Spatial and temporal distribution characteristics of different forms of inorganic nitrogen in three types of rivers around Lake Taihu, China.

In order to control nitrogen (N) pollution of Lake Taihu, China, we studied the spatial and temporal distribution characteristics of inorganic N in inflowing rivers polluted by industry, agriculture, and domestic sewage during low, moderate, and high flow periods. The results showed that dissolved total nitrogen (DTN) was the main fraction of total nitrogen (TN) input from these rivers. Inflowing rivers had distinct impacts on TN, DTN, ammonium N (NH), and nitrate N (NO) concentrations of Lake Taihu during the low flow period. Particulate nitrogen (PN) had an impact on Lake Taihu during the three flow periods and all the three types of rivers would increase PN concentration in the lake. Rivers polluted by agriculture had the greatest impact on Lake Taihu's TN, DTN, NO, and dissolved inorganic N (DIN) concentrations, while rivers polluted by industry had the greatest impact on NH concentration. Therefore, agriculture and industry should be key targets for nutrient reductions. The in-lake N concentrations were higher than those of inflowing rivers during moderate and high flow periods.