Explore the vast range of titles available.

Since the industrial revolution, it has been assumed that fossil-fuel combustions dominate increasing nitrogen oxide (NO x ) emissions. However, it remains uncertain to the actual contribution of the non-fossil fuel NO x to total NO x emissions. Natural N isotopes of NO 3 − in precipitation (δ 15 N w-NO3− ) have been widely employed for tracing atmospheric NO x sources. Here, we compiled global δ 15 N w-NO3− observations to evaluate the relative importance of fossil and non-fossil fuel NO x emissions. We found that regional differences in human activities directly influenced spatial-temporal patterns of δ 15 N w-NO3− variations. Further, isotope mass-balance and bottom-up calculations suggest that the non-fossil fuel NO x accounts for 55 ± 7% of total NO x emissions, reaching up to 21.6 ± 16.6Mt yr −1 in East Asia, 7.4 ± 5.5Mt yr −1 in Europe, and 21.8 ± 18.5Mt yr −1 in North America, respectively. These results reveal the importance of non-fossil fuel NO x emissions and provide direct evidence for making strategies on mitigating atmospheric NO x pollution. This study investigates in the importance of non-fossil fuel NO x emissions in the surface-earth-nitrogen cycle. The study shows how changes of regional human activities directly influence δ 15 N signatures of deposited NO x to terrestrial environments and that emissions have largely been underestimated.

Atmospheric ammonia (NH 3 ) and ammonium (NH 4 + ) can substantially influence air quality, ecosystems, and climate. NH 3 volatilization from fertilizers and wastes (v-NH 3 ) has long been assumed to be the primary NH 3 source, but the contribution of combustion-related NH 3 (c-NH 3 , mainly fossil fuels and biomass burning) remains unconstrained. Here, we collated nitrogen isotopes of atmospheric NH 3 and NH 4 + and established a robust method to differentiate v-NH 3 and c-NH 3 . We found that the relative contribution of the c-NH 3 in the total NH 3 emissions reached up to 40 ± 21% (6.6 ± 3.4 Tg N yr −1 ), 49 ± 16% (2.8 ± 0.9 Tg N yr −1 ), and 44 ± 19% (2.8 ± 1.3 Tg N yr −1 ) in East Asia, North America, and Europe, respectively, though its fractions and amounts in these regions generally decreased over the past decades. Given its importance, c-NH 3 emission should be considered in making emission inventories, dispersion modeling, mitigation strategies, budgeting deposition fluxes, and evaluating the ecological effects of atmospheric NH 3 loading. By integrating nitrogen isotope systematics of ammonia emissions and transformations in the atmosphere, this study quantified the combustion-related ammonia emission and uncovered its importance for mitigating strategies of ammonia pollution.

Tracing sources and assessing intervention effectiveness are crucial for controlling atmospheric particulate matter (PM) pollution. Isotopic techniques enable precise top-down tracing, but the absence of long-term, global-scale multi-compound isotopic data limits comprehensive analysis. Here, we establish a blockchain-based isotopic database, compiling 34,815 isotopic fingerprints of global PM and its emissions from 1,890 pollution events across 66 countries. This allows retrospective analysis and predictions, revealing that PM sources are distinct, dynamically changing over time, and often asynchronous with interventions. Additionally, we estimate source contributions to PM 2.5 and its compounds, highlighting the increasing impact of biomass burning. Furthermore, projections indicate that by 2100, PM levels may decline to 5.38 ± 0.16 μg/m³ in the Americas and 13.9 ± 1.82 μg/m³ in Asia under climate mitigation scenarios but will still exceed WHO guidelines without further controls on natural emissions. Guiding future interventions with isotopic big data is essential for addressing air pollution challenges. A blockchain-based isotopic database compiling 34,815 isotopic fingerprints of global atmospheric particulate matter (PM) and its emissions from 1,890 pollution events is presented, enabling tracing of the ‘intervention−emissions−PM’ pathway.

Inorganic nitrate production is critical in atmospheric chemistry that reflects the oxidation capacity and the acidity of the atmosphere. Here we use the oxygen anomaly of nitrate (Δ 17 O( NO 3 − )) in high-time-resolved (3 h) aerosols to explore the chemical mechanisms of nitrate evolution in fine particles during the winter in Nanjing, a megacity of China. The continuous Δ 17 O( NO 3 − ) observation suggested the dominance of nocturnal chemistry (NO 3  + HC/H 2 O and N 2 O 5  + H 2 O/Cl − ) in nitrate formation in the wintertime. Significant diurnal variations of nitrate formation pathways were found. The contribution of nocturnal chemistry increased at night and peaked (72%) at midnight. Particularly, nocturnal pathways became more important for the formation of nitrate in the process of air pollution aggravation. In contrast, the contribution of daytime chemistry (NO 2  + OH/H 2 O) increased with the sunrise and showed a highest fraction (48%) around noon. The hydrolysis of N 2 O 5 on particle surfaces played an important role in the daytime nitrate production on haze days. In addition, the reaction of NO 2 with OH radicals was found to dominate the nitrate production after nitrate chemistry was reset by the precipitation events. These results suggest the importance of high-time-resolved observations of Δ 17 O( NO 3 − ) for exploring dynamic variations in reactive nitrogen chemistry.

The influx of atmospheric nitrogen to soils and surfaces in arid environments is of growing concern due to increased N emissions and N usage associated with urbanization. Atmospheric nitrogen inputs to the critical zone can occur as wet (rain or snow) or dry (dust or aerosols) deposition, and can lead to eutrophication, soil acidification, and groundwater contamination through leaching of excess nitrate. The objective of this research was to use the δ¹⁵N, δ¹⁸O, and Δ¹⁷O values of atmospheric nitrate (NO₃ ⁻) (precipitation and aerosols) and NO₃ ⁻ in runoff to assess the importance of N deposition and turnover in semi-arid urban watersheds. Data show that the fractions of atmospheric NO₃ ⁻ exported from all the urban catchments, throughout the study period, were substantially higher than in nearly all other ecosystems studied with mean atmospheric contributions of 38% (min 0% and max 82%). These results suggest that catchment and stream channel imperviousness enhance atmospheric NO₃ ⁻ export due to inefficient N cycling and retention. In contrast, catchment and stream channel perviousness allow for enhanced N processing and therefore reduced atmospheric NO₃ ⁻ export. Overall high fractions of atmospheric NO₃ ⁻ were primarily attributed to slow N turn over in arid/semi-arid ecosystems. A relatively high fraction of nitrification NO₃ ⁻ (~30%) was found in runoff from a nearly completely impervious watershed (91%). This was attributed to nitrification of atmospheric NH₄ ⁺ in dry-deposited dust, suggesting that N nitrifiers have adapted to urban micro niches. Gross nitrification rates based on NO₃ ⁻ Δ¹⁷O values ranged from a low 3.04 ± 2 kg NO₃-N km⁻² day⁻¹ in highly impervious catchments to a high of 10.15 ± 1 kg NO₃-N km⁻² day⁻¹ in the low density urban catchment. These low gross nitrification rates were attributed to low soil C:N ratios that control gross autotrophic nitrification by regulating gross NH₄ ⁺ production rates.

Understanding the internal distribution of \"anomalous\" isotope enrichments has important implications for validating theoretical postulates on the origin of these enrichments in molecules such as ozone and for understanding the transfer of these enrichments to other compounds in the atmosphere via mass transfer. Here, we present an approach, using the reaction NO[Formula: see text] + O₃, for assessing the internal distribution of the Δ¹⁷O anomaly and the δ¹⁸O enrichment in ozone produced by electric discharge. The Δ¹⁷O results strongly support the symmetry mechanism for generating mass independent fractionations, and the δ¹⁸O results are consistent with published data. Positional Δ¹⁷O and δ¹⁸O enrichments in ozone can now be more effectively used in photochemical models that use mass balance oxygen atom transfer mechanisms to infer atmospheric oxidation chemistry.

Particulate matter smaller than 10 μm (PM10) is an important air pollutant that adversely affects human health by increasing the risk of respiratory and cardiovascular diseases. Recent studies reported multiple extreme PM10 levels at high altitude Peruvian cities, which resulted from a combination of high emissions and limited atmospheric circulation at high altitude. However, the emission sources of the PM10 still remain unclear. In this study, we collected PM10 samples from four sites (one industrial site, one urban site, and two rural sites) at the city of Arequipa, Peru, during the period of February 2018 to December 2018. To identify the origins of PM10 at each site and the spatial distribution of PM10 emission sources, we analyzed major and trace element concentrations of the PM10. Of the observed daily PM10 concentrations at Arequipa during our sampling period, 91% exceeded the World Health Organization (WHO) 24-h mean PM10 guideline value, suggesting the elevated PM10 strongly affected the air quality at Arequipa. The concentrations of major elements, Na, K, Mg, Ca, Fe, and Al, were high and showed little variation, suggesting that mineral dust was a major component of the PM10 at all the sites. Some trace elements, such as Mn and Mo, originated from the mineral dust, while other trace elements, including Pb, Sr, Cu, Ba, Ni, As and V, were from additional anthropogenic sources. The industrial activities at Rio Seco, the industrial site, contributed to significant Pb, Cu, and possibly Sr emissions. At two rural sites, Tingo Grande and Yarabamba, strong Cu emissions were observed, which were likely associated with mining activities. Ni, V, and As were attributed to fossil fuel combustion emissions, which were strongest at the Avenida Independencia urban site. Elevated Ba and Cu concentrations were also observed at the urban site, which were likely caused by heavy traffic in the city and vehicle brake wear emissions.

We reported on the first time series of δ 15 N in aerosol nitrate from South America. Particulate matter less than 2.5 microns in diameter (PM 2.5 ) was collected at four sites located in Arequipa, a major city in southern Peru. The δ 15 N values for nitrate in PM 2.5 ranged from -1.7–15.9‰ and averaged 5.3 ± 3.0‰, with no significant difference between the four study sites and no discernable seasonal trend. These values are significantly higher than those in aerosol nitrate from southern hemisphere marine environments and those from the northern hemisphere. We explain the elevated values using an isotope mass balance mixing model that estimates a source NO x δ 15 N of -8 ± 3‰, derived mainly from anthropogenic sources (vehicles, industry). An isotope enabled 0-D photochemical box model was used to estimate the isotope enrichment of nitrate relative to NO x due to kinetic, equilibrium, and photolysis isotope effects occurring during NO x oxidation. This “source plus photochemistry” approach resulted in general agreement with the observations. This suggests that if the photochemistry effect can be accounted for, nitrate δ 15 N can be used to assess the relative importance of NO x sources and could be a new tool to validate NO x emission inventories.

Groundwater heavy metal pollution is a major concern all around the world. For the assessment of heavy metals and physico-chemical characteristics, groundwater samples were collected from different locations of the Karak District, Pakistan. With the help of the global information system device (GIS), groundwater samples were collected and studied from 47 locations. The present study focused on the water table (WT), water source depth (WSD), pH, electrical conductivity (EC), dissolved oxygen (DO), total dissolved solids (TDS), lead (Pb(II)), silver (Ag(I)), iron (Fe(II)) and chromium (Cr(VI)) parameters. Heavy metals were analyzed by the Atomic Absorption Spectrophotometer (AAS). The Pearson’s matrix of correlation showed relationships between several parameters, such as the EC and the TDS which had close interactions between all the three different groundwater samples (collected by hand pump (HP), bore holes (BH) and tube wells (TW)). The strong correlation was detected in all the sources of water between the TDS and the EC, the regression coefficient (r) of which was 1. In the hierarchical clustering (by dendrograms) the HP samples show two clusters: Cluster 1 contains seven parameters and Cluster 2 has four parameters. The BH samples have two clusters: Cluster 1 contains three parameters and Cluster 2 has eight parameters. The TW dendrogram also shows two clusters: Cluster 1 contains six parameters while Cluster 2 has five parameters.

Nitrogen isotope fractionations between nitrogen oxides (NO and NO2) play a significant role in determining the nitrogen isotopic compositions (δ15N) of atmospheric reactive nitrogen. Both the equilibrium isotopic exchange between NO and NO2 molecules and the isotope effects occurring during the NOx photochemical cycle are important, but both are not well constrained. The nighttime and daytime isotopic fractionations between NO and NO2 in an atmospheric simulation chamber at atmospherically relevant NOx levels were measured. Then, the impact of NOx level and NO2 photolysis rate on the combined isotopic fractionation (equilibrium isotopic exchange and photochemical cycle) between NO and NO2 was calculated. It was found that the isotope effects occurring during the NOx photochemical cycle can be described using a single fractionation factor, designated the Leighton cycle isotope effect (LCIE). The results showed that at room temperature, the fractionation factor of nitrogen isotopic exchange is 1.0289±0.0019, and the fractionation factor of LCIE (when O3 solely controls the oxidation from NO to NO2) is 0.990±0.005. The measured LCIE factor showed good agreement with previous field measurements, suggesting that it could be applied in an ambient environment, although future work is needed to assess the isotopic fractionation factors of NO+RO2/HO2→NO2. The results were used to model the NO–NO2 isotopic fractionations under several NOx conditions. The model suggested that isotopic exchange was the dominant factor when NOx>20 nmol mol-1, while LCIE was more important at lowNOx concentrations (<1 nmol mol-1) and high rates ofNO2 photolysis. These findings provided a useful tool to quantify the isotopic fractionations between tropospheric NO and NO2, which can be applied in future field observations and atmospheric chemistry models.