Effects of incubation time and filtration method on Kd of indigenous selenium and iodine in temperate soils

Publication date: October 2017
Source:Journal of Environmental Radioactivity, Volume 177
Author(s): T. Almahayni, E. Bailey, N.M.J. Crout, G. Shaw
In this study, the effects of incubation time and the method of soil solution extraction and filtration on the empirical distribution coefficient (Kd) obtained by de-sorbing indigenous selenium (Se) and iodine (I) from arable and woodland soils under temperate conditions were investigated.Incubation time had a significant soil- and element-dependent effect on the Kd values, which tended to decrease with the incubation time. Generally, a four-week period was sufficient for the desorption Kd value to stabilise. Concurrent solubilisation of soil organic matter (OM) and release of organically-bound Se and I was probably responsible for the observed decrease in Kd with time. This contrasts with the conventional view of OM as a sink for Se and I in soils. Selenium and I Kd values were not significantly affected by the method of soil solution extraction and filtration.The results suggest that incubation time is a key criterion when selecting Se and I Kd values from the literature for risk assessments. Values derived from desorption of indigenous soil Se and I might be most appropriate for long-term assessments since they reflect the quasi-equilibrium state of their partitioning in soils.



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