title: Long-term variation (1960-2003) and causal factors of non-point-source nitrogen and phosphorus in the upper reach of the Yangtze River.
abstract: The knowledge of long-term variation and causal factors of non-point source (NPS) pollution in large-scale watersheds is helpful in the development of water quality control programs. In this study, the Improved Export Coefficient Model and the Revised Universal Soil Loss Equation were combined to estimate the temporal and spatial variations (1960-2003) of NPS pollution in the upper reach of the Yangtze River (URYR). Two change points for NPS pollution were successfully detected. In the URYR, the dissolved nitrogen (DN) and dissolved phosphorus (DP) increased before 2000 and decreased after 2000, whereas the inflection points from increase to decline were around 1980 for the adsorbed N (AN) and adsorbed P (AP). The results also indicated that the dissolved pollutants were mainly contributed by the anthropogenic factors, while the adsorbed pollutants were primarily exported by the natural factors. By comparing the load intensities from each source, it revealed that for the dissolved pollutants, the major source of the high load intensity transferred from urban land to dry land after 1980. Simultaneously, the high load intensity areas of the adsorbed pollutants transferred from forest to orchard around 1980, which was mainly attributed to the increasing fertilizer application. These results may be useful for planning and management of the URYR and other large-scale watersheds.
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, No 19 Xinjiekouwai Street, Haidian District, Beijing 100875, PR China. zyshen@bnu.edu.cn
authors.forename: Zhenyao
authors.initials: Z
authors.lastname: Shen
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Ding
authors.forename: Qian
authors.initials: Q
authors.lastname: Hong
authors.forename: Ruimin
authors.initials: R
authors.lastname: Liu
mesh_terms: D000327:Adsorption; D002681:China; D004784:Environmental Monitoring; D005308:Fertilizers; D049673:History, 20th Century; D049674:History, 21st Century; D008962:Models, Theoretical; D009584:Nitrogen / Q000032:analysis* / Q000266:history; D010758:Phosphorus / Q000032:analysis* / Q000266:history; D045483:Rivers; D012987:Soil / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000266:history
chemical_list: D005308:Fertilizers; D012987:Soil; D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen