The extent and significance of bioturbation on Cs-137 distributions in upland soils

Differences between measured Cs-137 activity-depth profiles and idealised u ndisturbed profiles generated from an exponential model suggest that faunal turbation has redistributed Cs-137 in mineral and organic upland soils in southern Scotland, Bioturbation is also demonstrated by the vertical displa cement of other inputs to the soils of known age (non-native tree pollen an d spheroidal carbonaceous particles, SCPs). The causes and mechanisms of bi oturbation were Further investigated by soil micromorphology. Well-drained mineral soils with active populations of earthworms are the most bioturbate d, showing near-complete homogenisation to depths of about 20 cm. Enchytrae ids also seem to remobilise Cs-137 by the digestion of organic matter and m ay be the main cause of Cs-137 redistribution in organic-rich upland soils. Relative rates of mixing are evaluated by comparing Cs-137 depth profiles. (C) 2001 Elsevier Science B.V. All rights reserved.