Journal of Atmospheric Chemistry最新文献

In order to investigate particulate matter characteristics in the urban area of Naples, South of Italy, PM₁₀ and PM_2.5 chemical composition and properties were determined; in particular, ionic composition (Na⁺, K⁺, NH₄⁺, Mg²⁺, Ca²⁺, HCOO-, CH₃COO^?, Cl^?, NO₂^?, NO₃^?, SO₄^2?, C₂O₄^2?) and concentration of specific metals (Pb, Cd, Cu and Zn) were evaluated in association with an air masses trajectories study. Information on major ions was used to conduct the ionic balance and to evaluate sea salt and non-sea salt contributions; furthermore, the study on metals concentration allowed to distinguish the contribution of anthropic sources while their chemical behaviour (solubility and leachability) was considered in order to highlight the presence of different chemical forms. In the period of interest (June 2015), daily averages PM concentrations were below the limit of 25?μg/m³ for PM_2.5 and 50?μg/m³for PM₁₀; moreover, for both fractions, the most abundant ionic species was SO₄^2?followed by NO₃^?. Ionic balance indicated that non-sea salt contribution accounted for the great part of Ca²⁺, SO₄^2? and K⁺ while secondary inorganic aerosol accounted for about 5% of total ionic fraction. As expected, the most abundant metal was zinc (about 41?ng/m³ and 44?ng/m³in PM_2.5 and PM_10, respectively), while cadmium, copper and lead were at very low concentrations, in the range of 0.01–0.47?ng/m³; leachability reached values of 40% for copper in both PM fractions, in contrast with zinc that showed the lowest leachability, corresponding to 6% for PM_2.5 fraction. The study on air masses trajectories indicated a change on ionic composition and chemical properties, varying from a condition with air masses coming from Eastern Europe, characterised also by higher concentrations of both PM_2.5 and PM₁₀, a prevalence of secondary aerosol and metals showing minor solubility and leachability, to a condition with air masses coming from North-west region, with characteristics opposed to the previous ones.

A recent paper reported GCxGC-TOFMS analysis used for the first time in southern Africa to tentatively characterise and semi-quantify ~1000 organic compounds in aerosols at Welgegund – a regional background atmospheric monitoring station. Ambient polar organic aerosols characterised are further explored in terms of temporal variations, as well as the influence of meteorology and sources. No distinct seasonal pattern was observed for the total number of polar organic compounds tentatively characterised and their corresponding semi-quantified concentrations (sum of the normalised response factors, ∑NRFs). However, the total number of polar organic compounds and ∑NRFs between late spring and early autumn seemed relatively lower compared to the period from mid-autumn to mid-winter, while there was a period during late winter and early spring with significantly lower total number of polar organic compounds and ∑NRFs. Relatively lower total number of polar organic compounds and corresponding ∑NRFs were associated with fresher plumes from a source region relatively close to Welgegund. Meteorological parameters indicated that wet removal during late spring to early autumn also contributed to lower total numbers of polar organics and associated ∑NRFs. Increased anticyclonic recirculation and more pronounced inversion layers contributed to higher total numbers of polar organic species and ∑NRFs from mid-autumn to mid-winter, while the influence of regional biomass burning during this period was also evident. The period with significantly lower total number of polar organic compounds and ∑NRFs was attributed to fresh open biomass burning plumes occurring within proximity of Welgegund, consisting mainly of volatile organic compounds and non-polar hydrocarbons. Multiple linear regression substantiated that the temporal variations in polar organic compounds were related to a combination of the factors investigated in this study.

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.