Soil affects the bioavailability and toxicity of trace element (TE) contaminants. Bioassays are often conducted on TE spiked soils. A key assumption is TE exposure is constant throughout the bioassay. Desorption of TE species controls exposure to many ecological receptors. We investigated the effect of post-spiking reaction time on desorption of As, Pb, Cd, Zn at bioassay time scales. Trace element availability, measured by 0.1 M Ca(NO3)2 extraction, was determined during 28 and 70 days periods which corresponded to earthworm and plant bioassays. Large decreases in TE desorption and availability (in parentheses) during bioassay were As (15-63%), Pb (3-28%), and Zn (21-44%). Time had little effect on Cd. The time required to achieve a pseudo-equilibrium of TE availability varied with soil type. The implications of irreversible desorption of TE by soil on derived soil bioavailability soil criteria will be presented. Probable sorption mechanisms will be discussed.

Trace element sorption reversibility and bioavailability during earthworm and plant bioassays

245th National Meeting (2013)

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