Diffusive gradient in thin films (DGT) for profiling leaching of CCA-treated wood waste mulch into the soil environment

Abstract

Chromated copper arsenate (CCA) is a common wood preservative that has been used worldwide. Studies have shown that there are leaching risks of the preservative components arsenic, chromium and copper. These risks include contamination of soil and water, resulting in toxic effects to humans, animals, plants and ecosystems. This study investigates leaching of the preservative components following exposure of the wood waste as mulch to soil and water. Diffusive gradient in thin films (DGTs) were used to quantify leaching of potentially bioavailable/dissolved forms of the elements along the soil profile. Speciation of chromium was also carried out. All elements were found to leach out of the wood. The containers that included CCA-treated wood waste as a mulch leached higher levels of arsenic, chromium and copper than the controls. The distribution was highest in the top 5 cm of the soil profile and decreased with depth. DGTs proved to be a useful, novel technique for measuring in situ leaching and speciation from waste materials into the environment.

Keywords:

• chromated copper arsenate (CCA) treated wood waste
• DGT
• leaching
• soil pollution

Acknowledgements

The authors would like to thank the eight anonymous reviewers whose comments greatly improved the manuscript, Dr Hao Zhang (Lancaster University) for her help with using DGTs, Bob Knight (University of Hull) for help with the analyses and Dr David Sands (University of Hull) for reading through the draft versions. Funding for this work was provided by an EPSRC studentship.