三峡库区大气活性氮组成及干沉降通量

为了解三峡库区腹地大气中活性氮的组成及干沉降通量，于2015年每个季节选取代表性月份在万州城区采集了气体和颗粒物样品.利用离子色谱法测定氮素浓度，同时结合大叶阻力模型模拟计算的干沉降速率值，估算了不同形态氮素的干沉降通量.结果表明，HNO₃的干沉降速率值最大，年均值为0.39cm/s，约为其它氮素的3~8倍.NO₂和NH₃是大气活性氮的主要赋存形态，年均浓度值分别为（11.7±3.9）和（11.0±5.3）μg N/m³，两者之和约占总无机氮浓度的80%.万州城区总无机氮干沉降总量为8.5kg N/（hm²·a），其中氧化态氮（NO₂、HNO₃、颗粒态NO₃^-）和还原态氮（NH₃、颗粒态NH₄⁺）干沉降通量分别为3.5，5.0kg N/（hm²·a），占干沉降总量的41.4%和58.6%.因此，为有效控制三峡库区腹地的氮素污染，应重点关注NH₃的减排.

Characteristics of chemical components and dry deposition of reactive nitrogen in the Three Gorges Reservoir Region

To understand the chemical components of reactive nitrogen and estimate their dry deposition flux in the Three Gorges Reservoir Region, gaseous and particulate nitrogen species were collected at urban Wanzhou in each season in 2015. Dry deposition flux was estimated using the inferential method with modelled dry deposition velocities and measured ambient concentrations, which was obtained from the big-leaf resistance model and ion chromatography, respectively. HNO₃ had the highest dry deposition velocity among all the reactive nitrogen species, with an annual mean value of 0.39cm/s, which was around 3~8 times higher than other nitrogen species. NO₂ and NH₃ were both important nitrogen forms, with an annual mean concentration of (11.7±3.9) and (11.0±5.3) μg N/m³, respectively, and together contributing around 80% of the total inorganic nitrogen concentrations. Furthermore, the dry deposition fluxes of oxidized nitrogen (NO₂, HNO₃ and particulate NO₃^-) and reduced nitrogen (NH₃ and particulate NH₄⁺) were 3.5 and 5.0kg N/(hm²·a), accounting for 41.4% and 58.6% of the total inorganic nitrogen dry deposition flux, respectively. Therefore, in order to reduce the nitrogen pollution efficiently in the Three Gorges Reservoir Region, it is key to control NH₃ emission.