DIstribution of organic phosphorus forms in lake sediments

A comprehensive understanding of the dynamics and potential mobility of phosphorus (P) in sediments requires separation and identification of its different forms, but the relevant information about organic P is insufficient. In this study, a detailed fractionation of organic and inorganic P was conducted on 22 different lake sediments, with an emphasis on understanding how organic P is distributed within various solid phases of sediments. Significantly positive correlations were observed between all of the inorganic and organic forms of P extracted at the same steps. Similar positive correlations were also found between the inorganic and organic P forms and their co-extracted metals and sediment organic matter. These relationships clearly demonstrated that both organic and inorganic P were bound in sediments by similar solid phases. Further analyses showed that the major organic and inorganic P pools could be basically divided into organic matter-bound and metalbound forms. The abundance of the former P pool depended on the content of organic matter in different sediments. The latter P pool included Fe and Al bound P as well as Ca bound P. The distributions between them depended on the relative abundances of Fe and Al to Ca in sediments. It was concluded that organic P forms in sediments had a distribution pattern similar to that of inorganic P, reflected by their similar binding phases and similar speciation changes in different sediments.