Enhanced Nonagricultural Emissions of Ammonia Influence Aerosol Ammonium in an Urban Atmosphere: Evidence from Kinetic Versus Equilibrium Isotope Fractionation Controls on Nitrogen.

Aerosol ammonium (NH) is a critical component of particulate matter that affects air pollution, climate, and human health. Isotope-based source apportionment of NH is essential for ammonia (NH) mitigation but the role of kinetic vs equilibrium controls on nitrogen isotope (δN) fractionation between NH and NH remains unresolved. Based on concurrent measurements of NH and NH in winter Beijing, we observed that the difference of δN between NH and NH on clean days (3.

Nitrogen isotopes reveal high NO emissions from arid agricultural soils in the Salton Sea Air Basin.

Air quality management commonly aims to mitigate nitrogen oxide (NO) emissions from combustion, reducing ozone (O) and particulate matter (PM) pollution. Despite such ongoing efforts, regulations have recently proven ineffective in rural areas like the Salton Sea Air Basin of Southern California, which routinely violates O and PM air quality standards. With over $2 billion in annual agricultural sales and low population density, air quality in the region is likely influenced by the year-round farming activity.

First direct measurements of the nitrogen isotopic composition of vehicle tailpipe-emitted NH and implications for the source apportionment of NH in urban atmosphere.

The introduction of three-way catalytic converter (TWC) to meet stringent vehicular NO emission standards worldwide has led to an unintended consequence of vehicle-derived ammonia (NH) emission, which might degrade air quality and affect human health, especially in urban areas. The nitrogen stable isotope composition of NH (δN-NH) may be a useful tool to trace NH sources, but the isotopic signature of vehicle-emitted NH is lacking. Here we report the δN-NH measured from tailpipe exhausts collected directly from 19 different vehicles equipped with TWC using "grab" sample technique optimized to avoid isotopic fractionation.

Solid Phase Extraction Methodology for Robust Isotope Analysis of Atmospheric Ammonium.

The stable nitrogen isotope composition (δN) of atmospheric ammonia (NH) and ammonium (NH) has emerged as a potent tool for improving our understanding of the atmospheric burden of reduced nitrogen. However, current chemical oxidation methodologies commonly utilized for characterizing δN values of NH samples have been found to lead to low precision for low concentration (i.e.

Nitrogen Isotopes Reveal High NO Emissions from Arid Agricultural Soils in the Salton Sea Air Basin.

Air quality management commonly aims to mitigate emissions of oxides of nitrogen (NO) from combustion, reducing ozone and particulate matter pollution. Despite such efforts, regulations have recently proven ineffective in rural areas like the Salton Sea Air Basin of Southern California, which routinely violates air quality standards. With $2 billion in annual agricultural sales and low population density, air quality in the region is likely influenced by year-round farming.

Nitrogen isotopic characteristics of aerosol ammonium in a Chinese megacity indicate the reduction from vehicle emissions during the lockdown period.

The role of agricultural versus vehicle emissions in urban atmospheric ammonia (NH) remains unclear. The lockdown due to the outbreak of COVID-19 provided an opportunity to assess the role of source emissions on urban NH. Concentrations and δN of aerosol ammonium (NH) were measured before (autumn in 2017) and during the lockdown (summer, autumn, and winter in 2020), and source contributions were quantified using SIAR.

Large Seasonal Variation in Nitrogen Isotopic Abundances of Ammonia Volatilized from a Cropland Ecosystem and Implications for Regional NH Source Partitioning.

Ammonia (NH) volatilization from agricultural lands is a main source of atmospheric reduced nitrogen species (NH). Accurately quantifying its contribution to regional atmospheric NH deposition is critical for controlling regional air nitrogen pollution. The stable nitrogen isotope composition (expressed by δN) is a promising indicator to trace atmospheric NH sources, presupposing a reliable nitrogen isotopic signature of NH emission sources.

Triple oxygen stable isotope analysis of nitrite measured using continuous flow isotope ratio mass spectrometry.

Oxygen stable isotopes (i.e., O, O, O) of nitrite (NO) are useful for investigating chemical processes and sources contributing to this important environmental contaminant and nutrient.

Revisiting the dynamics of gaseous ammonia and ammonium aerosols during the COVID-19 lockdown in urban Beijing using machine learning models.

The concentration of atmospheric ammonia (NH) in urban Beijing substantially decreased during the COVID-19 lockdown (24 January to 3 March 2020), likely due to the reduced human activities. However, quantifying the impact of anthropogenic interventions on NH dynamics is challenging, as both meteorology and chemistry mask the real changes in observed NH concentrations. Here, we applied machine learning techniques based on random forest models to decouple the impacts of meteorology and emission changes on the gaseous NH and ammonium aerosol (NH) concentrations in Beijing during the lockdown.

Long-term trends in inorganic aerosol chemical composition and chemistry at an urban and rural site in the northeastern US.

Atmospheric nitrate and sulfate are major inorganic particulate matter components that impact human and ecosystem health and air quality. Over the last several decades, emissions of the precursor gases, nitrogen oxides (NO = NO + NO) and sulfur dioxide (SO), have dramatically decreased in the US in response to federal regulations. However, the response in concentrations of particulate nitrate (pNO) and sulfate (pSO) have not followed predictions due to complex non-linear chemistry feedbacks that may differ amongst environments (i.

Nitrate isotopes (N, O) in precipitation: best practices from an international coordinated research project.

Stable isotope ratios of nitrogen and oxygen (N/N and O/O) of nitrate (NO) are excellent tracers for developing systematic understanding of sources, conversions, and deposition of reactive atmospheric nitrogen (N) in the environment. Despite recent analytical advances, standardized sampling of NO) isotopes in precipitation is still lacking. To advance atmospheric studies on N species, we propose best-practice guidelines for accurate and precise sampling and analysis of NO isotopes in precipitation based on the experience obtained from an international research project coordinated by the International Atomic Energy Agency (IAEA).

Collection of Nitrogen Dioxide for Nitrogen and Oxygen Isotope Determination─Laboratory and Environmental Chamber Evaluation.

The family of atmospheric oxides of nitrogen, NO (e.g., nitrogen oxides (NO) + nitric acid (HNO) + nitrous acid (HONO) + peroxyacetyl nitrate (PAN) + particulate nitrate (pNO) + other), have an influential role in atmospheric chemistry, climate, and the environment.

Significant contributions of combustion-related sources to ammonia emissions.

Atmospheric ammonia (NH) and ammonium (NH) can substantially influence air quality, ecosystems, and climate. NH volatilization from fertilizers and wastes (v-NH) has long been assumed to be the primary NH source, but the contribution of combustion-related NH (c-NH, mainly fossil fuels and biomass burning) remains unconstrained. Here, we collated nitrogen isotopes of atmospheric NH and NH and established a robust method to differentiate v-NH and c-NH.

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

It was previously believed that ammonia (NH) has a short residence time in the atmosphere and cannot be transported far from its sources. In late March, however, this study observed a severe NH episode in urban Beijing when fertilizer was intensively applied on the North China Plain, with the highest hourly concentrations of 66.9 μg m throughout the year.

Vehicular Emissions Enhanced Ammonia Concentrations in Winter Mornings: Insights from Diurnal Nitrogen Isotopic Signatures.

A general feature in the diurnal cycle of atmospheric ammonia (NH) concentrations is a morning spike that typically occurs around 07:00 to 10:00 (LST). Current hypotheses to explain this morning's NH increase remain elusive, and there is still no consensus whether traffic emissions are among the major sources of urban NH. Here, we confirmed that the NH morning pulse in urban Beijing is a universal feature, with an annual occurrence frequency of 73.

Important contributions of non-fossil fuel nitrogen oxides emissions.

Since the industrial revolution, it has been assumed that fossil-fuel combustions dominate increasing nitrogen oxide (NO) emissions. However, it remains uncertain to the actual contribution of the non-fossil fuel NO to total NO emissions. Natural N isotopes of NO in precipitation (δN) have been widely employed for tracing atmospheric NO sources.

Speciated Collection of Nitric Acid and Fine Particulate Nitrate for Nitrogen and Oxygen Stable Isotope Determination.

Stable isotopic composition of atmospheric nitrate (nitric acid (HNO) + particulate nitrate (pNO)) provides a higher-order dimensional analysis of critical atmospheric components, enabling a process-level understanding of precursor emissions, oxidation chemistry, aerosol acidity, and depositional patterns. Current methods have not been evaluated for their ability to accurately speciate and determine nitrogen (δN) and oxygen (δO and ΔO) isotope compositions for gaseous and particle phases. Suitability of a denuder-filter sampling system for the collection of speciated HNO and pNO for off-line concentration and isotopic determination was tested using both laboratory and field collections.

Substantial nitrogen oxides emission reduction from China due to COVID-19 and its impact on surface ozone and aerosol pollution.

A top-down approach was employed to estimate the influence of lockdown measures implemented during the COVID-19 pandemic on NO emissions and subsequent influence on surface PM and ozone in China. The nation-wide NO emission reduction of 53.4% due to the lockdown in 2020 quarter one in China may represent the current upper limit of China's NO emission control.

Isotopic evidence that recent agriculture overprints climate variability in nitrogen deposition to the Tibetan Plateau.

The stable isotopes of nitrogen in nitrate archived in polar ice have been interpreted as reflecting a shift in reactive nitrogen sources or changes in atmospheric chemical reactivity. Here, we present a novel concentration and isotopic record of nitrate (δN-NO) from a central Tibetan Plateau ice core over the last ~200 years. We find that nitrate concentration increased from 6.

Analysis of biogeographic ancestry reveals complex genetic histories for indigenous communities of St. Vincent and Trinidad.

Objectives: From a genetic perspective, relatively little is known about how mass emigrations of African, European, and Asian peoples beginning in the 16th century affected Indigenous Caribbean populations. Therefore, we explored the impact of serial colonization on the genetic variation of the first Caribbean islanders.

Materials And Methods: Sixty-four members of St.

Selective Collection of Particulate Ammonium for Nitrogen Isotopic Characterization Using a Denuder-Filter Pack Sampling Device.

Nitrogen stable isotope analysis (δN) of particulate ammonium (NH) may provide additional constraints on this critical component of fine particulate matter; however, no previous collection method has been verified for its ability to accurately and precisely characterize δN(NH). This is a critical point due to the difficulty of quantitative NH collection and possible sampling artifacts. Here, we report on δN(NH) precision using an established denuder-filter pack combination with two filter configurations including (1) a nylon filter plus an acid-impregnated cellulose filter and (2) an acid-impregnated glass fiber filter for NH collection in both laboratory-controlled environments and ambient air samples.

Collection of Ammonia for High Time-Resolved Nitrogen Isotopic Characterization Utilizing an Acid-Coated Honeycomb Denuder.

Nitrogen stable isotope analysis (δN) of ammonia (NH) has shown potential to be a useful tool for characterizing emission sources and sink processes. However, to properly evaluate NH emission sources and sink processes under ambient conditions, it is necessary to collect and characterize the chemical speciation between NH and particulate ammonium (p-NH), together referred to as NH . Current NH collection methods have not been verified for their ability to accurately characterize δN-NH and/or provide necessary chemical speciation (i.

Ab initio study of nitrogen and position-specific oxygen kinetic isotope effects in the NO + O reaction.

Ab initio calculations have been carried out to investigate nitrogen (k/k) and position-specific oxygen (k/kO & k/k) kinetic isotope effects (KIEs) for the reaction between NO and O using CCSD(T)/6-31G(d) and CCSD(T)/6-311G(d) derived frequencies in the complete Bigeleisen equations. Isotopic enrichment factors are calculated to be -6.7‰, -1.