TY - JOUR

T1 - An investigation of the effects of water velocity on inorganic phosphorus influx to a sediment

AU - House, W. A.

AU - Denison, F. H.

AU - Smith, J. T.

AU - Armitage, P. D.

N1 - Funding Information:
The authors thank Mrs S. Smith for assistance with the phosphate analysis, Mr S. Martin for help with the invertebrate counting and the Natural Environment Research Council, UK, for funding this work.

PY - 1995/9/1

Y1 - 1995/9/1

N2 - Measurements of the net influx of soluble reactive phosphorus (SRP), to a river bed-sediment, illustrate the importance of the water velocity and hydrodynamics in controlling the transfer rates. Experiments are reported using a characterised bed-sediment, with associated fauna, contained in a flowing-water channel. The results show a systematic increase in the net influx of SRP with increasing water velocity. A mathematical description of the influx was sought by modelling the experimental results using the Elovich equation, a boundary-layer model and a parabolic rate equation. In fact all three kinetic equations produce a good representation of the experimental data and it is concluded that further research is needed, in well-defined hydrodynamic conditions, to distinguish between the boundary-layer model and the parabolic equation. The boundary-layer model leads to an inverse relationship between the boundary-layer thickness (z/μm), and the water velocity (v/cm s-1, viz z ≈ 2500/v). In comparison, the parabolic equation of the form: influx of SRP (μmol m-2 = kp [SRP-EPC0]2, where EPC0 is the concentration at which the influx is zero prior to the sorption of phosphorus by the sediment and kp is the rate constant which leads to a velocity dependence, kp* = 0·714v + 1 where kp* is the reduced rate constant, kp* = kp(v)/kp(0). The semi-empirical Elovich equation in the form: influx of SRP (μmol m-2) = ( 1 b) ln(1 + abt) where a and b are the Elovich parameters and t the time, gives a convenient description of the net influx of SRP to bed-sediments downstream of a point-source of pollution. The parameters calculated from the results obtained from the experimental channel are used to estimate the SRP flux to the sediment for a distance of up to 5 km downstream of a point-input of SRP.

AB - Measurements of the net influx of soluble reactive phosphorus (SRP), to a river bed-sediment, illustrate the importance of the water velocity and hydrodynamics in controlling the transfer rates. Experiments are reported using a characterised bed-sediment, with associated fauna, contained in a flowing-water channel. The results show a systematic increase in the net influx of SRP with increasing water velocity. A mathematical description of the influx was sought by modelling the experimental results using the Elovich equation, a boundary-layer model and a parabolic rate equation. In fact all three kinetic equations produce a good representation of the experimental data and it is concluded that further research is needed, in well-defined hydrodynamic conditions, to distinguish between the boundary-layer model and the parabolic equation. The boundary-layer model leads to an inverse relationship between the boundary-layer thickness (z/μm), and the water velocity (v/cm s-1, viz z ≈ 2500/v). In comparison, the parabolic equation of the form: influx of SRP (μmol m-2 = kp [SRP-EPC0]2, where EPC0 is the concentration at which the influx is zero prior to the sorption of phosphorus by the sediment and kp is the rate constant which leads to a velocity dependence, kp* = 0·714v + 1 where kp* is the reduced rate constant, kp* = kp(v)/kp(0). The semi-empirical Elovich equation in the form: influx of SRP (μmol m-2) = ( 1 b) ln(1 + abt) where a and b are the Elovich parameters and t the time, gives a convenient description of the net influx of SRP to bed-sediments downstream of a point-source of pollution. The parameters calculated from the results obtained from the experimental channel are used to estimate the SRP flux to the sediment for a distance of up to 5 km downstream of a point-input of SRP.

UR - http://www.scopus.com/inward/record.url?scp=0028988708&partnerID=8YFLogxK

U2 - 10.1016/0269-7491(94)00071-K

DO - 10.1016/0269-7491(94)00071-K

M3 - Article

AN - SCOPUS:0028988708

SN - 0269-7491

VL - 89

SP - 263

EP - 271

JO - Environmental Pollution

JF - Environmental Pollution

IS - 3

ER -