中文摘要：

Due to increasing global demand for crop production and energy use, more and more reactive nitrogen（Nr） has been generated and emitted to the environment. As a result, global atmospheric nitrogen（N） deposition has tripled since the industrial revolution and the ecological environment and human health have been harmed. In this study, we measured dry and wet/bulk N deposition from July 2013 to December 2015 in a semi-arid grassland of Duolun County, Inner Mongolia, China. The samples of dry and wet/bulk N deposition were collected monthly with a DELTA（DEnuder for Long Term Atmospheric sampling） system and with Gradko passive samplers and a precipitation gauge. The measured results show that the annual mean concentrations of NH3, NO2, HNO3, particulate NH4+（pNH4+） and particulate NO3-（pNO3-） in atmosphere were 2.33, 1.90, 0.18, 1.42 and 0.42 μg N/m3, respectively, and that the annual mean volume-weighted concentrations of NH4+-N and NO3--N in precipitation were 2.71 and 1.99 mg N/L, respectively. The concentrations of Nr components（including NH3, NO2, HNO3, p NH4+, pNO3-, NH4+-N and NO3--N） exhibited different seasonal variations. Specifically, NO2 and HNO3 exhibited higher concentrations in autumn than in summer, while the other Nr components（NH3, pNH4+, pNO3-, NH4+-N and NO3--N） showed the highest values in summer. Based on measured concentrations of Nr components and their deposition velocities estimated using the GEOS-Chem global atmospheric chemical transport model, the calculated annual mean dry deposition fluxes were 3.17, 1.13, 0.63, 0.91 and 0.36 kg N/（hm2·a） for NH3, NO2, HNO3, p NH4+ and pNO3-, respectively, and the calculated annual mean wet/bulk deposition fluxes were 5.37 and 3.15 kg N/（hm2·a） for NH4+-N and NO3--N, respectively. The estimated annual N deposition（including dry N deposition and wet/bulk N deposition） reached 14.7 kg N/（hm2·a） in grassland of Duolun County, approaching to the upper limit of the N critical load（10–15 kg N/（hm2·a））

英文摘要：

Due to increasing global demand for crop production and energy use, more and more reactive nitrogen (Nr) has been generated and emitted to the environment. As a result, global atmospheric nitrogen (N) deposition has tripled since the industrial revolution and the ecological environment and human health have been harmed. In this study, we measured dry and wet/bulk N deposition from July 2013 to December 2015 in a semi-arid grassland of Duolun County, Inner Mongolia, China. The samples of dry and wet/bulk N deposition were collected monthly with a DELTA (DEnuder for Long Term Atmospheric sampling) system and with Gradko passive samplers and a precipitation gauge. The measured results show that the annual mean concentrations of NH₃, NO₂, HNO₃, particulate NH₄ ⁺ (pNH₄ ⁺) and particulate NO₃ ^? (pNO₃ ^?) in atmosphere were 2.33, 1.90, 0.18, 1.42 and 0.42 μg N/m³, respectively, and that the annual mean volume-weighted concentrations ofNH₄ ⁺-N and NO₃ ^?-N in precipitation were 2.71 and 1.99 mg N/L, respectively. The concentrations of Nr components (including NH₃, NO₂, HNO₃, pNH₄ ⁺, pNO₃ ^?,NH₄ ⁺-N and NO₃ ^?-N) exhibited different seasonal variations. Specifically, NO₂ and HNO₃ exhibited higher concentrations in autumn than in summer, while the other Nr components (NH₃, pNH₄ ⁺, pNO₃ ^?,NH₄ ⁺-N and NO₃ ^?-N) showed the highest values in summer. Based on measured concentrations of Nr components and their deposition velocities estimated using the GEOS-Chem global atmospheric chemical transport model, the calculated annual mean dry deposition fluxes were 3.17, 1.13, 0.63, 0.91 and 0.36 kg N/(hm²