Change search
Refine search result
12 51 - 84 of 84
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 51.
    Panagopoulos, Dimitri
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Lawrence Berkeley National Laboratory, United States.
    Jahnke, Annika
    Kierkegaard, Amelie
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Temperature Dependence of the Organic Carbon/Water Partition Ratios (K-oc) of Volatile Methylsiloxanes2017In: Environmental Science and Technology Letters, ISSN 2328-8930, Vol. 4, no 6, p. 240-245Article in journal (Refereed)
    Abstract [en]

    Knowing the temperature dependence of the organic carbon/water partition ratios (K-oc) of volatile methylsiloxanes (VMS) is required to understand their environmental fate. We measured the Koc of two linear VMS (IVMS), three cyclic VMS (cVMS), and six polychlorinated biphenyls (PCBs) at 25, 15, 10, and 5 degrees C and calculated their enthalpies and entropies of sorption to organic carbon (Delta H-oc and Delta S-oc, respectively). The Delta H-oc of VMS ranged from -79.2 to -45.8 kJ mol(-1) while the Delta H-oc of the PCBs ranged from -68.7 to -29.3 kJ mol(-1). Previously reported measurements of the enthalpy of phase change between octanol and water (Delta H-ow) for cVMS (11.3-68.8 kJ mol(-1)) differed substantially from our Delta H-oc measurements, even showing different signs (negative versus positive). Literature data of Delta H-oc and Delta H-ow for PCBs (-61 to -17 kJ mol(-1)) are closer to our measured values of Delta H-oc for the PCBs showing the same sign (negative) with differences within a factor of 2 in the majority of the cases. Comparison of all available data for PCBs and VMS indicated that there may be important differences between Delta H-oc and Delta H-ow, especially for the VMS. Therefore, assuming Delta H-oc equals Delta H-ow in environmental fate models may be a source of substantial error.

  • 52.
    Panagopoulos, Dimitri
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Jahnke, Annika
    Kierkegaard, Amelie
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Temperature dependence of the organic carbon/water partition ratios (KOC) of volatile methylsiloxanesIn: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851Article in journal (Refereed)
  • 53.
    Panagopoulos, Dimitri
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Kierkegaard, Amelie
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Jahnke, Annika
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Evaluating the salting-out effect on the organic carbon/water partition ratios (KOC and KDOC) of linear and cyclic volatile methylsiloxanes: Measurements and polyparameter linear free energy relationships2016In: Journal of Chemical and Engineering Data, ISSN 0021-9568, E-ISSN 1520-5134, Vol. 61, no 9, p. 3098-3108Article in journal (Refereed)
    Abstract [en]

    Dissolved inorganic salts influence the partitioning of organic chemicals between water and sorbents. We present new measurements of the salting-out constants (Ks) for partition ratios between water and organic carbon (KOC) and between water and dissolved organic carbon (KDOC) of three cyclic volatile methylsiloxanes (cVMS), two linear volatile methylsiloxanes (lVMS), three polychlorinated biphenyls (PCBs), and α-hexachlorocyclohexane (α-HCH). Ks, KOC, and KDOC were derived from volatilization rates of the chemicals from mixtures of water and organic carbon with varying concentrations of sodium chloride in a purge-and-trap system. KOC and KDOC values at different salinities were determined by fitting their values to reproduce observed volatilization rates using a fugacity-based multimedia model and assuming first-order kinetics for volatilization. The Ks values of cVMS and lVMS ranged from 0.16–0.76. The log KOC of cVMS and lVMS in fresh water interpolated from our measurements ranged from 5.20 to 7.36 and the log KDOC values from 5.04 to 6.72. Polyparameter linear free energy relationships (PP-LFERs) trained with data sets without measurements for siloxanes failed to accurately describe the log KOC and log KDOC of cVMS and lVMS. Including our measurements for cVMS and lVMS substantially improved the fit. PP-LFERs trained with data for Ks from solubility measurements do not describe our new measurements well regardless of whether or not they are included in the training set, which may reflect differences in the salting-out effect on partitioning to organic carbon versus on solubility.

  • 54.
    Panagopoulos, Dimitri
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    A critical assessment of the environmental fate of linear and cyclic volatile methylsiloxanes using multimedia fugacity modelsManuscript (preprint) (Other academic)
  • 55.
    Panagopoulos, Dimitri
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Lawrence Berkeley National Laboratory, USA.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    A critical assessment of the environmental fate of linear and cyclic volatile methylsiloxanes using multimedia fugacity models2018In: Environmental Science: Processes & Impacts, ISSN 2050-7887, E-ISSN 2050-7895, Vol. 20, no 1, p. 183-194Article in journal (Refereed)
    Abstract [en]

    We apply multimedia models to systematically evaluate the fate profile of cyclic volatile methyl siloxanes (VMS) D-4, D-5 and D-6, and the linear VMS L-4 and L-5 using recently reported measurements of their partition ratios between organic carbon and water (K-OC), their salting out constants (K-s), and their enthalpy of sorption to organic carbon (Delta H-OC). Our assessment follows a multi-stage strategy where the environmental fate of the chemicals is explored in generic regional models with increasing fidelity to the real system and in a region-specific model. Modeled emissions of VMS to air remained in air and were degraded or advected out of the system with overall residence times ranging from 2.4 to 2.5 days, while emissions to water resulted in accumulation in sediment and longer residence times ranging from 29.5 to 1120 days. When emitted to water the modeled residence times of VMS in the sediment exceeded the REACH criterion for persistence in freshwater sediments. Reported K-OC measurements for D-5 differ by 1 log unit, which results in a 500-day difference in the overall residence times calculated in the generic regional modeling. In the specific-region modeling assessment for Adventfjorden, Svalbard in Norway, the different K-OC measurements of D5 resulted in a 200-day difference in overall residence times. Model scenarios that examined combinations of previously published Delta H-OC or enthalpy of phase change between octanol and water (Delta H-OW) for D5 in combination with the range of the K-OC measurements resulted in 1100-days difference in overall residence times. Our results demonstrate that residence times of VMS in aquatic systems are highly sensitive to their degree of sorption to organic carbon, and that residence times of VMS likely exceed several persistence criteria and therefore they cannot be considered as non-persistent. Environmental significance Volatile methylsiloxanes (VMS) are a group of organosilicon chemicals that are used in personal care products and in the production of silicone polymers. VMS have been found at considerable levels in the air, in sediments and in aquatic organisms. We examine the fate of VMS using multimedia models in aquatic environments and we study their residence times in generic and specific environmental scenarios. Our calculations suggest that the residence times of VMS exceed several persistence criteria in aquatic environments and therefore they cannot be regarded as non-persistent chemicals.

  • 56.
    Persson, Linn
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Stockholm University, Stockholm Resilience Centre, Stockholm Environment Institute.
    Breitholtz, Magnus
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Cousins, Ian T.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    de Wit, Cynthia A.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    MacLeod, Matthew
    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).
    Confronting Unknown Planetary Boundary Threats from Chemical Pollution2013In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, no 22, p. 12619-12622Article in journal (Refereed)
    Abstract [en]

    Rockström et al. proposed a set of planetary boundaries that delimitate a “safe operating space for humanity”. One of the planetary boundaries is determined by “chemical pollution”, however no clear definition was provided. Here, we propose that there is no single chemical pollution planetary boundary, but rather that many planetary boundary issues governed by chemical pollution exist. We identify three conditions that must be simultaneously met for chemical pollution to pose a planetary boundary threat. We then discuss approaches to identify chemicals that could fulfill those conditions, and outline a proactive hazard identification strategy that considers long-range transport and the reversibility of chemical pollution.

  • 57. Qureshi, Asif
    et al.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hungerbuehler, Konrad
    Quantifying uncertainties in the global mass balance of mercury2011In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 25, p. GB4012-Article in journal (Refereed)
    Abstract [en]

    We quantify uncertainties in the global mass balance of mercury and identify research priorities to reduce these uncertainties. This is accomplished by developing a new spatially resolved global multimedia model (WorM(3)) that quantitatively describes the fate of mercury at a process level, and conducting an uncertainty analysis on its unit-world variant which computes similar global estimates. In our modeling approach, all mass transfer processes and reactions in ocean water, soil and vegetation, are represented as pseudo-first order; reactions in air are represented using the ratios of observed concentrations of mercury species. We use Monte Carlo analysis to estimate uncertainties in the unit-world modeled global mass balance of mercury and quantitatively identify the input parameters which contribute most to these uncertainties. A key finding is that uncertainties in input parameters that describe the rates of reduction and oxidation reactions in surface ocean contribute more than uncertainties in anthropogenic emissions to the total uncertainties in atmospheric concentration and depositional fluxes of mercury. More research should therefore be targeted toward understanding of these oceanic processes.

  • 58.
    Reppas-Chrysovitsinos, Efstathios
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Sobek, Anna
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacLeod, Matt
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Screening-level exposure-based prioritization to identify potential POPs, vPvBs and planetary boundary threats among Arctic contaminants2017In: Emerging Contaminants, ISSN 2405-6650, E-ISSN 2405-6642, Vol. 3, no 2, p. 85-94Article in journal (Refereed)
    Abstract [en]

    A report that reviews Arctic contaminants that are not currently regulated as persistent organic pollutants (POPs) under international treaties was recently published by the Arctic Monitoring and Assessment Programme (AMAP). We evaluated 464 individual chemicals mentioned in the AMAP report according to hazard profiles for POPs, very persistent and very bioaccumulative (vPvB) chemicals, and two novel and distinct hazard profiles we derived from the planetary boundary threat framework. The two planetary boundary threat profiles assign high priority to chemicals that will be mobile and poorly reversible environmental contaminants. Utilizing persistence as a proxy for poor reversibility, we defined two exposure-based hazard profiles; airborne persistent contaminants (APCs) and waterborne persistent contaminants (WPCs) that are potential planetary boundary threats. We used in silico estimates of physicochemical properties and multimedia models to calculate hazard metrics for persistence, bioaccumulation and long-range transport potential, then we synthesized this information into four exposure-based hazard scores of the potential of each AMAP chemical to fit each of the POP, vPvB, APC and WPC exposure-based hazard profiles. As an alternative to adopting a “bright line” score that represented cause for concern, we scored the AMAP chemicals by benchmarking against a reference set of 148 known and relatively well-studied contaminants and expressed their exposure-based hazard scores as percentile ranks against the scores of the reference set chemicals. Our results show that scores in the four exposure-based hazard profiles provide complementary information about the potential environmental exposure-based hazards of the AMAP chemicals. Our POP, vPvB, APC and WPC exposure-based hazard scores identify high priority chemicals for further study from among the AMAP contaminants.

  • 59.
    Reppas-Chrysovitsinos, Efstathios
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Sobek, Anna
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Exploring the Chemical Space Occupied by Non-ionizing Organic Chemicals with Hazardous Environmental Exposure PotentialManuscript (preprint) (Other academic)
  • 60.
    Reppas-Chrysovitsinos, Efstathios
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Sobek, Anna
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    In Silico Screening-Level Prioritization of 8468 Chemicals Produced in OECD Countries to Identify Potential Planetary Boundary Threats2018In: Bulletin of Environmental Contamination and Toxicology, ISSN 0007-4861, E-ISSN 1432-0800, Vol. 100, no 1, p. 134-146Article in journal (Refereed)
    Abstract [en]

    Legislation such as the Stockholm Convention and REACH aim to identify and regulate the production and use of chemicals that qualify as persistent organic pollutants (POPs) and very persistent and very bioaccumulative (vPvB) chemicals, respectively. Recently, a series of studies on planetary boundary threats proposed seven chemical hazard profiles that are distinct from the POP and vPvB profiles. We previously defined two exposure-based hazard profiles; airborne persistent contaminants (APCs) and waterborne persistent contaminants (WPCs) that correspond to two profiles of chemicals that are planetary boundary threats. Here, we extend our method to screen a database of chemicals consisting of 8648 substances produced within the OECD countries. We propose a new scoring scheme to disentangle the POP, vPvB, APC and WPC profiles by focusing on the spatial range of exposure potential, discuss the relationship between high exposure hazard and elemental composition of chemicals, and identify chemicals with high exposure hazard potential.

  • 61.
    Reppas-Chrysovitsinos, Efstathios
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Sobek, Anna
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    In silico Screening-Level Prioritization of 8648 Chemicals Produced in OECD Countries to Identify Potential Planetary Boundary ThreatsManuscript (preprint) (Other academic)
  • 62.
    Reppas-Chrysovitsinos, Efstathios
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Sobek, Anna
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Screening-level models to estimate partition ratios of organic chemicals between polymeric materials, air and water2016In: Environmental Science: Processes & Impacts, ISSN 2050-7887, E-ISSN 2050-7895, Vol. 18, no 6, p. 667-676Article in journal (Refereed)
    Abstract [en]

    Polymeric materials flowing through the technosphere are repositories of organic chemicals throughout their life cycle. Equilibrium partition ratios of organic chemicals between these materials and air (KMA) or water (KMW) are required for models of fate and transport, high-throughput exposure assessment and passive sampling. KMA and KMW have been measured for a growing number of chemical/ material combinations, but significant data gaps still exist. We assembled a database of 363 KMA and 910 KMW measurements for 446 individual compounds and nearly 40 individual polymers and biopolymers, collected from 29 studies. We used the EPI Suite and ABSOLV software packages to estimate physicochemical properties of the compounds and we employed an empirical correlation based on Trouton's rule to adjust the measured KMA and KMW values to a standard reference temperature of 298 K. Then, we used a thermodynamic triangle with Henry's law constant to calculate a complete set of 1273 KMA and KMW values. Using simple linear regression, we developed a suite of single parameter linear free energy relationship (spLFER) models to estimate KMA from the EPI Suite-estimated octanol-air partition ratio (KOA) and KMW from the EPI Suite-estimated octanol-water (KOW) partition ratio. Similarly, using multiple linear regression, we developed a set of polyparameter linear free energy relationship (ppLFER) models to estimate KMA and KMW from ABSOLV-estimated Abraham solvation parameters. We explored the two LFER approaches to investigate (1) their performance in estimating partition ratios, and (2) uncertainties associated with treating all different polymers as a single bulk polymeric material compartment. The models we have developed are suitable for screening assessments of the tendency for organic chemicals to be emitted from materials, and for use in multimedia models of the fate of organic chemicals in the indoor environment. In screening applications we recommend that K-MA and K-MW be modeled as 0.06 x K-OA and 0.06 x K-OW respectively, with an uncertainty range of a factor of 15.

  • 63. Rummel, Christoph D.
    et al.
    Escher, Beate
    Sandblom, Oskar
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Plassmann, Merle M.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Arp, Hans Peter H.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Jahnke, Annika
    Effects of Leachates from UV-Weathered Microplastic in Cell-Based Bioassays2019In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 53, no 15, p. 9214-9223Article in journal (Refereed)
    Abstract [en]

    Standard ecotoxicological testing of microplastic does not provide insight into the influence that environmental weathering by, e.g., UV light has on related effects. In this study, we leached chemicals from plastic into artificial seawater during simulated UV-induced weathering. We tested largely additive-free preproduction polyethylene, polyethylene terephthalate, polypropylene, and polystyrene and two types of plastic obtained from electronic equipment as positive controls. Leachates were concentrated by solid-phase extraction and dosed into cell-based bioassays that cover (i) cytotoxicity; (ii) activation of metabolic enzymes via binding to the arylhydrocarbon receptor (AhR) and the peroxisome proliferator-activated receptor (PPAR gamma); (iii) specific, receptor-mediated effects (estrogenicity, ER alpha); and (iv) adaptive response to oxidative stress (AREc32). LC-HRMS analysis was used to identify possible chain-scission products of polymer degradation, which were then tested in AREc32 and PPAR gamma. Explicit activation of all assays by the positive controls provided proof-of-concept of the experimental setup to demonstrate effects of chemicals liberated during weathering. All plastic leachates activated the oxidative stress response, in most cases with increased induction by UV-treated samples compared to dark controls. For PPAR gamma, polyethylene-specific effects were partially explained by the detected dicarboxylic acids. Since the preproduction plastic showed low effects often in the range of the blanks future studies should investigate implications of weathering on end consumer products containing additives.

  • 64.
    Rummel, Christoph Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Adolfsson-Erici, Margaretha
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Jahnke, Annika
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    No measurable cleaning of polychlorinated biphenyls from Rainbow Trout in a 9 week depuration study with dietary exposure to 40% polyethylene microspheres2016In: Environmental Science: Processes & Impacts, ISSN 2050-7887, E-ISSN 2050-7895, Vol. 18, no 7, p. 788-795Article in journal (Refereed)
    Abstract [en]

    Persistent hydrophobic chemicals sorbed to plastic can be transferred to fish and other aquatic organisms upon ingestion. However, ingestion of plastic could also lead to enhanced elimination of these chemicals if the plastic is less contaminated than the fish. Here, we attempted to measure the influence of ingestion of uncontaminated polyethylene microspheres on the depuration rates of polychlorinated biphenyls (PCBs) in an in vivo fish feeding experiment. Rainbow trout were given feed contaminated with PCBs for two consecutive days, then clean feed for three days to allow for egestion of the contaminated food. A control group of fish were then fed ordinary food pellets and a treatment group were fed pellets that additionally contained 40% by weight polyethylene microspheres. Condition factors and growth rates in both groups were similar, indicating no negative effect of the plastic microspheres on the nutritional status of the fish. Fish were sampled after zero, three, six and nine weeks, homogenized, solvent-extracted and analyzed by GC/MS. PCB concentrations declined in both groups at a rate consistent with growth dilution. There was no significant difference in the elimination rate constants between the control and treatment group, indicating that ingestion of uncontaminated plastic did not cause a measurable enhancement of depuration of PCBs by the fish in this study.

  • 65.
    Safron, Andreas
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Strandell, Michael
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Kierkegaard, Amelie
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Macleod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Rate Constants and Activation Energies for Gas-Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical2015In: International Journal of Chemical Kinetics, ISSN 0538-8066, E-ISSN 1097-4601, Vol. 47, no 7, p. 420-428Article in journal (Refereed)
    Abstract [en]

    Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second-order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D-4), decamethylcyclopentasiloxane (D-5), and dodecamethylcyclohexasiloxane (D-6) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140-mL gas-phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D-4 and D-5 with the OH radical are 1.9 x 10(-12) (95% confidence interval (CI): (1.7-2.2) x 10(-12)) and 2.6 x 10(-12) (CI: (2.3-2.9) x 10(-12)) cm(3) molecule(-1) s(-1), respectively, which are 1.9x and 1.7x faster than previous measurements. Our measured rate constant for D-6 is 2.8 x 10(-12) (CI: (2.5-3.2) x 10(-12)) cm(3) molecule(-1) s(-1) and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D-5 were 33% higher than for D-4 (CI: 30-37%), whereas the rates for D-6 were only 8% higher than for D-5 (CI: 5-10%). The activation energies of the reactions of D-4, D-5, and D-6 with OH were not statistically different and had a value of 4300 +/- 2800 J/mol.

  • 66. Shunthirasingham, Chubashini
    et al.
    Wania, Frank
    MacLeod, Matthew
    Institute for Chemical and Bioengineering, Zürich, Schweiz.
    Lei, Ying Duan
    Quinn, Christina L.
    Zhang, Xianming
    Scheringer, Martin
    Wegmann, Fabio
    Hungerbuhler, Konrad
    Ivemeyer, Silvia
    Heil, Fritz
    Klocke, Peter
    Pacepavicius, Grazina
    Alaee, Mehran
    Mountain Cold-Trapping Increases Transfer of Persistent Organic Pollutants from Atmosphere to Cows’ Milk2013In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, no 16, p. 9175-9181Article in journal (Refereed)
    Abstract [en]

    Concentrations of long-lived organic contaminants in snow, soil, lake water, and vegetation have been observed to increase with altitude along mountain slopes. Such enrichment, called “mountain cold-trapping”, is attributed to a transition from the atmospheric gas phase to particles, rain droplets, snowflakes, and Earth’s surface at the lower temperatures prevailing at higher elevations. Milk sampled repeatedly from cows that had grazed at three different altitudes in Switzerland during one summer was analyzed for a range of persistent organic pollutants. Mountain cold-trapping significantly increased air-to-milk transfer factors of most analytes. As a result, the milk of cows grazing at higher altitudes was more contaminated with substances that have regionally uniform air concentrations (hexachlorobenzene, α-hexachlorocyclohexane, endosulfan sulfate). For substances that have sources, and therefore higher air concentrations, at lower altitudes (polychlorinated biphenyls, γ-hexachlorocyclohexane), alpine milk has lower concentrations, but not as low as would be expected without mountain cold-trapping. Differences in the elevational gradients in soil concentrations and air-to-milk transfer factors highlight that cold-trapping of POPs in pastures is mostly due to increased gas-phase deposition as a result of lower temperatures causing higher uptake capacity of plant foliage, whereas cold-trapping in soils more strongly depends on wet and dry particle deposition. Climatic influences on air-to-milk transfer of POPs needs to be accounted for when using contamination of milk lipids to infer contamination of the atmosphere.

  • 67. Wang, Zhanyun
    et al.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Cousins, Ian
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Scheringer, Martin
    Hungerbuehler, Konrad
    Using COSMOtherm to predict physicochemical properties of poly- and perfluorinated alkyl substances (PFASs)2011In: Environmental Chemistry, ISSN 1448-2517, E-ISSN 1449-8979, Vol. 8, no 4, p. 389-398Article in journal (Refereed)
    Abstract [en]

    Recently, there has been concern about the presence of poly- and perfluorinated alkyl substances (PFASs) in the environment, biota and humans. However, lack of physicochemical data has limited the application of environmental fate models to understand the environmental distribution and ultimate fate of PFASs. We employ the COSMOtherm model to estimate physicochemical properties for 130 individual PFASs, namely perfluoroalkyl acids (including branched isomers for C(4)-C(8) perfluorocarboxylic acids), their precursors and some important intermediates. The estimated physicochemical properties are interpreted using structure-property relationships and rationalised with insight into molecular interactions. Within a homologous series of linear PFASs with the same functional group, both air-water and octanol-water partition coefficient increase with increasing perfluorinated chain length, likely due to increasing molecular volume. For PFASs with the same perfluorinated chain length but different functional groups, the ability of the functional group to form hydrogen bonds strongly influences the chemicals' partitioning behaviour. The partitioning behaviour of all theoretically possible branched isomers can vary considerably; however, the predominant isopropyl and monomethyl branched isomers in technical mixtures have similar properties as their linear counterparts (differences below 0.5 log units). Our property estimates provide a basis for further environmental modelling, but with some caveats and limitations.

  • 68. Wang, Zhanyun
    et al.
    Scheringer, Martin
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bogdal, Christian
    Mueller, Claudia E.
    Gerecke, Andreas C.
    Hungerbuehler, Konrad
    Atmospheric fate of poly- and perfluorinated alkyl substances (PFASs): II. Emission source strength in summer in Zurich, Switzerland2012In: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 169, p. 204-209Article in journal (Refereed)
    Abstract [en]

    Fluorotelomer alcohols (FTOHs) and perfluorooctane sulfonamides (FOSAs) are present in consumer products and are semi-volatile precursors of persistent perfluoroallcyl acids (PFAAs). The high variability of levels of FrOHs and FOSAs in products makes it difficult to derive FTOH- and FOSA-emissions from urban areas based on emission factors. Here we used a multimedia mass balance model that describes the day-night cycle of semi-volatile organic chemicals in air to interpret measurements of 8:2 FTOH, 10:2 FTOH, MeFOSA and EtFOSA from a sampling campaign in summer 2010 in Zurich, Switzerland. The estimated emission source strength of the four substances follows the sequence: 8:2 FTOH (2.6 g/h) > 10:2 FTOH (0.75 g/h) > MeFOSA (0.08 g/h) > EtFOSA (0.05 g/h). There is no FTOHs- or FOSAs-related industry in Zurich. Accordingly, our estimates are representative of diffusive emissions during use and disposal of consumer products, and describe noticeable sources of these PFASs to the environment.

  • 69. Woehrnschimmel, Henry
    et al.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hungerbuhler, Konrad
    Emissions, Fate and Transport of Persistent Organic Pollutants to the Arctic in a Changing Global Climate2013In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, no 5, p. 2323-2330Article in journal (Refereed)
    Abstract [en]

    Climate change is expected to alter patterns of human economic activity and the associated emissions of chemicals, and also to affect the transport and fate of persistent organic pollutants (POPs). Here, we use a global-scale multimedia chemical fate model to analyze and quantify the impact of climate change on emissions and fate of POPs, and their transport to the Arctic. First, climate change effects under the SRES-A2 scenario are illustrated using case-studies for two well-characterized POPs, PCB 153, and alpha-HCH. Then, we model the combined impact of altered emission patterns and climatic conditions on environmental concentrations of potential future-use substances with a broad range of chemical properties. Starting from base-case generic emission scenarios, we postulate changes in emission patterns that may occur in response to climate change: enhanced usage of industrial chemicals in an ice-free Arctic, and intensified application of agrochemicals due to higher crop production and poleward expansion of potential arable land. We find both increases and decreases in concentrations of POP-like chemicals in the Arctic in the climate change scenario compared to the base-case climate. During the phase of ongoing primary emissions, modeled increases in Arctic contamination are up to a factor of 2 in air and water, and are driven mostly by changes in emission patterns. After phase-out, increases are up to a factor of 2 in air and 4 in water, and are mostly attributable to changes in transport and fate of chemicals under the climate change scenario.

  • 70. Woehrnschimmel, Henry
    et al.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hungerbuhler, Konrad
    Global multimedia source-receptor relationships for persistent organic pollutants during use and after phase-out2012In: Atmospheric Pollution Research, ISSN 1309-1042, Vol. 3, no 4, p. 392-398Article in journal (Refereed)
    Abstract [en]

    Chemicals that are persistent in the atmosphere can be transported long distances and across international boundaries. Therefore, information about the fraction of local versus imported air pollution is required to formulate regulations aimed at controlling pollutant levels. The objective of this work is to illustrate the capabilities of a dynamic global-scale multimedia model to calculate source-receptor relationships for persistent organic pollutants that cycle between air, water, soil and vegetation in the global environment. As exemplary case studies, we present model calculations of time-evolving source-receptor relationships for PCB28, PCB153, alpha-HCH and beta-HCH over the duration of their usage, phase-out and a post-ban period. Our analysis is geographically explicit, and elucidates the role of primary versus secondary sources in controlling the levels of air pollution. Our case studies consider source-receptor relationships between the four regions defined by the Convention on Long-range Transboundary Air Pollution Task Force on Hemispheric Transport of Air Pollution, as well as the Arctic as a remote receptor region. We find source-receptor relationships that are highly variable over time, and between different regions and chemicals. Air pollution by PCBs in North America and Europe is consistently dominated by local emissions, whereas in East-and South-Asia extra-regional sources are sometimes major contributors. Emissions of alpha-HCH peak at different times in the four regions, which leads to a phase of high self-pollution in each region, and periods when pollution enters mainly from outside. Compared to alpha-HCH, air pollution with the less volatile and more persistent beta-HCH is more strongly determined by secondary emissions near source areas throughout its use history. PCB concentrations in Arctic air are dominated by emissions transported from North America and Europe from 1930 to 2080, whereas for HCHs each of the source regions contributes a high share at some point between 1950 and 2050. (C) Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License.

  • 71. Woehrnschimmel, Henry
    et al.
    Tay, Pascal
    von Waldow, Harald
    Hung, Hayley
    Li, Yi-Fan
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hungerbuhler, Konrad
    Comparative Assessment of the Global Fate of alpha- and beta-Hexachlorocyclohexane before and after Phase-Out2012In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 46, no 4, p. 2047-2054Article in journal (Refereed)
    Abstract [en]

    Technical hexachlorocyclohexane (HCH) was one of the most widely used pesticides during the 20th century. Although production and use were phased-out during the 1990s, two of its major components, alpha- and beta-HCH, are still ubiquitous in the environment. Here, we have collected and analyzed data on concentrations of alpha- and beta-HCH in the atmosphere and oceans, including spatial and temporal trends and seasonalities. We apply a global fate and transport model to both isomers over the period 1950 to 2050 to rationalize current levels and trends at remote locations with estimated emissions and to forecast into the near future. Our model results indicate that secondary emissions from soils and oceans are currently controlling the observed rates of decline in the atmosphere. beta-HCH is declining more slowly than alpha-HCH due to its higher persistence, and we hypothesize that it will eventually become the predominant isomer of HCH in the environment. The model reproduces over 70% of measured concentrations of alpha-HCH in air and ocean water within factors of 3 and 5, respectively, and over 70% of measured concentrations of beta-HCH within factors of 8 and 20, respectively. The model results are only weakly sensitive to climate change-induced trends in Arctic sea-ice cover and temperature.

  • 72.
    Wong, Fiona
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Cousins, Ian T.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bounding uncertainties in intrinsic human elimination half-lives and intake of polybrominated diphenyl ethers in the North American population2013In: Environment International, ISSN 0160-4120, E-ISSN 1873-6750, Vol. 59, p. 168-174Article in journal (Refereed)
    Abstract [en]

    We examine the balance between intake, intrinsic elimination half-lives and human body burdens measured in biomonitoring for polybrominated diphenyl ethers (PBDEs) in the North American population using the population-level pharmacokinetic model developed by Ritter et al. (2011). Empirical data are collected from two studies that made total intake estimates for the North American population for the years 2004 and 2005, and eight biomonitoring studies for the years 1992 to 2009. We assume intake of PBDEs increased exponentially to a peak in 2004, and has since exponentially declined. The model is fitted to the empirical PBDE intake and biomonitoring data on PBDE body burden using a least-square optimization method by adjusting the intake in 2004 and 2038, and the intrinsic elimination rate constants, which can be expressed as equivalent half-lives. We. fit the model in two types of scenarios using different combinations of PBDE intake estimates and biomonitoring data. Our modeling results indicate that there is an inconsistency between the PBDE intake estimates and the biomonitoring data, and that the inconsistency is likely due to underestimation of population-level intake. More efforts are needed to better characterize intake rates and identify potentially-unrecognized exposure pathways. Additional age-stratified biomonitoring data, and time trends of PBDE intakes would better constrain the model and provide an improved estimation of the intrinsic elimination half-lives.

  • 73.
    Wong, Fiona
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Mueller, Jochen F.
    Cousins, Ian T.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Enhanced Elimination of Perfluorooctane Sulfonic Acid by Menstruating Women: Evidence from Population-Based Pharmacokinetic Modeling2014In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, no 15, p. 8807-8814Article in journal (Refereed)
    Abstract [en]

    Human biomonitoring studies have shown that concentrations of perfluorooctane sulfonic acid (PFOS) in men are higher than in women. We investigate sex differences in elimination of PFOS by fitting a population-based pharmacokinetic model to six cross-sectional data sets from 1999 to 2012 from the US National Health and Nutrition Examination Survey (NHANES) and derive human first-order elimination rate constants (k(E)) and corresponding elimination half-lives (t(1/2)) for PFOS, where t(1/2) = In 2/k(E). We use a modified version of the Ritter population-based pharmacokinetic model and derive elimination rate constants separately for men and women. The model accounts for population-average lifetime changes in PFOS intake, body weight, and menstruation rate. We compare the model-derived elimination rate constant for hypothetical nonmenstruating women to the elimination rate constant for men and women when menstruation is included as a loss process to evaluate the hypothesis that loss of PFOS by menstruation is an important process for women. The modeled elimination half-life for men is 4.7 years, and the modeled elimination half-life for women when excluding losses from menstruation is 3.7 years. The elimination half-life for women when menstruation is included in the model is 4.0 years. Thus, menstruation accounts for 3096 of the discrepancy in elimination of PFOS between men and women. The remaining discrepancy is likely due to other sex-specific elimination routes that are not considered in our modeling.

  • 74.
    Wong, Fiona
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Mueller, Jochen F.
    Cousins, Ian T.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Response to Comment on Enhanced Elimination of Perfluorooctane Sulfonic Acid by Menstruating Women: Evidence from Population-based Pharmacokinetic Modeling2015In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, no 9, p. 5838-5839Article in journal (Refereed)
  • 75.
    Xiao, Ruiyang
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Adolfsson-Erici, Margaretha
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Åkerman, Gun
    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).
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    A BENCHMARKING METHOD TO MEASURE DIETARY ABSORPTION EFFICIENCY OF CHEMICALS BY FISH2013In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 32, no 12, p. 2695-2700Article in journal (Refereed)
    Abstract [en]

    Understanding the dietary absorption efficiency of chemicals in the gastrointestinal tract of fish is important from both a scientific and a regulatory point of view. However, reported fish absorption efficiencies for well-studied chemicals are highly variable. In the present study, the authors developed and exploited an internal chemical benchmarking method that has the potential to reduce uncertainty and variability and, thus, to improve the precision of measurements of fish absorption efficiency. The authors applied the benchmarking method to measure the gross absorption efficiency for 15 chemicals with a wide range of physicochemical properties and structures. They selected 2,2,5,6-tetrachlorobiphenyl (PCB53) and decabromodiphenyl ethane as absorbable and nonabsorbable benchmarks, respectively. Quantities of chemicals determined in fish were benchmarked to the fraction of PCB53 recovered in fish, and quantities of chemicals determined in feces were benchmarked to the fraction of decabromodiphenyl ethane recovered in feces. The performance of the benchmarking procedure was evaluated based on the recovery of the test chemicals and precision of absorption efficiency from repeated tests. Benchmarking did not improve the precision of the measurements; after benchmarking, however, the median recovery for 15 chemicals was 106%, and variability of recoveries was reduced compared with before benchmarking, suggesting that benchmarking could account for incomplete extraction of chemical in fish and incomplete collection of feces from different tests. Environ Toxicol Chem 2013;32:2695-2700.

  • 76.
    Xiao, Ruiyang
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Central South University, China.
    Arnot, Jon A.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Towards an improved understanding of processes controlling absorption efficiency and biomagnification of organic chemicals by fish2015In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 138, p. 89-95Article in journal (Refereed)
    Abstract [en]

    Dietary exposure is considered the dominant pathway for fish exposed to persistent, hydrophobic chemicals in the environment. Here we present a dynamic, fugacity-based three-compartment bioaccumulation model that describes the fish body as one compartment and the gastrointestinal tract (GIT) as two compartments. The model simulates uptake from the GIT by passive diffusion and micelle-mediated diffusion, and chemical degradation in the fish and the GIT compartments. We applied the model to a consistent measured dietary uptake and depuration dataset for rainbow trout (n = 215) that is comprised of chlorinated benzenes, biphenyls, dioxins, diphenyl ethers, and polycyclic aromatic hydrocarbons (PAHs). Model performance relative to the measured data is statistically similar regardless of whether micelle-mediated diffusion is included; however, there are considerable uncertainties in modeling this process. When degradation in the GIT is assumed to be negligible, modeled chemical elimination rates are similar to measured rates; however, predicted concentrations of the PAHs are consistently higher than measurements by up to a factor of 20. Introducing a kinetic limit on chemical transport from the fish compartment to the GIT and increasing the rate constant for degradation of PAHs in tissues of the liver and/or GIT are required to achieve good agreement between the modelled and measured concentrations for PAHs. Our results indicate that the apparent low absorption efficiency of PAHs relative to the chemicals with similar hydrophobicity is attributable to biotransformation in the liver and/or the GIT. Our results provide process-level insights about controls on the extent of bioaccumulation of chemicals.

  • 77. Xiao, Ruiyang
    et al.
    Zammit, Ian
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Wei, Zongsu
    Hu, Wei-Ping
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Spinney, Richard
    Kinetics and Mechanism of the Oxidation of Cyclic Methylsiloxanes by Hydroxyl Radical in the Gas Phase: An Experimental and Theoretical Study2015In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, no 22, p. 13322-13330Article in journal (Refereed)
    Abstract [en]

    The ubiquitous presence of cyclic volatile methylsiloxanes (cVMS) in the global atmosphere has recently raised environmental concern. In order to assess the persistence and long-range transport potential of cVMS, their second-order rate constants (k) for reactions with hydroxyl radical ((OH)-O-center dot) in the gas phase are needed. We experimentally and theoretically investigated the kinetics and mechanism of (OH)-O-center dot oxidation of a series of cVMS, hexamethylcyclotrisiloxane (D-3), octamethycyclotetrasiloxane (D-4), and decamethycyclopentasiloxane (D-5). Experimentally, we measured k values for D-3, D-4, and D-s -with (OH)-O-center dot in a gas-phase reaction chamber. The Arrhenius activation energies for these reactions in the temperature range from 313 to 353 K were small (-2.92 to 0.79 kcal.mol(-1)), indicating a weak temperature dependence. We also calculated the thermodynamic and kinetic behaviors for reactions at the M06-2X/6-311++G**//M06-2X/6-31+G** level of theory over a wider temperature range of 238-358 K that encompasses temperatures in the troposphere. The calculated Arrhenius activation energies range from -2.71 to -1.64 kcal-mol(-1), also exhibiting weak temperature dependence. The measured k values were approximately an order of magnitude higher than the theoretical values but have the same trend with increasing size of the siloxane ring. The calculated energy barriers for H-atom abstraction at different positions were similar, which provides theoretical support for extrapolating k for other cyclic siloxanes from the number of abstractable hydrogens.

  • 78.
    Yuan, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bogdal, Christian
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Berger, Urs
    Gao, Wei
    Wang, Yawei
    de Wit, Cynthia A.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Deconvolution of Soft Ionization Mass Spectra of Chlorinated Paraffins To Resolve Congener Groups2016In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 18, p. 8980-8988Article in journal (Refereed)
    Abstract [en]

    We describe and illustrate a three-step data-processing approach that enables individual congener groups of chlorinated-paraffins (CPs) to be resolved in mass spectra obtained from either-of two soft ionization methods: electron capture negative-ionization mass spectrometry (ECNI-MS) or atmospheric pressure chemical ionization mass spectrometry (APCI-MS). In the first step, general fragmentation pathways of CPs are deduced from analysis of mass spectra of individual CP congeners. In the-Second step, all possible fragment ions in the general fragmentation pathways of CPs with 10 to 20 carbon atoms are enumerated and compared to mass spectra of CP mixture standards, and a deconvolution algorithm is applied to identify fragment ions that are actually observed. In the third step, isotope permutations of the observed fragment ions are calculated and used to identify isobaric overlaps, so that mass intensities of indivichial CP congener groups can be deconvolved from the unresolved isobaric ion signal intensities in mass spectra. For a specific instrument; the three steps only need to be done once to enable deconvolution of CPs in unknown samples. This approach enables congener group-level resolution of CP mixtures in environmental samples, and: it opens up the possibility, for quantification of congener group.

  • 79.
    Yuan, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bogdal, Christian
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    de Wit, Cynthia
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Modelling isotopic peak distributions of chlorinated paraffins homologue groups in high resolution mass spectrometry in soft ionization modes2015Conference paper (Other academic)
  • 80.
    Yuan, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bogdal, Christian
    Berger, Urs
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Gebbink, Wouter A.
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    de Wit, Cynthia A.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Quantifying Short-Chain Chlorinated Paraffin Congener Groups2017In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, no 18, p. 10633-10641Article in journal (Refereed)
    Abstract [en]

    Accurate quantification of short-chain chlorinated paraffins (SCCPs) poses an exceptional challenge to analytical chemists. SCCPs are complex mixtures of chlorinated alkanes with variable chain length and chlorination level; congeners with a fixed chain length (n) and number of chlorines (m) are referred to as a congener group CnClm Recently, we resolved individual CnClm by mathematically deconvolving soft ionization high-resolution mass spectra of SCCP mixtures. Here we extend the method to quantifying CnClm by introducing CnClm specific response factors (RFs) that are calculated from 17 SCCP chain-length standards with a single carbon chain length and variable chlorination level. The signal pattern of each standard is measured on APCI-QTOF-MS. RFs of each CnClm are obtained by pairwise optimization of the normal distribution's fit to the signal patterns of the 17 chain-length standards. The method was verified by quantifying SCCP technical mixtures and spiked environmental samples with accuracies of 82-123% and 76-109%, respectively. The absolute differences between calculated and manufacturer-reported chlorination degrees were 0.9 to 1.0%Cl for SCCP mixtures of 49-71%Cl. The quantification method has been replicated with ECNI magnetic sector MS and ECNI-Q:Orbitrap-MS. CnClm concentrations determined with the three instruments were highly correlated (R-2 > 0.90) with each other.

  • 81.
    Yuan, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Muir, Derek
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Methods for trace analysis of short-, medium-, and long-chain chlorinated paraffins: Critical review and recommendations2019In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 1074, p. 16-32Article, review/survey (Refereed)
    Abstract [en]

    Many methods for quantifying chlorinated paraffins (CPs) yield only a total concentration of the mixture as a single value. With appropriate analytical instrumentation and quantification methods, more reliable and detailed analysis can be performed by quantifying total concentrations of short-, medium-, and longchain CPs (SCCPs, MCCPs, and LCCPs), and in the current optimal situation by quantifying individual carbon-chlorine congener groups (CnClm). Sample extraction and clean-up methods for other persistent organochlorines that have been adapted for recovery of CPs must be applied prior to quantification with appropriate quality assurance and quality control to ensure applicability of the methods for SCCPs, MCCPs, and LCCPs. Part critical review, part tutorial, and part perspective, this paper provides practical guidance to analytical chemists who are interested in establishing a method for analysis of CPs in their lab facilities using commercial reference standards, or for expanding existing analysis of total CPs or SCCPs to analysis of SCCPs, MCCPs, and LCCPs, or to analysis of CnClm congener groups.

  • 82.
    Zou, Hongyan
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    MacLeod, Matthew
    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).
    Evaluation of the potential of benchmarking to facilitate the measurement of chemical persistence in lakes2014In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 95, p. 301-309Article in journal (Refereed)
    Abstract [en]

    The persistence of chemicals in the environment is rarely measured in the field due to a paucity of suitable methods. Here we explore the potential of chemical benchmarking to facilitate the measurement of persistence in lake systems using a multimedia chemical fate model. The model results show that persistence in a lake can be assessed by quantifying the ratio of test chemical and benchmark chemical at as few as two locations: the point of emission and the outlet of the lake. Appropriate selection of benchmark chemicals also allows pseudo-first-order rate constants for physical removal processes such as volatilization and sediment burial to be quantified. We use the model to explore how the maximum persistence that can be measured in a particular lake depends on the partitioning properties of the test chemical of interest and the characteristics of the lake. Our model experiments demonstrate that combining benchmarking techniques with good experimental design and sensitive environmental analytical chemistry may open new opportunities for quantifying chemical persistence, particularly for relatively slowly degradable chemicals for which current methods do not perform well.

  • 83.
    Zou, Hongyan
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Radke, Michael
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Kierkegaard, Amelie
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    McLachlan, Michael S.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Using Chemical Benchmarking to Determine the Persistence of Chemicals in a Swedish Lake2015In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, no 3, p. 1646-1653Article in journal (Refereed)
    Abstract [en]

    It is challenging to measure the persistence of chemicals under field conditions. In this work, two approaches for measuring persistence in the field were compared: the chemical mass balance approach, and a novel chemical benchmarking approach. Ten pharmaceuticals, an X-ray contrast agent, and an artificial sweetener were studied in a Swedish lake. Acesulfame K was selected as a benchmark to quantify persistence using the chemical benchmarking approach. The 95% confidence intervals of the half-life for transformation in the lake system ranged from 780-5700 days for carbamazepine to <1-2 days for ketoprofen. The persistence estimates obtained using the benchmarking approach agreed well with those from the mass balance approach (1-21% difference), indicating that chemical benchmarking can be a valid and useful method to measure the persistence of chemicals under field conditions. Compared to the mass balance approach, the benchmarking approach partially or completely eliminates the need to quantify mass flow of chemicals, so it is particularly advantageous when the quantification of mass flow of chemicals is difficult. Furthermore, the benchmarking approach allows for ready comparison and ranking of the persistence of different chemicals.

  • 84. Åberg, Annika
    et al.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Wiberg, Karin
    Performance of the CalTOX fate and exposure model in a case study for a dioxin-contaminated site2015In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 22, no 11, p. 8719-8727Article in journal (Refereed)
    Abstract [en]

    Soil with high levels of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) is found at contaminated sites all over the world. Transfer of PCDD/Fs from contaminated soil to the food chain could lead to elevated human exposure. As a complement to available monitoring data, multimedia fate and exposure modeling can be applied to support risk assessment of sites with PCDD/F contaminated soil. In this study, we evaluated the performance of the CalTOX fate and exposure model for 2,3,7,8-substituted PCDD/Fs against measured concentrations in air, soil, grass, carrots, potatoes, milk, meat, and eggs from a contaminated site in northern Sweden. The calculated total toxic equivalent (TEQ) concentrations agree with measurements within a factor of 10 for all exposure media but one. Results for individual congeners demonstrated that the model did not always perform well at describing key processes that mobilize PCDD/Fs out of soils, such as transfer into root crops and ingestion of soil by chickens. Uncertainty in only a small subset of input parameters affects the model output. Improved information and models describing transfer of soil particles onto leafy vegetation by rain splash and biotransfer factors for PCDD/Fs to milk, meat, and eggs are particular research needs to reduce uncertainties in model-based assessments.

12 51 - 84 of 84
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf