The Primarily Study And Tests On Annual Eutrophicational Changes Of City Lakes In Wuhan

The research was to analyze the change of all water indicators and evaluate the eutrophication situation in some inner lakes of Wuhan city, including Ziyang Lake, Simei Tong (East, West two Lake domains), Houxiang River, Linjiao Lake, Beihu and Xihu Lake, Neisha Lake as researching objects, main results are as follows:1. Evaluating the three indicators of lake water quality-permanganate index (CODMn), total nitrogen (TN) and total phosphorus (TP), CODMn of eight lakes were all lower than class V in the standard of lake surface water (); all indicators of Simei Tong East and the Houxiang River lake were lower than class V in the standard of lake surface water; TN and TP of Neisha lake were all inferior class V,and critically exceeded standard; TP of Ziyang Lake, Simei Tong West and Linjiao lake were inferior class V;TN of Xihu Lake and Beihu Lake were all inferior class V, other indicators were lower than class V standard.2. The evaluated results with TSIc method was as follows:the water quality of Simei Tong East Lake was best that it was in a period of transition of moderate eutrophication to eutrophication; Ziyang Lake, Houxiang River lake and Xihu Lake were in the level of eutrophication; Simei Tong West Lake and Linjiao Lake are in a period of transition of eutrophication and heavy eutrophication; the water quality of Beihu Lake and Neisha Lake was in heavy eutrophication, and Neisha Lake water was worst. The lake eutrophication index was higher in the summer and autumn, lower in winter and spring.3. Changes in Chla mainly influnced by water temperature, light intensity and other factors, and water temperature is the main factor. The major trends of Chla's variation were higher in the summer and fall than in the winter and spring. All this 8 lakes'TN and TP index were higher than the normal level, thus it will not became one of the reasons that limited the algae reproduction.4. The parameters like N and P which existed in different forms and CODMn had relationships with chlorophyll a (Chla): Except Neisha Lake, there is a negative correlation between quantity of NO3--N and Chla in other lakes. In the most of the water, alage is an important source of CODMn.Regardless of eutrophicational degree, the most likely relationship between Chla and CODMn is positive, especially in the water blooming lakes, the correlation between the two is particularly significant.All lakes had relatively stable pH, which is neutral with a little alkaline, and the pH value in high-content-Chla lakes was higher than low-content-Chla, the correlation coefficient is 0.5493; it shows that the life activities of algae affect water pH. Simei Tong West Lake and Linjiao lake are in a period of transition of eutrophication and heavy eutrophication, and only these two lakes have turned up algal bloom, whose TN based on organic nitrogen, the concentration and change of TN had a positive correlation with Chla; Ziyang Lake and Xihu Lake are in the stage of eutrophication, TN based on organic nitrogen and the concentration and change of TN had a negative correlation with Chla.