Effects of dissolved oxygen supply level on phosphorus release from lake sediments

Phosphorus (P) can be released from sediments into overlying water under certain environmental conditions, which may have a significant impact on water quality and result in continuing eutrophication. In this study, effects of oxygen supply level in the overlying water on the P release from sediments were investigated in controlled experiments. The results show that in anaerobic condition soluble reactive phosphorus (SRP) increased in the overlying water for the two studied sediments, and gradually reached equilibrium after 30 days. In anoxic condition, P was rapidly released within 1 day, SRP then decreased, and gradually reached equilibrium after 10 days. In aerobic and oxygen saturation conditions changes in oxygen supply levels did not significantly affect the P release. pH in the overlying water increased in anaerobic condition, and gradually remained constant after 30 days. In anoxic, aerobic and oxygen saturation conditions pH rapidly increased within 1 day in the overlying water, and then decreased slightly, and gradually remained stable after 10 days. P can only be released from the sediment of Lake Meiliang and Gonghu in anaerobic condition, and the released P was mainly from BD-P, HCl-P and NaOH-P fractions. The results also indicate that transformation between different P fractions occurred under different oxygen supply levels, biological activities may be the main reason.