Institute of New Energy and Low-Carbon Technology & Healthy Food Evaluation Research Center, Sichuan University, Chengdu 610065, China.
Department of Environment, College of Architecture and Environment, Sichuan University, Chengdu 610065, China; State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China.
Sci Total Environ. 2020 Apr 15;713:136676. doi: 10.1016/j.scitotenv.2020.136676. Epub 2020 Jan 13.
The West China Rain Zone (WCRZ) is of ecological importance and thus, anthropogenic impacts on its vitality are of concern. To ascertain if China's SO and NO emissions reductions in the recent years are reflected in reduced impacts, sulfur and nitrogen wet deposition at Mt. Emei was observed during 2017-2019. The source contributions to sulfur and nitrogen wet deposition were estimated using the positive matrix factorization (PMF) and the source-oriented Community Multi-scale Air Quality (CMAQ) model. The annual Volume Weighted Mean (VWM) pH of precipitation increased from 4.01 to 4.75 in the 1980s-2000s to 5.39 in 2017-2019. However, 12% of the samples during 2017-2019 had pH < 4.50. The VWM SO concentration decreased from 80.9 to 26.0 μeq L from 2007-2009 to 2017-2019. The VWM NO concentration (18.3 μeq L) in 2017-2019 was close to that measured in 2007-2009. Although the dry deposition fluxes onto forest canopy were under-estimated, the mean annual total wet and dry deposition flux of nitrogen (24.3 kg N ha yr) was higher than the critical load (CL: 10.0-15.0 kg N ha yr), while the flux of sulfur (12.1 kg S ha yr) was lower than the CL (16.0-32.0 kg S ha yr). The annual wet deposition fluxes of SO and NO were mainly from industries (54% and 43%, respectively) and power plants (21% and 25%, respectively), and that of NH was mostly from agriculture (88%). Emissions within and outside the Sichuan Basin (SCB) were both important sources of the wet deposition fluxes of sulfur (45% and 39%, respectively) and nitrogen (68% and 29%, respectively), and other unidentified sources accounted for 16% and 3% of the sulfur and nitrogen fluxes, respectively. This study suggests that to protect Mt. Emei's ecosystems, efforts are needed to further control sulfur and nitrogen deposition through reducing emissions within and outside the SCB.
华西雨带（WCRZ）具有重要的生态意义，因此，人为活动对其活力的影响引起了关注。为了确定近年来中国 SO 和 NO 排放量的减少是否反映在减少的影响中，我们在 2017-2019 年期间对峨眉山的硫和氮湿沉降进行了观测。利用正定矩阵因子分解（PMF）和面向源的社区多尺度空气质量（CMAQ）模型，估算了硫和氮湿沉降的来源贡献。降水的年体积加权均值（VWM）pH 值从 20 世纪 80 年代至 2000 年代的 4.01 增加到 4.75，然后在 2017-2019 年增加到 5.39。然而，在 2017-2019 年，12%的样本 pH 值<4.50。2007-2009 年至 2017-2019 年，SO 浓度的 VWM 从 80.9 降至 26.0 μeq L。2017-2019 年的 VWM NO 浓度（18.3 μeq L）与 2007-2009 年的测量值相近。尽管对森林冠层的干沉降通量估计不足，但氮的年总湿和干沉降通量（24.3 kg N ha yr）高于临界负荷（CL：10.0-15.0 kg N ha yr），而硫的通量（12.1 kg S ha yr）低于 CL（16.0-32.0 kg S ha yr）。SO 和 NO 的年湿沉降通量主要来自工业（分别为 54%和 43%）和电厂（分别为 21%和 25%），而 NH 的湿沉降通量主要来自农业（88%）。四川盆地内（SCB）和盆地外的排放源对硫（分别为 45%和 39%）和氮（分别为 68%和 29%）的湿沉降通量都很重要，其他未确定的来源分别占硫和氮通量的 16%和 3%。本研究表明，为了保护峨眉山的生态系统，需要通过减少 SCB 内和外的排放来进一步控制硫和氮的沉积。
