An experimental study of the environmental impacts of CCA-treated wood waste land application
Mercer, T. G. (Theresa G.)
Thesis or dissertation
- © 2010 Theresa Mercer. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.
Chromated copper arsenate (CCA) has been the most commonly used wood preservative in the UK; up until its partial ban in 2004. The preservative prolongs the service life of wood by 20-50 years by making it resistant to biological attack. As such, in-service CCA treated wood is expected to be a major component of the UK wood waste stream in the future. Concerns over the impact of the chemical constituents of this treatment on both the environment and human health have prompted the introduction of legislation to ensure that such waste is disposed of safely in Hazardous Waste Landfills. Despite this, studies have shown that this waste can still enter into the landscape mulch market due to inadequate detection methods and increasing societal pressures to recycle.
A series of laboratory and field-based simulations were used to quantify leaching of copper, chromium and arsenic from CCA-treated wood waste mulch and evaluate the factors involved in promoting leaching. The distribution and behaviour of the metals in the soil column and leachate were also assessed. The samples generated in the study were analysed for a range of physico-chemical measurements, elemental and speciation concentrations.
Results show that arsenic, chromium and copper leaches from CCA waste wood; at times to levels exceeding regulatory thresholds by two to three orders of magnitude. Furthermore, the more toxic and mobile species of arsenic (As III) and chromium (Cr VI) were detected in both soil and leachate samples. A mass balance was produced which demonstrated that CCA wood tends to leach on initial exposure to a leachant and also during weathering of the wood. When in contact with soil, metal(loid) transport is reduced due to complexation reactions. With higher water application or where the adsorption capacity of the soil is exceeded, the metal(loid)s are transported through the soil column as leachate. Overall, there was a loss of metal(loid)s from the system that could be due to loss of water, volatilisation of arsenic and plant uptake. Due to the toxicity and concentration levels of the leached elements identified in the current study, it is apparent that adverse environmental and human health impacts may result from direct and indirect exposure to the environmental media.
- Department of Geography, University of Hull
- Frostick, L. E.; Adams, John D.; Ellis, S. (Stephen)
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