中国农业大学教授刘学军、张福锁等通过研究，系统揭示了过去30年（1980～2010）来我国氮沉降动态及其与人为活性氮排放的关系。相关成果日前在线发表于英国《自然》（Nature）杂志。
      氮素沉降是指大气中活性氮化合物通过降雨、降尘等途径降落到地表的过程。农田施肥不合理、养殖场畜禽粪便管理不佳、燃煤、汽车尾气排放等，都会增加人为活性氮向大气的排放。这些气体及通过次生反应形成的气溶胶/细颗粒物（如PM2.5），会导致空气质量下降或大气污染。同时，从大气沉降到陆地和水生态系统的活性氮数量和形态，也影响着生态系统的功能及稳定性。
      目前，我国在区域大尺度上开展人为活性氮排放与沉降的长期系统研究还非常有限，缺乏氮素沉降动态、效应及其与人为活性氮排放关系的直接证据。
      该研究小组从上世纪90年代后期开始启动大气氮素沉降研究，构建了中国氮素沉降通量及相关参数的大样本数据库。研究发现，目前我国人口相对密集和农业集约化程度更高的中东部地区（尤其是华北平原），其氮素沉降量已高于北美任何地区，与西欧上世纪80年代氮沉降高峰时的数量相当。
      研究还表明，中国氮素沉降的增加，主要受氮肥、畜牧业等农业源和工业、交通源等非农业源活性氮排放的影响。主要来自农业源氨排放的铵态氮沉降是氮素沉降的主体，占总沉降量的2/3左右。以来自非农业源（燃煤和汽车尾气等化石能源燃烧）氮氧化物排放为主的硝态氮沉降，约占总沉降量的1/3，而该占比在上世纪80年代为1/6，说明来自非农业源的排放增速更快。
      该研究提示，实现氮肥和畜牧业等农业源氨的减排，是当前中国控制氮素沉降的主要立足点。同时，大幅减少各种化石能源等非农业源活性氮的排放，已越来越迫切。（来源：中国科学报 钟华）

Enhanced nitrogen deposition over China

China is experiencing intense air pollution caused in large part by anthropogenic emissions of reactive nitrogen1, 2. These emissions result in the deposition of atmospheric nitrogen (N) in terrestrial and aquatic ecosystems, with implications for human and ecosystem health, greenhouse gas balances and biological diversity1, 3, 4, 5. However, information on the magnitude and environmental impact of N deposition in China is limited. Here we use nationwide data sets on bulk N deposition, plant foliar N and crop N uptake (from long-term unfertilized soils) to evaluate N deposition dynamics and their effect on ecosystems across China between 1980 and 2010. We find that the average annual bulk deposition of N increased by approximately 8 kilograms of nitrogen per hectare (P < 0.001) between the 1980s (13.2 kilograms of nitrogen per hectare) and the 2000s (21.1 kilograms of nitrogen per hectare). Nitrogen deposition rates in the industrialized and agriculturally intensified regions of China are as high as the peak levels of deposition in northwestern Europe in the 1980s6, before the introduction of mitigation measures7, 8. Nitrogen from ammonium (NH4+) is the dominant form of N in bulk deposition, but the rate of increase is largest for deposition of N from nitrate (NO3−), in agreement with decreased ratios of NH3 to NOx emissions since 1980. We also find that the impact of N deposition on Chinese ecosystems includes significantly increased plant foliar N concentrations in natural and semi-natural (that is, non-agricultural) ecosystems and increased crop N uptake from long-term-unfertilized croplands. China and other economies are facing a continuing challenge to reduce emissions of reactive nitrogen, N deposition and their negative effects on human health and the environment.

作 者： Xuejun Liu, Ying Zhang, Wenxuan Han, Aohan Tang, Jianlin Shen, Zhenling Cui, Peter Vitousek, Jan Willem Erisman, Keith Goulding,Peter Christie,Andreas Fangmeier & Fusuo Zhang
期刊名称： Science
期卷页： 20 February 2013
原文链接：http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11917.html