Assessment major NOx sources to nitrate of TSP around the Danjiangkou reservoir using isotopes and a Bayesian isotope mixing model

• Published in: Atmospheric pollution research Vol. 15; no. 7; p. 102151
• Main Authors: Xiao, Chunyan, Sun, Yimeng, Zhao, Tongqian, Wang, Guizhen, Li, Pengbo, Zhao, Yawei, Chen, Feihong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2024
• Subjects: Danjiangkou reservoir; Nitrate; Nitrogen and oxygen isotope; PSCF; SIAR; SIAR; Nitrate; PSCF; Danjiangkou reservoir; Nitrogen and oxygen isotope
• ISSN: 1309-1042; 1309-1042
• DOI: 10.1016/j.apr.2024.102151

Nitrate (NO3−) is a key component of atmospheric particulate matter. However, studies quantifying NO3− formation and sources in water source areas remain scarce. This study employs NO3− concentration, dual isotopic analyses (δ15N, δ18O), and SIAR and PSCF models to elucidate NO3− formation mechanisms and apportion sources in the Danjiangkou Reservoir area. The result showed that the concentration of NO3− (0.52 μg m−3-2.39 μg m−3), δ15N–NO3- (−2.3‰-4.2‰) and δ18O–NO3- (64.2‰–96.6‰) values varied seasonally in total suspended particulate matter (TSP). The contribution of the NO2 + ·OH pathway was the highest in summer (84%), while the main contributions came from the N2O5 + H2O and NO3 + VOCs pathways in winter (75%). The SIAR model revealed that the contributions of coal combustion and traffic emissions were 34% and 23%, respectively, indicating that fossil fuel release contributed most. Moreover, the contribution of biomass combustion sources was 31%, and soil emission sources had the least (12%). Considering liquefied petroleum gas, gasoline, and diesel vehicles as traffic emission sources, their contribution to NO3− in TSP increased to 50%. The PSCF analysis indicated that external input areas were predominantly from central Henan Province, northern Hubei Province, and central Shaanxi Province. This study quantitatively analyzed the sources of NO3− in atmospheric particulate matter in water sources for the first time, indicating that controlling the emissions of nitrogen oxides from gasoline cars, heavy-duty diesel trucks, and ships could help alleviate haze pollution and enhance air quality in the Danjiangkou reservoir area. •The δ15N–NO3- and δ18O–NO3- of TSP varied seasonally in the Danjiangkou Reservoir area.•High δ15N values of nitrate in winter indicated a dominant influence of coal combustion on NOx production.•Summer-time low values of δ18O suggestd a formation pathway via OH radical.•Fossil fuel sources were the main contamination sources of NO3− in TSP in the Danjiangkou Reservoir area (57%).