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| Sediments phosphorus forms and loading in the lakes of the mid-lower reaches of the Yangtze River and Yunnan Plateau, China |
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Abstract Differences of phosphorus forms in lake sediments and its flux across the sediment-water interface (SWI Pflux) between lakes located in the Middle and Lower Yangtze River drainage basin (MLYR) and those in the Yunnan Plateau (YN) were determined. The average ω(TP) in YN was (1256±621) mg/kg, which was higher than that in MLYR [(601±76)mg/kg]. Soil erosion resulted in the higher content of calcium bound phosphorus (HCl-P) in the sediments of YN, and the high salinity of their lake water were conductive to phosphorus burial. High organic matter content in sediments also inhibited the migration of phosphorus in lakes of YN, and the SWI Pflux was 0.17~1.07mg/(m2·d). However, in MLYR phosphorus forms were closely related to non-point source nutrient pollution and phytoplankton bloom, and redox sensitive phosphorus (BD-P) accounted for the majority of TP. The potential mobile phosphorus (the sum of loosely adsorbed P, BD-P, NaOH bound P) accounted for 60.60% of TP, which was around 2 times of that in YN, and its SWI Pflux was 0.002~1.32mg/(m2·d). Thus, measures including reducing agricultural nonpoint source pollution, maintaining and recovering macrophytes in lakes should be taken to improve water quality in MLYR. However, preventing the soil erosion, and implementing the best nutrient management practices are more important in the watershed of YN.
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Received: 30 October 2014
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