The Application of Soil Amendments to the Retardance of Rainwater-Leached Metals from CCA-Treated Wood Ash in Soil

The burning of wood treated with chromated copper arsenate (CCA) produces an ash that contains high concentrations of copper; chromium, and arsenic. The subsequent leaching of these metals front burn sites can produce soil and water contamination. Soils have varying natural abilities to reduce leaching and impact metals speciation and toxicity by sorption, conversion, and sedimentation-related mechanisms. Recent regulations have resulted in increased quantities of CCA-treated lumber entering the waste stream, making the study of metals leaching from ash, and the amendment of soils to more effectively immobilize metals, important areas of investigation. The performance of various soil amendments to immobilize or retard Cu, Cr and As species in soil/CCA-ash mixtures was studied. The amendments evaluated were agricultural lime (CaCO(3)/MgCO(3)), soil softener (CaSO(4) center dot 2H(2)O), and iron sulfate (FeSO(4)). Results of this investigation show that native soil alone retards the mobility of As and Cr, amendments applied alone or in combinations further retard metal mobility compared to the control soil/CCA-ash mixture. The CaSO(4) soil amendment is most effective in reducing the rainwater leaching of Cr and As from CCA-ash in soil reducing the mobility by 72.4% and 77.3%, respectively, compared to the control soil-ash mixture. Cu mobility is increased in the presence of the native soil and by all amendments.