Diffusive Gradient in thin film technique as tool for assessment of metal availability and kinetics of resupply in remediated soils

Abstract

This study focussed on the efficacy of two treatments, commercial-hardwood biochar and Delonix regia pods biomass, an agricultural waste, as amendment to tropical soils contaminated with lead, copper and cadmium ions; the use of Diffusive Gradient in Thin Films Technique (DGT) and measurement of soil solution concentration as means to assess the available concentration of the metals, lead, copper and cadmium ions, during and after the remediation treatment was carried out. Furthermore, Soil dynamics predicted from values of the labile partition coefficient (Kd), response time to depletion (Tc) and rates of exchange or desorption (k-1) of metal ions between soil solid phase and soil solution were also obtained using the DGT-induced fluxes in soils (DIFS) model.The heavy metal labile pool size in the soil and their kinetics of resupply in the biochar and Delonix regia amended soils were determined. The experimental results showed that the biochar-treated soils have the highest distribution coefficient, Kd, values in all the soils and for all metals considered. The depletion time (Tc) and desorption rate constant, k-1, values also revealed that the biochar treated soils would be depleted faster than the Delonix regia treated soils. Thus results from this work has shown that dynamics of metals in soils should be considered after treatment of contaminated soils.