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

Abstract

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.

Tsunami and Environmental Pollution Hazards: A Note for the Restoration Process

“…Likewise, this compound was widely used in Japan ; as arsenic was not present in the formula, ACQ contains a high copper concentration, much like CuAz. Copper-leaching has shown to be continuous from treated wood due to rainfall, albeit in lesser quantities as wood weathers (Hasan et al 2010 ).…”

“…Studies have shown that creosote's main elements continuously leach from weather-treated wood when washed with rainfall, having the highest loss rate of any chemical wood treatment (Hasan et al 2010 ). Considering that some of its compounds are highly mobile in soil, they could threaten resources (Schiøtz Hanse and Ottosen 2002 ) and a number of its constituents, notably the O-and N-heterocyclics, which exhibit appreciable solubility, may be transported over signifi cant distances via surface runoff or groundwater (Enzminger and Ahlert 1987 ).…”

Effect of precipitation pattern on leaching of preservative from treated wood and implications for accelerated testing

“…In addition, the interval between rainfall events has been reported to influence leaching, with greater amounts leached after longer resting periods. This type of effect has been attributed to the allowance for a longer period for soluble preservative components to diffuse to the surface from the interior of the wood products (Chung and Ruddick 2004, Hasan et al 2010, Ruddick 2008, Tao et al 2013, Taylor and Cooper 2005. At least one study, however, found little relationship between the length of the interval between rainfall events and the subsequent concentrations of preservative metals in leachate (Morrell et al 2010).…”

“…Field leaching tests indicating that time between rainfall events influences leaching have been conducted over longer times periods, and included longer periods between rainfall events (Chung and Ruddick 2004, Hasan et al 2010, Taylor and Cooper 2005. Time is required for mobilized preservative components to diffuse through the wood to the surface, and although the volume of rainfall was similar to a year of exposure, the length of time for diffusion of mobilized components through the wood was shorter than that of a specimen exposed for a year outdoors.…”

“…In the past, much interest in preservative leaching and environmental impact was focused on treated wood that was immersed in water, such as marine piles. In most structures however, the greatest proportion of treated wood is not in direct contact with soil or standing water, and more recently the need to characterize emissions from treated wood used above-ground or above water has been recognized (Hasan et al 2010, Tao et al 2013.…”