Vertical measurements of stable nitrogen and oxygen isotope composition of fine particulate nitrate aerosol in Guangzhou city: Source apportionment and oxidation pathway

Yujing Wang; Junwen Liu; Fan Jiang; Zixi Chen; Lili Wu; Shengzhen Zhou; Chenglei Pei; Ye Kuang; Fang Cao; Yanlin Zhang; Meiyi Fan; Junyu Zheng; Jun Li; Gan Zhang

doi:10.1016/j.scitotenv.2022.161239

Vertical measurements of stable nitrogen and oxygen isotope composition of fine particulate nitrate aerosol in Guangzhou city: Source apportionment and oxidation pathway

Sci Total Environ. 2023 Mar 20:865:161239. doi: 10.1016/j.scitotenv.2022.161239. Epub 2022 Dec 29.

Authors

Yujing Wang¹, Junwen Liu², Fan Jiang¹, Zixi Chen¹, Lili Wu¹, Shengzhen Zhou³, Chenglei Pei⁴, Ye Kuang¹, Fang Cao⁵, Yanlin Zhang⁵, Meiyi Fan⁶, Junyu Zheng¹, Jun Li⁷, Gan Zhang⁷

Affiliations

¹ Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China.
² Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China. Electronic address: liu.junwen@jnu.edu.cn.
³ School of Atmospheric Sciences, Guangdong Provincial Field Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, Sun Yat-sen University, Guangzhou 510275, China.
⁴ Guangzhou Sub-branch of Guangdong Ecological and Environmental Monitoring Center, Guangzhou 510308, China.
⁵ Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change, Nanjing University of Information Science and Technology, Nanjing 210044, China.
⁶ Department of Civil and Environmental Engineering, the Hong Kong Polytechnic University, 999077, Hong Kong, China.
⁷ Department of Civil and Environmental Engineering, the Hong Kong Polytechnic University, 999077, Hong Kong, China; State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.

PMID: 36587665
DOI: 10.1016/j.scitotenv.2022.161239

Abstract

Nowadays, the emission source and formation mechanism of fine particulate nitrate (pNO₃^-) in China are mired in controversy. In this study, the stable nitrogen isotope (δ¹⁵N-NO₃^-) and triple oxygen isotope (Δ¹⁷O-NO₃^-) were determined for the pNO₃^- samples collected at three heights under different atmospheric oxidation capacity (AOC) (O_x = O₃ + NO₂: 107 ± 29 μg m^-3 at ground, 102 ± 28 μg m^-3 at 118 m, 122 ± 23 μg m^-3 at 488 m) conditions during the sampling period based on the Canton Tower, Guangzhou, China. The Bayesian mixing model showed that coal combustion was the largest contributor to pNO₃^- in this city, followed by biomass burning, vehicle exhaust, and soil emission. Interestingly, we found that vertical NO_x and pNO₃^- concentrations displayed an opposite pattern owing to the different formation mechanisms among heights. The average contributions of oxidation pathways for (NO₂ + OH, P1), (NO₃ + DMS/HC, P2), and (N₂O₅ + H₂O, P3) were 61 %, 12 %, and 27 % at the ground, respectively, and these values would vary greatly among heights. These results implied that both AOC and NO_x loading played an important role in pNO₃^- production. The pNO₃^- displayed a positive correlation with NO_x (r = 0.95) with an enhanced contribution of the P1 pathway under the relatively high AOC condition. However, pNO₃^- has a negative correlation with NO_x (r = -0.99) with a rise of heterogeneous reaction (P2 and P3) under the relatively low AOC condition. Therefore, the current emission control strategy for air pollution in China needs to consider the AOC conditions among regions to effectively mitigate particulate air pollution.

Keywords: Emission source; Formation mechanism; Nitrate; Stable nitrogen isotope; Triple oxygen isotope.