Influence Of Water Diversion Form Yangtze River To Taihu Lake On Alkaline Phosphatase In Taihu Lake

Eutrophication is a serious problem in Taihu Lake water environment, and is also the key project in Water Diversion from Yangtze River to Taihu Lake. Hence the phosphorus plays a great role in causing eutrophication and boosting algae’s mass reproduction in Taihu Lake. The Alkaline phosphatase is a kind of inducible enzyme. Many scientists believe that aquatic organisms producing alkaline phosphatase in an induced way is one of the main compensation mechanisms that offer bioavailable phosphorus sources to the aquatic organism. Owing to Yangtze River’s higher quantity of total phosphorus content, on the project of Water Diversion from Yangtze River to Taihu Lake, people attach much importance on whether the water from the Yangtze River would increase the eutrophication problem of the Taihu Lake. This paper provides and analyzes the statistical data from a representative29survey points in the whole Taihu Lake. The parameters about the Alkaline phosphatase activity, phosphate, the content of Chlorophyll A and other water chemical parameters at different survey points were measured in diferent water transfer periods. The Alkaline phosphatase activity and the state of bioavailable phosphorus in Taihu Lake were discussed.The main results were as follows:(1) During the water transfer period of the project Water Diversion from Yangtze River to Taihu Lake, the quantity of water transferred through Wangyu River from Yangtze River was as much as858.5million cubic meters, while the quantity of water draining off through Taipu River reached as much as1427.9million cubic meters. As a result, the regional water shortage problem was alleviated. Some parts of the lake’s water environment were improved. Nevertheless, the total amount of TP transferred from Wangyu River into Taihu Lake reached to103.7tons, and the total amount of DTP reached to52.9tons.(2) During the water transfer period in2008, the content of phosphorus and Chlorophyll A in various forms in the rivers around Taihu Lake and Yangtze River was monitored. The results showed that the sequence of concentration of TP, DTP and PO43--P in the rivers around Taihu Lake was obviously higher than that in the water of Taihu Lake, Wangyu River and Yangtze River. The total concentration of phosphorus in Yangtze River was higher than the average value of that in Taihu Lake, and was lower than that in the rivers around Taihu Lake and Wangyu River-Wangting interchange monitoring section. In light of the above-mentioned, it could be known that the project Water Diversion from Yangtze River to Taihu Lake is scenically reasonable. During the water transfer period, the concentration of TP and DTP in all zones of Taihu Lake showed tendency to descend. But the concentration of TP and DTP in water tended to ascend after the water transfer period. The water transfer did not exert obvious influences over PO43--P in all zones of Taihu Lake.(3) During the water transfer period in2008, the content of phosphorus and Chlorophyll A in various forms in each Zone of Taihu Lake was monitored. The results showed that the concentrations of TP, DTP, PO43--P and Chlorophyll A in each Zone of Taihu Lake were heterogeneous. In different zones, concentration of TP in the Zhushan Bay zone was highest and was lowest in Grass Type zone. Concentrations of DTP and PO43--P were the same. Concentration of Chlorophyll A in Estuary zone in Western Bank was highest and was lowest in Grass Type zone of Taihu Lake.(4) During the water transfer period in2008, the influences exercised on the values of APA,Vmax and Km by TP, PO43--P, TN and Chlorophyll A and other factors were studied. The results indicated that there was a significant positive linear correlation between both of the values of APA and Vmax and the content of Chlorophyll A. Under the circumstances that the concentration of TP ranged from0to0.1mg·L-1, the values of APA and Vmax decreased linearly and distinctly as the concentration of TP increased. Under the circumstances that the concentration of TP was more than0.4mg·L-1, there was a significant positive linear correlation between both of the values of APA and Vmax and the concentration of TP. There was a significant linear negative correlation between the Km value and the concentration of PO43--P. The value of Vmax/Km quotients, was positively correlated distinctly and linearly with the concentration of Chlorophyll A.(5) Through comparisons with the activities of Alkaline phosphatase in Taihu Lake in different seasons, it was found that the value of APA and Vmax in summer was higher than that in spring and winter, while the value of Vmax in autumn was higher than that in spring and winter. The Km value of the water in Taihu Lake in autumn and winter was higher, whereas the Km value of the water in spring and summer was lower. (6) During the water transfer period in2008, the spatial distributions of APA, Vmax and the Km value in different zones of Taihu Lake were studied. The results showed that the sequence of the value of APA, Vmax in different zones from high to low was as follows: Meiliangwang Bay zone>Estuary zone in Western Bank>Zhushan Bay zone>Gonghu zone>Centre zone of Taihu Lake>Grass Type zone of Taihu Lake. The sequence of the Km value in different zones of Taihu Lake was as follows:Centre zone of Taihu Lake>Estuary zone in Western Bank>Grass Type zone of Taihu Lake>Meiliangwang Bay zone>Gonghu zone>Zhushan Bay zone.(7) The results of the project Water Diversion in2008showed:before and during the trial period of water transfer project, the value of APA and Vmax in water of the different zones of Taihu Lake was steady or decreased a little. However, after the trial period of water transfer project, the value of APA and Vmax in water increased dramatically. Before and during the trial period of water transfer project, the Km value in water of different zones of Taihu Lake tended to decrease generally, but after the trial period of water transfer project, the Km value began to increase. The water transfer project had an adverse effect on the activities of Alkaline phosphatase, the maximum reaction rate of alkaline phosphatase activity and the Km value, and it reduced the speed of enzyme-hydrolysis of organophosphorus in water.