Study On The Characteristic Of Nitrogen And Phosphorus Pollution Of Urban Lakes In Guangdong Province

Eutrophication is a process by which lakes gradually age and become more productive. However, humans add excessive amounts of plant nutrients (primarily phosphorus and nitrogen) to lakes in various ways. With the tremendous economic growth and increased population, the eutrophication of lakes situated in cities is more severe specially. The present study investigated the eutrophic status of 12 urban lakes in tropical and sub-tropical Guangdong Province from May to October in 2005.The results demonstrated that the 12 urban lakes of Guangdong province in the south of China are suffering from eutrophication. The 75% investigated lakes were eutrophic, especially Panlong tianhu Lake in Yunfu City and Liuhuahu Lake in Guangzhou City. All lakes were heavily polluted with nitrogen and phosphorus. The TN concentration of lakes ranged from 0.628 to 5.915mg/L, the mean was 1.97mg/L; the TP 0.024 -0.188mg/L, the mean was 0.092mg/L. In the DIN (dissolved inorganic nitrogen), NH4 had the highest proportion, and NO₂^- - N had the lowest. But in the other lakes of China, the proportion of NO₃^- - N is larger than NH₄⁺- N. The TP is composed by particulate phosphorus mainly, and the concentration of TSP (total soluble phosphorus) ranged from 0.006-0.055 mg/L with and PO₄^3--P 0.002-0.01 mg/L, the means were 0.015mg/L and 0.006mg/L respectively. The N/P ratios of the lakes ranged from 11.8-48.5, and the DIN/TSP ratio ranged from 76.6-892.1, which indicate that phosphorus was the limited nutrient for algal growth in the urban lakes of Guangdong Province.