Release characteristics of sediment P in all fractions of Donghu Lake, Wuhan, China

The aim of the study was to understand the releasing characteristics of sediment phosphorus (P) in all fractions under varying environmental conditions and the relationship between sediment P and eutrophication in shallow city lake, Donghu Lake of Wuhan in China. Effects of P concentration in overlying water, oxygen, light, pH, temperature, and agitation intensity on release processes of sediment P in all fractions in Donghu Lake, China, were investigated. The release quantity and release rate of sediment P in the distilled water were significantly higher than those of lake water, and under anaerobic condition, they were higher than those of aerobic treatment. The concentrations of each P form decreased obviously in both dark and irradiated systems. Both high and low pH promoted the release of Fe/Al-P, IP, and TP, but Ca-P decreased sharply with decreasing pH, while the difference of OP was not obvious. The release rate of each P form accelerated drastically when water temperature rose from 5 to 30 degrees C. The magnitude of the each P form released increased with the increase in the agitation intensity at the first 6d, while it showed no significant difference after 8d in different agitation intensities (100-200rpm). The results showed that the extent of P in all fractions released from Donghu Lake sediment was affected variously by the environmental factors, and the sediment was unstable, at risk of releasing P to Donghu Lake