College of Resources and Environmental Sciences, Beijing Key Laboratory of Cropland Pollution Control and Remediation, China Agricultural University, Beijing 100193, China; State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Laboratory for Climate and Ocean-Atmosphere Sciences, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China.
Environ Pollut. 2018 Jan;232:546-555. doi: 10.1016/j.envpol.2017.09.086. Epub 2017 Oct 6.
The Yangtze River basin is one of the world's hotspots for nitrogen (N) deposition and likely plays an important role in China's riverine N output. Here we constructed a basin-scale total dissolved inorganic N (DIN) deposition (bulk plus dry) pattern based on published data at 100 observational sites between 2000 and 2014, and assessed the relative contributions of different reactive N (N) emission sectors to total DIN deposition using the GEOS-Chem model. Our results show a significant spatial variation in total DIN deposition across the Yangtze River basin (33.2 kg N ha yr on average), with the highest fluxes occurring mainly in the central basin (e.g., Sichuan, Hubei and Hunan provinces, and Chongqing municipality). This indicates that controlling N deposition should build on mitigation strategies according to local conditions, namely, implementation of stricter control of N emissions in N deposition hotspots but moderate control in the areas with low N deposition levels. Total DIN deposition in approximately 82% of the basin area exceeded the critical load of N deposition for semi-natural ecosystems along the basin. On the basin scale, the dominant source of DIN deposition is fertilizer use (40%) relative to livestock (11%), industry (13%), power plant (9%), transportation (9%), and others (18%, which is the sum of contributions from human waste, residential activities, soil, lighting and biomass burning), suggesting that reducing NH emissions from improper fertilizer (including chemical and organic fertilizer) application should be a priority in curbing N deposition. This, together with distinct spatial variations in emission sector contributions to total DIN deposition also suggest that, in addition to fertilizer, major emission sectors in different regions of the basin should be considered when developing synergistic control measures.
长江流域是全球氮(N)沉降热点地区之一,可能在中国河流 N 输出方面发挥着重要作用。本研究基于 2000 年至 2014 年期间 100 个观测站点的已有发表数据,构建了流域尺度的总溶解无机氮(DIN)沉降(包括干沉降和湿沉降)格局,并利用 GEOS-Chem 模型评估了不同活性 N (N)排放源对总 DIN 沉降的相对贡献。结果表明,长江流域 DIN 总沉降存在显著的空间变异性(平均为 33.2 kg N ha yr),最高通量主要出现在流域中部(如四川、湖北和湖南以及重庆直辖市)。这表明,控制 N 沉降应该根据当地情况制定减排策略,即在 N 沉降热点地区实施更严格的 N 排放控制,而在 N 沉降水平较低的地区则实施适度控制。流域约 82%的区域 DIN 总沉降超过了沿流域半自然生态系统的 N 沉降临界负荷。在流域尺度上,DIN 沉降的主要来源是化肥使用(40%),其次是畜牧业(11%)、工业(13%)、电厂(9%)、交通(9%)和其他(18%,包括人类粪便、居民活动、土壤、照明和生物质燃烧的贡献总和),这表明减少不当施肥(包括化肥和有机肥)导致的 NH 排放应成为抑制 N 沉降的优先事项。此外,排放源对总 DIN 沉降的贡献存在明显的空间变化,这也表明,在制定协同控制措施时,除了化肥,还应考虑流域不同区域的主要排放源。