[Atmospheric Nitrogen Dioxide, Nitric Acid, Nitrate Nitrogen Concentrations, and Wet and Dry Deposition Rates in a Double Rice Region in Subtropical China].

Nitrogen dioxide (NO) and nitric acid (HNO) are nitrogen-containing acidic gases in the atmosphere, and they are important precursors of nitrate in aerosol and rainwater. The emission intensity of atmospheric nitrogen oxides is high in the subtropical region of China, but the concentrations and deposition rates of atmospheric nitrogen dioxide, nitric acid, particulate nitrate-nitrogen (NO-N), and rainwater nitrate-nitrogen (NO-N) in a double rice region in subtropical China are still unclear,. In this study, the atmosphere concentrations of NO-N, HNO-N, NO-N in PM, and NO-N and related meteorological parameters were simultaneously monitored in a typical double rice region within a subtropical hilly region of China, with the aim of determining the characteristics and influencing factors of NO-N, HNO-N, NO-N, and NO-N concentrations and quantifying the wet and dry deposition rates. The results showed that the annual mean concentrations of NO-N, HNO-N, NO-N, and NO-N were 4.2 μg·m, 0.7 μg·m, 4.0 μg·m, and 1.0 mg·L, respectively, and the deposition rates were 1.5, 3.2, 2.3, and 6.1 kg·hm, respectively. The NO-N concentrations were negatively correlated with air temperatures, and the HNO-N concentrations were negatively correlated with wind speeds. TheNO-N concentrations were negatively correlated with air temperatures, positively correlated with NO-N concentrations, but not significantly correlated with HNO-N concentrations, thus indicating that NO-N concentrations were an important limiting factor forNO-N pollution in this study area. The NO-N concentrations were negatively correlated with rainfall, as well as the concentrations of HNO-N and NO-N. The annual total dry and wet depositions of the atmospheric NO-N, HNO-N, NO-N, and NO-N were 13.0 kg·hm, which indicates that these compounds are important sources of nitrogen in paddy fields and may have significant impacts on paddy fields and surrounding ecosystems.