Phosphorus fractionation and bio-availability in Taihu Lake (China) sediments

Typical sediments from Taihu Lake, a meso-to-hypereutrophic lake, were collected and examined on the basis of P-fractionation by sequential extraction scheme. Sedimentary inorganic phosphorus were fractioned into four forms and the rank order according to the mean concentration of P-fractions in Taihu Lake was NaOH-P > BD-P > HCI-P > NH4Cl-P. The concentrations of BD-P were linearly correlated with the content of active Fe (R2 = 0.96). Also, 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 six sediments investigated (R2 = 0.96). Moreover, the bio-available phosphorus (BAP) content was estimated by the sum of NH4 Cl-P, BD-P, and NaOH-P, viz. BAP = NH4 Cl-P + NaOH-P + BD-P. In Taihu Lake, the BAP contents are ranging from 0.10 mg/g dw to 1.25 mg/g dw, and average 0.40 mg/g dw for all sediment samples. The relative contributions of BAP to total sedimentary phosphorus (TP) and inorganic sedimentary phosphorus (IP) range from 18.67% to 50.79% (33.61% on average) and from 52.82% to 82.09% (67.81% on average), respectively.