title: Reconstructing historical changes in phosphorus inputs to rivers from point and nonpoint sources in a rapidly developing watershed in eastern China, 1980-2010.
abstract: Quantifying point (PS) and nonpoint source (NPS) phosphorus inputs to rivers is critical for developing effective watershed remediation strategies. This study reconstructed PS and NPS total phosphorus (TP) inputs to the Yongan River in eastern China in 1980-2010 using a load apportionment model (LAM) from paired riverine TP concentrations and river discharge records. Based on the fundamental hydrological differences between PS and NPS pollution, the LAM statistically quantified their individual inputs as a power-law function of river discharge. The LAM-estimated monthly/annual riverine TP loads were in good agreement with results derived from a regression model, Load Estimator (LOADEST). The annual TP load increased from 18.4 to 357.0 Mg yr(-1) between 1980 and 2010. The PS input contributed 7-45% of annual total TP load and increased 23-fold, consistent with a 20-fold increase in flow-adjusted average chloride concentration during the low flow regime (a proxy for wastewater inputs), as well as measured increases in population, poultry, and industrial production. Inferring from observed TP and chloride ratios, as well as total suspended solids (TSS) and river discharge dynamics, temporally retained P load within the river during the low flow regime was estimated to contribute 18-65% of the annual PS input load. NPS inputs consistently dominated the annual riverine TP load (55-93%) and increased 19-fold, consistent with the strong correlation between riverine TP and TSS concentrations, increasing developed land area, improved agricultural drainage systems, and phosphorus accumulation in agricultural soils. Based on our analysis, TP pollution control strategies should be preferentially directed at reductions in NPS loads, especially during summer high-flow periods when the greatest eutrophication risk occurs.
authors.affiliation: College of Environmental & Resource Sciences, Zhejiang University, Hangzhou 310058, China; Department of Land, Air, and Water Resources, University of California, Davis, CA 95616 USA. Electronic address: chendj@zju.edu.cn.
authors.forename: Dingjiang
authors.initials: D
authors.lastname: Chen
authors.affiliation: College of Environmental & Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition, Zhejiang University, Hangzhou 310058, China.
authors.forename: Minping
authors.initials: M
authors.lastname: Hu
authors.affiliation: College of Environmental & Resource Sciences, Zhejiang University, Hangzhou 310058, China; Ministry of Education Key Laboratory of Environment Remediation and Ecological Health, Zhejiang University, Hangzhou 310058, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Land, Air, and Water Resources, University of California, Davis, CA 95616 USA.
authors.forename: Randy A
authors.initials: RA
authors.lastname: Dahlgren
mesh_terms: D000383:Agriculture; D002681:China; D004784:Environmental Monitoring; D015233:Models, Statistical; D010758:Phosphorus / Q000032:analysis*; D045483:Rivers / Q000737:chemistry*; D014506:Urban Renewal; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data*
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus
keywords: Agriculture; Diffuse (nonpoint) source; Eutrophication; Load apportionment model; Nutrient; Point source; Sewage