Study On Caohai Lake Eutrophication As Well As The Criteria And Control Standards For The Nutrient Phosphorus

At present, the problem of the lake eutrophication has become a global one of the hot issues of water ecological environment, to effectively control the lake eutrophication and protect the lake environment, it is imperative for the lake nutrient concentration to set a benchmark and control standards. China is a country of many lakes, most of the lakes also widely distributed, and most lakes have an obvious regional differences in the nutrient levels and eutrophication effects. Therefore, we should be reasonable to set nutrient criteria and control standards according to the study on the lake region.This paper introduces detailedly the present situation and the control measures of the lake eutrophication in China, as well as the existing state of phosphorus in lakes and the way of transformation, and systematic analysis the study method of the domestic and foreign scholars to determine lakes nutrient criteria candidate variable selection and the reference state, based on the above analysis, finally, we determine the lake nutrient benchmark value and control standard value.By choosing Caohai lake as the research object, based on consulting a large number relevant research literature of the domestic and abroad about lake nutrient benchmarks and control standards, and collecting the water quality data of Caohai lake from over the years and adding to field sampling, this paper analysis the present situation and changed trends of Caohai lake eutrophication, the same time, with the help of SPSS software, analyzing to the indicator variables by the principal component analysis, correlation analysis and multivariate linear regression analysis, by this way, determining the Caohai lake nutrient benchmark candidate variables. By using the reference lake approach, lake population distribution approach and model prediction approach, we analysis the Caohai lake nutrient criteria candidate variable and determine its nutrient criteria reference state value. Finally, according to Carlson theory, we deduce the Caohai lake nutrient total phosphorus control standard value. From this analysis process, we can draw the following conclusion:(1) In recent years, Caohai lake water quality has improved than before, but its water trophic status is still in between moderate eutrophication status and severe eutrophication status. Now, Caohai lake water quality grade is in V class water, and its water body function only use to agricultural and general scenic water.(2) Through the comprehensive analysis of various nutrient criteria candidate indicator variables and Caohai lake region environment, we determine the Chl-a, TP, TN, SD as its nutrient criteria candidate variables. Using statistical analysis to determine the Chl-a, TP, TN, SD reference status criteria value, its value is 2.000μg/L, 0.010mg/L,0.177 mg/L,2.200m, and making the total phosphorus concentration 0.010mg/L as Caohai lake nutrient TP criteria values. Finally, according to Carlson theory, we calculate Caohai lake nutrient total phosphorus control standards value 0.016mg/L.