Phosphorus readsorption on Occoquan sediments

The purpose of this investigation was to determine the extent of phosphorus readsorption on Occoquan sediments and the amount of subsequent removal because of settling of the particles with time. Occoquan sediments were placed in six polyurethane cylinders and submerged. In two separate experiments, the cylinders were driven anaerobic, which allowed phosphorus, previously bound in the sediments, to release. The sedimentâ water system was then reaerated and mixed with a porous air diffuser. Analyses were conducted before and after the mixing period.

From the results obtained, the following conclusions were drawn: phosphate readsorption occurred upon mixing the system, and as the turbidity decreased, the phosphate concentration decreased; phosphate readsorption occurred in a two-step process; each suspension tended toward equilibrium after mixing; interstitial waters contributed significant amounts of phosphorus upon mixing of the sediment-water systems; Occoquan sediments released variable amounts of phosphorus even within samples from similar sites; sediments from the Occoquan Creek arm contained less phosphorus than Bull Run sediments; and sediments low in phosphorus concentrations removed greater amounts of phosphorus in a shorter period of time.