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  • 1.
    Ahmed, Trifa M.
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ahmed, Baram
    Aziz, Bakhtyar K.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Native and oxygenated polycyclic aromatic hydrocarbons in ambient air particulate matter from the city of Sulaimaniyah in Iraq2015In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 116, p. 44-50Article in journal (Refereed)
    Abstract [en]

    The concentrations of 43 polycyclic aromatic hydrocarbons (PAHs) and 4 oxygenated PAHs (OPAHs) are reported for the first time in particulate matter (PM10) sampled in the air of the city of Sulaimaniyah in Iraq. The total PAH concentration at the different sampling sites varied between 9.3 and 114 ng/m(3). The corresponding values of the human carcinogen benzotalpyrene were between 0.3 and 6.9 ng/m(3), with most samples exceeding the EU annual target value of 1 ng/m(3). The highly carcinogenic dibenzopyrene isomers dibenzo[a,l]pyrene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene and dibenzo[a,h]pyrene constituted 0.1-0.4% of the total PAH concentration. However, when scaling for relative cancer potencies using toxic equivalency factors, a benzo[a]pyrene equivalent concentration of dibenzo[a,l]pyrene equal to that of benzo[a]pyrene was obtained, indicating that the contribution of dibenzo[a,l]pyrene to the carcinogenicity of the PAHs could be similar to that of benzo[a]pyrene. A high correlation between the determined concentrations of the dibenzopyrene isomers and benzo[a]pyrene was found, which supported the use of benzo[a]pyrene as an indicator for the carcinogenicity of PAHs in ambient air. The total concentrations of the four OPAHs, 9,10-anthraquinone, 4H-cyclopenta[def]phenanthren-4-one, benzanthrone, and 7,12-benz[a]anthraquinone, varied between 0.6 and 8.1 ng/m(3), with 9,10-anthraquinone being the most abundant OPAH in all of the samples.

  • 2.
    Andersson, August
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Sheesley, Rebecca J.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Krusa, Martin
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    (14)C-Based source assessment of soot aerosols in Stockholm and the Swedish EMEP-Aspvreten regional background site2011In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 45, no 1, p. 215-222Article in journal (Refereed)
    Abstract [en]

    Combustion-derived soot or black carbon (BC) in the atmosphere has a strong influence on both climate and human health. In order to propose effective mitigation strategies for BC emissions it is of importance to investigate geographical distributions and seasonal variations of BC emission sources. Here, a radiocarbon methodology is used to distinguish between fossil fuel and biomass burning sources of soot carbon (SC). SC is isolated for subsequent off-line (14)C quantification with the chemothermal oxidation method at 375 degrees C (CTO-375 method), which reflects a recalcitrant portion of the BC continuum known to minimize inadvertent inclusion of any non-pyrogenic organic matter. Monitored wind directions largely excluded impact from the Stockholm metropolitan region at the EMEP-Aspvreten rural station 70 km to the south-west. Nevertheless, the Stockholm city and the rural stations yielded similar relative source contributions with fraction biomass (f(biomass)) for fall and winter periods in the range of one-third to half. Large temporal variations in (14)C-based source apportionment was noted for both the 6 week fall and the 4 month winter observations. The f(biomass) appeared to be related to the SC concentration suggesting that periods of elevated BC levels may be caused by increased wood fuel combustion. These results for the largest metropolitan area in Scandinavia combine with other recent (14)C-based studies of combustion-derived aerosol fractions to suggest that biofuel combustion is contributing a large portion of the BC load to the northern European atmosphere.

  • 3.
    Andersson, Camilla
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bergström, Robert
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Population exposure and mortality due to regional background PM in Europe – longterm simulations of source-region and shipping contributions2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 22-23, p. 3614-3620Article in journal (Refereed)
    Abstract [en]

    This paper presents the contribution to population exposure (PE) of regional background fine primary (PPM2.5) and secondary inorganic (SIA) particulate matter and its impact on mortality in Europe during 1997–2003 calculated with a chemistry transport model. Contributions to concentrations and PE due to emissions from shipping, Western (WEU), Eastern (EEU), and Northern Europe are compared.

    WEU contributes about 40% to both PPM2.5 and SIA concentrations, whereas the EEU contribution to PPM2.5 is much higher (43% of total PPM2.5) than to SIA (29% of total SIA). The population weighted average concentration (PWC) of PPM2.5 is a factor of 2.3 higher than average (non-weighted) concentrations, whereas for SIA the PWC is only a factor 1.6 higher. This is due to PPM2.5 concentrations having larger gradients and being relatively high over densely populated areas, whereas SIA is formed outside populated areas. WEU emissions contribute relatively more than EEU to PWC and mortality due to both PPM2.5 and SIA in Europe.

    The number of premature deaths in Europe is estimated to 301 000 per year due to PPM2.5 exposure and 245 000 due to SIA, despite 3.3 times higher average SIA concentrations. This is due to population weighting and assumed (and uncertain) higher relative risk of mortality for PPM2.5 components (2.8 times higher RR for PPM2.5). This study indicates that it might be more efficient, for the health of the European population, to decrease primary PM emissions (especially in WEU) than to decrease precursors of SIA, but more knowledge on the toxicity of different PM constituents is needed before firm conclusions can be drawn.

  • 4.
    Avagyan, Rozanna
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Nyström, Robin
    Lindgren, Robert
    Boman, Christoffer
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Particulate hydroxy-PAH emissions from a residential wood log stove using different fuels and burning conditions2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 140, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Hydroxylated polycyclic aromatic hydrocarbons are oxidation products of polycyclic aromatic hydrocarbons, but have not been studied as extensively as polycyclic aromatic hydrocarbons. Several studies have however shown that hydroxylated polycyclic aromatic hydrocarbons have toxic and carcinogenic properties. They have been detected in air samples in semi urban areas and combustion is assumed to be the primary source of those compounds. To better understand the formation and occurrence of particulate hydroxylated polycyclic aromatic hydrocarbons from residential wood log stove combustion, 9 hydroxylated polycyclic aromatic hydrocarbons and 2 hydroxy biphenyls were quantified in particles generated from four different types of wood logs (birch, spruce, pine, aspen) and two different combustion conditions (nominal and high burn rate). A previously developed method utilizing liquid chromatography photo ionization tandem mass spectrometry and pressurized liquid extraction was used. Polycyclic aromatic hydrocarbons were analyzed along with hydroxylated polycyclic aromatic hydrocarbons. The hydroxylated polycyclic aromatic hydrocarbon emissions varied significantly across different wood types and burning conditions; the highest emissions for nominal burn rate were from spruce and for high burn rate from pine burning. Emissions from nominal burn rate corresponded on average to 15% of the emissions from high burn rate, with average emissions of 218 mu g/MJ(fuel) and 32.5 mu g/MJ(fuel) for high burn rate and nominal burn rate, respectively. Emissions of the measured hydroxylated polycyclic aromatic hydrocarbons corresponded on average to 28% of polycyclic aromatic hydrocarbons emissions. This study shows that wood combustion is a large emission source of hydroxylated polycyclic aromatic hydrocarbons and that not only combustion conditions, but also wood type influences the emissions of hydroxylated polycyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons. There are few studies that have determined hydroxylated polycyclic aromatic hydrocarbons in emissions from wood combustion, and it is therefore necessary to further investigate the formation, occurrence and distribution of these compounds as they are present in significant amounts in wood smoke particles.

  • 5.
    Baduel, Christine
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Nozière, Barbara
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Jaffrezo, Jean-Luc
    Summer/winter variability of the surfactants in aerosols from Grenoble, France2012In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 47, p. 413-420Article in journal (Refereed)
    Abstract [en]

    Many atmospheric aerosols seem to contain strong organic surfactants likely to enhance their cloud-forming properties. Yet, few techniques allow for the identification and characterization of these compounds. Recently, we introduced a double extraction method to isolate the surfactant fraction of atmospheric aerosol samples, and evidenced their very low surface tension (<= 30 mN m(-1)). In this work, this analytical procedure was further optimized. In addition to an optimized extraction and a reduction of the analytical time, the improved method led to a high reproducibility in the surface tension curves obtained (shapes and minimal values), illustrated by the low uncertainties on the values, +/- 10% or less. The improved method was applied to PM10 aerosols from the urban area of Grenoble, France collected from June 2009 to January 2010. Significant variability was observed between the samples. The minimum surface tension obtained from the summer samples was systematically lower (30 mN m(-1)) than that of the winter samples (35-45 mN m(-1)). Sharp transitions in the curves together with the very low surface tensions suggested that the dominating surfactants in the summer samples were biosurfactants, which would be consistent with the high biogenic activity in that season. One group of samples from the winter also displayed sharp transitions, which, together with the slightly higher surface tension, suggested the presence of weaker, possibly man-made, surfactants. A second group of curves from the winter did not display any clear transition but were similar to those of macromolecular surfactants such as polysaccharides or humic substances from wood burning. These surfactants are thus likely to originate from wood burning, the dominating source for aerosols in Grenoble in winter. These observations thus confirm the presence of surfactants from combustion processes in urban aerosols reported by other groups and illustrates the ability of our method to distinguish between different types of surfactants in atmospheric samples.

  • 6.
    Bergvall, Christoffer
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of highly carcinogenic dibenzopyrene isomers in particulate emissions from two diesel- and two gasoline-fuelled light-duty vehicles2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 25, p. 3883-3890Article in journal (Refereed)
    Abstract [en]

    Emission factors of particulate-bound Polycyclic Aromatic Hydrocarbons (PAHs) including benzo(a)pyrene and, for the first time, the highly carcinogenic dibenzo(a,l)pyrene, dibenzo(a,e)pyrene, dibenzo(a,i)pyrene and dibenzo(a,h)pyrene have been determined in exhausts from two diesel- (DFVs) and two gasoline-fuelled light-duty vehicles (GFVs) operated in the Urban (AU), Rural Road (AR) and Motorway (AM) transient ARTEMIS driving cycles. The obtained results showed the DFVs to emit higher amounts of PAHs than the GFVs per km driving distance at low average speed in the AU driving cycle, while the GFVs emitted higher amounts of PAHs than the DFVs per km driving distance at higher average speeds in the AR and AM driving cycles. Furthermore, the study showed an increase in PAH emissions per km driving distance with increasing average speed for the GFVs with the opposite trend found for the DFVs. The GFVs generated particulate matter with higher PAH content than the DFVs in all three driving cycles tested with the highest concentrations obtained in the AR driving cycle. Dibenzo(a,l)pyrene was found to be a major contributor to the potential carcinogenicity accounting for 58–67% and 25–31% of the sum added potential carcinogenicity of the measured PAHs in the emitted particulate matter from the DFVs and GFVs, respectively. Corresponding values for benzo(a)pyrene were 16–25% and 11–40% for the DFVs and GFVs, respectively. The DFVs displayed higher sum added potential carcinogenicity of the measured PAHs than the GFVs in the AU driving cycle with the opposite trend found in the AR and AM driving cycles. The findings of this study show the importance of including the dibenzopyrenes in vehicle exhaust chemical characterizations to avoid potential underestimation of the carcinogenic activity of the emissions. The lower emissions and the lower sum added potential carcinogenicity of the measured PAHs found in this study for the GFVs compared to the DFVs in the AU driving cycle indicate the GFVs to be preferred in dense urban areas with traffic moving at low average speeds with multiple start and stops. However, the obtained results suggest the opposite to be true at higher average speeds with driving at rural roads and motorways. Further studies are, however, needed to establish if the observed differences between GFVs and DFVs are generally valid as well as to study the effects on variations in vehicle/engine type, ambient temperature, fuel and driving conditions on the emission factors.

  • 7. Budhavant, K. B.
    et al.
    Rao, P. S. P.
    Safai, P. D.
    Granat, L.
    Rodhe, Henning
    Stockholm University, Faculty of Science, Department of Meteorology .
    Chemical composition of the inorganic fraction of cloud-water at a high altitude site in West India2014In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 88, p. 59-65Article in journal (Refereed)
    Abstract [en]

    Data from a ground-based cloud-water collection system intercepting water from clouds at a mountain field station, Sinhagad near Pune in India are presented. This study was part of an Indo-Swedish Collaboration Project on Atmospheric Brown Cloud-Asia (ABC-A). Cloud-water and rainwater (wet-only) samples were collected during June 2007-Dec. 2010. Concentrations of major anions and cations were determined. Ion concentrations were generally higher (NO3-, about 8 times; SO42- and K+, 5 times; NH4+ times and Cl-, Na+, Ca2+, Mg2+ 3 times) in cloud-water samples than in rainwater samples collected during the same days. The average pH of cloud-water samples was 6.0 with about 20% of the values below 5.6 and only 4% less than 5.0. Despite high concentrations of SO42- and NO3- the cloud water samples were on average not more acidic than rainwater samples. This is different from most of the other studies of cloud-water composition which have noted a substantially higher acidity (i.e. lower pH) in cloud-water than in rainwater. The slightly alkaline (pH > 5.6) nature of the cloud-water samples is mainly due to the presence of soil derived calcium carbonate in quantities more than enough to neutralize the acids or their precursors. A separation of the cloud-water data into trajectory groups showed that samples in air-masses having spent the last few days over the Indian sub-continent were in general more acidic (due to anthropogenic emissions) than those collected during days with air-masses of marine origin. A high correlation mutually between Ca2+, Na+, NO3- and SO42- makes it difficult to estimate the contribution to SO42- from different sources. Anthropogenic SO2- emissions and soil dust may both give important contributions.

  • 8. Budhavant, K. B.
    et al.
    Rao, P. S. P.
    Safai, P. D.
    Leck, Caroline
    Stockholm University, Faculty of Science, Department of Meteorology .
    Rodhe, Henning
    Stockholm University, Faculty of Science, Department of Meteorology .
    Black carbon in cloud-water and rain water during monsoon season at a high altitude station in India2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 129, p. 256-264Article in journal (Refereed)
    Abstract [en]

    We present results of measurements of black carbon (BC) from ground-based wet-only rainwater (RW) and cloud-water (CW) sampling at a mountain field station, Sinhagad, situated in south western India during the period from June 2008 to October 2010. The amount of BC in the sample was determined by photometry at a wavelength of 528 nm after a procedure including the filtration through a 0.4 mu m polycarbonate membrane filter. Water soluble concentrations of major anions in RW and CW were also determined. The average concentration of BC in RW (16 mu mol dm(-3)) is higher by at least a factor 2 than that found in similar studies reported from other parts of the world. On the other hand, the average concentration of BC in CW (47 mu mol dm(-3)) is lower by about a factor of 2 than that found at other sites. The ratio between the average concentrations in CW and RW varies from 2 (K+) to 7 (SO42-). The ratio for BC was about 3. No significant difference was observed for pH. Analysis of air mass back trajectories and of correlations between the various components indicates that long range transport of pollutants and dust from East Africa and Southern part of the Arabian peninsula might contribute to the high concentrations of BC and some of the ionic constituents at Sinhagad during the monsoon season.

  • 9. Cavalli, F.
    et al.
    Alastuey, A.
    Areskoug, Hans
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ceburnis, D.
    Cech, J.
    Genberg, J.
    Harrison, R. M.
    Jaffrezo, J. L.
    Kiss, G.
    Laj, P.
    Mihalopoulos, N.
    Perez, N.
    Quincey, P.
    Schwarz, J.
    Sellegri, K.
    Spindler, G.
    Swietlicki, E.
    Theodosi, C.
    Yttri, K. E.
    Aas, W.
    Putaud, J. P.
    A European aerosol phenomenology-4: Harmonized concentrations of carbonaceous aerosol at 10 regional background sites across Europe2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 144, p. 133-145Article in journal (Refereed)
    Abstract [en]

    Although particulate organic and elemental carbon (OC and EC) are important constituents of the suspended atmospheric particulate matter (PM), measurements of OC and EC are much less common and More uncertain than measurements of e.g. the ionic components of PM. In the framework of atmospheric research infrastructures supported by the European Union, actions have been undertaken to determine and mitigate sampling artefacts, and assess the comparability of OC and EC data obtained in a network of 10 atmospheric observatories across Europe. Positive sampling artefacts (from 0:4 to 2.8 mu g C/m(3)) and analytical discrepancies (between -50% and +40% for the EC/TC ratio) have been taken into account to generate a robust data set, from which we established the phenomenology of carbonaceous aerosols at regional background sites in Europe. Across the network, TC and EC annual average concentrations range from 0.4 to 9 mu g C/m(3), and from 0.1 to 2 mu g C/m(3), respectively. TC/PM10 annual mean ratios range from 0.11 at a Mediterranean site to 0.34 at the most polluted continental site, and TC/PM2.5 ratios are slightly greater at all sites (0.15-0.42). EC/TC annual mean ratios range from 0.10 to 0.22, and do not depend much on PM concentration levels, especially in winter. Seasonal variations in PM and TC concentrations, and in TC/PM and EC/TC ratios, differ across the network, which can be explained by seasonal changes in PM source contributions at some sites.

  • 10. Cho, Chaeyoon
    et al.
    Kim, Sang-Woo
    Lee, Meehye
    Lim, Saehee
    Fang, Wenzheng
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Park, Rokjin J.
    Sheridan, Patrick J.
    Observation-based estimates of the mass absorption cross-section of black and brown carbon and their contribution to aerosol light absorption in East Asia2019In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 212, p. 65-74Article in journal (Refereed)
    Abstract [en]

    In this study, we estimated the contribution of black carbon (BC) and brown carbon (BrC) to aerosol light absorption from surface in-situ and aerosol robotic network (AERONET) columnar observations. The mass absorption cross-section (MAC) of BC (MAC(BC)) was estimated to be 6.4 +/- 1.5 m(2) g(-1) at 565 mn from in-situ aerosol measurements at Gosan Climate Observatory (GCO), Korea, in January 2014, which was lower than those observed in polluted urban areas. A BrC MAC of 0.62 +/- 0.06 m(2) g(-1) (565 mn) in our estimate is approximately ten times lower than MACK at 565 nm. The contribution of BC and BrC to the carbonaceous aerosol absorption coefficient at 565 nm from the in-situ measurements was estimated at 88.1 +/- 7.4% and 11.9 +/- 7.4%, respectively at GCO. Similarly, the contribution of BC and BrC to the absorption aerosol optical depth (AAOD) for carbonaceous aerosol (CA), constrained by AERONET observations at 14 sites over East Asia by using different spectral dependences of the absorption (i.e., absorption Angstrom exponent) of BC and BrC, was 84.9 +/- 2.8% and 15.1 +/- 2.8% at 565 nm, respectively. The contribution of BC to CA AAOD was greater in urban sites than in the background areas, whereas the contribution of BrC to CA AAOD was higher in background sites. The overall contribution of BC to CA AAOD decreased by 73%-87% at 365 nm, and increased to 93%-97% at 860 nm. The contribution of BrC to CA AAOD decreased significantly with increasing wavelength from approximately 17% at 365 nm to 4% at 860 nm.

  • 11. Cirino, Glauber
    et al.
    Brito, Joel
    Barbosa, Henrique M. J.
    Rizzo, Luciana V.
    Tunved, Peter
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    de Sá, Suzane S.
    Jimenez, Jose L.
    Palm, Brett B.
    Carbone, Samara
    Lavric, Jost V.
    Souza, Rodrigo A. F.
    Wolff, Stefan
    Walter, David
    Tota, Júlio
    Oliveira, Maria B. L.
    Martin, Scot T.
    Artaxo, Paulo
    Observations of Manaus urban plume evolution and interaction with biogenic emissions in GoAmazon 2014/52018In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 191, p. 513-524Article in journal (Refereed)
    Abstract [en]

    As part of the Observations and Modeling of the Green Ocean Amazon (GoAmazon 2014/5) Experiment, detailed aerosol and trace gas measurements were conducted near Manaus, a metropolis located in the central Amazon Basin. Measurements of aerosol particles and trace gases were done downwind Manaus at the sites T2 (Tiwa Hotel) and T3 (Manacapuru), at a distance of 8 and 70 km from Manaus, respectively. Based on in-plume measurements closer to Manaus (site T2), the chemical signatures of city emissions were used to improve the interpretation of pollutant levels at the T3 site. We derived chemical and physical properties for the city's atmospheric emission ensemble, taking into account only air masses impacted by the Manaus plume at both sites, during the wet and dry season Intensive Operating Periods (IOPs). At T2, average concentrations of aerosol number (CN), CO and SO2 were 5500 cm(-3) (between 10 and 490 nm), 145 ppb and 0.60 ppb, respectively, with a typical ratio ACN/ACO of 60-130 particles cm(-3) ppb(-1). The aerosol scattering (at RH < 60%) and absorption at 637 nm at T2 ranged from 10 to 50 M m(-1) and 5-10 M m(-1), respectively, leading to a mean single scattering albedo (SSA) of 0.70. In addition to identifying periods dominated by Manaus emissions at both T2 and T3, the plume transport between the two sampling sites was studied using back trajectory calculations. Results show that the presence of the Manaus plume at site T3 was important mainly during the daytime and at the end of the afternoons. During time periods directly impacted by Manaus emissions, an average aerosol number concentration of 3200 cm(-3) was measured at T3. Analysis of plume evolution between T2 and T3 indicates a transport time of 4-5 h. Changes of submicron organic and sulfate aerosols ratios relative to CO (Delta OA/Delta CO and Delta SO4/Delta CO, respectively) indicate significant production of secondary organic aerosol (SOA), corresponding to a 40% mass increase in OA and a 30% in SO4 mass concentration. Similarly, during air mass arrival at T3 the SSA increased to 0.83 from 0.70 at T2, mainly associated with an increase in organic aerosol concentration. Aerosol particle size distributions show a strong decrease in the Aitken nuclei mode (10-100 nm) during the transport from T2 to T3, in particular above 30 nm, as a result of efficient coagulation processes into larger particles. A decrease of 30% in the particle number concentration and an increase of about 50 nm in geometric mean diameter were observed from T2 to T3 sites. The study of the evolution of aerosol properties downwind of the city of Manaus improves our understanding of how coupling of anthropogenic and biogenic sources may be impacting the sensitive Amazonian atmosphere.

  • 12. Denby, B. R.
    et al.
    Ketzel, M.
    Ellermann, T.
    Stojiljkovic, A.
    Kupiainen, K.
    Niemi, J. V.
    Norman, M.
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Environment and Health Protection Administration of the City of Stockholm, Sweden.
    Gustafsson, M.
    Blomqvist, G.
    Janhall, S.
    Sundvor, I.
    Road salt emissions: A comparison of measurements and modelling using the NORTRIP road dust emission model2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 141, p. 508-522Article in journal (Refereed)
    Abstract [en]

    De-icing of road surfaces is necessary in many countries during winter to improve vehicle traction. Large amounts of salt, most often sodium chloride, are applied every year. Most of this salt is removed through drainage or traffic spray processes but a certain amount may be suspended, after drying of the road surface, into the air and will contribute to the concentration of particulate matter. Though some measurements of salt concentrations are available near roads, the link between road maintenance salting activities and observed concentrations of salt in ambient air is yet to be quantified. In this study the NORTRIP road dust emission model, which estimates the emissions of both dust and salt from the road surface, is applied at five sites in four Nordic countries for ten separate winter periods where daily mean ambient air measurements of salt concentrations are available. The model is capable of reproducing many of the salt emission episodes, both in time and intensity, but also fails on other occasions. The observed mean concentration of salt in PM10, over all ten datasets, is 4.2 mu g/m(3) and the modelled mean is 2.8 mu g/m(3), giving a fractional bias of -0.38. The RMSE of the mean concentrations, over all 10 datasets, is 2.9 mu g/m(3) with an average R-2 of 0.28. The mean concentration of salt is similar to the mean exhaust contribution during the winter periods of 2.6 mu g/m(3). The contribution of salt to the kerbside winter mean PM10 concentration is estimated to increase by 4.1 +/- 3.4 mu g/m(3) for every kg/m(2) of salt applied on the road surface during the winter season. Additional sensitivity studies showed that the accurate logging of salt applications is a prerequisite for predicting salt emissions, as well as good quality data on precipitation. It also highlights the need for more simultaneous measurements of salt loading together with ambient air concentrations to help improve model parameterisations of salt and moisture removal processes.

  • 13. Denby, B. R.
    et al.
    Sundvor, I.
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Pirjola, L.
    Ketzel, M.
    Norman, M.
    Kupiainen, K.
    Gustafsson, M.
    Blomqvist, G.
    Kauhaniemi, M.
    Omstedt, G.
    A coupled road dust and surface moisture model to predict non-exhaust road traffic induced particle emissions (NORTRIP). Part 2: Surface moisture and salt impact modelling2013In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 81, p. 485-503Article in journal (Refereed)
    Abstract [en]

    Non-exhaust traffic induced emissions are a major source of airborne particulate matter in most European countries. This is particularly important in Nordic and Alpine countries where winter time road traction maintenance occurs, e.g. salting and sanding, and where studded tyres are used. Though the total mass generated by wear sources is a key factor in non-exhaust emissions, these emissions are also strongly controlled by surface moisture conditions. In this paper, Part 2, the road surface moisture sub-model of a coupled road dust and surface moisture model (NORTRIP) is described. We present a description of the road surface moisture part of the model and apply the coupled model to seven sites in Stockholm, Oslo, Helsinki and Copenhagen over 18 separate periods, ranging from 3.5 to 24 months. At two sites surface moisture measurements are available and the moisture sub-model is compared directly to these observations. The model predicts the frequency of wet roads well at both sites, with an average fractional bias of −2.6%. The model is found to correctly predict the hourly surface state, wet or dry, 85% of the time. From the 18 periods modelled using the coupled model an average absolute fractional bias of 15% for PM10 concentrations was found. Similarly the model predicts the 90'th daily mean percentiles of PM10 with an average absolute bias of 19% and an average correlation (R2) of 0.49. When surface moisture is not included in the modelling then this average correlation is reduced to 0.16, demonstrating the importance of the surface moisture conditions. Tests have been carried out to assess the sensitivity of the model to model parameters and input data. The model provides a useful tool for air quality management and for improving our understanding of non-exhaust traffic emissions.

  • 14. Denby, B. R.
    et al.
    Sundvor, I.
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Pirjola, L.
    Ketzel, M.
    Norman, M.
    Kupiainen, K.
    Gustafsson, M.
    Blomqvist, G.
    Omstedt, G.
    A coupled road dust and surface moisture model to predict non-exhaust road traffic induced particle emissions (NORTRIP). Part 1: Road dust loading and suspension modelling2013In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 77, p. 283-300Article in journal (Refereed)
    Abstract [en]

    Non-exhaust traffic induced emissions are a major source of particle mass in most European countries. This is particularly important in Nordic and Alpine countries where winter time road traction maintenance occurs, e.g. salting and sanding, and where studded tyres are used. In this paper, Part 1, the road dust sub-model of a coupled road dust and surface moisture model (NORTRIP) is described. The model provides a generalised process based formulation of the non-exhaust emissions, with emphasis on the contribution of road wear, suspension, surface dust loading and the effect of road surface moisture (retention of wear particles and suspended emissions). The model is intended for use as a tool for air quality managers to help study the impact of mitigation measures and policies. We present a description of the road dust sub-model and apply the model to two sites in Stockholm and Copenhagen where seven years of data with surface moisture measurements are available. For the site in Stockholm, where studded tyres are in use, the model predicts the PM10 concentrations very well with correlations (R-2) in the range of R-2 = 0.76-0.91 for daily mean PM10. The model also reproduces well the impact of a reduction in studded tyres at this site. For the site in Copenhagen the correlation is lower, in the range 0.44-0.51. The addition of salt is described in the model and at both sites this leads to improved correlations due to additional salt emissions. For future use of the model a number of model parameters, e.g. wear factors and suspension rates, still need to be refined. The effect of sanding on PM10 emissions is also presented but more information will be required before this can be confidently applied for management applications.

  • 15.
    Eneroth, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Holmen, Kim
    Berg, Torunn
    Schmidbauer, Norbert
    Solberg, Sverre
    Springtime depletion of tropospheric ozone, gaseous elemental mercury and non-methane hydrocarbons in the European Arctic, and its relation to atmospheric transport2007In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 41, no 38, p. 8511-8526Article in journal (Refereed)
    Abstract [en]

    Using a trajectory climatology for the period 1992-2001 we have examined how seasonal changes in transport cause changes in the concentrations of tropospheric ozone (O-3), gaseous elemental mercury (GEM) and non-methane hydrocarbons (NMHCs) observed at the Mt. Zeppelin station, Ny-angstrom lesund (78.9 degrees N, 11.9 degrees E). During April-June O-3 depletion events were frequently observed in connection with air transport across the Arctic Basin. The O-3 loss was most pronounced in air masses advected close to the surface. This result supports the idea that the O-3 depletion reactions take place in the lowermost part of the atmosphere in the central Arctic Basin. A strong positive correlation between springtime O-3 depletion events and the oxidation of GEM to divalent mercury was found. During air mass advection from Siberia, the Barents Sea and the Norwegian Sea the strongest correlation was observed during April-May, whereas air masses originating from the Canadian Arctic and the central Arctic areas showed the highest O-3-GEM correlation in May-June. We suggest that this 1-month lag could either be due to the position of the marginal ice zone or temperature differences between the northwestern and northeastern air masses. In connection with springtime O-3 depletion events low concentrations of some NMHCs, especially ethane and ethyne, were observed, indicating that both bromine (ethyne oxidant) and chlorine radicals (ethane oxidant) are present in the Arctic atmosphere during spring. In winter, negative correlations between O-3 and NMHCs were found in connection with air transport from Europe and Siberia, which we interpret as O-3 destruction taking place in industrially contaminated plumes.

  • 16. Fowler, D.
    et al.
    Pilegaard, K.
    Sutton, M. A.
    Ambus, P.
    Raivonen, M.
    Duyzer, J.
    Simpson, D.
    Fagerli, H.
    Fuzzi, S.
    Schjoerring, J. K.
    Granier, C.
    Neftel, A.
    Isaksen, I. S. A.
    Laj, P.
    Maione, M.
    Monks, P. S.
    Burkhardt, J.
    Daemmgen, U.
    Neirynck, J.
    Personne, E.
    Wichink-Kruit, R.
    Butterbach-Bahl, K.
    Flechard, C.
    Tuovinen, J. P.
    Coyle, M.
    Gerosa, G.
    Loubet, B.
    Altimir, N.
    Gruenhage, L.
    Ammann, C.
    Cieslik, S.
    Paoletti, E.
    Mikkelsen, T. N.
    Ro-Poulsen, H.
    Cellier, P.
    Cape, J. N.
    Horvath, L.
    Loreto, F.
    Niinemets, Ue
    Palmer, P. I.
    Rinne, J.
    Misztal, P.
    Nemitz, E.
    Nilsson, Douglas
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Pryor, S.
    Gallagher, M. W.
    Vesala, T.
    Skiba, U.
    Brueggemann, N.
    Zechmeister-Boltenstern, S.
    Williams, J.
    O'Dowd, C.
    Facchini, M. C.
    de Leeuw, G.
    Flossman, A.
    Chaumerliac, N.
    Erisman, J. W.
    Atmospheric composition change: Ecosystems-Atmosphere interactions2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 33, p. 5193-5267Article, review/survey (Refereed)
    Abstract [en]

    Ecosystems and the atmosphere: This review describes the state of understanding the processes involved in the exchange of trace gases and aerosols between the earth's surface and the atmosphere. The gases covered include NO, NO2, HONO, HNO3, NH3, SO2, DMS, Biogenic VOC, O-3, CH4, N2O and particles in the size range 1 nm-10 mu m including organic and inorganic chemical species. The main focus of the review is on the exchange between terrestrial ecosystems, both managed and natural and the atmosphere, although some new developments in ocean-atmosphere exchange are included. The material presented is biased towards the last decade, but includes earlier work, where more recent developments are limited or absent. New methodologies and instrumentation have enabled, if not driven technical advances in measurement. These developments have advanced the process understanding and upscaling of fluxes, especially for particles, VOC and NH3. Examples of these applications include mass spectrometric methods, such as Aerosol Mass Spectrometry (AMS) adapted for field measurement of atmosphere-surface fluxes using micrometeorological methods for chemically resolved aerosols. Also briefly described are some advances in theory and techniques in micrometeorology. For some of the compounds there have been paradigm shifts in approach and application of both techniques and assessment. These include flux measurements over marine surfaces and urban areas using micrometeorological methods and the up-scaling of flux measurements using aircraft and satellite remote sensing. The application of a flux-based approach in assessment of O-3 effects on vegetation at regional scales is an important policy linked development secured through improved quantification of fluxes. The coupling of monitoring, modelling and intensive flux measurement at a continental scale within the NitroEurope network represents a quantum development in the application of research teams to address the underpinning science of reactive nitrogen in the cycling between ecosystems and the atmosphere in Europe. Some important developments of the science have been applied to assist in addressing policy questions, which have been the main driver of the research agenda, while other developments in understanding have not been applied to their wider field especially in chemistry-transport models through deficiencies in obtaining appropriate data to enable application or inertia within the modelling community. The paper identifies applications, gaps and research questions that have remained intractable at least since 2000 within the specialized sections of the paper, and where possible these have been focussed on research questions for the coming decade. 

  • 17.
    Gidhagen, Lars
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Langner, Joakim
    Olivares, Gustavo
    Simulation of NOx and ultrafine particles in a street canyon in Stockholm, Sweden2004In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 38, no 14Article in journal (Refereed)
    Abstract [en]

    A computational fluid dynamic (CFD) model has been used to assess the concentrations of NOx and particle number in a street canyon in Stockholm with a high traffic volume. Comparisons of a simulated 11-week long time series of NOx with measurements (both sides of the street, urban background excluded) show good agreement, especially if emissions are distributed to be three times higher along the side of the street where the traffic is uphill, as compared to the downhill side. The simulation of number concentrations of inert particles indicates a similar asymmetry in emissions.

    A month-long measurement of particle size distribution (7–450 nm) at street level indicates that the ratio of nucleation size mode particle (7–20 nm) to total particle number (7–450 nm) is decreasing for increased particle surface area. Given the strong dominance of the locally generated particles over the urban background, this is interpreted as a local change in the size distribution. The results of a monodisperse aerosol dynamic model, coupled to the CFD model that simulates also the turbulence generated by vehicle movements, show that coagulation and deposition may reduce total particle inside the canyon with approximately 30% during low wind speeds. Most of the removal occurs shortly after emission, before the particles reach the leeward curb-side. Losses between the leeward curb-side and other locations in the street, e.g. roof levels, is estimated to be smaller, less than 10%. Coagulation is the dominating removal process under low wind speed conditions and deposition for higher wind speeds, the summed removal being smaller for high wind velocities. Deposition is enhanced over the road surface due to the velocities generated by vehicle movements. Although coagulation and deposition removal is most effective on the smallest ultrafine particles, this effect is not sufficient to explain the observed change in size distribution. It is suggested that also the formation of particles in the exhaust plumes is influenced by a larger particle surface area in the ambient air.

  • 18.
    Glantz, Paul
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Kokhanovsky, A.
    von Hoyningen-Huene, W.
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Estimating PM2.5 over southern Sweden using space-borne optical measurements2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 36, p. 5838-5846Article in journal (Other academic)
    Abstract [en]

    in the present study Bremen aerosol retrieval (BAER) columnar aerosol optical thickness (ACT) data, according to moderate resolution imaging spectroradiometer (MODIS) and medium resolution imaging sensor (MERIS) level 1 calibrated satellite data, have been compared with ACT data obtained with the MODIS and MERIS retrieval algorithms (NASA and ESA, respectively) and by AErosol Robotic NETwork (AERONET). Relatively good agreement is found between these different instruments and algorithms. The R-2 and relative RMSD were 0.86 and 31% for MODIS when comparing with AERONET and 0.92 and 21% for MERIS. The aerosols investigated were influenced by low relative humidity. During this period, a relatively large range of aerosol loadings were detected; from continental background aerosol to particles emitted from agricultural fires. In this study, empirical relationships between BAER columnar AOT and ground-measured PM2.5 have been estimated. Linear relationships, with R-2 values of 0.58 and 0.59, were obtained according to MERIS and MODIS data, respectively. The slopes of the regression of ACT versus PM2.5 are lower than previous studies, but this could easily be explained by considering the effect of hygroscopic growth. The present AOT-PM2.5 relationship has been applied on MERIS full resolution data over the urban area of Stockholm and the results have been compared with particle mass concentrations from dispersion model calculations. it seems that the satellite data with the 300 m resolution can resolve the expected increased concentrations due to emissions along the main highways close to the city. Significant uncertainties in the spatial distribution of PM2.5 across land/ocean boundaries were particularly evident when analyzing the high resolution satellite data.

  • 19. Hoffmann, Anne
    et al.
    Osterloh, Lukas
    Stone, Robert
    Lampert, Astrid
    Ritter, Christoph
    Stock, Maria
    Tunved, Peter
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hennig, Tabea
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Boeckmann, Christine
    Li, Shao-Meng
    Eleftheriadis, Kostas
    Maturilli, Marion
    Orgis, Thomas
    Herber, Andreas
    Neuber, Roland
    Dethloff, Klaus
    Remote sensing and in situ measurements of tropospheric aerosol, a pamarcmip case study2012In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 52, p. 56-66Article in journal (Refereed)
    Abstract [en]

    In this work, a closure experiment for tropospheric aerosol is presented. Aerosol size distributions and single scattering albedo from remote sensing data are compared to those measured in-situ. An aerosol pollution event on 4 April 2009 was observed by ground based and airborne lidar and photometer in and around Ny-Alesund, Spitsbergen, as well as by DMPS, nephelometer and particle soot absorption photometer at the nearby Zeppelin Mountain Research Station. The presented measurements were conducted in an area of 40 x 20 km around Ny-Alesund as part of the 2009 Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project (PAMARCMiP). Aerosol mainly in the accumulation mode was found in the lower troposphere, however, enhanced backscattering was observed up to the tropopause altitude. A comparison of meteorological data available at different locations reveals a stable multi-layer-structure of the lower troposphere. It is followed by the retrieval of optical and microphysical aerosol parameters. Extinction values have been derived using two different methods, and it was found that extinction (especially in the UV) derived from Raman lidar data significantly surpasses the extinction derived from photometer AOD profiles. Airborne lidar data shows volume depolarization values to be less than 2.5% between 500 m and 2.5 km altitude, hence, particles in this range can be assumed to be of spherical shape. In-situ particle number concentrations measured at the Zeppelin Mountain Research Station at 474 m altitude peak at about 0.18 mu m diameter, which was also found for the microphysical inversion calculations performed at 850 m and 1500 m altitude. Number concentrations depend on the assumed extinction values, and slightly decrease with altitude as well as the effective particle diameter. A low imaginary part in the derived refractive index suggests weakly absorbing aerosols, which is confirmed by low black carbon concentrations, measured at the Zeppelin Mountain as well as on board the Polar 5 aircraft.

  • 20. Hung, Hayley
    et al.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Guardans, Ramon
    Scheringer, Martin
    Barra, Ricardo
    Harner, Tom
    Zhang, Gan
    Toward the next generation of air quality monitoring: Persistent organic pollutants2013In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 80, p. 591-598Article in journal (Refereed)
    Abstract [en]

    Persistent Organic Pollutants (POPs) are global pollutants that can migrate over long distances and bioaccumulate through food webs, posing health risks to wildlife and humans. Multilateral environmental agreements, such as the Stockholm Convention on POPs, were enacted to identify POPs and establish the conditions to control their release, production and use. A Global Monitoring Plan was initiated under the Stockholm Convention calling for POP monitoring in air as a core medium; however long temporal trends (>10 years) of atmospheric POPs are only available at a few selected sites. Spatial coverage of air monitoring for POPs has recently significantly improved with the introduction and advancement of passive air samplers. Here, we review the status of air monitoring and modeling activities and note major uncertainties in data comparability, deficiencies of air monitoring and modeling in urban and alpine areas, and lack of emission inventories for most POPs. A vision for an internationally-integrated strategic monitoring plan is proposed which could provide consistent and comparable monitoring data for POPs supported and supplemented by global and regional transport models. Key recommendations include developing expertise in all aspects of air monitoring to ensure data comparability and consistency; partnering with existing air quality and meteorological networks to leverage synergies; facilitating data sharing with international data archives; and expanding spatial coverage with passive air samplers. Enhancing research on the stability of particle-bound chemicals is needed to assess exposure and deposition in urban areas, and to elucidate long-range transport. Conducting targeted measurement campaigns in specific source areas would enhance regional models which can be extrapolated to similar regions to estimate emissions. Ultimately, reverse-modeling combined with air measurements can be used to derive “emission” as an indicator to assess environmental performance with respect to POPs on the country, region, or global level.

  • 21.
    Jahnke, Annika
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Barber, J.L.
    Jones, K.C.
    Temme, C.
    Quantitative trace analysis of polyfluorinated alkyl substances (PFAS) in ambient air samples from Mace Head (Ireland): A method intercomparison2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 4, p. 844-850Article in journal (Refereed)
    Abstract [en]

    A method intercomparison study of analytical methods for the determination of neutral, volatile polyfluorinated alkyl substances (PFAS) was carried out in March, 2006. Environmental air samples were collected in triplicate at the European background site Mace Head on the west coast of Ireland, a site dominated by 'clean' westerly winds coming across the Atlantic. Extraction and analysis were performed at two laboratories active in PFAS research using their in-house methods. Airborne polyfluorinated telomer alcohols (FTOHs), fluo ooctane sulfonamides and sulfonamidoethanols (FOSAs/FOSEs) as well as additional polyfluorinated compounds were investigated. Different native and isotope-labelled internal standards (IS) were applied at various Steps in the analytical procedure to evaluate the different quantification strategies. Field blanks revealed no major blank problems. European background concentrations observed at Mace Head were found to be in a similar range to Arctic data reported in the literature. Due to trace-levels at the remote site, only FTCH data sets were complete and could therefore be compared between the laboratories. Additionally, FOSEs Could Partly be included. Data comparison revealed that despite the challenges inherent in analysis of airborne PFAS and the low concentrations, all methods applied in this Study obtained similar results. However, application of isotope-labelled IS early in the analytical procedure leads to more precise results and is therefore recommended.

  • 22.
    Johansson, Christer
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Burman, L.
    Forsberg, B.
    The effects of congestions tax on air quality and health.2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 31, p. 4843-4854Article in journal (Refereed)
    Abstract [en]

    The “Stockholm Trial” involved a road pricing system to improve the air quality and reduce traffic congestion. The test period of the trial was January 3–July 31, 2006. Vehicles travelling into and out of the charge cordon were charged for every passage during weekdays. The amount due varied during the day and was highest during rush hours (20 SEK = 2.2 EUR, maximum 60 SEK per day). Based on measured and modelled changes in road traffic it was estimated that this system resulted in a 15% reduction in total road use within the charged cordon. Total traffic emissions in this area of NOx and PM10 fell by 8.5% and 13%, respectively. Air quality dispersion modelling was applied to assess the effect of the emission reductions on ambient concentrations and population exposure. For the situations with and without the trial, meteorological conditions and other emissions than from road traffic were kept the same. The calculations show that, with a permanent congestion tax system like the Stockholm Trial, the annual average NOx concentrations would be lower by up to 12% along the most densely trafficked streets. PM10 concentrations would be up to 7% lower. The limit values for both PM10 and NO2 would still be exceeded along the most densely trafficked streets. The total population exposure of NOx in Greater Stockholm (35 × 35 km with 1.44 million people) is estimated to decrease with a rather modest 0.23 μg m−3. However, based on a long-term epidemiological study, that found an increased mortality risk of 8% per 10 μg m−3 NOx, it is estimated that 27 premature deaths would be avoided every year. According to life-table analysis this would correspond to 206 years of life gained over 10 years per 100 000 people following the trial if the effects on exposures would persist. The effect on mortality is attributed to road traffic emissions (likely vehicle exhaust particles); NOx is merely regarded as an indicator of traffic exposure. This is only the tip of the ice-berg since reductions are expected in both respiratory and cardiovascular morbidity. This study demonstrates the importance of not only assessing the effects on air quality limit values, but also to make quantitative estimates of health impacts, in order to justify actions to reduce air pollution.

  • 23.
    Johansson, Christer
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Norman, M.
    Burman, L.
    Road traffic emission factors for heavy metals2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 31, p. 4681-4688Article in journal (Refereed)
    Abstract [en]

    Quantifying the emissions and concentrations of heavy metals in urban air is a prerequisite for assessing their health effects. In this paper a combination of measurements and modelling is used to assess the contribution from road traffic emissions. Concentrations of particulate heavy metals in air were measured simultaneously during 1 year at a densely trafficked street and at an urban background site in Stockholm, Sweden. Annual mean concentrations of cadmium were 50 times lower than the EU directive and for nickel and arsenic concentrations were 10 and six times lower, respectively. More than a factor of two higher concentrations was in general observed at the street in comparison to roof levels indicating the strong influence from local road traffic emissions. The only compound with a significantly decreasing trend in the urban background was Pb with 9.1 ng m−3 in 1995/96 compared to 3.4 ng m−3 2003/04. This is likely due to decreased emissions from wear of brake linings and reduced emissions due to oil and coal combustion in central Europe.

    Total road traffic emission factors for heavy metals were estimated using parallel measurements of NOx concentrations and knowledge of NOx emission factors. In general, the emission factors for the street were higher than reported in road tunnel measurements. This could partly be due to different driving conditions, since especially for metals which are mainly emitted from brake wear, more stop and go driving in the street compared to in road tunnels is likely to increase emissions. Total emissions were compared with exhaust emissions, obtained from the COPERT model and brake wear emissions based on an earlier study in Stockholm. For Cu, Ni and Zn the sum of brake wear and exhaust emissions agreed very well with estimated total emission factors in this study. More than 90% of the road traffic emissions of Cu were due to brake wear. For Ni more than 80% is estimated to be due to exhaust emissions and for Zn around 40% of road traffic emissions are estimated to be due to exhaust emissions. Pb is also mainly due to exhaust emissions (90%); a fuel Pb content of only 0.5 mg L−1 would give similar emission factor as that based on the concentration increment at the street. This is the first study using simultaneous measurements of heavy metals at street and roof enabling calculations of emission factors using a tracer technique.

  • 24.
    Kierkegaard, Amelie
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    McLachlan, Michael S.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Determination of linear and cyclic volatile methylsiloxanes in air at a regional background site in Sweden2013In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 80, p. 322-329Article in journal (Refereed)
    Abstract [en]

    A number of volatile methylsiloxanes have been identified as environmental contaminants and several are currently the subject of detailed risk assessments due to concerns that they may be persistent, bioaccumulative and toxic in the environment. Once emitted these chemicals reside primarily in the atmosphere. Consequently, knowledge of their concentrations in air is essential to understanding their fate in the environment and any potential adverse impacts. We developed a method to analyse 4 cyclic volatile methylsiloxanes (D3, D4, D5 and D6) and 4 linear volatile methylsiloxanes (L3, L4, L5 and L6) in air at regional background levels. The method showed good repeatability (median difference between sample pairs of 2-8%) and low limits of quantification (from 3.8 pg m(-3) for L3 to 320 pg m(-3) for D4). However, the analysis of D3 and D4 was confounded by the transformation of D5 to these analytes on the sampling cartridge. During a sampling campaign with a daily temporal resolution between November 4 and December 14 2011, all analytes with the exception of L5 and L6 could be quantified in all samples. It was hypothesized that the ratio of the concentrations of different VMS reflected the relative strength of their emissions to the airshed due to the slow phototransformation of the VMS at high latitudes in winter. This was supported by available emissions information.

  • 25. Krecl, Patricia
    et al.
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm Environment and Health Administration, Sweden.
    Créso Targino, Admir
    Ström, Johan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Burman, Lars
    Trends in black carbon and size-resolved particle number concentrations and vehicle emission factors under real-world conditions2017In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 165, p. 155-168Article in journal (Refereed)
    Abstract [en]

    Kerbside concentrations of NOx, black carbon (BC), total number of particles (diameter > 4 nm) and number size distribution (28-410 nm) were measured at a busy street canyon in Stockholm in 2006 and 2013. Over this period, there was an important change in the vehicle fleet due to a strong dieselisation process of light-duty vehicles and technological improvement of vehicle engines. This study assesses the impact of these changes on ambient concentrations and particle emission factors (EF). EF were calculated by using a novel approach which combines the NOx tracer method with positive matrix factorisation (PMF) applied to particle number size distributions. NOx concentrations remained rather constant between these two years, whereas a large decrease in particle concentrations was observed, being on average 60% for BC, 50% for total particle number, and 53% for particles in the range 28-100 nm. The PMF analysis yielded three factors that were identified as contributions from gasoline vehicles, diesel fleet, and urban background. This separation allowed the calculation of the average vehicle EF for each particle metric per fuel type. In general, gasoline EF were lower than diesel EF, and EF for 2013 were lower than the ones derived for 2006. The EFBC decreased 77% for both gasoline and diesel fleets, whereas the particle number EF reduction was higher for the gasoline (79%) than for the diesel (37%) fleet. Our EF are consistent with results from other on-road studies, which reinforces that the proposed methodology is suitable for EF determination and to assess the effectiveness of policies implemented to reduce vehicle exhaust emissions. However, our EF are much higher than EF simulated with traffic emission models (HBEFA and COPERT) that are based on dynamometer measurements, except for EFBC for diesel vehicles. This finding suggests that the EF from the two leading models in Europe should be revised for BC (gasoline vehicles) and particle number (all vehicles), since they are used to compile national inventories for the road transportation sector and also to assess their associated health effects. Using the calculated kerbside EF, we estimated that the traffic emissions were lower in 2013 compared to 2006 with a 61% reduction for BC (due to decreases in both gasoline and diesel emissions), and 34-45% for particle number (reduction only in gasoline emissions). Limitations of the application of these EF to other studies are also discussed.

  • 26.
    Krecl, Patricia
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Ström, Johan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Diurnal variation of atmospheric aerosol during the wood combustion season in Northern Sweden2008In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 42, no 18, p. 4113-4125Article in journal (Refereed)
    Abstract [en]

    A set of aerosol measurements was conducted in the residential area of Forsdala in Lycksele, Northern Sweden, during winter 2005/2006. This article describes the temporal and diurnal variation of the aerosol physical properties (concentrations of PM10, PM1, light-absorbing carbon, and particle number, and number size distributions), and the relationship among aerosol concentrations and meteorological variables. A large day-to-day and hour-to-hour variability in aerosol concentrations was observed during the intensive study period. Evening aerosol concentrations were statistically significantly higher on weekends than on weekdays. On weekdays, particle size distribution and concentrations varied diurnally with small particles (diameter <30 nm) associated mainly with morning motor vehicle emissions. The results suggest that a combination of emissions from residential wood combustion and traffic sources might explain the high evening concentrations of PM10, PM1, particle number, and light-absorbing carbon as well as large geometric mean diameters observed during weekdays and weekends. Strong correlations of PM10 and PM1 with particle size distributions are found in the diameter range 130–500 nm and are remarkably high on weekend evenings when larger particles are sampled. The correlation between light-absorbing carbon mass concentration and particle size distribution is high regarding both particle number and mass for particle diameters >95 nm. High aerosol concentrations were associated with low air temperatures and very stable atmospheric conditions close to the ground.

  • 27.
    Masala, Silvia
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Lim, Hwanmi
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Environment and Health Administration, Sweden.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Determination of semi-volatile and particle-associated polycyclic aromatic hydrocarbons in Stockholm air with emphasis on the highly carcinogenic dibenzopyrene isomers2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 140, p. 370-380Article in journal (Refereed)
    Abstract [en]

    The concentrations of polycyclic aromatic hydrocarbons (PAHs) have been determined in the gaseous phase and in various particulate matter (PM) size fractions at different locations in and outside of Stockholm, Sweden, representative of street level, urban and rural background. The focus has been on the seldom determined but highly carcinogenic dibenzopyrene isomers (DBPs) dibenzo[a,I]pyrene, dibenzo [a,e]pyrene, dibenzo[a,i]pyrene and dibenzo[a,h]pyrene. PAHs with 3 rings were found to be mainly associated with the vapor phase (>90%) whereas PAHs with 5-6 rings were mostly associated with particulate matter (>92%) and the 4-ringed PAHs partitioned between the two phases. PAH abundance was determined to be in the order street level > urban background > rural background with the PM10 street level 2010 mean of benzo[a]pyrene (B[a]P) reaching 0.24 ng/m(3), well below the EU annual limit value of 1 ng/m(3). In addition, higher PAH concentrations were found in the sub-micron particle fraction (PM1) as compared to the super -micron fraction (PM1-10) with the abundance in PM1 varying between 57 and 86% of the total PAHs. The B[a]P equivalent concentrations derived for DB[a,l]P and total DBPs exceeded 1-2 and 2-4 times, respectively, that of B[a]P at the four sampling sites; therefore underestimation of the cancer risk posed by PAHs in air could be made if the DBPs were not considered in risk assessment using the toxic equivalency approach, whilst the high correlation (p < 0.001) found in the relative concentrations supports the use of B[a]P as a marker substance for assessment of the carcinogenic risk associated to PAHs. However, the big difference in concentration ratios of B[a]P and the DBPs between the present study and some literature data calls for further research to evaluate the temporal and spatial invariance of the B[a]P/DBP ratios.

  • 28.
    McLachlan, Michael S
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Sellström, Ulla
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Precipitation scavenging of particle-bound contaminants: A case study of PCDD/Fs2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 38, p. 6084-6090Article in journal (Other academic)
    Abstract [en]

    Precipitation scavenging of particles is a major mechanism for atmospheric deposition of organic contaminants, but there have been few field studies. We studied precipitation scavenging of PCDD/Fs with the aim of deepening understanding of environmental variables influencing this process. Bulk deposition of PCDD/Fs and their concentrations in ambient air measured at a background site in Sweden were used to calculate precipitation scavenging ratios. Contrary to expectations, increasing scavenging ratios with decreasing degree of chlorination of the PCDD/F congeners were observed when the particle-associated PCDD/F concentrations in air were used for the calculation. This was attributed to differences in temperature and thereby in the gas - particle partitioning of the PCDD/Fs between ground level and clouds where much of the particle scavenging occurs. When the particle-associated PCDD/F concentrations were recalculated for a 10-20 degrees C lower temperature, the scavenging ratios of the different PCDD/F congeners were similar. Hence differences between ground level and in-cloud temperature should be considered when calculating scavenging ratios from field observations and when modeling this process. The scavenging ratios averaged similar to 200 000, with lower values when the particle-associated PCDD/F concentration in air was lower. The soot concentration in air was a good predictor of bulk deposition of PCDD/Fs.

  • 29. Monks, P. S.
    et al.
    Granier, C.
    Fuzzi, S.
    Stohl, A.
    Williams, M. L.
    Akimoto, H.
    Amann, M.
    Baklanov, A.
    Baltensperger, U.
    Bey, I.
    Blake, N.
    Blake, R. S.
    Carslaw, K.
    Cooper, O. R.
    Dentener, F.
    Fowler, D.
    Fragkou, E.
    Frost, G. J.
    Generoso, S.
    Ginoux, P.
    Grewe, V.
    Guenther, A.
    Hansson, Hans-Christen
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Henne, S.
    Hjorth, J.
    Hofzumahaus, A.
    Huntrieser, H.
    Isaksen, I. S. A.
    Jenkin, M. E.
    Kaiser, J.
    Kanakidou, M.
    Klimont, Z.
    Kulmala, M.
    Laj, P.
    Lawrence, M. G.
    Lee, J. D.
    Liousse, C.
    Maione, M.
    McFiggans, G.
    Metzger, A.
    Mieville, A.
    Moussiopoulos, N.
    Orlando, J. J.
    O'Dowd, C. D.
    Palmer, P. I.
    Parrish, D. D.
    Petzold, A.
    Platt, U.
    Poeschl, U.
    Prevot, A. S. H.
    Reeves, C. E.
    Reimann, S.
    Rudich, Y.
    Sellegri, K.
    Steinbrecher, R.
    Simpson, D.
    ten Brink, H.
    Theloke, J.
    van der Werf, G. R.
    Vautard, R.
    Vestreng, V.
    Vlachokostas, Ch.
    von Glasow, R.
    Atmospheric composition change: global and regional air quality2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 33, p. 5268-5350Article, review/survey (Refereed)
    Abstract [en]

    Air quality transcends all scales with in the atmosphere from the local to the global with handovers and feedbacks at each scale interaction. Air quality has manifold effects on health, ecosystems heritage and, climate. In this review the state of scientific understanding in relation to global and regional air quality is outlined. The review discusses air quality, in terms of emissions, processing and transport of trace gases and aerosols. New insights into the characterization of both natural and anthropogenic emissions are reviewed looking at both natural (e.g. dust and lightning) as well as plant emissions. Trends in anthropogenic emissions both by region and globally are discussed as well as biomass burning emissions. In terms of chemical processing the major air quality elements of ozone, non-methane hydrocarbons, nitrogen oxides and aerosols are covered. A number of topics are presented as a way of integrating the process view into the atmospheric context; these include the atmospheric oxidation efficiency, halogen and HOx chemistry, nighttime chemistry, tropical chemistry, heat waves, megacities, biomass burning and the regional hot spot of the Mediterranean. New findings with respect to the transport of pollutants across the scales are discussed, in particular the move to quantify the impact of long-range transport on regional air quality. Gaps and research questions that remain intractable are identified. The review concludes with a focus of research and policy questions for the coming decade. In particular, the policy challenges for concerted air quality and climate change policy (co-benefit) are discussed.

  • 30. Nielsen, Ingeborg E.
    et al.
    Eriksson, Axel C.
    Lindgren, Robert
    Martinsson, Johan
    Nyström, Robin
    Nordin, Erik Z.
    Sadiktsis, Ioannis
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Boman, Christoffer
    Nøjgaard, Jacob K.
    Pagels, Joakim
    Time-resolved analysis of particle emissions from residential biomass combustion – Emissions of refractory black carbon, PAHs and organic tracers2017In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 165, p. 179-190Article in journal (Refereed)
    Abstract [en]

    Time-resolved particle emissions from a conventional wood stove were investigated with aerosol mass spectrometry to provide links between combustion conditions, emission factors, mixing state of refractory black carbon and implications for organic tracer methods. The addition of a new batch of fuel results in low temperature pyrolysis as the fuel heats up, resulting in strong, short-lived, variable emission peaks of organic aerosol-containing markers of anhydrous sugars, such as levoglucosan (fragment at m/z 60). Flaming combustion results in emissions dominated by refractory black carbon co-emitted with minor fractions of organic aerosol and markers of anhydrous sugars. Full cycle emissions are an external mixture of larger organic aerosol-dominated and smaller thinly coated refractory black carbon particles. A very high burn rate results in increased full cycle mass emission factors of 66, 2.7, 2.8 and 1.3 for particulate polycyclic aromatic hydrocarbons, refractory black carbon, total organic aerosol and m/z 60, respectively, compared to nominal burn rate. Polycyclic aromatic hydrocarbons are primarily associated with refractory black carbon-containing particles. We hypothesize that at very high burn rates, the central parts of the combustion zone become air starved, leading to a locally reduced combustion temperature that reduces the conversion rates from polycyclic aromatic hydrocarbons to refractory black carbon. This facilitates a strong increase of polycyclic aromatic hydrocarbons emissions. At nominal burn rates, full cycle emissions based on m/z 60 correlate well with organic aerosol, refractory black carbon and particulate matter. However, at higher burn rates, m/z 60 does not correlate with increased emissions of polycyclic aromatic hydrocarbons, refractory black carbon and organic aerosol in the flaming phase. The new knowledge can be used to advance source apportionment studies, reduce emissions of genotoxic compounds and model the climate impacts of refractory black carbon, such as absorption enhancement by lensing.

  • 31. Nordin, Erik Z.
    et al.
    Uski, Oskari
    Nyström, Robin
    Jalava, Pasi
    Eriksson, Axel C.
    Genberg, Johan
    Roldin, Pontus
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jokiniemi, Jorma
    Pagels, Joakim H.
    Boman, Christoffer
    Hirvonen, Maija-Riitta
    Influence of ozone initiated processing on the toxicity of aerosol particles from small scale wood combustion2015In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 102, p. 282-289Article in journal (Refereed)
    Abstract [en]

    Black carbon containing emissions from biomass combustion are being transformed in the atmosphere upon processing induced by tropospheric ozone and UV. The knowledge today is very limited on how atmospheric processing affects the toxicological properties of the emissions. The aim of this study was to investigate the influence of ozone initiated (dark) atmospheric processing on the physicochemical and toxicological properties of particulate emissions from wood combustion. Emissions from a conventional wood stove operated at two combustion conditions (nominal and hot air starved) were diluted and transferred to a chamber. Particulate matter (PM) was collected before and after ozone addition to the chamber using an impactor. Detailed chemical and physical characterization was performed on chamber air and collected PM. The collected PM was investigated toxicologically in vitro with a mouse macrophage model, endpoints included: cell cycle analysis, viability, inflammation and genotoxicity. The results suggest that changes in the organic fraction, including polycyclic aromatic hydrocarbons (PAHs) are the main driver for differences in obtained toxicological effects. Fresh hot air starved emissions containing a higher organic and PAH mass-fraction affected cell viability stronger than fresh emissions from nominal combustion. The PAH mass fractions decreased upon aging due to chemical degradation. Dark aging increased genotoxicity, reduced viability and reduced release of inflammatory markers. These differences were statistically significant for single doses and typically less pronounced. We hypothesize that the alterations in toxicity upon simulated dark aging in the atmosphere may be caused by reaction products that form when PAHs and other organic compounds react with ozone and nitrate radicals. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).

  • 32. Norman, M.
    et al.
    Sundvor, I.
    Denby, B. R.
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Environment and Health Administration of the City of Stockholm, Sweden.
    Gustafsson, M.
    Blomqvist, G.
    Janhäll, S.
    Modelling road dust emission abatement measures using the NORTRIP model: Vehicle speed and studded tyre reduction2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 134, p. 96-108Article in journal (Refereed)
    Abstract [en]

    Road dust emissions in Nordic countries still remain a significant contributor to PM10 concentrations mainly due to the use of studded tyres. A number of measures have been introduced in these countries in order to reduce road dust emissions. These include speed reductions, reductions in studded tyre use, dust binding and road cleaning. Implementation of such measures can be costly and some confidence in the impact of the measures is required to weigh the costs against the benefits. Modelling tools are thus required that can predict the impact of these measures. In this paper the NORTRIP road dust emission model is used to simulate real world abatement measures that have been carried out in Oslo and Stockholm. In Oslo both vehicle speed and studded tyre share reductions occurred over a period from 2004 to 2006 on a major arterial road, RV4. In Stockholm a studded tyre ban on Hornsgatan in 2010 saw a significant reduction in studded tyre share together with a reduction in traffic volume. The model is found to correctly simulate the impact of these measures on the PM10 concentrations when compared to available kerbside measurement data. Importantly meteorology can have a significant impact on the concentrations through both surface and dispersion conditions. The first year after the implementation of the speed reduction on RV4 was much drier than the previous year, resulting in higher mean concentrations than expected. The following year was much wetter with significant rain and snow fall leading to wet or frozen road surfaces for 83% of the four month study period. This significantly reduced the net PM10 concentrations, by 58%, compared to the expected values if meteorological conditions had been similar to the previous years. In the years following the studded tyre ban on Hornsgatan road wear production through studded tyres decreased by 72%, due to a combination of reduced traffic volume and reduced studded tyre share. However, after accounting for exhaust contributions and the impact of meteorological conditions in the model calculations then the net mean reduction in PM10 concentrations was only 50%, in agreement with observations. The NORTRIP model is shown to be able to reproduce the impacts of both traffic measures and meteorology on traffic induced PM10 concentrations, making it a unique and valuable tool for predicting the impact of measures for air quality management applications.

  • 33. Putaud, J. -P
    et al.
    Van Dingenen, R.
    Alastuey, A.
    Bauer, H.
    Birmili, W.
    Cyrys, J.
    Flentje, H.
    Fuzzi, S.
    Gehrig, R.
    Hansson, Hans-Christen
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Harrison, R. M.
    Herrmann, H.
    Hitzenberger, R.
    Hueglin, C.
    Jones, A. M.
    Kasper-Giebl, A.
    Kiss, G.
    Kousa, A.
    Kuhlbusch, T. A. J.
    Loeschau, G.
    Maenhaut, W.
    Molnar, A.
    Moreno, T.
    Pekkanen, J.
    Perrino, C.
    Pitz, M.
    Puxbaum, H.
    Querol, X.
    Rodriguez, S.
    Salma, I.
    Schwarz, J.
    Smolik, J.
    Schneider, J.
    Spindler, G.
    ten Brink, H.
    Tursic, J.
    Viana, M.
    Wiedensohler, A.
    Raes, F.
    A European aerosol phenomenology-3: Physical and chemical characteristics of particulate matter from 60 rural, urban, and kerbside sites across Europe2010In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 44, no 10, p. 1308-1320Article in journal (Refereed)
    Abstract [en]

    This paper synthesizes data on aerosol (particulate matter, PM) physical and chemical characteristics, which were obtained over the past decade in aerosol research and monitoring activities at more than 60 natural background, rural, near-city, urban, and kerbside sites across Europe. The data include simultaneously measured PM10 and/or PM2.5 mass on the one hand, and aerosol particle number concentrations or PM chemistry on the other hand. The aerosol data presented in our previous works (Van Dingenen et al., 2004; Putaud et al., 2004) were updated and merged to those collected in the framework of the EU supported European Cooperation in the field of Scientific and Technical action COST633 (Particulate matter: Properties related to health effects). A number of conclusions from our previous studies were confirmed. There is no single ratio between PM2.5 and PM10 mass concentrations valid for all sites, although fairly constant ratios ranging from 0.5 to 0.9 are observed at most individual sites. There is no general correlation between PM mass and particle number concentrations, although particle number concentrations increase with PM2.5 levels at most sites. The main constituents of both PM10 and PM2.5 are generally organic matter, sulfate and nitrate. Mineral dust can also be a major constituent of PM10 at kerbside sites and in Southern Europe. There is a clear decreasing gradient in SO42- and NO3- contribution to PM10 when moving from rural to urban to kerbside sites. In contrast, the total carbon/PM10 ratio increases from rural to kerbside sites. Some new conclusions were also drawn from this work: the ratio between ultrafine particle and total particle number concentration decreases with PM2.5 concentration at all sites but one, and significant gradients in PM chemistry are observed when moving from Northwestern, to Southern to Central Europe. Compiling an even larger number of data sets would have further increased the significance of our conclusions, but collecting all the aerosol data sets obtained also through research projects remains a tedious task.

  • 34. Rao, P. S. P.
    et al.
    Tiwari, Suresh
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Indian Institute of Tropical Meteorology, Pune, India.
    Matwale, J. L.
    Pervez, S.
    Tunved, Peter
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Safai, P. D.
    Srivastava, A. K.
    Bisht, D. S.
    Singh, S.
    Hopke, P. K.
    Sources of chemical species in rainwater during monsoon and non-monsoonal periods over two mega cities in India and dominant source region of secondary aerosols2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 146, p. 90-99Article in journal (Refereed)
    Abstract [en]

    Samples of rainwater (RW) were collected to characterize the chemistry and sources in two representative megacities at Pune (Southwest) and Delhi (Northern) India from 2011 to 2014 across two seasons: monsoon (MN) and non-monsoon (NMN). Collected RW samples were analyzed for major chemical constituents (F-, Cl-, SO42-, NO3-, NH4+, Na+, K+, Ca2+, and Mg2+), pH and conductivity. In addition, bicarbonate (HCO3-) was also estimated. The mean pH values of the RW were >6 at Pune and <6 at Delhi and 4% and 26% were acidic, respectively. The mean sum of all measured ionic species in Pune and Delhi was 304.7 and 536.4 mu ep/l, respectively, indicating that significant atmospheric pollution effects in these Indian mega cities. Both the Ca2+ and SO42- were the dominant ions, accounting for 43% (Pune) and 54% (Delhi) of the total ions. The sum of measured ions during the NMN period was greater than the NM period by a factor of 1.5 for Pune (278.4: NM and 412.1: NMN mu eq/l) and a factor of about 2.5 for Delhi (406 and 1037.7 mu eq/l). The contributions of SO42- and NO3- to the RW acidity were similar to 40% and 60%, respectively, at Pune and correspondingly, 36% and 64% at Delhi. The concentrations of secondary aerosols (SO42- and NO3-) were higher by a factor of two and three when the air masses were transported to Pune from the continental side. At Delhi, the concentrations of SO42-, NO3-, Ca2+, and Mg2+ were significantly higher when the air masses arrive from Punjab, Haryana, and Pakistan indicating the greater atmospheric pollution over the Indo-Gangetic Plain. Positive matrix factorization was applied to the source apportionment of the deposition fluxes of these ions. Three factors were obtained for Pune and four for Delhi. The sources at Pune were secondary aerosols from fossil fuel combustion, soil dust, and marine, whereas, at Delhi, the sources were soil, fossil fuel combustion, biomass burning, and industrial chlorine.

  • 35. Rose, C.
    et al.
    Sellegri, K.
    Velarde, F.
    Moreno, I.
    Ramonet, M.
    Weinhold, K.
    Krejci, Radovan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Ginot, Patrick
    Andrade, M.
    Wiedensohler, A.
    Laj, P.
    Frequent nucleation events at the high altitude station of Chacaltaya (5240 m a.s.l.), Bolivia2015In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 102, p. 18-29Article in journal (Refereed)
    Abstract [en]

    While nucleation may represent one of the major processes responsible for the total aerosol number burden in the atmosphere, and especially at high altitude, new particle formation (NPF) events occurring in the upper part of the troposphere are poorly documented in the literature, particularly in the southern hemisphere. NPF events were detected and analyzed at the highest measurement site in the world, Chacaltaya (5240 m a.s.l.), Bolivia between January 1 and December 31 2012, using a Neutral Aerosol and Ion Spectrometer (NAIS) that detects clusters down to 0.4 nm. NPF frequency at Chacaltaya is one of the highest reported so far (63.9%) and shows a clear seasonal dependency with maximum up to 100% during the dry season. This high seasonality of the NPF events frequency was found to be likely linked to the presence of clouds in the vicinity of the station during the wet season. Multiple NPF events are seen on almost 50% of event days and can reach up to 6 events per day, increasing the potential of nucleation to be the major contributor to the particle number concentrations in the upper troposphere. Ion-induced nucleation (IIN) was 14.8% on average, which is higher than the IIN fractions reported for boundary layer stations. The median formation rate of 2 nm particles computed for first position events is increased during the dry season (1.90 cm(-3) s(-1)) compared to the wet season (1.02 cm(-3) s(-1)), showing that events are more intense, on top of being more frequent during the dry season. On the contrary, particle growth rates (GRs) are on average enhanced during the wet season, which could be explained by higher amount of biogenic volatile organic compounds transported from the Amazon rainforest. The NPF events frequency is clearly enhanced when air masses originate from the oceanic sector, with a frequency of occurrence close to 1. However, based on the particle GRs, we calculate that particles most likely nucleate after the oceanic air masses reach the land and are presumably not originating from the marine free troposphere. The high frequency of NPF events, the occurrence of multiple events per day, and the relatively high formation rates observed at Chacaltaya imply that nucleation and growth are likely to be the major mechanism feeding the upper atmosphere with aerosol particles in this part of the continent.

  • 36.
    Sellström, Ulla
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Egebäck, Anna Lena
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    McLachlan, Michael S
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Identifying source regions for the atmospheric input of PCDD/Fs to the Baltic Sea2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 10, p. 1730-1736Article in journal (Other academic)
    Abstract [en]

    PCDD/F contamination of the Baltic Sea has resulted in the European Union imposing restrictions on the marketing of several fish species. Atmospheric deposition is the major source of PCDD/Fs to the Baltic Sea, and hence there is a need to identify the source regions of the PCDD/Fs in ambient air over the Baltic Sea. A novel monitoring strategy was employed to address this question. During the winter of 2006-2007 air samples were collected in Aspvreten (southern Sweden) and Pallas (northern Finland). Short sampling times (24 h) were employed and only samples with stable air mass back trajectories were selected for analysis of the 2,3,7,8-substituted PCDD/F congeners. The range in the PCDD/F concentrations from 40 samples collected at Aspvreten was a factor of almost 50 (range 0.6-29 fg TEQ/m(3)). When the samples were grouped according to air mass origin into seven compass sectors, the variability was much lower (typically less than a factor of 3). This indicates that air mass origin was the primary source of the variability. The contribution of each sector to the PCDD/F contamination over the Baltic Sea during the winter half year of 2006/2007 was calculated from the average PCDD/F concentration for each sector and the frequency with which the air over the Baltic Sea came from that sector. Air masses originating from the south-southwest, south-southeast and east segments contributed 65% of the PCDDs and 75% of the PCDFs. Strong correlations were obtained between the concentrations of most of the PCDD/F congeners and the concentration of soot. These correlations can be used to predict the PCDD/F concentrations during the winter half year from inexpensive soot measurements.

  • 37. Sheesley, Rebecca J.
    et al.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Source characterization of organic aerosols using Monte Carlo source apportionment of PAHs at two South Asian receptor sites2011In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 45, no 23, p. 3874-3881Article in journal (Refereed)
    Abstract [en]

    The quantification of source contributions is of key importance for proposing environmental mitigation strategies for particulate organic matter. Organic molecular tracer analysis of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes was conducted on a set of winter samples from two regional receptor sites in South Asia: the Island of Hanimaadhoo (the Republic of Maldives) and a mountain top near Sinhagad (W. India). Monte Carlo source apportionment (MCSA) techniques were applied to the observed PAH ratios using profiles of a representative range of regional combustion sources from the literature to estimate the relative source contributions from petroleum combustion, coal combustion and biomass burning. One advantage of this methodology is the combined use of the mean and standard deviation of the diagnostic ratios to calculate probability distribution functions for the fractional contributions from petroleum, coal and biomass combustion. The results of this strategy indicate a higher input from coal combustion at the Hanimaadhoo site (32-43 +/- 21%) than the Sinhagad site (24-25 +/- 18%). The estimated biomass contribution for Sinhagad (53 +/- 22%) parallels previous radiocarbon-based source apportionment of elemental carbon at this location (54 +/- 3%). In Hanimaadhoo, the MCSA results indicate 34 +/- 20% biomass burning contribution compared to 41 +/- 5% by radiocarbon apportionment of EC. While the MCSA based on PAH ratio diagnostic distributions are less precise than the radiocarbon-based apportionment, it provides additional information of the relative contribution of two subgroups, coal and petroleum combustion, within the overall contribution from fossil fuel combustion.

  • 38. Thomas, Manu Anna
    et al.
    Brännström, Niklas
    Persson, Christer
    Grahn, Håkan
    von Schoenberg, Pontus
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. The Swedish Defence Research Agency, FOI, Sweden.
    Robertson, Lennart
    Surface air quality implications of volcanic injection heights2017In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 166, p. 510-518Article in journal (Refereed)
    Abstract [en]

    Air quality implications of volcanic eruptions have gained increased attention recently in association with the 2010 Icelandic eruption that resulted in the shut-down of European air space. The emission amount, injection height and prevailing weather conditions determine the extent of the impact through the spatio-temporal distribution of pollutants. It is often argued that in the case of a major eruption in Iceland, like Laki in 1783-1784, that pollutants injected high into the atmosphere lead to substantially increased concentrations of sulfur compounds over continental Europe via long-range transport in the jet stream and eventual large-scale subsidence in a high-pressure system. Using state-of-the-art simulations, we show that the air quality impact of Icelandic volcanoes is highly sensitive to the injection height. In particular, it is the infinitesimal injections into the lower half of the troposphere, rather than the substantial injections into the upper troposphere/lower stratosphere that contribute most to increased pollutant concentrations, resulting in atmospheric haze over mainland Europe/Scandinavia. Besides, the persistent high pressure system over continental Europe/Scandinavia traps the pollutants from dispersing, thereby prolonging the haze.

  • 39. Titos, G.
    et al.
    Cazorla, A.
    Zieger, Paul
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Andrews, E.
    Lyamani, H.
    Granados-Munoz, M. J.
    Olmo, F. J.
    Alados-Arboledas, L.
    Effect of hygroscopic growth on the aerosol light-scattering coefficient: A review of measurements, techniques and error sources2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 141, p. 494-507Article, review/survey (Refereed)
    Abstract [en]

    Knowledge of the scattering enhancement factor,.f(RH), is important for an accurate description of direct aerosol radiative forcing. This factor is defined as the ratio between the scattering coefficient at enhanced relative humidity, RH, to a reference (dry) scattering coefficient. Here, we review the different experimental designs used to measure the scattering coefficient at dry and humidified conditions as well as the procedures followed to analyze the measurements. Several empirical parameterizations for the relationship between f(RH) and RH have been proposed in the literature. These parameterizations have been reviewed and tested using experimental data representative of different hygroscopic growth behavior and a new parameterization is presented. The potential sources of error in f(RH) are discussed. A Monte Carlo method is used to investigate the overall measurement uncertainty, which is found to be around 20-40% for moderately hygroscopic aerosols. The main factors contributing to this uncertainty are the uncertainty in RH measurement, the dry reference state and the nephelometer uncertainty. A literature survey of nephelometry-based f(RH) measurements is presented as a function of aerosol type. In general, the highest f(RH) values were measured in clean marine environments, with pollution having a major influence on f(RH). Dust aerosol tended to have the lowest reported hygroscopicity of any of the aerosol types studied. Major open questions and suggestions for future research priorities are outlined.

  • 40. Toledano, C.
    et al.
    Cachorro, V. E.
    Gausa, M.
    Stebel, K.
    Aaltonen, V.
    Berjon, A.
    Ortiz de Galisteo, J. P.
    de Frutos, A. M.
    Bennouna, Y.
    Blindheim, S.
    Myhre, C. L.
    Zibordi, G.
    Wehrli, C.
    Kratzer, Susanne
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Håkansson, B.
    Carlund, T.
    de Leeuw, G.
    Herber, A.
    Torres, B.
    Overview of sun photometer measurements of aerosol properties in Scandinavia and Svalbard2012In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 52, p. 18-28Article in journal (Refereed)
    Abstract [en]

    An overview on the data of columnar aerosol properties measured in Northern Europe is provided. Apart from the necessary data gathered in the Arctic, the knowledge of the aerosol loading in nearby areas (e.g. sub-Arctic) is of maximum interest to achieve a correct analysis of the Arctic aerosols and transport patterns. This work evaluates data from operational sites with sun photometer measurements belonging either to national or international networks (AERONET, GAW-PFR) and programs conducted in Scandinavia and Svalbard. We enumerate a list of sites, measurement type and periods together with observed aerosol properties. An evaluation and analysis of aerosol data was carried out with a review of previous results as well. Aerosol optical depth (AOD) and Angstrom exponent (AE) are the current parameters with sufficient long-term records for a first evaluation of aerosol properties. AOD (500 nm) ranges from 0.08 to 0.10 in Arctic and sub-Arctic sites (Ny-Alesund: 0.09; Andenes: 0.10; Sodankyla: 0.08), and it is somewhat higher in more populated areas in Southern Scandinavia (AOD about 0.10-0.12 at 500 nm). On the Norwegian coast, aerosols show larger mean size (AE = 1.2 at Andenes) than in Finland, with continental climate (AE = 1.5 at Sodankyla). Columnar particle size distributions and related parameters derived from inversion of sun/sky radiances were also investigated. This work makes special emphasis in the joint and collaborative effort of the various groups from different countries involved in this study. Part of the measurements presented here were involved in the IPY projects Polar-AOD and POLARCAT.

  • 41.
    Vogt, Matthias
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Nilsson, E. D.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Ahlm, Lars
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Mårtensson, E. M.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Struthers, Hamish
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Johansson, Christer
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Traffic Aerosol emission velocity derived from direct flux measurements over urban Stockholm, Sweden2011In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 45, no 32, p. 5725-5731Article in journal (Refereed)
    Abstract [en]

    Size-resolved aerosol vertical number fluxes were measured using the eddy covariance method, 105 meters above the ground over the city of Stockholm, Sweden, between 1st April 2008 and 15th April 2009. The size range of the measurements cover particles from 0.25 to 2.5 μm diameter (Dp). Emission velocities (ve) were calculated for the same size range and were found to be well correlated with friction velocity (u*) and CO2 fluxes (FCO2). These variables were used to parameterize the emission velocity aswhere ve and u* are given in [m s−1], Dp in [μm], and FCO2 in [mmol m−2s−1].

    The parameterization reproduces the average diurnal cycle from the observations well for particles sizes up to 0.6 μm Dp. For larger particles the parameterization tends to over predict the emission velocity. These larger particles are not believed to be produced by combustion and therefore not well represented by FCO2, which represents the traffic source through its fossil fuel consumption and the related CO2 emissions.

  • 42. Weinbruch, Stephan
    et al.
    Wiesemann, David
    Ebert, Martin
    Schuetze, Katharina
    Kallenborn, Roland
    Ström, Johan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Chemical composition and sources of aerosol particles at Zeppelin Mountain (Ny Alesund, Svalbard): An electron microscopy study2012In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 49, p. 142-150Article in journal (Refereed)
    Abstract [en]

    Aerosol particles were collected at the Zeppelin Mountain Atmospheric Research Station (474 m asl) near Ny Alesund (Svalbard, Norway) on 27 different days between July 2007 and December 2008. The size, morphology and chemical composition of 57,617 individual particles were studied by high-resolution scanning electron microscopy and energy-dispersive X-ray microanalysis. Based on chemical composition, morphology, mixing state and stability under electron bombardment, the particles were assigned to one of the following groups: sea salt, aged sea salt, Ca sulphates, Na sulphates, carbonates, soot, silicates, fly ashes, secondary aerosol, secondary aerosol plus sodium, secondary aerosol plus soot, mixed particles and others. Sea salt, aged sea salt, silicates and mixed particles (mixtures of sea salt, silicates and Ca sulphates) are the most abundant groups for particles with aerodynamic diameters > 0.5 mu m, secondary aerosol, mixed particles and secondary aerosol with soot inclusions below 0.5 mu m. Silicate fly ashes (major source coal burning) and metal fly ashes (from metallurgical high temperature processes) occur only at very low number concentrations. In contrast to previous work, the fly ash abundance is not correlated with air masses that crossed industrialized regions in Central and Eastern Europe, Scandinavia or Russia. These observations indicate a significant reduction of long-range transport of heavy metals to Svalbard. Soot (external and internally mixed with secondary aerosol) shows a pronounced seasonal pattern with a much lower abundance during summer compared to spring, autumn and winter. The soot abundance is not correlated with the air mass back-trajectories. During summer (July and August), soot was only observed when cruise ships were present in the area around Ny Alesund (Kongsfjorden). Pronounced seasonal patterns were observed for the abundance of the mineral dust component which is generally lower in summer compared to the other seasons. The observed seasonal dependence of anthropogenic primary particles (soot, fly ashes) is in good agreement with the Arctic circulation pattern.

  • 43. Wiedensohler, A.
    et al.
    Andrade, M.
    Weinhold, K.
    Mueller, T.
    Birmili, W.
    Velarde, F.
    Moreno, I
    Forno, R.
    Sanchez, M. F.
    Laj, P.
    Ginot, P.
    Whiteman, D. N.
    Krejci, Radovan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Sellegri, K.
    Reichler, T.
    Black carbon emission and transport mechanisms to the free troposphere at the La Paz/El Alto (Bolivia) metropolitan area based on the Day of Census (2012)2018In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 194, p. 158-169Article in journal (Refereed)
    Abstract [en]

    Urban development, growing industrialization, and increasing demand for mobility have led to elevated levels of air pollution in many large cities in Latin America, where air quality standards and WHO guidelines are frequently exceeded. The conurbation of the metropolitan area of La Paz/El Alto is one of the fastest growing urban settlements in South America with the particularity of being located in a very complex terrain at a high altitude. As many large cities or metropolitan areas, the metropolitan area of La Paz/El Alto and the Altiplano region are facing air quality deterioration. Long-term measurement data of the equivalent black carbon (eBC) mass concentrations and particle number size distributions (PNSD) from the Global Atmosphere Watch Observatory Chacaltaya (CHC; 5240 m a.s.l., above sea level) indicated a systematic transport of particle matter from the metropolitan area of La Paz/El Alto to this high altitude station and subsequently to the lower free troposphere. To better understand the sources and the transport mechanisms, we conducted eBC and PNSDs measurements during an intensive campaign at two locations in the urban area of La Paz/El Alto from September to November 2012. While the airport of El Alto site (4040 m a.s.l.) can be seen as representative of the urban and Altiplano background, the road site located in Central La Paz (3590 m a.s.l.) is representative for heavy traffic-dominated conditions. Peaks of eBC mass concentrations up to 5 mu g m(-3) were observed at the El Alto background site in the early morning and evening, while minimum values were detected in the early afternoon, mainly due to thermal convection and change of the planetary boundary layer height. The traffic-related eBC mass concentrations at the road site reached maximum values of 10-20 mu g m(-3). A complete traffic ban on the specific Bolivian Day of Census (November 21, 2012) led to a decrease of eBC below 1 mu g m(-3) at the road site for the entire day. Compared to the day before and after, particle number concentrations decreased by a factor between 5 and 25 over the particle size range from 10 to 800 nm, while the submicrometer particle mass concentration dropped by approximately 80%. These results indicate that traffic is the dominating source of BC and particulate air pollution in the metropolitan area of La Paz/El Alto. In general, the diurnal cycle of eBC mass concentration at the Chacaltaya observatory is anti-correlated to the observations at the El Alto background site. This pattern indicates that the traffic-related particulate matter, including BC, is transported to higher altitudes with the developing of the boundary layer during daytime. The metropolitan area of La Paz/El Alto seems to be a significant source for BC of the regional lower free troposphere. From there, BC can be transported over long distances and exert impact on climate and composition of remote southern hemisphere.

  • 44. Yan, Caiqing
    et al.
    Zheng, Mei
    Sullivan, Amy P.
    Bosch, Carme
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Desyaterik, Yury
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Li, Xiaoying
    Guo, Xiaoshuang
    Zhou, Tian
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Collett, Jeffrey L.
    Chemical characteristics and light-absorbing property of water-soluble organic carbon in Beijing: Biomass burning contributions2015In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 121, p. 4-12Article in journal (Refereed)
    Abstract [en]

    Emissions from biomass burning contribute significantly to water-soluble organic carbon (WSOC) and light-absorbing organic carbon (brown carbon). Ambient atmospheric samples were collected at an urban site in Beijing during winter and summer, along with source samples from residential crop straw burning. Carbonaceous aerosol species, including organic carbon (OC), elemental carbon (EC), WSOC and multiple saccharides as well as water-soluble potassium (K+) in PM2.5 (fine particulate matter with size less than 2.5 mu m) were measured. Chemical signatures of atmospheric aerosols in Beijing during winter and summer days with significant biomass burning influence were identified. Meanwhile, light absorption by WSOC was measured and quantitatively compared to EC at ground level. The results from this study indicated that levoglucosan exhibited consistently high concentrations (209 +/- 145 ng m(-3)) in winter. Ratios of levoglucosan/mannosan (L/M) and levoglucosan/galacosan (L/G) indicated that residential biofuel use is an important source of biomass burning aerosol in winter in Beijing. Light absorption coefficient per unit ambient WSOC mass calculated at 365 nm is approximately 1.54 +/- 0.16 m(2) g(-1) in winter and 0.73 +/- 0.15 m(2) g(-1) in summer. Biomass burning derived WSOC accounted for 23 +/- 7% and 16 +/- 7% of total WSOC mass, and contributed to 17 +/- 4% and 19 +/- 5% of total WSOC light absorption in winter and summer, respectively. It is noteworthy that, up to 30% of total WSOC light absorption was attributed to biomass burning in significant biomass-burning-impacted summer day. Near-surface light absorption (over the range 300-400 nm) by WSOC was about similar to 40% of that by EC in winter and similar to 25% in summer.

  • 45. Yu, Kuangyou
    et al.
    Xing, Zhenyu
    Huang, Xiaofeng
    Deng, Junjun
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Fang, Wenzheng
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Zhou, Jiabin
    Du, Ke
    Characterizing and sourcing ambient PM2.5 over key emission regions in China III: Carbon isotope based source apportionment of black carbon2018In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 177, p. 12-17Article in journal (Refereed)
    Abstract [en]

    Regional haze over China has severe implications for air quality and regional climate. To effectively combat these effects the high uncertainties regarding the emissions from different sources needs to be reduced. In this paper, which is the third in a series on the sources of PM2.5 in pollution hotspot regions of China, we focus on the sources of black carbon aerosols (BC), using carbon isotope signatures. Four-season samples were collected at two key locations: Beijing-Tianjin-Hebei (BTH, part of Northern China plain), and the Pearl River Delta (PAD). We find that that fossil fuel combustion was the predominant source of BC in both BTH and PRD regions, accounting for 75 +/- 5%. However, the contributions of what fossil fuel components were dominating differed significantly between BTH and PRD, and varied dramatically with seasons. Coal combustion is overall the all-important BC source in BTH, accounting for 46 +/- 12% of the BC in BTH, with the maximum value (62%) found in winter. In contrast for the PAD region, liquid fossil fuel combustion (e.g., oil, diesel, and gasoline) is the dominant source of BC, with an annual mean value of 41 +/- 15% and the maximum value of 55% found in winter. Region- and season-specific source apportionments are recommended to both accurately assess the climate impact of carbonaceous aerosol emissions and to effectively mitigate deteriorating air quality caused by carbonaceous aerosols.

  • 46. Zanatta, M.
    et al.
    Gysel, M.
    Bukowiecki, N.
    Mueller, T.
    Weingartner, E.
    Areskoug, Hans
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Fiebig, M.
    Yttri, K. E.
    Mihalopoulos, N.
    Kouvarakis, G.
    Beddows, D.
    Harrison, R. M.
    Cavalli, F.
    Putaud, J. P.
    Spindler, G.
    Wiedensohler, A.
    Alastuey, A.
    Pandolfi, M.
    Sellegri, K.
    Swietlicki, E.
    Jaffrezo, J. L.
    Baltensperger, U.
    Laj, P.
    A European aerosol phenomenology-5: Climatology of black carbon optical properties at 9 regional background sites across Europe2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 145, p. 346-364Article in journal (Refereed)
    Abstract [en]

    A reliable assessment of the optical properties of atmospheric black carbon is of crucial importance for an accurate estimation of radiative forcing. In this study we investigated the spatio-temporal variability of the mass absorption cross-section (MAC) of atmospheric black carbon, defined as light absorption coefficient (sigma(ap)) divided by elemental carbon mass concentration (m(EC)). sigma(ap) and m(EC) have been monitored at supersites of the ACTRIS network for a minimum period of one year. The 9 rural background sites considered in this study cover southern Scandinavia, central Europe and the Mediterranean. sigma(ap) was determined using filter based absorption photometers and m(EC) using a thermal-optical technique. Homogeneity of the data-set was ensured by harmonization of all involved methods and instruments during extensive intercomparison exercises at the European Center for Aerosol Calibration (ECAC). Annual mean values of sigma(ap) at a wavelength of 637 nm vary between 0.66 and 1.3 Mm(-1) in southern Scandinavia, 3.7-11 Mm(-1) in Central Europe and the British Isles, and 2.3-2.8 Mm(-1) in the Mediterranean. Annual mean values of mEC vary between 0.084 and 0.23 mu g m(-3) in southern Scandinavia, 0.28 -1.1 in Central Europe and the British Isles, and 0.22-0.26 in the Mediterranean. Both sigma(ap) and mEC in southern Scandinavia and Central Europe have a distinct seasonality with maxima during the cold season and minima during summer, whereas at the Mediterranean sites an opposite trend was observed. Annual mean MAC values were quite similar across all sites and the seasonal variability was small at most sites. Consequently, a MAC value of 10.0 m(2) g(-1) (geometric standard deviation = 133) at a wavelength of 637 nm can be considered to be representative of the mixed boundary layer at European background sites, where BC is expected to be internally mixed to a large extent. The observed spatial variability is rather small compared to the variability of values in previous literature, indicating that the harmonization efforts resulted in substantially increased precision of the reported MAC. However, absolute uncertainties of the reported MAC values remain as high as +/- 30-70% due to the lack of appropriate reference methods and calibration materials. The mass ratio between elemental carbon and non-light-absorbing matter was used as a proxy for the thickness of coatings around the BC cores, in order to assess the influence of the mixing state on the MAC of BC. Indeed, the MAC was found to increase with increasing values of the coating thickness proxy. This provides evidence that coatings do increase the MAC of atmospheric BC to some extent, which is commonly referred to as lensing effect.

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