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International audience; A key Earth system science question is the role of atmospheric deposition in supplying vital nutrients to the phytoplankton that form the base of marine food webs. Industrial and vehicular pollution, wildfires, volcanoes, biogenic debris, and desert dust all carry nutrients within their plumes throughout the globe. In remote ocean ecosystems, aerosol deposition represents an essential new source of nutrients for primary production. The large spatiotemporal variability in aerosols from myriad sources combined with the differential responses of marine biota to changing fluxes makes it crucially important to understand where, when, and how much nutrients from the atmosphere enter marine ecosystems. This review brings together existing literature, experimental evidence of impacts, and new atmospheric nutrient observations that can be compared with atmospheric and ocean biogeochemistry modeling. We evaluate the contribution and spatiotemporal variability of nutrient-bearing aerosols from desert dust, wildfire, volcanic, and anthropogenic sources, including the organic component, deposition fluxes, and oceanic impacts. Expected final online publication date for the Annual Review of Marine Science, Volume 14 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

In this review, we cover selected research on secondary organic aerosol (SOA) formation from isoprene, from the beginning of research, about two decades ago, to today. The review begins with the first observations of isoprene SOA markers, i.e., 2-methyltetrols, in ambient fine aerosol and focuses on studies dealing with molecular characterization, speciation, formation mechanisms, and source apportionment. A historic account is given on how research on isoprene SOA has developed. The isoprene SOA system is rather complex, with different pathways being followed in pristine and polluted conditions. For SOA formation from isoprene, acid-catalyzed hydrolysis is necessary, and sulfuric acid enhances SOA by forming additional nonvolatile products such as organosulfates. Certain results reported in early papers have been re-interpreted in the light of recent results; for example, the formation of C5-alkene triols. Attention is given to mass spectrometric and separation techniques, which played a crucial role in molecular characterization. The unambiguous structural characterization of isoprene SOA markers has been achieved, owing to the preparation of reference compounds. Efforts have also been made to use air quality data to estimate the influence of biogenic and pollution aerosol sources. This review examines the use of an organic marker-based method and positive matrix factorization to apportion SOA from different sources, including isoprene SOA.

Molybdenum (Mo) is a key cofactor in enzymes used for nitrogen (N) fixation and nitrate reduction, and the low availability of Mo can constrain N inputs, affecting ecosystem productivity. Natural atmospheric Mo aerosolization and deposition from sources such as desert dust, sea‐salt spray, and volcanoes can affect ecosystem function across long timescales, but anthropogenic activities such as combustion, motor vehicles, and agricultural dust have accelerated the natural Mo cycle. Here we combined a synthesis of global atmospheric concentration observations and modeling to identify and estimate anthropogenic sources of atmospheric Mo. To project the impact of atmospheric Mo on terrestrial ecosystems, we synthesized soil Mo data and estimated the global distribution of soil Mo using two approaches to calculate turnover times. We estimated global emissions of atmospheric Mo in aerosols (

Direct infusion analysis using soft ionization techniques coupled to ultra-high-resolution mass spectrometers (UHRMS) allows screening of thousands of organic species in complex samples. Despite the high analytical throughput of direct infusion, this technique is known to be prone to matrix effects caused by changes in the ionization efficiency of an analyte, ion suppression, or enhancement due to the presence of certain compounds and inorganic salts in the sample. In this study we compared two soft ionization sources, that is, heated electrospray ionization (HESI) and nano-ESI for the analysis of atmospheric aerosol samples in the negative ionization mode. In-source fragmentation tests were conducted and experiments involving sample desalting through solid-phase extraction (SPE) with a reversed phase functionalized polymeric sorbent and spiking samples with inorganic salt were performed. Both ionization sources showed specific advantages and disadvantages for the direct infusion analysis of atmospheric aerosol extracts. The mass spectra of aerosol samples analyzed using HESI contained a large number of high molecular weight homologues containing sulfur and nitrogen, suggesting that this source is prone to formation of salt adducts and noncovalent compounds in samples enriched with inorganic salts. Data from the same aerosol sample extracts analyzed using nanoelectrospray ionization (nano-ESI) show less adduct formation; however, a decrease in the number of homologues was observed, as well as loss of molecules at higher mass range, indicating that the nano-ESI source is more prone to ion suppression. Irrespective of ionization source, SPE pretreatment significantly improved ion recoveries for organic species with nonpolar and moderately polar functional groups, but lower recoveries were obtained for highly oxygenated molecules. Therefore, while SPE reduced in-source adduct formation, it also limited the range of compounds identified through a single analysis.

Isoprene (C5H8) is the main non-methane hydrocarbon emitted into the global atmosphere. Despite intense research, atmospheric transformations of isoprene leading to secondary organic aerosol (SOA) are still not fully understood, including its multiphase chemical reactions. Herein, we report on the detailed structural characterization of atmospherically relevant isoprenederived organosulfates (OSs) with a molecular weight (MW) of 212 (C5H8SO7), which are abundantly present in both ambient fine aerosol (PM2.5) and laboratory-generated isoprene SOA. The results obtained from smog chamber-generated isoprene SOA and aqueous-phase laboratory experiments coupled to the S(IV)-autooxidation chemistry of isoprene, 3-methyl-2(5H)-furanone, and 4-methyl-2(5H)-furanone, allowed us for the first time to fully elucidate the isomeric structures of the MW 212 OSs. By applying liquid chromatography interfaced to electrospray ionization high-resolution mass spectrometry, we firmly confirmed six positional isomers of the MW 212 OSs in PM2.5 collected from different sites in Europe and the United States. Our results also show that despite the low solubility of isoprene in water, aqueous-phase or multiphase chemistry can play an important role in the formation of OSs from isoprene. Possible formation mechanisms for the MW 212 OSs are also tentatively proposed.

The Spring Festival (SF) is the most important holiday in China for family reunion and tourism. During the 2015 SF an intensive observation campaign of air quality was conducted to study the impact of the anthropogenic activities and the dynamic characteristics of the sources. During the study period, pollution episodes frequently occurred with 12 days exceeding the Chinese Ambient Air Quality Standards for 24-h average PM2.5 (75 μg/m3), even 8 days with exceeding 150 μg/m3. The daily maximum PM2.5 concentration reached 350 μg/m3 while the hourly minimum visibility was

Five-year-long (1991–1996) aerosol trace element data sets for the fine (PM2) size fraction from the sites of Birkenes and Skreadalen in southern Norway were reanalysed by US EPA positive matrix factorization PMF5 in order to assess the sources and their contribution to the PM2 aerosol. The data sets contained the concentrations of the particulate mass (PM), black carbon (BC) and 21 elements in over 700 samples for each of the two sites. The PM was obtained from weighing with a microbalance and BC was determined with a light reflectance technique. The data for the elements were obtained by a combination of particle-induced X-ray emission and instrumental neutron activation analysis. Eight source factors were retained for each site, i.e., (i) secondary sulfate, which accounted for around 40% of the average measured PM2 mass, (ii) wood burning, with BC, K, Zn and As, which accounted for about 17%, (iii) an iodine factor (with also Br and Se), which is probably related to a marine biogenic source and was responsible for about 6.5%, (iv) aged sea salt with Na, Mg, Cl and Ca, but heavily depleted in Cl; (v) a crustal factor containing Al, Si, Ca, Ti and Fe; (vi) a heavy oil burning factor with V and Ni in a ratio of 3–4; (vii) a general pollution factor (with Cu, Zn, As, Se, Sb and Pb), and (viii) an almost pure manganese factor, which is attributed to Mn and FeMn industries in southern Norway. The results were substantially different from those of an earlier PMF analysis, in which use was made of PMF2.

Carbonaceous aerosols in high emission areas attract worldwide attention of the scientific community and the public due to their adverse impacts on the environment, human health and climate. However, long-term continuous hourly measurements are scarce on the regional scale. In this study, a one-year hourly measurement (from December 1, 2016 to November 30, 2017) of organic carbon (OC) and elemental carbon (EC) in airborne fine particles was performed using semi-continuous OC/EC analyzers in Beijing, Tianjin, Shijiazhuang and Tangshan in the Beijing-Tianjin-Hebei (BTH) region in China, which is one of high emission areas in China, even in the world. Marked spatiotemporal variations were observed. The highest concentrations of OC (22.8 ± 30.6 μg/m 3 ) and EC (5.4 ± 6.5 μg/m 3 ) occurred in Shijiangzhuang while the lowest concentrations of OC (11.0 ± 10.7 μg/m 3 ) and EC (3.1 ± 3.6 μg/m 3 ) were obtained in Beijing and Tianjin, respectively. Pronounced monthly, seasonal and diurnal variations of OC and EC were recorded. Compared to published data from the past two decades for the BTH region, our OC and EC levels were lower, implying some effect of recent measures for improving the air quality. Significant correlations of OC versus EC (p < 0.001) were found throughout the study period with high slopes and correlation coefficients in winter, but low slopes and correlation coefficients in summer. The estimated secondary OC (SOC), based on the minimum R squared (MRS) method, represented 29%, 47%, 38% and 48% of the OC for Beijing, Tianjin, Shijiazhuang and Tangshan, respectively. These percentages are larger than previous ones obtained for the BTH region in the past decade. There were obvious differences in the potential source regions of OC and EC among the four cities. Obvious prominent potential source areas of OC and EC were observed for Beijing, which were mainly located in the central and western areas of Inner Mongolia and even extended to the Mongolian regions, which is different from the findings in previous studies. For all sites, adjacent areas of the main provinces in northern China were found to be important potential source areas. © 2019 The Authors

Atmospheric particulate matter samples (PM10) were collected at an urban site in Sao Paulo (SPA) city in winter episodes of 2012 and 2013. Several organic compounds were determined in the samples to characterize the composition of the particulate matter with emphasis on marker compounds for biomass burning. Organic carbon (OC), elemental carbon (EC), monosaccharide anhydrides, monosaccharides, nitroaromatic compounds, isoprene secondary organic aerosol markers, and polyols were measured. The PM10, OC and EC median concentrations were higher for samples collected in 2013 than in 2012, with the contribution of OC to the PM10 mass being 17% and 11% in 2012 and 2013. The three anhydrosugars, levoglucosan, mannosan and galactosan together, accounted, on average, for 2.0 and 2.2% of the OC mass in 2012 and 2013, whereas the nitro-aromatic compounds, including 4-nitrophenol, 4-nitrocatechol, isomeric methyl nitrocatechols and dimethyl catechols, showed the same trend, contributing, on average, for 0.28% and 0.35% to the OC mass in 2012 and 2013, and thus indicating a higher contribution from biomass burning in 2013 compared to 2012. The methyl nitrocatechols were substantially correlated with levoglucosan, consistent with their proposed origin from biomass burning. The results demonstrate that biomass burning compounds are important contributors to the OC mass, especially in winter. Furthermore, it is suggested that a levoglucosan/galactosan ratio smaller than about 30 may be indicative for regional sugarcane burning and not for advected air from sites that are impacted by tropical forest fires. (C) 2016 Elsevier Ltd. All rights reserved.

We show in the present study that the unsaturated aldehydes 2-E-pentenal, 2-E-hexenal, and 3-Z-hexenal are biogenic volatile organic compound (BVOC) precursors for polar organosulfates with molecular weights (MWs) 230 and 214, which are also present in ambient fine aerosol from a forested site, i.e., K-puszta, Hungary. These results complement those obtained in a previous study showing that the green leaf aldehyde 3-Z-hexenal serves as a precursor for MW 226 organosulfates. Thus, in addition to isoprene, the green leaf volatiles (GLVs) 2-E-hexenal and 3-Z-hexenal, emitted due to plant stress (mechanical wounding or insect attack), and 2-E-pentenal, a photolysis product of 3-Z-hexenal, should be taken into account for secondary organic aerosol and organosulfate formation. Polar organosulfates are of climatic relevance because of their hydrophilic properties and cloud effects. Extensive use was made of organic mass spectrometry (MS) and detailed interpretation of MS data (i.e., ion trap MS and accurate mass measurements) to elucidate the chemical structures of the MW 230, 214 and 170 organosulfates formed from 2-E-pentenal and indirectly from 2-E-hexenal and 3-Z-hexenal. In addition, quantum chemical calculations were performed to explain the different mass spectral behavior of 2,3-dihydroxypentanoic acid sulfate derivatives, where only the isomer with the sulfate group at C-3 results in the loss of SO3. The MW 214 organosulfates formed from 2-E-pentenal are explained by epoxidation of the double bond in the gas phase and sulfation of the epoxy group with sulfuric acid in the particle phase through the same pathway as that proposed for 3-sulfooxy-2-hydroxy-2-methylpropanoic acid from the isoprene-related α,β-unsaturated aldehyde methacrolein in previous work (Lin et al., 2013). The MW 230 organosulfates formed from 2-E-pentenal are tentatively explained by a novel pathway, which bears features of the latter pathway but introduces an additional hydroxyl group at the C-4 position. Evidence is also presented that the MW 214 positional isomer, 2-sulfooxy-3-hydroxypentanoic acid, is unstable and decarboxylates, giving rise to 1-sulfooxy-2-hydroxybutane, a MW 170 organosulfate. Furthermore, evidence is obtained that lactic acid sulfate is generated from 2-E-pentenal. This chemistry could be important on a regional and local scale where GLV emissions such as from grasses and cereal crops are substantial.

To control the spread of the novel coronavirus disease 2019 (COVID-19) in China, many anthropogenic activities were reduced and even closed on the national scale. To study the impact of this reduction and closing down, hourly concentrations of PM2.5-related elements were measured at a rural site before (12–25 January 2020), during (26 January–9 February 2020) and after (22 March–2 April 2020) the control period when all people remained socially isolated in their homes and could not return to economic zones for work. Nine major sources were identified by the positive matrix factorization model, including fireworks burning, coal combustion, vehicle emissions, dust, Cr industry, oil combustion, Se industry, Zn smelter, and iron and steel industry. Before the control period, K, Fe, Ca, Zn, Ba and Cu were the main elements, and fireworks burning, Zn smelter and vehicle emissions provided the highest contributions to the total element mass with 55%, 12.1% and 10.3%, respectively. During the control period, K, Fe, Ba, Cu and Zn were the dominating elements, and fireworks burning and vehicle emissions contributed 55% and 27% of the total element mass. After the control period, Fe, K, Ca, Zn and Ba were the main elements, and dust and iron and steel industry were responsible for 56% and 21% of the total element mass. The increased contribution from vehicle emissions during the control period could be attributed to our sampling site being near a town hospital and the fact that the vehicle activities were not restricted. The source apportionment results were also related to air mass backward trajectories. The largest reductions of dust, coal combustion, and the industrial sources (Cr industry, Zn smelter, Se industry, iron and steel industry) were distinctly seen for northwest transport (Ulanqab) and were least significant for northeast transport (Tangshan and Tianjin)., Graphical abstract Unlabelled Image, Highlights • The effects of COVID-19 and its control were studied for a rural site in Xianghe. • PM2.5-related elements were hourly measured during our study. • Dust, coal combustion and industrial sources decreased during the control period. • Beyond expectation, vehicle emissions increased during the control period. • Lowest reductions of industrial emission occurred for air masses from northeast.

Continuous measurements between July 2012 and December 2015 at the Henties Bay Aerosol Observatory (HBAO; 22∘ S, 14∘05′ E), Namibia, show that, during the austral wintertime, transport of light-absorbing black carbon aerosols occurs at low level into the marine boundary layer. The average of daily concentrations of equivalent black carbon (eBC) over the whole sampling period is 53 (±55) ng m−3. Peak values above 200 ng m−3 and up to 800 ng m−3 occur seasonally from May to August, ahead of the dry season peak of biomass burning in southern Africa (August to October). Analysis of 3-day air mass back-trajectories show that air masses from the South Atlantic Ocean south of Henties Bay are generally cleaner than air having originated over the ocean north of Henties Bay, influenced by the outflow of the major biomass burning plume, and from the continent, where wildfires occur. Additional episodic peak concentrations, even for oceanic transport, indicate that pollution from distant sources in South Africa and maritime traffic along the Atlantic ship tracks could be important. While we expect the direct radiative effect to be negligible, the indirect effect on the microphysical properties of the stratocumulus clouds and the deposition to the ocean could be significant and deserve further investigation, specifically ahead of the dry season.

Sources of elemental carbon (EC) and organic carbon (OC) in atmospheric aerosols (carbonaceous aerosols) were investigated by collection of weekly aerosol filter samples at six background sites in Northern Europe (Birkenes, Norway; Vavihill, Sweden; Risoe, Denmark; Cabauw and Rotterdam in The Netherlands; Melpitz, Germany) during winter 2013. Analysis of 14C and a set of molecular tracers were used to constrain the sources of EC and OC. During the four-week campaign, most sites (in particular those in Germany and The Netherlands) were affected by an episode during the first two weeks with high concentrations of aerosol, as continental air masses were transported westward. The analysis results showed a clear, increasing north to south gradient for most molecular tracers. Total carbon (TC = OC + EC) at Birkenes showed an average concentration of 0.5 ± 0.3 μg C m−3, whereas the average concentration at Melpitz was 6.0 ± 4.3 μg C m−3. One weekly mean TC concentration as high as 11 μg C m−3 was observed at Melpitz. Average levoglucosan concentrations varied by an order of magnitude from 25 ± 13 ng m−3 (Birkenes) to 249 ± 13 ng m−3 (Melpitz), while concentrations of tracers of fungal spores (arabitol and mannitol) and vegetative debris (cellulose) were very low, showing a minor influence of primary biological aerosol particles during the North European winter. The fraction of modern carbon generally varied from 0.57 (Melpitz) to 0.91 (Birkenes), showing an opposite trend compared to the molecular tracers and TC. Total concentrations of 10 biogenic and anthropogenic carboxylic acids, mainly of secondary origin, were 4–53 ng m−3, with the lowest concentrations observed at Birkenes and the highest at Melpitz. However, the highest relative concentrations of carboxylic acids (normalized to TC) were observed at the most northern sites. Levels of organosulphates and nitrooxy organosulphates varied more than two orders of magnitude, from 2 to 414 ng m−3, between individual sites and samples. The three sites Melpitz, Rotterdam and Cabauw, located closest to source regions in continental Europe, showed very high levels of organosulphates and nitrooxy organosulphates (up to 414 ng m−3) during the first two weeks of the study, while low levels (40% of TC), while use and combustion of fossil fuels was the second most important source. Furthermore, EC from biomass burning accounted for 7–16% of TC, whereas EC from fossil sources contributed to

In the 1980s and 1990s nearly half of the elemental analyses of atmospheric aerosol samples were performed by PIXE. Since then, other techniques for elemental analysis became available and there has been a steady increase in studies on organic aerosol constituents and other aspects of aerosols, especially in the areas of nucleation (new particle formation), optical properties, and the role of aerosol particles in cloud formation and properties. First, a brief overview and discussion is given of the developments and trends in atmospheric aerosol analysis and research of the past three decades. Subsequently, it is indicated that there is still invaluable work to be done by PIXE in atmospheric aerosol research, especially if one teams up with other aerosol researchers and performs complementary measurements, e.g., on small aerosol samples that are taken with high-time resolution. Fine examples of such research are the work done by the Lund group in the CARIBIC aircraft studies and the analysis of circular streaker samples by the Florence PIXE group. These and other examples are presented and other possibilities of PIXE are indicated. (C) 2015 Elsevier B.V. All rights reserved.

Continuous measurements between July 2012 and December 2015 at the Henties Bay Aerosol Observatory (HBAO; 22° S, 14°05’ E), Namibia, show that, during the austral wintertime, transport of light-absorbing black carbon aerosols occurs at low-level into the marine boundary layer from the South East Atlantic coast. Daily concentrations reach 986 ng m-3 and display a seasonal maximum from May to August, ahead of the dry season peak of biomass burning in southern Africa (August to October). This outflow is due to either anti-cyclonic circulation or along-the-coast streamlines and contributes to the transport of both biomass and fossil fuel burning aerosols. We estimate that the particle number concentration associated with this transport could contribute up to 2000 cm-3 to the cloud droplet number concentration with respect to pristine conditions. Their direct radiative effect is negligible.

The basic principles, instrumentation, sample types, and applications of the particle-induced X-ray emission (PIXE) technique are presented. PIXE is an ion beam analysis (IBA) technique, whereby energetic heavy charged particles (usually protons of 1–4 MeV) are used to induce element-specific X-ray emission. The X-rays are generally measured with an energy-dispersive solid state detector, nowadays typically a silicon drift detector (SDD), and the elements from Na to U can be detected with good sensitivity and good detection limits, down to 0.1 mg kg − 1 in favorable cases. By combining PIXE with other IBA techniques also the light elements (from H to F) can be measured.

A one-year-long aerosol characterization study was conducted from July 2002 through July 2003, in Beijing, China. Twenty-four hour PM2.5 and PM10 filter samples were collected, and about 50 aerosol samples of each type were obtained. Organic, elemental, and total carbon, levoglucosan and other organic compounds, and inorganic ionic species were measured. The overall mean PM mass concentrations were 99 and 175 mu g/m(3) for PM2.5 and PM10, respectively. Total carbon was the main component in both PM2.5 and PM10, with overall mean concentrations of 21 and 30 mu g/m(3), respectively. Of the organic compounds measured, levoglucosan exhibited the highest levels (overall mean of 0.31 mu g/m(3) in PM2.5 and of 0.40 ng/m(3) in PM10). Sulfate was the most prominent inorganic ionic species, with overall mean levels of 15.6 and 17.0 mu g/m(3) in PM2.5 and PM10, respectively. Most components measured were predominantly present in the PM2.5 size fraction; the overall mean PM2.5/PM10 ratio was typically in the range of 0.7-0.8, but this ratio was only 0.55 for the PM mass and for Ca2+ it was as low as 0.19. In PM2.5, total carbon exhibited relatively larger concentration levels (30 mu g/m(3)) in winter than in the other seasons. K+ also exhibited a relatively high concentration level in the winter season, with 2.3 mu g/m(3) in PM2.5. The contribution from biomass burning to K+ in PM2.5 was estimated on the basis of the levoglucosan data and the minimum K+/levoglucosan ratios obtained throughout the year; it was found that the contribution was largest in autumn, with 44%.

An oxygenated MW 188 compound is commonly observed in substantial abundance in atmospheric aerosol samples and was proposed in previous studies as an a-pinene-related marker compound that is associated with aging processes. Owing to difficulties in producing this compound in sufficient amounts in laboratory studies and the occurrence of isobaric isomers, a complete assignment for individual MW 188 compounds could not be achieved in these studies. Results from a comprehensive mass spectrometric analysis are presented here to corroborate the proposed structure of the most abundant MW 188 compound as a 2-hydroxyterpenylic acid diastereoisomer with 2R,3R configuration. The application of collision-induced dissociation with liquid chromatography/electrospray ionization-ion trap mass spectrometry in both negative and positive ion modes, as well as chemical derivatization to methyl ester derivatives and analysis by the latter technique and gas chromatography/electron ionization mass spectrometry, enabled a comprehensive characterization of MW 188 isomers, including a detailed study of the fragmentation behavior using both mass spectrometric techniques. Furthermore, a MW 188 positional isomer, 4-hydroxyterpenylic acid, was tentatively identified, which also is of atmospheric relevance as it could be detected in ambient fine aerosol. Quantum chemical calculations were performed to support the diastereoisomeric assignment of the 2-hydroxyterpenylic acid isomers. Results from a time-resolved a-pinene photooxidation experiment show that the 2-hydroxyterpenylic acid 2R,3R diastereoisomer has a time profile distinctly different from that of 3-methyl-1,2,3-butanetricarboxylic acid, a marker for oxygenated (aged) secondary organic aerosol. This study presents a comprehensive chemical data set for a more complete structural characterization of hydroxyterpenylic acids in ambient fine aerosol, which sets the foundation to better understand the atmospheric fate of a-pinene in future studies.

Nitro-organic compounds were determined in a one-year set of atmospheric PM10 filter samples that were collected at a rural background site in Hamme, Belgium. In an earlier study, it was found that the site was substantially impacted by wood burning, making the filter samples appropriate for further investigations on wood burning indicators. In total, four groups of nitro-aromatic compounds (with molecular weights (MWs) of 139, 155, 169, and 183), cc-pinene-related nitrooxy-organosulfates (MW 295), and the resin acid dehydroabietic acid (DHAA, MW 300) were quantified using liquid chromatography combined with negative ion electrospray ionization mass spectrometry. The annual mean concentrations were 0.94, 6.0, 7.7, 4.8, 7.8, and 1.76 ng m(-3) for the sum of the nitrophenols (MW 139), 4-nitrocatechol (MW 155), the sums of the methyl-nitrocatechols (MW 169), of the dimethyl-nitrocatechols (MW 183), and of the cz-pinene-related nitrooxy-organosulfates (MW 295), and DHAA (MW 300), respectively. 4-nitrocatechol, the sum of the methyl-nitrocatechols, and the sum of the dimethyl-nitrocatechols were substantially correlated with levoglucosan (r-values of 0.71, 0.66, and 0.65, respectively), consistent with their proposed origin from biomass burning. The nitro-aromatic compounds were also observed during the summer months, indicating a non-negligible usage of wood burning for domestic purposes at the site. The ch-pinene-related nitrooxy-organosulfates (MW 295) were detected in high concentrations during the winter period, but they were poorly correlated with the biomass burning tracers. All of the targeted species showed a clear seasonal variation with highest concentrations in winter, followed by autumn, spring, and summer. Based on the DHAA measurements, it is suggested that burning of softwood is likely an important source for the formation of all the nitro-organic compounds measured. (C) 2013 Elsevier Ltd. All rights reserved.

Organic compounds are important constituents of fine particulate matter (PM) in the troposphere. In this study, we applied direct infusion nanoelectrospray (nanoESI) ultrahigh resolution mass spectrometry (UHR-MS) and liquid chromatography LC/ESI-UHR-MS for the analysis of the organic fraction of PM1 aerosol samples Collected over a two week period at a boreal forest site (Hyytiala), southern Finland. Elemental formulas (460-730 in total), were identified With nanoESI-UHR-MS in the negative ionization mode and attributed to organic compounds with a molecular weight below 400. Kendrick Mass Defect, and Van Krevelen approaches were used to identify compound classes and mass distributions of the detected species. The molecular composition of the aerosols strongly varied between samples with different air mass histories. An increased number of nitrogen, sulfur, and highly oxygenated organic compounds was observed during the days associated with continental air masses. However, the samples with Atlantic air mass history were marked by a presence of homologous series of unsaturated and saturated C-12-C-20 fatty acids suggesting their marine origin. To our knowledge, we show for the first time that the highly detailed chemical composition obtained from UHR-MS analyses can be clearly linked to meteorological parameters and trace gases concentrations that are relevant to atmospheric oxidation processes. The additional LC/ESI-UHR-MS analysis revealed 29 species, which were mainly attributed to oxidation products of biogenic volatile compounds BVOCs (i.e., alpha,beta-pinene, Delta(3)-carene, limonene, and isoprene) supporting the results from the direct infusion analysis.

RATIONALE: A considerable fraction of atmospheric particulate fine matter consists of organosulfates, with some of the most polar ones originating from the oxidation of isoprene. Their structural characterization provides insights into the nature of gas-phase precursors as well as into formation pathways. METHODS: The structures of unknown polar organosulfates present in ambient particulate fine matter were characterized using liquid chromatography/(-)electrospray ionization mass spectrometry (LC/(-)ESI-MS), including ion trap MS(n) and accurate mass measurements, derivatization of the carbonyl group into 2,4-dinitrophenylhydrazones, detailed interpretation of the MS data, and in a selected case comparison of their LC and MS behavior with that of synthesized reference compounds. RESULTS: Polar organosulfates with molecular weights (MWs) of 156, 170, 184 and 200 were attributed to/or confirmed as derivatives of glycolic acid (156), lactic acid (170), 1,2-dihydroxy-3-butanone (184), glycolic acid glycolate (200), 2-methylglyceric acid (200), and 2,3-dihydroxybutanoic acid (200). In the case of the MW 184 compound an unambiguous assignment was obtained through synthesis of reference compounds. CONCLUSIONS: A more complete structural characterization of polar organosulfates that originate from isoprene secondary organic aerosol was achieved. An important atmospheric finding is the presence of an organosulfate that is related to methyl vinyl ketone, a major gas-phase oxidation product of isoprene. In addition, minor polar organosulfates related to crotonaldehyde were identified.

Aerosol samples were collected with a micro-orifice uniform deposit impactor in an aerodynamic diameter (AD) range of 0.5–10 μm in central Budapest, Hungary for 12 days. Aqueous aerosol extracts and atmospheric humic-like substances (HULIS) were obtained from the combined aerosol samples for each impactor stage. Water-soluble organic carbon (WSOC) and carbon in HULIS (HULIS-C) were measured in the samples with a total organic carbon analyzer. The analytical data were inverted into semi-smooth mass size distributions, and modal parameters were derived. The size distributions for both WSOC and HULIS-C consisted of three peaks: a coarse mode and two accumulation submodes. The geometric mean AD for the coarse mode was 6.4 μm for both WSOC and HULIS-C. Contribution of the coarse mode to the total concentration of WSOC and HULIS-C were substantial and similar for both components, i.e., approximately 20%. The splitting of the accumulation mode into condensation and droplet submodes was explained by water processing of aerosol particles in the air. The geometric mean ADs of the condensation submode for the WSOC and HULIS-C were 0.37 and 0.31 μm, respectively, and the droplet submode appeared at 1.72 and 1.22 μm, respectively. The condensation submode was larger than the droplet submode by similar ratios of 1.7–1.8 for both WSOC and HULIS-C. The relative concentrations of the two submodes were likely influenced by local meteorology, in particular by relative humidity, pollutant gases, and water uptake properties and aging of fine particles.

The aim of this study was to investigate the influence of the vertical position of a motorway on the pollutant concentrations in the vicinity of the motorway. Therefore, a near-road monitoring campaign was performed along two adjoining motorway stretches: one motorway at ground level and a motorway flyover. PM 2.5 and nitrogen oxides (NO, NO 2 and NO x ) were measured at both sides of the motorway on a 30-min resolution. In addition, EC (elemental carbon) was measured on both sides of the road on a daily basis using low volume samplers and thermal–optical transmission (TOT) analysis of filters. PNC (particle number concentration) was measured at one side. The measurement locations on each side of the road were located at 29 m and 102 m from the motorway at ground level and at 60 m and 120 m from the motorway flyover. Pollution roses, showed increased average concentrations in the direction of the road for nitrogen oxides and PM 2.5 . The impact of road traffic appeared to be higher at ground level compared to the flyover. The difference in concentration between both sides of the road for PM 2.5 , NO, NO 2 and NO x was analysed using linear mixed models. The concentration difference, which can be seen as the contribution of road traffic to the pollutant concentration, was calculated taking into account prevailing wind directions. The results indicate that taking into account confounding parameters (time of day, day of the week, distance to the road and wind speed), the contribution of the motorway traffic to pollutant concentrations is significantly higher when the motorway is at ground level. Furthermore, time of day and day of the week also have a significant effect on the concentration difference. The linear mixed model estimated a reduced road increment at the motorway flyover compared to the ground level motorway of 119 ppb for NO, 29 ppb for NO 2 and 3.5 μg m −3 for PM 2.5 . taking into account confounding parameters. The highest EC and PNC concentrations were measured downwind of the motorway at ground level.

Stable carbon isotope ratios in marine aerosol collected over the Southern Indian Ocean revealed δ13C values ranging from −20.0‰ to −28.2‰. The isotope ratios exhibited a strong correlation with the fractional organic matter (OM) enrichment in sea spray aerosol. The base-level isotope ratio of −20.0‰ is characteristic of an aged Dissolved Organic Matter (DOM) pool contributing a relatively homogeneous background level of DOM to oceanic waters. The range of isotope ratios, extending down to −28.2‰, is characteristic of more variable, stronger, and fresher Particulate Organic Matter (POM) pool driven by trophic level interactions. We present a conceptual dual-pool POM-DOM model which comprises a ‘young’ and variable POM pool which dominates enrichment in sea-spray and an ‘aged’ but invariant DOM pool which is, ultimately, an aged end-product of processed ‘fresh’ POM. This model is harmonious with the preferential enrichment of fresh colloidal and nano-gel lipid-like particulate matter in sea spray particles and the observed depleted δ13C ratio resulting from isotope equilibrium fractionation coupled with enhanced plankton photosynthesis in cold water (−2 °C to +8 °C). These results re-assert the hypothesis that OM enrichment in sea-spray is directly linked to primary production and, consequently, can have implications for climate-aerosol-cloud feedback systems.

From 30 June 2011 to 2 July 2012 PM10 aerosol samples were simultaneously taken every 4th day at four urban background sites in Flanders, Belgium. The sites were in Antwerpen, Gent, Brugge, and Oostende. The PM10 mass concentration was determined by weighing; organic and elemental carbon (OC and EC) were measured by thermal-optical analysis, the wood burning tracers levoglucosan, mannosan and galactosan were determined by gas chromatography/mass spectrometry, 8 water-soluble ions were measured by ion chromatography, and 15 elements were determined by a combination of inductively coupled plasma atomic emission spectrometry and mass spectrometry. The multi-species dataset was subjected to receptor modeling by PMF. The 10 retained factors (with their overall average percentage contributions to the experimental PM10 mass) were wood burning (9.5%), secondary nitrate (24%), secondary sulfate (12.6%), sea salt (10.0%), aged sea salt (19.2%), crustal matter (9.7%), non-ferrous metals (1.81%), traffic (10.3%), non-exhaust traffic (0.52%), and heavy oil burning (3.0%). The average contributions of wood smoke for the four sites were quite substantial in winter and ranged from 12.5 to 20% for the PM10 mass and from 47 to 64% for PM10 OC. Wood burning appeared to be also a notable source of As, Cd, and Pb. The contribution from wood burning to the PM10 mass and OC was also assessed by making use of levoglucosan as single marker compound and the conversion factors of Schmidl et al. (2008), as done in our previous study on wood burning in Flanders (Maenhaut et al., 2012). However, the apportionments were much lower than those deduced from PMF. It seems that the conversion factors of Schmidl et al. (2008) may not be applicable to wood burning in Flanders. From scatter plots of the PMF-derived wood smoke OC and PM versus levoglucosan, we arrived at conversion factors of 9.7 and 22.6, respectively. (C) 2016 Elsevier B. V. All rights reserved.

The ability of a complex model chain to simulate elemental carbon (EC) concentrations was examined. The results of the model chain were compared to EC concentration measurements made at several locations, every sixth day. Two measurement campaigns were taken into account, one in 2006–2007 and one in 2008–2009. The model results compare very well for both periods, with an R 2 of 0.74, a bias of 0.02 μg m −3 and a RMSE of 0.32 μg m −3 . Sensitivity analyses to different meteorology inputs and changing emissions from year to year were performed. The differences between the two measurement periods were also investigated. It is shown that somewhat more than half of these differences is due to meteorology. However, emission changes also play an important role.

Particle-induced X-ray emission (PIXE), ion chromatography (IC), and occasionally also instrumental neutron activation analysis (INAA) were used in combination for the analysis of atmospheric aerosol samples that were collected on Nuclepore polycarbonate filters. A comparison of the results enabled us to evaluate the matrix effects (i.e., particle size effects) of the PIXE analysis for the light elements and to assess the water-solubility and/or speciation of a number of elements (e.g., S, K, Ca). Results are presented from several measurement campaigns at urban and forested sites in Europe, whereby PM10 or PM2.5 filter samples were taken. From the PIXE and IC results for a 2003 summer campaign at the K-puszta site in Hungary, it was estimated that organosulphates could be responsible for 20% of the total sulphur concentration and 30% of the organic aerosol in PM10. The comparison of the IC and PIXE data for K and Ca from the various sites indicated that most of the Ca was water-soluble (the mineral dust Ca was presumably mostly present as calcite, and perhaps also in part as gypsum); in contrast, for K, only half of it was typically water-soluble, indicating that it was to a large extent associated with insoluble mineral dust. Exceptions, with almost fully water-soluble K, were found for samples that were substantially impacted by biomass burning.

In this study, we present liquid chromatographic and mass spectral data for predominant terpenoic acids formed through oxidation of α-pinene, β-pinene, d-limonene, and Δ3-carene that occur in fine forest aerosol from K-puszta, Hungary, a rural site with coniferous vegetation. Characterization of these secondary organic aerosol tracers in fine ambient aerosol is important because it allows one to gain information on monoterpene precursors and source processes such as oxidation and aging processes. The mass spectral data were obtained using electrospray ionization in the negative ion mode, accurate mass measurements, and linear ion trap tandem mass spectrometric experiments. Emphasis is given to the mass spectrometric differentiation of isobaric terpenoic acids, such as, e.g. the molecular weight (MW) 186 terpenoic acids, cis-pinic, cis-caric, homoterpenylic, ketolimononic, and limonic acids. Other targeted isobaric terpenoic acids are the MW 184 terpenoic acids, cis-pinonic and cis-caronic acids, and the MW 204 tricarboxylic acids, 3-methyl-1,2,3-butanetricarboxylic and 3-carboxyheptanedioic acids. Fragmentation pathways are proposed to provide a rational explanation for the observed isomeric differences and/or to support the suggested tentative structures. For the completeness of the data set, data obtained for recently reported lactone-containing terpenoic acids (i.e. terpenylic and terebic acids), related or isobaric compounds (i.e. norpinic acid, diaterpenylic acid acetate, and unknown MW 188 compounds) are also included, the rationale being that other groups working on this topic could use this data compilation as a reference.

Atmospheric aerosol was sampled at different humidity conditions using two 7-stage modified BLPI impactors. Dry particles were obtained at 20% RH. Wet particles were humidified inside diffuse humidifier with output 85-90% RH. 11 parallel intakes of dry and wet aerosol were done during winter campaign and 10 during summer one. The samples were processed by gravimetric method, ion chromatography and WSOC analysis. The average mass concentration sampled in winter was 34.4 μg/m 3 at dry, whereas the average mass concentration obtained at wet conditions was slightly higher 37.2 μg/m 3 . The average of summer concentration was 21.4 μg/m 3 at dry conditions, and 21.6 μg/m 3 at wet conditions. Theoretical mass-size distribution of wet aerosol determined from dry aerosol data was calculated using the most abundant hygroscopic inorganic anions SO 4 2- , NO 3 , Cl - , and WSOC fractions were only taken into account. Calculated distribution estimates the growth of particles due to water uptake and predicts the size distribution of wet aerosol. The growth factors based on Stokes and aerodynamic diameters were calculated. Measured differences in dry and wet size distributions of single species pointed to externally mixed particles and/or changes in aerosol composition during sampling.

Skeleton remains and soil samples, recovered from the central tomb of the Church of Our Lady, Bruges, were analyzed for their major, minor and trace element content by means of instrumental neutron activation analysis (INAA), particle induced X-ray emission (PIXE) and Rutherford back-scattering (RBS). The results indicated that the reddish brown patinaed surface layer of the skeleton remains had a lead content of the order of 8 to 241, whereas that in the onderlying normal looking bone tissue was only 0.6%. The soil samples, recovered from inside the skull also showed abnormally high lead contents. It is concluded that the lead in the bone is of exogenous origin, ultimately originating from the lead coffin in which the body was buried. It is further suggested that the high lead concentration in the surface layer of the skeleton may be responsible for its reddish brown colour.

Atmospheric aerosol samples in PM10 and PM2.5 size fractions were collected in parallel at a rural site in Morogoro during wet season in March and April 2006. All samples were analysed for the particulate matter mass, for organic, elemental, and total carbon (OC, EC, and TC), and for water-soluble OC (WSOC). The average PM10 and PM2.5 mass concentrations and associated standard deviations were 14 ± 13 μg/m3 and 7.3 ± 4 μg/m3 respectively. On average, TC accounted for 33% of the PM10 mass and 44% of the PM2.5 mass for the campaign. The average OC/PM percentage ratios were 27% and 33% in PM10 and PM2.5 size fractions respectively and a larger fraction of the OC was water-soluble. The observed low EC/TC mean percentage ratios of 10–14% respectively for PM10 and PM2.5 fractions indicate that the carbonaceous aerosol originates mainly from biogenic aerosols and/or biomass burning. A simple source apportionment approach was used to apportion the OC to biofuel and charcoal burning. On average, 93% of the PM10 OC was attributed to biofuel and 7% to charcoal burning in the 2006 wet season campaign. However, it is suggested that a contribution to the OC at Morogoro could also come from other natural biogenic matter, and/or biomass burning aerosols. The results for the sources of OC at Morogoro should therefore be considered with great caution.

Aqueous-phase oligomer formation from methylglyoxal, a major atmospheric photooxidation product, has been investigated in a simulated cloud matrix under dark conditions. The aim of this study was to explore an additional pathway producing secondary organic aerosol (SOA) through cloud processes without participation of photochemistry during nighttime. Indeed, atmospheric models still underestimate SOA formation, as field measurements have revealed more SOA than predicted. Soluble oligomers (n = 1–8) formed in the course of acid-catalyzed aldol condensation and acid-catalyzed hydration followed by acetal formation have been detected and characterized by positive and negative ion electrospray ionization mass spectrometry. Aldol condensation proved to be a favorable mechanism under simulated cloud conditions, while hydration/acetal formation was found to strongly depend on the pH of the system and only occurred at a pH3H4O2 units (72 Da) to the parent β-hydroxy ketone. Ion trap mass spectrometry experiments were performed to structurally characterize the major oligomer species. A mechanistic pathway for the growth of oligomers under cloud conditions and in the absence of UV-light and OH radicals, which could substantially enhance in-cloud SOA yields, is proposed here for the first time.

Ambient daytime and nighttime PM(10) and PM(2.5) samples were collected in parallel at a kerbside in Dar es Salaam in August and September 2005 (dry season) and in April and May 2006 (wet season). All samples were analyzed for the particulate matter mass, for organic, elemental, and total carbon (OC, EC, and TC), and for water-soluble OC (WSOC). The average PM(10) and PM(2.5) mass concentrations and associated standard deviations were 76+/-32microg/m(3) and 26+/-7microg/m(3) for the 2005 dry season and 52+/-27microg/m(3) and 19+/-10microg/m(3) for the 2006 wet season campaign. On average, TC accounted for 29% of the PM(10) mass and 49% of the PM(2.5) mass for the 2005 dry season campaign and the corresponding values for the 2006 wet season campaign were 35% and 59%. There was little difference between the two campaigns for the WSOC/OC ratios with the PM(2.5) fraction having higher ratios than the PM(10) fraction during each campaign. Also for EC/TC higher ratios were noted in PM(2.5) than in PM(10), but the ratios were substantially larger in the 2006 wet season than in the 2005 dry season. The large EC/TC ratios (means 0.22-0.38) reflect the substantial impact from traffic at Dar es Salaam, as was also apparent from the clear diurnal variation in OC levels, with higher values during the day. A simple source apportionment approach was used to apportion the OC to traffic and charcoal burning. On average, 70% of the PM(10) OC was attributed to traffic and 30% to charcoal burning in both campaigns. A definite explanation for the substantially larger EC/TC ratios in the 2006 campaign as compared to the 2005 campaign is not available.

The ionic composition of coarse, fine and total PM10 was investigated in aerosol samples collected from a kerbside in Dar es Salaam during the 2005 dry season and 2006 wet season. A “Gent” PM10 stacked filter unit sampler with sequential Nuclepore polycarbonate filters, providing coarse (8 μm) and fine (0.4 μm) size fractions, was deployed. The mean concentrations and associated standard deviation of fine, coarse and PM10 were, respectively, 17 ± 4, 52 ± 27, and 69 ± 29 μg/m3 during the 2005 dry season campaign and 13 ± 5, 34 ± 23 and 47 ± 25 μg/m3 for the 2006 wet season campaign. The higher PM mass concentrations during the dry season campaign are essentially due to soil dust dispersal, much biomass burning and temperature inversions. Chloride, Na+ and Mg2+ were the dominant ions in coarse fraction, indicating a significant influence of sea-salt aerosols. In the fine fraction, SO 4 2 - and NH 4 + and K+ were the most important ions. The mean equivalent PM2 NO 3 - concentration in the 2005 dry season campaign was two times higher than in the 2006 wet season campaign, probably due to reaction of NaCl (sea-salt) with HNO3 as a result of higher levels of NOx during the dry season and/or reduced volatilization of NH4NO3 due to lower temperature in the dry season. The results from our water-soluble ions study strongly suggests that biomass burning and secondary aerosols make a significant contribution to fine particulate mass in Dar es Salaam atmosphere. Thus, burning of waste and biomass are thought to be the major causes for the atmospheric particulate pollution in Dar es Salaam during the dry season.

Mass concentrations, mass size distributions, time series, and diet variations for organic tracers and major inorganic ions in aerosols from K-puszta, Hungary, during a 2003 summer period are reported. Emphasis was placed on alpha-/beta-pinene secondary organic aerosol (SOA) tracers comprising cis-pinic acid, 3-hydroxyglutaric acid, and 3-methyl-1,2,3-butanetricarboxylic acid. Only cis-pinic acid and the d-limonene SOA tracer 3-carboxyheptanedioic acid exhibited diet variations with highest concentrations at night. Malic acid was fairly well correlated with succinic and oxalic acid, pointing to a similar SOA formation process. No day-night variations were observed for the latter acids, suggesting that they are formed over relatively longtime scales. Of the ionic species sulfate, ammonium, and nitrate, only nitrate showed clear diet variations with highest concentrations at night. As to the size-segregated samples, the 2-methyltetrols were present in both the fine and coarse modes, while the C-5-alkene triols and the alpha-/beta-pinene SOA tracers were only associated with the fine mode. The ionic species sulfate, ammonium, and nitrate made up for, on average, 24, 10, and 2.6% of the PM2.5 mass, while organic matter was responsible for 47% of that mass. Isoprene and alpha-pinene secondary organic carbon (SOC) accounted, on average, for, respectively, 6.8 and at least 4.8% of the PM2.5 organic carbon, but the contribution of isoprene SOC was more pronounced during daytime (9.6%), whereas that of alpha-pinene SOC was largest at night (at least 6.0%).

Ambient daily PM10 aerosol samples were collected at two sites in Tanzania in May and June 2005 (during the wet season), and their chemical characteristics were studied. The sites were a rural site in Morogoro and an urban kerbside site in Dar es Salaam. A Gent PM10 stacked filter unit sampler with sequential Nuclepore polycarbonate filters, providing fine and coarse size fractions, and a PM10 sampler with quartz fibre filters were deployed. Parallel collections of 24 h were made with the two samplers and the number of these collections was 13 in Morogoro and 16 in Dar es Salaam. The average mass concentration of PM10 was 27 ± 11 μg/m3 in Morogoro and 51 ± 21 μg/m3 in Dar es Salaam. In Morogoro, the mean concentrations of organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were 6.8, 0.51, and 2.8 μg/m3, respectively. In contrast, higher mean concentrations (11.9, 4.6, and 3.3 μg/m3, respectively) were obtained for Dar es Salaam. At both sites, species and elements, such as black carbon, NH4+, non-sea-salt SO42−, K, and Ni (and at Dar es Salaam also V, As, Br, and Pb) were mainly present in the fine size fraction. The common crustal and sea-salt elements, including Na, Mg, Al, Si, Cl, Ca, Ti, Mn, Fe, and Sr, and also NO3− and P (and to a lesser extent Cu and Zn) were concentrated in the coarse particles. Aerosol chemical mass closure indicated that the PM10 mass in Morogoro consisted, on average, of 48% organic matter (OM), 44% crustal matter, 4% sea salt, and 2% EC, while in Dar es Salaam OM, crustal matter, sea salt, and EC represented 37%, 32%, 9%, and 9% of the PM10 mass. The contributions of the secondary inorganic aerosol (non-sea-salt sulphate, nitrate, and ammonium) were small, i.e., only 5% in total at each site. Carbonaceous materials and crustal matter were thus the most important components of the PM10 mass. It is suggested that biomass burning is a major contributor to the OM; at Dar es Salaam there is also a very substantial contribution from traffic. A source apportionment calculation indicated that 68% of the OC at this site originated from traffic exhaust versus 32% from charcoal burning. The crustal matter at Morogoro is likely mainly attributable to soil dust resuspension, whereas in Dar es Salaam it is likely mostly resuspended road dust.

The molecular composition of PM2.5 (particulate matter with an aerodynamic diameter2.5 microm) aerosol samples collected during a very warm and dry 2003 summer period at a mixed forest site in Jülich, Germany, was determined by gas chromatography/mass spectrometry in an effort to evaluate photooxidation products of biogenic volatile organic compounds (BVOCs) and other markers for aerosol source characterization. Six major classes of compounds represented by twenty-four individual organic species were identified and measured, comprising tracers for biomass combustion, short-chain acids, fatty acids, sugars/sugar alcohols, and tracers for the photooxidation of isoprene and alpha-/beta-pinene. The tracers for the photooxidation of alpha-/beta-pinene include two compounds, 3-hydroxyglutaric acid and 3-methyl-1,2,3-butanetricarboxylic acid, which have only recently been elucidated. The characteristic molecular distribution of the fatty acids with a strong even/odd number carbon preference indicates a biological origin, while the presence of isoprene and terpene secondary organic aerosol products suggests that the photooxidation of BVOCs contributes to aerosol formation at this site. The sum of the median concentrations of the isoprene oxidation products was 21.2 ng m(-3), while that of the terpene oxidation products was 19.8 ng m(-3). On the other hand, the high median concentration of malic acid (37 ng m(-3)) implies that photooxidation of unsaturated fatty acids should also be considered as an important aerosol source process. In addition, the occurrence of levoglucosan and pyrogallol indicates that the site is affected by biomass combustion. Their median concentrations were 30 and 8.9 ng m(-3), respectively.

Organic and elemental carbon (OC and EC) content in PM10 was studied at two sites in Prague, which were located in a suburb and in the downtown. Similar overall average levels were found for both species and also for the PM10 mass at the two sites (i.e., 5.5 and 4.8 μg/m3 for OC, 0.74 and 0.80 μg/m3 for EC, and 33 μg/m3 and 37 μg/m3 for the PM10 mass at the suburb and downtown site, respectively), but substantial differences were observed between the two sites in some seasons and/or meteorological situations. Approximately three times higher values were found for OC in winter compared to summer, with a higher winter/summer ratio for the suburban site. The differences for EC were smaller, but still, compared to summer, more than two times higher EC levels were observed during autumn at the suburban site and 1.5 higher EC levels in winter and autumn at the downtown site. The lowest OC to EC ratios at the suburban site were 3.4, while they were around 1.3 for the downtown site. It was found that the origin of the air masses had a major impact on the observed PM10 mass and OC levels, with largest concentrations noted for air masses recirculating over central Europe and arriving from southeastern Europe in winter. Trajectories coming from the west and northwest originating above the Atlantic Ocean and the Artic brought the cleanest air masses to the sites. For EC the largest difference between the two sites was observed for northwesterly winds during the non-heating season when the suburban site was upwind of Prague.

European publications dealing with source apportionment (SA) of atmospheric particulate matter (PM) between 1987 and 2007 were reviewed in the present work, with a focus on methods and results. The main goal of this meta-analysis was to provide a review of the most commonly used SA methods in Europe, their comparability and results, and to evaluate current trends and identify possible gaps of the methods and future research directions. Our analysis showed that studies throughout Europe agree on the identification of four main source types ( PM 10 and PM 2.5 ): a vehicular source (traced by carbon/Fe/Ba/Zn/Cu), a crustal source (Al/Si/Ca/Fe), a sea-salt source (Na/Cl/Mg), and a mixed industrial/fuel-oil combustion ( V / Ni / SO 4 2 - ) and a secondary aerosol ( SO 4 2 - / NO 3 - / NH 4 + ) source (the latter two probably representing the same source type). Their contributions to bulk PM levels varied widely at different monitoring sites, and showed clear spatial patterns in the cases of the crustal and sea-salt sources. Other specific sources such as biomass combustion or shipping emissions were rarely identified, even though they may contribute significantly to PM levels in specific locations.

Organosulfates of isoprene, alpha-pinene, and beta-pinene have recently been identified in both laboratory-generated and ambient secondary organic aerosol (SOA). In this study, the mechanism and ubiquity of organosulfate formation in biogenic SOA is investigated by a comprehensive series of laboratory photooxidation (i.e., OH-initiated oxidation) and nighttime oxidation (i.e., NO3-initiated oxidation under dark conditions) experiments using nine monoterpenes (alpha-pinene, beta-pinene, d-limonene, l-limonene, alpha-terpinene, gamma-terpinene, terpinolene, Delta(3)-carene, and beta-phellandrene) and three monoterpenes (alpha-pinene, d-limonene, and l-limonene), respectively. Organosulfates were characterized using liquid chromatographic techniques coupled to electrospray ionization combined with both linear ion trap and high-resolution time-of-flight mass spectrometry. Organosulfates are formed only when monoterpenes are oxidized in the presence of acidified sulfate seed aerosol, a result consistent with prior work. Archived laboratory-generated isoprene SOA and ambient filter samples collected from the southeastern U.S. were reexamined for organosulfates. By comparing the tandem mass spectrometric and accurate mass measurements collected for both the laboratory-generated and ambient aerosol, previously uncharacterized ambient organic aerosol components are found to be organosulfates of isoprene, alpha-pinene, beta-pinene, and limonene-like monoterpenes (e.g., myrcene), demonstrating the ubiquity of organosulfate formation in ambient SOA. Several of the organosulfates of isoprene and of the monoterpenes characterized in this study are ambient tracer compounds for the occurrence of biogenic SOA formation under acidic conditions. Furthermore, the nighttime oxidation experiments conducted under highly acidic conditions reveal a viable mechanism for the formation of previously identified nitrooxy organosulfates found in ambient nighttime aerosol samples. We estimate that the organosulfate contribution to the total organic mass fraction of ambient aerosol collected from K-puszta, Hungary, a field site with a similar organosulfate composition as that found in the present study for the southeastern U.S., can be as high as 30%.