| This study is supported by the sub-project “The effects of nitrogen, phosphorus and trace elements on water quality in landscape waters” of the twelfth Five-year Plan of national water projects. The C uiHu lake, a typical landscape water of Kunming, is selected as research object. This thesis has analyzed the pollution sources of the CuiHu lake, evaluated its current pollution situation, and summarized the seasonal variation of its water quality index. Detailed analysis has been made on the migration and transformation law of its nutrients as well as the balance of payments. In addition, the correlation between the characteristics of its phytoplankton community and the water environmental factors makes it possible to identify the main control factors of eutrophication for the C uiHu lake. O n this basis, the thesis proposes a basic strategy of water pollution control and water quality improvement. The main conclusions are as follows:(1) The main pollution sources of the C uiHu lake consisted of the reclaimed water, deposition, the surface runoff, Black-headed Gull droppings, and tourist activities. This study investigated the seasonal variation of water organoleptic indicators, the conventional physical and chemical indicators, nitrogen and phosphorus nutrients and phytoplankton by the continuous water quality monitoring in different points, and evaluated the water pollution situation of the CuiHu lake. The results showed that the seasonal variation of the water quality was obvious, the overall presentation appeared as substandard V class. This study has confirmed that the C uiHu lake was severely eutrophic, most serious in winter. During the survey period, a total of 109 species of phytoplankton were identified, which belongs to 7 phyla. The majority of them were Chlorphyta, and there were seven kinds of dominant species. The phytoplankton abundance varied seasonally with the ma ximum value in winter, and the Bacillariophyta accounted for the vast proportion.(2) To further determine the intensity of each pollution source, this study focused on the analysis of nitrogen and phosphorus nutrient characteristics of different pollution sources of C uiHu lake. Meanwhile, small simulation tests under different replenishment indicated that the concentration of TN and TP in the overlying water replenished by the tap water performed release; while in the overlying water replenished by the reclaimed water and the surface water they showed adsorptive accumulation process. Finally, the nitrogen and phosphorus nutrient balance analysis in CuiHu lake showed that the reclaimed water was the dominant input way of TN and an important input way of TP, with Seagull droppings being another important input way of TP. Outflow water and leakage water were two main output ways of TN and TP. The NPA of TN and TP were very high. They respectively accounted for 36% and 34% of the total input.(3) Years of research data of the CuiHu lake shows that its water quality deterioration and eutrophication aggravation have an important influence on the function of the landscape water. According to RDA, TP、DTP、PO43-、NH3-N、T、DO and p H were the most important environme ntal factors affecting the distribution of phytoplankton in C uiHu lake, which contributed to the eutrophication. The main control factors of water eutrophication were phosphorus, ammonia nitrogen and water pH.(4) Based on the above analysis and conclusions, and in accordance with the principle of “main symptoms and cure supplement”, the thesis puts forward the following specific strategies: enhancing the water quality to control the pollution, increasing the amount of water to shorten the water exchange cycle, establishing local cross flow composite biological filtration process(2000 m3/d), setting plug flow pump in multiple dead zones, and establishing ecological floating island to purify water. |
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