The Calculation of Transport Coefficients of Phosphate and Calcium Fluxes Across the Sediment-Water Interface, from Experiments with Undisturbed Sediment Cores

• Published in: Water science and technology 1985-01, Vol.17 (6-7), p.941-951
• Main Authors: van Raaphorst, W., Brinkman, A. G.
• Format: Article
• Language: English
• Subjects: Calcium; Calcium phosphates; Coefficients; Cores; Diffusion layers; Dye dispersion; Experiments; Fluxes; Forces (mechanics); Mathematical analysis; Mud-water interfaces; Overlaying; Phosphates; Phosphorus; Pore water; Sampling; Sediment; Sediment-water interface; Sediments; Seepage
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.1985.0192

Fluxes of phosphate and calcium across the sediment-water interface of six undisturbed cores are investigated. Attention is paid to the accuracy of porewater extraction and the influence of this sampling upon the experiments. From this, it is concluded that sampling time should at least be one day. Continuous and batch experiments resulted in a rapid release of phosphorus and calcium from the sediment. The influence of induced seepage could not be shown. On a theoretical base, it is concluded that the benthic fluxes are fed by desorption at or just below the interface, rather than by diffusion from deeper layers. Hence, data of interstitial water could not directly be used for calculating the driving forces of these fluxes. Instead, endconcentrations in the overlaying water of the batch experiments are used, which resulted in values of transportcoefficients of 3–10.10−7 m.s−1, being in good agreement with theoretical as well as field data.