Accumulation Characteristics Of Phosphorus In Lake Sediments And Their Responses To Human Activities

With the intensification of human activities, water quality worsening, as a collection of lake sediment pollutants, indicating the effect of human activities in the river basin. The selection of phosphorus in the sediment as the research object, research on human activity accumulation and basin effects on different areas, different depth and different lake sediment phosphorus.Taking Poyang Lake as an example, study the influence of the river lake relation changes caused by human activities of different forms of phosphorus in the sediments of lake, The total phosphorous(TP) and various forms of phosphorus contents characteristics of Poyang Lake surface exposed sediments were studied, in order to reveal the influence of the water level descended resulted from the relationship between Yangtze River and the Poyang Lake changed on the potential phosphorus-release risk of Poyang Lake sediments. Results showed that: The TP contents of Poyang Lake surface sediments varied from 214.5 to 736.0mg/kg, and the average content of TP was(428.6±154.3)mg/kg, The TP contents in the estuary of “five rivers” and central area of Poyang Lake were closed, were 444.5mg/kg and 445.4mg/kg, the content in the north area was 387.7mg/kg which far less than the estuary of “five rivers” and central area of Poyang Lake. The spatial distribution of various forms of phosphorus of Poyang Lake surface sediments was relatively uniform, the average content of reactive phosphorous from Poyang Lake surface sediments was(254.6±114.3)mg/kg, non-reactive phosphorus was(69.1±26.3)mg/kg, and organic phosphorus was(105.0±49.2)mg/kg, their contents relationship was the reactive phosphorous>organic phosphorus>non-reactive phosphorus. The relationship between Yangtze River and the Poyang Lake changed, resulting in the low water level advanced and the outcropped time prolonged, then caused the TP and various forms of phosphorus contents increased with the elevation rise from 10~11m to 12~13m, and the growth rate of the reactive phosphorous was faster than organic phosphorus and non-reactive phosphorus. The growth in the estuary of “five rivers” was the most significant, the central area comes second, and the north area was the least.The relationship between the characteristics of organic phosphorus(OP) accumulation, its bioavailability and watershed development were investigated selecting four representative columnar sediments in Poyang Lake using the modified Hedley sequential extraction methods and enzymatic hydrolysis technique. Results showed that: the OP contents in sediments from four sites of Poyang Lake were all increasing continuously with time since 1972, and the value of the south area and estuary of ‘five rivers’ had the trends of increasing faster than that of the north and central area; The contents of H2O-Po and HCl-Po in sediments were decreasing with time, but increasing in near decade; NaOH-EDTA-Po contents in sediments were increasing continuously with time, which means that NaOH-EDTA-Po was the main source of the OP in sediments of Poyang Lake increased continuously with time. The characteristics of OP form in sediments of Poyang Lake were different, H2O-Po mainly consisted by phytate-like P, both content and bioavailability were in low level; NaOH-EDTA-Po content and bioavailability are higher than H2O-Po, the labile monoester P was the major component. The increase of OP in Poyang Lake sediments mainly caused by the labile monoester P, the trend of bioavailability also was increasing continuously with time, the diester P and phytate-like P were decreasing from 1972 to 2002, but increasing since 2002. The characteristics of OP accumulation in sediments of Poyang Lake, especially the NaOH-EDTA-Po were effected by agricultural non-point source pollution, The OP and NaOH-EDTA-Po contents were positively correlated with phosphate fertilizer consumption per hectare in watershed of Poyang Lake, which showed that agricultural non-point source pollution was an important cause for the OP content increasing in Poyang Lake sediments.In the social and economic development level differences, the different human activities within the basin of lake pollution degree and stage. This paper selects the eastern plain area and the Yungui Plateau Lake as the research object, on the eastern plain area Taihu, Poyang Lake, East Lake, Yungui Plateau Lakes in Dianchi, Erhai, Lugu Lake and the bioavailability of phosphorus forms in the sediments of the characteristics, to explore the influence of human activity difference. The results show that the eastern plain and the Yungui Plateau Lake Sediment extractable TP in the range of 195.6mg/kg to 1502.0mg/kg, including H2O-Pt 0.05%-1.34%, HCl-Pt 10.9%-73.9%, NaOH-EDTA-Pt 25.1%-88.7%. The lake sediment extractable TP size: Dianchi<Poyang Lake<Lugu Lake<Erhai Taihu<East Lake. The IP content in the range of 176.68mg/kg to 1432.57mg/kg, TP 61.24%-101.76%. The relationship between the size of Dianchi Lake< Poyang Lake<Taihu<Lugu Lake<Erhai< East Lake. The content of OP is in the range of 8.67mg/kg to 165.76 mg/kg, accounting for TP of 3.22%-38.76%. The relationship between Taihu<Poyang Lake<Erhai<East Lake<Dianchi<Lugu Lake. Urban lakes extractable TP content was the highest, poor water quality of lake sediments with high content of HCl-Pi, The eastern plains lakes sediments OP in addition to single lipid phosphorus in NaOH-EDTA-Po must be less than the outside of the Yungui Plateau lakes.