Eutrophication Risk Assessment

Abstract

Eutrophication is commonly considered as one major aspect of global environmental degradation (Nixon, 1995). To protect and manage the water quality, indices are useful tools to communicate with managers because they reduce complex scientific data, integrate different types of information and produce results that can be easily interpreted in the perspective of water quality management (Potapova and Charles, 2007). Many researchers consider that the main reason for the dramatic propagation of algae is the increase in concentration of nutrient materials, such as nitrogen, phosphate, etc. Nonetheless, the relationships between physiochemical and biological factors that impact the growth of algae, such as sunlight, nutrient salts, changes of seasons, water temperature, pH value, and the algae itself, are very complex. It is very hard to forecast the trend in algal growth and to set the eutrophication indicator. A common method was to indicate the water nutrient level using the main representative parameters. The parameters mainly include the concentrations of total phosphate (TP), and total nitrogen (TN), transparency, concentration of chlorophyll a, dissolved oxygen (DO), and so on. According to the parameters, the lakes are divided into different trophic levels, such as poor, middle, eutrophic and so on. The trophic level criterion is different for different countries and different reseachers. Tables 7.1, 7.2 and 7.3 show the trophic level proposed by the United States Environmental Protection Agency and used by Dianchi Lake and East Lake in Wuhan.