Atmospheric nitrate formation pathways in urban and rural atmosphere of Northeast China: Implications for complicated anthropogenic effects

Zhengjie Li; Wendell W Walters; Meredith G Hastings; Linlin Song; Shaonan Huang; Feifei Zhu; Dongwei Liu; Guitao Shi; Yilan Li; Yunting Fang

doi:10.1016/j.envpol.2021.118752

Atmospheric nitrate formation pathways in urban and rural atmosphere of Northeast China: Implications for complicated anthropogenic effects

Environ Pollut. 2022 Mar 1:296:118752. doi: 10.1016/j.envpol.2021.118752. Epub 2021 Dec 27.

Authors

Zhengjie Li¹, Wendell W Walters², Meredith G Hastings³, Linlin Song⁴, Shaonan Huang⁵, Feifei Zhu⁶, Dongwei Liu⁶, Guitao Shi⁷, Yilan Li⁷, Yunting Fang⁸

Affiliations

¹ National Engineering Laboratory for Applied Technology of Forestry & Ecology in Southern China, College of Biological Science and Technology, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China; CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning, 110016, China.
² Institute at Brown for Environment and Society, Brown University, Providence, RI, 02912, USA.
³ Institute at Brown for Environment and Society, Brown University, Providence, RI, 02912, USA; Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, 02912, USA.
⁴ CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning, 110016, China; Key Laboratory of Stable Isotope Techniques and Applications, Liaoning Province, 110016, China.
⁵ Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, Ministry of Education, College of Geography and Environment Science, Henan University, Kaifeng, 475004, China.
⁶ CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning, 110016, China; Qingyuan Forest CERN, Chinese Academy of Sciences, Shenyang, Liaoning, 110016, China; Key Laboratory of Stable Isotope Techniques and Applications, Liaoning Province, 110016, China.
⁷ Key Laboratory of Geographic Information Science (Ministry of Education), School of Geographic Sciences, East China Normal University, Shanghai, 200241, China.
⁸ CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning, 110016, China; Qingyuan Forest CERN, Chinese Academy of Sciences, Shenyang, Liaoning, 110016, China; Key Laboratory of Stable Isotope Techniques and Applications, Liaoning Province, 110016, China. Electronic address: fangyt@iae.ac.cn.

PMID: 34968617
DOI: 10.1016/j.envpol.2021.118752

Abstract

Effects of human activities on atmospheric nitrate (NO₃^-) formation remain unclear, though the knowledge is critical for improving atmospheric chemistry models and nitrogen deposition reduction strategies. A potentially useful way to explore this is to compare NO₃^- oxidation processes in urban and rural atmospheres based upon the oxygen stable isotope composition of NO₃^- (Δ¹⁷O-NO₃^-). Here we compared the Δ¹⁷O-NO₃^- from three-years of daily-based bulk deposition in urban (Shenyang) and forested rural sites (Qingyuan) in northeast China and quantified the relative contributions of different formation pathways based on the SIAR model. Our results showed that the Δ¹⁷O in Qiangyuan (26.2 ± 3.3‰) is significantly higher (p < 0.001) than in Shenyang (24.0 ± 4.0‰), and significantly higher in winter (Shenyang: 26.1 ± 6.7‰, Qingyuan: 29.6 ± 2.5‰) than in summer (Shenyang: 22.7 ± 2.9‰, Qingyuan: 23.8 ± 2.4‰) in both sites. The lower values in the urban site are linked with conditions that favored a higher relative contribution of nitrogen dioxide reaction with OH pathway (0.76-0.91) than in rural site (0.47-0.62), which should be induced by different levels of human activities in the two sites. The seasonal variations of Δ¹⁷O-NO₃^- in both sites are explained by a higher relative contribution of ozone-mediated oxidation chemistry and unfavorable conditions for the OH pathway during winter relative to summer, which is affected by human activities and seasonal meteorological condition change. Based on Δ¹⁷O, wintertime conditions led to a contribution of O₃ related pathways (NO₃ + DMS/HC and N₂O₅ hydrolysis) of 0.63 in Qingyuan and 0.42 in Shenyang, while summertime conditions led to 0.15 in Qingyuan and 0.05 in Shenyang. Our comparative study on Δ¹⁷O-NO₃^- between urban and rural sites reveals different anthropogenic effects on nitrate formation processes on spatial and temporal scales, illustrating different responses of reactive nitrogen chemistry to changes in human activities.

Keywords: Bulk nitrate; Nitrate formation pathways; Oxidant chemistry; Triple oxygen isotopes.

MeSH terms

Anthropogenic Effects*
China
Environmental Monitoring
Humans
Nitrates* / analysis
Nitrogen Isotopes / analysis
Seasons

Substances

Nitrates
Nitrogen Isotopes