Environmental Impacts of CCA-Treated Wood Within Florida, USA

Studies in Florida, USA, focusing on the environmental impacts of wood treated with chromated copper arsenate (CCA) were initiated because of elevated levels of arsenic and chromium encountered in ash from wood cogeneration plants within the State. During 1996 it was determined that these elevated levels were due to contamination of wood fuel with discarded CCA-treated wood. Since this time, a research team from the University of Miami and the University of Florida have been evaluating: a) disposal pathways for CCA-treated wood within the State, b) new disposal management strategies for CCA-treated wood, and c) impacts of CCA-treated wood during its inservice use. In-service leaching was evaluated through two focused efforts. These efforts included a study that characterized metal concentrations in soils below 9 pre-existing decks (8 CCA treated and 1 not CCA treated) and a controlled field-scale experiment where 2 decks (one CCA treated and one untreated) were constructed over a leachate collection system. Immediately below the pre-existing decks the average soil arsenic concentration was 28.5 mg/kg. This was contrasted by a value of 1.5 mg/kg for the background samples. Arsenic concentrations in runoff collected from a CCA-treated deck ranged from 0.1 to 8.4 mg/L with 0.7 mg/L, on average. Arsenic in the runoff was predominately in the +5 valence; however, some As(III) was measured. Detectable amounts of arsenic were also measured in the infiltrated water below the sand supporting the decks. A larger fraction of As(III) was observed in the infiltrated water as compared to the runoff water. Disposal pathways for CCA-treated wood within Florida include construction and demolition (C&D) debris landfills (which are generally unlined in Florida) and inadvertent mixing with mulch and wood fuel that is produced from recycled C&D wood. Leaching test results demonstrate that CCA-treated wood leaches enough arsenic to cause the wood to be a toxicity characteristic (TC) hazardous waste (if it were not otherwise exempted) and to pose a potential risk for contaminating