Mobilization of Phosphorus From River Sediments.

Loading of excessive nutrients to open waters has negative impact on water quality and aquatic ecosystem. Although a significant fraction of phosphorus (P) entering rivers is trapped in river sediments, fluctuation of physio-chemical and biochemical conditions may promote remobilization of P from sediments and its removal to open waters. This study aimed to quantify the amount of P that can be released from selected sections of Patuxent, Nanticoke and Paul Creek rivers in the Chesapeake Bay watershed. Environmental parameters used to identify P release included change in biological activity, Eh, water temperature, salinity and pH (6-9). The results showed that the P released from sediment spiked with Shewanella putrefaciens CN32 was significantly higher in all river sediments compared to the sediment incubation alone. When the ambient pH (7.33) of the Nanticoke river sediment was decreased (to 6.0) or increased (to 9.0), P was released, with higher P release (1.9 µmole/g) at pH 9. The amount of P released due to the increase in salinity was the highest among all parameters analyzed in this study. For example, increase in salinity by 2 practical salinity unit (PSU) resulted in the release of 6.4 µmole/g P from Nanticoke river sediment. These results suggest that the release and removal of sediment bound P can be a new source of P in the Chesapeake Bay watershed.