| Dongping Lack is the second largest freshwater lake in Shandong province. It is the only natural lake on downstream of Yellow River, and is very important for the safety of control flood for the downstream of Yellow River. According to Eastern Route of South-to-North Water Diversion Project, Dongping Lack takes on the task of adjustment and impoundment. Dongping Lack will certainly play a very important role in medium and long development of Shandong province. It is signality of water quality research and environmental protection for Dongping Lack. This study is about the fact-finding and sampling analysis, and the analysis evaluation for water enviroment of Dongping Lack. This study is in order to provide effective information for water enviroment and development tendency of Dongping Lack, and it is also in order to provide scientific basis for environment adjustment and Eastern Route of South-to-North Water Diversion Project.The samples were taken continuously from Dongping Lack from2006to2010. Water quality indexes of water temperature, depth of water, transparency, dissolved oxygen, pH value, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, total nitrogen, phosphate phosphate, total phosphorus, permanganate index, main ions (Cl-，SO42-, HCO3-, CO32-,Ca2+, Mg2+, K+, Na+), mineralization degree, copper, oil and chlorophyll a were analysed. Each factor was evaluated. Chl-a (as the standard factor), TP(as the important factor), TN,COD and SD (as the main factor) were selected as the best evaluation factors. Weighted comprehensive nutritive index method was used to evaluate eutrophication for understanding the present situation of water environment.The result is as follows:The mineralization degree increased year by year for Dongping Lack. The types of water those were detected were ClⅢCa, ClⅡCa, SⅡNa, SⅡCa, SⅢCa. The average content of cation was Ca2+> K++Na+> Mg2+. The calcium accounted for44%of total cation. The average content of anion was SO42-> Cl-> HCO3-> CO32-. The sulfate ion accounted for42%of total anion. The degree of correlation for mineralization degree and main ion was SO42-> Ca2+> K+Na+> Mg2+> HCO3-> Cl-. The result had significant positive correlation with SO42-and Ca2+. It had no significant correlation with Cl-. So the water with higher mineralization degree usually manifested the type of sulfate (SⅡNa, SⅡCa,SⅢCa). The water with lower mineralization degree usually manifested the type of chloride (ClⅢCa, ClⅡCa). With the increase of mineralization degree for Dongping Lake, the type of water gradually transformed from carbonate into chloride and sulfate.The variation tendency of eutrophication for Dongping Lack was stable. The eutrophication state was between moderate and mild. The pollution was qualitative evaluated between sound and light. The main pollutants were nitrogen and phosphorus.The average value of total nitrogen for Dongping Lack was2.480mg/L. It was over evaluation criteria of the lake eutrophication (0.2mg/L). The rate exceeded the standard was93%. The multiple of average value exceeded the standard was1.48, and the multiple of maximum value was5.07. The average value of inorganic nitrogen was1.437mg/L. It accounted for58%of total nitrogen. According to the order of content, the inorganic nitrogen was consisted of NC3--N, NH4+-N and NO2-N. The NO3--N had significant positive correlation with inorganic nitrogen in the level of p<0.01.The average value of total phosphorus for Dongping Lack was0.169mg/L. It was over evaluation criteria of the lake eutrophication (0.02mg/L). The rate exceeded the standard was53%. The multiple of average value exceeded the standard was2.36, and the multiple of maximum value was10.88. The average value of PO43--P was0.009mg/L. It accounted for5.2%of total phosphorus.The nitrogen of Dongping Lack had a wide range of sources. The water with abundant nitrogen usually manifested the type of phosphorus restriction. The suitable proportion of nitrogen and phosphorus accounted for20%.The nitrogen restriction accounted for20%and the phosphorus restriction for60%. Dongping Lack was the lake which was the type of aquatic plants occupied dominant, rinsing state and shallow waterweeds.The progress of eutrophication for Dongping Lack is slower now. The state of eutrophication is comparatively stable. But the destroyed ecosystem to recover with self regulation and self repair system still needs a very long time. |
