Water-soluble Organic Nitrogen Research Articles

Biogas Stoves Reduce Firewood Use, Household Air Pollution, and Hospital Visits in Odisha, India

Traditional cooking using biomass is associated with ill health, local environmental degradation, and regional climate change. Clean stoves (liquefied petroleum gas (LPG), biogas, and electric) are heralded as a solution, but few studies have demonstrated their environmental health benefits in field settings. We analyzed the impact of mainly biogas (as well as electric and LPG) stove use on social, environmental, and health outcomes in two districts in Odisha, India, where the Indian government has promoted household biogas. We established a cross-sectional observational cohort of 105 households that use either traditional mud stoves or improved cookstoves (ICS). Our multidisciplinary team conducted surveys, environmental air sampling, fuel weighing, and health measurements. We examined associations between traditional or improved stove use and primary outcomes, stratifying households by proximity to major industrial plants. ICS use was associated with 91% reduced use of firewood (p < 0.01), substantial time savings for primary cooks, a 72% reduction in PM2.5, a 78% reduction in PAH levels, and significant reductions in water-soluble organic carbon and nitrogen (p < 0.01) in household air samples. ICS use was associated with reduced time in the hospital with acute respiratory infection and reduced diastolic blood pressure but not with other health measurements. We find many significant gains from promoting rural biogas stoves in a context in which traditional stove use persists, although pollution levels in ICS households still remained above WHO guidelines.

Marine submicron aerosol gradients, sources and sinks

Abstract. Aerosol principal sources and sinks over eastern North Atlantic waters were studied through the deployment of an aerosol chemistry gradient sampling system. The chemical gradients of primary and secondary aerosol components – specifically, sea salt (SS), water-insoluble organic matter (WIOM), water-soluble organic matter (WSOM), nitrate, ammonium, oxalate, amines, methanesulfonic acid (MSA) and water-soluble organic nitrogen (WSON) – were examined in great detail. Sea salt fluxes were estimated by the boundary layer box model and ranged from 0.3 to 3.5 ng m−2 s−1 over the wind speed range of 5–12 m s−1 and compared well with the derived fluxes from existing sea salt source parameterisations. The observed seasonal pattern of sea salt gradients was mainly driven by wind stress in addition to the yet unquantified effect of marine OM modifying fractional contributions of SS and OM in sea spray. WIOM gradients were a complex combination of rising and waning biological activity, especially in the flux footprint area, and wind-driven primary sea spray production supporting the coupling of recently developed sea spray and marine OM parameterisations.

Uncertainties in the measurements of water-soluble organic nitrogen in the aerosol

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 PM2.5 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 PM2.5. 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.

Stable carbon and nitrogen isotopic compositions of ambient aerosols collected from Okinawa Island in the western North Pacific Rim, an outflow region of Asian dusts and pollutants

Stable carbon (δ13C) and nitrogen (δ15N) 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 δ13C and δ15N ratios are −22.2‰ and +12.5‰, respectively. The δ13C values are similar in both spring (−22.5‰) and winter (−22.5‰), suggesting the similar sources and/or source regions. We found that δ13C 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 δ13C 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 NO3− to TN was on average 45% whereas that of NH4+ 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.

Nitrogen speciation in various types of aerosols in spring over the northwestern Pacific Ocean

Abstract. The cumulative atmospheric nitrogen deposition has been found to profoundly impact the nutrient stoichiometry of the eastern China seas (ECSs: the Yellow Sea and East China Sea) and the northwestern Pacific Ocean (NWPO). In spite of the potential significance of dry deposition in those regions, shipboard observations of atmospheric aerosols remain insufficient, particularly regarding the compositions of water-soluble nitrogen species (nitrate, ammonium and water-soluble organic nitrogen – WSON). We conducted a cruise covering the ECSs and the NWPO during the spring of 2014 and observed three types of atmospheric aerosols. Aluminum content, air mass backward trajectories, weather conditions, and ion stoichiometry allowed us to discern dust aerosol patches and sea-fog-modified aerosols (widespread over the ECSs) from background aerosols (open ocean). Among the three types, sea-fog-modified aerosols contained the highest concentrations of nitrate (536 ± 300 nmol N m−3), ammonium (442 ± 194 nmol N m−3) and WSON (147 ± 171 nmol N m−3); furthermore, ammonium and nitrate together occupied ∼ 65 % of the molar fraction of total ions. The dust aerosols also contained significant amounts of nitrate (100 ± 23 nmol N m−3) and ammonium (138 ± 24 nmol N m−3) which were obviously larger than those in the background aerosols (26 ± 32 for nitrate and 54 ± 45 nmol N m−3 for ammonium), yet this was not the case for WSON. It appeared that dust aerosols had less of a chance to come in contact with WSON during their transport. In the open ocean, we found that sea salt (e.g., Na+, Cl−, Mg2+), as well as WSON, correlated positively with wind speed. Apparently, marine dissolved organic nitrogen (DON) was emitted from breaking waves. Regardless of the variable wind speeds from 0.8 to as high as 18 m s−1, nitrate and ammonium, by contrast, remained in narrow ranges, implying that some supply and consumption processes of nitrate and ammonium were required to maintain such a quasi-static condition. Mean dry deposition of total dissolved nitrogen (TDN) for sea-fog-modified aerosols (1090 ± 671 µmol N m−2 d−1) was 5 times higher than that for dust aerosols (190 ± 41.6 µmol N m−2 d−1) and around 20 times higher than that for background aerosols (56.8 ± 59.1 µmol N m−2 d−1). Apparently, spring sea fog on the ECSs played an important role in removing atmospheric reactive nitrogen from the Chinese mainland and depositing it into the ECSs, thus effectively preventing its seaward export to the NWPO.

Water-Soluble Organic Nitrogen in High Mountain Snow Samples from Central Japan

ABSTRACTWe measured water-soluble organic nitrogen (WSON) in snow pit samples, which were collected at the Murodo-Daira snowfield near the summit of Mt. Tateyama, central Japan in 2008, 2009, and 2011. The concentrations of WSON ranged from 12.8 to 96.7 ng g–1, which were significantly lower than those reported in continental wet deposition samples from the Asian continent. WSON may be largely diluted in the snow samples during snowing processes over the high mountains. We found that WSON significantly correlated with nss-Ca2+ and water-soluble organic carbon (WSOC). Concentrations of WSON are likely controlled by the intensity of Asian dust events. Contributions of WSON to water soluble total nitrogen (WSTN) in snow pit sequence was found to be 15 ± 10%, which is lower than those (63–91%) of reference dust materials collected in China. Mass concentration ratio of WSOC/WSON was on average 23.7, which is significantly higher than the C/N weight ratio (5.6) calculated from the Redfield ratio. This result suggests that WSOC is largely produced by secondary photochemical oxidation of anthropogenic volatile organic compounds during the transport from East Asia to the high mountain areas in Japan. On the other hand, WSON may be contributed from Asian dusts from arid areas in China whereas water-soluble inorganic nitrogen may be derived from pollution sources.

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.

Size-resolved airborne particulate oxalic and related secondary organic aerosol species in the urban atmosphere of Chengdu, China

Size-segregated (9-stages) airborne particles during winter in Chengdu city of China were collected on a day/night basis and determined for dicarboxylic acids (diacids), ketocarboxylic acids (ketoacids), α-dicarbonyls, inorganic ions, and water-soluble organic carbon and nitrogen (WSOC and WSON). Diacid concentration was higher in nighttime (1831±607ngm−3) than in daytime (1532±196ngm−3), whereas ketoacids and dicarbonyls showed little diurnal difference. Most of the organic compounds were enriched in the fine mode (<2.1μm) with a peak at the size range of 0.7–2.1μm. In contrast, phthalic acid (Ph) and glyoxal (Gly) presented two equivalent peaks in the fine and coarse modes, which is at least in part due to the gas-phase oxidation of precursors and a subsequent partitioning into pre-existing particles. Liquid water content (LWC) of the fine mode particles was three times higher in nighttime than in daytime. The calculated in-situ pH (pHis) indicated that all the fine mode aerosols were acidic during the sampling period and more acidic in daytime than in nighttime. Robust correlations of the ratios of glyoxal/oxalic acid (Gly/C2) and glyoxylic acid/oxalic acid (ωC2/C2) with LWC in the samples suggest that the enhancement of LWC is favorable for oxidation of Gly and ωC2 to produce C2. Abundant K+ and Cl− in the fine mode particles and the strong correlations of K+ with WSOC, WSON and C2 indicate that secondary organic aerosols in the city are significantly affected by biomass burning emission.

Changes in microbial community structure and functioning of a semiarid soil due to the use of anaerobic digestate derived composts and rosemary plants

We studied the changes in structure and functioning of the microbial community in a degraded agricultural soil after the addition of two composts, obtained from cattle manure or pig slurry anaerobic digestate, and the use of rosemary plants for restoring soil quality.The composts were added at low or high doses to soil samples (30 or 60tha−1, respectively), which were kept in microcosms for 6months. Some soil microcosms were treated with inorganic fertiliser and other non-treated soils were used as microbiological controls. Rosemary plants, used both for their ability to grow in semi-arid regions and for the capacity of their root system to protect soil from erosion, were planted in half of the entire microcosm set up. At different times (0–180days) microbial abundance and dehydrogenase activity were measured in the various experimental treatments. Total and water-soluble soil organic carbon and nitrogen contents were assessed at 0 and 180days. With an increase in carbon and nitrogen soil content, a rise in microbial abundance was also observed in the presence of both composts. However, microbial activity was significantly influenced by the presence of rosemary, without considering the allochthonous carbon and nitrogen input. Microbial community structure and diversity were also assessed by Fluorescence In Situ Hybridization in the different treatments. The highest values for microbial community biodiversity were found in the co-presence of rosemary and at low concentrations of both composts.The overall results suggest that the use of composts together with plant species suited to Mediterranean areas seems to be an appropriate strategy for restoring soil quality and the ecosystem services provided by microorganisms.

Characteristics of water-soluble organic nitrogen in fine particulate matter in the continental area of China

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 PM2.5 collected in Xi'an, China from 2008 to 2009. The yearly average WSON concentration (300 nmol Nm−3, ranging from 29 to 1250 nmol Nm−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 PM2.5. 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 (NH4+, NO3−, and SO42−) 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.

Evolution of aerosol chemistry in Xi'an, inland China, during the dust storm period of 2013 – Part 1: Sources, chemical forms and formation mechanisms of nitrate and sulfate

Abstract. A total suspended particulate (TSP) sample was collected hourly in Xi'an, an inland megacity of China near the Loess Plateau, during a dust storm event of 2013 (9 March 18:00−12 March 10:00 LT), along with a size-resolved aerosol sampling and an online measurement of PM2.5. The TSP and size-resolved samples were determined for elemental carbon (EC), organic carbon (OC), water-soluble organic carbon (WSOC) and nitrogen (WSON), inorganic ions and elements to investigate chemistry evolution of dust particles. Hourly concentrations of Cl−, NO3−, SO42−, Na+ and Ca2+ in the TSP samples reached up to 34, 12, 180, 72 and 28 μg m−3, respectively, when dust peak arrived over Xi'an. Chemical compositions of the TSP samples showed that during the whole observation period NH4+ and NO3− were linearly correlated with each other (r2=0.76) with a molar ratio of 1 : 1, while SO42− and Cl− were well correlated with Na+, Ca2+, Mg2+ and K+ (r2 &gt; 0.85). Size distributions of NH4+ and NO3− presented a same pattern, which dominated in the coarse mode (&gt; 2.1 μm) during the event and predominated in the fine mode (&lt; 2.1 μm) during the non-event. SO42− and Cl− also dominated in the coarse mode during the event hours, but both exhibited two equivalent peaks in both the fine and the coarse modes during the non-event, due to the fine-mode accumulations of secondarily produced SO42− and biomass-burning-emitted Cl- and the coarse-mode enrichments of urban soil-derived SO42− and Cl−. Linear fit regression analysis further indicated that SO42− and Cl− in the dust samples possibly exist as Na2SO4, CaSO4 and NaCl, which directly originated from Gobi desert surface soil, while NH4+ and NO3− in the dust samples exist as NH4NO3. We propose a mechanism to explain these observations in which aqueous phase of dust particle surface is formed via uptake of water vapor by hygroscopic salts such as Na2SO4 and NaCl, followed by heterogeneous formation of nitrate on the liquid phase and subsequent absorption of ammonia. Our data indicate that 54 ± 20% and 60 ± 23% of NH4+ and NO3− during the dust period were secondarily produced via this pathway, with the remaining derived from the Gobi desert and Loess Plateau, while SO42− in the event almost entirely originated from the desert regions. Such cases are different from those in the East Asian continental outflow region, where during Asia dust storm events SO42− is secondarily produced and concentrates in sub-micrometer particles as (NH4)2SO4 and/or NH4HSO4. To the best of our knowledge, the current work for the first time revealed an infant state of the East Asian dust ageing process in the regions near the source, which is helpful for researchers to understand the panorama of East Asian dust ageing process from the desert area to the downwind region.

Water-soluble organic nitrogen in the ambient aerosols and its contribution to the dry deposition of fixed nitrogen species in Japan

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.

On the water-soluble organic nitrogen concentration and mass size distribution during the fog season in the Po Valley, Italy

The study of organic nitrogen gained importance in recent decades due to its links with acid rain, pollution, and eutrophication. In this study, aerosol and fog water samples collected from two sites in Italy during November 2011 were analyzed to characterize their organic nitrogen content. Organic nitrogen contributed 19–25% of the total soluble nitrogen in the aerosol and around 13% in fog water. The largest water soluble organic nitrogen concentrations in the PM1.2 fraction occurred during the diurnal period with mean values of 2.03 and 2.16μg-Nm−3 (154 and 145nmol-Nm−3) at Bologna and San Pietro Capofiume (SPC), respectively. The mean PM10 WSON concentration during diurnal periods at SPC was 2.30μg-Nm−3 (164nmol-Nm−3) while it was 1.34 and 0.82μg-Nm−3 (95.7 and 58.5nmol-Nm−3) in the night and fog water samples, respectively. Aerosol mass distribution profiles obtained during fog changed significantly with respect to those estimated in periods without fog periods due to fog scavenging, which proved to be over 80% efficient. Linear correlations suggested secondary processes related to combustion and, to a lesser extent, biomass burning, as plausible sources of WSON. Regarding the inorganic nitrogen fraction, the results showed that ammonium was the largest soluble inorganic nitrogen component in the samples.

Rapid and Accurate Evaluation of the Quality of Commercial Organic Fertilizers Using Near Infrared Spectroscopy

The composting industry has been growing rapidly in China because of a boom in the animal industry. Therefore, a rapid and accurate assessment of the quality of commercial organic fertilizers is of the utmost importance. In this study, a novel technique that combines near infrared (NIR) spectroscopy with partial least squares (PLS) analysis is developed for rapidly and accurately assessing commercial organic fertilizers quality. A total of 104 commercial organic fertilizers were collected from full-scale compost factories in Jiangsu Province, east China. In general, the NIR-PLS technique showed accurate predictions of the total organic matter, water soluble organic nitrogen, pH, and germination index; less accurate results of the moisture, total nitrogen, and electrical conductivity; and the least accurate results for water soluble organic carbon. Our results suggested the combined NIR-PLS technique could be applied as a valuable tool to rapidly and accurately assess the quality of commercial organic fertilizers.

One-year observations of carbonaceous and nitrogenous components and major ions in the aerosols from subtropical Okinawa Island, an outflow region of Asian dusts

Abstract. Ambient aerosol samples (TSP, n = 50) were collected for 12 months at subtropical Okinawa Island, Japan, an outflow region of Asian dusts in the western North Pacific and analysed for organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), water-soluble total nitrogen (WSTN), water-soluble organic nitrogen (WSON) and major ions to better understand the formation and transformation of East Asian aerosols during long-range atmospheric transport. Concentration ranges of these components are; OC: 0.76–7.1 μg m−3 (av. 1.7 ± 1.0 μg m−3), EC: 0.07–0.96 μg m−3 (0.28 ± 0.19 μg m−3), WSOC: 0.27–1.9 μg m−3 (0.73 ± 0.38 μg m−3), WSTN: 0.77 to 3.0 μg m−3 (0.58 ± 0.46 μg m−3) and WSON: 0.0–2.2 μg m−3 (0.12 ± 0.23 μg m−3). Higher OC concentrations were obtained in active biota seasons; spring (av. 2.4 μg m−3) and summer (1.8 μg m−3). EC and WSOC concentrations maximized in spring (av. 0.41 μg m−3 and 0.95 μg m−3, respectively) followed by winter (0. 70 and 0.90 μg m−3) whereas they became lowest in summer (0.19 and 0.52 μg m−3). In contrast, WSTN concentrations were highest in winter (0.86 μg m−3) and lowest in summer (0.37 μg m−3) and autumn (0.34 μg m−3). Concentrations of WSON are higher in early summer (av. 0.26 μg m−3) due to the emission from marine biota. The high ratios of OC / EC (av. 7.6) and WSOC / OC (44%) suggest a secondary formation of organic aerosols. Strong correlation between OC and MSA- (0.81) in spring suggests that springtime aerosols are influenced by additional marine and terrestrial biogenic sources. The positive correlation of Ca2+ and TSP in spring (r = = 0.81) demonstrates a significant contribution of Asian dust whereas high abundances of NO3- and nss-SO42- in winter suggest an important contribution from anthropogenic sources including biomass burning, vehicular emission and coal combustion. NH4-N/WSTN ratios peaked in winter (0.56), indicating a significant contribution of biomass burning to WSTN in cold season. In contrast, higher NO3-N/WSTN ratio in spring than winter suggests that the atmospheric transport of vehicular emissions maximizes in spring. Correlation analyses of major ions suggest that NH4+ and Ca2+ play major role in the neutralization of acidic aerosols forming NH4HSO4, (NH4)2SO4 and CaSO4.

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.

Soil Organic Carbon Transformation and Related Properties in Urban Soil Under Impervious Surfaces

Installation of impervious surface in urban area prevents the exchange of material and energy between soil and other environmental counterparts, thereby resulting in negative effects on soil function and urban environment. Soil samples were collected at 0-20 cm depth in Nanjing City, China, in which seven sites were selected for urban open soils, and fourteen sites with similar parent material were selected for the impervious-covered soils, to examine the effect of impervious surface on soil properties and microbial activities, and to determine the most important soil properties associated with soil organic carbon (SOC) transformation in the urban soils covered by impervious surfaces. Soil organic carbon and water-soluble organic carbon (WSOC) concentrations, potential carbon (C) and nitrogen (N) mineralization rates, basal respiration, and physicochemical properties with respect to C transformation were measured. Installation of impervious surface severely affected soil physicochemical properties and microbial activities, e.g., it significantly decreased total N contents, potential C mineralization and basal respiration rate (P < 0.01), while increased pH, clay and Olsen-P concentrations. Soil organic carbon in the sealed soils at 0-20 cm was 2.35 kg m−2, which was significantly lower than the value of 4.52 kg m−2 in the open soils (P < 0.05). Canonical correlation analysis showed WSOC played a major role in determining SOC transformation in the impervious-covered soil, and it was highly correlated with total N content and potential C mineralization rate. These findings demonstrate that installation of impervious surface in urban area, which will result in decreases of SOC and total N concentrations and soil microbial activities, has certain negative consequences for soil fertility and long-term storage of SOC.

Quantitative LC–MS for water-soluble heterocyclic amines in fine aerosols (PM2.5) at Duke Forest, USA

A quantitative liquid chromatography–mass spectrometry (LC–MS) technique was developed to measure the concentrations of heterocyclic nitrogen compounds in ambient fine aerosols (PM2.5). Quadrupole time-of-flight (Q-TOF) MS technology was used to provide both accurate-mass and MS/MS data for confirmation of chemical formula and nitrogen compound structure. The fine aerosol was collected over the winter and summer seasons at an experimental monitoring station at Duke Forest in North Carolina U.S.A. 3-Hydroxypyridine and two β-carbolines, harmane, and norharmane, were observed in both campaigns at concentrations lower in summer (sum = 332 pg m−3; N = 27) than winter (554 pg m−3; N = 31). Aminopyridines, dimethylpyrazoles, and hydroxymethyl-pyridines were observed in the winter aerosols with a total estimated average concentration of 779 pg m−3. These results demonstrate the possibility of enhanced speciation and provide a first glance at heterocyclic amines in the water-soluble organic nitrogen (ON) fraction of fine aerosols collected from a forest atmosphere.

不同施肥对雷竹林径流及渗漏水中氮形态流失的影响

Heavy winter mulching to increase soil temperature and winter fertilization are widely used techniques for intensive management of Phyllostachys praecox forests to increase bamboo shoot production and economic return for landowners in subtropical China. The application of excessive mineral fertilizer has resulted in serious water pollution. The object of this study was to ascertain effects of reducing inorganic fertilizer rate or applying organic fertilizer on reducing the loss loads of different forms of nitrogen under Phyllostachy praecox stands by conducting a field experiment in main production area of Lin'an city,Zhejiang province. Four treatments were respective 1) control with zero fertilizer( CK),2)conventional fertilizer( CF) at the rate of N + P2O5+ K2O = 850 + 337. 5 + 337. 5 kg / hm2provided with 2250 kg / hm2of compound fertilizer and 1110 kg / hm2of urea,3) decreasing inorganic fertilizer( DI) at the rate of N+P2O5+K2O = 510 +337. 5 + 337. 5 kg / hm2provided with 2250 kg / hm2of compound fertilizer and 376 kg / hm2of urea,and 4) decreasing organic and inorganic fertilizer( DOI) at the rate of N+P2O5+K2O = 510+259. 8+165. 4 kg / hm2provided with 554 kg / hm2of urea and 46400 kg / hm2of pig manure. Fertilizer were separately applied in May 18th,September 7thand November 9th with respective 40%,30% and 30% of total amount of fertilizer,and then plowed into soil at the depth of 5 cm. Water samples from runoff and leaching water were collected by special devices,totally 16 runoff water samples and 10 seepage water samples were collected around the year 2012. It was shown that the concentrations of different forms of nitrogen actually affected by rainfall,especially for particulate nitrogen( PN) in the runoff water. The concentrations of nitrate nitrogen( NO-3-N),water-soluble organic nitrogen( WSON) and PN in the runoff water were at the range of 3. 82—6. 82mg / L,0. 89—1. 85 mg / L,and 0. 89—1. 83 mg / L,respectively,which accounting for 60. 9% —68. 2%,16. 0% —18. 1%,and 15. 1% —21. 6% of total N loss,respectively. The concentrations of NO-3-N,ammonium nitrogen( NH+4-N),and WSON in the seepage water were 26. 2—92. 5 mg / L,0. 50—6. 42 mg / L and 6. 57—12. 6 mg / L,respectively,which accounting for 75. 8% —82. 9%,1. 50% —6. 36% and 11. 2% —20. 6% of total N loss,respectively. Nitrate N was among the largest loss both in runoff water and seepage water. The loss loads of total N in the runoff water respectively decreased by46. 9% and 23. 1% for DI and DOI treatments compared with CF,and the corresponding data for seepage water were19. 1% and 52. 1%. In conclusion,decreasing inorganic fertilizer or decreasing organic and inorganic fertilizer play a remarkable role on reducing the loss loads of different forms of N under Phyllostachy praecox stands suggesting that reducing inorganic fertilizer rate and applying organic fertilizer was the useful practice to decrease the N loss.