Investigating atmospheric nitrate sources and formation pathways between heating and non-heating seasons in urban North China

Abstract In urban North China, nitrate ( NO 3 − ) is a primary contributor to haze formation. So far, the production processes and source apportionments of atmospheric NO 3 − during the heating season (i.e. the wintertime) have not yet been well understood. This study determined δ 15 N– NO 3 − , δ 1...

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Bibliographic Details
Published in:Environmental research letters 2023-03, Vol.18 (3), p.34006
Main Authors: Yan, Xiao, Hu, Beibei, Li, Yilan, Shi, Guitao
Format: Article
Language:English
Subjects:
Combustion
Dimethyl sulfate
Dust storms
Emissions
Fractionation
Haze
Heating
heating season
Isotope composition
Mitigation
MixSIAR
nitrate formation
Nitrates
Nitrogen oxides
Photochemicals
Pollution control
Relative humidity
Seasons
Soil microorganisms
stable isotope
Stable isotopes
Wind speed
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Summary:Abstract In urban North China, nitrate ( NO 3 − ) is a primary contributor to haze formation. So far, the production processes and source apportionments of atmospheric NO 3 − during the heating season (i.e. the wintertime) have not yet been well understood. This study determined δ 15 N– NO 3 − , δ 18 O– NO 3 − , and Δ 17 O– NO 3 − of aerosol samples to compare the potential sources and formation pathways of atmospheric NO 3 − during heating (November to March) and non-heating (April to May) seasons. Combining stable isotope composition with the MixSIAR model based on Δ 17 O– NO 3 − showed that NO 3 + DMS/HC (dimethyl sulfate/hydrocarbon) pathway was the dominant process of atmospheric nitrate formation during the heating season (mean = 52.88 ± 16.11%). During the non-heating season, the contributions of NO 3 + DMS/HC (mean = 37.89 ± 13.57%) and N 2 O 5 + H 2 O (mean = 35.24 ± 3.75%) pathways were comparable. We found that Δ 17 O– NO 3 − was negatively correlated with wind speed and positively correlated with relative humidity during the heating season, possibly associated with the sources and production of atmospheric NO 3 − . In specific, in a dust storm event, the very low Δ 17 O– NO 3 − is likely associated with particles from land surface. Under the premise of considering 15 N fractionation, the constraint-based on δ 15 N– NO 3 − illustrated that coal combustion was the major source of NO x emission during the heating season, and the relative contribution of coal combustion decreased rapidly from the heating season (mean = 42.56 ± 15.50%) to the non-heating season (mean = 21.86 ± 4.91%). Conversely, the proportion of NO x emitted by soil microbes rose significantly from the heating (mean = 9.67 ± 5.99%) to non-heating season (mean = 24.02 ± 11.65%). This study revealed differences in the sources and formation processes of atmospheric NO 3 − during the heating and non-heating seasons, which are of significance to atmospheric nitrogen oxide/nitrate pollution mitigation.
ISSN:1748-9326
1748-9326
DOI:10.1088/1748-9326/acb805