Phosphorus speciation and sedimentary phosphorus release in an urban bay (Dachan Bay, China) impacted by multiple anthropogenic perturbations.

Sedimentary phosphorus (P) release and retention are important in controlling P dynamics in coastal waters. Here, two sediment cores were analysed to understand the P speciation and sedimentary P release characteristics in Dachan Bay, Shenzhen, where was highly influenced by human activity. Total phosphorus (TP) concentrations, 52.3 to 1119 μg g, fluctuated greatly with depth. Four P binding forms were fractionated: iron-bound P (FeP), authigenic apatite (CaP), detrital P (De-P), and organic P (OP) with the following order of concentration: Fe-P > OP > De-P > Ca-P. The P pollution index (PPI) revealed the contamination of sediment with P in recent years. Additionally, the potentially mobile P pools and long-term P release in the sediments were estimated, and the results indicated that, sediment was an important potentially mobile P pools in the water column, especially in nearshore areas, which required the attention of management departments.