Characterizing Constituents of Sediment Phosphorus Fractionation in a Freshwater Shallow Lake System

[Objective] This study aimed to characterize constituents of phosphorus(P)fractionation as well as reciprocities among factors in sediments of a freshwater shallow lake. [Method] Surface sediment was discretely sampled at 24 sites through Van Veen grabs. Based on a modified sequential extraction scheme, P fractionation was determined as Fe/Al bound P(Fe/Al-P), Ca bound P(Ca-P), solute and reductive P(S/R-P) and organic P(OP). Curve estimation and Pearson product-moment correlation were employed for statistical analysis. [Result] Total P(TP) content ranged from 443 to 774 mg/kg. Inorganic P(IP) was the major component of TP,of which Ca-P was dominated with an average of 51%±9.7%. Average contents of P fractionation were in the following order: Ca-P(51%) OP(29%) S/R-P(8%) Fe/Al-P(7%). The molar ratio of Fe to P was 11- 20, close to the threshold value of P leaching. [Conclusion] In freshwater shallow lakes, IP and Ca-P were prone to be relatively high, whereas Fe/Al-P was low compared with deep lakes. Occurrence of spatially monotonic gradient indicated the primary causation of anthropogenic sources. Imminent sediment P liberation was also expected. Close associations among TP, Fe/Al-P and Ca-P, implying that anthropogenic P was mainly bound to metals in particulates. Significant correlations of TOC and P fractionation highlighted endogenous mechanism and authigenic origin in sediments.