Vertical distributions of phosphorus fractions in sediments of three typical shallow urban lakes in PR China

Sediment cores were sampled from three typical shallow urban lakes in China. The Standards, Measurements and Testing (SMT) programme, proposed by the European Commission, was employed to characterize the vertical distributions of phosphorus fractions in sediment profiles. The results showed that TP contents ranged from 1,198.9 to 1,897.3, 1,289.1 to 1,652.1, and 611.7 to 760.3 mg kg(-1) in sediment profiles of Darning Lake, Mochou Lake, and Xuanwu Lake, respectively. Within the 50-cm sediment profiles, phosphorus distributed mainly in IP, and the OP contents only accounted for 9.7%--16.3% of TP. For IP in sediments, the AP was the predominant fraction for Darning Lake and Mochou Lake, accounting for 92.8%, and 71.4%, respectively. While for Xuanwu Lake the proportion of NAIP to IP was higher than that of AP (41.7%+/- 16.0%), indicating that the Xuanwu Lake was polluted more heavily than the other two lakes. The phosphorus concentration in pore-water (TDP) correlated significantly to the P fractions in sediments, especially to the OP and NAIP contents, which could be predicted by: TDP (mg L-1) = 0.005 OP (mg kg(-1)) - 0.001 NAIP (mg kg(-1)) + 0.138 (R-2 = 0.836, P<0.01). The physicochemical properties of sediments presented significant correlation to the contents of P fractions, highlighting the importance of the physicochemical properties of sediments for the phosphorus fraction distributions in lake sediments.