Miyun Reservoir Phosphorus Biogeochemical Cycling Of Environmental Simulation Test

Miyun Reservoir is the only headstream of surface drinking water in Beijing nowadays, and its water quality influences life and health of the capital people directly. It is at the stage of transferring from midtrophication to eutrophication. Phosphorus (P) is the key element that restricts the density and quantity of algae. So it is important to study the circulation of phosphorus in the system of sediments, water and algae.Accordingly, the simulation experiments that sediments absorb phosphorus, sediments release phosphorus, and algae absorb phosphorus were done, which was surrounding primary productivity in Miyun Reservoir. The results showed that the value of the maximum P concentration was 0.919mg/g in sediments, and the balance concentration of Total Phosphorus (TP) was 0.031 mg/L and that of the Dissolved Phosphorus (DP) was 0.018mg/L in the sediments-water interface (Ph=7.5, DO＜2, T=5℃). The average releasing velocity of TP and DP from sediments to water was 0.33μg/L and 0.42μg/L respectively everyday. When the culture medium was the mixture of lake water and sediments, the average absorption velocity of DP was 2 ng for per 10000 Microcystis aerugilnosa and 7.6 ng for per 10000 Scenedesmus obiquus respectively everyday. And the average increasing velocity was 1.19×10~5 per mL and 3.7×10~4 per mL respectively everyday.At the same time, the correlative experiments about the influence of environmental factors on the circulation of P were done. At the stage of sediments releasing phosphorus, pH,DO and Temperature (T) were regarded as the dominating factors. The results showed that the increasing of temperature, the reducing of DO and the deviation from neutral of pH contributed to TP releasing. DO was the first factor on TP releasing, next was T and pH. pH was the first factor on DP releasing. At the stage of algae uptaking P, the influence factors were regarded as temperature, illumination and pH. The results showed that the lack of T or illumination was not beneficial to algae fertility, and the fertility velocity was 1/100～1/10 of that in the natural condition. T was more important than illumination for algae fertility. When pH of culture medium is different, the fertility rate of algae was different. For Microcystis aerugilnosa, the best value of pH is 7.5, next is 8, 7 and 9 and for Scenedesmus obiquus the order is 7.5,8,9 and 7.