The Application of CaSO₄ Soil Amendment 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 a toxic ash that is highly concentrated with As, Cr and Cu metals. The subsequent leaching of these metals from 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. The goal of this research has been to determine the effectiveness of various soil amendments in the immobilization/retardance of As, Cr, and Cu species in ash produced from the burning of CCA-treated lumber, and enhance our understanding of the role of amendments in the leaching of As, Cr, and Cu metals in a soil contaminated with CCA-ash. Soil softener (CaSO₄ ⋅ 2H₂O) was evaluated for potential application as a low-cost method of reducing the mobility of these toxic metals. Results of the investigation shows that although the control host soil retards the mobility of As & Cr, the CaSO₄ soil amendment further retards metals mobility by (72.4% and 77.3%), respectively compared to the control soil-ash mixture. Cu mobility is increased by the presence of soil and by CaSO₄ amendment but at a much smaller mass rate.