Field-scale leaching of arsenic, chromium and copper from weathered treated wood.

Earlier studies documented the loss of wood preservatives from new wood. The objective of this study was to evaluate losses from weathered treated wood under field conditions by collecting rainfall leachate from 5 different wood types, all with a surface area of 0.21 m(2). Wood samples included weathered chromate copper arsenate (CCA) treated wood at low (2.7 kg/m(3)), medium (4.8 kg/m(3)) and high (35.4 kg/m(3)) retention levels, new alkaline copper quat (ACQ) treated wood (1.1 kg/m(3) as CuO) and new untreated wood. Arsenic was found to leach at a higher rate (100 mg in 1 year for low retention) than chromium and copper (<40 mg) in all CCA-treated wood samples. Copper leached at the highest rate from the ACQ sample (670 mg). Overall results suggest that metals' leaching is a continuous process driven by rainfall, and that the mechanism of release from the wood matrix changes as wood weathers.