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Characteristics of Inorganic Components and Nitrate Nitrogen-oxygen Isotopes of PM2.5 in the Chengdu City (Vol. 48, No.1, Tot No.333) TEXT SIZE: A A A

YANG Zhou1, LI Xiaodong2, LEI Guoliang3, LI Qinkai2

(1.School of Tourism and Geographical Sciences, Tongren University, Tongren 565300;
2.Institute of Surface-Earth System Sciences, Tianjin University, Tianjin, 300072;
3.College of Geographical Science, Fujian Normal University, Fuzhou 350007)

Abstract:PM2.5 samples were collected in the campus of Chengdu University of Technology in Chengdu day and night from 12 to 23 January 2013 and from 10 to 21 August 2014, mass concentrations of nine water soluble inorganic ion species and values of δ15N and δ18O in nitrate were analyzed. The results showed that mass concentrations of PM2.5 in summer and winter were 161~677μg/m3 (360±118μg/m3) and 87~137μg/m3 (92±18μg/m3), respectively, implying the severe PM2.5 pollution in winter, 2 to 9 times exceeding the PM2.5 standard, and the light PM2.5 pollution in summer, 1 to 2 times exceed the PM2.5 standard. SO42-, NO3- and NH4+ (SNA) were the major water-soluble inorganic ionic components, they accounted for 72±14.3% and 65±9.2% of the total mass of water-soluble inorganic ions and 21.1±2.5% and 30.3±6.9% of the total mass of PM2.5 in winter and summer, respectively. According to the ionic correlation analysis, the main form of SNA in PM2.5 might be (NH4)2SO4 and/or NH4HSO4 in daytime and NH4NO3 in nighttime. The values of δ15N and δ18O of nitrate in PM2.5 of Chengdu were higher in winter than in summer, indicating that sources of nitrate were coal combustion and vehicle exhaust in winter and were vehicle exhaust, coal combustion and agricultural soil release in summer. The mass ratio of [NO3-]/[SO42-] implied that the stationary sources, e.g. the coal combustion emission, were more important than the mobile sources, e.g. the vehicle emission. Nitrate in PM2.5 was mainly formed from the O3 oxidation of NOx during winter and from the ·OH oxidation of NOx and/or the hydrolysis of N2O5 in summer.

Key words:Chengdu City;fine particles;nitrate;nitrogen-oxygen isotope

EARTH AND ENVIRONMENT Vol.48, No.1, Tot No.333, 2020, Page 10-16 

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