Atmospheric NH3 Research Articles

Risk assessment and seasonal variation of atmospheric ammonia in Ondo State, Nigeria

The environment is impacted by atmospheric ammonia (NH3) in a number of ways, including the global nitrogen cycle, ecology, and the production of secondary particles. Our findings present an unparalleled depiction of the temporal and geographical properties of atmospheric NH3 in and around this megacity, based on long-term, continuous measurements of NH3 at various locations in Ondo State. The increase in atmospheric ammonia during this anthropogenic era is believed to pose a significant threat to humanity, with scientists linking it to a rise in global warming and climate change. KP-826 multiple gas detector was used to investigate ammonia gas in five locations within Ondo state and its correlation with meteorological parameters was examined in this study. The selection of Dumpsite, Cattle rearing farm and Poultry farm was purposeful because of their involvement in the production of ammonia gas. The mean concentration of NH3 (ppm) during wet season was 3.87 ± 1.60 and for dry season was 5.87 ± 1.60. The mean temperature (°C) in wet conditions is 32.51 ± 1.27, which is a little lower than the mean (33.51 ± 1.25) in dry conditions. The mean wind speed (in m/s) during wet conditions is 1.21 ± 0.32, which is greater than the mean wind speed (in m/s) during dry conditions of 1.11 ± 0.32. The mean value of humidity for wet situations is 72.08 ± 2.31, which is a little lower than the mean value for dry conditions, which is 76.07 ± 2.31. This work evaluated the potential health risks associated with NH3. The total hazard quotient (THQ) for adult was 1.30 × 10–6 for children 1.50 × 10–6. The children's HQ ranged from 2.41 to 4.15. The adult's ranged from 8.70 to 15.13. However, it was discovered that the health risk posed by breathing in atmospheric NH3 was far higher than the USEPA limits, where HQ > 1.

Understanding the spatial patterns of atmospheric ammonia trends in South Asia

Ammonia (NH3) is the most abundant alkaline gas in the atmosphere, mainly emitted by agricultural activities. NH3 readily reacts with other atmospheric acidic pollutants, such as the oxidation products of sulfur dioxide (SO2) and nitrogen oxides (NOₓ), to create fine particulate matter, which has far-reaching effects on human health and ecosystems. Here, we investigated long-term atmospheric NH3 trends in South Asia (SA) using satellite observations from the Infrared Atmospheric Sounding Interferometer (IASI). We analyzed 15 years (2008–2022) of IASI-NH3 retrievals against climate, biophysical, and chemical variables using an ensemble of multivariate statistical methods to identify the major factors driving the observed patterns in the region. Trend analysis of IASI-NH3 data reveals a significant rise in atmospheric NH3 over 51 % of SA plains, but a downward trend over 31 % of the region. Spatial correlation analysis reveals that biophysical factors, representing cropland expansion and agriculture intensification, have the highest positive correlation over 56 % of SA plains experiencing positive NH3 trends. However, our results reveal that the chemical conversion of NH3 to ammonium compounds, driven by the positive trends in NOₓ and SO2 pollution, is driving the apparently declining trend of NH3 in the other regions. Our results provide important insights into the NH3 trends detected by satellite data and can better inform the policy design aimed at reducing NH3 emissions and improving air quality for developing regions of the world.

Atmospheric NH3 in urban Beijing: long-term variations and implications for secondary inorganic aerosol control

Abstract. Ammonia (NH3) has major effects on the environment and climate. In situ measurements of NH3 concentrations taken between June 2009 and July 2020 at an urban site in Beijing were analyzed to study its long-term behavior, responses to meteorological conditions, and influences on the formation of secondary inorganic aerosols (SIAs). The 11-year average NH3 mixing ratio was 26.9±19.3 ppb (median 23.5 ppb). The annual average NH3 mixing ratio increased from 2009 to 2017 by 50 % and then decreased by 49 % from 2017 to 2020. Notably, the long-term trend for NH3 at the ground level did not align with the trends derived from satellite observations and emission estimates. The NH3 concentration exhibited a stronger correlation with the daily variation in water vapor (H2O) concentration than with air temperature. Thermodynamic modeling revealed the nonlinear response of SIAs to NH3, with increased sensitivity when its concentration was reduced to 40 % of the initial level. Although reducing NH3 concentrations can improve air quality during winter, controlling acid gas concentrations has a greater effect than controlling NH3 concentrations on reducing SIA concentrations, until NH3 and acidic gas concentrations are reduced below 80 % of their current levels. Nevertheless, the increased mass proportion of ammonium salts in SIAs during the observation period indicates that future control measures for NH3 concentrations may need to be prioritized in Beijing.

Multi-time Scale Variation of Atmospheric Ammonia Concentration and Dry Deposition in a Paddy Rice Region in Subtropical China

Meteorological factors and anthropogenic activities significantly affect atmospheric ammonia （NH3） concentration and its dry deposition. Former studies have examined the spatial and temporal variability in atmospheric NH3 concentrations at monthly scales. However, the characteristics of atmospheric concentrations at finer time scales such as hourly and daily scales and the influencing factors remain unclear. In this study, atmospheric NH3 concentration and related meteorological factors were continuously monitored online for one year in a double cropping rice region in subtropical China, and atmospheric NH3 concentration and its meteorological influencing factors as well as dry deposition were analyzed at different time scales （hourly, daily, and monthly）. The main results were as follows： The annual average daily concentration of NH3 in the rice area varied from 0.01 to 58.0 μg·m-3 （in N, same below）, and the annual average concentration was 5.3 μg·m-3. On the hourly scale, the 24-hour dynamics of atmospheric NH3 concentration showed a unimodal pattern, and the time of the NH3 peak appearance in different seasons was different； the time of the peak that appeared in winter lagged behind that in the other seasons. From the perspective of daily scale, NH3 concentration was mainly affected by fertilization in the paddy fields, peaking at 1-3 days after fertilization and then gradually decreasing. On the monthly scale, NH3 concentration peaked at 12.8 μg·m-3 in July and was the lowest in October at 1.6 μg·m-3. On the hourly scale, NH3 concentration varied seasonally due to the influences of meteorological factors, mainly as follows： NH3 concentration showed significant positive correlations with air temperature and solar radiation in all four seasons and with wind speed in spring and summer, whereas it showed significant negative correlations with relative humidity except in winter. On the daily scale, NH3 concentration showed a significant positive correlation with air temperature, rainfall, and solar radiation, whereas it showed a significant negative correlation with relative humidity. On the monthly scale, no significant correlation existed between each meteorological factor and NH3 concentration. The annual dry deposition flux （in N） calculated from the hourly average NH3 concentration was 8.5 kg·（hm2·a）-1, which was 11.6% higher than the annual flux calculated from the daily average and 12.4% higher than the annual flux calculated from the monthly average. In summary, there were significant daily and seasonal variations in atmospheric NH3 concentration in the paddy rice region in subtropical China, and conducting hourly-scale observations of NH3 concentration can help to reveal the multi-time scale variations in NH3 concentration and to quantify NH3 dry deposition more accurately.

Sources and processes affecting the abundances of atmospheric NHx using δ15N over northwestern Indo-Gangetic plain

Ammonia (NH3) is the major constituent among all the reactive nitrogen species present in the atmosphere, and the most essential species for secondary inorganic aerosol formation. Recent satellite-based observations have identified the Indo-Gangetic Plain (IGP) as a major hotspot of global NH3 emission; however, the major sources and atmospheric processes affecting its abundance are poorly understood. The present study aims to understand the wintertime sources of NH3 over a semi-urban site (Patiala, 30.3°N, 76.4°E, 249 m amsl) located in the IGP using species specific δ15N in PM2.5. A distinct diurnal variation in the stable isotopic signature of total nitrogen (δ15N-TN) and ammonium (δ15N–NH4+) were observed; although, average day and night time concentrations of TN and NH4+ were similar. Mixing model results using δ15N–NH3 reveal the dominance of non-agricultural emissions (NH3 slip: 47 ± 24%) over agricultural emissions (24 ± 11%), combustion sources (19 ± 14 %), and biomass burning (10 ± 8%) for atmospheric NH3. Diurnal variability in source contributions to NH3 was insignificant. Further, significantly negative correlations of δ15N–NH4+ with ambient relative humidity (RH) and daytime NO3−-N concentration were observed, and attributed to the possibility of NH4NO3 volatilization during day-time owing to lower RH and higher temperature, resulting in isotopic enrichment of the remaining NH4+ in aerosol phase. This study, a first of its type from India, highlights the importance of non-agricultural NH3 emissions over the agriculture dominated IGP region, and the role of local meteorology on the isotopic fractionation of δ15N in aerosol NH4+.

A Decadal Change in Atmospheric Nitrogen Deposition at a Rural Site in Southern China

Elevated atmospheric reactive nitrogen (Nr) emissions and the subsequent nitrogen (N) deposition have negatively impacted the global environment, particularly in China. In order to assess the long-term trends in atmospheric N deposition in the south of China, Taojiang County in Hunan Province was selected as a representative rural area for study. We analyzed interannual variation in atmospheric Nr, including gaseous ammonia (NH3), nitrogen dioxide (NO2), nitrate acid (HNO3) vapor, particulate ammonium (NH4+), and nitrate (NO3−) in air and NH4+-N and NO3−-N in precipitation from 2011 to 2020. The 10-year average atmospheric wet-plus-dry N deposition was 41.9 kg N ha−1 yr−1, which decreased by approximately 24% after 2012, indicating that NH3 and NOx emissions were effectively reduced by emission controls introduced in 2013. Wet deposition accounted for approximately 74% of the total N deposition and was significantly influenced by annual precipitation amount. Reduced N (NH3, pNH4+, and NH4+ in rainwater) was the dominant form, comprising approximately 58% of the total N deposition, while oxidized N (pNO3−, NO2, HNO3, and NO3− in rainwater) accounted for 42% of the total N deposition. Atmospheric HNO3, NO2, and NH3 concentrations and deposition declined by 30–80% over the decade, while particulate NH4+ and NO3− concentrations and deposition remained at relatively stable levels, which suggests that ongoing research and policy should focus on rural particulate pollution. Future strategies must concentrate on the integrated control of NH3 and NOx emissions to mitigate air pollution and protect human health, particularly in rural areas because current abatement efforts are primarily directed toward urban areas and the industrial sector, whereas non-point source NH3 pollution, influenced mainly by agricultural activities, dominates in rural regions.

Multifunctional Polypyrrole-Based Textile Sensors for Integration into Personal Protection Equipment.

Integrated safety sensors for personal protection equipment increasingly attract research activities as there is a high need for workers in delicate situations to be physically monitored in order to avoid accidents. In this work, we present a simple approach to generate thin, homogeneous polypyrrole (PPy) layers on flexible textile polyamide fabrics. PPy layers of 0.5-1 µm were deposited on the fabric, which thus kept its flexibility. The conductive layers are multifunctional and can act as temperature and gas sensors for the detection of corrosive gases such as HCl and NH3. Using three examples of life-threatening environments, we were able to monitor temperature, atmospheric NH3 and HCl within critical ranges, i.e., 100 to 400 ppm for ammonia and 20 to 100 ppm for HCl. In the presence of HCl, a decrease in resistance was observed, while gaseous NH3 led to an increase in resistance. The sensor signal thus allows for distinguishing between these two gases and indicating critical concentrations. The simple and cheap manufacturing of such PPy sensors is of substantial interest for the future design of multifunction functional sensors in protective clothing.

Source apportionment of atmospheric ammonia in suburban Beijing revealed through 15N-stable isotopes

Addressing the urgent issue of atmospheric ammonia (NH3) emissions is crucial in combating poor air quality in megacities. Previous research has highlighted the significant contribution of nonagricultural sources, particularly fossil fuel emissions, to urban NH3 levels. However, there is limited assessment of NH3 dynamics in suburban areas. This study focuses on four suburban sites in Beijing, covering a 16 to 22-month observation period, to investigate spatial and temporal patterns of NH3 concentrations. The δ15N-stable isotope method is employed to identify NH3 sources and their contributions. Our results demonstrate that agricultural sources (53 %) dominate atmospheric NH3 emissions in suburban areas of Beijing, surpassing nonagricultural sources, and primarily emanate from local sources. Notably, fertilizer application (37 ± 11 %) and livestock breeding (32 ± 6 %) emerge as the primary contributors in summer and spring, respectively, leading to significantly elevated NH3 concentrations during these seasons. Even in autumn and winter, both agricultural (49 %) and nonagricultural (51 %) sources contribute almost equally to NH3 emissions. This study emphasizes the need for coordinated efforts to control atmospheric NH3 pollution in Beijing City, with particular attention to addressing both vehicular and agricultural emissions.

Distinguishing Oceans of Water from Magma on Mini-Neptune K2-18b

Mildly irradiated mini-Neptunes have densities potentially consistent with them hosting substantial liquid-water oceans (“Hycean” planets). The presence of CO2 and simultaneous absence of ammonia (NH3) in their atmospheres has been proposed as a fingerprint of such worlds. JWST observations of K2-18b, the archetypal Hycean, have found the presence of CO2 and the depletion of NH3 to <100 ppm; hence, it has been inferred that this planet may host liquid-water oceans. In contrast, climate modeling suggests that many of these mini-Neptunes, including K2-18b, may likely be too hot to host liquid water. We propose a solution to this discrepancy between observation and climate modeling by investigating the effect of a magma ocean on the atmospheric chemistry of mini-Neptunes. We demonstrate that atmospheric NH3 depletion is a natural consequence of the high solubility of nitrogen species in magma at reducing conditions; precisely the conditions prevailing where a thick hydrogen envelope is in communication with a molten planetary surface. The magma ocean model reproduces the present JWST spectrum of K2-18b to ≲3σ, suggesting this is as credible an explanation for current observations as the planet hosting a liquid-water ocean. Spectral areas that could be used to rule out the magma ocean model include the >4 μm region, where CO2 and CO features dominate: magma ocean models suggest a systematically lower CO2/CO ratio than estimated from free-chemistry retrieval, indicating that deeper observations of this spectral region may be able to distinguish between oceans of liquid water and magma on mini-Neptunes.

Insights into national distribution of NH3 concentrations in Republic of Korea: findings from passive sampler observations and implications for sources and management.

Gas-phase NH3 is one of the significant contributors to secondary aerosol formation in the atmosphere, and it is a crucial consideration in any strategy aiming to reduce PM2.5 emissions. This study aimed to investigate the spatial distributions of NH3 in verity source areas in Republic of Korea using passive samplers. NH3 concentrations were observed at 45 locations over a period of approximately 35weeks, from June 2022 to February 2023. As a result, NH3 concentration was found to be more affected by local sources rather than long-distance influx from outside. The average concentration of NH3 observed in 7 source areas excluding the background area was all less than 20.91ppb, except for livestock sources. These results suggest that atmospheric NH3 concentrations are significantly influenced from livestock sources. In addition, in major cities, the need for NH3 management was confirmed to be more focused on emissions from automobiles and industrial complexes than emissions from livestock and farmland. Moreover, even for the same source, NH3 concentrations varied depending on the type of livestock species, breeding methods and scale, products produced, crops cultivated, and vehicle traffic volume. These findings indicate the importance of considering factors such as breeding methods and manure treatment practices in emission factors, and it is expected that the results can be used as basic data for NH3 emission estimation and management.

Atomic insights into the interaction of N2, CO2, NH3, NO, and NO2 gas molecules with Zn2(V, Nb, Ta)N3 ternary nitride monolayers.

The search for promising carrier blocking layer materials with high stability, including resistance to surface inhibition by environmental molecules that cause a drop in carrier mobility, is critical for the production of tandem solar cells. Based on density functional theory calculations, the reaction of atmospheric gases, including N2, CO2, NH3, NO, and NO2, with three promising Zn2(V, Nb, Ta)N3 monolayers is discovered. The results suggest the chemical adsorption of NH3 and physical adsorption of NO and NO2. In addition, the Zn2(V, Nb, Ta)N3 monolayers are characterized by a weak bonding with N2 and CO2. Charge redistribution is found at the interface between the monolayers and NH3, NO and NO2 molecules, leading to the formation of a local surface dipole that affects the functionality of the Zn2(V, Nb, Ta)N3 monolayers. The Zn2VN3 monolayer is less reactive with atmospheric gases and thus is the most promising for application in tandem solar cells. Notably, the revealed nontrivial behavior of the Zn2(V, Nb, Ta)N3 monolayers towards N-containing gases makes them promising for application in gas sensing. Specifically, the Zn2TaN3 monolayer is the most promising for application in molecular sensing due to its high reversibility and distinguished interaction with NH3, NO, and NO2 gases.

Anomalous increase in global atmospheric ammonia during COVID-19 lockdown: Need policies to curb agricultural emissions

The restrictions imposed on human activities during the COVID-19 lockdown (LD) period provided a new scenario to identify potential sources of atmospheric pollution. There are several studies that deal with changes in air quality around the world during LD, but very few on atmospheric ammonia (NH3). Therefore, we examine the changes in global NH3 during LD (April–May 2020) in comparison to the pre-lockdown (PreLD, April–May 2017–2019) and post-lockdown (PostLD, April–May 2021) periods, and assess the factors responsible for these changes. We observe an increase in NH3 during LD across the latitudes, with very high values in the western Europe, Eastern China (EC), the Indian subcontinent and the eastern United States of America (USA). However, a decline in NH3 is observed in some regions of South America (SA) and North America (NA). Similar changes in NH3 during LD are also observed in smaller spatial scales, as found in 3000 cities across the globe. The reduction of sulphur dioxide (SO2), nitrogen dioxide (NO2), nitric acid (HNO3), humidity and cloud cover as a result of restrictions on human activities, particularly in the western Europe and the USA, may have impeded the conversion of NH3 to particulates, which led to a higher NH3 there. Nevertheless, agricultural activities and livestock are the most prominent sources of atmospheric NH3, and were not under restriction during LD, show an enhancement in terms of the use of nitrogen fertilizer, crop production and area harvested, which also cause a rise in NH3 in these regions. Therefore, it is evident that the changes in meteorology and atmospheric composition, together with increased agricultural activities, led to the global increase in atmospheric NH3 during LD. That is, most pollutants show a decline during LD, but NH3 exhibits a rise due to its sources such as agricultural activities. Henceforth, environmental regulations, policies and advanced technologies are required in the agricultural sector, such as fertilizer deep placement using urea briquettes and restricted application of nitrogen fertilizers, to curb NH3 emissions.

GaN/rGO nanocomposite gas sensor for enhanced NH3 sensing performances at room temperature

In this work, we developed a high-performance NH3 sensor based on GaN/rGO nanocomposites via a low-cost solvothermal method and subsequent nitridation process. The morphological, structural, and chemical compositions were investigated to demonstrate that GaN and rGO were coupled together by interfacial modulation, and the GaN/rGO heterostructure chemical bonds are successfully formed. Gas-sensing performance test results show that the fabricated GaN/rGO (2.2 wt%) NH3 sensor exhibited a high response value (92%), fast response time (11 s), and low limit of detection (500 ppb) at room temperature. In addition, reproducibility, humidity, and long-term stability tests of the GaN/rGO sensor were also conducted in this work. The enhancement sensing mechanisms are attributed to the large specific surface area, the excellent conductivity of rGO, and resistance modulation effect of the heterojunction potential. Hence, the GaN/rGO gas sensor can be regarded as a promising sensing solution for atmospheric and exhaled NH3 detection at room temperature.

Severe photochemical pollution formation associated with strong HONO emissions from dew and guttation evaporation

The unknown daytime source of HONO has been extensively investigated due to unexplained atmospheric oxidation capacity and current modelling bias, especially during cold seasons. In this study, abrupt morning increases in atmospheric HONO at a rural site in the North China Plain (NCP) were observed almost on daily basis, which were closely linked to simultaneous rises in atmospheric water vapor content and NH3 concentrations. Dew and guttation water formation was frequently observed on wheat leaves, from which water samples were taken and chemically analyzed for the first time. Results confirmed that such natural processes likely governed the daily nighttime deposition and daytime release of HONO and NH3, which have not been considered in the numerous HONO budget studies investigating its large missing daytime source in the NCP. The dissolved HONO and NH3 in leaf surface water droplets reached 1.4 and 23 mg L−1 during the morning on average, resulting in averaged atmospheric HONO and NH3 increases of 0.89 ± 0.61 and 43.7 ± 29.3 ppb during morning hours, with relative increases of 186 ± 212 % and 233 ± 252 %, respectively. The high atmospheric oxidation capacity contained within HONO was stored in near surface liquid water (such as dew, guttation and soil surface water) during nighttime, which prevented its atmospheric dispersion after sunset and protected it from photodissociation during early morning hours. HONO was released in a blast during later hours with stronger solar radiation, which triggered and then accelerated daytime photochemistry through the rapid photolysis of HONO and subsequent OH production, especially under high RH conditions, forming severe secondary gaseous and particulate pollution. Results of this study demonstrate that global ecosystems might play significant roles in atmospheric photochemistry through nighttime dew formation and guttation processes.

Measurement report: Ammonia in Paris derived from ground-based open-path and satellite observations

Abstract. Ammonia (NH3) is an important air pollutant which, as a precursor of fine particulate matter, raises public health concerns. This study analyzes 2.5 years of NH3 observations derived from ground-based (miniDOAS; differential optical absorption spectroscopy) and satellite (IASI; Infrared Atmospheric Sounding Interferometer) remote sensing instruments to quantify, for the first time, temporal variabilities (from interannual to diurnal) in NH3 concentrations in Paris. The IASI and miniDOAS datasets are found to be in relatively good agreement (R&gt;0.70) when atmospheric NH3 concentrations are high and driven by regional agricultural activities. Over the investigated period (January 2020–June 2022), NH3 average concentrations in Paris measured by the miniDOAS and IASI are 2.23 µg m−3 and 7.10×1015 molec. cm−2, respectively, which are lower than or equivalent to those documented in other urban areas. The seasonal and monthly variabilities in NH3 concentrations in Paris are driven by sporadic agricultural emissions influenced by meteorological conditions, with NH3 concentrations in spring up to 2 times higher than in other seasons. The potential source contribution function (PSCF) reveals that the close (100–200 km) east and northeast regions of Paris constitute the most important potential emission source areas of NH3 in the megacity. Weekly cycles of NH3 derived from satellite and ground-based observations show different ammonia sources in Paris. In spring, agriculture has a major influence on ammonia concentrations, and, in the other seasons, multi-platform observations suggest that ammonia is also controlled by traffic-related emissions. In Paris, the diurnal cycle of NH3 concentrations is very similar to the one of NO2, with morning enhancements coincident with intensified road traffic. NH3 evening enhancements synchronous with rush hours are also monitored in winter and fall. NH3 concentrations measured during the weekends are consistently lower than NH3 concentrations measured during weekdays in summer and fall. This is further evidence of a significant traffic source of NH3 in Paris.

NH3 emissions from the human body in central Tokyo decreased during the COVID-19 pandemic lockdown

Atmospheric NH3 is emitted from various sources, such as agriculture, automobile exhaust, industrial activities, and human bodies (dermal and respiratory). Although the contribution from automobile exhaust to NH3 concentrations in urban areas is well understood, the contribution from human body emissions has not been clarified, even in densely populated areas far from agricultural and industrial sources. Tokyo, Japan, is the one of the most populated megacities in the world. During April and May 2020, socioeconomic activities in Tokyo were severely restricted to prevent the spread of the coronavirus disease (COVID-19), resulting in significant changes in human flow and automobile traffic. The sudden decrease in emissions presented a unique opportunity to clarify the contributions of human body emissions to NH3 levels. NH3 concentrations observed in central Tokyo from 2018 to 2021 decreased significantly, by about 20%, during the lockdown in 2020. No significant differences were found in wind speed or rainfall during the same period. Air quality model simulations of NH3 concentrations in the area were performed for 2019 and 2020. The simulation results for 2019 reproduced the observed NH3 concentrations and temporal variations well. However, the simulation results were overestimated for 2020. To evaluate the differences in emissions' contributions during the lockdown, sensitivity tests of NH3 emissions’ strength were conducted for 2020. The simulation in which NH3 emissions from automobiles and human bodies were reduced by 20% and 80%, respectively, reproduced the observed results well. These results indicate that emissions from human bodies and automobile traffic contribute significantly to NH3 concentrations in central Tokyo. The contributions from human body emissions to NH3 concentrations revealed in this study should be applied to update emissions factors for human bodies; clarifying human emissions factors under various conditions will improve the accuracy of air quality simulations over densely populated megacities.

Characteristics and sources of atmospheric ammonia at the SORPES station in the western Yangtze river delta of China

Ammonia (NH3) is an important air pollutant with crucial impacts on air quality, ecosystems and climate change. However, NH3 is not included in routine air quality monitoring and the availability of long-term NH3 measurements is still limited, resulting in large uncertainties in our knowledge of the spatial distribution and sources of NH3. Here we performed 1 year (March 2021–February 2022) of atmospheric NH3 measurements at a regional background station, the Station for Observing Regional Processes of the Earth System (SORPES) in the western Yangtze River Delta of China. We found that the annual mean NH3 concentration was 12.2 ± 4.6 ppb and exhibited apparent seasonal variations, with a maximum in June and a minimum in February, influenced by agricultural activities, air temperature, gas-particle partitioning and precipitation. Moreover, air temperature and absolute humidity correlated well with NH3, indicating that they are important factors in influencing NH3 levels. The diurnal variation of NH3 showed a single peak in the morning and higher concentrations during the day. In spring and autumn, the NH3 morning peak can be attributed to dew evaporation. The air mass backward trajectory, local wind direction and velocity analysis suggested that NH3 was influenced by both local emissions and regional transport from nearby cities. During the COVID-19 lockdown, a strong reduction of NOx (−77%) and a weak reduction of NH3 (−14%) were observed compared to the pre-lockdown, highlighting that traffic emissions have a minor impact on NH3 at the SORPES station. Our results provide more insights into the characteristics and sources of atmospheric NH3 in background regions influenced by mixed air pollution plumes.

Biomonitoring of dairy farm emitted ammonia in surface waters using phytoplankton and periphyton

The increasing environmental abundance of reactive N (‘Nr’) entails many adverse effects for society such as soil degradation and eutrophication. In addressing the global surplus of N, there is a pressing need to quantify local sources and dynamics of Nr. Although quantified as an important anthropogenic source of Nr, the spatiotemporal patterns of ammonia (‘NH3’) emitted by dairy farming and its resulting pressure on local surface waters lacks quantification. Quantification could optimize farm management with minimized losses of valuable nitrogen and protection of freshwater ecology. This study aimed to unravel spatiotemporal dynamics of ammonia nitrogen emitted by a dairy farm in the atmospheric and aquatic geo-ecosphere. Atmospheric NH3 and aqueous ammonium (‘NH4+’) were determined over time, together with meteorological variables. Aquatic biomonitors (periphyton and phytoplankton) were employed to monitor the spatial impacts of cattle-stable emitted NH3. Atmospheric NH3 on the farm was significantly regulated by wind, sharply declining over increasing distances from the stable (average decrease in the dominant wind direction from 55.5 μg/m3 at 20 m to 5.8 μg/m3 at 500 m, in the other wind directions values decreased from 38.3 μg/m3 to 6.0 μg/m3). This was also reflected in local surface water concentrations of NH4+, with average concentrations decreasing from 37.0 mg [NH4+-N]/L at 65 m to 4.8 mg [NH4+-N]/L in the dominant wind direction, and from 1.2 to 0.7 in other directions. Periphyton biomass, total N (“TN”) and δ15N all significantly reflected spatiotemporal dynamics of atmospheric NH3 and aqueous NH4+, as did phytoplankton TN. The cattle stable significantly influenced local water quality through atmospheric spreading of NH3, and both aquatic biomonitors were influenced by and reflected dairy farm emitted NH3 with a sharp dilution over distance. This study strongly underlines the importance of atmospheric transport of dairy farm emitted NH3 and its effects on local water quality.

Development of a CFD model to simulate the dispersion of atmospheric NH3 in a semi-open barn

The dispersion of atmospheric NH3 constitutes the most common passive polluting system in cattle stables. Although the studies carried out through computational fluid dynamics (CFD) are focused on improving the environmental conditions in situ to increase the productivity of stables, they do not refer to determining the environmental impact of NH3 emissions into the atmosphere. This work evaluated the distribution of the NH3 flux inside a barn using CFD and its relationship with environmental conditions through probabilistic analysis by the K2 algorithm. The initial data on environmental conditions were wind speed and direction, maximum temperature, and humidity from the nearest weather station in a region characterized by hot weather conditions during summer. The vertical trajectory was used to analyze the impact of long-range transport on the spatial distribution, where 75% is between 0 and 5 m in height, and 25% is between 10 and 20 m outside the eaves. The work concluded that temperature is the main parameter of influence.

Traceability of atmospheric ammonia in a suburban area of the Beijing-Tianjin-Hebei region

Ammonia (NH3) is one of the most important sources that have been linked to the formation of PM2.5. Therefore, it is important to study the source contributions to atmospheric NH3 for air pollution control. Here we used 15N natural abundance (expressed by δ15N) values to quantify the source contributions to atmospheric NH3 in the Beijing-Tianjin-Hebei (BTH) region, which suffers from the country's worst air pollution. Results showed that from 2017 to 2019, the annual mean δ15N-NH3 value at the livestock site (−27.5 ± 6.0 ‰) was lower than at cropland (−20.7 ± 6.0 ‰) and rural residential sites (−22.1 ± 7.4 ‰), while their concentrations were the opposite. Seasonal mean δ15N-NH3 values were the highest in winter and lowest in summer, whereas monthly mean δ15N-NH3 values were the highest in January and lowest in June. The isotope mixing model results showed that agricultural sources account for 64.5 ± 13.5 % of year-round total NH3 emissions, while industrial and other sources contributed 27.4 and 8.1 %, respectively. However, the contribution of industrial sources was higher than that of agricultural sources in January. Our results indicated that the contribution of agricultural sources has decreased after the implementation of air pollution control policies in this region suggesting that NH3 abatement from agricultural sources is effective. However, further refinement of agricultural emission abatement measures will be required, accompanied by a greater focus on controlling winter non-agricultural sources.