The Analysis On Eutrophication And Prediction Advance Warning On Water Quality In Dianshan Lake

The current global shortage of water resources has become an indisputable fact.And eutrophication as a global problem of water pollution is increasingly attracting the attention of the whole society, especially eutrophication of lakes,which is menacing the security of cities water supply.The object of this research was Dianshan Lake and a systemic work on eutrophication was done under the security target of water supply.Firstly,some data of water quality status in Dianshan Lake were collected and researched.Based on those data,some of them were selected and analyzed,and then the space-time curves of water quality in Dianshan Lake were gotten.The results showed that:the trend of chlorophyll-a(Chl-a) concentration in all monitoring sites was downward, but the results of assessment to the overall and annual chlorophyll-a concentration were still eutrophication.The annual average of total phosphorus(TP) concentration in each monitoring site was between the classâ…£andâ…¤of water quality standards,and the exceeding multiple was 6.12 times to 10.09.The total phosphorus concentration in Dianshan Lake was severely overweight.The annual average of total nitrogen(TN) concentration was 3.56 to 5.17 mg/L,which was worse than the classâ…¤of water quality standards.On the three indicators of eutrophication,the water quality of Dianshan Lake could not meet the requirements of the classâ…¡.Secondly,the Dianshan Lake's nutrition status was evaluated in our research according to the monitoring data of the lake water from 2000 to 2003.The relationship between Chlorophyll-a and environmental factors was discussed.Meanwhile,the relationship between Chlorophyll-a and total nitrogen,total phosphorous was analyzed.The lake was under eutrophication due to the results that TST_M=58(calculated by Carlson). Multiple stepwise regression data showed that the Chl-a influencing factors with significance varied according to different sampling locations. However,4 of the 5 sampling location have showed that TP was a common factor with great significance.Significant influencing factors of the lake were water temperature,TP and Ph,with the total correlation coefficient 0.683,whereas,TP and TN stood out with the coefficient 0.785 after logarithmic standardization.Our data showed that TP had an great positive correlation with Chl-a content.Whereas the relationship between Chl-a content and TN is complex and needs further investigation. Furthermore,the content of Chl-a remained stable while the contents of TN and TP reached 9.37 mg.L-1,0.37 mg.L-1 for each,which indicated that the lake water had excess N and P.Finally,the concentrations of chlorophyll-a which represented the quantity of algal to predict have been chosen and advance warnings on eutrophication have been given.Then,a prediction model was established by means of nonlinear regression analysis.Furthermore,aiming at the forward studied results and according to popular methods of advance warning of water quality,a corresponding classified warning project has been made.The algae biomass peak could not be accurately simulated by the modle established with means of nonlinear regression analysis.It remained to be further research and other statistical models used to supplement and perfect.But the results of early warning obtained by using the modle established with means of nonlinear regression analysis could meet the basic requirements of water quality management.