Long-Term Evolution of Particulate Nitrate Pollution in North China: Isotopic Evidence From 10 Offshore Cruises in the Bohai Sea From 2014 to 2019

Zheng Zong, Chongguo Tian, Zeyu Sun, Yang Tan, Yajun Shi, Xiaohuan Liu, Jun Li, Yunting Fang, Yingjun Chen, Yuhao Ma, Huiwang Gao, Gan Zhang, Tao Wang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

12 Citations (Scopus)

Abstract

Atmospheric nitrate (NO3) pollution has become an obstacle to efforts to further reduce fine particulate (PM2.5) concentration in North China. However, there have been limited long-term measurements of NO3 and isotopic knowledge (δ15N, δ18O) on the driving factors during NO3 changes. Here, we report observations of 10 voyages from 2014 to 2019 conducted in the Bohai Sea, a typical background area in North China. The results show that the average proportion of NO3 in PM2.5 increased from 0.08 to 0.16 over the study period. The δ15N–NO3 ranged from −4.1‰ to +20.5‰, with a significant annual decline (p < 0.01), especially in winter. The average δ18O–NO3 was +72.6 ± 13.5‰, and a Monte Carlo calculation revealed that the contribution of the •OH pathway in the NO3 formation declined by 27.4% in winter, implying an increase in O3 pollution. Coal combustion remained the most important contributor to NO3 (46.6 ± 15.9%), but its contribution showed a significant downward trend (p < 0.01), consistent with the control of disperse coal use in North China. Enhancement of atmospheric oxidation and the unexpected large increase in contribution of microbial processes were found to be the main causes of the increasingly serious NO3 pollution in North China. In addition, a spike in the contribution of coal combustion in 2018 indicates that the coal-control policy needs to be reinforced.

Original languageEnglish
Article numbere2022JD036567
JournalJournal of Geophysical Research: Atmospheres
Volume127
Issue number11
DOIs
Publication statusPublished - 16 Jun 2022

ASJC Scopus subject areas

  • Atmospheric Science
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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