College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
Xizang Agriculture and Animal Husbandry University, Nyingchi, Tibet, 860000, China.
Sci Rep. 2019 Mar 15;9(1):4645. doi: 10.1038/s41598-019-39855-2.
Atmospheric reactive nitrogen (N) deposition has been proven to be an important nutrient input from external environments to forest ecosystems. However, the magnitude of atmospheric N deposition in the Tibetan region of China is not well known. In this study, multi-year (between 2005 and 2016) measurements of dry and wet N deposition were carried out in Nyingchi (NC) city, southeastern Tibet. Bulk deposition was collected by the rain gauge method; dry deposition was calculated by the inferential method, namely, multiplying ambient N concentrations by dry deposition velocity (V) of the N species. During the entire period, annual bulk and dry N deposition fluxes averaged 2.19 and 1.85 kg N ha yr, respectively. Total N deposition fluxes (the sum of reduced and oxidized N species in dry and bulk deposition) showed an obvious increasing trend, especially for oxidized N species. Both bulk and dry N deposition showed a consistent seasonal pattern, with the highest fluxes in summer and the lowest in winter. Our findings suggest that N deposition to the urban environment in southeast Tibet has recently shifted from ammonium-dominated to nitrate-dominated conditions.
大气活性氮（N）沉降已被证明是森林生态系统从外部环境输入的重要养分。然而，中国西藏地区的大气 N 沉降量尚不清楚。本研究对西藏东南部的林芝（NC）市进行了多年（2005 年至 2016 年）干湿 N 沉降的测量。用雨量计法收集总沉降；通过推断法（即通过环境 N 浓度乘以 N 物种的干沉降速度（V））计算干沉降。在整个研究期间，年总沉降和干沉降通量分别平均为 2.19 和 1.85kgNha yr。总 N 沉降通量（干沉降和总沉降中还原和氧化 N 物种的总和）呈明显上升趋势，尤其是氧化 N 物种。总沉降和干沉降均表现出一致的季节性模式，夏季通量最高，冬季最低。我们的研究结果表明，西藏东南部城市环境中的 N 沉降最近已由铵态为主转变为硝态为主。
