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The role of adsorption in sediment‐water exchange of phosphate in North Sea continental margin sediments
Author(s) -
Slomp C. P.,
Malschaert J. F. P.,
Van Raaphorst W.
Publication year - 1998
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1998.43.5.0832
Subject(s) - adsorption , sediment , sedimentary depositional environment , desorption , geology , flux (metallurgy) , phosphate , continental margin , sedimentary rock , water column , sediment–water interface , environmental chemistry , oceanography , geochemistry , environmental science , mineralogy , chemistry , geomorphology , paleontology , organic chemistry , tectonics , structural basin
The effect of adsorption on the sediment‐water exchange of PO 4 was investigated in sediments from four different types of sedimentary environments in the southern and eastern North Sea in August 1991 and February 1992. Nonlinear adsorption isotherms for oxidized sediment from eight stations indicate that North Sea sediments differ widely in their capacity to adsorb PO 4 . A good correlation between the value of the adsorption coefficient and NH 4 + oxalate‐extractable Fe was observed. A combination of the adsorption data with Porewater PO 4 profiles, solid phase results, and measured and calculated rates of sediment‐water exchange of PO 4 for 15 stations in both August and February indicates that adsorption plays an important role in controlling sediment‐water exchange of PO 4 during at least a part of the year in three of the four North Sea environments. At most stations, PO 4 adsorption constrains the flux of PO 4 to the overlying water. At one station in the depositional environment of the Skagerrak, however, desorption is responsible for the maintenance of a flux of PO 4 to the overlying water. A one‐dimensional reactiondiffusion model, describing Porewater PO 4 and solid phase P profiles, was developed and applied to results for two stations. The model results show that both enhanced retention and enhanced release of PO 4 can be adequately described when simultaneous equilibrium and first‐order kinetic reversible adsorptive reactions are assumed.