title: Enhanced nitrogen deposition over China.
abstract: China is experiencing intense air pollution caused in large part by anthropogenic emissions of reactive nitrogen. 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 diversity. 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 1980s, before the introduction of mitigation measures. 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.
authors: College of Resources & Environmental Sciences, China Agricultural University, Beijing 100193, China.
authors: Xuejun
authors: X
authors: Liu
authors: Ying
authors: Y
authors: Zhang
authors: Wenxuan
authors: W
authors: Han
authors: Aohan
authors: A
authors: Tang
authors: Jianlin
authors: J
authors: Shen
authors: Zhenling
authors: Z
authors: Cui
authors: Peter
authors: P
authors: Vitousek
authors: Jan Willem
authors: JW
authors: Erisman
authors: Keith
authors: K
authors: Goulding
authors: Peter
authors: P
authors: Christie
authors: Andreas
authors: A
authors: Fangmeier
authors: Fusuo
authors: F
authors: Zhang
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000378:metabolism / Q000600:supply & distribution; D000397:Air Pollution / Q000032:analysis* / Q000706:statistics & numerical data; D000818:Animals; D002681:China; D017753:Ecosystem; D004784:Environmental Monitoring / Q000706:statistics & numerical data*; D017752:Greenhouse Effect; D006802:Human Activities; D006801:Humans; D009566:Nitrates / Q000032:analysis / Q000378:metabolism; D009584:Nitrogen / Q000032:analysis* / Q000378:metabolism; D010944:Plants / Q000737:chemistry / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000032:analysis / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D009584:Nitrogen