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  • 1.
    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.

  • 2.
    Ekström, S
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Alsberg, T
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hultberg, M.
    Nozière, B
    Nilsson, D
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Artaxo, P.
    “Super-CCN”: A contribution of bio-organisms to cloud formation in Earth’s atmosphere2008In: International Global Atmospheric Chemistry Project (IGAC) 2008: 7-12 September, Annecy, France, 2008Conference paper (Refereed)
  • 3.
    Ekström, S
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Nozière, B
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hansson, H
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    The CCN Properties of 2-Methyltetrols and C3-C6 Polyols2008In: ICCP 2008: August 28-30, Cluj-Napoca, Romania, 2008Conference paper (Refereed)
  • 4.
    Ekström, Sanna
    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).
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hultberg, Malin
    Magnér, Jorgen
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Nilsson, E. Douglas
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Artaxo, Paulo
    Of Bacteria and clouds: when microbial substances trigger cloud formation in Earth’s atmosphere2008In: American Geophysical Union Fall Meeting 2008, 2008Conference paper (Refereed)
    Abstract [en]

    This presentation reports the discovery that substances produced by microorganisms might trigger the formation of cloud in the atmosphere, at least under certain conditions.

    The Cloud Condensation Nuclei (CCN) efficiency of substances produced by microorganisms (bacteria, fungi, micro-algae …) that are common at Earth’s surface and in the oceans were studied. Their Köhler curves were determined experimentally by surface tension and osmometry measurements and found to have much lower critical supersaturations than any material studied so far, including inorganic salts.

    The presence of these substances was evidenced in aerosols from four different origins (coastal, marine, temperate forest, and Amazonian forest) by LC/MS/MS analyses and by their unique signature on the surface tension. These substances lowered the surface tension of the aerosols below 40 mN/m, allowing them to be activated into cloud droplets before inorganic particles.

    Microorganisms would thus be able to control cloud formation in Earth’s atmosphere under certain conditions. This would explain many previous observations such as correlations between algae bloom and cloud cover. Most importantly, this work identifies a potentially important component of Earth’s hydrological cycle and a new direct link between biosphere and climate.

  • 5.
    Ekström, Sanna
    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).
    Hansson, Hans Christen
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    First direct measurements of the CCN properties of 2-methyltetrols and polyols2008In: Geophysical Research Abstracts, 2008Conference paper (Refereed)
    Abstract [en]

    2-methyltetrols and polyols have received a lot of attention in recent years. 2-methyltetrols have been found in aerosols in various regions are believed to be formed by the oxidation of isoprene. Polyols are produced by fungi and have been measured

    in large concentrations in aerosols. The main reason of interest of both 2-methyltetrols and polyols as efficient cloud condensation nuclei (CCN) is due to their high solubility.

    This presentation will report for the first time the experimental determination of complete Köhler curves for 2-methyltetrols (2-methylerythritol and 2-methylthreitol), C3 to C6 polyols (glycerol, erythritol, arabitol, and mannitol), and for comparison their

    analogue di-acids (malonic acid, succinic acid and, adipic acid). The original Köhler equations were determined from osmolality and tensiometry measurements of the compounds both in water and salt solutions (sodium chloride and ammonium sulphate).

    The results indicate that the polyols generally have similar CCN properties as the dicarboxylic acids. The critical supersaturation for aerosol particles with a 30 nm radius were: 2-methyltetrol; 0.68%, mannitol; 0.62%, arabitol; 0.60%, 2-methylerythritol;

    0.57%, erythritol; 0.56%, glycerol; 0.53%, adipic acid; 0.52%, succinic acid; 0.49%, and malonic acid; 0.44%. Mixtures of salts had lower critical supersaturation than water solutions, especially for the polyols. One exception was 2-methylerythritol, which interestingly was less efficient as CCN in salt solutions.

    The CCN efficiency of the polyols is believed to result mostly from their large water affinity, enforcing the Raoult effect, while organic acids lower the Kelvin effect. The very large solubility of polyols compared to the di-acids mean that they could positive effect in the initial phase of the droplet growth while the di-acids cannot. 2-methyltetrols were found to have both a Kelvin and a Raoult effect.

    In addition, these results establish for the first time that the 3-dimensional structure of molecules can have an effect on their CCN properties. The two isomers of the 2-methyltetrols have significantly different CCN properties that are also influenced

    oppositely in the presence of salts.

  • 6.
    Ekström, Sanna
    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).
    Hansson, Hans-Christen
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    The Cloud Condensation Nuclei (CCN) properties of 2-methyltetrols and C3-C6 polyols from osmolality and surface tension measurements2009In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 9, no 3, p. 973-980Article in journal (Refereed)
    Abstract [en]

    A significant fraction of the organic material in aerosols is made of highly soluble compounds such as sugars (mono-and polysaccharides) and polyols such as the 2-methyltetrols, methylerythritol and methyltreitol. Because of their high solubility these compounds are considered as potentially efficient CCN material. For the 2-methyltetrols, this would have important implications for cloud formation at global scale because they are thought to be produced by the atmospheric oxidation of isoprene. To investigate this question, the complete Kohler curves for C3-C6 polyols and the 2-methyltetrols have been determined experimentally from osmolality and surface tension measurements. Contrary to what was expected, none of these compounds displayed a higher CCN efficiency than organic acids. Their Raoult terms show that this limited CCN efficiency is due to their absence of dissociation in water, this in spite of slight surface-tension effects for the 2-methyltetrols. Thus, compounds such as saccharides and polyols would not contribute more to cloud formation than other organic compounds studied so far. In particular, the presence of 2-methyltetrols in aerosols would not particularly enhance cloud formation in the atmosphere, in contrary to recently suggested

  • 7.
    Ekström, Sanna
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Nozière, Barbara
    Stockholm University, Faculty of Science, Department of Meteorology .
    Hansson, Hans-Christen
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    The Cloud Condensation Nuclei (CCN) properties of 2-methyltetrols and C3–C6 polyols from osmolality and surface tension measurements (Discussion paper)2008In: Atmospheric Chemistry and Physics Discussion, ISSN 1680-7367, Vol. 8, no 5, p. 17237-17256Article in journal (Refereed)
    Abstract [en]

    A significant fraction of the organic material in aerosols is made of highly soluble compounds such as sugars (mono- and polysaccharides) and polyols, including the 2-methyltetrols, methylerythritol and methyltreitol. The high solubility of these compounds has brought the question of their potentially high CCN efficiency. For the 2-methyltetrols, this would have important implications for cloud formation at global scale because they are thought to be produced by the atmospheric oxidation of isoprene. To investigate this question, the complete Köhler curves for C3–C6 polyols and the 2-methyltetrols have been determined experimentally from osmolality and surface tension measurements. Contrary to what expected, none of these compounds displayed a critical supersaturation lower than those of inorganic salts or organic acids. Their Raoult terms show that this limited CCN efficiency is due to their absence of dissociation in water, this in spite of slight surface-tension effects for the 2-methyltetrols. Thus, compounds such as sugars and polyols would not contribute more to cloud formation in the atmosphere than any other organic compounds studied so far. In particular, the presence of 2-methyltetrols in aerosols would not particularly enhance cloud formation in the atmosphere, contrary to what has been suggested.

  • 8.
    Ekström, Sanna
    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).
    Hultberg, M.
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Magnér, J.
    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).
    Artaxo, P.
    A possible role of ground-based microorganisms on cloud formation in the atmosphere2010In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7, no 1, p. 387-394Article in journal (Refereed)
    Abstract [en]

    The formation of clouds is an important process for the atmosphere, the hydrological cycle, and climate, but some aspects of it are not completely understood. In this work, we show that microorganisms might affect cloud formation without leaving the Earth’s surface by releasing biological surfactants (or biosurfactants) in the environment, that make their way into atmospheric aerosols and could significantly enhance their activation into cloud droplets. In the first part of this work, the cloud-nucleating efficiency of standard biosurfactants was characterized and found to be better than that of any aerosol material studied so far, including inorganic salts. These results identify molecular structures that give organic compounds exceptional cloud-nucleating properties. In the second part, atmospheric aerosols were sampled at different locations: a temperate coastal site, a marine site, a temperate forest, and a tropical forest. Their surface tension was measured and found to be below 30 mN/m, the lowest reported for aerosols, to our knowledge. This very low surface tension was attributed to the presence of biosurfactants, the only natural substances able to reach to such low values. The presence of strong microbial surfactants in aerosols would be consistent with the organic fractions of exceptional cloud-nucleating efficiency recently found in aerosols, and with the correlations between algae bloom and cloud cover reported in the Southern Ocean. The results of this work also suggest that biosurfactants might be common in aerosols and thus of global relevance. If this is confirmed, a new role for microorganisms on the atmosphere and climate could be identified.

  • 9.
    Ekström, Sanna
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Wittbom, Cerina
    Svenningsson, Birgitta
    Nozière, Barbara
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Biosurfactants as CCN: comparison between on-line and off-line measurementsManuscript (preprint) (Other academic)
    Abstract [en]

    We are presenting the CCN properties for the bacterial compounds rhamnolipid and surfactin, which are extremely strong surfactants. Three organic:sodium chloride mixtures with mass percentages of 80:20, 50:50 and 20:80 were measured for each biosurfactant. Both on-line Cloud Condensation Nuclei Counter (CCNC) and off-line osmolality combined with surface tension measurements were performed to obtain two sets of critical supersaturations for various dry particle diameters. The critical supersaturations measured by the CCNC were systematically higher than the corresponding supersaturations derived from osmolality/surface tension measurements. A simple surface partitioning-adaption was applied to the off-line data and resulted in a correlation with the results from CCNC measurements for both mixtures with 20 wt% biosurfactant and the 50 wt% rhamnolipid mixture but not for the mixtures with 80 wt% biosurfactant and the 50 wt% surfactin mixture. An explanation can be unreliable CCNC results from the surfactin mixtures as we suspect poor dissolvement of the organic crystals. The choice of the assumed biosurfactant density also has an effect which should not be ignored. However, this indicate that the experimental method using osmolality and surface tension measurements together with a simple surface partitioning model can be used for strongly surfactant compounds as long as they do not dominate the particle mass. We also conclude that biosurfactants in mixed potential CCN particles can activate at relatively low supersaturation compared to other organic mixtures. Still, the critical supersaturation increases with increasing surfactant fraction.

  • 10.
    Gonzalez, Nelida J. D.
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Borg-Karlson, Anna-Karin
    Redeby, Johan Pettersson
    Noziere, Barbara
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Krejci, Radovan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Pei, Yuxin
    Dommen, Josef
    Prevot, Andre S. H.
    New method for resolving the enantiomeric composition of 2-methyltetrols in atmospheric organic aerosols2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 51, p. 9288-9294Article in journal (Refereed)
    Abstract [en]

    In order to facilitate the determination of the primary and secondary origin of atmospheric organic aerosols, a novel method involving chiral capillary gas chromatography coupled with mass spectrometry has been developed and validated. The method was focused on the analysis of 2-methylerythritol and 2-methylthreitol, considered to be tracers of secondary organic aerosols from the oxidation of atmospheric isoprene. The method was validated by performing various tests using authentic standards, including pure enantiomeric standards. The result showed that the analytical method itself does not affect the enantiomeric composition of the samples analyzed. The method was applied on atmospheric aerosols from a boreal forest collected in Aspvreten, Sweden and on laboratory samples obtained from liquid phase oxidation of isoprene and smog chamber experiments. Aerosol samples contained one enantiomer of 2-methylerythritol in significantly larger quantities than the others. In contrast, the liquid-phase oxidation of isoprene and its gas-phase oxidation in the smog chamber produced all enantiomers in equal quantities. The results obtained where the enantiomer fraction, EF, is larger than 0.50 suggest that 2-methyltetrols in atmospheric aerosols may also have biological origin. Information about the differences between enantiomer fractions obtained using this method brings new insights in the area of atmospheric aerosols.

  • 11.
    González, N
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Borg-Karlson, A.-K.
    Nozière, B
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Krejci, R
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Levula, J.
    Artaxo, P.
    New analytical technique for the identification of tracers for secondary organic material in atmospheric aerosols2008In: European Aerosol Conference (EAC) 2008: 24-29 August, Thessaloniki, Greece, 2008Conference paper (Refereed)
  • 12.
    Noziere, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Chabert, Perrine
    Abiotic C-C bond formation under environmental conditions: kinetics of the aldol condensation of acetaldehyde in water catalyzed by carbonate ions (CO32-)2010In: International Journal of Chemical Kinetics, ISSN 0538-8066, E-ISSN 1097-4601, Vol. 42, no 11, p. 676-686Article in journal (Refereed)
    Abstract [en]

    The role of CC bond-forming reactions such as aldol condensation in the degradation of organic matter in natural environments is receiving a renewed interest because naturally occurring ions, ammonium ions, NH+4, and carbonate ions, CO32−, have recently been reported to catalyze these reactions. While the catalysis of aldol condensation by OH has been widely studied, the catalytic properties of carbonate ions, CO32−, have been little studied, especially under environmental conditions. This work presents a study of the catalysis of the aldol condensation of acetaldehyde in aqueous solutions of sodium carbonate (0.1–50 mM) at T = 295 ± 2 K. By monitoring the absorbance of the main product, crotonaldehyde, instead of that of acetaldehyde, interferences from other reaction products and from side reactions, in particular a known Cannizzaro reaction, were avoided. The rate constant was found to be first order in acetaldehyde in the presence of both CO32− and OH, suggesting that previous studies reporting a second order for this base-catalyzed reaction were flawed. Comparisons between the rate constants in carbonate solutions and in sodium hydroxide solutions ([NaOH] = 0.3–50 mM) showed that, among the three bases present in carbonate solutions, CO32−, HCO3, and OH, OH was the main catalyst for pH ≤ 11. CO32− became the main catalyst at higher pH, whereas the catalytic contribution of HCO3 was negligible over the range of conditions studied (pH 10.3–11.3). Carbonate-catalyzed condensation reactions could contribute significantly to the degradation of organic matter in hyperalkaline natural environments (pH ≥ 11) and be at the origin of the macromolecular matter found in these environments.

  • 13.
    Noziere, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Ekström, Sanna
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Holmström, Sara
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Radical-initiated formation of organosulfates and surfactants in atmospheric aerosols2010In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 37, no L05806Article in journal (Refereed)
    Abstract [en]

    Many atmospheric aerosols contain both organic compounds and inorganic material, such as sulfate salts. In this work, we show that these sulfates could trigger some chemical transformations of the organic compounds by producing sulfate radicals, SO4, when exposed to UV light (280–320 nm). In particular, we show by mass spectrometry (LC/ESI-MSMS) that isoprene, methyl vinyl ketone, methacrolein, and α-pinene in irradiated sulfate solutions (ammonium and sodium sulfate) produce the same organosulfates as previously identified in aerosols, and even some that had remained unidentified until now. With a typical time constant of 9 h instead of 4600 days for esterifications, these radical reactions would be a plausible origin for the atmospheric organosulfates. These reactions also produced efficient surfactants, possibly resembling the long-chain organosulfates found in the experiments. Thus, photochemistry in mixed sulfate/organic aerosols could increase cloud condensation nuclei (CCN) numbers, which would be supported by previous atmospheric observations

  • 14.
    Nozière, B
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Light-absorbing organic matter in primary, aged, and biomass burning aerosols2008In: Amazonian Aerosols Workshop: February 18-22, Manaus, Brazil, 2008Conference paper (Refereed)
  • 15.
    Nozière, B
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Toward the direct mesurement of secondary organic aerosols2008In: Amazonian Aerosols Workshop: February 18-22, Manaus, Brazil, 2008Conference paper (Refereed)
  • 16.
    Nozière, B
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Dziedzic, P.
    Córdova, A.
    Common inorganic salts catalyze the transformations of organic compounds in atmospheric aerosols2008In: American Geophysical Union (AGU) Fall Meeting 2008: 15-19 December, San Fransisco, CA, USA, 2008Conference paper (Refereed)
  • 17.
    Nozière, Barbara
    Stockholm University, Faculty of Science, Department of Meteorology.
    Secondary organic aerosols: Thinking outside the smog chamber2007In: Global Change NewsLetter, ISSN 0284-5865, no 69, p. 4-7Article, review/survey (Other (popular science, discussion, etc.))
  • 18.
    Nozière, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A Kinetic and Mechanistic Study of the Amino Acid Catalyzed Aldol Condensation of Acetaldehyde in Aqueous and Salt Solutions2008In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 112, no 13, p. 2827-2837Article in journal (Refereed)
    Abstract [en]

    The amino acid-catalyzed aldol condensation is of great interest in organic synthesis and natural environments such as atmospheric particles. But kinetic and mechanistic information on these reactions is limited. In this work, the kinetics of the aldol condensation of acetaldehyde in water and aqueous salt solutions (NaCl, CaCl2, Na2SO4, MgSO4), catalyzed by five amino acids (glycine, alanine, serine, arginine, and proline) at room temperature (295 ± 2K) has been studied. Monitoring the formation of three products, crotonaldehyde, 2,4-hexadienal, and 2,4,6-octatrienal by UV-Visible absorption over 200 – 1100 nm revealed two distinct kinetic regimes: at low amino acid concentrations (in all cases, below 0.1 M) the overall reaction was first order with respect to acetaldehyde and kinetically limited by the formation of the enamine intermediate. At larger amino acid concentrations (at least 0.3 M) the kinetics was second order and controlled by the C-C bond-forming step. The first-order rate constants increased linearly with amino acid concentration, consistent with the enamine formation. Inorganic salts further accelerated the enamine formation according to their pKb plausibly by facilitating the iminium and/or enamine formation. The rate constant of the C-C bond-forming step varied with the square of amino acid concentration, suggesting the involvement of two amino acid molecules. Thus, the reaction proceeded via a Mannich pathway. However, the contribution of an aldol pathway, first-order in amino acid, could not be excluded. Our results show that the rate constant for the self-condensation of acetaldehyde in aqueous atmospheric aerosols (up to 10 of mM of amino acids) is identical as in sulfuric acid 10 - 15 M (kI ~ 10-7 - 10-6 s-1), clearly illustrating the potential importance of amino acid catalysis in natural environments. This work also demonstrates that under usual laboratory conditions and in natural environments aldol condensation is likely to be kinetically controlled by the enamine formation. Notably, kinetic investigations of the C-C bond-forming addition step would only be possible with high concentrations of amino acids.

  • 19. Nozière, Barbara
    et al.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic transformations of organic matter in tropospheric aerosols - Importance for aerosol optical properties and gas-phase chemistry2008In: Geophysical Research Abstracts, EGU General Assembly 2008, Vol. 10, 2008, p. EGU2008-AConference paper (Refereed)
  • 20.
    Nozière, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Common inorganic ions are efficient catalysts for organic reactions in atmospheric aerosols and other natural environments2009In: Atmospheric Chemistry and Physics Discussion, Vol. 9, no 1, p. 1-21Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    In this work, inorganic ammonium ions, NH4+, and carbonate ions, CO32-, are reported for the first time as catalysts for organic reactions in atmospheric aerosols and other natural environments at the Earth’s surface. These reactions include the formation of C-C and C-O bonds by aldol condensation and acetal formation, and reveal a new aspect of the interactions between organic and inorganic materials in natural environments. The catalytic properties of inorganic ammonium ions, in particular, were not previously known in chemistry. The reactions were found to be as fast in tropospheric ammonium sulfate composition as in concentrated sulfuric acid. The ubiquitous presence and large concentrations of ammonium ions in tropospheric aerosols would make of ammonium catalysis a main consumption pathway for organic compounds in these aerosols, while acid catalysis would have a minor contribution. In particular, ammonium catalysis would account quantitatively for the aging of carbonyl compounds into secondary “fulvic” compounds in tropospheric aerosols, a transformation affecting the optical properties of these aerosols. In general, ammonium catalysis is likely to be responsible for many observations previously attributed to acid catalysis in the troposphere.

  • 21.
    Nozière, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology.
    Dziedzic, Pawel
    Department of Organic Chemistry.
    Córdova, Armando
    Department of Organic Chemistry.
    Formation of secondary light-absorbing "fulvic-like" oligomers: A common process in aqueous and ionic atmospheric aerosols ?2007In: Geophysical Research Letters, ISSN 0094-8276, Vol. 34, no L21812, p. 1-5Article in journal (Refereed)
    Abstract [en]

    Secondary Organic Aerosols (SOA), produced by the transformation of organic gases in the atmosphere, have received a considerable amount of attention over the last three decades because of their expected roles in urban pollution, global aerosol loadings, and cloud formation. While most investigations have been performed under controlled conditions such as smog chambers, atmospheric observations of SOA are sparse, mostly indirect, and critically limit the knowledge of these aerosols. In particular, techniques for the specific observation of the secondary organic fraction of aerosols in the atmosphere need to be developed, and seem today the most likely pathways to make significant progress in this topic.

  • 22.
    Nozière, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Formation of secondary light-absorbing "fulvic-like'' oligomers: A common process in aqueous and ionic atmospheric particles?2007In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, no 21, p. L21812-Article in journal (Refereed)
    Abstract [en]

    Light-absorbing ''humic-like'' compounds of secondary origin have been consistently reported in partly inorganic aerosols and in fog waters but their formation could not be explained until now. In this work, we demonstrate that amino acid- and ammonium sulfate-catalyzed reactions in water and ionic solutions produce compounds of identical molecular and optical properties and account well for the quantities found in atmospheric particles. For typical aerosol concentrations of amino acids or ammonium sulfate the rate constants of reaction are found to be identical to the one in concentrated sulfuric acid (10-15 M), clearly demonstrating the efficiency of these catalysts. Our results also show that these reactions should be common in aqueous and ionic aerosols, as confirmed by the observations, and significantly impact their absorption index. In particular, previous radiative calculations indicate that they should substantially reduce current estimates of the cooling contribution of sulfate aerosols on climate.

  • 23.
    Nozière, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Inorganic ammonium salts and carbonate salts are efficient catalysts for aldol condensation in atmospheric aerosols2010In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 12, no 15, p. 3864-3872Article in journal (Refereed)
    Abstract [en]

    In natural environments such as atmospheric aerosols, organic compounds coexist with inorganic salts but, until recently, were not thought to interact chemically. We have recently shown that inorganic ammonium ions, NH4+, act as catalysts for acetal formation from glyoxal, a common atmospheric gas. In this work, we report that inorganic ammonium ions, NH4+, and carbonate ions, CO32−, are also efficient catalysts for the aldol condensation of carbonyl compounds. In the case of NH4+ this was not previously known, and was patented prior to this article. The kinetic results presented in this work show that, for the concentrations of ammonium and carbonate ions present in tropospheric aerosols, the aldol condensation of acetaldehyde and acetone could be as fast as in concentrated sulfuric acid and might compete with their reactions with OH radicals. These catalytic processes could produce significant amounts of polyconjugated, light-absorbing compounds in aerosols, and thus affect their direct forcing on climate. For organic gases with large Henry's law coefficients, these reactions could also result in a significant uptake and in the formation of secondary organic aerosols (SOA). This work reinforces the recent findings that inorganic salts are not inert towards organic compounds in aerosols and shows, in particular, that common ones, such as ammonium and carbonate salts, might even play important roles in their chemical transformations.

  • 24.
    Nozière, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Products and Kinetics of the Liquid-Phase Reaction of Glyoxal Catalyzed by Ammonium Ions (NH4+)2009In: Journal of Physical Chemistry A, ISSN 1089-5639, Vol. 113, no 1, p. 231-237Article in journal (Refereed)
    Abstract [en]

    Glyoxal, a common atmospheric gas, has been reported to be depleted in some regions of the atmosphere. The corresponding sink could be accounted for by reactions in or at the surface of atmospheric particles, but these reactions were not identified. Recently, we showed that inorganic ammonium ions, NH4+, are efficient catalysts for reactions of carbonyl compounds, including glyoxal, in the liquid phase. To determine whether ammonium-catalyzed reactions can contribute to depletion of glyoxal in the atmosphere, the reactivity of this compound in aqueous solutions containing ammonium salts (ammonium sulfate, chloride, fluoride, and phosphate) at 298 K has been studied. The products identified by LC-HRMS and UV absorption revealed a mechanism involving two distinct pathways: a Bronsted acid pathway and an iminium pathway. The kinetics of the iminium pathway was studied by monitoring formation of a specific product. This pathway was second order in glyoxal in most of the solutions studied and should therefore be second order in most ammonium containing aerosols in the atmosphere. The corresponding rate constant, kII (M-1 s-1), increased strongly with ammonium ion activity, aNH4+, and pH:

    kII (M-1 s-1) ) (2 ( 1) × 10-10 exp(1.5 ( 0.8)aNH4+ exp(2.5 ( 0.2)pH.

    This iminium pathway is a lower limit for the ammonium-catalyzed consumption of glyoxal, but the contribution of the acid pathway is expected to be small in tropospheric aerosols. With these results the reactive uptake of glyoxal on ammonium-containing aerosols was estimated and shown to be a possible explanation for the depletion of this compound in Mexico City.

  • 25.
    Nozière, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology.
    Esteve, William
    Light-absorbing aldol condensation products in acidic aerosols: Spectra, kinetics, and contribution to the absorption index2007In: Atmospheric environment, ISSN 1352-2310, Vol. 41, no 6, p. 1150-1163Article in journal (Refereed)
    Abstract [en]

    The radiative properties of aerosols that are transparent to light in the near-UV and visible, such as sulfate aerosols, can be dramatically modified when mixed with absorbing material such as soot.

    In a previous work we had shown that the aldol condensation of carbonyl compounds produces light-absorbing compounds in sulfuric acid solutions. In this work we report the spectroscopic and kinetic parameters necessary to estimate the effects of these reactions on the absorption index of sulfuric acid aerosols in the atmosphere. The absorption spectra obtained from the reactions of six different carbonyl compounds (acetaldehyde, acetone, propanal, butanal, 2-butanone, and trifluoroacetone) and their mixtures were compared over 190–1100 nm. The results indicated that most carbonyl compounds should be able to undergo aldol condensation.

    The products are oligomers absorbing light in the 300–500 nm region where few other compounds absorb, making them important for the radiative properties of aerosols.

    Kinetic experiments in 96–75 wt% H2SO4 solutions and between 273 and 314 K gave an activation energy for the rate constant of formation of the aldol products of acetaldehyde of −(70±15) kJ mol−1 in 96 wt% solution and showed that the effect of acid concentration was exponential. A complete expression for this rate constant is proposed where the absolute value in 96 wt% H2SO4 and at 298 K is scaled to the Henry's law coefficient for acetaldehyde and the absorption cross-section for the aldol products assumed in this work. The absorption index of stratospheric sulfuric acid aerosols after a 2-year residence time was estimated to 2×10−4, optically equivalent to a content of 0.5% of soot and potentially significant for the radiative forcing of these aerosols and for satellite observations in channels where the aldol products absorb.

  • 26.
    Nozière, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    González, Nélida J. D.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Borg-Karlson, Anna-Karin
    Pei, Yuxin
    Redeby, Johan Pettersson
    Krejci, Radovan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Dommen, Josef
    Prevot, Andre S. H.
    Anthonsen, Thorleif
    Atmospheric chemistry in stereo: A new look at secondary organic aerosols from isoprene2011In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, p. L11807-Article in journal (Refereed)
    Abstract [en]

    Isoprene, a compound emitted by vegetation, could be a major contributor to secondary organic aerosols (SOA) in the atmosphere. The main evidence for this contribution were the 2-methylbutane-1,2,3,4-tetraols, or 2-methyltetrols (2-methylerythritol and 2-methylthreitol) present in ambient aerosols. In this work, the four stereoisomers of these tetraols were analyzed in aerosols from Aspvreten, Sweden. 2-C-methyl-D-erythritol was found in excess over its enantiomer in the Spring/Summer, by up to 29% in July. This clearly indicated some biological origins for this enantiomer, consistent with its well-documented production by plants and other living organisms. In addition, a minimum of 20 to 60% of the mass of racemic tetraols appeared from biological origin. Thus, the SOA mass produced by isoprene in the atmosphere is less than what indicated by the 2-methyltetrols in aerosols. Our results also demonstrate that stereochemical speciation can distinguish primary and secondary organic material in atmospheric aerosols.

1 - 26 of 26
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