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KMID : 0385520190320010017
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Analytical Science & Technology
2019 Volume.32 No. 1 p.17 ~ p.23
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Characterization of contribution of vehicle emissions to ambient NO2 using stable isotopes
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Park Kwang-Soo
Kim Hyuk
Yu Suk-Min
Noh Seam
Park Yu-Mi
Seok Kwang-Seol
Kim Min-Seob
Yoon Suk-Hee
Kim Young-Hee
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Abstract
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Sources of NOx are both anthropogenic (e.g. fossil fuel combustion, vehicles, and other industrial processes) and natural (e.g. lightning, biogenic soil processes, and wildfires). The nitrogen stable isotope ratio of NOx has been proposed as an indicator for NOx source partitioning, which would help identify the contributions of various NOx sources. In this study, the δ15N-NO2 values of vehicle emissions were measured in an urban region, to understand the sources and processes that influence the isotopic composition of NOx emissions. The Ogawa passive air sampler was used to determine the isotopic composition of NO2(g). In urban tunnels, the observed NO2 concentration and δ15N-NO2 values averaged 3809±2656 ppbv and 7.7±1.8‰, respectively. The observed δ15N-NO2 values are associated with slight regional variations in the vehicular NO2 source. Both NO2 concentration and δ15N-NO2 values were significantly higher near the expressway (965±125 ppbv and 5.9±1.4 ‰) than at 1.1 km from the expressway (372±96 ppbv and -11.5±2.9‰), indicating a high proportion of vehicle emissions. Ambient δ15N-NO2 values were used in a binary mixing model to estimate the percentage of the δ15N-NO2 value contributed by vehicular NOx emissions. The calculated percentage of the δ15N-NO2 contribution by vehicles was significantly higher close to the highway, as observed for the NO2 concentration and δ15N-NO2.
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KEYWORD
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nitrogen dioxide, stable isotope, passive air sampler, vehicle emission
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