Eutrophication Investigation Of Baihua Lake And Study On The Phosphorus Forms In Sediments

Nowadays,eutrophication is one of the ecological problems in lakes and reservoirs.With the development of economy,many lakes were polluted,especially water eutrophication caused by nitrogen and phosphorus.Baihua Lake is one of the three major drinking water resources of Guiyang,which is the capital of Guizhou Province.Baihua Lake is located on the upstream of Yangtze River,so condition of lake pollution has some relationship with ecological system of Yangtze River. The environment deterioration,during the process of economic development,does not draw enough attention,so this lake has been deadly polluted.This has greatly damaged the environment quality of this area and influenced the working and living of peripheral population,and restricted the sustainable development in this area as well.Implementing lake water environment ecology controlling projects thus becomes significant for the social and economic development.This study,based on the experiments and data analysis of 10 core sediment sample(from three layers) taken in March,2008,carries out research on current water eutrophication and analyzed the limitative factor of current Baihua Lake eutrophication and proposes the rational disposal measures according to the present condition of eutrophication.This thesis draws the following conclusions:1.The main reason for the eutrophication in Baihua Lake was due to the input of nutrient materials caused by human beings.The analysis shows the sources of nutrient were from urban and rural sewerage and industry sewerage,the fertilizer losing from farmland,the release of N and P from the sediment.Above all,the external pollution which contains phosphorus and nitrogen was an major factor,even the most important.2.The dissolved oxygen in surface water is high,and become lower from surface to the bottom.The water in the lake was alkaline,and the range of pH is 7.53～8.60.The concentrations of total phosphorus and total nitrogen are high,and they are 0.01～0.28 mg/L and 0.72～3.38 mg/L,respectively.The ratio of total nitrogen and total phosphorus is 15.4～84.5,which is bigger than 10,so that the phosphorus is the limitative factor.3.The concentrations of total phosphorus and total nitrogen in sediments are high,and they are 685～2300 mg/kg and 729～2516 mg/kg,respectively.The concentrations of TP and TN were different in sites and depths;vertically,the deeper the depth was,the higher concentrations of TP and TN.4.Organic phosphorus is the highest in all forms of phosphorus, about 37.3-52.1%of TP.The highest concentration of inorganic phosphorus is Ca-P,the second is O-P,the third is Fe-P,and the concentrations of Al-P and DP remain low.From the above factors,we come to the conclusion that the lake was already at a eutrophic state,which should attract much attention. Combined with the present condition of Baihua Lake,the author of this thesis proposes several suggestions:1.Controlling the entering of nutrients;2.Controlling the release of endogenous nutrition material;3. Setting up a good aquatic ecosystem;4.Protecting the surrounding environment of the lake.