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In order to clarify the concentration levels and sources of the water-insoluble amino acids (WIAA) in aerosols that have been received little attention in previous studies and to discuss their potential impact on nitrogen deposition, the WIAA in the coarse-mode (d = 2.0–10 μm) and fine-mode (d < 2.0 μm) aerosols were measured at a forested site in Japan together with the water-soluble free and combined amino acids. The sum of the WIAA showed more than a 6-times higher concentration than that of the water-soluble amino acids in the coarse-mode range and a similar concentration to that in the fine-mode range, which suggests a significant contribution of the WIAA to the amino acids pool in aerosols. The WIAA were predominantly partitioned into the coarse-mode range. The concentration of the coarse-mode WIAA was the highest in the summer and a strong correlation was found between the coarse-mode WIAA and nss-K+ concentrations. These results suggest that plant debris and the associated materials are important sources for the coarse-mode WIAA and the increase in the suspension of these particulate materials caused the enhancement of the WIAA in the summer. Remarkably higher concentrations of the coarse-mode WIAA than the water-soluble amino acids would be caused by these particulate materials. In the fine-mode range, on the other hand, the concentration of the WIAA was the highest in the spring and strongly correlated with the fine-mode nss-K+ concentrations. The fine-mode WIAA would be mainly derived from the biomass burning particles. The coarse-mode WIAA were estimated to significantly contribute to the dry deposition flux of the total nitrogen. The present study implies a potential impact of the WIAA in the coarse aerosols on nitrogen deposition. • A significant part of amino acids in aerosols was water-insoluble amino acids (WIAA). • The WIAA in aerosols were mainly partitioned into the coarse-mode range. • The coarse-mode WIAA were derived from plant debris and the associated materials. • The fine-mode WIAA were derived from biomass burning particles by Asian outflow. • The WIAA significantly contributed to the dry deposition flux of the total nitrogen. [ABSTRACT FROM AUTHOR]

Globally water‐soluble organic nitrogen (WSON) accounts for about one third of water‐soluble total nitrogen in atmospheric deposition, yet the key factors influencing WSON deposition remain uncertain. In the present study, precipitation and aerosol samples were collected during 2016–2018 at a forest site in the Pearl River Delta, south China. Rainwater WSON concentrations were found to elevate significantly during fall, and wet deposition of WSON during fall could account for about 50% of its annual total wet deposition. The wet deposition and rainwater concentrations of K+ and levoglucosan, which are tracers for biomass burning emissions, also increased substantially during fall. The average WSON/water‐soluble total nitrogen ratio in precipitations (0.48) was over two times higher than that in aerosols (0.20) during fall, while during other seasons, the ratios in precipitations (0.17) and in aerosols (0.19) were comparable. Moreover, concentrations of WSON in rainwater, unlike that of inorganic N, did not decrease significantly with the increase of precipitation amount during fall. These results suggested that enhanced biomass burning during fall (harvest season) might be an important source of in‐cloud WSON, and in‐cloud scavenging, instead of below‐cloud washout, likely contributed remarkably to the wet deposition of WSON. Key Points: Wet deposition of WSON increased significantly during fall with elevated WSON concentrations and WSON/WSTN ratios in rainwaterWet deposition of WSON was largely attributed to in‐cloud scavengingBiomass burning in the harvest season was a significant source of in‐cloud WSON [ABSTRACT FROM AUTHOR]

China is considered one of the nitrogen deposition hotspots in the world. Measurements to date have focused mainly on inorganic nitrogen, organic nitrogen and the size distribution of particulate nitrogen has yet to be studied. Lack of dry deposition observations imposes a reliance on models, resulting in a much larger uncertainty relative to wet deposition which is routinely measured. In this study, dry and wet organic and inorganic nitrogen deposition were comprehensively measured in Nanjing in 2019, and nitrogen species in size-segregated particles were investigated. Total annual nitrogen deposition flux was up to 29.96 kg N ha−1 yr−1 in Nanjing, with wet deposition contributed slightly more (51.90%) to total deposition than dry deposition (48.10%). Observations revealed that reduced nitrogen (NH x = NH 3 + NH 4 +) contributed 65.49% of the total inorganic nitrogen deposition budget, which implied that the control of reduced N in urban environments is needed to improve local air quality. Dry deposition of ammonia played an especially key role in dry deposition, contributing from 18.17% to 55.91% in different seasons. The deposition flux of water-soluble organic nitrogen (WSON) dominated by wet deposition, with the wet WSON about 4.6 times higher than that of dry deposition and contributed 41.18% of the wet nitrogen deposition. The wet N deposition in summer was significantly higher than in the other three seasons. The seasonal patterns in dry deposition were driven mostly by seasonal concentration patterns. The highest deposition of ammonia occurred in summer, while the deposition of nitrogen dioxide, particulate ammonium and nitrate peaked in winter. The maximum dry and wet WSON deposition appeared in autumn. Higher NH 4 + concentration almost distributed in each size bin and centered in ranges of 0.18–1.0 μm, while higher NO 3 − concentration scattered in particle size ranges of 1.8–5.6 μm and 0.18–1.0 μm. • A comprehensive observation of reactive nitrogen was conducted in Nanjing. • Total annual nitrogen deposition flux was up to 29.96 kg N ha−1 yr−1 in Nanjing. • Wet deposition contributed slightly more (51.90%) to total deposition. • Reduced nitrogen contributed 65.49% of the TIN deposition budget. • The deposition of WSON dominated by wet deposition and contributed 41.18%. [ABSTRACT FROM AUTHOR]

Water-soluble organic nitrogen (WSON) in fine particulate matter (PM2.5) was determined at urban coastal environments in China based on 1-year measurement. The WSON concentrations were in a range of 14.3–257.6 nmol N m−3 and accounted for 22.0–61.2% of the water-soluble nitrogen (WSN) in composition. The average total concentration of free amino acid (FAA) was 1264.5 ± 393.0 pmol m−3, which was lower than those in continental urban cities but nevertheless comparable to the rural area of Pearl River Delta (PRD) in China. The total quantified amines and amino compounds ranged from 223.8 to 806.0 pmol m−3 in which methylamine, ethylamine, and ethanolamine were the most abundant compounds. The average concentration of urea was 7.8 ± 3.0 nmol m−3 and at least one order of magnitude higher than those in marine and rural areas but comparable to other continental cities in China during non-dust period. Summer showed the highest average concentration of WSON (95.0 ± 66.6 nmol N m−3) and composition in WSN (49.3%) compared to other seasons (27.9–37.0%). The results were consistent with previous findings that the inorganics can contribute more than the organics in secondary aerosol formation. There were no distinctive seasonal variations of organic compositions of FAA, amine and amino compounds, and urea. This observation was possibly attributed to a mix of original sources in urban and different prevailing wind directions. Fair correlations (r < 0.4) between WSON compounds and atmospheric oxidants [ozone (O3) and nitrogen oxides (NOx)] suggest that biogenic oxidation is possibly not a major contributing factor in atmospheric coastal urban location. [ABSTRACT FROM AUTHOR]

Abstract A simultaneous observation of the water-soluble organic nitrogen (WSON) in the gaseous and particulate phases was conducted at a forested site in Japan for two years to clarify the generation mechanism and possible sources of the gaseous and particulate WSON. The concentration of the WSON in the aerosols was 0.070 μg m−3 on average, ranging from the concentration below the detection limit (DL) to 0.302 μg m−3. A large portion (about 73%) of the particulate WSON was distributed in the fine-mode range (d < 2.0 μm). The concentration of the gaseous WSON was 0.041 μg m−3 on average, ranging from the concentration below the DL to 0.195 μg m−3. About 37% of the atmospheric WSON was distributed in the gas phase, and about 59% of the gaseous WSON was basic. The coarse-mode (d = 2.0–10 μm) WSON showed an unclear seasonal trend, but increased in the summer. Its concentration showed a significant correlation only with the WSOC concentration among the measured species in the coarse aerosols. Suspended organic materials from primary sources, such as plant debris, would be a possible source for the coarse-mode WSON. The WSON in the fine-mode range showed a clear seasonality with enhanced concentrations from the spring to summer. The fine-mode WSON concentration showed a strong correlation with the acidity of the fine particles and the concentration of the gaseous basic WSON, suggesting the secondary production of the WSON in the acid fine particles from the gaseous basic WSON. The basic WSON in the gas phase showed a similar seasonal trend with the gaseous ammonia and strongly correlated with the temperature, which suggests the temperature dependent-volatilization of the gaseous basic WSON species from terrestrial vegetation and/or soil. The seasonal trend of the gaseous acid WSON was unclear, and its concentration did not show significant correlations with any parameters. The possible source and chemical forms of the gaseous acid WSON cannot be deduced at the present time. Highlights • About 73% of the WSON in the aerosols was distributed in the fine-mode range. • About 59% of the gaseous WSON was basic species. • Possible source of the coarse-mode WSON is primary emissions, such as plant debris. • Secondary production from the gaseous basic WSON is the source of the fine-mode WSON. • The gaseous basic WSON would be derived from the terrestrial vegetation and/or soil. [ABSTRACT FROM AUTHOR]

Abstract Simultaneous measurements of the water-soluble organic nitrogen (WSON) in the aerosols and rainwater were conducted to clarify the deposition pathway of the atmospheric WSON. In the aerosols, about 10% of the water-soluble total nitrogen (WSTN) was in an organic form, and a large portion (about 81% on average) of the WSON was distributed in the fine-mode range. Concentrations of the fine-mode WSON were associated with the acidity of the fine particles, suggesting the secondary production of the WSON in the acid fine particles. On the other hand, it was suggested that the coarse-mode WSON was derived from bio-particles, such as plant debris, although its concentrations were low and widely scattered. Dry deposition amounts of the WSON estimated from the concentrations and dry deposition velocities of the particulate WSON suggested that almost all of the dry deposition of the particulate WSON was derived from the coarse-mode particles. The contribution of the fine-mode particles to the dry deposition was negligible. About 10% of the WSTN in the bulk precipitation was in an organic form. The bulk deposition amounts of the WSON were largely dependent on the rainfall amounts and coarse-mode WSON concentrations. Although about 30% of the WSON in the bulk deposition was from the dry deposition, the wet deposition significantly contributed to the WSON deposition, especially in the rainy season. Wet deposition is the major removal process of WSON from spring to autumn; however, in winter, dry and wet deposition are comparable. Highlights • About 10% of the WSTN in the aerosols was in an organic form. • The WSON in fine particles was associated with the acidity of the particles. • About 10% of the WSTN in the bulk precipitation was in an organic form. • Almost all of the dry deposition of the WSON was derived from the coarse particles. • Wet deposition is a major process for the WSON deposition. [ABSTRACT FROM AUTHOR]

To estimate dry deposition flux of atmospheric water-soluble nitrogen (N), including ammonium (NH4+), nitrate (NO3−), and water-soluble organic nitrogen (WSON), aerosol samples were collected over the subarctic western North Pacific Ocean in the summer of 2016 aboard the Korean icebreaker IBR/V Araon. During the cruise, concentrations of NH4+, NO3−, and WSON in bulk (fine + coarse) aerosols ranged from 0.768 to 25.3, 0.199 to 5.94, and 0.116 to 14.7 nmol m−3, respectively. Contributions of NH4+, NO3−, and WSON to total water-soluble N represented ~74%, ~17%, and ~9%, respectively. Water-soluble N concentrations showed a strong gradient from the East Asian continent to the subarctic western North Pacific Ocean, indicating that water-soluble N species were mainly derived from anthropogenic or terrestrial sources. During sea fog events, coarse mode NO3− was likely to be scavenged more efficiently by fog droplets than fine mode NO3−; besides, WSON was detected only in fine mode, suggesting that there may have been a significant influence of sea fog on WSON, such as the photochemical conversion of WSON into inorganic N. Mean dry deposition flux for water-soluble total N (6.3 ± 9.4 µmol m−2 d−1) over the subarctic western North Pacific Ocean was estimated to support a minimum carbon uptake of 42 ± 62 µmol C m−2d−1 by using the Redfield C/N ratio of 6.625.

In order to clarify the production process for the particulate WSON in the maritime atmosphere, measurements of the WSON and the associated species in the aerosols were conducted at the coastal site on Rishiri Island near the northern tip of Japan. The mean concentration of the WSON in the aerosols was 0.077 μg m −3 , which was within the previous measurements from the remote or rural clean sites. The WSON accounted for about 13% of the WSTN in the aerosols, and about 90% of the WSON was detected in the fine-mode range (d < 2 μm). The WSON in both mode ranges was not associated with the air mass origin. The fine-mode WSON was correlated with nss-SO 4 2- whether nss-SO 4 2- was derived from anthropogenic or marine biogenic sources, suggesting that the WSON in the fine-mode range would be produced by the secondary processes in the acid particulate phase. EC and nss-K + , on the other hand, were not associated with the WSON in the fine-mode range, suggesting that the primary emissions from fossil fuel and/or biomass combustion are not important sources for the WSON. The coarse-mode WSON was not associated with any species. Negligible influence of dust particles and plant debris on coarse particle would cause very low concentrations of the WSON in the coarse-mode range. [ABSTRACT FROM AUTHOR]

The WSON in the gas phase and aerosols were simultaneously measured by the denuder–filter pack method. Approximately 33 ± 18% of the WSON in the atmosphere existed in the gas phase. A large portion (approximately 76 ± 33%) of the gaseous WSON collected in the present sampling method was occupied by basic species. The gaseous basic and acid WSON showed about one-sixth of the nitrogen concentrations of the gaseous NH3 and HNO3, respectively. These results indicate that the gaseous WSON is also an important fixed nitrogen species in the atmosphere.

The South China Sea (SCS) is one of the world’s largest oligotrophic marginal seas. Increases in biomass and primary production in the surface layer of the northern SCS are affected by anthropogenic aerosol use among north Asian peoples. The seasonal variation of dry deposition and its contribution to new production in the ocean are vital to determining the effect that such dry deposition has on the biogeochemical cycle of the SCS. This study collected 240 samples of total suspended particles at Dongsha Island in the northern SCS from April 2007 to March 2009; the major ions and water-soluble nitrogen species in the samples were analyzed. The analysis results indicated that the concentration distributions of major water-soluble ions and nitrogen species in total suspended particles exhibited significant seasonal (source) variation. The north-east monsoon seasons (autumn to spring) brought relatively high concentrations because most air masses during this period arrived from the northern continental region. We found that the concentration of nitrogen species shows a latitude distribution, gradually decreasing from north to south. In addition, this study also discovered that the ratio of organic nitrogen to total dissolved or water-soluble nitrogen also varies in a similar manner, resulting in a concentration of 30% for those south of 30° N. Aerosols at Dongsha Island mainly comprised sea salt; however, significant chloride depletion was observed during the north-east monsoon season. The molar ratio of NH4+ to non–sea salt (NSS) sulfate (nss-SO42−) was 0.8, indicating that the amount of artificially produced NH4+ in the region was insufficient for reaction with nss-SO42−. Therefore, NH4+ was mainly present in the form of NH4HSO4. The fluxes of water-soluble inorganic nitrogen (WSIN) and water-soluble organic nitrogen (WSON) within the region were 23 ± 13 and 27 ± 15 mmol m−2 y−1, respectively. The new production converted from atmospheric water-soluble nitrogen species in the northern SCS was estimated to be 0.52–0.81 mmol C m−2 d−1. This flux made about 5.6–8.7% (the global average was about 3.5%) contribution to the primary production (9.24 mmol C m−2 d−1) of the SCS surface water. This result indicates that the ocean’s external nitrogen supply, provided by anthropogenic aerosols, is vital for the biogeochemical cycle in Asian marginal seas, particularly the northern SCS.

In order to evaluate the positive and negative artifacts in the measurements of the water-soluble organic nitrogen (WSON) in the aerosols by filter sampling, comparative experiments between the filter sampling and denuder-filter sampling were conducted during both the warm and cold seasons. The results suggest that the traditional filter sampling underestimates the concentrations of the particulate WSON due to its volatilization loss, but this effect on the ratio of the WSON to the water-soluble total nitrogen (WSTN) was small probably because inorganic nitrogen species were also lost during the filter sampling. Approximately 32.5% of the WSON in the PM 2.5 was estimated to be lost during the filter sampling. The denuder–filter sampling also demonstrated the existence of the WSON in the gas phase with approximately quarter concentrations of the WSON in the PM 2.5 . On the other hand, the filter sampling would overestimate the gaseous WSON concentration due to the loss of the WSON from the aerosol collection filter. [ABSTRACT FROM AUTHOR]

Stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope ratios were measured for total carbon (TC) and nitrogen (TN), respectively, in aerosol (TSP) samples collected at Cape Hedo, Okinawa, an outflow region of Asian pollutants, during 2009–2010. The averaged δ 13 C and δ 15 N ratios are −22.2‰ and +12.5‰, respectively. The δ 13 C values are similar in both spring (−22.5‰) and winter (−22.5‰), suggesting the similar sources and/or source regions. We found that δ 13 C from Okinawa aerosols are ca. 2‰ higher than those reported from Chinese megacities probably due to photochemical aging of organic aerosols. A strong correlation ( r = 0.81) was found between nss-Ca and TSP, suggesting that springtime aerosols are influenced from Asian dusts. However, carbonates in the Asian dusts were titrated with acidic species such as sulfuric acid and oxalic acid during atmospheric transport although two samples suggested the presence of remaining carbonate. No correlations were found between δ 13 C and tracer compounds (levoglucosan, elemental carbon, oxalic acid, and Na + ). During winter and spring, coal burning is significant source in China. Based on isotopic mass balance, contribution of coal burning origin particles to total aerosol carbon was estimated as ca. 97% in winter, which is probably associated with the high emissions in China. Contribution of NO 3 − to TN was on average 45% whereas that of NH 4 + was 18%. These results suggest that vehicular exhaust is an important source of TN in Okinawa aerosols. Concentration of water-soluble organic nitrogen (WSON) is higher in summer, suggesting that WSON is more emitted from the ocean in warmer season whereas inorganic nitrogen is more emitted in winter and spring from pollution sources in the Asian continent. [ABSTRACT FROM AUTHOR]

In the last decades, there has been an increasing interest in the presence of amino acids in atmospheric aerosols, either free or in combination (e.g., proteinaceous compounds). The fact that these compounds play an important role in the chemistry and physics of air particles and atmosphere, in atmosphere/biosphere nutrient cycling, and have a direct impact in human health has encouraged further studies. The diversity in origin, type, and ambient concentrations of these amino compounds considerably complicates, thus indicating their environmental impact. Studies for the determination of amino acids in the atmosphere are extremely diverse, encompassing an array of different analytical methodologies; however, it is not possible to conduct a comparative study of these methods. In this critical review, we evaluate and compare the procedures involved in the analytical methods and studies developed thus far for the identification and quantification of amino acids in different ambient particle sizes and in different atmospheric environments (i.e., background/pristine, rural, and urban environments). [ABSTRACT FROM AUTHOR]

In recent years growing evidence has shown that organic nitrogen (ON) constitutes a significant fraction of the nitrogen budget in particulate matter (PM). However, the composition and sources of ON in Chinese PM are not clear to date due to the lack of field measurements and receptor modeling interpretations. In this study, water-soluble ON (WSON), free amino acids (FAAs) and primary amines, together with water-soluble ionic species and carbonaceous components, were quantified in PM 2.5 collected in Xi'an, China from 2008 to 2009. The yearly average WSON concentration (300 nmol N m −3 , ranging from 29 to 1250 nmol N m −3 ) was one order of magnitude higher than that reported in other urban and rural regions in U.S. A total of 24 organic nitrogen species were determined, with an average total concentration of 2180 pmol m −3 , which account for 1.2% of the WSON in PM 2.5 . Glycine, β-alanine and methylamine were the most abundant protein type amino acid, non-protein type amino acid and primary amine, respectively, contributing to 21.1%, 5.2% and 20.6% of the total quantified organic nitrogen species (TONS). Strong linear correlations (Pearson's correlation) (r = .72, p < 0.001 ) between WSON and one of biomass burning tracer (K + ) potentially indicate the contribution from biomass burning (especially in spring and fall) and the correlation (r = .76–.87, p < 0.001 ) between WSON and secondary species ( NH 4 + , NO 3 − , and SO 4 2 − ) also suggests the important contribution to WSON from secondary formation processes. Moreover, both protein type amino acids and primary amines revealed good correlations with water-soluble ions in spring, which indicates that seasonal variability occurred in primary sources and secondary formation pathway of the organic nitrogen species were found in Xi'an. [ABSTRACT FROM AUTHOR]

Measurements of the water-soluble organic nitrogen (WSON) in the aerosols were conducted over three years at two sites; an urban site in Kofu and a forested site in Fujiyoshida, Japan. Our preliminary experiment demonstrated that the adsorption of organic gases on the filter had little effect on the measurement of the WSON. The mean concentration of the WSON in the aerosols at the urban site was 0.221 µg m-3, which was higher than that of 0.101 µg m-3 at the forested site. Large portions of the WSON were found in the fine-mode range; 90.3% at the urban site and 86.4% at the forested site. The WSON constituted a significant fraction of the water-soluble total nitrogen (WSTN) in the aerosols; 11.1% and 16.2% of the WSTN in the coarse and fine particles, respectively, at the urban site, and 11.5% and 13.1% in the coarse and fine particles, respectively, at the forested site. The fine-mode WSON would be derived from the reaction of its basic precursor gases with particulate or gaseous acidic species. Photochemical reactions and combustion emissions could also be important sources of the fine-mode WSON. In the coarse-mode range, on the other hand, vegetation sources could be an important source of the WSON. The mean concentration of urea in the aerosols at the urban site was 1.7 ngN m-3. A large portion (87.2%) of the urea was partitioned into the fine-mode range. Urea is a minor compound in the particulate WSON in this region with contributions to about 1% of the WSON. Approximately 26% of the dry deposition of the WSTN was attributed to the WSON in the cold season. The significant part (96.5%) of the WSON was deposited by coarse aerosols. Coarse-mode WSON is important for discussing the dry deposition fluxes of the WSON and fixed nitrogen. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen-containing organic compounds in the atmosphere have drawn attention owing to their impact on aerosol chemistry and physics and their potential adverse effects on the biosphere. Among them, nitrocatechols and their homologs have recently been associated with biomass burning. In the present study, nitrocatechols, nitrophenols, nitroguaiacols and nitrosalicylic acids (NSAs) were simultaneously quantified for the first time by using a new analytical method based on liquid chromatography/tandem mass spectrometry, which was systematically optimized and validated. Several analyte specific issues regarding the sample preparation and chromatographic analysis were addressed in order to ensure method sensitivity, precision, and accuracy. Sample matrix effects were thoroughly investigated in order to ensure method specificity. The method was found to be sensitive with limits of detection ranging from 0.1 to 1.0μgL−1, and with accuracy generally between 90 and 104%. The relative standard deviations for repeatability and intermediate precision were better than 4% and 9%, respectively. The method was applied to the analysis of winter and summer PM10 samples from the city of Ljubljana, Slovenia. Aerosol concentrations as high as 152 and 134ngm−3 were obtained for the major aerosol nitro-aromatics: 4-nitrocatechol (4NC) and methyl-nitrocatechols (MNCs), respectively. Up to 500-times higher concentrations of 4NC and MNCs were found in winter compared to summer aerosols. The correlation analysis for winter samples showed that 4NC, MNCs, and NSAs are strongly inter-correlated (R 2 =0.84–0.96). Significant correlations between these analytes and anhydrosugars support their proposed origin from biomass burning. The studied nitro-aromatics were found to constitute a non-negligible fraction (around 1%) of the organic carbon. [Copyright &y& Elsevier]

Methodology for detection of native (underivatized) amino acids (AA) in atmospheric aerosols has been developed. This article describes the use of LC-MS (Q-TOF) and microwave-assisted gas phase hydrolysis for detection of free and combined amino acids in aerosols collected in a Southeastern U.S. forest environment. Accurate mass detection and the addition of isotopically labeled surrogates prior to sample preparation allows for sensitive quantitation of target AA in a complex aerosol matrix. A total of 16 native AA were detected above the reporting threshold as water-soluble free AA, with an average concentration of 22 ± 9 ng m ( N = 13). Following microwave-assisted gas phase hydrolysis, the total AA concentration in the forest environment increased significantly (70 ± 35 ng m) and additional compounds (methionine, isoleucine) were detected above the reporting threshold. The ability to quantify AA in aerosol samples without derivatization reduces time-consuming preparation procedures while providing the advancement of selective mass determination for important organic nitrogen (ON) species. Details on sample preparation that eliminates the freeze-drying approach typically practiced for water removal with biological samples, and vapor phase microwave hydrolysis parameters are provided. Method application for determination of atmospheric ON is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Simultaneous daily measurements of water-soluble organic nitrogen (WSON), ammonium and nitrate were made between July and November 2008 at a rural location in south-east Scotland, using a ‘Cofer’ nebulizing sampler for the gas phase and collection on an open-face PTFE membrane for the particle phase. Average concentrations of NH3 were 82 ± 17 nmol N m−3 (error is s.d. of triplicate samples), while oxidised N concentrations in the gas phase (from trapping NO2 and HNO3) were smaller, at 2.6 ± 2.2 nmol N m−3, and gas-phase WSON concentrations were 18 ± 11 nmol N m−3. The estimated collection efficiency of the nebulizing samplers for the gas phase was 88 (±8) % for NH3, 37 (±16) % for NO2 and 57 (±7) % for WSON; reported average concentrations have not been corrected for sampling efficiency. Concentrations in the particle phase were smaller, except for nitrate, at 21 ± 9, 10 ± 6 and 8 ± 9 nmol N m−3, respectively. The absence of correlation in either phase between WSON and either (NH3 + NH4 +) or NO3 − concentrations suggests atmospheric WSON has diverse sources. During wet days, concentrations of gas and particle-phase inorganic N were lower than on dry days, whereas the converse was true for WSON. These data represent the first reports of simultaneous measurements of gas and particle phase water-soluble nitrogen compounds in rural air on a daily basis, and show that WSON occurs in both phases, contributing 20–25% of the total water-soluble nitrogen in air, in good agreement with earlier data on the contribution of WSON to total dissolved N in rainfall in the UK. [Copyright &y& Elsevier]

Based on atmospheric precipitation collected in the northern suburbs of Nanjing from 2019 to 2020, the pH, conductivity, and chemical components of precipitation were analyzed. The seasonal variation in pH and conductivity of atmospheric precipitation in the northern suburbs of Nanjing were studied. The pollution levels and deposition characteristics of water-soluble inorganic nitrogen (WSIN) and organic nitrogen (WSON) in precipitation were also analyzed. The frequency of acid rain (pH<5.6) in atmospheric precipitation in the northern suburbs of Nanjing reached 37.18% during the observation period. Precipitation acidification was more serious in autumn and winter, and the pH value showed a variation trend of spring>summer>autumn>winter. The average conductivity of precipitation was 29.49 μS·cm -1 ; high pH and conductivity in spring were related to the high dust content in the atmosphere. The seasonal difference between WSIN and WSON in precipitation was significant. The highest and lowest concentrations of NO 3 - -N and NH 4 + -N appeared in spring and summer, respectively. The concentration of WSON was the highest in autumn (2.63 mg·L -1 ). The average concentration ratio of WSON to water-soluble total nitrogen (WSTN) in precipitation was approximately 0.47, indicating that WSON played an important role in the study of total nitrogen. The average wet deposition fluxes of WSIN and WSON were 12.10 kg·(hm 2 ·a) -1 and 11.13 kg·(hm 2 ·a) -1 , respectively, in which the inorganic nitrogen deposition was mainly NH 4 + -N.

The seasonal variation characteristics of water-soluble organic nitrogen (WSON) in PM 2.5 were analyzed in the Nanjing Jiangbei new area. The relationship between WSON and water-soluble inorganic nitrogen (WSIN) was also discussed. The results showed that the variation range of WSON in PM 2.5 was 0.446 to 4.200 μg·m -3 , with an average value of 2.04 μg·m -3 . This value was slightly higher than the observed results in Beijing, Shanghai, and Changzhou. The average value of WSON was the highest in autumn[(2.967±0.643) μg·m -3 ], which was approximately 1.7 times that of the other three seasons. The average contribution ratio of WSON to water-soluble total nitrogen (WSTN) in fine particles of Nanjing accounted for 25%, with high ratios in summer-autumn and low ratios in winter-spring. For example, the proportion of WSON/WSTN in winter was only approximately 50% of that in summer and autumn. WSON had the highest correlation with NO 2 - -N and the lowest correlation with NO 3 - -N in WSIN, which may be related to the volatilization of NO 3 - -N caused by high temperatures in summer. Principal component analysis (PCA) showed that WSON of PM 2.5 in Nanjing was mainly derived from secondary transformation, sea salt, dust, and biomass combustion.

A year-round observation of the free amino acids (FAA) and combined amino acids (CAA) in coarse and fine aerosols were conducted at an urban site in Japan. The averaged concentrations of the total FAA and total CAA measured in this study were 149.9 and 237.6 pmolN m−3, respectively, in coarse aerosols, and 177.9 and 562.2 pmolN m−3, respectively, in fine aerosols. The concentrations of the total CAA were higher than those of the total FAA in both mode ranges. The CAA were mainly partitioned into the fine-mode range, whereas the FAA were contained in both mode ranges with a similar concentration level. Only 8.1% of the water-soluble organic nitrogen (WSON) in fine aerosols was explained by these amino acids, although a significant contribution (26.4%) of them to the WSON was found in coarse aerosols. Correlation and factor analyses including these amino acids and other chemical species in the aerosols and gas phase were conducted to discuss potential sources of these amino acids. Plant debris and their associated materials, sea-salt, and Asian dust particles would be important potential sources of the coarse-mode FAA. The most dominant FAA in coarse aerosols was serine that is considered to be derived from sea-salt and Asian dust particles, whereas the other major FAA in coarse aerosols would be from plant debris and associated materials. The coarse-mode CAA can be also considered to be mainly from plant debris and associated materials. Glutamic acid and aspartic acid were dominant in the coarse-mode CAA, and estimated to be from these sources. Significant parts of the fine-mode FAA would be derived from the photochemical aging of the fine-mode CAA in polluted air masses from the Asian continent. Glycine and arginine were dominant in the fine-mode FAA, and estimated to be from the photochemical aging process. The fine-mode CAA is considered to be mainly from both the fossil fuel and biomass burning particles from both the Asian continental and local sources. Glutamic acid and glycine were dominant in the fine-mode CAA, and would be mainly from these sources, especially the Asian continental sources. Serine that is the most dominant compound in the fine-mode CAA, however, is considered to be derived from other unidentified sources. • Plant debris, sea-salt, and Asian dust are important sources of the coarse-mode FAA. • The coarse-mode CAA is mainly derived from plant debris and associated materials. • The fine-mode FAA is mainly derived from the photochemical aging of the CAA. • The fine-mode CAA is mainly derived from both the fossil fuel and biomass burning. [ABSTRACT FROM AUTHOR]

Air-to-sea deposition of water-soluble total nitrogen (WSTN) can influence the primary productivity in the coastal oceans. Here, we assessed the concentrations of aerosol inorganic (WSIN: NH 4 + + NO 3 −) and WSTN over the Arabian Sea during winter season (SS379:6–24 December 2018). The mean concentrations of NH 4 + (109 ± 83 nmol m−3) overwhelm that of NO 3 − (32 ± 13 nmol m−3) and water-soluble organic nitrogen (WSON: WSTN-WSIN: 86 ± 81 nmol m−3), and contributing to ~50 ± 31% of WSTN mass. Significant linear relationships of WSON with water-soluble organic carbon and NH 4 + with non-sea-salt (nss)-K+ is observed suggesting their common origin from biomass burning and fertilizers. Backward air mass trajectories and satellite-based fire counts further revealed their provenance in the Indo-Gangetic Plain and southern India. The concentration of NO 3 − moderately correlated with nss Ca2+ (dust tracer), indicating heterogeneous reactive uptake on mineral aerosol surface. Despite high concentrations, the deposition fluxes of NH 4 + (~9.4 ± 7.1 μmol m−2 d−1) and WSON (7.4 ± 7.0 μmol m−2 d−1) are lower than NO 3 − (27 ± 11 μmol m−2 d−1) because of their predominant fine nature (i.e., strong correlation with nss-SO 4 2−). We also constrained the total annual atmospheric deposition rates of WSIN (0.94 Tg yr−1) and WSON (0.08 Tg yr−1) to the Arabian Sea during the continental outflow (November-April). The maximum dry-deposition of WSON to the Arabian Sea (0.24 Tg yr−1) is twice that of the riverine supply (0.11 Tg yr−1), highlighting the significance of aeolian sources. By using Redfield Stoichiometry, the WSTN deposition (21–73 μmol m−2 d−1) can account for <5.3% of fixed‑carbon by a primary production in the Arabian Sea. • High abundances of NH4+ and WSON in aerosols over Arabian Sea. • Aeolian supply of WSON is comparable to that of Riverine input. • Water soluble nitrogen in aerosols can support >3% of water column primary production. [ABSTRACT FROM AUTHOR]

Atmospheric nitrogen is ubiquitous in the environment and hence plays an essential role in the nutrient balance over the whole ecosystem. However, its abundance and characteristics, particularly in the Himalayas, are not well understood. Therefore, to understand the abundance, sources, and seasonality of soluble nitrogenous species in the middle hills of the central Himalayas, aerosol samples were collected at Dhulikhel in Nepal from January to December 2018. The results of this study revealed that water-soluble inorganic nitrogen (WSIN) contributed the most to water-soluble total nitrogen with an abundance of ammonium nitrogen (NH 4 +–N). Moreover, water-soluble organic nitrogen (WSON) contributed approximately 18% to aerosol total water-soluble nitrogen. The aerosol mass and WSIN species exhibited strong seasonality with considerably higher concentrations during dry periods and lower concentrations during the wet period. Furthermore, for dry periods, the HYSPLIT model revealed that nitrogen aerosols mainly originated from the Indo-Gangetic Plain region and were transported and deposited in the Himalayas through long-range atmospheric transport. The strong correlations of WSON with nss K+ (biomass burning) and nss Ca2+ (crustal sources) and lack of a significant correlation with SO 4 2− indicated that primary sources are responsible for generating WSON rather than secondary processes in the Himalayas. The estimated dry deposition fluxes for NO 3 −–N, NH 4 +–N, and WSON were 1.56, 8.35, and 4.06 kg ha−1 y−1, respectively. This study also shows that increasing air contaminants and emissions over South Asia can enter the Himalayas and affect the human health and ecology of this fragile area. Unlabelled Image • WSON contributed ~18% to aerosol total water-soluble nitrogen (TWSN). • WSON did not show any seasonality; meanwhile, WSIN exhibited strong seasonality. • Primary sources are responsible for generating WSON rather than secondary processes. • Ammonium-N plays a significant role in Nitrogen deposition. • South Asian pollutants play a vital role in enhanced N-species in the Himalayas. [ABSTRACT FROM AUTHOR]

In order to clarify the deposition amounts and processes of bioavailable nitrogen species including organic forms on forests, a simultaneous observation of rainfall, throughfall, stemflow, aerosols, and their precursor gases was conducted for a two-year period at a forested site on the northern foot of Mt. Fuji in Japan. About 80–90% of the rainfall waters reached the forest floor via the throughfall process and the remaining fraction can be considered to be intercepted by the forest canopy and not transported to the forest floor. Partitioning of the rainfall waters into stemflow waters was negligible. Deposition amounts of the total dissolved nitrogen by rainfall, throughfall, and stemflow were 2.204, 2.685, and 0.027 mgN m−2 day−1, respectively, on average. Contributions of the water-soluble organic nitrogen (WSON) to the dissolved nitrogen in the rainfall, throughfall, and stemflow deposition were about 51%, 58%, and 75%, respectively. The major fraction of the nitrogen species in the deposition was the organic forms. Among the inorganic nitrogen, the contribution of NH 4 +-N to the nitrogen deposition was significantly greater than that of NO 3 −-N in the rainfall deposition, whereas both were comparable in the throughfall deposition. The deposition amounts of NO 3 −-N and WSON by throughfall were greater than those by rainfall due to the influence of the dry deposition on the canopies and the leaching from trees, whereas the deposition amount of NH 4 +-N by throughfall was smaller than that by rainfall due to the uptake by trees. About 58% of the net nitrogen deposition on the forest floor, which is defined as the sum of the deposition amounts by the throughfall and stemflow, was explained by the WSON. In the remaining inorganic fraction, the contributions of NO 3 −-N and NH 4 +-N to the net nitrogen deposition were comparable, about 20% and 22%, respectively. The nitrogen deposition amount to the forest floor was estimated to be 2.711 mg m−2 day−1, which is equal to the value of the threshold for the condition of "nitrogen saturation" for the forest ecosystems. The modified canopy budget model can estimate that the contributions of the dry deposition to the sum of the dry and wet deposition were about 90%, 64%, 61%, and 22% for NO 2 −-N, NO 3 −-N, NH 4 +-N, and WSON, respectively. The canopy leaching was found only for the WSON, about 72%, 20%, and 8.5% of the net deposition of the WSON can be explained by the wet deposition, dry deposition, and canopy leaching, respectively. The remaining nitrogen compounds showed the canopy uptake. About 10%, 56% and 32% of NO 2 −-N, NO 3 −-N, and NH 4 +-N deposited on the canopy by the wet and dry processes would be transported to the forest floor and the remaining fractions (about 90%, 44%, and 68%, respectively) would be taken into the canopy. Comparisons of the dry deposition amount with the concentration in the surface atmosphere of the nitrogen compounds suggest that the modified canopy budget model can be considered to be better to estimate the amounts of the dry deposition and canopy exchange. • About 58% of the nitrogen deposition on the forest floor was explained by the WSON. • About 72% of the WSON deposition on the forest floor was derived from wet deposition. • The remaining fraction was derived from dry deposition and canopy leaching. • For the inorganic nitrogen species, dry deposition was greater than wet deposition. • Inorganic nitrogen species were absorbed into trees. [ABSTRACT FROM AUTHOR]

To estimate dry deposition flux of atmospheric water-soluble nitrogen (N), including ammonium (NH4+), nitrate (NO3−), and water-soluble organic nitrogen (WSON), aerosol samples were collected over the subarctic western North Pacific Ocean in the summer of 2016 aboard the Korean icebreaker IBR/V Araon. During the cruise, concentrations of NH4+, NO3−, and WSON in bulk (fine + coarse) aerosols ranged from 0.768 to 25.3, 0.199 to 5.94, and 0.116 to 14.7 nmol m−3, respectively. Contributions of NH4+, NO3−, and WSON to total water-soluble N represented ~74%, ~17%, and ~9%, respectively. Water-soluble N concentrations showed a strong gradient from the East Asian continent to the subarctic western North Pacific Ocean, indicating that water-soluble N species were mainly derived from anthropogenic or terrestrial sources. During sea fog events, coarse mode NO3− was likely to be scavenged more efficiently by fog droplets than fine mode NO3−; besides, WSON was detected only in fine mode, suggesting that there may have been a significant influence of sea fog on WSON, such as the photochemical conversion of WSON into inorganic N. Mean dry deposition flux for water-soluble total N (6.3 ± 9.4 µmol m−2 d−1) over the subarctic western North Pacific Ocean was estimated to support a minimum carbon uptake of 42 ± 62 µmol C m−2d−1 by using the Redfield C/N ratio of 6.625. [ABSTRACT FROM AUTHOR]

The South China Sea (SCS) is one of the world's largest oligotrophic marginal seas. Increases in biomass and primary production in the surface layer of the northern SCS are affected by anthropogenic aerosol use among north Asian peoples. The seasonal variation of dry deposition and its contribution to new production in the ocean are vital to determining the effect that such dry deposition has on the biogeochemical cycle of the SCS. This study collected 240 samples of total suspended particles at Dongsha Island in the northern SCS from April 2007 to March 2009; the major ions and water-soluble nitrogen species in the samples were analyzed. The analysis results indicated that the concentration distributions of major water-soluble ions and nitrogen species in total suspended particles exhibited significant seasonal (source) variation. The north-east monsoon seasons (autumn to spring) brought relatively high concentrations because most air masses during this period arrived from the northern continental region. We found that the concentration of nitrogen species shows a latitude distribution, gradually decreasing from north to south. In addition, this study also discovered that the ratio of organic nitrogen to total dissolved or water-soluble nitrogen also varies in a similar manner, resulting in a concentration of <20% for locations north of 30° N and >30% for those south of 30° N. Aerosols at Dongsha Island mainly comprised sea salt; however, significant chloride depletion was observed during the north-east monsoon season. The molar ratio of NH4+ to non–sea salt (NSS) sulfate (nss-SO42−) was 0.8, indicating that the amount of artificially produced NH4+ in the region was insufficient for reaction with nss-SO42−. Therefore, NH4+ was mainly present in the form of NH4HSO4. The fluxes of water-soluble inorganic nitrogen (WSIN) and water-soluble organic nitrogen (WSON) within the region were 23 ± 13 and 27 ± 15 mmol m−2 y−1, respectively. The new production converted from atmospheric water-soluble nitrogen species in the northern SCS was estimated to be 0.52–0.81 mmol C m−2 d−1. This flux made about 5.6–8.7% (the global average was about 3.5%) contribution to the primary production (9.24 mmol C m−2 d−1) of the SCS surface water. This result indicates that the ocean's external nitrogen supply, provided by anthropogenic aerosols, is vital for the biogeochemical cycle in Asian marginal seas, particularly the northern SCS. [ABSTRACT FROM AUTHOR]

The WSON in the gas phase and aerosols were simultaneously measured by the denuder–filter pack method. Approximately 33 ± 18% of the WSON in the atmosphere existed in the gas phase. A large portion (approximately 76 ± 33%) of the gaseous WSON collected in the present sampling method was occupied by basic species. The gaseous basic and acid WSON showed about one-sixth of the nitrogen concentrations of the gaseous NH3 and HNO3, respectively. These results indicate that the gaseous WSON is also an important fixed nitrogen species in the atmosphere. [ABSTRACT FROM AUTHOR]