THE CONCENTRATION AND DYNAMICS OF SEDIMENT PHOSPHORUS IN VARIOUS LAKE REGIONS OF LAKE DONGHU

The concentration and seasonal dynamics of phosphorus in the sediment(0—5cm,5—10cm)of Lake Donghu were studied at six stations with different nutrient levels. The sampling was taken by a core sampler monthly from March 1998 to February 1999. On the annual average of the six stations,P content in the sediment was 1.15mg/g. The P content in the sediment at Station Ⅰ(Ⅱ)in the present study was 1.42(1.03)times that in the early 1980s. At Station 0 where there was heavy sewerage discharge,the sediment P content was as high as 2.78mg/g,while at the less affected Stations Ⅳ and Ⅴ,it was only 0.52mg/g and 0.50mg/g,respectively. There was a good relationship between the P content of the sediment and the P content of the lake water(r=0.997,n=5,p0.02). By comparing the P content of the sediment and water column,and external P loading in some Chinese lakes,it appears that if the P content of the water column is high and external P loading is large,the P content in the sediment is generally also high. Predictably,the great P pool in the sediment will still be a threat to the water quality of the lake ecosystem even if the external loading is under control.