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Mist cannon trucks have been widely applied in megacities in China to reduce the road dust. Their practical effect on controlling the formation of secondary organic aerosol and fine particles remains unknown. We characterized the chemical composition variations in PM2.5 collected on the road sides with the simulated operations of mist cannon truck and traditional sprinkling truck via Fourier transform ion cyclotron resonance mass spectrometry and ion chromatography. The mass concentrations of water-soluble organic carbon in PM2.5 showed a significant increase (62–70 %) after air spraying. Further, we found that secondary organic aerosols, particularly organic nitrates, increased significantly via the interactions of reactive gas-phase organics, atmospheric oxidants, and aerosol liquid water after air spraying, although the air spraying had a better effect on suppressing road dust than the ground aspersion. Moreover, the formation of PM2.5 in the road segment where the mist cannon truck passed was promoted, with an increase of up to 13 % in mass concentration after 25–35 minutes, on average. The application of mist cannon trucks undoubtedly worsens the road atmospheric environment and causes health hazards to walking residents. The overall results provide not only valuable insights to the formation processes of secondary organic aerosols associated with aerosol liquid water in the road environment but also management strategies to regulate the mist cannon truck operation in China.

Sugars and amino acids are major classes of organic components in atmospheric fine particles and play important roles in atmospheric processes. However, the identification of their sources in different regions is explored little. To characterize local primary sources (biomass burning, plant, and soil sources) and evaluate their contributions to the total sugar compound and amino acid (AA) pool in different regions, fine particulate matter samples were collected from the urban, rural, and forest areas in Nanchang, China. The concentrations and compositions of sugar compounds (anhydrosugars, primary sugars, and sugar alcohols), free amino acids (FAAs), and combined amino acids (CAAs) were analysed by gas chromatography–mass spectrometry (GC-MS) after silylation derivatization. Urban areas had significantly higher average Σ sugar concentration (317±139 ng m−3) than that of the rural (181±72 ng m−3) and forest (275±154 ng m−3) areas (p<0.05). Overall, the distribution pattern of sugar compounds and CAAs in PM2.5 was generally similar in three areas. Levoglucosan accounted for 24.4 %, 22.0 %, and 21.7 %, respectively, of the total sugar pool in the urban, rural, and forest areas. This suggests that plant and soil sources, as well as biomass burning (BB), provide important contributions to aerosol sugars and CAAs in three areas. In the urban area, the concentrations of anhydrosugars showed a positive correlation with combined Gly concentrations, but no correlation was found between these two compounds in the rural and forest areas, indicating that the urban area is mainly affected by local combustion sources. This conclusion was also supported by the positive correlation between levoglucosan and non-sea-salt potassium, only observed in the urban area (Lev=0.07 K++37.7,r=0.6,p<0.05). In addition, the average levoglucosan / mannosan (L/M) ratio in the urban area (59.9) was much higher than in the rural (6.9) and forest areas (7.2), implying BB aerosols collected in the urban area originated from lignite burning, while the type of biofuels used in the rural and forest areas is mainly softwood. The concentrations of sugar alcohols in the rural and forest areas were positively correlated with that of CAAs, which are abundant in the topsoil (r=0.53∼0.62,p<0.05), suggesting that the contribution of local topsoil sources is large in these two areas. In the rural and forest areas, the concentrations of primary sugars were positively correlated with those of combined CAA species abundant in local dominant vegetation. Our findings suggest that combining specific sugar tracers and chemical profiles of CAAs in local emission sources can provide insight into primary source characteristics, including the types of biofuels burned, the contribution of topsoil sources, and local vegetation types.

Sugars and amino acids are major classes of organic components in atmospheric fine particles and play important roles in atmospheric processes. However, the identification of their sources in different regions is less explored. To characterize local primary sources (biomass burning, plant and soil sources) and evaluate their contributions to the total sugar compounds and AAs pool in different regions, fine particulate matter samples were collected from the urban, rural and forest locations. The concentrations and compositions of sugar compounds (anhydrosugars, primary sugars and sugar alcohols), free amino acids (FAAs) and combined amino acids (CAAs) were analyzed. Overall, the distribution pattern of sugar compounds and CAAs in PM2.5 was generally similar among the urban, rural and forest locations. Moreover, the average contribution of sugar compounds and CAAs reflecting BB, plant and soil sources to the total sugar and CAA pool were consistent in all sampling locations. These suggest BB, plant and soil sources all have important contributions to aerosol sugars and CAAs in three locations. In the urban area, the concentrations of anhydrosugars showed a positive correlation with combined Gly concentrations, but no correlation was found between these two compounds in the rural and forest areas, indicating that the urban area is mainly affected by local combustion sources, while the rural and forest areas may be more influenced by long-transport BB source. In addition, the average L/M ratio in the urban location (59.9) was much higher than those in the rural (6.9) and forest locations (7.2), implying BB aerosols collected in the urban location originated from lignite burning while the type of biofuels used in the rural and forest locations is mainly softwood. The concentrations of sugar alcohols in the rural and forest locations were positively correlated with that of CAAs, which are abundant in the topsoil, suggesting that the contribution of local topsoil sources is large in these two locations. In the rural area, the concentrations of primary sugars were positively correlated with that of combined aspartic acid (a CAA specie abundant in grass, the dominant vegetation in the rural area), while in the forest area, primary sugars had good correlations with combined citrulline, lysine, ornithine, glutamic acid and serine (CAA species abundant in pine, dominant vegetation in the forest area), indicating that combining primary sugars with major CAA species in local dominant vegetations may identify local vegetation types. Furthermore, the nitrogen isotope of combined Gly and PMF model results demonstrated that the average contribution of combustion processes to total sugar compounds and CAAs pool in the urban and rural locations was higher than that in the forest location while primary biogenic sources showed a higher average contribution in the forest location than those in rural and urban locations. Our findings suggest that combining specific sugar tracers and chemical profiles CAAs in local emission sources can provide insight to primary sources characteristics including the types of biofuels burned, the contribution of topsoil sources and local vegetation types.

Nitrate (NO

Atmospheric ambient gaseous ammonia (NH3), the most abundant alkaline gas, affects public health and climate change through its key role in the formation of secondary aerosols via reactions with acidic gases. Estimation of the contributions of ammonia sources is very challenging in the urban atmosphere. Stable nitrogen isotope ratio (δ15N) measurements have shown that urban aerosol NH4+ and gaseous NH3 are derived from fossil fuel combustion-related (FF) sources, such as coal combustion, NH3 slip, and vehicle exhaust, and volatilization-related sources, such as agriculture and urban water volatilization. Biomass burning (BB) sources, especially residential biofuel, can produce vast quantities of NH3 and other pollutants and may greatly influence air quality and contribute to increased urban NH3 emissions. In the present study, we continually collected PM2.5 samples at three urban sites in Central China during autumn and analyzed the major water-soluble ions and δ15N values of aerosol NH4+. The concentrations of NH4+ increased as the temperature decreased close to winter, whereas the δ15N values did not show this pattern. According to the Bayesian model after isotope fractionation correction, FF sources contributed to 56.4 ± 17.1%, 46.4 ± 18.2%, and 51.8 ± 14.9% of aerosol NH4+ in Nanchang, Wuhan, and Changsha, respectively, throughout autumn. The contributions from BB sources were 34.5 ± 20.4%, 46.4 ± 21.4%, and 40.4 ± 17.4% for Nanchang, Wuhan, and Changsha, respectively. We also found the fraction of aerosol NH4+ from BB increased in all three cities from September to November 2017, which was likely caused by increased heating demands with the decrease in temperature during the season. Furthermore, BB was responsible for a severe haze event (maximum PM2.5 of 205.69 μg/m3) in Nanchang. These findings suggest government controls to improve air quality should include BB sources in addition to FF sources.

Combustion-derived black carbon (BC) is increasingly recognized as a significant pollutant that can have adverse effects on the atmospheric environment, human health, and regional climate. Fossil fuel combustion is the main source of BC, yet understanding of the relative contributions to BC from coal and liquid fuel combustion remains incomplete. Moreover, few studies have assessed the relative contributions based on long-term continuous daily field observations. This study adopted a Bayesian model of a three-dimensional array of a stable carbon isotope and the ratios of non-sea-salt K+ to BC and ΔBC/ΔCO of one year's daily observations (from September 1, 2017 to August 31, 2018) to constrain source apportionment of BC in Beijing (China). Results showed that both the BC and the carbon isotope concentrations exhibited strong seasonal variability, and that the annual BC concentration has decreased significantly in recent years. The Bayesian model results also revealed that the relative contributions from the combustion of coal, liquid fuel, and biomass were 42% ± 18%, 42% ± 18%, and 16% ± 11%, respectively, with a larger contribution from coal (liquid fuel) combustion in winter and spring (summer and autumn). The seasonal variation of source appointment was attributed to local and regional fuel combustion coupled with meteorological conditions. With increasing PM2.5 level, the BC concentration derived from biomass burning increased fastest, followed by that derived from coal combustion. But concentration of secondary inorganic ions increased faster than BC as PM2.5 increased.

High anthropogenic N loads and abundant bacteria are characteristic of highly contaminated urban rivers. To better understand the dispersal and accumulation of bacteria, we determined contents and isotopic compositions of suspended particulate organic matter (SPOM) and bacteria in a highly contaminated urban river (the Nanming) and effluents in winter and summer of 2013. Relative to SPOM, bacterial biomass in the river was depleted in 13C and 15N and its C/N ratio was lower (δ13C: − 33.2‰ ± 3.1‰; δ15N: − 1.5‰ ± 1.2‰; C/N: 4.8 ± 0.6), while effluents showed higher 13C and 15N contents and C/N ratios (δ13C: − 25‰ ± 2.1‰; δ15N: + 8.5‰ ± 1.1‰; C/N: 8.1 ± 1.2). Source recognition of SPOM was based on carbon isotopes because they are conservative and distinct between end-members (effluent detritus and bacterial biomass). Using a mixing model, bacterial biomass in the river was calculated to account for

Southwest China is the primary area for damming rivers to produce hydroelectric energy and store water. River damming has changed hydrodynamic, chemical, and biological processes, which are related to sinks and sources of greenhouse gases and carbon and nitrogen fluxes of different interfaces. Here, I provide an introduction to a river damming-related foundation, the National Key R&D Program of China (2016YTA0601000). Supported by the foundation, we carried out research on multi-processes/multi-interfaces of carbon and nitrogen biogeochemical cycles in a dammed river system and have produced important results, as presented in this issue of the journal.

Vertical profiles of PM

N and S contents in

Field investigation on the content of heavy metals in soils and three types of widely distributing compositae plants(

Haplocladium microphyllum moss samples were collected in Nanchang, China. Free amino acid (FAA) concentrations and N isotope compositions (δ

Major inorganic chemical ionic concentrations (Na+, Cl−, SO42−, Ca2+, Mg2+, K+, NH4+, NO3−) were determined in total suspended particulates (TSP) at Yongxing Island in the South China Sea (SCS), from March 2014 to February 2015. The annual average concentration of TSP was 89.6 ± 68.0 μg/m3, with 114.7 ± 82.1, 60.4 ± 27.0, and 59.5 ± 25.6 μg/m3 in cool, warm, and transition seasons, respectively. Cl− had the highest concentration, with an annual average of 7.73 ± 5.99 μg/m3, followed by SO42− (5.54 ± 3.65 μg/m3), Na+ (4.00 ± 1.88 μg/m3), Ca2+ (2.15 ± 1.54 μg/m3), NO3− (1.95 ± 1.34 μg/m3), Mg2+ (0.44 ± 0.33 μg/m3), K+ (0.33 ± 0.22 μg/m3), and NH4+ (0.07 ± 0.07 μg/m3). Concentrations of TSP and the major ions showed seasonal variations, higher in the cool season and lower in the warm and transition seasons, which were influenced by wind speed, temperature, relatively humidity, rain, and air masses. Back trajectories, concentration weighted trajectories (CWT), and positive matrix factorization (PMF) of chemical compositions were analyzed for source apportionment, source contribution, and spatio-temporal variation of major ions. Back trajectories and CWTs showed that air masses at Yongxing Island were mainly from the northeast, southwest, and southeast in the cool, warm, and transition seasons, respectively. Na+ and Cl− were mainly from sea salt, which made up 74 % and 82 %, respectively. Asian dust contributed 50 % of Ca2+ to the marine aerosols. Anthropogenic sources were very important for atmospheric aerosols over the island. Fossil fuel combustion (especially coal in Chinese coastal regions) was the important sources of NO3− (56 %) and SO42− (22 %). Biomass burning in Asia accounted for 41 % of K+. 69 % of NH4+ and 38 % of SO42− were of marine biogenic sources.

Rainwater samples were collected in the summer on "Shiyan 3" during the 2012 South China Sea Sectional Scientific Survey. The concentrations of anion and cation, and pH in precipitation were determined and backward trajectories of air mass were simulated to analyze the chemical characteristics of ions and examine the source of ions. The results indicated that the mean pH value of precipitation was 6.3, with 5.6 of minimal value in summer in South China Sea. The order of anion and cation abundance was Cl(-)S04(2-)NO3(-) and Na(+)Mg(2+)Ca(2+)K(+). Cl(-) was the major anion and Na(+) was the major cation, with concentrations of 2 637.5 microeq x L(-1) and 2095.5 microeq x L(-1), respectively, showing that they were the characteristics of marine atmospheric precipitation. There was a good linear relationship between each pair of 7 ions, with correlation coefficient above 0.9, suggesting that they may have a common source. However, the correlation coefficients were lower between NO3(-) and other ions than the others, suggesting that NO3(-) had more complex sources. The concentrations of Ca(2+) and K(+) in precipitation may be related to coral environment in South China Sea. The backward trajectories in 6 stations showed that the air mass was from south and southwest of South China Sea, without passing through above the continent. These results suggested that precipitation affected by human ion source can be ignored in summer in South China Sea.

This study analyzed the inorganic sulfur (SSO4) and total sulfur (ST) content as well as the isotopic signatures (delta34SSO4 and 834ST) in leaves of Pinus massoniana lamb. collected from Guizhou and Yunnan areas. The results indicated that the SSO4 and ST content in leaves at Guiyang areas was significantly higher than that at Yunnan areas, and the content of inorganic sulfur in the leaves was found to be directly related to the concentration of ambient sulfur dioxide, but no correlation was seen between the ST content and the ambient sulfur dioxide, showing the SSO4 content in leaves was more reliable to reflect the ambient sulfur input. The average value of delta34SSO4 in leaves at Guiyang areas ( -7. 22%o) was significantly lower than that at Yunnan areas(3. 85 per thousand) , which was related to the fact that the sulfur isotopic composition of coal at Guiyang areas is lower than that at Yunnan areas. The SSO4 and ST content in leaves around Kunming steel and Qujing power plant was inversely proportional to the distance from the factories, while around Kunming steel plant the value of 83SSO4 in leaves became more negative when the distance became larger while around Qujing power plant the value of 834Sso4 became more positive when the distance became larger, indicating that the SSO4 content and delta34SSO4, in leaves around Kunming steel and Qujing power plant were controlled by coal sources of atmospheric sulfur deposition.

In order to study the influence of atmospheric sulfur on soil sulfur, the forest surface soil samples and moss samples were collected in north areas of Jiangxi province. Contents and isotopes of sulfur in different forms (total sulfur, water-soluble sulfur, absorbed sulfur and organic sulfur) were determined. The average sulfur content of mosses was 0. 34% +/- 0. 20%. All of the delta34S values except at Fengcheng (-3. 31 per thousand) were positive, the average was 5.64 per thousand +/- 2. 23 per thousand. The average contents of soil total sulfur were between 189.0 mg.kg-1 and 793.5 mg.kg-1. The organic sulfur was the main sulfur form in surface soils and the contents of water-soluble sulfur were the lowest. The delta34S values of total sulfur were in the range of 4. 45 per thousand +/-10. 28 per thousand. The highest soil delta34S values were determined for organic sulfur and the delta34S values of water-soluble and absorbed sulfur were similar. The contents of soil total sulfur were much lower than those of the mosses. Except for organic sulfur (R = 0. 50, P0. 05) , the delta34S values of total sulfur, water-soluble sulfur and absorbed sulfur were all significantly correlated with those of moss sulfur (R0.7, P0. 01). These results indicated that atmospheric sulfur directly affected the total sulfur, water-soluble sulfur and absorbed sulfur, but not the organic sulfur.

Leaves of Platanus orientalis were collected since Mar. 2009 till Apr. 2010, in an urban area at Guiyang. After mass of experiments and analysis, we carried out constructing the temporal variation of foliar N% and delta15 N: both higher in Spring/Summer, lower in Autumn, no data of Winter because of leaf abscission. Results showed that foliar N% varied from 1.48% to 5.27%, with an annual average of 3.36%, while the average concentration of total N in rhizospheric soil was 0.29%. The foliar N% rose and fell relative to DIN in rainwater (range from 0.57 mg x L(-1) to 6.74 mg x L(-1)), indicating that the N% content in foliar tissue of plant was approximately proportional to atmospheric N inputs. The range of foliar delta15N were from 4.48 per thousand to 8.39 per thousand, with the average of 6.33 per thousand, much higher than the delta15N-NH4+ of rain water (-19.76 per thousand(-) -10.41 per thousand) and delta15TN of rhizospheric soil (3.19 per thousand +/- 1.04 per thousand). Besides, a good uniform correlation between foliar delta15N and delta15N-NH4+ of rain water were found. As synthesis of two main N sources, the more positive delta15N values of Platanus orientalis can be explained by isotopic fractionation during N uptake and basipetal translocation. These responses of both foliar N% and delta15N to atmospheric nitrogen deposition, revealed the potential value in using vascular leaves as bio-monitors for assessment of N deposition, furthermore, for prevention and control of air pollution in urban ecosystem.

Atmospheric N deposition and N sources in Jiangxi Province were investigated on the basis of the nitrogen concentrations and nitrogen isotope in epilithic mosses which collected from 11 cities of the province during 2009-2010. Mean nitrogen concentrations ranged from 2.46% to 3.48% and showed a significant regional difference. The highest was found in the northwestern of the province and the lowest in the southeastern, reflecting that the level of the atmospheric N deposition gradually decreased from the north to the south in the province. The higher N concentrations in urban mosses than in suburban mosses indicated that the urban areas received higher rates of nitrogen deposition than suburbs areas. Mosses 15N values varied from (-9.74 +/- 0.25) per thousand to (-1.96 +/- 1.30) per thousand. More negative delta15N values of urban mosses (-5.51 per thousand-9.74 per thousand) indicated that more NH3 was released from excretory wastes and sewage, while less negative delta15N values of suburban mosses (-4.81 per thousand-1.96 per thousand) suggested an important contribution from agricultural NH3 emission due to intensive fertilizer application. This research provides basic information for further study on the ecological and environmental effects of atmospheric N deposition.

A study of the continuous precipitation in Guiyang has been taken during October 30 and November 7. The results showed that the range of pH was between 3.65 and 7.20, and volume-weighted mean was 4.24. SO4(2-) was the main anion and volume-weighted mean was 119.06 microeq x L(-1), accounting for 80.63% of total anions. While Ca2+ was the main cation and volume-weighted mean was 48.87 microeq x L(-1), accounting for 48.16% of total cation and NH4+ was 38.38 microeq x L(-1), 37.82%. Good correlations between Mg2+, Ca2+, NH4+ and SO4(2-) are observed, which may exist as MgSO4, CaSO4 and (NH4)2SO4 in the rainwater in Guiyang City. Different ions of the atmosphere had different scavenged ways and rate in the precipitation process. In the initial stage of precipitation, the ions such as Mg2+, which were rich in coarse particles, were quickly removed from atmosphere. However the ions such as NH4+ and SO4(2-), which were rich in fine particles, could remain in the atmosphere for a longer time.

We investigated the carbon (C) and nitrogen (N) concentrations and isotopic signatures (delta 13C and delta15 N) in epilithic mosses collected from urban sites to rural sites along four directions at Guiyang area. Mosses C (34.47%-52.76%) decreased significantly with distance from urban to rural area and strongly correlated with tissue N (0.85%-2.97%), showing atmospheric N deposition has positive effect on C assimilation of epilithic mosses, higher atmospheric N/NHx deposition at urban area has improved the photosynthesis and C fixation of mosses near urban, which also caused greater 13C discrimination for urban mosses. Mosses delta 13C signatures (-30.69% per hundred - -26.96% per hundred) got less negative with distance from urban to rural area, which was also related to the anthropogenic CO2 emissions in the city, and these 12C-enriched CO2 sources would lead to more negative mosses delta 13C through enhancing the atmospheric CO2 concentration in urban area. Moreover, according to the characteristics of mosses C and delta 13C variations with distance, it is estimated that the influences of urban anthropogenic CO2 sources on plants was mainly within 20 km from city center. This study mainly focused on the factors regulating tissue C and delta 13C of mosses in city area and the interaction between C and N in mosses, the responses of mosses C and delta 13C to urban CO2 emission and atmospheric N deposition have been revealed, which could provide new geochemical evidences for the control of city atmospheric pollution and the protection of ecosystems around city.

Tissue N concentration and delta15 N signature in epilithic mosses were investigated along 4 directions from urban area to rural area at Guiyang city. Mosses N concentration ranged from 0.85% to 2.97% and showed significant decrease from urban area (2.24% +/- 0.32%) to suburb (1.27% +/- 0.13%), reflecting the level of atmospheric N deposition decreased away from urban. While slightly higher tissue N re-emerged at rural area beyond 25km (mean = 1.33%-1.75%), suggesting increased N deposition occurred in the rural area. Mosses delta15 N values varied from - 12.50 per thousand to - 1.39 per thousand characterized with getting less negative from urban to rural area. More negative delta15 N signatures of urban mosses (mean= - 8.87 per thousand(-) - 8.59 per thousand) mainly indicated the extensive NH3 sources released from excretory wastes and sewage, while mosses growing at farther suburb or rural area had less depleted delta15 N values (mean = - 3.83 per thousand(-) - 2.48 per thousand), indicating the large sources of agricultural NH3 emission connected with fertilizer application. Moreover, the pattern of mosses delta15 N variation in this study was opposite to areas where N deposition was dominated by oxidized form N (NO(x)) with generally positive mosses delta15 N. Accordingly, we concluded that reduced NH, was the dominant N form in atmospheric deposition at Guiyang area, which would be of great value for understanding the spatial variation and sources of atmospheric N deposition.