[Distribution and Bioavability of Phosphorus in Surface Sediments in Megalopolis: A Case Study of Chengdu].

: A total of 33 surface sediments were collected from rivers in Chengdu. The content of phosphorus species was measured with the chemical continuous extraction method (SMT) and in situ monitoring techniques (DGT). Multivariate statistical analysis was used to analyze the spatial distribution of phosphorus species in sediments. The release flux of DGT-P in sediments and their pore water was calculated in this study. It is helpful to understand the influence of sediment endogenous pollution and human activities on the environment. The results show that the phosphorus species have a spatial variability. The average content of TP in the surface sediments is 1132.41 mg·kg-1, which is higher than the background value of 365.00 mg·kg-1 in Chengdu. The Ca-P is the most dominant species, accounting for 70.58% of the TP on average. The study area is divided into three groups based on spatial clustering. Groups 1 and 3 show large differences of phosphorus morphological structures, while Group 2 is small. The contents of phosphorus in the surface sediment of Groups 1 and 3 are generally higher than those of Group 2. The DGT-P concentration has a good correlation with the soluble DTP concentration, bioavailable Fe/Al-P, and OP concentration, respectively. The DGT technology can be used as a fast, in situ, reliable method for measurements of the bioavailable content of sediments. The higher release fluxes of bioavailable phosphorus are N8, W11, and N2, which are 20.05, 17.13, and 14.79 mg·(m2·d)-1 respectively. The available phosphorus release capacity is closely related to human activities.