Mobilization of phosphorus from East Creek in the Chesapeake Bay Watershed

Upreti, Kiran
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University of Delaware
Nutrients released to open waters may cause deterioration of water quality and impact aquatic ecosystems. Although a significant fraction of phosphorus (P) entering rivers is retained in riverine sediments, fluctuation of physiochemical and biological conditions may promote remobilization of the retained P and its removal to open waters. This study aimed to quantify the amount of inorganic phosphorus (Pi) that can be released from the selected sections of East Creek in the Chesapeake Bay watershed. Environmental parameters chosen to identify Pi release included changes in biological activity, redox potential, pH, salinity, and temperature. Pi released from sediment spiked with Shewanella putrefaciens CN32 varied from 1.42 μmol/g along the lower reaches of the creek to 5.08 μmol/g near the agricultural headwaters. Changing the ambient water column pH (7.4) to acidic (6.0) condition resulted in the retention of dissolved Pi while changing to basic (9.0) condition promoted release of Pi. Similarly, increase in salinity and temperature also resulted in Pi release. Pi flux at the sediment-water interface from field simulated experiments varied from 14.8 μmol/m²‒hr along lower reaches to 48.6 μmol/m²‒hr near agricultural headwaters. High Pi release in the upstream section of the creek was consistent with the high sediment and water column Pi near the agricultural field. Statistical analyses indicated that the enhanced biological activity and pH were the most sensitive parameters affecting Pi release from the sediment. A regression equation developed to approximate the amount of Pi release in the worst case scenario in East Creek was 0.30 μmol/g at the salinity of 15 PSU, 0.38 μmol/g at 25°C, 0.83 μmol/g at pH 9.5, and 3.10 μmol/g under enhanced biological condition. These results collectively suggest that the remobilization of P from the East Creek could be a new source to be exported to the Chesapeake Bay.
Mobilization , Phosphorous , Sediment , Chesapeake Bay Watershed