CONTAMINATION ASSESSMENT AND POTENTIAL MOBILITY OF SEDIMENT PHOSPHORUS FROM DIANCHI LAKE, CHINA

Dianchi Lake has been hyper-eutrophicated in the last decades, which is caused directly by the phosphorus loading. In order to understand the relationship between sediment phosphorus and eutrophication in the lake, we investigated the water and sediment samples in twelve cores, and evaluated the phosphorus release potential of five phosphorus fractions with a sequential extraction scheme. The results suggested that total sediment phosphorus in Dianchi Lake varied greatly. The concentration tended to decrease from north to south cores in horizontal and with the depth in vertical. The maximum concentration of total phosphorus was 4.15 mg/g dry weight, and was observed in the upper 5 cm of site S1. For sediment fractions of Dianchi Lake, metallic oxide-phosphorus was maximum phosphorus species and had high potential release risk to act as internal phosphorus sink. Correlation analysis showed that both reactive ferric-Fe bound phosphorus and metallic oxide-phosphorus in sediment were positively related to TP concentration of overlying water. In addition, a positive correlation was also observed between the sediment metallic oxide-phosphorus and chlorophyll a concentration in overlaying water. The effect of sediment characteristics on phosphorus fractions represented that reactive ferric-Fe bound phosphorus of sediment decreased with the decrease of oxidation-reduction potential, and residual-phosphorus increased with the increase of organic matter.