Barbara Samartini Queiroz Alves, University of California-Davis, Davis, CA, William R. Horwath, One Shields Avenue, University of California-Davis, Davis, CA and Sanjai J. Parikh, Department of Land, Air and Water Resources, University of California-Davis, Davis, CA
Cadmium (Cd) is a heavy metal that can be toxic for living beings at very low concentrations,and thus can pose food safety concerns. Some soils within California’s Salinas Valley,whereleafy vegetables arecommonly grown, are enriched in geocenic Cd.Onesolutionto reduce plant uptake may besoil amendments of biochar, a carbon rich material producedby thermal converstion, that can adsorb a variety of pollutants, including Cd.However, not enough is known regarding the specific binding mechanisms involved, and how Cd retentionwill change over time, which are essential information for selecting and optimizingbiochars.This research aims toidentify trends between feedstock and pyrolysis temperature and Cd retention, identify main surface characteristics,andevaluate the adsorption and desorption over time.We hypothesize:(i) there is anoptimal relationshipbetween surface area and functional groups to obtain maximum adsorption; (ii)the effect of time on adsorption can either be rising with the increasing content of functional groups derived by surface oxidation, anddecreasing with reduction of surface area due to physical break down and steric effects which limits the diffusion of Cd into internal pores.A preliminary set of 9 raw biochars and 8 modified biochars (with post-treatments) wereexanimated regarding their Cd adsorptive capacities and five were selected for furtherevaluation. Laboratory aging experiments will be evaluated with acid washing treatments. Next, a series of batch sorptionexperiments will compare retention rates between fresh and aged biochars. If results are promising, data from this study will be used todevelop soil management strategies to ensure safe production of leafy green crops in soil with elevatedCd levels.