THE VARIATION AND DISTRIBUTION OF THE PHOSPHORUS CONTENT IN DONGHU LAKE, WUHAN

This paper summarizes the dynamics of phosphorus content(all referred to PO4)in 1973—1985 in Lake Donghu, Wuhan. In terms of area weighted means, the contents of TP, TDP and DRP in the observing period were 0.244 mg/l(1983—1985), 0.121 mg/1(1981—1984)and 0.051 mg/1(1981—1984)respectively. Contents of both of the total phosphorus(TP)and the total dissolved phosphorus(TDP)were observed to have two peaks in each year, one in March-May, and another in August-September, while their lowest values were measured in winter(December-February)when water temperature became the lowest. As to the dissolved reactive phosphorus(DRP), the highest content was measured in January-March and the lowest in May-July.The phosphorus contents in the Lake increased obviously in last decade and fluctuated markedly with the years. There was conspicuous difference in the horizontal distribution of phosphorus in the Lake, but little difference was observed in its vertical distribution. As for the composition of phosphorus, the amount of the particulate phosphorus(PP)was the largest and the dissolved non-reactive phosphorus(DNP)was the smallest, amounting 63.4% and 12.0% of the total phosphorus, respectively, in 1983—1984.