Source Of NH3 Research Articles

Development of current and future high-resolution gridded emission inventory of anthropogenic air pollutants for urban air quality studies in Hanoi, Vietnam

A high-resolution (1 km × 1 km) emission inventory was developed for Hanoi for 2017 and 2018. The total annual emissions of PM2.5, BC, OC, NOx, SO2, NMVOC, NH3, CH4, and CO were 14.9, 1.6, 2.9, 56.7, 19.1, 109.2, 23.0, 37.9, and 472.7 Gg, respectively. Transportation, industry, and agriculture contributed 89.1%, 92.2%, and 81.3% to the total emissions of PM2.5, BC, and OC, respectively. Transportation contributed 72.4%, 52.1%, and 72.5% to the emissions of NOx, NMVOC, and CO, respectively. Industry contributed 64.9% to the emissions of SO2. Agriculture was a major source of NH3 and CH4, contributing 84.2% and 76.6%, respectively. Future emissions of select sectors were estimated for 2030. The emissions from transportation can increase in the range of 26.9% (CH4) to 245.8% (NH3), despite the consideration of the EURO 5 standard. For domestic cooking, transitioning from coal to liquefied petroleum gas can help reduce the emissions of most pollutants in the range of 10.4% (NH3) to 52.6% (OC), except NOx and NMVOC. The crop residue burning (CRB) ban could reduce emissions in the range of 0.27 Gg (SO2) to 138.4 Gg (CO) in 2030, respectively. The study can help policy-makers to develop strategies for air pollution mitigation in developing economies such as Hanoi.

Mitigating Ammonia and Greenhouse Gas Emissions from Stored Pig Slurry Using Chemical Additives and Biochars

Slurry storage is a significant source of NH3 and greenhouse gas (GHG) emissions. The aim of this laboratory study was to assess the effects of different chemical additives and biochars on the emissions of NH3, N2O, CO2, and CH4 during the short-term storage of pig slurry. The experiment was performed using Kilner jars filled with raw slurry as control and six treatment additives (5% w/w): acidified slurry, alkalinized slurry, neutralized slurry, agroforestry biochar, cardoon biochar, and elderberry biochar. The gas emissions were measured for 30 days, and the composition of the slurries was determined. During short-term storage, the results of this laboratory study indicated that the NH3 emissions were reduced by 58% by acidification and by 20% by the biochars (Agroforestry, Cardoon, and Elderberry treatments), while neutralization reduced this loss by only 12%. Nitrous oxide emissions were not reduced by the chemical additives (Acidified, Alkalinized, and Neutralized treatments), while this loss was increased by 12% by the biochars. Carbon dioxide, CH4, and global warming potential emissions were not affected by the chemical additives and biochars. Furthermore, the absence of differences between the biochars may be related to their similar composition. Regarding the influence of the studied additives on NH3 losses, it can be concluded that acidification was the best mitigation measure and the biochars were quite similar due to their composition. Furthermore, neutralization had the advantage of sanitizing the slurry, but only had a mild impact on NH3 preservation.

Isotopic characteristics and source analysis of atmospheric ammonia during agricultural periods in the Xichuan area of the Danjiangkou Reservoir

Nitrogen deposition is an important means of exogenous nitrogen input in reservoir water. Agricultural activities around the reservoir lead to a sharp increase in the concentration of ammonia in the atmosphere, which poses a threat to the reservoir water body. Clarifying the contribution of agricultural ammonia release to atmospheric NHx (gaseous NH3 and particulate NH4+), in the reservoir area can provide a theoretical foundation for local reactive nitrogen control. We collected atmospheric NH3 and NH4+ samples during the agricultural periods and analyzed the isotopic characteristics of atmospheric NHx and the contribution rates of different ammonia sources in the Xichuan area of the Danjiangkou Reservoir. The results showed that the initial δ15N values of NH3 (–30.0‰ to –7.2‰) and particulate NH4+(–33‰ to +4.9‰ for finer and coarser particles, respectively) are different, and their contribution ratios from dissimilar ammonia sources are also different, among which NH4+ is more susceptible to meteorological factors. However, since the atmospheric NHx in the Xichuan area is mainly gaseous NH3, the final sources of atmospheric ammonia nitrogen source depend on gaseous NH3. Agricultural sources (59%-74%) were the main NH3 sources in this area. Among them, the fertilizer use emission was dominant; it had the highest contribution rate in summer during the agricultural period and a more prominent impact in areas with less human interference. Reasonable regulation of the application of high-ammonia releasing fertilizer, especially during the agricultural period in summer, is an effective way to reduce the threat of atmospheric ammonia to water health.

Nitrogen isotopes indicate vehicle emissions and biomass burning dominate ambient ammonia across Colorado's Front Range urban corridor

Urban ammonia (NH3) emissions contribute to poor local air quality and can be transported to rural landscapes, impacting sensitive ecosystems. The Colorado Front Range urban corridor encompasses the Denver Metropolitan Area, rural farmland/rangeland and montane forest between the city and the Rocky Mountains. Reactive nitrogen emissions from the corridor are partly responsible for increased N deposition to the wildland-urban interface (WUI) in this region. To determine the significance of individual NH3 sources to WUI ecosystems, we measured the concentration and isotopic composition (δ15N–NH3) of ambient NH3(g) from April to October 2018 across a five-site urban to rural gradient in the corridor. The urban sites had higher NH3 concentrations and δ15N–NH3 values than the rural/suburban sites. Based on isotope mixing models, NH3 emission source contributions for all sites were fertilizer (12 ± 5.7%), livestock waste (18 ± 12%), vehicles (37 ± 23%), and biomass burning (34 ± 20%). Vehicle contributions were consistent across all months with an average of 35% and summer months showed a peak in biomass burning contributions (40%). As wildfires are projected to increase due to climate change, we stress a need for constraints on the isotopic signature of NH3 emitted from wildfires. Vehicle emissions contributed the greatest amount of NH3 (40%) at the urban sites while rural/suburban sites had higher agricultural contributions (41%). Had 2018 not had an anomalously high wildfire season, 46% and 60% of the NH3 would have been attributed to vehicle emissions at the WUI site and urban sites, respectively. NH3 emissions have historically been ascribed to agricultural activities but these findings illustrate the universal significance of vehicle emissions and the potential for sustained wildfire activity to be a primary contributor to NH3. Air quality (e.g., particulate matter) and nitrogen deposition reduction plans may benefit by including management practices that address vehicle NH3 emissions.

Isotopic imprints of aerosol ammonium over the north China plain

Atmospheric PM2.5 poses a variety of health and environmental risks to urban environments. Ammonium is one of the main components of PM2.5, and its role in PM2.5 pollution will likely increase in the coming years as NH3 emissions are still unregulated and rising in many cities worldwide. However, partitioning urban NH4+ sources remains challenging. Although the 15N natural abundance (δ15N) analysis is a promising approach for this purpose, it has seldom been applied across multiple cities within a given region. This limits our understanding of the regional patterns and controls of NH4+ sources in urban environments. Here, we collected PM2.5 samples using an active sampling technique during winter at six cities in the North China Plain to characterize the concentrations, δ15N and sources of NH4+ in PM2.5. We found substantial variations in both the concentrations and δ15N of NH4+ among the sites. The mean NH4+ concentrations across the six cities ranged from 3.6 to 12.1 μg m−3 on polluted days and from 0.9 to 10.6 μg m−3 on non-polluted days. The δ15N ranged from 6.5‰ to 13.9‰ on polluted days and from 8.7‰ to 13.5‰ on non-polluted days. The δ15N decreased with increasing NH4+ concentrations at all six sites. We found that non-agricultural sources (vehicle exhaust, ammonia slip and urban wastes) contributed 72%–94% and 56%–86% of the NH4+ on polluted and non-polluted days, respectively, and that during polluted days, combustion-related emissions (vehicle exhaust and ammonia slip) were positively associated with the proportion of urban area, population density and number of vehicles, highlighting the importance of local sources of particulate pollution. This study suggests that the analysis of 15N in aerosol NH4+ is a promising approach for apportioning atmospheric NH3 sources over a large region, and this approach has potential for mapping rapidly and precisely the sources of NH3 emissions.

NH3 spatiotemporal variability over Paris, Mexico City, and Toronto, and its link to PM2.5 during pollution events

Abstract. Megacities can experience high levels of fine particulate matter (PM2.5) pollution linked to ammonia (NH3) mainly emitted from agricultural activities. Here, we investigate such pollution in the cities of Paris, Mexico, and Toronto, each of which have distinct emission sources, agricultural regulations, and topography. Ten years of measurements from the infrared atmospheric sounding interferometer (IASI) are used to assess the spatiotemporal NH3 variability over and around the three cities. In Europe and North America, we determine that temperature is associated with the increase in NH3 atmospheric concentrations with a coefficient of determination (r2) of 0.8 over agricultural areas. The variety of the NH3 sources (industry and agricultural) and the weaker temperature seasonal cycle in southern North America induce a lower correlation factor (r2=0.5). The three regions are subject to long-range transport of NH3, as shown using HYSPLIT cluster back trajectories. The highest NH3 concentrations measured at the city scale are associated with air masses coming from the surrounding and north/northeast regions of Paris, the south/southwest areas of Toronto, and the southeast/southwest zones of Mexico City. Using NH3 and PM2.5 measurements derived from IASI and surface observations from 2008 to 2017, annually frequent pollution events are identified in the three cities. Wind roses reveal statistical patterns during these pollution events with dominant northeast/southwest directions in Paris and Mexico City, and the transboundary transport of pollutants from the United States in Toronto. To check how well chemistry transport models perform during pollution events, we evaluate simulations made using the GEOS-Chem model for March 2011. In these simulations we find that NH3 concentrations are underestimated overall, though day-to-day variability is well represented. PM2.5 is generally underestimated over Paris and Mexico City, but overestimated over Toronto.

2011-2020 trends of urban and regional ammonia in and around Barcelona, NE Spain.

It is well established that in environments where NH3 abundance is limiting in secondary PM2.5 generation, a reduction of NH3 emissions can result in an important contribution to air quality control. However, as deduced from open data published by the European Environmental Agency, the availability of measurements of NH3 concentrations is very scarce, with very few countries in Europe reporting data consistently for extensive periods, this being especially true for urban background sites. In this framework, simultaneous multi-site measurements were carried out in NE (Northeast) Spain from 2011 to 2020, using diffusion tubes. The highest NH3 concentrations were recorded at the traffic site (5.3μgm-3 on average), followed by those measured at the urban background site (2.1μgm-3). Mean concentrations at the mountain site were 1.6μgm-3, while the lowest concentrations were recorded at the regional site (0.9μgm-3). This comparison highlights traffic emissions as an important source of NH3. A statistically significant time trend of this pollutant was observed at the urban background site, increasing by 9.4% per year. A season-separated analysis also revealed a significant increasing trend at the mountain site during summer periods, probably related with increasing emissions from agricultural/livestock activities. These increases in NH3 concentrations were hypothesized to be responsible for the lack of a decreasing trend of NO3- concentrations at the monitoring sites, in spite of a markedly reduction of NO2 during the period, especially at the urban background. Thus, this would in turn affect the effectiveness of current action plans to abate fine aerosols, largely made up of secondary compounds. Actions to reduce NH3 concentrations at urban backgrounds are challenging though, as predicting NH3 is subjected to a high uncertainty and complexity due to its dependence on a variety of factors. This complexity was clearly indicated by the application of a decision tree algorithm to find the parameters better predicting NH3 at the urban background under study. O3, NO, NO2, CO, SO2 and OM+EC concentrations, together with meteorological indicators, were used as independent variables, obtaining no combination of parameters evidently able to predict significant differences in NH3 concentrations, with a coefficient of determination between real and predicted measurements lower than 0.50. This emphasizes the need for highly temporally and spatially resolved NH3 measurements for an accurate design of abatement actions.

15N Natural Abundance Characteristics of Ammonia Volatilization from Soils Applied by Different Types of Fertilizer

Ammonia (NH3) volatilized from cropland significantly impacts the ecological environment and human health. The identification and quantification of atmospheric sources of NH3 from cropland are therefore important for NH3 emission reduction and air pollution control. Choosing appropriate nitrogen (N) fertilizer types is one of the key ways to reduce NH3 emissions from agricultural systems due to different N fertilizers with different emission factors. The natural abundance isotope of N (δ15N) values can well identify the source of NH3 volatilization, although there is rare research on δ15N-NH3 values volatilized when applying different types of N fertilizers. Here, we conducted an incubation experiment to study the characteristics of δ15N-NH3 values during the whole volatilization process after different N fertilizers were applied to the soil. The results show that the cumulative NH3 volatilization from urea (U), urease inhibitor fertilizer (UI), compound fertilizer (CF) and ammonium nitrate phosphate fertilizer (AP) treatment was 5.25 ± 0.00, 3.11 ± 0.00, 3.22 ± 0.19 and 1.38 ± 0.12 kg N ha−1 at the end of the 15-day incubation period, respectively. The average δ15N value of NH3 volatilized from the U, UI, CF and AP treatments was −36.02 ± 4.95, −29.08 ± 9.70, −35.18 ± 4.98 and −29.42 ± 4.33‰, respectively. Generally, the δ15N-NH3 values ranged from −41.33 to −6.30‰ during the NH3 volatilization process. The δ15N-NH3 value was lower in the U treatment than in the UI and AP treatments (p < 0.05), which suggests that N forms and the slow-release additions of different fertilizers, such as NO3−-N and urease inhibitors, can delay or slow down NH3 volatilization, resulting in relative isotopic enrichment. Therefore, the basic properties of different N fertilizers, the changes in soil NH4+-N and cumulative NH3 during the volatilization process significantly impacted the δ15N-NH3 values.

Model for calculating ammonia emission from stored animal liquid manure

Ammonia (NH3) emissions from agriculture have increased by 90% from 1970 to 2005, and agriculture is now the largest source of NH3 to the atmosphere. Calculated national NH3 emissions from agriculture using static emission factors do not reflect regional conditions. We propose, parameterize and test a simple model to calculate emission rates which incorporates effects of temperature, pH, total ammoniacal nitrogen (TAN) concentration, exposed storage area, and storage cover. This is the first time that several known algorithms were combined in this semi-dynamic user-friendly model concept and that model parameters (uploaded on the internet) were estimated from a unique database comprising 44 studies. The calculator is designed to be used correctly even if there exists only little knowledge about manure chemistry or micrometeorology, and can calculate emissions with a low demand for input data Calculations using the new model are as accurate as the standard method. The proposed approach has two advantages compared to the standard alternative: it does not require an estimate of TAN flow through the store, and calculated values reflect management (e.g., storage area or covers), TAN concentration, pH and temperature based on well-established principles. The simple and process-related approach has the potential to deliver more accurate estimates after a more precise parameterization from dedicated studies where the focus is on emission measurements, slurry composition characterization, air and slurry temperature and turbulence. To facilitate this approach, data need to be collected over relatively short time intervals (less than twice per day) to ensure that they cover cardinal diurnal conditions at the same time and right place. A spreadsheet implementation of the model is publicly available from https://github.com/sashahafner/AMOSTO.

Is fertilization the dominant source of ammonia in the urban atmosphere?

It was previously believed that ammonia (NH3) has a short residence time in the atmosphere and cannot be transported far from its sources. In late March, however, this study observed a severe NH3 episode in urban Beijing when fertilizer was intensively applied on the North China Plain, with the highest hourly concentrations of 66.9 μg m-3 throughout the year. The stable nitrogen isotopic composition of NH3 (δ15N-NH3) during this episode (-37.0 to -20.0‰) fell in the range of endmembers of fertilizer and livestock, suggesting the long-range transport of NH3 from agricultural to urban regions. Based on a Bayesian isotope mixing model, the contribution of agriculture (fertilization) to urban NH3 concentrations was apportioned as 43.5% (26.0%) on polluted days. However, these contributions were reduced to 29.1% (12.8%) when nitrogen isotope fractionation between NH3 and ammonium was considered. In contrast to the limited contribution of agricultural sources, we found that nonagricultural emissions, particularly vehicles, dominate the source of NH3 in urban Beijing, even during the fertilization period. This finding indicated that nonagricultural sources should be considered when designing a control strategy for NH3 to reduce haze pollution in the urban atmosphere.

Isotopic Variability of Ammonia (δ15N-NH3) Slipped from Heavy-Duty Vehicles under Real-World Conditions

The widespread use of urea-SCR (selective catalytic reduction) aftertreatment to meet stringent heavy-duty vehicle (HDV) NOx emission standards has worldwide led to increased exhaust ammonia (NH3) slip. A prerequisite for the nitrogen (N) stable isotope (δ15N)-based source apportionment of ambient NH3 is that the N isotopic signatures of NH3 sources be well characterized. However, knowledge of δ15N values from HDV-emitted NH3 is still lacking. Using an on-board HDV emission measurement system, tailpipe-emitted gaseous NH3 from eight HDVs was collected during real-world driving conditions, and δ15N values were analyzed. We tentatively report an average δ15N-NH3 [mean ± 1σ = (−1.74 ± 6.27)‰] that is significantly higher (and hence potentially of diagnostic value) than that of naturally occurring volatile NH3 sources (less than −26‰) but only slightly lower than that of gasoline vehicles equipped with three-way catalytic converters. The observed variations in measured HDV δ15N-NH3 can be largely explained by the differential N-isotope fractionation during NH3 formation and the extent of ammonia conversion. We found that minor changes in SCR efficiency can cause relatively large fluctuations in δ15N-NH3, highlighting the difficulties and/or limitations with regard to attributing a characteristic δ15N to tailpipe NH3 in N-isotope balances and source partitioning efforts.

Lewis acid–dominated aqueous electrolyte acting as co-catalyst and overcoming N2 activation issues on catalyst surface

The growing demands for ammonia in agriculture and transportation fuel stimulate researchers to develop sustainable electrochemical methods to synthesize ammonia ambiently, to get past the energy-intensive Haber-Bosch process. However, the conventionally used aqueous electrolytes limit N2 solubility, leading to insufficient reactant molecules in the vicinity of the catalyst during electrochemical nitrogen reduction reaction (NRR). This hampers the yield and production rate of ammonia, irrespective of how efficient the catalyst is. Herein, we introduce an aqueous electrolyte (NaBF4), which not only acts as an N2-carrier in the medium but also works as a full-fledged "co-catalyst" along with our active material MnN4 to deliver a high yield of NH3 (328.59 μg h-1 mgcat-1) at 0.0 V versus reversible hydrogen electrode. BF3-induced charge polarization shifts the metal d-band center of the MnN4 unit close to the Fermi level, inviting N2 adsorption facilely. The Lewis acidity of the free BF3 molecules further propagates their importance in polarizing the N≡N bond of the adsorbed N2 and its first protonation. This push-pull kind of electronic interaction has been confirmed from the change in d-band center values of the MnN4 site as well as charge density distribution over our active model units, which turned out to be effective enough to lower the energy barrier of the potential determining steps of NRR. Consequently, a high production rate of NH3 (2.45 × 10-9 mol s-1 cm-2) was achieved, approaching the industrial scale where the source of NH3 was thoroughly studied and confirmed to be chiefly from the electrochemical reduction of the purged N2 gas.

A survey of deuterated ammonia in the Cepheus star-forming region L1251

ABSTRACT Understanding the chemical processes during starless core and prestellar core evolution is an important step in understanding the initial stages of star and disc formation. This project is a study of deuterated ammonia, o-NH2D, in the L1251 star-forming region towards Cepheus. Twenty-two dense cores (20 of which are starless or prestellar, and two of which have a protostar), previously identified by p-NH3 (1,1) observations, were targeted with the 12m Arizona Radio Observatory telescope on Kitt Peak. o-NH2D J$_{\rm {K_a} \rm {K_c}}^{\pm } =$$1_{11}^{+} \rightarrow 1_{01}^{-}$ was detected in 13 (59 per cent) of the NH3-detected cores with a median sensitivity of $\sigma _{T_{mb}} = 17$ mK. All cores detected in o-NH2D at this sensitivity have p-NH3 column densities >1014 cm−2. The o-NH2D column densities were calculated using the constant excitation temperature (CTEX) approximation while correcting for the filling fraction of the NH3 source size. The median deuterium fraction was found to be 0.11 (including 3σ upper limits). However, there are no strong, discernible trends in plots of deuterium fraction with any physical or evolutionary variables. If the cores in L1251 have similar initial chemical conditions, then this result is evidence of the cores physically evolving at different rates.

Ground-based measurements of atmospheric NH3 by Fourier transform infrared spectrometry at Hefei and comparisons with IASI data

Atmospheric ammonia (NH3) plays an important role in the formation of fine particulate matter, leading to severe environmental degradation and human health issues. In this work, ground-based Fourier transform infrared spectrometry (FTIR) observations are used to obtain the total columns of atmospheric NH3 at Hefei, China, from December 2016 to December 2020. After the presentation of the retrieval algorithm and uncertainty budget, we perform a spatio-temporal analysis of the dataset. Over the four years, NH3 columns have been increasing by 15.82% (2017–2018), 3.83% (2018–2019) and 3.68% (2019–2020). A clear seasonal cycle is observed, with the largest surface concentrations (12.93 ± 6.40 ppb) observed in June to August, and the lowest (4.08± 2.66 ppb) in November to January. The diurnal cycles of NH3 exhibit increased morning and afternoon concentrations. Interpretation of the diurnal cycles is difficult, however, the absence of a peak during rush hours, and the absence of correlation with CO and NO2 suggest that agriculture and not traffic is the main source of NH3 at Hefei. The polar plots of NH3 columns with wind and back trajectories of air masses calculated by the HYSPLIT model confirmed that agriculture was the dominant source of ammonia in four seasons, while urban anthropogenic emissions contributed to the high level of NH3 in summer over the Hefei site. We end this paper with a short validation exercise of NH3 columns retrieved from measurements of the IASI satellite data with the FTIR measurements over Hefei. Correlation coefficients (R) between the two datasets are 0.79 and 0.75 for IASI-A and IASI-B, with the slope of 0.96 and 1.10, respectively. The mean difference is −3.44 × 1015 and −3.96 × 1015 molec cm−2, with standard deviation of 7.16 × 1015 and 8.10 × 1015 molec cm−2, respectively. These results demonstrate the IASI and FTIR data, over Hefei, are in broad agreement.

Developing Nitrogen Isotopic Source Profiles of Atmospheric Ammonia for Source Apportionment of Ammonia in Urban Beijing

Atmospheric ammonia (NH3) is the key precursor in secondary particle formation, which is identified as the most abundant components of haze in Beijing in most cases. It is critical to understand the characteristics of NH3 from various emission sources and quantify each source contribution to NH3 in ambient atmosphere. Stable nitrogen (N) isotope composition (δ15N) is an effective tool to study NH3 source. However, this tool cannot be effectively applied in Beijing due to the lack of comprehensive N nitrogen isotope source profiles. Reliable source profiles are the basis of source apportionment of NH3 using the isotope mixing model. In this study, multiple NH3 source samples were collected at sites, representing six major NH3 source types in Beijing from 2017 to 2018 in four seasons. The δ15N values of 212 NH3 source samples were determined to build a local source profiles database of δ15N. NH3 from traffic source presents significantly higher δ15N values (−14.0 ± 5.4‰), distinguished from other sources. The δ15N values of other sources besides traffic were more depleted and did not clear differences (solid waste, sewage, human feces, fertilizer, and livestock for −33.6 ± 4.5‰, −34.1 ± 4.8‰, −32.2 ± 3.8‰, −35.0 ± 3.9‰, and −34.9 ± 4.4‰, respectively). These sources were classified into non-traffic source in this study. From March 2018 to March 2019, ambient NH3 samples were collected at an urban site in Beijing. With the newly developed source profiles in this study, the contribution of traffic and non-traffic sources to ambient NH3 in an urban site in Beijing was calculated using 15N isotope mass balance equations. Traffic and non-traffic sources contributed 8% and 92% to ambient NH3 in urban Beijing, respectively. The highest seasonal average contribution of traffic to ambient NH3 was found in winter (22%). Our results reveal the importance of traffic source and provide evidence for the need to control NH3 emission from traffic in urban Beijing in winter.

Sources identification of ammonium in PM2.5 during monsoon season in Dhaka, Bangladesh

Ammonia (NH3) is taken up by fine particulate matter (PM2.5), and there are concerns about its impact on the environment and health. The source of NH3, which was thought to be of agricultural sources, has recently been suspected to be non-agricultural sources in urban areas. Here, we collected PM2.5 during the monsoon season in Dhaka, Bangladesh, the most polluted city in the world, and analyzed the δ15N-NH4+ in PM2.5. As the result, the δ15N-NH4+ ranged from 9.2 ‰ to 34.4 ‰ (average: 20.7 ± 4.8 ‰), the highest of any of the averaged values annual reported in previous researches. In order to perform source analysis, the NH3 concentrations were estimated using the thermodynamic model ISORROPIA-II. The estimated concentration of NH3 gas averaged 40.8 μg/m3 (3.0–154.6 μg/m3). The contributions calculated with the mixing model to the δ15N-NH4+ values in PM2.5 in Dhaka, Bangladesh averaged 25.3 ± 14 %, 22.8 ± 10 %, 26.5 ± 15 %, and 25.4 ± 10 % for waste, fertilizer, NH3 slip, and fossil fuel combustion, respectively. Non-agricultural sources (NH3 slip, and fossil fuel combustion) accounted for almost half (51.9 %) of the contributions. In addition, the several validation tests of the isotope mixing model were also performed. For validating the uncorrected and corrected source data for δ15N-NH3, the contribution of non-agricultural sources with uncorrected source data would have been very high (>80 %), much higher than the corrected source data.

Characterization of greenhouse gas emissions and stable isotopic composition of ammonia during industrial composting process

Carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) and ammonia (NH3) emitted during the composting of livestock and poultry waste are important gaseous atmospheric pollutants. However, most previous studies on compost-related anthropogenic emissions of these gases were based on small reactor composting. Our understanding of their in situ emissions during industrial composting remains extremely limited. In order to explore the influence of gas produced by industrial composting on regional environment, we monitored CO2, CH4, N2O and NH3 emissions during industrial composting for 19 days and characterized the isotopic composition of emitted NH3. On average, the emission rates of CO2, CH4, N2O, and NH3 during the composting cycle were 86.8 g CO2-C·d-1·m-2, 9.8 g CH4-C·d-1·m-2, 3.7 mg N2O-N·d-1·m-2 and 736.6 mg NH3-N·d-1·m-2, respectively. The contribution of CH4 to daily global warming potential (GWP) was the highest (65%), followed by CO2, NH3(indirect), and N2O. Moreover, ammonia emitted from industrial compost had a mean δ15N value of -11.6‰±1.2‰ (range: -21.8‰--7.2‰). Overall, this study provided useful information for understanding greenhouse gas emission dynamics and characterizing atmospheric NH3 sources during composting process in livestock and poultry breeding areas.

Regime shift in aerosol ammonium between the rainy and dry season: Perspective from stable isotopes in bulk deposition

Atmospheric ammonia (NH3) is a precursor of the ammonium (NH4+) in rainwater and aerosol. However, relations among them are largely unknown, which preventing our understanding from the sources and spatio-temporal variability of the NH4+ in rainwater and aerosol. Concentration and stable nitrogen isotope (δ15N) of NH4+ were measured in bulk deposition to reveal the relations between rainwater-NH4+ and aerosol-NH4+ and identify NH3 sources in a tropical coastal city, Zhanjiang. During the dry season, δ15N values of NH4+ in the aerosol (aerosol-δ15N–NH4+) were enriched with increased air temperature and consistently heavier than those in the rainwater (rainwater-δ15N–NH4+), suggesting that relatively high air temperature in the tropics were dominant regulator in the dry season. The negative correlation in the Rayleigh model also evidenced that air temperature caused a kinetic fractionation (fractionation effect: −4.8 ± 0.7‰) in aerosol. By contrast, rainfall was a dominant factor on aerosol and rainwater in the rainy season, as suggested by the progressively enriched aerosol-δ15N–NH4+ and depleted rainwater-δ15N–NH4+. These scenarios were ascribed to isotopic exchange (fractionation effect: +1.0 ± 0.4‰), indicating by positive coefficients in the Rayleigh model. After considering the isotopic fractionation in aerosol, the major sources of NH3 in Zhanjiang calculated by the SIAR mixing model were volatilization of livestock waste and fertilizer (>95% in both season), followed by fossil fuel combustion (2% in the rainy season and 3% in the dry season), and biomass burning (1% in the rainy season and 1% in the dry season).

Dominant factors influencing changes in the water quantity and quality in the Dianshi Reservoir, East China

This study aims to identify the major factors affecting the water quality and quantity of the Dianshi Reservoir and to determine the potential risks facing the Dianshi Reservoir under the combined effects of climate and human activities. Multi-year data (2010 to 2019) were collected, and comparative analysis, trend analysis, Pearson correlation analysis, stable isotopes, and Morlet wavelet analysis were used conjunctively. The results showed that precipitation and runoff are the main recharge sources of the Dianshi Reservoir. The reservoir water level was mainly influenced by industrial and domestic water uses. Ammonia-nitrogen (NH4 +-N), total phosphorus (TP), total nitrogen (TN), and chemical oxygen demand (CODMn) were the main pollution indices in the Dianshi Reservoir. Animal excrement responsible for organic pollution entered the reservoir through surface runoff, while sewage discharge, fertilizer application, and leaf decomposition were the main sources of NH4 +-N, TP, and TN in the reservoir. Wavelet analysis indicated that water quality was greatly affected by the human activities before 2016, while the effects of precipitation, temperature, and evaporation gradually increased after 2016 and became the main factors after 2018. In addition, the management measures of the Dianshi Reservoir are not comprehensive, resulting in potential risks to water quantity regulation and water quality protection. It is, therefore, necessary to formulate a water regulation program and a comprehensive reservoir safety protection system.

Air Pollutants and CO2 Emissions in Industrial Parks and Evaluation of Their Green Upgrade on Regional Air Quality Improvement: A Case Study of Seven Cities in Henan Province

Although central to the promotion of regional economic development, industrial parks discharge large quantities of air pollutants and CO2, counter to the goals of air quality improvement and CO2 reductions in China. In this study, 13 industrial parks in seven cities in Henan Province were chosen to evaluate their emission of air pollutants and CO2 in 2017, their reduction potential under different green measures, and their air quality improvements under a Green Upgrade scenario. The results show that: (1) The total emissions of SO2, NOx, CO, PM10, PM2.5, VOCs and CO2 in the 13 industrial parks were 43, 39, 351, 19, 7, 18, 2 kt and 36 Mt, and would decrease by 72, 56, 19, 30, 26, 77 and 30%, respectively, under the Green Upgrade scenario. (2) The industrial process was the major source of CO, PM2.5, VOCs and NH3, whereas power plants were the largest source of SO2 and NOx, and they would be reduced by 93, 59, 94, 91, 23 and 28%, respectively, under the Green Upgrade scenario. (3) The terminal energy use sector (including industrial boilers and industrial process sources) was the main source of CO2, accounting for 75% of total CO2 emissions, and would be reduced by 76% under the Green Upgrade scenario. (4) WRF-CMAQ simulation results show that, under the Green Upgrade scenario, the concentration of PM2.5 in a transmission channel city would be improved by 1–36 μg/m3, with an annual average value of 9 μg/m3. Our results demonstrate the significant effect of the synergistic reduction in air pollutants and CO2 emissions using Green Technologies in industrial parks and the subsequent improvement in regional air quality.