Leaching of heavy metals from chromated copper arsenate (CCA) treated wood after disposal Azita H. Moghaddam, Catherine N. Mulligan * Department of Building, Civil and Environmental Engineering, Concordia University, 1455 de Maisonneuve Boulevard W., EV 006-187, Montreal, QC, Canada H3G 1M8 Accepted 19 March 2007 Available online 17 May 2007 Abstract Wood treated by preservatives is commonly found in solid waste. Among the different types of preserved wood, chromated copper arsenate (CCA) treated wood recently has received much attention due to the scale of usage and its significant role in soil and water contamination. As the ash of CCA treated wood would be hazardous if the wood were to be incinerated, this is not a good alternative, and the best available disposal method is thus landfilling in the US, Canada and Australia. Leaching of the metals from preserved wood that is disposed in unlined landfills for construction debris pollutes the soil and water environments. Several factors affecting leaching of the metals from wood, including pH of the leachant, temperature, the duration of leaching and the type of leachant, were investigated. These factors affect each of the metals, chromium, copper and arsenic, differently. A comparison of these effects on each metal was per- formed. The results of the experiments showed that the pH of the leachants has a significant effect on the leaching process, and sulfuric acid (pH 3) is the most effective leachant compared to nitric and acetic acid (pH 3-4-5). The amounts of leached chromium, copper and arsenic by sulfuric acid (pH 3) during 15 days were, respectively, 0.2, 0.14 and 0.15 mg more than leachates by nitric acid (pH 5) on the basis of 1 g of wood (initial contents of 1.03 mg, 0.42 g and 0.8 mg per g of wood). Most of the leaching occurs in the first 5 days, and the rate of leaching decreases significantly after 5 days. Increasing temperature increases the amount of leached metals, and arsenic is the least resistant metal to the leaching when the temperature increases. Increasing the temperature from 15 °C to 35 °C during 15 days increases the amount of leached chromium, copper and arsenic by acetic acid at pH 5 by about 0.1, 0.4 and 1.2 mg per g of wood, respectively. Ó 2007 Elsevier Ltd. All rights reserved. 1. Introduction Today, municipal solid waste management has become an important part of environmental protection activities. In 2003, the US produced more than 236,000 million kg of municipal solid waste, of which 30% was recycled and the rest was disposed of by landfilling or composting (US EPA, 2006). In Canada, even though the population is less, the same problem exists. As there are some limitations for the types of wastes that can be recycled or combusted, landfilling is an important method of municipal and con- struction debris waste management (Ress et al., 1998). Following wood removal from the forests, several types of deterioration by fungi and insects threaten the untreated wood and reduce the lifetime of the wood and the wooden building materials. Chemicals are utilized to treat the wood to protect wood against bacterial, fungal, and insect attack. Chemical treatment has been practiced for centuries and is intended to enhance wood durability, and thereby increase the life expectancy of wood in service. As an example, rail- road cross ties that are used in North America would have an average lifetime of 5 years without treatment (Konase- wich and Henning, 1998), whereas the lifetime of most cre- osote preserved wood is estimated to be 30 years (Webb, 1990). In Florida, it has been found that up to 30% of the 0956-053X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2007.03.009 * Corresponding author. Tel.: +1 514 848 2424x7925; fax: +1 514 848 7965. E-mail address: mulligan@civil.concordia.ca (C.N. Mulligan). www.elsevier.com/locate/wasman Available online at www.sciencedirect.com Waste Management 28 (2008) 628–637