Effect of pH on Sedimentary Phosphorus Bioavailability under Sediment Disturbance Conditions

Effect of pH values on bioavailability of sedimentary phosphorus under sediment disturbance was studied.With sediments and waters taken from a eutrophic canal,concentrations of soluble reactive phosphorus(SRP)in overlying water and changes of phosphorus bioavailability in the sediments as influenced by disturbance and initial pH values were done in laboratory experiments.Results showed that sharp decreases in SRP from overlying water,resulting from sediment disturbance,were observed and the removal of SRP decreased gradually with an increase in initial pH,with the order of SRP removal under different initial pH values as pH 5,pH 7 and pH 9.5,which was attributed to neoformation of amorphous Fe oxides under low pH values.Based on mobility of phosphorus fractionations,BAP could be accurately estimated by the sum of NH4Cl-P,% BD-P(bioavailable,non-occluded Fe-P)and NaOH-nrP.By this estimation,proportions of bioavailable phosphorus(BAP)to Tot-P decreased gradually with an increase in initial pH.Percentage of BAP to total phosphorus(Tot-P) was 33.36%,the mean under three pH values,which was far lower than 85.04% which was calculated by traditional methods.However,the percentage of BAP to Tot-P was verse visa under both methods,which attributed to the change of algae available phosphorus.