title: Historical and seasonal dynamics of phosphorus mobility in Sancha Lake of Southwest China's Sichuan Province.
abstract: Phosphorus (P) fractionations in the surface sediment of Sancha Lake in China's southwestern Sichuan Province were examined to assess the potential P release at the water-sediment interface and to understand its seasonal (2009-2010) and historical dynamics (1989-2010) in the surface water. Elevated P concentrations were detected in the sediment at main reservoir inflow, south canal of the Dujiangyan irrigation network, and intensive cage fish farming area, accounting for 32 and 40% of current total P discharges. The highest total P concentration (11,200 μg P g-1) was observed in the upper sediment below intensive fish farming area with a specific enrichment of HCl-P (51% of total P) mainly from fish feeds and feces. These sediments had larger MgCl2-P pools with higher diffusive P fluxes (0.43-0.47 mg m-2d-1) from surface sediment than those from other areas (0.25-0.42 mg m-2d-1). The general small proportion of MgCl2-P (5.7-10%) and low diffusive P fluxes from surface sediment (<0.02% of sediment P storage (0-1 cm)) indicate low mobility and slow release of P from sediments. The sediment as an internal P source led to a 3-4-year lag for P concentration decrease in the surface water after restriction of anthropogenic P discharges since 2005. Thus, the peak P concentration in April and September could be explained as a combined effect of supplementing internal loading via reductive processes in sediments and seasonal water vertical circulation in the early spring and fall. Policy played a crucial role in reducing P inputs to the lake.
authors.affiliation: Chengdu Academy of Environmental Sciences, Environmental Protection Building, No.8 Fanglin Road, Chengdu, Sichuan, 610072, People's Republic of China.
authors.forename: Binyang
authors.initials: B
authors.lastname: Jia
authors.affiliation: Department of Environment, College of Architecture and Environment, Sichuan University, No 24, South Section One, First Ring Road, Chengdu, Sichuan, 610065, People's Republic of China. tangya@scu.edu.cn.
authors.forename: Ya
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Chengdu Center, China Geological Survey, No 2, North Section Three, First Ring Road, Chengdu, Sichuan, 610081, People's Republic of China.
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.affiliation: Department of Environmental Geosciences, University of Basel, CH-4056, Basel, Switzerland.
authors.forename: Jen-How
authors.initials: JH
authors.lastname: Huang
mesh_terms: D000818:Animals; D002681:China; D004784:Environmental Monitoring / Q000379:methods*; D005399:Fishes; D019015:Geologic Sediments / Q000032:analysis*; D060106:Lakes; D010758:Phosphorus / Q000032:analysis*; D012621:Seasons; D014867:Water; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D014874:Water Pollutants, Chemical; D014867:Water; D010758:Phosphorus
keywords: Aquatic ecosystem; Environmental protection; Eutrophication; Reservoir; Sediment; Socio-economic development