COMPARISON OF THE UPTAKE OF INORGANIC PHOSPHORUS TO A SUSPENDED AND STREAM BED SEDIMENT

Results are presented describing the influx of soluble reactive phosph orus (SRP) to a stream sediment in an outdoor experimental channel, a laboratory channel and in well-mixed suspensions. The kinetics of phos phorus uptake are modelled using several kinetic equations including t he Elovich, Bangham, diffusion and first-order equation. The Elovich e quation is found to describe best the SRP influx to both bed and suspe nded sediments. The relative contribution of abiotic and biotic proces ses in the outdoor experimental channel are considered together with e stimates of the flux to the bed-sediment predicted from the results de scribing the kinetics in the laboratory channel. The sediment is chara cterized by mineralogy, size fractionation and wet-chemical analyses i ncluding total phosphorus, iron and calcium determinations as well as biologically available phosphorus (BAP) by the iron-oxide stripping me thod and the equilibrium phosphate concentration, EPC(0), calculated f rom sorption measurements. The kinetic results from this sediment illu strate the importance of suspended sediment in the fast uptake of SRP. This contrasts with the control of the influx of SRP to the bed-sedim ent in channels with low concentrations of suspended solids, caused by the rate-limiting diffusional transfer across the sediment-water inte rface.