Phosphorus Fractionation and Bio-availability in Surface Sediments from the Middle and Lower Reaches of the Yellow River

Species and bioavailability of phosphorus in surface sediments from the middle and lower reaches of the Yellow River were investigated using the sequential extraction method. Sedimentary inorganic phosphorus were fractioned into four forms and the rank order according to the mean concentration of P-fraction in Yellow river was HCl-P > NaOH-P > BD-P > NH4Cl-P. The linear relationship between the sum of BD-P and NaOH-P and the sum of active Fe and active Al content was observed within the twelve sediments investigated (R2=0.66). Moreover, the bio-available phosphorus (BAP) content was estimated by the sum of NH4Cl-P, BD-P, and NaOH-P, viz. BAP = NH4Cl-P + BD-P + NaOH-P. In Yellow River, the BAP contents were ranging from 0.031 mg/g dw (dry weight) to 0.066 mg/g dw, and average 0.050 mg/g dw for all sediment samples. The relative contributions of BAP to inorganic sedimentary phosphorus (IP) range from 41% to 62% (53% on average).