Plant Accumulation and Soil Sorption of Cobalt from Cobalt‐Amended Soils1

Abstract

AbstractPresent industrial uses of Co result in elevated metal concentrations in soils around industrial activities and land treatment facilities. Laboratory and greenhouse studies were conducted to determine Co uptake by tall fescue (Festuca arundinaceaSchreb.) as affected by soils, Co levels, lime additions, Mn additions, and soil layering. In a laboratory sorption study using solutions containing 5 to 1000 mg Co L−1, the Marietta (Aquentic Dystrochrepts) and Norwood (Typic Udifluvent) soils had sorption maxima of 1440 and 3787 mg Co kg−1, respectively. The higher sorption of the Norwood soil was presumably due to the formation of complexes or precipitates between the CaCO3and Co. Addition of up to 6.7 Mg lime ha−1resulted in decreased concentrations of Co in tall fescue grown in soils containing 400 mg Co kg−1. Addition of 50 to 2000 mg MnO2kg−1soil had no effect on Co accumulation by tall fescue. Layering of uncontaminated soil over Co‐amended soil increased plant uptake of Co over that taken up by plants grown in Co‐amended soil alone. Apparently, the healthy roots in the upper layers of soil removed Co from the lower layers of soil; whereas, elevated Co in the total soil volume retarded root development sufficiently to prevent Co uptake. Total Co determinations were as good as or better than any of the three extractants (2.5% acetic acid, 0.01 MEDTA [ethylenediamine tetracetic acid] and DTPA‐TEA [diethylenetriamine pentacetic acidtriethanolamine]) in predicting plant accumulation of Co. Of the tested extractants, acetic acid had the lowest correlation coefficient when compared with plant Co accumulation.