Journal of Atmospheric Chemistry最新文献

This study presents a yearlong data set of 28 medium-chain functionalised carboxylic acids (C5 to C10) in atmospheric aerosol particles (PM₁₀) from a German rural measurement station, which is analysed to obtain seasonal trends and evidences for possible sources of these rarely studied compounds. The analysed carboxylic acids were divided into four main groups: (I) functionalised aliphatic monocarboxylic acids, (II) functionalised aromatic monocarboxylic acids, (III) non-functionalised and functionalised aliphatic dicarboxylic acids, and (IV) aromatic dicarboxylic acids. A concentration maximum in summer was observed for aliphatic carboxylic acids, indicating mainly photochemical formation processes. For example, the highest mean summer concentrations were observed for 4-oxopentanoic acid (4.1?ng?m^?3) in group I and for adipic acid (10.3?ng?m^?3) in group III. In contrast, a concentration maximum in winter occurred for aromatic carboxylic acids, hinting at anthropogenic sources like residential heating. The highest mean winter concentrations were observed for 4-hydroxybenzoic acid (2.4?ng?m^?3) in group II and for phthalic acid (5.8?ng?m^?3) in group IV. For the annual mean concentrations, highest values were found for adipic acid and 4-oxopimelic acids with 7.8?ng?m^?3 and 6.1?ng?m^?3, respectively. The concentrations of oxodicarboxylic acids exceeded those of their corresponding unsubstituted form. Accordingly, straight-chain dicarboxylic acids might act as precursor compounds for their respective oxygenated forms. Similarly, unsubstituted monocarboxylic acids are possible precursors for functionalised aliphatic monocarboxylic acids. The present study contributes to the speciation of organic content on a molecular level of atmospheric particles, as well as giving hints for possible sources for these carboxylic acids.

Daily PM_2.5 samples were collected in Nanjing, a megacity in southeastern China, for a period of one-half of a month during every season from 2014~2015. Mass concentrations of nine water soluble inorganic ions (F^?, Cl^?, SO₄^2?, NO₃^?, Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺) were determined using ion chromatography to identify the chemical characteristics and potential sources of PM_2.5. The mass concentrations of daily PM_2.5 ranged from 31.0 to 242.9?μg?m^?3, with an annual average and standard deviation of 94.4?±?31.1?μg?m^?3. The highest seasonal average of PM_2.5 concentrations was observed during winter (108.5?±?31.8?μg?m^?3), and the lowest average was observed during summer (85.0?±?22.6?μg?m^?3). The annual average concentration of total water soluble inorganic ions was 39.82?μg?m^?3, accounting for 44.4% of the PM_2.5. The seasonal variation in water soluble inorganic ions in PM_2.5 reached its maximum during autumn and reached its minimum during spring. Sulfate, nitrate and ammonium were the dominant water soluble inorganic species, with their combined proportion of 82.0% of the total water soluble inorganic ions and 36.8% of the fine particles. Seasonal variations in aerosol acidity and chemical forms of secondary inorganic ions were discussed. The average ratio of NO₃^?/SO₄^2? was 0.95. According to the results of principal component analysis, secondary sources, burning processes, and airborne dust were the dominant potential sources of PM_2.5 in Nanjing.

Dissolved organic carbon (DOC) is an important organic pollutant in the air-water carbon cycle system, potentially influencing the global climate. In this study, 204 rainwater samples from five sampling stations in the Mt. Yulong region were synchronously collected from June to September in 2014. We comprehensively investigated the sources and wet deposition of DOC in summer precipitation. The average concentrations of DOC at five stations ranged from 0.74 to 1.31?mg?L^?1. The mass absorption efficiency (MAE) of rainwater DOC evaluated at 365?nm was 0.43?±?0.32?m²?g^?1. Backward trajectory analyses indicated that the southwest advection air parcel accounting for 46% of precipitation events, while the corresponding average concentration of rainwater DOC was 1.25?±?0.56?mg C L^?1. In addition to the local or regional contribution, large amount of atmospheric pollutants were transported from South Asia and Southeast Asia to the Mt. Yulong region, both of which had exerted great influence on the regional atmospheric environment. For the first time, the annual wet deposition of DOC in the Mt. Yulong region was estimated and determined to be 1.99?g C m^?2?year^?1. This is significant because the deposition of DOC on glaciers has great influence on surface albedo of snow and glacier melt. This study can bridge the gap of rainwater DOC research between the Mt. Yulong region and the southeast of Tibetan Plateau (TP), which has significant implications for better understanding the relationship of DOC deposition and glacial shrink in the TP.

Alkaline earth metals act as dominating acid-neutralizing species in atmosphere and hence, regulate the rain water chemistry significantly. In this contribution, concentrations of these metals (Mg, Ca, Sr and Ba) and other major ions in rain water samples, collected during south-west monsoon of year 2017, from a coastal location (Berhampur) in eastern part of India have been analyzed to trace their provenances and controlling factors. The chemical compositions of rain water reveal oceanic and continental supply of Mg and Sr to the site, whereas Ca and Ba are pre-dominantly supplied through continental sources. The dominancy of continental fluxes at this coastal site is mainly due to particulate fluxes from regional lithologies and favorable wind pattern for long-range transport from south-western/western directions. An inverse model involving chemical mass balance between rain water composition and its possible sources have been adopted in this study to quantify the source(s) contributions. These model results show that the continental Mg is mainly derived from long-range transport of mafic minerals from Deccan Traps (40?±?21%) with sub-ordinate contribution (15?±?6%) from regional lithologies. On average, about 70% of rain water Ca at Berhampur is derived from carbonates, whereas most of the Ba (~95%) is supplied from regional silicates (charnockites and khondalites). Owing to faster dissolution kinetics of these silicates with higher Ba content, the silicates contribute most of the rain water Ba concentration over this region. The median Ba content (29 nM) at this location is systematically higher than available literature Ba data for rain water worldwide (1-22 nM). The observed higher concentrations of Ba, a micronutrient, in rain water emphasize important role of regional lithology in the biogeochemical cycling of nutrients over the region via wet deposition.

The purpose of this paper is to develop an emission inventory of anthropogenic air pollutants and VOCs species in Sichuan Province. Based on the anthropogenic source activity data collected in different cities of Sichuan Province and the selected emission factors, the 1?km?×?1?km gridded atmospheric air pollutant emission inventory of 2015 was developed in the “bottom-up” and “top-down” approaches with the GIS technology. The results showed that the emissions of SO₂, NO_X, CO, PM₁₀, PM_2.5, BC, OC, VOCs and NH₃ from anthropogenic sources in Sichuan Province were 444.9 kt, 820.0 kt, 3773.1 kt, 1371.6 kt, 537.5 kt, 28.7 kt, 53.1 kt, 923.6 kt and 988.0 kt, respectively. Power plants and other industrial combustion boilers contributed more than 95% of SO₂ emission. Transportation, fossil fuel burning and industrial process contributed 54%, 23% and 20% of NOx emission respectively. Industrial process dominated by steel production and building material manufacturing contributed 20% of PM₁₀ emission and 34% of PM_2.5 emission. Fugitive dust dominated by road fugitive dust contributed 60% of PM₁₀ emission and 35% of PM_2.5 emission respectively. Biomass burning contributed 33% of BC emission and 51% of OC emission respectively. Solvent use of mechanical processing, building decoration, electronic equipment manufacturing, printing and furniture industry contributed 46% of VOCs emission. NH₃ mainly came from the emission of agricultural sectors, such as livestock breeding and N-fertilizer application, which contributed 70% and 25% of NH₃ emission respectively. The percentage of alkanes, alkenes, alkynes, aromatics, OVOCs, halohydrocarbons and other VOCs in the total VOCs emission were 17%, 9%, 2%, 23%, 22%, 4% and 23%, respectively. Ethene, m-xylene, toluene, propene, formaldehyde, o-xylene, 1, 2, 4-trimethyl benzene, 1-butene, p-xylene and ethyl benzene were the most critical chemical species for the formation of ozone pollution in Sichuan Province contributing 50% of the total OFP. Various air pollutants and OFP were mainly distributed in places with the densest population and well-developed agriculture and industry in Sichuan Basin and some areas of Panzhihua. The Chengdu Plain urban agglomerations, represented by Chengdu, Deyang and Mianyang, were the main areas with concentrated pollutant emissions in Sichuan Basin.

Changes in the frequency of precipitation as a result of a changing climate, as well as anthropogenic induced deposition of nitrogen (N), both have the potential to alter grassland productivity and diversity. Central U.S. weather patterns are dominated by three major air mass trajectories including regional sources from the Gulf of Mexico (marine tropical, Mt), the Pacific Northwest (mild pacific, mP), and the Desert Southwest (continental tropical, Ct). In this work, the Hybrid Single Particle Lagrangian Integrated Trajectory model was used to determine trends in the proportion of precipitation events from these air mass sources from 1983 to 2006 relative to Konza Prairie Biological Station (KPBS), KS. The annual volume-weighted mean (VWM) concentrations and wet deposition of a variety of precipitation dissolved solutes were linked to source regions north or south of KPBS. The proportion of precipitation events from Mt significantly increased, while the proportion of events from Ct and mP decreased significantly over the study period. The annual VWM concentrations of most solutes were typically higher from precipitation sourced to the north of KPBS. However, wet deposition of four ecologically relevant solutes (NH₄⁺, NO₃^?, H⁺_, and SO₄^?2) was higher from events from the southern region, likely due to higher precipitation amounts. The proportion of reduced N increased significantly over the study period but was not affected by source region despite the higher use of fertilizers for agriculture in the northern source region. Given the location of this site relative to three dominant air mass paths, future shifts in these patterns will likely impact wet nutrient deposition.

Hygroscopicity measurements of secondary organic aerosol (SOA) particles often show inconsistent results between the supersaturated and subsaturated regimes, with higher activity as cloud condensation nucleus (CCN) than indicated by hygroscopic growth. In this study, we have investigated the discrepancy between the two regimes in the Lund University (LU) smog chamber. Various anthropogenic SOA were produced from mixtures of different precursors: anthropogenic light aromatic precursors (toluene and m-xylene), exhaust from a diesel passenger vehicle spiked with the light aromatic precursors, and exhaust from two different gasoline-powered passenger vehicles. Three types of seed particles were used: soot aggregates from a diesel vehicle, soot aggregates from a flame soot generator and ammonium sulphate (AS) particles. The hygroscopicity of seed particles with condensed, photochemically produced, anthropogenic SOA was investigated with respect to critical supersaturation (s_c) and hygroscopic growth factor (gf) at 90% relative humidity. The hygroscopicity parameter κ was calculated for the two regimes: κ_sc and κ_gf, from measurements of s_c and gf, respectively. The two κ showed significant discrepancies, with a κ_gf /κ_sc ratio closest to one for the gasoline experiments with ammonium sulphate seed and lower for the soot seed experiments. Empirical observations of s_c and gf were compared to theoretical predictions, using modified K?hler theory where water solubility limitations were taken into account. The results indicate that the inconsistency between measurements in the subsaturated and supersaturated regimes may be explained by part of the organic material in the particles produced from anthropogenic precursors having a limited solubility in water.

This study reports for the first-time the ambient concentrations of HULIS mass (HULIS-OM, Humic-like substances) and HULIS-C (carbon) in PM₁₀ (particulate matter with aerodynamic diameter?≤?10?μm) from the Indo-Gangetic Plain (IGP at Kanpur, wintertime). HULIS extraction followed by purification and isolation protocol with methanol: acetonitrile (1:1?v/v) on HLB (Hydrophilic-Lipophilic Balanced) cartridge has been established. Quantification of HULIS-C was achieved on a total organic carbon (TOC) analyser whereas HULIS-OM was determined gravimetrically. Consistently high recovery (> 90%) of HULIS-C based on analysis of Humic standard (sodium salt of Humic acid) suggested suitability of our established analytical protocol involving solvent extraction, purification and accurate quantification of HULIS. HULIS-OM varied from 17.3–38?μg?m^?3 during daytime and from 19.8–40.6?μg?m^?3 during night in this study. During daytime the HULIS-OM constituted 20–30% mass fraction of OM_Total and 10–15% of PM₁₀ mass. However, a relatively low contribution of HULIS-OM has been observed during the night. This observation has been attributed to higher concentrations of OM and PM₁₀ in night owing to nighttime chemical reactivity and condensation of organics in conjunction with shallower planetary boundary layer height. Strong correlation of HULIS-C with K⁺_BB (R²?>?0.80) and significant day-night variability of HULIS-C/WSOC ratio in conjunction with air-mass back trajectories (showing transport of pollutants from upwind IGP) suggest biomass burning emission and secondary transformations as important sources of HULIS over IGP. High-loading of atmospheric PM₁₀ (as high as 440?μg?m^?3) with significant contribution of water-soluble organic aerosols (WSOC/OC: ~ 0.40–0.80) during wintertime highlights their plausible potential role in fog and haze formation and their impact on regional-scale atmospheric radiative forcing over the IGP.

Temporal variations in atmospheric hydrogen sulphide concentrations and its biosphere-atmosphere exchanges were studied in the World’s largest mangrove ecosystem, Sundarbans, India. The results were used to understand the possible contribution of H₂S fluxes in the formation of atmospheric aerosol of different size classes (e.g. accumulation, nucleation and coarse mode). The mixing ratio of hydrogen sulphide (H₂S) over the Sundarban mangrove atmosphere was found maximum during the post-monsoon season (October to January) with a mean value of 0.59?±?0.02?ppb and the minimum during pre-monsoon (February to May) with a mean value of 0.26?±?0.01?ppb. This forest acted as a perennial source of H₂S and the sediment-air emission flux ranged between 1213?±?276?μg?S?m^?2 d^?1(December) and 457?±?114?μg?S?m^?2 d^?1 (August) with an annual mean of 768?±?240?μg?S?m^?2d^?1. The total annual emissions of H₂S from the Indian Sundarban were estimated to be 1.2?±?0.6 Tg S. The accumulation mode of aerosols was found to be more enriched with non-sea salt sulfate with an average loading of 5.74?μg?m^?3 followed by the coarse mode (5.18?μg?m^?3) and nucleation mode (1.18?μg?m^?3). However, the relative contribution of Non-sea salt sulfate aerosol to total sulfate aerosol was highest in the nucleation mode (83%) followed by the accumulation (73%) and coarse mode (58%). Significant positive relations between H₂S flux and different modes of NSS indicated the likely link between H₂S, a dominant precursor for the non-sea salt sulfate, and non-sea sulfate aerosol particles. An increase in H₂S emissions from the mangrove could result in an increase in enhanced NSS in aerosol and associated cloud albedo, and a decrease in the amount of incoming solar radiation reaching the Sundarban mangrove forest.