EFFECTS OF in-situ SEDIMENT TREATMENT OF PHOSPHORUS RELEASE IN WUHAN EAST LAKE, CHINA

In-situ sediment treatment with salts is a promising approach for preventing P release from sediments. Five 35-days tests of undisturbed sediment cores had been applied under anoxic conditions, which were (1) no additive, (2) Al(2)(SO(4))(3), (3) FeCl(3), (4) CaCl(2) and (5) NaNO(3). To identify changes in the P-binding sites in the sediment caused by the treatments, different P binding forms were extracted from the sediment before and after the treatments. We found that the mean P release rates for anoxic treatments with Al(2)(SO(4))(3), FeCl(3), CaCl(2) and NaNO(3) were -0.644 mg.m(-2).d(-1), 0.033 mg.m(-2).d(-1), 0.644mg.m(-2).d(-1) and 2.574mg.m(-2).d(-1), respectively, while the P release rate with no additive was 7.314 mg.m(-2).d(-1). We also found that adding CaCl(2) prevented P release because of the apatite formation and because P(Ca) (Ca-bound P) increased at the sediment surface. Addition of Fe(3+) and NO(3)(-) to the sediment increased the amounts of P(Fe, Mn) (redox-sensitive P, mainly bound to Fe and Mn compounds), since iron oxide has the ability to combine P. Addition of Al(2)(SO(4))(3) increased the fraction Of P(Al,Fe) (P bound to Al and Fe oxides) and decreased the P and Fe in the water above the anoxic sediment, showing the greater ability of Al in binding P.