Diffusion of potentially toxic elements from CCA-treated wood into layey and sandy Brazilian soils

Reforestation wood treated with chromated copper arsenate (CCA) has been a source of soil pollutants. The planar source diffusion method was used to assess the leaching of As, Cu, and Cr ions from CCA-treated wood into soil. The research focused on treated Pine and Eucalyptus wood in clayey and sandy soils. Gaussian fitting derived diffusion coefficients around 10^-12 m² s^-1 with the highest mobility for Cr(VI), followed by As(V) and Cu(II) in both soil types. A pilot experiment was conducted in plastic pots to simulate CCA diffusion from wood into the soil. The multidirectional ion mobility described by polar charts indicated Cu(II) with the highest mobility, followed by Cr(III/VI) and As(V). This behavior may be attributed to the interconversion of Cr(III/VI) species in the clayey soil (pH 6.10 and Eh 531 mV) and sandy soil (pH 4.55 and Eh 593 mV). A significant finding was the pronounced leaching of CCA in clayey soil, underscoring the influence of environmental features on pollutant dynamics. The results warn about the environmental contamination caused by the diffusion of PTE ions from CCA-treated wood into soils. Based on these findings, environmental regulations are anticipated to prompt the industry to develop more eco-friendly wood treatment methods. Environmental implications: This study highlights the leaching potential of chromated copper arsenate (CCA) in soil. As Brazil is a major food exporter, contamination of agricultural land due to the proximity to CCA-treated wooden structures could affect people across various countries. The research observes the mobility of potential toxic elements (PTE) from CCA into water-saturated soils, as well as the potential conversion of less toxic Cr(III) to the more toxic Cr(VI). This conversion significantly increases PTE's mobility and toxicity, which can disrupt the environmental balance. Consequently, the findings urge authorities to recognize the risks associated with CCA-treated wood and reconsider the existing regulations in Brazil.