三峡库区澎溪河流域氮湿沉特征及其来源

本研究收集了澎溪河流域及万州城区共6个站点2016年1~12月大气湿沉降样品，分析了澎溪河流域大气湿沉降氮的时空变化特征、来源及其对流域水体的输入贡献.澎溪河流域氮湿沉降空间上差异较小，呈现区域性特征；季节上差异较大，呈现春夏大于秋冬的特点.总氮沉降（TDN）浓度和通量分别为1.1mg N/L和11.8kg N/（hm²·a）.来源主要包括二次源、地壳源、交通源和养殖源，其贡献占比分别为47.4%、23.5%、14.3%和10.9%，而工业源和化石燃料燃烧源仅分别贡献2.8%和1.1%.通过湿沉降直接输入流域水体的氮素为76.9t/a，约占总氮输入的1.8%；沉降通量超过了水体富营养化临界负荷.流域湿沉降铵态氮（NH₄⁺-N）、硝酸盐氮（NO₃^--N）和有机氮（DON）沉降通量分别占总沉降的63.3%、25.9%和10.7%，减少NH₄⁺-N排放能有效控制流域氮沉降量.

Characteristics and sources of wet deposition of nitrogen in the Pengxi River Basin of the Three Gorges Reservoir Area

From January to December 2016, atmospheric wet deposition samples were collected at six sampling sites, among which five sites were located in the Pengxi River Basin and the other was in the urban area of Wanzhou. The spatio-temporal variation and sources of the atmospheric wet deposition of nitrogen were analyzed, and its contribution to nitrogen in water bodies in the basin were estimated. The spatial variations of nitrogen wet deposition in Pengxi River Basin was insignificant, i.e., an even distribution in general in the region. On the other hand, the seasonal difference was substantial, with larger deposition in spring and summer. The averaged concentration in deposition samples and the depositional flux of total dissolved nitrogen (TDN) were 1.1mg N/L and 11.8kg N/(hm²·a), respectively. The nitrogen in wet deposition was mainly originated from secondary sources, crustal, transportation, and aquaculture, accounting for 47.4%, 23.5%, 14.3%, 10.9%, respectively. The contribution from industry and fossil fuel combustion was only 2.8%, and 1.1%, respectively. The nitrogen transported directly into the water body via wet deposition was 76.9 tons per year in the study area, accounting for 1.8% of total input. This depositional flux of nitrogen exceeded the critical load of eutrophication. The ammonium (NH₄⁺-N), nitrate (NO₃^--N), and dissolved organic nitrogen (DON) accounted for 63.3%, 25.9%, and 10.7% in nitrogen depositional fluxes in the basin, respectively. Therefore, it was critical to reduce ammonia emission in the region for the effective control of nitrogen deposition in Pengxi River Basin.