Characteristics Evaluation of Eutrophication About Hongfeng Lake

The eutrophication characteristics of Hongfeng Lake during 2003-2009 were analyzed and evaluated by synthetical trophic state index method to further clarify the status of the Hongfeng Lake water eutrophication.The results showed that the annual water transparency of Hongfeng Lake varied little.pH,permanganate index and chlorophyll a showed an increasing trend.The annual data of pH and chlorophyll a in recent years presented a water bloom risk.The annual mean values of total nitrogen and total phosphorus were high,although declined year by year,but the annual mean value surpassed water quality standard III of surface water.In the seven years,the annual mean value of total nitrogen exceed by 1.46,2.68,2.39,1.35,1.67,0.58 and 0.58 times,and total phosphorus by 6,0.16,1.2,10,4.4,2.2 and 0.4 times.The trophic status was eutrophic type in 2003,2006 and 2008.And mesotrophic type in 2004-2005,2007 and 2009.Total phosphorus and total nitrogen were the major contribution factors of eutrophication classification.Generally speaking,the nutriture of Hongfeng Lake was at meso-eutrophic level,and had the development tendency of eutrophication.