[Atmospheric Ammonia/Ammonium-nitrogen Concentrations and Wet and Dry Deposition Rates in a Double Rice Region in Subtropical China]

Ammonia (NH) is the most abundant alkaline gas in the ambient air, and it is also one of the important precursors for the ammonium salts in aerosol and rainwater. Though the emission intensities of NH and acidic gases are high, the concentrations and deposition rates of atmospheric ammonia-nitrogen (NH-N), particulate ammonium-nitrogen (NH-N) and rainwater ammonium-nitrogen (NH-N) in double rice regions in subtropical China are still less known. In this study, atmospheric concentrations of NH-N, NH-N in PM and NH-N and related meteorological parameters were observed simultaneously in a typical double rice region in the subtropical hilly region of China, with the aim to clarify the characteristics and influencing factors of atmospheric NH/NH-N concentrations and to quantify the wet and dry deposition rates of atmospheric NH/NH-N. The results showed that the annual mean concentrations of nitrogen in NH-N, NH-N and NH-N were 5.7 μg·m, 12.8 μg·m and 0.8 mg·L, respectively, and their deposition rates were 8.38, 5.61 and 9.07 kg·(hm·a), respectively. The NH-N concentration was significantly increased after application of nitrogen fertilizer in the paddy field, and had a significant positive correlation with the air temperature. The NH-N concentration did not show significant correlation with NH-N concentration, indicating that atmospheric NH-N concentration was not the main limiting factor for the NH-N pollution in the studied region. The NH-N concentration was positively correlated with the NH-N concentration but negatively correlated with precipitation. The high concentrations and deposition rates of atmospheric NH-N/NH-N in the studied region indicated that the atmospheric NH/NH-N pollution was serious, and atmospheric deposition of NH/NH-N was an important nitrogen source in paddy fields, which should be considered in cropland nitrogen nutrient management.