Effects of sustained-release composite on the oxygen levels and sediment phosphorus fractions of an urban river in Shanghai.

The eutrophication of many rivers and lakes is attributed to the anoxia and the increasing internal loading of nutrients from sediment. A novel sustained-release composite (SRC) synthesis of stearic acid and calcium peroxide (CaO2) was applied to supply a water body with oxygen endured in this study. The influences of SRC on the dissolved oxygen (DO) level, pH and total phosphorus (TP) of an urban river in Shanghai were studied. The results show that SRC has a longer oxygen-releasing cycle and a more tender effect on pH with the comparison of CaO2 powder. Reduction of 79.6% in the concentration of TP was observed in the water column. After 35 days of SRC addition, there was a significant positive correlation between TP and DO. As a consequence, the phosphorus fractions in sediment, including loosely sorbed P (NH4Cl-P), redox-sensitive P (Fe-P), calcium bound P (Ca-P), aluminium bound P (Al-P) and residual P (organic and refractory P) were affected by the addition of SRC. The NH4Cl-P and Fe-P fractions in the sediment that could release P easily were well constrained under the positive effect of SRC.