Dynamic characteristics of nutrients and causal analysis in eutrofic reservoir: a case study of Shibianyu reservoir

摘要

Eutrofication and the resulting proliferation of phytoplankton have become a serious problem of reservoirs around the world. In order to make effective algae control measures through reducing concentrations of nutrients, in this study both the dynamic characteristics of nutrients and its source were investigated in Shibianyu reservoir located in north-western of China. The results showed that a 2.8 mg/L of annual average total nitrogen concentration in Shibianyu reservoir was observed, which exceeded the source water quality standard during whole monitoring years, and the maximum concentration reached 5.1 mg/L in spring. Moreover, it was observed that there is high total phosphorus concentration during the mixing period in winter or the heavy rainfall period. The hypolimnion became anoxic during the stratified period to increase the release of nutrients from the sediments. The nutrients of upper water increased rapidly when stratification disappeared because the high concentrations of pollutants in the bottom water were carried into the upper water. The continuous heavy rains led to significant increase of nitrogen and phosphorus in summer because a large number of sediment was flushed into reservoir. The excess nutrients promoted algae to multiply. Intense cyanobacterial blooms have been observed in Shibianyu reservoir. It is premise to improve water quality in Shibianyu reservoir that the infusion of nutrient must reduce during rainstorm period. Inhibition of endogenous pollutants release would be the key to control and improve the water quality in Shibianyu reservoir.