The Characteristics of the Composition of Various Phosphorus Forms in Lake Surface Sediments in Wuhan City

In order to reveal the characteristics of phosphorus composition within lake sediments in Wuhan City, forty surface sediment samples were collected from five types of lakes with water quality of grades Ⅱ, Ⅲ, Ⅳ, Ⅴ and inferior Ⅴ. Concentrations of total phosphorus (TP), organic phosphorus (Org-P), inorganic phosphorus (IP), Fe/Al-bound phosphorus (Fe/Al-P), and Ca-bound phosphorus (Ca-P) in these samples were analyzed using the standard measurement and test procedure (SMT). The ranges of phosphorus concentrations were 444.0-2 055.5 mg·kg^-1 for TP, 146.8-400.5 mg·kg^-1 for Org-P, 237.5-1 889.3 mg·kg^-1 for IP, 96.1-1 152.8 mg·kg^-1 for Fe/Al-P and 108.4-812.7 mg·kg^-1 for Ca-P, respectively. The results indicate that TP was dominated by IP, followed by Fe/Al-P, Ca-P, and Org-P. Among the five different types of lakes, contents of TP and various species of phosphorus (except Org-P) generally increased with the deterioration of water quality. In 26 samples, readily-released bioavailable phosphorus accounted for more than 50% of TP, indicating that these lakes would be faced with high risk of eutrophication, even under a scenario of decreased external phosphorus inputs. According to the local indicators of spatial association cluster map of various phosphorus species in Wuhan City, TP, IP and Fe/Al-P have high-high type of spatial agglomeration in four lakes of the industrial zone, while random distribution is observed in Ca-P and Org-P.