PM2.5 pollution is substantially affected by ammonia emissions in China

Association between ambient fine particular matter components and subsequent cognitive impairment in community-dwelling older people: a prospective cohort study from eastern China

BACKGROUND

Fine particular matter (PM2.5) has been associated with dementia, but limited information is available regarding the association between PM2.5 components and dementia.

AIMS

We aimed to identify the major components of PM2.5 that affect cognitive function to further investigate its mechanism of action, and develop a prevention strategy for dementia.

METHODS

In this study, we included 7804 participants aged ≥ 60 years recruited from seven counties in Zhejiang province, eastern China. The participants completed the baseline survey between 2014 and 2015, and were followed up until the end of 2020. We adopted single-component robust Poisson regression models for analyses, and estimated relative risks and 95% confidence intervals describing associations between the chemical constituents of PM2.5 exposure and incident cognitive impairment in those who were free from cognitive impairment at baseline.

RESULTS

Significantly positive associations were observed between sulfate, nitrate, ammonium, and organic matter in PM2.5 and incident cognitive impairment across different exposure periods; the relative risks of 10-year exposure before enrollment ranged from 1.01 to 1.02. However, we did not find a significant association between black carbon and cognitive impairment. The point estimates of the relative risk values did not change substantially after performing the sensitivity analyses.

CONCLUSIONS

Our findings strengthen the idea that long-term exposure to PM2.5 mass and its chemical components is associated with an elevated risk of incident cognitive impairment among older adults.

The Development of the Regenerable Catalytic System in Selective Catalytic Oxidation of Ammonia with High N2 Selectivity

Supported particulate noble-metal catalysts are widely used in industrial catalytic reactions. However, these metal species, whether in the form of nanoparticles or highly dispersed entities, tend to aggregate during reactions, leading to a reduced activity or selectivity. Addressing the frequent necessity for the replacement of industrial catalysts remains a significant challenge. Herein, we demonstrate the feasibility of the 'regenerable catalytic system' exemplified by selective catalytic oxidation of ammonia (NH3-SCO) employing Ag/Al2O3 catalysts. Results demonstrate that our highly dispersed Ag catalyst (Ag HD) maintains >90% N2 selectivity at 80% NH3 conversion and >80% N2 selectivity at 100% NH3 conversion after enduring 5 cycles of reducible aggregation and oxidative dispersion. Moreover, it consistently upholds over 98% N2 selectivity at 100% NH3 conversion after 10 cycles of Ar treatment. During the aggregation-dispersion process, the Ag HD catalyst intentionally aggregated into Ag nanoparticles (Ag NP) after H2 reduction and exhibited remarkable regenerable capabilities, returning to the Ag HD state after calcination in the air. This structural evolution was characterized through in situ transmission electron microscopy, atomically resolved high-angle annular dark-field scanning transmission electron microscopy, and X-ray absorption spectroscopy, revealing the on-site oxidative dispersion of Ag NP. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy provided insights into the exceptional N2 selectivity on Ag HD catalysts, elucidating the critical role of NO+ intermediates. Our findings suggest a sustainable and cost-effective solution for various industry applications.

Implementation of a GEOAI model to assess the impact of agricultural land on the spatial distribution of PM2.5 concentration

Air pollution is considered one of the major environmental risks to health worldwide. Researchers are making significant efforts to study it, thanks to state-of-art technologies in data collection and processing, and to mitigate its effect. In this context, while a lot is known about the role of urbanization, industries, and transport, the impact of agricultural activities on the spatial distribution of pollution is less studied, despite knowledge about emissions suggest it is not a secondary factor. Therefore, the aim of this study was to assess this impact, and to compare it with that of traditional polluting sources, harvesting the capabilities of GEOAI (Geomatics and Earth Observation Artificial Intelligence). The analysis targeted the highly polluted territory of Lombardy, Italy, considering fine particulate matter (PM2.5). PM2.5 data were obtained from the Copernicus-Atmosphere-Monitoring-Service and processed to infer time-invariant spatial parameters (frequency, intensity and exposure) of concentration across the whole period. An ensemble architecture was implemented, with three blocks: correlation-based features selection, Multiscale-Geographically-Weighted-Regression for spatial enhancement, and a final random forest classifier. Finally, the SHapley Additive exPlanation algorithm was applied to compute the relevance of the different land-use classes on the model. The impact of land-use classes was found significantly higher compared to other published models, showing that the insignificant correlations found in the literature are probably due to an unfit experimental setup. The impact of agricultural activities on the spatial distribution of PM2.5 concentration was comparable to the other considered sources, even when focusing only on the most densely inhabited urban areas. In particular, the agriculture's contribution resulted in pollution spikes rather than in a baseline increase. These results allow to state that public policymakers should consider also agricultural activities for evidence-based decision-making about pollution mitigation.

In situ biomass burning enhanced the contribution of biogenic sources to sulfate aerosol in subtropical cities

Sulfurous gases released by biogenic sources play a key role in the global sulfur cycle. However, the contribution of biogenic sources to sulfate aerosol in the urban atmosphere has received little attention. Emission sources and formation process of sulfate in Guangzhou, a subtropical mega-city in China, were clarified using multiple methods, including isotope tracers and chemical markers. The δ18O of sulfate suggested that secondary sulfate was the dominant component (84 %) of sulfate aerosol, which mainly formed by transition metal ion (TMI) catalyzed oxidation (31 %) and OH radical oxidation (30 %). The factors driving secondary sulfate formation were revealed using a tree boosting model, which suggested that NH3, temperature, and oxidants were the most important factors. The δ34S of sulfate indicated that biogenic sources accounted for annual average of 26.0 % of the sulfate, which increased to 30.4 % in winter monsoon period. Rice straw burning enhanced sulfate formation by promoting the release of reduced sulfur from soil, which is rapidly converted into sulfate under a subtropical urban atmosphere with high concentration of NH3 and oxidants. This study revealed the important influence of rice straw burning on biogenic sulfur emission during the rice harvest, thereby providing insight into the sulfur cycle and regional air pollution.

Roles of historical land use/cover and nitrogen fertilizer application changes on ammonia emissions in farmland ecosystem from 1990 to 2020 in China

In the past decades, China has witnessed significant changes in its land use/land cover (LULC) pattern. These changes have led to a direct impact on ammonia (NH3) emissions in soil background, and indirectly affected the total nitrogen fertilizer (N-fertilizer) application, crop planting amount and the resulting straw mass through the changes of cropland area. Great changes have also taken place in the amount and structure of fertilizer application in China, which affects the NH3 emissions from farmland ecosystems caused by N-fertilizer application. The aforementioned changes have led to significant alterations in NH3 emissions from China's farmland ecosystems over the past 30 years. The process of these changes remains to be analyzed, and the contributions of LULC changes and N-fertilizer application in this process are yet to be assessed. This study aims to investigate the NH3 emission changes and spatiotemporal variation characteristics from farmland ecosystems during 1990 and 2020 due to the LULC changes. Additionally, the study employs scenario analysis method to discuss the effects of LULC changes and N-fertilizer application changes on NH3 emissions in farmland ecosystems. Results indicate that there is evident spatiotemporal heterogeneity in China's LULC pattern, particularly in eastern China. The southeast region is predominantly characterized by the conversion of cropland into construction land. Moreover, some regions such as Northwest China and Northeast China have experienced the conversion of other land types into cropland, significantly influenced by national development policies. From 1990 to 2020, the national NH3 emissions from farmland ecosystem range from 3294.75 Gg to 4064.20 Gg. NH3 emissions and their interannual variation in farmland ecosystems exhibit significant differences across various regions. The regions with higher contributions to NH3 emissions in farmland ecosystems are East China, Central China, and North China, accounting for 25.32 %-37.26 %, 18.85 %-22.46 % and 11.24 %-18.50 % of the total emissions, respectively. NH3 emissions in each region are influenced by cropland area, N-fertilizer application, and regional development characteristics. Compared to LULC changes, changes in N-fertilizer application have a more pronounced impact on NH3 emission changes in farmland ecosystems. From 1990 to 2020, the contribution (increase or decrease) of N-fertilizer application changes to NH3 emission changes in farmland ecosystems in China ranges from 0.11 % to 16.61 %, while the contribution (increase or decrease) of LULC changes ranges from 0.47 % to 2.38 %. South China demonstrates a unique situation regarding the influence of LULC changes. This region has a relatively small cropland area, and fluctuations in cropland area significantly affect NH3 emissions in farmland ecosystems. The influence of policies is evident. From the changes in cropland area in Northwest China and Northeast China to changes in N-fertilizer application, policy changes have consistently impacted the changes in NH3 emissions in China's farmland ecosystems. From "soft policies" involving encouragement and guidance to "hard policies" encompassing the establishment of necessary targets, the degree of strictness in policy directly affects the timeliness of policies effectiveness. The results of this study indicate that reducing the application of N-fertilizers is the primary approach to reducing NH3 emissions in China's farmland ecosystems. In terms of policy guidance, compared to implementing structural and pathway adjustments, implementing clear total control of fertilizer usage is a timely and effective choice for reducing NH3 emissions.

Establishing an emission inventory for ammonia, a key driver of haze formation in the southern North China plain during the COVID-19 pandemic

Despite the significant reduction in atmospheric pollutant levels during the COVID-19 lockdown, the presence of haze in the North China Plain remained a frequent occurrence owing to the enhanced formation of secondary inorganic aerosols under ammonia-rich conditions. Quantifying the increase or decrease in atmospheric ammonia (NH3) emissions is a key step in exploring the causes of the COVID-19 haze. Historic activity levels of anthropogenic NH3 emissions were collected through various yearbooks and studies, an anthropogenic NH3 emission inventory for Henan Province for 2020 was established, and the variations in NH3 emissions from different sources between COVID-19 and non-COVID-19 years were investigated. The validity of the NH3 emission inventory was further evaluated through comparison with previous studies and uncertainty analysis from Monte Carlo simulations. Results showed that the total NH3 emissions gradually increased from north-west to south-east, totalling 751.80 kt in 2020. Compared to the non-COVID-19 year of 2019, the total NH3 emissions were reduced by approximately 4 %, with traffic sources, waste disposal and biomass burning serving as the sources with the top three largest reductions, approximately 33 %, 9.97 % and 6.19 %, respectively. Emissions from humans and fuel combustion slightly increased. Meanwhile, livestock waste emissions decreased by only 3.72 %, and other agricultural emissions experienced insignificant change. Non-agricultural sources were more severely influenced by the COVID-19 lockdown than agricultural sources; nevertheless, agricultural activities contributed 84.35 % of the total NH3 emissions in 2020. These results show that haze treatment should be focused on reducing NH3, particularly controlling agricultural NH3 emissions.

Summertime Urban Ammonia Emissions May Be Substantially Underestimated in Beijing, China

Ammonia (NH3) is critical to the nitrogen cycle and PM2.5 formation, yet a great deal of uncertainty exists in its urban emission quantifications. Model-underestimated NH3 concentrations have been reported for cities, yet few studies have provided an explanation. Here, we explore reasons for severe WRF-Chem model underestimations of NH3 concentrations in Beijing in August 2018, including simulated gas-particle partitioning, meteorology, regional transport, and emissions, using spatially refined (3 km resolution) NH3 emission estimates in the agricultural sector for Beijing-Tianjin-Hebei and in the traffic sector for Beijing. We find that simulated NH3 concentrations are significantly lower than ground-based and satellite observations during August in Beijing, while wintertime underestimations are much more moderate. Further analyses and sensitivity experiments show that such discrepancies cannot be attributed to factors other than biases in NH3 emissions. Using site measurements as constraints, we estimate that both agricultural and non-agricultural NH3 emission totals in Beijing shall increase by ∼5 times to match the observations. Future research should be performed to allocate underestimations to urban fertilizer, power, traffic, or residential sources. Dense and regular urban NH3 observations are necessary to constrain and validate bottom-up inventories and NHx simulation.

Subsurface fertilization boosts crop yields and lowers greenhouse gas emissions: A global meta-analysis

The subsurface application (SA) of nitrogenous fertilizers is a potential solution to mitigate climate change and improve food security. However, the impacts of SA technology on greenhouse gas (GHG) emissions and agronomic yield are usually evaluated separately and their results are inconsistent. To address this gap, we conducted a meta-analysis synthesizing 40 peer-reviewed studies on the effects of SA technology on GHG and ammonia (NH₃) emissions, nitrogen uptake (NU), crop yield, and soil residual NO₃-N in rice paddies and upland cropping system. Compared to the surface application of N, SA technology significantly increased rice yields by 32 % and crop yield in upland systems by 62 %. The largest SA-induced increases in crop yield were found at low N input rates (<100 kg Nha^-1) in rice paddies and medium N input rates (100-200 kg Nha^-1) in upland systems, suggesting that soil moisture is a key factor determining the efficiency of SA technology. SA treatments increased yields by more at reduced fertilizer rates (~30 % less N), a shallow depth (<10 cm), and with urea in both cropping systems than at the full (recommended) N rate, a deeper depth (10-20 cm), and with ammonical fertilizer. SA treatments significantly increased NU in rice paddies (34 %) and upland systems (18 %), and NO₃-N (40 %) in paddyland; however, NO₃-N decreased (28 %) in upland conditions. Ammonia mitigation was greater in paddyland than in upland conditions. SA technology decreased the carbon footprint (CF) in paddyland by 29 % and upland systems by 36 %, and overall by 33 %. Compared with broadcasting, SA significantly reduced CH₄ emissions by 16 %, N₂O emissions by 30 %, and global warming potential (GWP) by 10 % in paddy cultivation. Given SA increased grain yield and NU while reducing NH₃, CF, and GWP, this practice provides dual benefits - mitigating climate change and ensuring food security.

Distribution, source identification and ecological effects of aerosol dissolved nutrients in the Bohai Bay

The atmospheric aerosols around the Bohai Bay are affected intensively by the surrounding industrial, shipping and other human activities. Although atmospheric dry deposition is an important way for nutrients to enter the Bohai Bay, few studies explore the distribution patterns, source and deposition fluxes of typical nutrients in aerosols and their impacts on the marine ecosystem. This paper explored the spatial-temporal distribution of typical aerosol nutrients in summer and autumn, and their source and ecological effects were illustrated further. The mean concentration of dissolved total phosphorus (DTP), dissolved total nitrogen (DTN), dissolved organic nitrogen (DON), dissolved inorganic nitrogen (DIN), ammonium (NH₄-N), nitrate (NO₃-N), nitrite (NO₂-N), silicate (SiO₃-Si), phosphate (PO₄-P), and dissolved organic phosphorus (DOP) were 31.22, 847.22, 288.19, 559.77, 288.19, 304.00, 253.65, 2.12, 15.74 and 15.48 nmol/m³, respectively, while their fluxes were corresponding to 0.61, 8.36, 2.52, 4.90, 1.41, 2.49, 0.02, 0.04, 0.19 and 0.26 mmol/(m² month). Typical aerosol nutrient concentrations in autumn were mostly higher than those in summer, with high values occurring mainly in the central region. The potential sources of pollution were mainly concentrated in Shandong and Mongolia, and the sources of pollution were mainly agriculture, dust and industry. The large N:P and N:Si ratios in the dry deposition likely exacerbated Si and P limitation in the water column. These results provided the data basis for evaluating the pollution status and revealed that the dry deposition of aerosol nutrients should not be neglected by the ecological environment in the Bohai Bay.

Life cycle assessment and techno-economic analysis of nitrogen recovery by ammonia air-stripping from wastewater treatment

Wastewater treatment plants (WWTPs) with anaerobic digestion of biosolids produce an ammonia-rich sidestream out of which nitrogen can be recovered through air stripping. Recovered ammonia can be used to produce ammonium sulfate (AS) for agricultural use, enabling the circular return of nitrogen as fertilizer to the food system. We investigate the cost and life cycle environmental impact of recovering ammonia from the sidestream of WWTPs for conversion to AS and compare it to AS production from the Haber Bosch process. We perform life cycle assessment (LCA) to investigate the environmental impact of AS fertilizer production by air-stripping ammonia from WWTP sidestreams at varying sidestream nitrogen concentrations. Techno-economic analysis (TEA) is performed to assess the break-even selling price of sidestream AS production at a WWTP in the City of Philadelphia. Greenhouse gas emissions for air-stripping technology range between 0.2 and 0.5 kg CO₂e/kg AS, about six times lower than the hydrocarbon-based Haber-Bosch process, estimated at 2.5 kg CO₂e/kg AS. Further reduction of greenhouse gas emissions is feasible by replacing fossil-based energy use in air-stripping process (82-98 % of net energy demand) with renewable sources. Also, a significant reduction in mineral depletion and improvement in human and ecosystem health are observed for the air-stripping approach. Furthermore, the break-even selling price for installing sidestream-based AS production at the Philadelphia's WWTP, considering capital and operating costs, is estimated at $0.046/kg AS (100 %), which is 92 % lower than the 2014 estimate of AS's average selling price at farms in the United States. We conclude that even with varying ammonia concentrations and high sidestream volume, air-stripping technology offers an environmentally and economically favorable option for implementing nitrogen recovery and simultaneous production of AS at WWTPs.

A Source Apportionment and Emission Scenario Assessment of PM2.5- and O3-Related Health Impacts in G20 Countries

Exposure to air pollution is a leading risk factor for premature death globally; however, the complexity of its formation and the diversity of its sources can make it difficult to address. The Group of Twenty (G20) countries are a collection of the world's largest and most influential economies and are uniquely poised to take action to reduce the global health burden associated with air pollution. We present a framework capable of simultaneously identifying regional and sectoral sources of the health impacts associated with two air pollutants, fine particulate matter (PM_2.5) and ozone (O₃) in G20 countries; this framework is also used to assess the health impacts associated with emission reductions. This approach combines GEOS-Chem adjoint sensitivities, satellite-derived data, and a new framework designed to better characterize the non-linear relationship between O₃ exposures and nitrogen oxides emissions. From this approach, we estimate that a 50% reduction of land transportation emissions by 2040 would result in 251 thousand premature deaths avoided in G20 countries. These premature deaths would be attributable equally to reductions in PM_2.5 and O₃ exposure which make up 51% and 49% of the potential benefits, respectively. In our second application, we estimate that the energy generation related co-benefits associated with G20 countries staying on pace with their net-zero carbon dioxide targets would be 290 thousand premature deaths avoided in 2040; action by India (47%) would result in the most benefits of any country and a majority of these avoided deaths would be attributable to reductions in PM_2.5 exposure (68%).

Isotopic imprints of aerosol ammonium over the north China plain

Atmospheric PM_2.5 poses a variety of health and environmental risks to urban environments. Ammonium is one of the main components of PM_2.5, and its role in PM_2.5 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 PM_2.5 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 PM_2.5. 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.

Multi-Scale Effects of Meteorological Conditions and Anthropogenic Emissions on PM2.5 Concentrations over Major Cities of the Yellow River Basin

The mechanism behind PM2.5 pollution is complex, and its performance at multi-scales is still unclear. Based on PM2.5 monitoring data collected from 2015 to 2021, we used the GeoDetector model to assess the multi-scale effects of meteorological conditions and anthropogenic emissions, as well as their interactions with PM2.5 concentrations in major cities in the Yellow River Basin (YRB). Our study confirms that PM2.5 concentrations in the YRB from 2015 to 2021 show an inter-annual and inter-season decreasing trend and that PM2.5 concentrations varied more significantly in winter. The inter-month variation of PM2.5 concentrations shows a sinusoidal pattern from 2015 to 2021, with the highest concentrations in January and December and the lowest from June to August. The PM2.5 concentrations for major cities in the middle and downstream regions of the YRB are higher than in the upper areas, with high spatial distribution in the east and low spatial distribution in the west. Anthropogenic emissions and meteorological conditions have similar inter-annual effects, while air pressure and temperature are the two main drivers across the whole basin. At the sub-basin scale, meteorological conditions have stronger inter-annual effects on PM2.5 concentrations, of which temperature is the dominant impact factor. Wind speed has a significant effect on PM2.5 concentrations across the four seasons in the downstream region and has the strongest effect in winter. Primary PM2.5 and ammonia are the two main emission factors. Interactions between the factors significantly enhanced the PM2.5 concentrations. The interaction between ammonia and other emissions plays a dominant role at the whole and sub-basin scales in summer, while the interaction between meteorological factors plays a dominant role at the whole-basin scale in winter. Our study not only provides cases and references for the development of PM2.5 pollution prevention and control policies in YRB but can also shed light on similar regions in China as well as in other regions of the world.

Assessment of long-term particulate nitrate air pollution and its health risk in China

Air pollution is a major environmental and public health challenge in China and the Chinese government has implemented a series of strict air quality policies. However, particulate nitrate (NO₃⁻) concentration remains high or even increases at monitoring sites despite the total PM_2.5 concentration has decreased. Unfortunately, it has been difficult to estimate NO₃⁻ concentration across China due to the lack of a PM_2.5 speciation monitoring network. Here, we use a machine learning model incorporating ground measurements and satellite data to characterize the spatiotemporal patterns of NO₃⁻, thereby understanding the disease burden associated with long-term NO₃⁻ exposure in China. Our results show that existing air pollution control policies are effective, but increased NO₃⁻ of traffic emissions offset reduced NO₃⁻ of industrial emissions. In 2018, the national mean mortality burden attributable to NO₃⁻ was as high as 0.68 million, indicating that targeted regulations are needed to control NO₃⁻ pollution in China.

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We build a NO₃⁻ model using machine learning techniques incorporating satellite data

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We estimate spatiotemporal variations of NO₃⁻ concentration in China from 2005–2018

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In 2018, the national mean mortality burden attributable to NO₃⁻ was about 0.68 million

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Targeted regulations on vehicle emissions are needed to control NO₃⁻ pollution in China

Impact of NH3 Emissions on Particulate Matter Pollution in South Korea: A Case Study of the Seoul Metropolitan Area

We analyzed the multi-year relationship between particulate matter (PM10 and PM2.5) concentrations and possible precursors including NO2, SO2, and NH3 based on local observations over the Seoul Metropolitan Area (SMA) from 2015 to 2017. Surface NH3 concentrations were obtained from Cross-track Infrared Sounder (CrIS) retrievals, while other pollutants were observed at 142 ground sites. We found that NH3 had the highest correlation with PM2.5 (R = 0.51) compared to other precursors such as NO2 and SO2 (R of 0.16 and 0.14, respectively). The correlations indicate that NH3 emissions are likely a limiting factor in controlling PM2.5 over the SMA in a high-NOx environment. This implies that the current Korean policy urgently requires tools for controlling local NH3 emissions from the livestock industry (for example, from hog manure). These findings provide the first satellite-based trace gas evidence that implementing an NH3 control strategy could play a key role in improving air quality in the SMA.

Ammonia Emissions from Croplands Decrease with Farm Size in China

Farm size affects nitrogen fertilizer input and agricultural practices, which are key determinants of ammonia (NH₃) emissions from croplands. However, the degree to which NH₃ emissions are associated with changes in farm size is not well understood yet despite its crucial role in achieving agricultural sustainability in China, where agricultural production is still dominated by smallholder farms. Here we provide a first analysis of the relationship between farm size and NH₃ emissions based on 863 000 surveys conducted in 2017 across China. Results show that NH₃ emissions (kg ha^-1) on average decrease by 0.07% for each 1% increase in average farm size. This change occurs mainly due to a reduction in nitrogen fertilizer use and the introduction of more efficient fertilization practices. The largest reduction in NH₃ emissions is found in maize, with less pronounced changes in rice cultivation, and none for wheat production. Overall lower NH₃ emissions factors can be observed in the north of China with increasing farm size, especially in the northeast, the opposite pattern was found in the south. National total NH₃ emissions could be approximately halved (1.5 Tg) in a scenario favoring a conversion to large-scale farming systems. This substantial reduction potential highlights the potential of such a transition to reduce NH₃ emissions, including benefits from a socioeconomic point of view as well as for improving air quality.

Assessing the Relationship among Land Transfer, Fertilizer Usage, and PM2.5 Pollution: Evidence from Rural China

Concern for environmental issues is a crucial component in achieving the goal of sustainable development of humankind. Different countries face various challenges and difficulties in this process, which require unique solutions. This study investigated the relationship between land transfer, fertilizer usage, and PM_2.5 pollution in rural China from 2000 to 2019, considering their essential roles in agricultural development and overall national welfare. A cross section dependence test, unit root test, and cointegration test, among other methods, were used to test the panel data. A Granger causality test was used to determine the causal relationship between variables, and an empirical analysis of the impulse response and variance decomposition was carried out. The results show that the use of chemical fertilizers had a significant positive impact on PM_2.5 pollution, but the impact of land transfer on PM_2.5 pollution was negative. In addition, land transfer can reduce the use of chemical fertilizers through economies of scale, thus reducing air pollution. More specifically, for every 1% increase in fertilizer usage, PM_2.5 increased by 0.17%, and for every 1% increase in land transfer rate, PM_2.5 decreased by about 0.07%. The study on the causal relationship between land transfer, fertilizer usage, and PM_2.5 pollution in this paper is helpful for exploring environmental change—they are supplements and innovations which are based on previous studies and provide policy-makers with a basis and inspiration for decision-making.

Ambient observations indicating an increasing effectiveness of ammonia control in wintertime PM2.5 reduction in Central China

Ammonia emission reduction is increasingly being considered one of the control measures to mitigate wintertime fine particulate matter (PM_2.5) pollution. Three wintertime observations from 2012 to 2018 in Wuhan, China, were analyzed to examine the effectiveness of ammonia control in wintertime PM_2.5 reduction based on the critical total ammonia concentration (CTAC, i.e., the inflection point of effective ammonia control for PM_2.5 mass reduction based on the asymmetric response of PM_2.5 to ammonia control). The CTAC gradually approached 0% (immediate effectiveness), with values of -26% in 2012, -23% in 2015, and -9% in 2018. At the observed ambient conditions, there were significant positive correlations of the CTAC with sulfate and total nitrate changes, in contrast to the negative correlation of the CTAC with total ammonia change. An approximately 10% total ammonia reduction could offset the decline in CTAC attributed to a 30-40% sulfate or 20-30% total nitrate reduction in Wuhan. This study indicates that the combined control of SO₂ + NO_x (NO+NO₂) remains the preferred way to reduce inorganic particles in Central China at present, despite a tendency of the ambient chemical state moving towards effective ammonia control. However, as the CTAC approaches 0%, the effectiveness of ammonia and NO_x reduction measures targeting wintertime PM_2.5 can greatly exceed that observed during the 2012-2018 period in Central China.

Particulate Matter and Ammonia Pollution in the Animal Agricultural-Producing Regions of North Carolina: Integrated Ground-Based Measurements and Satellite Analysis

Intensive animal agriculture is an important part of the US and North Carolina’s (NC’s) economy. Large emissions of ammonia (NH3) gas emanate from the handling of animal wastes at these operations contributing to the formation of fine particulate matter (PM2.5) around the state causing a variety of human health and environmental effects. The objective of this research is to provide the relationship between ammonia, aerosol optical depth and meteorology and its effect on PM2.5 concentrations using satellite observations (column ammonia and aerosol optical depth (AOD)) and ground-based meteorological observations. An observational-based multiple linear regression model was derived to predict ground-level PM2.5 during the summer months (JJA) from 2008–2017 in New Hanover County, Catawba County and Sampson County. A combination of the Cumberland and Johnston County models for the summer was chosen and validated for Duplin County, NC, then used to predict Sampson County, NC, PM2.5 concentrations. The model predicted a total of six 24 h exceedances over the nine-year period. This indicates that there are rural areas of the state that may have air quality issues that are not captured for a lack of measurements. Moreover, PM2.5 chemical composition analysis suggests that ammonium is a major component of the PM2.5 aerosol.

Synergistic effect of reductions in multiple gaseous precursors on secondary inorganic aerosols in winter under a meteorology-based redistributed daily NH3 emission inventory within the Beijing-Tianjin-Hebei region, China

Secondary inorganic aerosols (SIA) account for 20-60% of the total fine particulates in the Beijing-Tianjin-Hebei (BTH) region of China, indicating an urgent need to clarify the relationship among such compounds. The purpose of this study was to quantify the relationship between emissions of NH₃, NOx, SO₂, VOCs and SIA concentrations during a severe winter haze episode using an air quality model and a meteorology-based redistributed NH₃ emission inventory within the BTH region. The results showed that the model performance regarding the NH₃ simulations in January by the four emission inventories improved after the redistribution of daily NH₃ emissions, with an increase of 0.02-0.13 in R, a 9-56% decrease in NMB, and a 7-51% decrease in NME. The updated simulations reproduced the daily observations of SIA, SO₂, and NO₂ well. A total of 125 sets of sensitivity simulations showed that a synergistic reduction in NH₃ and VOCs was more efficient in terms of SIA control than simply reducing SO₂ or NOx in the BTH region. If only NOx emissions were reduced, the SIA concentration would first increase and then decrease, and it could decline by another 0.86-8.03% in parallel with an equal NH₃ emission cut. SIA could be reduced by approximately 22.68% with the most stringent inorganic precursors' control. Moreover, VOCs emission reductions could lead to a decrease in SIA, and the impact of VOCs on SIA was similar to that of NH₃. The collaborative control of both inorganic precursors and VOCs was more effective than single-factor control measures for decreasing SIA, and the decline rate was approximately 29.26% under minimum emission conditions. This improved effectiveness was obtained because VOCs mitigation effectively decreases the ozone concentration, which in turn influences SIA formation. Finally, on the premise of a 60% SO₂ cut, the reduction scheme NH₃:VOCs:NOx = 4:4:1 was suggested for SIA control.

Protonated acetone ion chemical ionization time-of-flight mass spectrometry for real-time measurement of atmospheric ammonia

Ammonia (NH₃) is ubiquitous in the atmosphere, it can affect the formation of secondary aerosols and particulate matter, and cause soil eutrophication through sedimentation. Currently, the use of radioactive primary reagent ion source and the humidity interference on the sensitivity and stability are the two major issues faced by chemical ionization mass spectrometer (CIMS) in the analysis of atmospheric ammonia. In this work, a vacuum ultraviolet (VUV) Kr lamp was used to replace the radioactive source, and acetone was ionized under atmospheric pressure to obtain protonated acetone reagent ions to ionize ammonia. The ionization source is designed as a separated three-zone structure, and even 90 vol.% high-humidity samples can still be directly analyzed with a sensitivity of sub-ppbv. A signal normalization processing method was designed, and with this new method, the quantitative relative standard deviation (RSD) of the instrument was decreased from 17.5% to 9.1%, and the coefficient of determination was increased from 0.8340 to 0.9856. The humidity correction parameters of the instrument were calculated from different humidity, and the ammonia concentrations obtained under different humidity were converted to its concentration under zero humidity condition with these correction parameters. The analytical time for a single sample is only 60 sec, and the limit of detection (LOD) was 8.59 pptv (signal-to-noise ratio S/N = 3). The ambient measurement made in Qingdao, China, in January 2021 with this newly designed CIMS, showed that the concentration of ammonia ranged from 1 to 130 ppbv.

Reversible ammonia uptake at room temperature in a robust and tunable metal-organic framework

Ammonia is useful for the production of fertilizers and chemicals for modern technology, but its high toxicity and corrosiveness are harmful to the environment and human health. Here, we report the recyclable and tunable ammonia adsorption using a robust imidazolium-based MOF (JCM-1) that uptakes 5.7 mmol g⁻¹ of NH₃ at 298 K reversibly without structural deformation. Furthermore, a simple substitution of NO₃⁻ with Cl⁻ in a post-synthetic manner leads to an increase in the NH₃ uptake capacity of JCM-1(Cl⁻) up to 7.2 mmol g⁻¹.

Recyclable and tunable ammonia adsorption with JCM-1 and JCM-1(Cl⁻) at room temperature occurs reversibly without structural decomposition.

Differential Mortality Risks Associated With PM2.5 Components: A Multi-Country, Multi-City Study

BACKGROUND

The association between fine particulate matter (PM2.5) and mortality widely differs between as well as within countries. Differences in PM2.5 composition can play a role in modifying the effect estimates, but there is little evidence about which components have higher impacts on mortality.

METHODS

We applied a 2-stage analysis on data collected from 210 locations in 16 countries. In the first stage, we estimated location-specific relative risks (RR) for mortality associated with daily total PM2.5 through time series regression analysis. We then pooled these estimates in a meta-regression model that included city-specific logratio-transformed proportions of seven PM2.5 components as well as meta-predictors derived from city-specific socio-economic and environmental indicators.

RESULTS

We found associations between RR and several PM2.5 components. Increasing the ammonium (NH4+) proportion from 1% to 22%, while keeping a relative average proportion of other components, increased the RR from 1.0063 (95% confidence interval [95% CI] = 1.0030, 1.0097) to 1.0102 (95% CI = 1.0070, 1.0135). Conversely, an increase in nitrate (NO3-) from 1% to 71% resulted in a reduced RR, from 1.0100 (95% CI = 1.0067, 1.0133) to 1.0037 (95% CI = 0.9998, 1.0077). Differences in composition explained a substantial part of the heterogeneity in PM2.5 risk.

CONCLUSIONS

These findings contribute to the identification of more hazardous emission sources. Further work is needed to understand the health impacts of PM2.5 components and sources given the overlapping sources and correlations among many components.

Relocate 10 billion livestock to reduce harmful nitrogen pollution exposure for 90% of China's population

Livestock production in China is increasingly located near urban areas, exposing human populations to nitrogen pollution via air and water. Here we analyse livestock and human population data across 2,300 Chinese counties to project the impact of alternative livestock distributions on nitrogen emissions. In 2012 almost half of China's livestock production occurred in peri-urban regions, exposing 60% of the Chinese population to ammonia emissions exceeding UN guidelines. Relocating 5 billion animals by 2050 according to crop-livestock integration criteria could reduce nitrogen emissions by two-thirds and halve the number of people exposed to high ammonia emissions. Relocating 10 billion animals away from southern and eastern China could reduce ammonia exposure for 90% of China's population. Spatial planning can therefore serve as a powerful policy instrument to tackle nitrogen pollution and exposure of humans to ammonia.

Use of ammonium sulphate as a sulphur fertilizer: Implications for ammonia volatilization

Ammonium sulphate is widely used as a sulphur (S) fertilizer, constituting about 50% of global S use. Within nitrogen (N) management, it is well known that ammonium-based fertilizers are subject to ammonia (NH₃) volatilization in soils with pH > 7, but this has been overlooked in decision making on S fertilization. We reviewed 41 publications reporting measurements of NH₃ loss from ammonium sulphate in 16 countries covering a wide range of soil types and climates. In field experiments, loss was mostly <5% of applied N in soils with pH (in water) <7.0. In soils with pH > 7.0, there was a wide range of losses (0%-66%), with many in the 20%-40% range and some indication of increased loss (ca. 5%-15%) in soils with pH 6.5-7.0. We estimate that replacing ammonium sulphate with a different form of S for arable crops could decrease NH₃ emissions from this source by 90%, even taking account of likely emissions from alternative fertilizers to replace the N, but chosen for low NH₃ emission. For every kt of ammonium sulphate replaced on soils of pH > 7.0 in temperate regions, NH₃ emission would decrease from 35.7 to 3.6 t NH₃. Other readily available sources of S include single superphosphate, potassium sulphate, magnesium sulphate, calcium sulphate dihydrate (gypsum), and polyhalite (Polysulphate). In view of the large areas of high pH soils globally, this change of S fertilizer selection would make a significant contribution to decreasing NH₃ emissions worldwide, contributing to necessary cuts to meet agreed ceilings under the Gothenburg Convention.

Atmospheric ammonia and its effect on PM2.5 pollution in urban Chengdu, Sichuan Basin, China

Controlling ammonia (NH₃) emissions has been proposed as a strategy to mitigate haze pollution. To explore the role of NH₃ in haze pollution in Sichuan Basin, where agricultural activities are intense, hourly in situ data of NH₃, as well as nitric acid and secondary inorganic aerosols (SIAs) were gathered in Chengdu from April 2017 to March 2018. We found that NH₃ had an annual mean concentration of 9.7 ± 3.5 (mean ± standard deviation) μg m^-3, and exhibited seasonal variations (spring > summer > autumn and winter) due to changes in emission sources and meteorological conditions (particularly temperature). Chengdu's atmosphere is generally NH₃-sufficient, especially in the warm seasons, implying that the formation of SIAs is more sensitive to the availability of nitric acid. However, an NH₃ "sufficient-to-deficient" transition was found to occur during winter pollution periods, and the frequency of NH₃ deficiency increased with the aggravation of pollution. Under NH₃-deficient conditions, the nitrogen oxidation ratio increased linearly with the increase in free NH₃, implying that NH₃ contributes appreciably to the formation of nitrate and thus to high PM_2.5 loadings. No relationships of NH₃ with fossil fuel combustion-related pollutants were found. The NH₃ emissions from farmland and livestock waste in the suburbs of Chengdu and regional transport from west of Chengdu probably contribute to the occurrence of high PM_2.5 loading in winter and spring, respectively. These results suggest that to achieve effective mitigation of PM_2.5 in Chengdu, local and regional emission control of NH₃ and NOx synergistically would be effective.

Ammonia exposure induced intestinal inflammation injury mediated by intestinal microbiota in broiler chickens via TLR4/TNF-α signaling pathway

Ammonia is a known environmental pollutant that causes injury to the intestine. Growing evidence suggests that intestinal microbiota dysbiosis involves in the development of intestinal injury under environmental pollution. However, the specific mechanism remains unexplored. To do this, broiler chicken ileal exposed to ammonia was selected as the research object. Further, antibiotic depletion of intestinal microbiota and flora transplantation were used to clarify the role of intestinal microbiota in the intestinal injury. Histopathological examination indicated inhaled ammonia caused intestinal injury. Then we observed a decrease in intestinal muc-2, claudin-1, IL-6, IL-10 in ammonia inhalation, as opposed to the control group, associated with a significant increase in TLR4, MyD88, NF-κB, TNF-α, IL-1β, caspase3. Moreover, there was a significant increase of Streptococcus, Escherichia-Shigella, Faecalibacterium, [Ruminococcus]_torques_group, Ruminococcaceae_UCG-014, unclassified_f_Lachnospiraceae, Rothia, unclassified_f_Ruminococcaceae in the inhaled ammonia exposure. Correlation analysis suggested that the altered genera were positively correlated with the expression of TLR4 and TNF-α. Moreover, transferring intestinal microbiota from ammonia exposure broiler into healthy broiler caused intestinal injury and increased TLR4 and TNF-α concentrations in recipient broiler. Furthermore, antibiotic depletion of intestinal microbiota attenuated ammonia-caused intestinal injury and reduced TLR4 and TNF-α productions. In summary, TLR4/TNF-α signaling pathway was an important regulated mechanism involved in the intestinal injury mediated by intestinal microbiota dysbiosis under inhaled ammonia.

Strategies to reduce ammonia emissions from livestock and their cost-benefit analysis: A case study of Sheyang county

Ammonia (NH₃) emissions, the majority of which arise from livestock production, are linked to high concentration of PM_2.5 and lower air quality in China. NH₃ mitigation options were well studied at the small-scale (laboratory or pilot), however, they lack of a large-scale test in China. This study fills this crucial gap by evaluating the cost-benefit of pioneering NH₃ mitigation projects carried out for a whole county - Sheyang, Jiangsu province, China. Measures were implemented in 2019 following two distinct strategies, improved manure treatment for industrial livestock farms, and collection and central treatment for traditional livestock farms. Emission reductions of 16% were achieved in a short time. While this is remarkable, it falls short of expectations from small-scale studies. If measures were fully implemented according to purpose and meet expectations from the small scale, higher emission reductions of 42% would be possible. The cost benefit analysis presented in this study demonstrated advantages of central manure treatment over in-farm facilities. With improved implementation of mitigation strategies in industrial livestock farms, traditional livestock farms may play an increasing role in total NH₃ emissions, which means such farms either need to be included in future NH₃ mitigation policies or gradually replaced by industrial livestock farms. The study found an agricultural NH₃ reduction technology route suitable for China's national conditions (such as the "Sheyang Model").

Geospatial Correlation Analysis between Air Pollution Indicators and Estimated Speed of COVID-19 Diffusion in the Lombardy Region (Italy)

Background: the Lombardy region in Italy was the first area in Europe to record an outbreak of COVID-19 and one of the most affected worldwide. As this territory is strongly polluted, it was hypothesized that pollution had a role in facilitating the diffusion of the epidemic, but results are uncertain. Aim: the paper explores the effect of air pollutants in the first spread of COVID-19 in Lombardy, with a novel geomatics approach addressing the possible confounding factors, the reliability of data, the measurement of diffusion speed, and the biasing effect of the lockdown measures. Methods and results: all municipalities were assigned to one of five possible territorial classes (TC) according to land-use and socio-economic status, and they were grouped into districts of 100,000 residents. For each district, the speed of COVID-19 diffusion was estimated from the ambulance dispatches and related to indicators of mean concentration of air pollutants over 1, 6, and 12 months, grouping districts in the same TC. Significant exponential correlations were found for ammonia (NH₃) in both prevalently agricultural (R² = 0.565) and mildly urbanized (R² = 0.688) areas. Conclusions: this is the first study relating COVID-19 estimated speed of diffusion with indicators of exposure to NH₃. As NH₃ could induce oxidative stress, its role in creating a pre-existing fragility that could have facilitated SARS-CoV-2 replication and worsening of patient conditions could be speculated.

Real-time on-site monitoring of soil ammonia emissions using membrane permeation-based sensing probe

An ability to real-time, continuously monitor soil ammonia emission profiles under diverse meteorological conditions with high temporal resolution in a simple and maintenance-free fashion can provide the urgently needed scientific insights to mitigate ammonia emission to the atmosphere and improve agricultural fertilization practice. Here, we report an open-chamber deployment unit embedded a gas-permeable membrane-based conductometric sensing probe (OC-GPMCP) capable of on-site continuously monitoring soil ammonia emission flux ( [Formula: see text] ) -time (t) profiles without the need for ongoing calibration. The developed OC-GPMCPs were deployed to a sugarcane field and a cattle farm under different fertilization/meteorological conditions to exemplify their real-world applicability for monitoring soil ammonia emission from agricultural land and livestock farm, respectively. The obtained [Formula: see text] - t profiles from the sugarcane field unveil that the ammonia emission rate is largely determined by fertilization methods and meteorological conditions. While the [Formula: see text] - t profiles from the cattle farm can be decisively correlated to various meteorological conditions. The reported OC-GPMCP is cheap to fabricate, easy to deploy, and maintenance-free to operate. These advantageous features make OC-GPMCP an effective analytical tool for large-scale soil ammonia emission assessment under diverse meteorological conditions, providing critically important scientific insights to mitigate ammonia emission into the atmosphere and improve agricultural fertilization practice.

Nitrogen emission and deposition budget in an agricultural catchment in subtropical central China

The study of emissions and depositions of atmospheric reactive nitrogen species (N_rs) in a region is important to uncover the sources and sinks of atmospheric N_rs in the region. In this study, atmospheric total N_rs depositions including both wet-only and dry deposition were monitored simultaneously across major land-use types in a 105 km² catchment called Jinjing River Catchment (JRC) in subtropical central China from 2015 to 2016. Based on activity data and emission factors for the main N_rs emission sources, ammonia (NH₃) and nitrogen oxides (NO_x) emission inventories for the catchment were also compiled. The estimated total N_rs deposition in JRC was 35.9 kg N ha^-1 yr^-1, with approximately 49.7 % attributed to reduced compounds (NH_x), and 40.5 % attributed to oxidized (NO_y). The total N_rs emission rate in JRC was 80.4 kg N ha^-1 yr^-1, with 61.5 and 18.9 kg N ha^-1 yr^-1 from NH₃ and NO_x emissions, respectively. Livestock excretion and fertilization were the two main contributing emission sources for NH₃, while vehicle sources contributed the bulk of NO_x emissions. The net atmospheric budgets of N_rs in paddy field, forest, and tea field were +3.7, -36.1, and +23.8 kg N ha^-1 yr^-1, respectively. At the catchment scale, the net atmospheric budget of N_rs was +47.7 kg N ha^-1 yr^-1, with +43.7 kg N ha^-1 yr^-1 of NH_x and +4.0 kg N ha^-1 yr^-1 of NO_y, indicating that the subtropical catchment was net sources of atmospheric N_rs. Considering that excessive atmospheric N_r emissions and deposition may cause adverse effects on the environment, effects should be conducted to mitigate the N_rs emissions from agriculture and transportation, and increasing the area of forest is good for reducing the net positive budget of atmospheric N_rs in the subtropical catchments in China.

Abating ammonia is more cost-effective than nitrogen oxides for mitigating PM2.5 air pollution

[Figure: see text].

Mitigation potential of global ammonia emissions and related health impacts in the trade network

Ammonia (NH3) emissions, mainly from agricultural sources, generate substantial health damage due to the adverse effects on air quality. NH3 emission reduction strategies are still far from being effective. In particular, a growing trade network in this era of globalization offers untapped emission mitigation potential that has been overlooked. Here we show that about one-fourth of global agricultural NH3 emissions in 2012 are trade-related. Globally they induce 61 thousand PM2.5-related premature mortalities, with 25 thousand deaths associated with crop cultivation and 36 thousand deaths with livestock production. The trade-related health damage network is regionally integrated and can be characterized by three trading communities. Thus, effective cooperation within trade-dependent communities will achieve considerable NH3 emission reductions allowed by technological advancements and trade structure adjustments. Identification of regional communities from network analysis offers a new perspective on addressing NH3 emissions and is also applicable to agricultural greenhouse gas emissions mitigation.

Characteristics of ambient ammonia and its effects on particulate ammonium in winter of urban Beijing, China

To understand the characteristics of winter fine aerosol pollution in Beijing, we conducted continuous measurements of the atmospheric trace gas ammonia (NH3), PM2.5, and inorganic ions in PM2.5 at an urban site in Beijing from February 13 to March 17, 2015. The hourly average concentration of NH3 throughout the campaign was 15.4 ± 17.5 ppb. NH3 concentrations correlated well with NH4+ in PM2.5, indicating the dominant precursor role of NH3 on NH4+ formation. The diurnal profile indicated an increase in NH3 concentrations during the morning rush hours, which was likely due to vehicle emissions. The mean ammonium conversion ratio (NHR) was 0.26, with the highest value of 0.32 in the afternoon. Elevated NHR, nitrate oxidation ratio (NOR), and NH4+ coincided with the significant increase in O3 levels in the afternoon, indicating the large daytime formation of NH4NO3 via photochemical reactions. Moreover, higher NHR values occurred under higher relative humidity (RH >60%) and lower temperature (0-10 °C). NHR increased during the nighttime and correlated well with RH, indicating the dominant role of heterogeneous reactions on gas-particle partitioning. The sulfate oxidation ratio (SOR) and NOR showed positive correlations with RH, which suggests that the conversions of SO2 to SO42- and NO2 to NO3- were sensitive to changes in RH. The sustained increase in SO42- concentrations at RH >60% suggests that RH had a higher influence on SO42- formation than on NO3- formation. As the sole precursor of NH4+, NH3 significantly enhanced daytime NH4NO3 formation via homogeneous gas-phase reactions and also promoted sulfate formation via both homogeneous and heterogeneous reactions. Moreover, the back trajectory results inferred a high contribution of southwestern air masses to atmospheric NH3 and NH4+ aerosol variations in Beijing. The result suggests the need for controlling the vehicle emissions to reduce the high levels of NH3 and alleviate PM2.5 pollution in winter in Beijing.

Exposure to PM2.5 induces neurotoxicity, mitochondrial dysfunction, oxidative stress and inflammation in human SH-SY5Y neuronal cells

Ambient air pollution is a global public health issue. Recent evidence suggests that exposure to fine aerosolized particulate matter (PM) as small as ≤2.5 microns (PM_2.5) is neurotoxic to brain structures. Many studies also suggest exposure to PM_2.5 may cause neurotoxicity and affect brain function. However, the molecular mechanisms by which PM_2.5 exerts these effects are not fully understood. Thus, we evaluated the hypothesis that PM_2.5 exposure exerts its neurotoxic effects via increased oxidative and inflammatory cellular damage and mitochondrial dysfunction using human SH-SY5Y neuronal cells. Here, we show PM_2.5 exposure significantly decreases viability, and increases caspase 3 and 9 protein expression and activity in SH-SY5Y cells. In addition, PM_2.5 exposure decreases SH-SY5Y survival, disrupts cell and mitochondrial morphology, and significantly decreases ATP levels, D-loop levels, and mitochondrial mass and function (maximal respiratory function, COX activity, and mitochondrial membrane potential) in SH-SY5Y cells. Moreover, SH-SY5Y cells exposed to PM_2.5 have significantly decreased mRNA and protein expression levels of survival genes (CREB and Bcl-2) and neuroprotective genes (PPARγ and AMPK). We further show SH-SY5Y cells exposure to PM_2.5 induces significant increases in the levels of oxidative stress, and expression levels of the inflammatory mediator's TNF-α, IL-1β, and NF-κB. Taken together, these results provide the first evidence of the biochemical, molecular and morphological effects of PM_2.5 on human neuronal SH-SY5Y cells, and support our hypothesis that increased mitochondrial disruption, oxidative stress and inflammation are critical mediators of its neurotoxic effects. These findings further improve our understanding of the neuronal cell impact of PM_2.5 exposure, and may be useful in the design of strategies for the treatment and prevention of human neurodegenerative disorders.

Effects of Anthropogenic Emissions from Different Sectors on PM2.5 Concentrations in Chinese Cities

PM_2.5 pollution has gradually attracted people's attention due to its important negative impact on public health in recent years. The influence of anthropogenic emission factors on PM_2.5 concentrations is more complicated, but their relative individual impact on different emission sectors remains unclear. With the aid of the geographic detector model (GeoDetector), this study evaluated the impacts of anthropogenic emissions from different sectors on the PM_2.5 concentrations of major cities in China. The results indicated that the influence of anthropogenic emissions factors with different emission sectors on PM_2.5 concentrations exhibited significant changes at different spatial and temporal scales. Residential emissions were the dominant driver at the national annual scale, and the NO_X of residential emissions explained 20% (q = 0.2) of the PM_2.5 concentrations. In addition, residential emissions played the leading role at the regional annual scale and during most of the seasons in northern China, and ammonia emissions from residents were the dominant factor. Traffic emissions play a leading role in the four seasons for MUYR and EC in southern China, MYR and NC in northern China, and on a national scale. Compared with primary particulate matter, secondary anthropogenic precursors have a more important effect on PM_2.5 concentrations at the national or regional annual scale. The results can help to strengthen our understanding of PM_2.5 pollution, improve PM_2.5 forecasting models, and formulate more precise government control policy.

Emerging MXene-Polymer Hybrid Nanocomposites for High-Performance Ammonia Sensing and Monitoring

Ammonia (NH3) is a vital compound in diversified fields, including agriculture, automotive, chemical, food processing, hydrogen production and storage, and biomedical applications. Its extensive industrial use and emission have emerged hazardous to the ecosystem and have raised global public health concerns for monitoring NH3 emissions and implementing proper safety strategies. These facts created emergent demand for translational and sustainable approaches to design efficient, affordable, and high-performance compact NH3 sensors. Commercially available NH3 sensors possess three major bottlenecks: poor selectivity, low concentration detection, and room-temperature operation. State-of-the-art NH3 sensors are scaling up using advanced nano-systems possessing rapid, selective, efficient, and enhanced detection to overcome these challenges. MXene-polymer nanocomposites (MXP-NCs) are emerging as advanced nanomaterials of choice for NH3 sensing owing to their affordability, excellent conductivity, mechanical flexibility, scalable production, rich surface functionalities, and tunable morphology. The MXP-NCs have demonstrated high performance to develop next-generation intelligent NH3 sensors in agricultural, industrial, and biomedical applications. However, their excellent NH3-sensing features are not articulated in the form of a review. This comprehensive review summarizes state-of-the-art MXP-NCs fabrication techniques, optimization of desired properties, enhanced sensing characteristics, and applications to detect airborne NH3. Furthermore, an overview of challenges, possible solutions, and prospects associated with MXP-NCs is discussed.

Analysis of Basic Physical and Chemical Characteristics of Manganese Slag before and after Solidification and Its Feasibility as Highway Slope

Manganese slag is a kind of industrial waste produced by electrolytic production of manganese metal. The traditional method of stacking manganese slag not only causes waste of resources, but also produces environmental pollution. Finding harmless, effective, and economical disposal technology of manganese slag has gradually become a research hotspot and difficulty in the field of electrolytic manganese industry and environmental protection. To verify the feasibility of using manganese slag as roadbed material, the basic physical and chemical properties of manganese slag were analyzed based on X-ray diffraction, X-ray fluorescence spectrum, SEM scanning electron microscope, and particle analysis, the basic engineering characteristics of raw materials of manganese slag and solidified manganese slag mixed with quicklime were analyzed through a compaction test and a CBR test. Finally, based on the Monte Carlo method, the stability of a highway slope in the Guizhou Province of China is simulated by the finite element method, considering the spatial variability of manganese slag material strength parameters. The results show that the solidified manganese slag material can be used as highway subgrade material. This study has important reference significance for manganese slag highway construction projects.

Altering the substituents of salicylic acid to improve Berthelot reaction for ultrasensitive colorimetric detection of ammonium and atmospheric ammonia

The Berthelot reaction is a classic method for detection of ammonium (NH₄⁺) and atmospheric ammonia (NH₃) by using salicylic acid (SA) as the chromogenic substrate. However, there lacks a method for improving the activity of the Berthelot reaction to enhance the analytical performance for detection of NH₄⁺ and NH₃. Here, five SA analogues with electron-withdrawing groups (-F) and electron-donating groups (-CH₃ and -OCH₃) at different positions of the aromatic ring have been chosen as the alternative to SA for Berthelot reaction. Among these analogues, 4-methoxysalicylic acid (4-OCH₃-SA) shows the best colorimetric response and color change at a NH₄⁺ concentration of 30 μM, and the sensitivity of 4-OCH₃-SA-based colorimetric assay for NH₄⁺ increases 1.75-fold compared with that of SA-based colorimetric method. This enhancement effect is attributed to the strong electron-donating property of 4-OCH₃ group, activating the two-step electrophilic aromatic substitution reaction in the Berthelot reaction. Additionally, visual and sensitive detection of NH₃ is realized, along with a low limit of detection down to 0.037 ppm. Furthermore, we demonstrate that this assay is reliable and practical for detection of NH₄⁺ and NH₃ in real water and air samples with good accuracy.

The antecedents and outcomes of transformational leadership: leader's self-transcendent value, follower's environmental commitment and behavior

Purpose

The primary purpose of this paper is to identify the antecedent (i.e. leader's self-transcendent value) and outcomes (i.e. follower's environmental commitment and behavior) of transformational leadership. The second purpose is to examine the mediating role of transformational leadership plays in the relationship between leader's self-transcendent value and follower's environmental commitment and behavior.

Design/methodology/approach

Multi-source data were collected at multiple times in China. A total of 262 employees and their 64 supervisors completed the survey. The authors conducted a series of confirmatory factor analyses (CFAs) to verify the validity of the constructs and adopted the SPSS PROCESS macro with bootstrapping techniques to test the hypotheses.

Findings

The authors find that leader's self-transcendent value is an important antecedent of transformational leadership, and transformational leadership can enhance followers' environmental commitment and foster their environmental behavior. Besides, transformational leadership plays a significant mediating role between leader's self-transcendent value and follower's environmental commitment and behavior.

Originality/value

This study has developed an integrated model of the antecedents and outcomes of transformational leadership in the Chinese context. It also confirmed that transformational leadership mediates the process through which leader's self-transcendent value has a positive impact on follower's environmental commitment and behavior.

Mitigating NOX emissions does not help alleviate wintertime particulate pollution in Beijing-Tianjin-Hebei, China

Stringent mitigation measures have reduced wintertime fine particulate matter (PM_2.5) concentrations by 42.2% from 2013 to 2018 in the Beijing-Tianjin-Hebei (BTH) region, but severe PM pollution still frequently engulfs the region. The observed nitrate aerosols have not exhibited a significant decreasing trend and constituted a major fraction (about 20%) of the total PM_2.5, although the surface-measured NO₂ concentration has decreased by over 20%. The contributions of nitrogen oxides (NO_X) emissions mitigation to the nitrate and PM_2.5 concentrations and how to alleviate nitrate aerosols efficiently under the current situation still remains elusive. The WRF-Chem model simulations of a persistent and heavy PM pollution episode in January 2019 in the BTH reveal that NO_X emissions mitigation does not help lower wintertime nitrate and PM_2.5 concentrations under current conditions in the BTH. A 50% reduction in NO_X emissions only decreases nitrate mass by 10.3% but increases PM_2.5 concentrations by 3.2%, because the substantial O₃ increase induced by NO_X mitigation offsets the HNO₃ loss and enhances sulfate and secondary organic aerosols formation. Our results are further consolidated by the occurrence of severe PM pollution in the BTH during the COVID-19 outbreak, with a significant reduction in NO₂ concentration. Mitigation of NH₃ emissions constitutes the priority measure to effectively lower the nitrate and PM_2.5 concentrations in the BTH under current conditions, with 35.5% and 12.7% decrease, respectively, when NH₃ emissions are reduced by 50%.

Anthropogenic-Biogenic Interactions at Night: Enhanced Formation of Secondary Aerosols and Particulate Nitrogen- and Sulfur-Containing Organics from β-Pinene Oxidation

Mixing of anthropogenic gaseous pollutants and biogenic volatile organic compounds impacts the formation of secondary aerosols, but still in an unclear manner. The present study explores secondary aerosol formation via the interactions between β-pinene, O₃, NO₂, SO₂, and NH₃ under dark conditions. Results showed that aerosol yield can be largely enhanced by more than 330% by NO₂ or SO₂ but slightly enhanced by NH₃ by 39% when the ratio of inorganic gases to β-pinene ranged from 0 to 1.3. Joint effects of NO₂ and SO₂ and SO₂ and NH₃ existed as aerosol yields increased with NO₂ but decreased with NH₃ when SO₂ was kept constant. Infrared spectra showed nitrogen-containing aerosol components derived from NO₂ and NH₃ and sulfur-containing species derived from SO₂. Several particulate organic nitrates (MW 215, 229, 231, 245), organosulfates (MW 250, 264, 280, 282, 284), and nitrooxy organosulfates (MW 295, 311, 325, 327, and 343) were identified using high-resolution orbitrap mass spectrometry in NO₂ and SO₂ experiments, and their formation mechanism is discussed. Most of these nitrogen- and sulfur-containing species have been reported in ambient particles. Our results suggest that the complex interactions among β-pinene, O₃, NO₂, SO₂, and NH₃ during the night might serve as a potential pathway for the formation of particulate nitrogen- and sulfur-containing organics, especially in polluted regions with both anthropogenic and biogenic influences.

Ammonia volatilization modeling optimization for rice watersheds under climatic differences

The ammonia (NH₃) volatilization mechanism is complicated with pronounced watershed differences of climate conditions, soil properties, and tillage practices. The watershed NH₃ emission dynamics model was developed with the combination of field measurements, Soil Water Assessment Tool and NH₃ volatilization algorithms. The temporal NH₃ emissions patterns and the watershed NH₃ volatilization dynamics were simulated with the improved NH₃ volatilization modeling. Five monitoring sites and three case watersheds across China were selected to highlight the impacts of climatic conditions and validated the modeling. The average NH₃ emissions of the three watersheds ranged from 14.94 to 120.33 kg N ha^-1, which were mainly positively correlated with temperatures (r = 0.56, p < 0.01) and negatively correlated with soil organic carbon content (r = -0.33, p < 0.01). Analysis of similarities indicated that significant differences existed between the watersheds in terms of NH₃ volatilization (R_ANOSIM = 0.758 and 0.834, p < 0.01). These analysis imply that environmental variabilities were more important than N input amounts.

The importance of ammonia volatilization in estimating the efficacy of nitrification inhibitors to reduce N2O emissions: A global meta-analysis

Nitrification inhibitors (NIs) have been shown to be an effective tool to mitigate direct N₂O emissions from soils. However, emerging findings suggest that NIs may increase soil ammonia (NH₃) volatilization and, subsequently, indirect N₂O emission. A quantitative synthesis is lacking to evaluate how NIs may affect NH₃ volatilization and the overall N₂O emissions under different environmental conditions. In this meta-analysis, we quantified the responses of NH₃ volatilization to NI application with 234 observations from 89 individual studies and analysed the role of experimental method, soil properties, fertilizer/NI type, fertilizer application rate and land use type as explanatory factors. Furthermore, using data sets where soil NH₃ emission and N₂O emission were measured simultaneously, we re-evaluated the effect of NI on overall N₂O emissions including indirect N₂O emission from NH₃ volatilization. We found that, on average, NIs increased NH₃ volatilization by 35.7% (95% CI: 25.7-46.7%) and increased indirect N₂O emission from NH₃ emission (and subsequent N deposition) by 2.9%-15.2%. Responses of NH₃ volatilization mainly varied with experimental method, soil pH, NI type and fertilizer type. The increase of NH₃ volatilization following NI application showed a positive correlation with soil pH (R² = 0.04, n = 234, P < 0.05) and N fertilizer rate (R² = 0.04, n = 187, P < 0.05). When the indirect N₂O emission was considered, NI's N₂O mitigation effect decreased from 48.0% to 39.7% (EF = 1%), or 28.2% (EF = 5%). The results indicate that using DMPP with ammonium-based fertilizer in low pH, high SOC soils would have a lower risk for increasing NH₃ volatilization than using DCD and nitrapyrin with urea in high pH, lower SOC soil. Furthermore, reducing N application rate may help to improve NIs' overall N₂O emission mitigation efficiency and minimize their impact on NH₃ volatilization.

Degradation of ammonia gas by Cu2O/{001}TiO2 and its mechanistic analysis

A heterogeneous composite catalyst Cu₂O/{001}TiO₂ was successfully prepared by the impregnation-reduction method. With ammonia as the target pollutant, the degradation performance and degradation mechanism analysis of the prepared composite catalyst were investigated, providing technology for the application of photocatalysis technology in ammonia treatment reference. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), specific surface area (BET), fluorescence spectrum (PL) and UV-visible absorption (UV-Vis). The results showed: compared with single {001}TiO₂, the addition of Cu₂O to form a composite catalyst can reduce the recombination of electron-hole pairs, resulting in increased absorption intensity in the visible light range, decreased band gap width, and finally improved the degradation performance. When the composite ratio is 1 : 10, the specific surface area is the largest, which is 72.51 m² g^-1, and the degradation rate of ammonia is also the highest maintained at 85%. After repeated use for 5 times, the degradation rate of ammonia decreases gradually due to the loss of catalyst and photo-corrosion. In the whole reaction process, surface adsorbed water and associated hydroxyl radical participate in the ammonia degradation reaction, and finally form free hydroxyl radical and NO₃ ^-. It provides some theoretical support for ammonia gas treatment, which is of great significance to protect the environment.

Atmospheric Ammonia in Beijing during the COVID-19 Outbreak: Concentrations, Sources, and Implications

This study investigates the concentrations and δ15N values of NH3 in Beijing during and after the 2020 COVID-19 lockdown. Higher NH3 concentrations and lower δ15N-NH3(measured) were observed at most sites in 2020 compared to 2017. Except for a site inside a tunnel, NH3 concentrations did not increase significantly after the lockdown had ended compared to those during the lockdown, while δ15N-NH3(measured) increased by 2.1-9.9‰. Nonagricultural sources (fossil fuel and urban waste) overall contributed 81% and 62% of NH3 at on-road (tunnel interior) and nonroad (CAU) sites in 2020, respectively, comparable to those in 2017 (without significant difference). The contribution of nonagricultural sources slightly increased after the lockdown compared to the contribution during the lockdown at the nonroad site and hardly changed at the tunnel interior site. Our results suggest that (1) unfavorable meteorological conditions, especially lower boundary layer heights and changes in regional transport patterns, might play a more important role than reduced anthropogenic emissions in the temporal variations of Beijing NH3 and (2) the effect of reduced anthropogenic emissions, during the COVID-19 outbreak or with the future implementation of emission control strategies, on atmospheric NH3 can be better demonstrated by isotope-based source apportionment of NH3, rather than only by changes in NH3 concentrations.

Ammonia emissions from different pig production scales and their temporal variations in the North China Plain

Pig production systems in China are shifting from small to industrial scale. Significant variation in housing ammonia (NH₃) emissions can exist due to differences in diet, housing design, and management practices. However, there is a knowledge gap regarding the impacts of farm-scale in China, which may be critical in identifying hotspots and mitigation targets. Here, continuous in-situ NH₃ concentration measurements were made at pig farms of different scales for sows and fattening pigs over periods of 3-6 days during two different seasons (summer vs. winter). For the sow farms, NH₃ emission rates were greater at the small farm (summer: 0.52 g pig^-1 hr^-1; winter: 0.21 g pig^-1 hr^-1) than at the large farm (summer: 0.34 g pig^-1 hr^-1; winter: 0.12 g pig^-1 hr^-1). For the fattening pig farms, NH₃ emission rates were greater at the large farm (summer: 0.22 g pig^-1 hr^-1; winter: 0.16 g pig^-1 hr^-1) than at the small farm (summer: 0.19 g pig^-1 hr^-1; winter: 0.07 g pig^-1 hr^-1). Regardless of farm scale, the NH₃ emission rates measured in summer were greater than those in winter; the NH₃ emission rates were greater in the daytime than at the nighttime; a positive relationship (R² = 0.06-0.68) was established between temperature and NH₃ emission rate, whereas a negative relationship (R² = 0.10-0.47) was found between relative humidity and NH₃ emission rate. The effect of farm-scale on indoor NH₃ concentration could mostly be explained by the differences in ventilation rates between farms. The diurnal variation in NH₃ concentration could be partly explained by ventilation rate (R² = 0.48-0.78) in the small traditional farms and by emission rate (R² = 0.26-0.85) in the large industrial farms, except for the large fattening pig farm in summer. Overall, mitigation of NH₃ emissions from sow farms should be a top priority in the North China Plain. Implications: The present study firstly examined the farm-scale effect of ammonia emissions in the North China Plain. Of all farms, the sow farm was identified as the greatest source of ammonia emission. Regardless of farm scale, ammonia emission rates were observed to be higher in summer. Ammonia concentrations were mostly higher in the large industrial farms partly due to lower ventilation rates than in the small traditional farms.

Lignite Improved the Quality of Composted Manure and Mitigated Emissions of Ammonia and Greenhouse Gases during Forced Aeration Composting

Lignite amendment of livestock manure is considered a viable ammonia (NH3) emission mitigation technique. However, its impact on the subsequent composting of the manure has not been well studied. This work compared changes in biochemical parameters (e.g., organic matter loss and nitrogen (N) transformation) and also the emissions of NH3 and greenhouse gases (GHGs) between lignite-amended and unamended cattle manure during forced aeration composting. Amending manure with lignite did not alter the time to compost stability despite delaying the onset of the thermophilic temperatures. Lignite treatments retained N in the manure by suppressing NH3 loss by 35–54%, resulting in lignite-amended manure composts having 10–19% more total N than the unamended compost. Relative to manure only, lignites reduced GHG emissions over the composting period: nitrous oxide (N2O) (58–72%), carbon dioxide (CO2) (12–23%) and methane (CH4) (52–59%). Low levels of CH4 and N2O emissions were observed and this was attributed to the continuous forced aeration system used in the composting. Lignite addition also improved the germination index of the final compost: 90–113% compared to 71% for manure only. These findings suggest that lignite amendment of manure has the potential to improve the quality of the final compost whilst mitigating the environmental release of NH3 and GHGs.

Describing the trend of ammonia, particulate matter and nitrogen oxides: The role of livestock activities in northern Italy during Covid-19 quarantine

Nitrogen oxides (NOx), sulphur oxides (SOx) and ammonia (NH3) are among the main contributors to the formation of secondary particulate matter (PM2.5), which represent a severe risk to human health. Even if important improvements have been achieved worldwide, traffic, industrial activities, and the energy sector are mostly responsible for NOx and SOx release; instead, the agricultural sector is mainly responsible for NH3 emissions. Due to the emergency of coronavirus disease, in Italy schools and universities have been locked down from late February 2020, followed in March by almost all production and industrial activities as well as road transport, except for the agricultural ones. This study aims to analyze NH3, PM2.5 and NOx emissions in principal livestock provinces in the Lombardy region (Brescia, Cremona, Lodi, and Mantua) to evaluate if and how air emissions have changed during this quarantine period respect to 2016-2019. For each province, meteorological and air quality data were collected from the database of the Regional Agency for the Protection of the Environment, considering both data stations located in the city and the countryside. In the 2020 selected period, PM2.5 reduction was higher compared to the previous years, especially in February and March. Respect to February, PM2.5 released in March in the city stations reduced by 19%-32% in 2016-2019 and by 21%-41% in 2020. Similarly, NOx data of 2020 were lower than in the 2016-2019 period (reduction in March respect to February of 22-42% for 2016-2019 and of 43-62% for 2020); in particular, this can be observed in city stations, because of the current reduction in anthropogenic emissions related to traffic and industrial activities. A different trend with no reductions was observed for NH3 emissions, as agricultural activities have not stopped during the lockdown. Air quality is affected by many variables, for which making conclusions requires a holistic perspective. Therefore, all sectors must play a role to contribute to the reduction of harmful pollutants.