Isotopic advances in understanding reactive nitrogen deposition and atmospheric processing

Abstract

Recent advances in stable isotope measurements now allow for detailed investigations of the sources, transformations, and deposition of reactive nitrogen (N) species. Stable isotopes show promise as a complementary tool for apportioning emissions sources that contribute to deposition and also for developing a more robust understanding of the transformations that can influence these isotope ratios. Methodological advances have facilitated the unprecedented examination of the isotopic composition of reactive N species in the atmosphere and in precipitation including nitrogen oxides (NO x =nitric oxide (NO) + nitrogen dioxide (NO 2 )), atmospheric nitrate (NO 3 − ), nitric acid (HNO 3 ), and NH x ammonia (NH 3 ), and ammonium (NH 4 + )). This isotopic information provides new insight into the mechanisms of transformation and cycling of reactive N in the atmosphere and moreover help resolve the contribution of multiple NO x and NH 3 emission sources to deposition across landscapes, regions, and continents. Here, we highlight the current state of knowledge regarding the isotopic ratios of NO x and NH 3 emission sources and chemical alterations of isotopic ratios during atmospheric transformations. We also highlight illustrative examples where isotopic approaches are used and review recent methodological advances. While these highlights are not an exhaustive review of the literature, we hope they provide a glimpse of the potential for these methods to help resolve knowledge gaps regarding total N deposition to Earth surfaces. We conclude with promising opportunities for future research in the short-, medium-, and long-term.

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

“…The δ 15 N values of the initial NH 3 (denoted as δ 15 N-NH x ) were calculated using an isotope mass-balance model ( eq 1 ), 23 the measured δ 15 N-NH 3 , and the δ 15 N difference between gaseous NH 3 and particulate NH 4 + ( eq 2 ), 24 as follows: where ε (NH 4 + -NH 3 ) is the theoretical N isotopic fractionation factor between the gas and particle and equals 12.522 × 1000/ T – 11.31, 25 where T is the temperature in kelvin. f is the fraction of the initial gaseous NH 3 converted to particulate NH 4 + (NH 4 + /NH x in molar concentrations).…”

Seasonal trends of the stable nitrogen isotope ratio in particulate nitrogen compounds and their gaseous precursors in Akita, Japan

“…However, only a few studies have measured nitrogen isotopes in gases and particles collected simultaneously over extended periods and have examined isotopic fractionation during gas-particle reactions (Moore, 1977;Freyer, 1991). The review by Elliott et al (2019) described that medium-, and long-term data need for future research. In this study, stable nitrogen isotope ratios (d 15 N) of gaseous NH 3 , NO 2 , and HNO 3 (d 15 N-NH 3 , d 15 N-NO 2 , and d 15 N-HNO 3 , respectively) and of NO 3 À and NH 4 þ ions (d 15 N-NO 3 À and d 15 N-NH 4 þ , respectively) in SPM were measured for long term sampling, and the analysis results were used to examine isotope fractionation during gas-to-aerosol reactions and the sources and behavior of these compounds in the atmosphere.…”

Impact of an accidental explosion in Tianjin Port on enhanced atmospheric nitrogen deposition over the Bohai Sea inferred from aerosol nitrate dual isotopes

“…Generally, atmospheric NO 3 − is mainly derived from the conversion of NO x , of which δ 15 N of different anthropogenic and natural sources usually varies over a large range (Elliott et al 2019). For example, NO x from coal combustion owns a higher δ 15 N value, while δ 15 N from microbial processes is more negative (Hastings, Sigman, and Lipschultz 2003).…”