Phosphorus dynamics in a lowland river

Seasonal changes in the concentration of phosphorus and other nutrients along a section of the river Wey in southern England are reported. Measurements of the water chemistry upstream and downstream of a point-discharge together with the analysis of surface bed-sediments indicates the accumulation of phosphorus in surface sediments in the spring and summer followed by a decrease in the autumn and winter. The profiles of soluble reactive phosphorus (SRP) concentration along a stretch of river are modelled by simulating the net loss of SRP using the Elovich equation and a parabolic equation. The model utilizes results from measurements of the uptake of phosphorus by bed-sediments in a laboratory fluvarium channel. The channel was also used to measure the uptake of phosphorus and release from bed-sediments to overlying anoxic water. The measured net loss of SRP in the spring survey is much greater than expected from the uptake by the bed-sediment alone. The net phosphorus uptakes measured in the summer and autumn surveys are much less, and in closer agreement with the simulated data.