KINETIC CHARACTERISTICS OF PHOSPHATE RELEASE FROM SURFACE SEDIMENTS IN ESTUARIES

A total of 3 surface sediment samples collected from the estuary of Licun river into Jiaozhou Bay were studied for the behavior of phosphate release and the effects of salinity, temperature, waves strength, suspended solids concentration on release kinetics. According to our experiment, the kinetic process of phosphate release can be divided into 3 phases:rapid release phase(0~1 h), slow release phase(1~8 h) and balance phase(>8 h). Increasing salinity can accelerate phosphate release. The largest release quantity occurred at salinity values between 0 and 10 suggesting that phosphate release is very sensitive to the salinity mutation of water mass. Increasing temperature accelerates phosphate release as well. At high temperature (>20 ℃), the release rate is 10 times as high as the release rate at low temperature (<10 ℃). Wave oscillation frequency has similar impact on release rate as temperature does. Phosphate release quantity increases significantly for the sediments in full suspension. When the concentration of suspended particles is reduced, both high release rate and slow release rate increase, and the quantity of slow release increases about 40% and the total release quantity also increases significantly.