Source Of NH3 Research Articles

Estimating ammonia emissions from cropland in China based on the establishment of agro-region-specific models

Estimating ammonia (NH3) volatilization from cropland can identify potential environmental risks and is also important for mitigating NH3 loss, since cropland is the major anthropogenic source of NH3. Reducing uncertainties around NH3 volatilization estimates is a key need. In this study, both a single national model and agro-region-specific models were developed to embody the variation of NH3 volatilization associated with environmental attributes and management practices for cropland in various agro-regions of China. A database with 951 field measurements across China was established to develop and evaluate the model, in which 75% of the measurements were used for model fitting and 25% were used for evaluation. The agro-region specific model had a better performance than the single national scale model, and the agro-region-specific model could successfully simulate NH3 emissions with R2 values of 0.41–0.93 as a function of crop type, N fertilizer type and rate, timing of fertilization, soil pH, clay content, bulk density, precipitation, air temperature, and soil total nitrogen content. Inputting high-resolution spatial data into the model, the NH3 emissions from China's cropland were estimated to be 4.31 Tg NH3N in the year 2015 with a 95% confidence interval of 3.64–5.64 Tg NH3N, of which paddy rice cultivation accounted for 44%, and maize and wheat cultivation contributed 20% and 16%, respectively. Notable spatial variability was also found in NH3 emissions from China's cropland due to regional differences in climate, soil and management patterns. This study showed that the accuracy of estimation of farmland NH3 emissions can be improved by taking meteorological, soil and management variables into account and inputting high-spatial-resolution data into the modeling.

Source forensics of inorganic and organic nitrogen using \u03b415N for tropospheric aerosols over Mt. Tai

Nitrogen-containing species are major components in atmospheric aerosols. However, little is known about the sources of N-containing aerosols over high mountainous regions, especially for organic nitrogen (ON). This study aims to reveal the emission sources of both inorganic and organic nitrogen in tropospheric aerosols atop Mt. Tai, China, and to improve our understanding of the N cycle imbalance in the North China Plain (NCP). Total suspended particle (TSP) samples were collected on a daytime/nighttime basis in spring 2017 and were investigated for the concentrations and stable N isotopic compositions of total nitrogen, NH4+, NO3− and ON. Our results show that the concentrations of N-containing compounds were higher in daytime than nighttime, mainly resulting from mountain–valley breezes and the changes of planetary boundary layer height. However, no significant day/nighttime changes were found for their corresponding δ15N values, indicating similar contributions from different N sources between day and night. The MixSIAR Bayesian stable isotope mixing model results suggest that the most important emission source of NH3 for aerosol NH4+ was agriculture, followed by fossil fuel-related sources, human waste and biomass burning. Aerosol NO3− was mainly formed from combustion and mobile emitted NOx. Interestingly, the isotopes of ON suggest that ON were very likely firstly of primary origin. Our study reveals the characteristics of reactive N emission sources and helps understand the regional transport of tropospheric N-containing aerosols in the NCP.

Predicción in vitro del estrés de Vallisneria americana Michx. por enriquecimiento de iones amonio y nitrato

El enriquecimiento de nutrientes es un factor de estrés involucrado en la declinación de vegetación sumergida. Sin embargo, la sensibilidad fisiológica o toxicológica de los genotipos varía debido a las interacciones microbióticas y el desbalance fisicoquímico del agua, las cuales han sido abordadas mediante una aproximación reduccionista y experimentos controlados. El objetivo del estudio fue evaluar, en un modelo de cultivo in vitro de Vallisneria americana, diferentes fuentes y concentraciones de N sobre la supervivencia y el crecimiento de hojas y raíces. Las plantas juveniles in vitro se expusieron a concentraciones de 500 a 2 000 µg L−1 de N total con fuentes de NH4, NO3 y NH4:NO3 (1:1) en un diseño factorial 4 x 3, en evaluaciones de corto y mediano plazo. La supervivencia fue inversamente proporcional a los síntomas de clorosis, necrosis o ruptura de tejidos. La primera elongación foliar se midió con un método no destructivo. Mientras que a los 25 días, se cuantificó la longitud individual y promedio de hojas y raíces, número de hojas regeneradas y número de raíces. Las plantas no mostraron síntomas de vulnerabilidad. El NH4 en todas sus concentraciones inhibió el crecimiento de los nueve parámetros analizados. En contraste, el NH4:NO3 causó dos inhibiciones a nivel de hoja y el NO3 estimuló todos los crecimientos de hojas y raíces. La predicción de crecimiento resulta prometedora para discriminar factores de estrés sobre la vegetación sumergida de los Pantanos de Centla.

Stable nitrogen isotopic signatures reveal the NH4+ evolution processes in pollution episodes in urban southwestern China

In most of the urban atmosphere, the formation of ammonium (NH4+) is mainly controlled by the initial isotope value of ammonia (δ15N-NH3 values) and the corresponding ammonia (NH3) conversion ratio (NH4+/(NH4+ + NH3)), as N isotope fractionation may occur under an NH3-sufficient environment. The significant influence of δ15N-NH3 values on the formation of NH4+ in the urban atmosphere has been demonstrated by many previous studies; however, exploration of the effect of the NH3 conversion ratios on NH4+ formation has been limited, especially during pollution episodes. To better understand the NH3 sources and the effect of the NH3 conversion ratios on the formation of NH4+ in the urban environment, NH4+ concentrations (0.2 to 13.4 μg·m−3, average 3.9 ± 2.8 μg·m−3) and their δ15N values (−4.0‰ to 29.2‰, average 20.6‰ ± 6.1‰) in PM2.5 were determined in the urban area of Nanning from September 1 to December 31, 2017. Based on the measured δ15N-NH4+ values and the isotope fractionation that occurred during gas-to-particle partitioning, we estimated that the initial δ15N-NH3 values were − 22.8‰ to 3.1‰ (average − 8.8‰ ± 5.5‰). These initial δ15N-NH3 values were influenced by agricultural emission sources (−31.0‰ to −4.4‰), fossil fuel-related NH3 emission sources (−14.6‰ to 10.1‰) and biomass combustion sources (12‰ and 23‰). Source apportionment indicated that these three potential NH3 emission sources contributed 43%, 33% and 24% to the ambient NH3, respectively. On clean days, similar trends in initial δ15N-NH3 and δ15N-NH4+ values were observed, and there was an apparent positive linear correlation between these values (R2 = 0.70, p < 0.01). This suggested that the δ15N-NH4+ signatures recorded changes in the NH3 sources and that NH4+ formation was controlled by the NH3 sources on clean days. However, during different pollution episodes the variations in δ15N-NH4+ values were consistent with the NH4+ concentrations and the NH4+/(NH4+ + NH3) values, and there were negative linear correlation between these values (R2 > 0.6, p < 0.01). This suggested that the δ15N-NH4+ signatures recorded NH4+ evolution processes and that the increased NH3 conversion ratios was the main reason for the development of NH4+ and PM2.5 in pollution episodes. We inferred that the decreased air temperature in cold months may stimulate the increased NH3 conversion ratios, based on the negative correlation of NH4+/(NH4+ + NH3) values with air temperature (r = −0.63, p < 0.01).

Radiatively driven NH3 release from agricultural field during wintertime slack season

A chemical ionization mass spectrometer (CIMS) was deployed to measure ambient ammonia (NH3) with a time-resolution of ~5 min. Unexpectedly high levels of NH3, peaking at 15.5 ppbv and averaging at 2.1 ± 1.9 ppbv, were observed near an agricultural field in Nanjing, China, during wintertime, a slack season for farming. Re-partitioning from aerosols can only explain a small portion of this NH3 due to the considerably low air temperature, whereas the major source was emission from soil, as indicated by significant positive correlations of the NH3 concentration with the ground surface temperature, solar radiation intensity, and particularly the surface-air temperature difference. The dissolved/adsorbed NH3 and NH4NO3 in soil likely originated from conversion of nitrogen-containing organic matter by microorganisms through ammonification and nitrification. The upward transfer of NH3 released from the soil was facilitated by convective mixing driven by solar radiation, which produced the required high soil-air temperature gradient. This winter release of NH3 from the soil is not captured by commonly used long-term, passive-sampler based methods, giving rise to an incorrect assumption that during winter, a slack season for farming, soil emits no NH3 and so this source has remained unresolved by typical emission inventory models. Our results indicate that contrary to the common assumption, agricultural background emissions are a non-negligible source of NH3 even in wintertime, which may exert a significant impact on regional air pollution formations. Hence, a refined NH3 emission inventory is critically needed to account for the haze events in wintertime northern China.

Source Apportionment of Urban Ammonia and its Contribution to Secondary Particle Formation in a Mid-size European City

ABSTRACT Ambient air pollution caused by fine particulate matter (PM) and trace gases is a pressing topic as it affects the vast majority of the world's population, with a particularly heavy influence in densely populated urban environments. Alongside nitrogen oxides (NOx) and PM, ammonia (NH3) is also a relevant air pollutant due to its role as a precursor of particulate ammonium. This is a study about the short-term temporal dynamics of urban NH3 concentrations in Munster, northwest Germany, the role of road traffic and agriculture as NH3 sources and about the importance of ammonia for secondary particle formation (SPF). The NH3 mixing ratio was rather high (mean: 17 ppb) compared to other urban areas and showed distinct diurnal maxima around 10 a.m. and during the night at 9 p.m. The main source for ammonia in Munster was agriculture, but road traffic also contributed through local emissions from vehicle catalysts. NH3 from surrounding agricultural areas accumulated in the nocturnal boundary layer and contributed to SPF in the city center. Modeled emissions of NH3 as estimated by the Handbook for Emission Factors in combination with traffic counts were in the same magnitude for NH3. The size-resolved chemical composition of inorganic ions in PM10 was dominated by NH4+ (8.66 µg m–3), followed by NO3– (3.89 µg m–3), SO42– (1.58 µg m–3) and Cl– (1.33 µg m–3). Particles in the accumulation range (diameter: 0.1–1 µm) showed the highest inorganic ion concentrations. The ammonium neutralization index J (111%) indicated an excess of NH4+ leading to mostly alkaline PM. High ammonia emissions from surrounding agricultural areas combined with large amounts of NOx from road traffic play a crucial role for SPF in Munster.

Changes of δ15N values during the volatilization process after applying urea on soil.

Ammonia (NH3) volatilized from soils plays an important role in N cycle and air pollution, thus it is important to trace the emission source and predict source contributions to development strategies mitigating the environmental harmful of soil NH3 volatilization. The measurements of 15N natural abundance (δ15N) could be used as a complementary tool for apportioning emissions sources to resolve the contribution of multiple NH3 emission sources to air NH3 pollution. However, information of the changes of δ15N-NH3 values during the whole volatilization process under different N application rates are currently lacking. Hence, to fill this gap, we conducted a 15-day incubation experiment included different urea-N application rates to determine δ15N values of NH3 during volatilization process. Results showed that volatilization process depleted 15N in NH3. The average δ15N value of NH3 volatilized from the 0, 20, 180, and 360kgN ha-1 treatment was-16.2±7.3‰,-26.0±5.4‰,-34.8±4.8‰, and-40.6±5.7‰. Overall, δ15N-NH3 values ranged from-46.0‰ to-4.7‰ during the whole volatilization process, with lower in higher urea-N application treatments than those in control. δ15N-NH3 values during the NH3 volatilization process were much lower than those of the primary sources, soil (-3.4±0.1‰) and urea (-3.6±0.1‰). Therefore, large isotopic fractionation may occur during soil volatilization process. Moreover, negative relationships between soil NH4+-N and NH3 volatilization rate and δ15N-NH3 values were observed in this study. Our results could be used as evidences of NH3 source apportionments and N cycle.

Measurement report: Short-term variation in ammonia concentrations in an urban area increased by mist evaporation and emissions from a forest canopy with bird droppings

Abstract. Local meteorological conditions and natural and anthropogenic sources affect atmospheric NH3 concentrations in urban areas. To investigate potential sources and processes of NH3 variation in urban areas, hourly NH3 and NH4+ concentrations were measured during November 2017–October 2019 in Nagoya, a central Japanese megacity. Average NH3 concentrations are high in summer and low in winter. Daily minimum NH3 concentrations are linearly correlated with daily minimum air temperatures. By contrast, daily maximum NH3 concentrations increase exponentially with temperature, suggesting that different nighttime and daytime processes and air temperatures affect concentrations. Short-term increases in NH3 concentrations of two types were examined closely. Infrequent but large increases (11 parts per billion (ppb) for 2 h) occurred after mist evaporation during daytime. During 2 years of observations, only one event of this magnitude was identified in Nagoya, although evaporation of mist and fog occurs frequently after rains. Also, short-term increases occur with a large morning peak in summer. Amplitudes of diurnal variation in NH3 concentration (daily maximum minus minimum) were analyzed on days with nonwet and low wind conditions. Amplitudes were small (ca. 2 ppb) in winter, but they increased from early summer along with new leaf growth. Amplitudes peaked in summer (ca. 20 ppb) because of droppings from hundreds of crows before roosting in trees on the campus. High daily maximum NH3 concentrations were characterized by a rapid increase occurring 2–4 h after local sunrise. In summer, peak NH3 concentrations at around 08:00 local time (LT) in sunny weather were greater than in cloudy weather, suggesting that direct sunlight particularly boosts the morning peak. Daily and seasonal findings related to the morning peak imply that stomatal emission at the site causes the increase. Differences between daily amplitudes during the two summers was explained by the different input amounts of reactive nitrogen from bird droppings and rain, suggesting that bird droppings, a temporary rich source of NH3, affected the small forest canopy.

Laboratory-based validation of a passive sampler for determination of the nitrogen stable isotope ratio of ammonia gas

Nitrogen stable isotope ratio (δ15N) analysis of ammonia gas (NH3) by using a passive sampler is expected to be useful for determining sources of NH3 and for examining environmental dynamics. However, the use of passive samplers for determining the δ15N values of NH3 obtained has not been well validated in laboratory. Here, we evaluated the reliability of the passive sampler under various simulated environmental conditions in the chamber. When the amount of NH3 collected by the sampler was <70 μg, the δ15N value obtained was approximately 10–15‰ lighter than the δ15N value of a reference NH3 gas value regardless of type of passive sampler, the temperature, or sampling chamber size. Thus, when using a passive sampler to collect NH3, if the amount of NH3 collected is < 70 μg, it is necessary to add approximately 10–15‰ to the measured value. This finding will enable determination of more accurate δ15N values, which will be meaningful for future air research.

Inverse modeling of NH3 sources using CrIS remote sensing measurements

Spatiotemporal uncertainty in emissions in the US hinders prediction of environmental effects of atmospheric . We conducted 4D-Var inversions using CrIS remote-sensing observations and GEOS-Chem to estimate monthly emissions over the contiguous US at the 0.25°× 0.3125° resolution in 2014, finding they are 33% higher than the prior emissions which likely underestimated most agricultural emissions, especially intense springtime fertilizer and livestock sources over the Central US. However, decreases were found in the Central Valley, southern Minnesota, northern Iowa and southeastern North Carolina during warm months. These updates increased the correlation coefficient between modeled monthly mean and surface observations from 0.53 to 0.84, and reduced the normalized mean bias of annual mean simulated and wet by a factor of 1.3 to 12.7. Our satellite-based inversion approach thus holds promise for improving estimates of and reactive nitrogen deposition throughout the world where measurements are scarce.

Multi-pollutant air quality analyses and apportionment of sources in three particle size categories at Taj Mahal, Agra

Taj Mahal, an iconic monument at Agra, India, is faced with the high air pollution levels, affecting its facade. A study was undertaken at the Taj Mahal (June 7–26, 2018) to measure PM2.5, PM10, TSP and their chemical composition: metals, ions, elemental and organic carbons and molecular markers (polyaromatic hydrocarbons, n-alkanes, hopanes and sterols). The objectives of the study were to (i) assess the contribution of sources to PM2.5, PM10 and TSP by employing receptor modelling (USEPA's Chemical Mass Balance model 8.2) and (ii) measure levels of reactive (NH3, SO2, NO2), acidic (HCl, HNO3) and corrosive (H2S) gases.The PM levels were: PM2.5 65 ± 13; PM10 234 ± 84 and TSP 465 ± 204 μg/m3. The percent mass of metals (32–39) was the maximum in all PM size categories followed by secondary inorganic aerosol (SIA; 6–21). PM2.5 had a substantial contribution to coal combustion and fly ash (35%), followed by vehicles (19%). The contribution of soil and road dust was maximum to PM10 (39%) and TSP (61%), followed by the contribution of coal and fly ash in PM10 (34%) and TSP (22%). The presence of HCl (9.44 ± 4.61 μg/m3) suggested the contribution of burning of coal, plastic, paper and waste. The other concern was levels of NH3 (30 ± 14 μg/m3), which adds to the formation of SIA. The major source of NH3 could be from the upstream discharges of partially treated sewage in the River Yamuna, flowing adjacent to the Taj Mahal.

Changes in ammonia and its effects on PM2.5 chemical property in three winter seasons in Beijing, China

NH3, SO2, NOx and the inorganic ions of PM2.5 in winter 2009, 2014 and 2016 were examined to investigate the change in NH3 and aerosol chemistry in Beijing, China. NH3 concentrations showed an increase by 59% on average, in contrast to the decrease of SO2 by 63% from winter 2009 to 2016. The mean mass ratio of NH3/NHx was 0.83 ± 0.12 in 2016, which is higher than those obtained in 2009 and 2014, implying more NHx remaining as free NH3 in 2016 winter. Our findings suggest that vehicles exhaust emissions are an important NH3 source in urban central atmosphere of Beijing in winter. Despite the observed NOx presenting declining trends from 2014 to 2016, nitrate concentrations even exhibited a significant increasing trend, which may be largely attributable to high NH3 levels. An in-depth analysis of measured NH3 and aerosol species in a heavy pollution episode in December 2016, combined with the acidity predicted by ISORROPIA II model demonstrated abundant NH3 most of the time in air, where NH3 is not only a precursor for NH4+ but also effect the neutralization of SO42− and NO3− in PM2.5. With high RH and low photochemical activity, elevated NO3− concentration was attributed to an enhanced heterogeneous conversion of NOx to HNO3 to form NH4NO3 in pollution transport stage. The decrease in NOx from high level and the increase in NH3, with peaks of SO42− occurring were observed in pollution cumulative stage. The aqueous-phase oxidation of SO2 by NO2 to sulfate might play an important role with high pH values. Our results suggested that the simultaneous control of NH3 emissions in conjunction with SO2 and NOx emissions would be more effective in reducing particulate matter PM2.5 formation.

Utilization of road dust chemical profiles for source identification and human health impact assessment

This study investigated the chemical profiles of fine urban road dust as a set of indicators for major air pollutants at sampling sites or as proxies for potential human health impacts. We examined the chemical compositions of fine particles (< 100 μm) or re-suspended ultrafine particles (< 2.5 μm) in the urban road dust collected from the cities with major emission sources of CO, NH3, NOx, PM2.5, SOx, and volatile organic compounds. The elemental compositions, including metal contents and volatile or semi-volatile organic compound species were determined to constitute comprehensive chemical profiles of the solid road dust samples. The water-extractable organic compounds and fluorescent species of the size-fractionated re-suspended fine particulate matter (RPM) were also incorporated in the chemical profiles. The metal content and aliphatic hydrocarbons could partly distinguish emission sources, and clearer distinctions were achieved with the inclusion of fluorescence excitation-emission matrix (EEM) results. The dose–response test results showed positive correlations between cytotoxicity and relative abundance of hydrocarbons or metal contents of urban road dust. The set of chemical profiles suggested in this study could be further utilized for site identification or human health impact assessment using urban road dust.

Improved nucleation of AlN on in situ nitrogen doped graphene for GaN quasi-van der Waals epitaxy

In the present work, improved crystal quality of GaN on a graphene-covered sapphire substrate was achieved compared to GaN grown on a bare sapphire substrate, and the growth mechanism of GaN quasi-van der Waals epitaxy with an AlN nucleation layer was clarified using metal-organic chemical vapor deposition. The in situ N-doping of graphene by an NH3 source during AlN growth was responsible for AlN nucleation. The first-principles calculation indicated that N atoms doped initially at the step edges of graphene and subsequently at its center and AlN nuclei followed the same sequence, which is consistent with experimental observations of nucleation. The lower migration barrier of Al atoms (0.07 eV) on graphene created larger AlN nuclei compared to that on bare sapphire (0.21 eV), leading to improved quality of the upper GaN epilayer with lower defect density. This work offers guidance for precisely controlling the nucleation morphology and density of GaN base materials and thus realizing high-quality epitaxial materials and related high-performance devices by quasi-van der Waals epitaxy.

A Review of Chamber and Micrometeorological Methods to Quantify NH3 Emissions from Fertilisers Field Application

Agriculture is mainly responsible for ammonia (NH3) volatilisation. A common effort to produce reliable quantifications, national emission inventories, and policies is needed to reduce health and environmental issues related to this emission. Sources of NH3 are locally distributed and mainly depend on farm building characteristics, management of excreta, and the field application of mineral fertilisers. To date, appropriate measurements related to the application of fertilisers to the field are still scarce in the literature. Proper quantification of NH3 must consider the nature of the fertiliser, the environmental variables that influence the dynamic of the emission, and a reliable measurement method. This paper presents the state of the art of the most commonly used direct methods to measure NH3 volatilisation following field application of fertilisers, mainly focusing on chamber method. The characteristics and the associated uncertainty of the measurement of the most widespread chamber types are discussed and compared to the micrometeorological methods.

Sources of gaseous NH3 in urban Beijing from parallel sampling of NH3 and NH4+, their nitrogen isotope measurement and modeling

Atmospheric gaseous ammonia (NH3) is the most abundant alkaline gas in the atmosphere while aerosol ammonium (NH4+) constitutes a majority of the inorganic cation concentration in total PM2.5 mass and plays a vital role in severe haze formation. This study tried to shed some light on sources of gaseous NH3 through integrating the parallel measurements of δ15N values in NH4+ and ambient NH3, NH3 source signature measurement, IsoSource model, and chemistry and transport model (CTM). As a result, predicted initial δ15N (NH3) values ranging from −42.0‰ to −4.9‰ were derived from daily δ15N(NH4+) values of fine particulate NH4+, and δ15N(NH3) values ranging from −26.8‰ to −17.2‰ were obtained from weekday/weekend δ15N(NH3) values, respectively. During summer, non-agricultural sources (e.g. fossil fuel sources, urban waste) contributed 63% to ambient NH3 in urban Beijing, derived from δ15N(NH3) values whereas 64% to ambient NH3, derived from δ15N(NH4+) values. These results suggested that non-agricultural sources were main contributors to gaseous NH3 even during summer and agricultural sources were not likely the main source of gaseous NH3 in urban Beijing. To further reduce the uncertainty of isotope-based source apportionment results, more laboratory and field studies are necessary to refine the δ15N(NH3) source profile of NH3 using validated collection technique as overlapping exist between δ15N(NH3) values in agricultural sources such as livestock breeding waste (−42.5‰ to −29.1‰) and fertilizer application (−51.5‰ to −35.0‰).

Comparative assessment of modeling and experimental data of ammonia removal from pre-digested chicken manure

The aim of this study was to interpret the development of Anammox activity by a mathematical model in an UASB reactor -originally inoculated with methanogenic granules- at which Anammox progress has been also experimentally observed while treating chicken manure digestate. Since ammonium is derived from anaerobic degradation of nitrogenous compounds in chicken manure similar to any other nitrogen-rich organic wastes; the reactor was operated intentionally at favorable conditions [i.e.; with external nitrite source for NH4 +:NO2 -≅1.0] in order to make Anammox process to prevail as operation continued. Results indicated significant ammonia removals (60% on average) although influent concentration was gradually increased up to 200 mg L-1. A modeling exercise has been undertaken to investigate the performance of the laboratory scale UASB reactor. In this scope, the experimental results were modeled by using Mantis2 model within GPS-X 6.5 simulation software that included several built in libraries. Accordingly, effluent chemical oxygen demand (COD) and total ammonia nitrogen (TAN) concentrations could be predicted with reasonably good accuracy demonstrating successful calibration. The regression coefficient (R2 ) and mean relative absolute error (MRAE) parameters were found as 0.66 and 16% and 0.70 and 19%, respectively.

Determining rainwater chemistry to reveal alkaline rain trend in Southwest China: Evidence from a frequent-rainy karst area with extensive agricultural production

Rainwater chemistry plays an important role in the earth-surficial ecosystem, but studies on rainwater chemical composition of karst agro-ecosystem are rare. To explore the rainwater alkalization and the provenance of components responsible for neutralization, two-years chemical monitoring of rainwater was carried out in a karst agricultural catchment in Southwest China. The main findings suggest that SO42−, NO3−, Ca2+, and NH4+ are the principal ions. All the ionic contents show distinctly seasonal variation (highest in winter) in response to variations in seasonal precipitation because the rain-scour process can efficiently remove atmospheric materials. Source identification indicates that Cl− and Na+ are mainly derived from marine input whereas SO42− and NO3− are controlled by anthropogenic emission, in particular, fixed emission sources. The source of NH4+ is attributed to intense agricultural production, while Ca2+ and Mg2+ are mainly derived from calcite dissolution. The rainwater alkalization caused by the seasonal acid neutralization (via basic components, Ca2+ and NH4+) is beneficial to crop growth but also reflect agricultural overfertilization. Sulfur controlled the total wet acid deposition (68%–94%) and could be a potential agent of weathering.

Source Apportionment of Atmospheric Ammonia: Sensitivity Test Based on Stable Isotope Analysis in R Language

Ammonia (NH3) is an important precursor of fine particles and nitrogen deposition. It is critical to identify and quantify the sources of NH3 before the implementation of a mitigation strategy. Stable isotope analysis in R (SIAR) has potential with regard to the source apportionment of NH3, but its reliability is closely related to the signatures (δ15N-NH3) of emission sources. Based on SIAR, we found that the agricultural contribution varied significantly with mean δ15N-NH3 values of endmember input. In contrast, both the contributions of fossil fuel and NH3 slip showed low sensitivity against the change of endmember input. Moreover, the agricultural contribution changed by about 20% due to the variations in agricultural endmember mean values. Such a change is five times that due to the variations in endmember standard deviation values. Notably, regardless of the number of input sources tested, "non-agricultural source" was the dominant source of NH3 during hazy days in January 2013 in Beijing. Since various agricultural sources showed large variations in δ15N-NH3, future studies should focus on the endmember signatures of agricultural sources to further reduce the uncertainty in SIAR-based NH3 source apportionment.

Research on Laser Absorption Spectrum Detection Technology for CO2 and NH3 Regional Emission

High-sensitivity emission monitoring of CO2 and NH3 in farmland region is very important for analyzing environment and climate change. The on-line detection technology was studied based on open-path tunable diode laser absorption spectroscopy technology (OP-TDLAS). The detection spectrum of open path was extracted to realize accurate concentration inversion by designing the multi-line fitting algorithm. The system detection stability was evaluated by Allan variance that the detection limit of NH3 and CO2 were about 0.048 L/L and 4.31 L/L respectively. The detection experiment was carried out in farmland of north Anhui to prove that both of the fertilization and straw returning to the field were the emission source of CO2 and NH3 from soil. The growth effect of the former was slower but higher than that of fertilization. This stable spectrum detection method can obtain large-scale concentration results and clear emission rules, which provide technical support for the environment-friendly agriculture