Release of copper, chromium, and arsenic from treated southern pine exposed in seawater and freshwater

The use of chromated copper arsenate (CCA -C) treated wood in marine construction has drawn criticism from environmentalists because of the high levels of chemical concentration in the wood and the potential for harm to aquatic life. These criticisms have been difficult to address because of the lack of, or conflicting, information on the release of chemical elements of CCA-C into seawater. In this study, sections of lumber and piling were treated with CCA-C to retention levels of 20 or 40 kg/m3 and immersed for 15 months in deionized water and dilutions of an artificial seawater solution. The leaching solutions were periodically collected and analyzed for the concentration of released copper, chromium, and arsenic. Seawater had a mixed effect on leaching of the elements of CCA-C. The steady-state release rate of copper was much greater in seawater than in deionized water. In contrast, the steady-state release rate of arsenic was somewhat greater in deionized water than in seawater. The rate of chromium release was consistently much less than that of copper and arsenic and did not appear to be affected by seawater. Release rates of copper and arsenic were somewhat less from the wood treated to 20 kg/m3 than from the wood treated to 40 kg/m3, but retention had little effect on the rate of chromium release. Release rates per unit surface area were consistently greater from piling than from lumber, especially for arsenic. Long-term release of CCA-C elements was estimated from steady-state release rates that occurred after 10 to 15 months of leaching.

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