Seasonal isotopic trend of the gaseous nitrogen precursors and nitrogen compounds in aerosol in Akita, Japan
Abstract
Particulate matter (PM) can have adverse effects on human health. Moreover, because the mechanisms of PM formation and behavior in the atmosphere are notably complicated, to reduce PM concentrations effectively and attain environmental standards, source-receptor relationships must be clearly understood. Stable isotope ratios can be used to detect chemical processes and distinguish sources. In environmental science, especially research on aerosols, stable isotope ratios have proven to constitute a powerful tool for source identification. However, studies on isotope fractionation by secondary aerosol formation are limited, and identification is highly important. In this study, I selected ammonia gas (NH3), nitrogen dioxide gas (NO2), nitric acid vapor (HNO3) and nitrate (NO3-) and ammonium (NH4+) in suspended PM (SPM) and investigated their isotope fractionation during aerosol formation, source using nitrogen stable isotope ratio (δ15N) analysis in Akita Prefectural University. In addition, to investigate nitrogen fractionation between gas (NH3) and PM (NH4+), we measured the fractionation in the laboratory. The results indicated that δ15N-NH4+ in SPM and δ15N-NH3 in gas ranged from 1.3 to 38.5‰ (mean: 16.1‰) and -33.7 to -0.0‰ (-16.9‰), respectively. Furthermore, δ15N-NO3- in SPM and δ15N-NO2 and δ15N-HNO3 in gas ranged from -4.6 to 4.8‰ (mean: -0.5‰), -8.2 to -3.1‰ (-5.4‰) and -7.5 to 2.7‰ (-5.0‰), respectively. For isotope fractionation, the actual isotope fractionation from δ15N-NH3 to δ15N-NH4+ was +36.0‰ (spring), +34.7‰ (summer), +26.9‰ (autumn) and +35.6‰ (winter). The actual isotope fractionation in spring and summer agreed well with the results of the laboratory tests (+43‰ (2°C) and +38‰ (30°C)). Finally, the isotope fractionations from NO2 to HNO3 and from HNO3 to NO3- in aerosol were demonstrated to be approximately 0.6‰ and 4.6‰, respectively, and were consistently heavy.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A21M2911K
- Keywords:
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- 0322 Constituent sources and sinks;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0330 Geochemical cycles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES