Effect of deposit feeders on migration of137Cs in lake sediments
| Autor: | J. Berton Fisher, John A. Robbins, Peter L. McCall, John R. Krezoski |
|---|---|
| Rok vydání: | 1979 |
| Předmět: |
Molecular diffusion
Pontoporeia biology Analytical chemistry Detritivore Sediment engineering.material biology.organism_classification Geophysics Adsorption Benthos Space and Planetary Science Geochemistry and Petrology Tubifex tubifex Illite Earth and Planetary Sciences (miscellaneous) engineering Geomorphology Geology |
| Zdroj: | Earth and Planetary Science Letters. 42:277-287 |
| ISSN: | 0012-821X |
| DOI: | 10.1016/0012-821x(79)90035-9 |
| Popis: | Illite clay particles with adsorbed 137 Cs were added as a submillimeter layer to the surface of silt-clay sediments contained in rectangular Plexiglas cells stored in a temperature-regulated aquarium, in order to trace the effect of the oligochaete, Tubifex tubifex , and the amphipod, Pontoporeia hoyi , on mass redistribution near the sediment-water interface. A well-collimated NaI gamma detector scanned each sediment column (∼10 cm deep) at daily or weekly intervals for six months, depicting the time evolution of radioactivity with and without added benthos. In a cell with tubificids (∼5 × 10 4 m −2 ), which feed below 3 cm and defecate on surface sediments, the labeled layer was buried at a rate of 0.052 ± 0.007 cm/day (20°C). When labeled particles entered the feeding zone, 137 Cs reappeared in surface sediments creating a bimodal activity profile. In time, the activity tended toward a uniform distribution over the upper 6 cm, decreasing exponentially below to undetectable levels by 9 cm. In a cell with amphipods (∼1.6 × 10 4 m −2 ) uniform activity developed rapidly (∼17 days) down to a well-defined depth (1.5 cm). The mixing of sediments by Pontoporeia is described by a simple quantitative model of eddy diffusive mixing of sediment solids. The value of the diffusion coefficient, 4.4 cm 2 /yr (7°C) was computed from a least squares fit of theoretical to observed profile broadening over time. In a cell without benthos, small but measurable migration of 137 Cs indicated an effective molecular diffusion coefficient of 0.02 cm 2 /yr. |
| Databáze: | OpenAIRE |
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