ORIGINAL RESEARCH
Rainfall Chemistry and Total Wet and Dry Deposition of Acidity and Nitrogen in Mianyang, Southwest China
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1
School of Environment and Resource, Southwest University of Science and Technology, Mianyang 621010, China
 
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National Anti-Drug Laboratory Sichuan Regional Center, Chengdu 610031, China
 
 
Submission date: 2023-11-18
 
 
Final revision date: 2024-01-30
 
 
Acceptance date: 2024-02-25
 
 
Online publication date: 2024-06-17
 
 
Corresponding author
Huanbo Wang   

Southwest University of Science and Technology, China
 
 
 
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ABSTRACT
Wet and dry deposition samples were collected from September 2020 to August 2021 at a suburban site in Mianyang, Southwest China. Major water-soluble inorganic ions (WSIIs) in daily rainfall samples and integrated dry deposition samples were determined using ion chromatography. In rainfall, the annual volume-weighted mean (VWM) concentrations of SO4 2-, NO3 -, NH4 +, and Ca2+ were 30.1, 28.7, 64.9, and 31.8 μeq L-1, respectively. The annual values of acid-neutralizing capacity and fractional acidity were 37.8 μeq L-1 a nd 0.0035, r espectively, i ndicating t hat S O4 2- a nd NO3 - in the rainfall were fully neutralized by NH4 + and Ca2+, which was supported by the annual rainfall pH of 6.7. The annual wet and dry deposition fluxes were 0.27 and 0.09 keq ha-1 yr-1 for SO4 2- and 0.26 and 0.11 keq ha-1 yr-1 for NO3 -, respectively, resulting in a total acid deposition flux of 0.73 keq ha-1 yr-1, which approximated the maximum critical load of acidity in Sichuan province. The annual wet and dry deposition fluxes were 8.3 and 2.9 kg N ha-1 yr-1 for NH4 +-N and 3.7 and 1.5 kg N ha-1 yr-1 for NO3 --N, respectively, leading to a total nitrogen deposition of 16.4 kg N ha-1 yr-1. Moreover, the annual equivalent ratio of [SO4 2-]/[NO3 -] in rainfall was 1.1, suggesting that the acid deposition in Mianyang was a mixed type caused by sulfuric and nitric acids. The annual mass ratio of NH4 +-N/NO3 --N was 2.3, reflecting the important role of agricultural activities in nitrogen deposition in Mianyang.
eISSN:2083-5906
ISSN:1230-1485
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