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 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.

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.

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.

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.

Atmospheric Particles Are Major Sources of Aged Anthropogenic Organic Carbon in Marginal Seas.

Deposition of atmospheric particulates is a major pathway for transporting materials from land to the ocean, with important implications for climate and nutrient cycling in the ocean. Here, we report the results of year-round measurements of particulate organic carbon (POC) and black carbon (BC) in atmospheric aerosols collected on Tuoji Island in the coastal Bohai-Yellow Sea of China (2019-2020) and during a cruise in the western North Pacific. Aerosol POC contents ranged from 1.

Persistent Nitrate in Alpine Waters with Changing Atmospheric Deposition and Warming Trends.

Nitrate concentrations in high-elevation lakes of the Colorado Front Range remain elevated despite declining trends in atmospherically deposited nitrate since 2000. The current source of this elevated nitrate in surface waters remains elusive, given shifts in additional nitrogen sources via glacial inputs and atmospheric ammonium deposition. We present the complete isotopic composition of nitrate (δN, δO, and ΔO) from a suite of nitrate-bearing source waters collected during the summers of 2017-2018 from two alpine ecosystems to constrain the provenance of elevated nitrate in surface waters during the summer open-water season.

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.

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.

Soil Carbon and Nitrogen Dynamics in Two Agricultural Soils Amended with Manure-Derived Biochar.

Biochar has been promoted as a means to sequester C and improve soil quality. Biochar produced from agricultural waste streams and recycled as a soil amendment also provides a strategy for improved nutrient management in agricultural systems. The effects of biochar amendment on soil C and N cycling remain poorly constrained.

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.

Development of a Fuel-Based Oil and Gas Inventory of Nitrogen Oxides Emissions.

In this study, we develop an alternative Fuel-based Oil and Gas inventory (FOG) of nitrogen oxides (NO ) from oil and gas production using publicly available fuel use records and emission factors reported in the literature. FOG is compared with the Environmental Protection Agency's 2014 National Emissions Inventory (NEI) and with new top-down estimates of NO emissions derived from aircraft and ground-based field measurement campaigns. Compared to our top-down estimates derived in four oil and gas basins (Uinta, UT, Haynesville, TX/LA, Marcellus, PA, and Fayetteville, AR), the NEI overestimates NO by over a factor of 2 in three out of four basins, while FOG is generally consistent with atmospheric observations.

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.

Nitrogen cycling during secondary succession in Atlantic Forest of Bahia, Brazil.

Carbon accumulation in tropical secondary forests may be limited in part by nitrogen (N) availability, but changes in N during tropical forest succession have rarely been quantified. We explored N cycle dynamics across a chronosequence of secondary tropical forests in the Mata Atlântica of Bahia, Brazil in order to understand how quickly the N cycle recuperates. We hypothesized that N fixation would decline over the course of succession as N availability and N gaseous losses increased.

The Nitrogen Footprint Tool Network: A Multi-Institution Program To Reduce Nitrogen Pollution.

Anthropogenic sources of reactive nitrogen have local and global impacts on air and water quality and detrimental effects on human and ecosystem health. This article uses the Nitrogen Footprint Tool (NFT) to determine the amount of nitrogen (N) released as a result of institutional consumption. The sectors accounted for include food (consumption and upstream production), energy, transportation, fertilizer, research animals, and agricultural research.

Collection Method for Isotopic Analysis of Gaseous Nitrous Acid.

The sources and chemistry of gaseous nitrous acid (HONO) in the environment are of great interest. HONO is a major source of atmospheric hydroxyl radical (OH), which impacts air quality and climate. HONO is also a major indoor pollutant that threatens human health.

Mechanisms of nitrogen deposition effects on temperate forest lichens and trees.

We review the mechanisms of deleterious nitrogen (N) deposition impacts on temperate forests, with a particular focus on trees and lichens. Elevated anthropogenic N deposition to forests has varied effects on individual organisms depending on characteristics both of the N inputs (form, timing, amount) and of the organisms (ecology, physiology) involved. Improved mechanistic knowledge of these effects can aid in developing robust predictions of how organisms respond to either increases or decreases in N deposition.

Automated, High-resolution Mobile Collection System for the Nitrogen Isotopic Analysis of NOx.

Nitrogen oxides (NOx = NO + NO2) are a family of atmospheric trace gases that have great impact on the environment. NOx concentrations directly influence the oxidizing capacity of the atmosphere through interactions with ozone and hydroxyl radicals. The main sink of NOx is the formation and deposition of nitric acid, a component of acid rain and a bioavailable nutrient.

Collection of NO and NO2 for isotopic analysis of NO(x) emissions.

There have been several measurements made of the nitrogen isotopic composition of gaseous NOx (NOx = NO + NO2) from various emission sources, utilizing a wide variety of methods to collect the NOx in solution as nitrate or nitrite. However, previous collection techniques have not been verified for complete or efficient capture of NOx such that the isotopic composition of NOx remains unaltered during collection. Here, we present a method of collecting NOx (NO + NO2) in solution as nitrate to evaluate the nitrogen isotopic composition of the NOx (δ(15)N-NOx).

Triple oxygen isotope analysis of nitrate using the denitrifier method and thermal decomposition of N2O.

Interaction with ozone transfers its anomalous (non-mass-dependent) 17O enrichment to atmospheric nitrogen oxides and nitrate. The 17O anomaly (Delta17O) in nitrate can be used to identify atmospheric nitrate inputs into terrestrial and aquatic environments as well as to study the role of ozone in the atmosphere's reactive nitrogen cycle. We report here on an online method for analysis of the 17O anomaly, using a strain of denitrifiers to convert nitrate to N2O, which decomposes quantitatively to N2 and O2 in a gold furnace at 800 degrees C, followed by gas chromatographic separation and isotope analysis of O2.

Intercontinental transport of air pollution: will emerging science lead to a new hemispheric treaty?

We examine the emergence of InterContinental Transport (ICT) of air pollution on the agendas of the air quality and climate communities and consider the potential for a new treaty on hemispheric air pollution. ICT is the flow of air pollutants from a source continent (e.g.