Aerosol Nitrogen Research Articles

Source signatures from combined isotopic analyses of PM2.5 carbonaceous and nitrogen aerosols at the peri-urban Taehwa Research Forest, South Korea in summer and fall

Isotopes are essential tools to apportion major sources of aerosols. We measured the radiocarbon, stable carbon, and stable nitrogen isotopic composition of PM2.5 at Taehwa Research Forest (TRF) near Seoul Metropolitan Area (SMA) during August–October 2014. PM2.5, TC, and TN concentrations were 19.4 ± 10.1 μg m−3, 2.6 ± 0.8 μg C m−3, and 1.4 ± 1.4 μg N m−3, respectively. The δ13C of TC and the δ15N of TN were − 25.4 ± 0.7‰ and 14.6 ± 3.8‰, respectively. EC was dominated by fossil-fuel sources with Fff (EC) of 78 ± 7%. In contrast, contemporary sources were dominant for TC with Fc (TC) of 76 ± 7%, revealing the significant contribution of contemporary sources to OC during the growing season. The isotopic signature carries more detailed information on sources depending on air mass trajectories. The urban influence was dominant under stagnant condition, which was in reasonable agreement with the estimated δ15N of NH4+. The low δ15N (7.0 ± 0.2‰) with high TN concentration was apparent in air masses from Shandong province, indicating fossil fuel combustion as major emission source. In contrast, the high δ15N (16.1 ± 3.2‰) with enhanced TC/TN ratio reveals the impact of biomass burning in the air transported from the far eastern border region of China and Russia. Our findings highlight that the multi-isotopic composition is a useful tool to identify emission sources and to trace regional sources of carbonaceous and nitrogen aerosols.

Characterization of organic nitrogen in aerosols at a forest site in the southern Appalachian Mountains.

This study investigates the composition of organic particulate matter in PM2.5 in a remote montane forest in the southeastern US, focusing on the role of organic nitrogen (N) in sulfur-containing secondary organic aerosol (nitrooxy-organosulfates) and aerosols associated with biomass burning (nitro-aromatics). Bulk water-soluble organic N (WSON) represented ~ 14% w/w of water-soluble total N (WSTN) in PM2.5 on average across seasonal measurement campaigns conducted in the spring, summer, and fall of 2015. The largest contributions of WSON to WSTN were observed in spring (~ 18% w/w) and the lowest in the fall (~ 10% w/w). On average, identified nitro-aromatic and nitrooxy-organosulfate compounds accounted for a small fraction of WSON, ranging from ~ 1% in spring to ~ 4% in fall, though were observed to contribute as much as 28% w/w of WSON in individual samples that were impacted by local biomass burning. The highest concentrations of oxidized organic N species occurred during summer (average of 0.65 ng N m−3) along with a greater relative abundance of higher-generation oxygenated terpenoic acids, indicating an association with more aged aerosol. The highest concentrations of nitro-aromatics (e.g., nitrocatechol and methyl-nitrocatechol), levoglucosan, and aged SOA tracers were observed during fall, associated with aged biomass burning plumes. Nighttime nitrate radical chemistry is the most likely formation pathway for nitrooxy-organosulfates observed at this low NOx site (generally < 1 ppb). Isoprene-derived organosulfate (MW216, 2-methyltetrol derived), which is formed from isoprene epoxydiols (IEPOX) under low NOx conditions, was the most abundant individual organosulfate. Concentration-weighted average WSON / WSOC ratios for nitro-aromatics + organosulfates + terpenoic acids were 1 order of magnitude lower than the overall aerosol WSON / WSOC ratio, indicating the presence of other uncharacterized higher-N-content species. Although nitrooxy-organosulfates and nitro-aromatics contributed a small fraction of WSON, our results provide new insight into the atmospheric formation processes and sources of these largely uncharacterized components of atmospheric organic N, which also helps to advance the atmospheric models to better understand the chemistry and deposition of reactive N.

Sources of reactive nitrogen in marine aerosol over the Northwest Pacific Ocean in spring

Abstract. Atmospheric deposition of long-range transport of anthropogenic reactive nitrogen (Nr, mainly comprised of NHx, NOy and water-soluble organic nitrogen, WSON) from continents may have profound impact on marine biogeochemistry. In addition, surface ocean dissolved organic nitrogen (DON) may also contribute to aerosol WSON in the overlying atmosphere. Despite the importance of off-continent dispersion and Nr interactions at the atmosphere–ocean boundary, our knowledge of the sources of various nitrogen species in the atmosphere over the open ocean remains limited due to insufficient observations. We conducted two cruises in the spring of 2014 and 2015 from the coast of China through the East China seas (ECSs, i.e. the Yellow Sea and East China Sea) to the open ocean (i.e. the Northwest Pacific Ocean, NWPO). Concentrations of water-soluble total nitrogen (WSTN), NO3- and NH4+, as well as the δ15N of WSTN and NO3- in marine aerosol, were measured during both cruises. In the spring of 2015, we also analysed the concentrations and δ15N of NO3- and the DON of surface seawater (SSW; at a depth of 5 m) along the cruise track. Aerosol NO3-, NH4+ and WSON decreased logarithmically (1–2 orders of magnitude) with distance from the shore, reflecting strong anthropogenic emission sources of NO3-, NH4+ and WSON in China. Average aerosol NO3- and NH4+ concentrations were significantly higher in 2014 (even in the remote NWOP) than in 2015 due to the stronger wind field in 2014, underscoring the role of the Asian winter monsoon in the seaward transport of anthropogenic NO3- and NH4+. However, the background aerosol WSON over the NWPO in 2015 (13.3 ± 8.5 nmol m−3) was similar to that in 2014 (12.2 ± 6.3 nmol m−3), suggesting an additional non-anthropogenic WSON source in the open ocean. Obviously, marine DON emissions should be considered in model and field assessments of net atmospheric WSON deposition in the open ocean. This study contributes information on parallel isotopic marine DON composition and aerosol Nr datasets, but more research is required to explore complex Nr sources and deposition processes in order to advance our understanding of anthropogenic influences on the marine nitrogen cycle and nitrogen exchange at land–ocean and atmosphere–ocean interfaces.

Water-soluble nitrogen and phosphorus in aerosols and dry deposition in Jiaozhou Bay, North China: Deposition velocities, origins and biogeochemical implications

To probe the deposition velocities (Vd), fluxes, origins and biogeochemical significance of atmospheric dry deposition (ADD) of nutrients in coastal waters, aerosol and dry deposition samples were collected in Jiaozhou Bay (JZB) from June 2015 to May 2016. We measured water-soluble inorganic nitrogen (WSIN; including ammonium (NH4N), nitrate (NO3N) and nitrite (NO2N)), organic nitrogen (WSON), inorganic phosphorus (WSIP; including reactive phosphate (PO4P)) and organic phosphorus (WSOP) for all samples. The concentrations of aerosol N species were comparatively higher than those in other aquatic ecosystems worldwide. Although WSIN and WSIP represented relatively large percentages of species, WSON (~16%) and WSOP (~35%) cannot be ignored in aerosols. The dry deposition fluxes for NH4N, NO3N, NO2N, WSON, PO4P and WSOP were 29.4, 29.9, 0.058, 15.4, 0.099 and 0.165 mmol m−2 yr−1, respectively, with apparent seasonal variations. The average annual Vd values of NH4N, NO3N, NO2N, WSON, PO4P and WSOP were indirectly calculated as 0.17 ± 0.11, 0.35 ± 0.20, 0.34 ± 0.25, 0.30 ± 0.22, 0.43 ± 0.28 and 0.91 ± 0.60 cm s−1, respectively. The considerable differences between the percentages of corresponding nutrient concentrations and ADD fluxes were mainly attributed to Vd variations. Anthropogenic emissions were the most common source of WSON and WSIN based on a correlation analysis. WSIP was highly correlated with WSOP, suggesting that they may share similar sources. Additionally, the long-range transport of natural and anthropogenic pollutants, especially the air-masses originating from the northwest direction, exerted greater effects than local emissions on aerosol N and P species in JZB based on an air mass backward trajectory analysis. The increasing ADD flux may have non-negligible biogeochemical effects on JZB by increasing primary productivity and altering the nutrient structure due to the high WSIN/WSIP ratio.

Concentrations and Compositions of Different Forms of Nitrogen and Phosphorus in Atmospheric Aerosols in the Qingdao Coastal Region and over the Yellow and Bohai Sea

The total suspended particulate (TSP) samples were collected in the Qingdao coastal region and over the Yellow and Bohai Sea from June to July in 2016. The diurnal and nightly TSP samples were also continuously collected in the Qingdao coastal region from August 6 to 15. The concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), dissolved total nitrogen (DTN), dissolved total phosphorus (DTP), total nitrogen (TN), and total phosphorus (TP) in the TSP samples were analyzed. Results showed that the concentrations of different forms of nitrogen and phosphorus in Qingdao were higher than those over the Yellow and Bohai Sea during the same sampling period. The contribution of dissolved N was similar to that of insoluble N to TN in Qingdao, with the ratio of DTN to TN of 56%. However the DTN was the dominant contributor of TN over the Yellow and Bohai Sea, accounting for 72% of TN on average. The inorganic nitrogen was the dominant species of DTN in Qingdao and over the Yellow and Bohai Sea (YBS), accounting for 67% and 75% of DTN, respectively. The contribution of dissolved P to TP was similar to that of insoluble P to TP in Qingdao and over the Yellow and Bohai Sea, and the DTP accounted for 49% and 58% of TP in Qingdao and over YBS, respectively. The ratio of IP to DTP was slightly higher than that of OP, with values of 56% and 59% in Qingdao and over the YBS, respectively. The origin of the air mass affected the concentrations and compositions of nitrogen and phosphorus in the aerosols. The concentrations of DIN, dissolved organic nitrogen (DON), TN, DIP, and dissolved organic phosphorus (DOP) in the aerosols from southern air mass were higher than those from northern and marine air masses. The concentration of DON in the diurnal aerosol samples was similar to that in the nightly samples; however, the concentrations of DIN and TN were higher in the diurnal aerosols than those in the nightly aerosols. The DTN was the dominant species of TN in the diurnal and nightly aerosol samples, accounting for 79% of TN on average. Inorganic nitrogen was the dominant species of DTN in the diurnal and nightly aerosols. The ratio of DIN to DTN decreased from 70% in diurnal samples to 61% in nightly samples. The concentrations of DIP were close to that of DOP in the diurnal and nightly aerosols; however, the concentrations of TP were higher in the diurnal aerosols than in the nightly ones. The insoluble P was the dominant form of TP in the aerosols, accounting for 83% and 62% of TP during the day and night, respectively. The contribution of DTP to TP in the nightly aerosols samples was much higher than that in the diurnal aerosols. For both day and night samples, inorganic phosphorus was the dominant species of DTP in aerosols, with a ratio of 71%-77%.

Theoretical insight into the role of urea in the hydrolysis reaction of NO2 as a source of HONO and aerosols

Environmental contextUrea is an important component of dissolved organic nitrogen in rainfall and aerosols, but the sources and the mechanisms of its production are not well understood. This computational study explores the effects of urea and water on the hydrolysis of NO2 and urea nitrate production. The results will aid our interpretation of the role of urea in the formation of atmospheric secondary nitrogen contaminants and aerosols. AbstractThe effects of urea on the hydrolysis reaction 2NO2 + mH2O (m = 1–3) have been investigated by theoretical calculations. The energy barrier (−2.67 kcal mol−1) of the urea-promoted reaction is lower than the naked reaction by 14.37 kcal mol−1. Urea also has a better catalytic effect on the reaction than methylamine and ammonia. Urea acts as a catalyst and proton transfer medium in this process, and the produced HONO may serve as a source of atmospheric nitrous acid. In addition, the subsequent reactions include clusters of nitrite, urea, and nitric acid. Then urea nitrate (UN), which is a typical HNO3 aerosol, can be formed in the subsequent reactions. The production of the acid-base complex (UN-2) is more favourable with an energy barrier of 0.10 kcal mol−1, which is 3.88 kcal mol−1 lower than that of the zwitterions NH2CONH3+NO3− (UN-1). The formation of zwitterions and the hydrolysis reaction are affected by humidity. The multi water-promoted hydrolysis reactions exhibit better thermodynamic stability when the humidity is increased. The extra water molecules act as solvent molecules to reduce the energy barrier. The natural bond orbital (NBO) analysis is employed to describe the donor-acceptor interactions of the complexes. The hydrogen bond interaction between the urea carbonyl and nitric acid of UN-2 is the strongest. The potential distribution maps of the urea nitrate and hydrate are examined, and the result shows that they tend to form zwitterions.

Seasonal Characterization of Organic Nitrogen in Atmospheric Aerosols Using High Resolution Aerosol Mass Spectrometry in Beijing, China

Despite extensive efforts to characterize organic nitrogen (ON) in atmospheric aerosols, knowledge of the sources and processes of ON in the megacity of Beijing is still limited, mainly due to the complexity of ON species and the absence of highly time-resolved measurements. Here we demonstrate the applications of Aerodyne high-resolution time-of-flight aerosol mass spectrometer combined with positive matrix factorization in characterization of ON in submicron aerosols. Our results show that the average nitrogen-to-carbon ratios (N/C) vary from 0.021 to 0.028, and the average ON concentrations range from 0.26 to 0.59 μg m–3 during four seasons in Beijing. ON accounts for 7–10% of the total nitrogen (TN) on average, yet the sources vary differently across different seasons. We found that 56–65% of ON was secondary during three seasons except winter when 59–67% was related to primary emissions. Particularly, more oxidized secondary organic aerosol contributes the dominant fraction of ON (39–44%) in spring, ...

Water Soluble Organic Nitrogen (WSON) in Ambient Fine Particles Over a Megacity in South China: Spatiotemporal Variations and Source Apportionment

AbstractOrganic nitrogen aerosols are complex mixtures and important compositions in ambient fine particulate matters (PM2.5), yet their sources and spatiotemporal patterns are not well understood particularly in regions influenced by intensive human activities. In this study, filter‐based ambient PM2.5 samples at four stations (one urban, two rural, plus one urban roadside) and PM samples from combustion sources (vehicle exhaust, ship emission, and biomass burning) were collected in the coastal megacity Guangzhou, south China, for determining water soluble organic nitrogen (WSON) along with other organic and inorganic species. The annual average WSON concentrations, as well as the ratios of WSON to water soluble total nitrogen, were all significantly higher at rural sites than urban sites. Average WSON concentrations at the four sites during the wet season were quite near each other, ranging from 0.41 to 0.49 μg/m3; however, they became 2 times higher at the rural sites than at the urban sites during the dry season. Five major sources for WSON were identified through positive matrix factorization analysis. Vehicle emission (29.3%), biomass burning (22.8%), and secondary formation (20.2%) were three dominant sources of WSON at the urban station, while vehicle emission (45.4%) and dust (28.6%) were two dominant sources at the urban roadside station. At the two rural sites biomass burning (51.1% and 34.1%, respectively) and secondary formation (17.8% and 30.5%, respectively) were dominant sources of WSON. Ship emission contributed 8–12% of WSON at the four sites. Natural vegetation seemed to have very minor contribution to WSON.

Antarctic sea ice region as a source of biogenic organic nitrogen in aerosols

Climate warming affects the development and distribution of sea ice, but at present the evidence of polar ecosystem feedbacks on climate through changes in the atmosphere is sparse. By means of synergistic atmospheric and oceanic measurements in the Southern Ocean near Antarctica, we present evidence that the microbiota of sea ice and sea ice-influenced ocean are a previously unknown significant source of atmospheric organic nitrogen, including low molecular weight alkyl-amines. Given the keystone role of nitrogen compounds in aerosol formation, growth and neutralization, our findings call for greater chemical and source diversity in the modelling efforts linking the marine ecosystem to aerosol-mediated climate effects in the Southern Ocean.

Chemical Constituents of Carbonaceous and Nitrogen Aerosols over Thumba Region, Trivandrum, India.

Aerosol filter samples collected at a tropical coastal site Thumba over Indian region were analysed for water-soluble ions, total carbon and nitrogen, organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon/nitrogen and their sources for different seasons of the year. For the entire study period, the order of abundance of ions showed the dominance of secondary ions, such as SO42-, NO3-, and NH4+. On average, Mg2+ (56%), K+ (11%), SO42- (8.8%), and Ca2+ (8.1%) contributions were from maritime influence. There was significant chloride depletion due to enhanced levels of inorganic acids, such as SO42- and NO3-. Total carbon contributed 21% of the aerosol total suspended particulate matter in which 85% is organic carbon. Primary combustion-generated carbonaceous aerosols contributed 41% of aerosol mass for the entire study period. High average ratios of OC/EC (5.5±1.8) and WSOC/OC (0.38±0.11) suggest that organic aerosols are predominantly comprised of secondary species. In our samples, major fraction (89±9%) was found to be inorganic nitrate in total nitrogen (TN). Good correlations (R 2≥0.82) were observed between TN with NO3- plus NH4+, indicating that nitrate and ammonium ions account for a significant portion of TN. The temporal variations in the specific carbonaceous aerosols and air mass trajectories demonstrated that several pollutants and/or their precursor compounds are likely transported from north western India and the oceanic regions.

A study of pulmonary function test, diffusing capacity of lungs for carbon monoxide and hematological parameters among petrol pump workers

Background: Currently, air pollution is one of the crucial issues with growing concern. Automobile exhaust consists of mixture of soot, gases including oxides of sulfur and of nitrogen, carbon monoxide and liquid aerosols and particles. It leads to various lung disorders, carcinogenesis and changes in hematological parameters. Aims and Objective: To detect the presence and extent of changes in pulmonary function tests and changes in hematological parameters in petrol pump workers. Materials and Methods: It was a cross-sectional study. Study subjects comprised 60 males working at different petrol pumps. Healthy counterparts were taken as controls. The study subjects were given pre-designed questionnaire, and data were collected in preformed case record form. Investigations such as sputum for acid fast bacilli, spirometry, diffusing capacity of lungs for carbon monoxide (DLCO), and hematological parameters like hemoglobin (Hb)% and packed cell volume (PCV) were done. Data for all parameters were analyzed by software Microsoft excel and Graph pad prism5. Results: There was no statistical difference in the baseline characters of study and control groups. There was a significant decline in Hb% and PCV in petrol pump workers as compared to control group. Decrease in values of forced vital capacity, forced expired volume 1, and forced expiratory flow 25-75% is noted in petrol pump workers. Values of DLCO% predicted were mildly decreased in Group II and mild to moderately in Group III. Conclusions: The lung function tests and hematological tests (Hb, PCV) in petrol pump workers were significantly lower than control group. Lack of awareness and protective measures during duty hours by these workers may have led to lung function abnormality and hematological changes among them.

Batteries in Offshore Support Vessels - Pollution, Climate Impact and Economics

This paper assesses the pros and the cons of installing batteries on offshore support vessels. These vessels are specially designed to provide services to oil and gas operations, such as anchor handling, supply and subsea operations. They have multiple engines and advanced dynamic positioning systems to ensure that they can perform their duties with high reliability at nearly any sea state. Combined with high safety requirements, this has resulted in general operational patterns with vessels running multiple combustion engines even at calm water conditions. For emissions, low engine loads yield high emissions of exhaust gases such as nitrogen oxides (NOx) and aerosols such as black carbon (BC), due to less favorable combustion conditions. The high span for these vessels between low loads and high, and their great need for potential power at short notice, motivate our examination of hybrid setups with electric: the vessel segment should be more favorable than many. We find that combining batteries with combustion engines reduces local pollution and climate impact, while the economics with current battery cost and fuel prices is good enough for new vessels, but not good enough for retrofits.

Influence of atmospheric dry deposition of inorganic nutrients on phytoplankton biomass in the coastal Bay of Bengal

The aerosols from continents contain relatively higher amounts of inorganic nutrients than those of marine origin and can make a notable contribution to the coastal biological productivity. To test this hypothesis, the composition of aerosols over the city of Visakhapatnam (central east coast of India) were studied when continental flow was dominant and its impact on phytoplankton biomass was estimated through microcosm experiments between September 2013 and November 2014. Higher nitrate (NO3−) and ammonium (NH4+) concentrations were observed in the aerosols collected in January while higher phosphate (PO43−) was observed in September. Simultaneous observations of aerosols over the city and neighboring coastal waters revealed that the concentrations of nitrate in ambient aerosols ranged from 0.56 to 1.89μgm−3 and 0.09 to 0.86μgm−3, respectively. Our results suggest that 52–89% of city's aerosols borne nitrogen deposited over waters within 10km from the coastline. Microcosm experiments were conducted by spiking the surface water samples, collected from the coastal Bay of Bengal (BoB), with the dust borne nutrients. Upon spiking, dissolved inorganic nitrogen (NO3−+NH4+) increased from 0.3 to 11.7μmolL−1 and the N:P ratio increased from 2 to 97. This led to enhanced phytoplankton biomass (1.5 to 4 times) upon spiking. The increase in phytoplankton biomass was linearly related to dissolved N:P ratios in water as aerosol deposition increased the N:P ratios in the microcosms, leading to phytoplankton growth. Though aerosols did not contribute to bioavailable silicate, our microcosm experiments showed linear relationships between ambient silicate phytoplankton biomass, and concentrations of Fucoxanthin (a marker pigment for diatoms). This indicates that the availability of silicate in coastal waters facilitated dominant diatom growth in the presence of higher N:P ratios due to aerosol deposition. The deposition of soluble aerosol nitrogen appears to support ~3 to 33% of the biological production in the coastal waters off Visakhapatnam with higher contribution in winter (~33%) than in summer (10%). This study suggests that atmospheric deposition of nutrients enhances phytoplankton biomass in waters along the central east coast of India during the winter monsoon period, in particular, supporting the hypothesis stated above.

Study of fire–extinguishing efficiency of environmentally friendly binary aerosol-nitrogen mixtures

It was theoretically grounded and experimentally confirmed that adding nitrogen to the aerosol of inorganic potassium salts considerably increases efficiency of the fire­extinguishing of the obtained binary mixture. As a result of the studies we determined that the addition of nitrogen to the aerosol reduces the fire­extinguishing concentration of the components of the final binary mixture by 30 %. Experiments confirmed that the optimal ratio of the components in the mixture of a binary mixture, which consists of the aerosol is 10 g/m 3 and nitrogen – 12.1 %. It is fire­extinguishing for the diffusion flame of heptane and simultaneously provides life­safe concentration of oxygen. It was found that high efficiency of binary aerosol nitrogen mixture is achieved due to the synergy of the components of the mixture. We defined the value of intensity and decrease in the temperature of the diffusion and kinetic flame with its presence in the aerosol­nitrogen mixture. The study of fire­extinguishing efficiency of the aerosol­nitrogen mixtures is necessary to determine the conditions and methods of the fire extinguishing by the mixture in closed areas. Received dependencies and specifications of aerosol­nitrogen mixtures can be the foundation for the creation of ecologically clean, cheap, and simple in the production and operation fire­fighting tools with high fire­suppression efficiency, which can be used for the fire suppression in the areas of temporary stay of people and living organisms without an apparent damage to them as a result of volumetric fire extinguishing by the described mixtures.

DRY and BULK atmospheric nitrogen deposition to a West-African humid forest exposed to terrestrial and oceanic sources

Atmospheric deposition can be a significant source of reactive nitrogen (Nr) in terrestrial ecosystems and might play a relevant role for both N cycle processes and NC cycle interactions. However, detailed studies and annual budgets of Nr deposition are scarce in many regions of the globe, particularly dry depositions in tropical areas. In this study we estimated the magnitude and dynamics of Nr dry and bulk deposition to an African humid forest located 30km from the Atlantic coast, in the National Park of Ankasa (Ghana). Atmospheric concentrations of gaseous (NH3, NO2, HNO3) and aerosol (NH4+, NO3−) nitrogen compounds were measured above the forest canopy, at 45m, using active denuder and filter sampling systems (DELTA). The experimental facility also provided high frequency micrometeorological data, sampled at the same height as DELTA, which were used to estimate deposition fluxes of gas and aerosols by applying an ensemble of four inferential models (six for NH3). Additionally, bulk deposition rates and ionic composition were also determined. Estimated Nr input as dry deposition at the site was −4.9±1.7kgNrha−1yr−1, 50% of which in form of aerosol N (NH4++NO3−). Bulk deposition accounted for 23.1±3.6kgNrha−1yr−1. Two main N deposition peaks were identified during the year, the first occurring in the dry season and being more evident for gaseous N compounds, the second occurring during the wet season, when both aerosol N and bulk N deposition rates reached their maximum value. Savannah burning and ocean emissions were hypothesized to be two important sources for Nr deposition at Ankasa, the former having a more significant role in the dry season, the latter dominating in the wet season. The important role of the oceanic source was supported by the continuous significant input of aerosol N at the site, which was consistent with the constant presence of a sea breeze, causing never less than 50% of the dominant wind direction over the whole year.

Atmospheric chemistry of nitrogenous aerosols in northeastern Asia: biological sources and secondary formation

Abstract. To better understand the sources of nitrogenous aerosols, particularly water-soluble organic nitrogen (WSON) and water-insoluble organic nitrogen (WION), in northeastern Asia, we measured total nitrogen (TN) and water-soluble total nitrogen (WSTN) as well as nitrogen isotope ratios (δ15N) of TN (δ15NTN) and WSTN (δ15NWSTN) in the total suspended particulate (TSP) samples collected from Sapporo, northern Japan, for a 1-year period. In general, WION was more abundant (126 ± 117 ng m−3), whereas WSON was 89.7 ± 80.6 ng m−3, accounting for 14 ± 11 % and 9.2 ± 7.3 % of TN, respectively. WSON peaked in late autumn to winter (maximum 288 ng m−3) and WION peaked in mid-spring to early summer (454 ng m−3). δ15NTN (21.9 ± 4.1 ‰) and δ15NWSTN (25.8 ± 8.2 ‰) showed peaks in summer with relatively high ratios in late autumn. Based on the seasonal variations in WSON and WION together with organic tracers, fossil fuel combustion and biomass burning are found to be two major sources of WSON, whereas emissions of biological particles and secondary formation by reactions of biogenic secondary organic species (carbonyls) with NH3 are suggested as an important source of WION. The seasonality of δ15NTN and δ15NWSTN, together with the comparisons to literature values, implies that chemical aging (including gas–particle partitioning) and biomass burning are the causes of the enhanced values in summer and autumn, respectively. This study demonstrates that contributions of aerosol N from fossil fuel combustion and biomass burning dominate in autumn and/or winter, whereas emission of terrestrial biological particles and secondary formation from biogenic hydrocarbons and subsequent chemical aging in the atmosphere are important in spring and/or summer in northeastern Asia.

Atmospheric water-soluble organic nitrogen (WSON) over marine environments: a global perspective

Abstract. To obtain a comprehensive picture of the spatial distribution of water-soluble organic nitrogen (WSON) in marine aerosols, samples were collected during research cruises in the tropical and southern Atlantic Ocean and also in the southern Indian Ocean (Amsterdam Island) for a 1-year period (2005). Samples were analyzed for both organic and inorganic forms of nitrogen, and the factors controlling their levels were examined. Fine-mode WSON was found to play a significant role in the remote marine atmosphere with enhanced biogenic activity, with concentrations of WSON (11.3 ± 3.3 nmol N m−3) accounting for about 84 % of the total dissolved nitrogen (TDN). Such concentrations are similar to those observed in the polluted marine atmosphere of the eastern Mediterranean (11.6 ± 14.0 nmol N m−3). Anthropogenic activities were found to be an important source of atmospheric WSON as evidenced by the levels in the Northern Hemisphere (NH) being 10 times higher than in the remote Southern Hemisphere (SH). Furthermore, the higher contribution of fine-mode WSON to TDN (51%) in the SH, compared to the NH (13%), underlines the important role of organic nitrogen in remote marine areas. Finally, there was a strong association of WSON with dust in coarse-mode aerosols in the NH.

Free amino acids in Antarctic aerosol: potential markers for the evolution and fate of marine aerosol

Abstract. To investigate the impact of marine aerosols on global climate change it is important to study their chemical composition and size distribution. Amino acids are a component of the organic nitrogen in aerosols and particles containing amino acids have been found to be efficient ice nuclei. The main aim of this study was to investigate the L- and D-free amino acid composition as possible tracers of primary biological production in Antarctic aerosols from three different areas: two continental bases, Mario Zucchelli Station (MZS) on the coast of the Ross Sea, Concordia Station at Dome C on the Antarctic Plateau, and the Southern Ocean near the Antarctic continent. Studying the size distribution of amino acids in aerosols allowed us to characterize this component of the water-soluble organic carbon (WSOC) in marine aerosols near their source and after long-range transport. The presence of only free L-amino acids in our samples is indicative of the prevalence of phytoplanktonic material. Sampling at these three points allowed us to study the reactivity of these compounds during long-range transport. The mean total amino acid concentration detected at MZS was 11 pmol m−3, a higher percentage of amino acids were found in the fine fraction. The aerosol samples collected at Dome C had the lowest amino acid values (0.7 and 0.8 pmol m−3), and the coarse particles were found to have higher concentrations of amino acids compared to the coastal site. The amino acid composition in the aerosol collected at Dome C had also changed compared to the coastal site, suggesting that physical and chemical transformations had occurred during long range transport. During the sampling cruise on the R/V Italica on the Southern Ocean, high concentrations of amino acids were found in the total suspended particles, this we attribute to the presence of intact biological material (as microorganisms or plant material) in the sample.

Observed changes in ocean acidity and carbon dioxide exchange in the coastal Bay of Bengal – a link to air pollution

Variations in surface water hydrographic properties and dissolved inorganic carbon (DIC) were evaluated in the coastal Bay of Bengal using observations carried out during March–April 1991 and 2011, including 8 yr monthly time-series observations during 2005 and 2013. The coastal Bay of Bengal is characterised by relatively fresher, more basic and lower pCO2 in 1991 compared to 2011. The rates of decrease in pH, increase in DIC and pCO2 per decade were consistent with global trends in the southwestern (SW) coastal Bay of Bengal, whereas rates in the northwestern (NW) coastal Bay of Bengal were observed to be 3–5 times higher. The associated recent increase in sulphate and nitrogen aerosol loadings over NW Bay of Bengal from the Indo-Gangetic Plain and Southeast Asia during winter and spring may be mainly responsible for the increased acidity in recent years. Thus, this region, which was previously considered to be a significant sink for atmospheric CO2, now seems to have become a source of CO2 to the atmosphere.

Seasonal cycles of water‐soluble organic nitrogen aerosols in a deciduous broadleaf forest in northern Japan

AbstractThe seasonal variations in aerosol water‐soluble organic nitrogen (WSON) concentrations measured in a deciduous forest canopy over an approximately 30 month period were investigated for possible sources in the forest. The WSON concentrations (average 157 ± 127 ng N m−3) and WSON/water‐soluble total nitrogen mass fractions (average 20 ± 11%) in the total suspended particulate matter exhibited a clear seasonal cycle with maxima in early summer. The WSON mass was found to reside mostly in the fine‐mode size range (Dp &lt; 1.9 µm) during the summer months. WSON was positively correlated with oxidation products of α‐pinene and isoprene with similar size distributions, suggesting that secondary formation from biogenic hydrocarbon precursors is a plausible source for WSON in summer. In contrast, the majority of WSON in autumn was associated with coarse fraction (Dp &gt; 1.9 µm), which was similar to the size distributions of sugar compounds, indicating that the major WSON sources in autumn are associated with primary biological emissions. The vertical differences in WSON concentrations suggest that the water‐soluble organic aerosol is enriched with nitrogen below the canopy level relative to the forest floor. The WSON concentration increased with enhanced hydrogen ion concentrations in aerosol in the early summer, indicating that aerosol acidity associated with anthropogenic sources outside the forest likely plays an important role in the formation of WSON in that season. The study suggests that multiple sources of WSON within the forest canopy may dominate over others in specific seasons, providing insights into WSON formation processes in forest environments.