Pentachlorphenol migration from treated wood exposed to simulated rainfall

Abstract

The leaching of toxins from treated wood poses an, as yet, poorly quantified risk to both plant and animal life. In particular, the leaching of pentachlorophenol (PCP) into rainwater falling on treated wood over aquatic environments, such as bridges, is understudied. Computer models have been developed which predict the leaching of creosote from marine pilings. If data were available, similar models could be developed for PCP-treated bridges and the risk to waterways determined for various structural designs. Providing such data is the objective of this study, where the migration of PCP from treated wood under the influence of simulated rainfall was studied using a simulation system that delivered uniform rainfall rates over-treated wood. The runoff from the treated wood was captured and analyzed with high resolution gas chromatography combined with low resolution mass spectrometry. PCP migrated from treated wood into rainwater runoff at a fairly constant rate of approximately 0.15 g l-1 m-2. Small non-significant deviations were observed with rainfall rate, time, and temperature. We suggest that PCP migration rates from exposed treated wood can be modeled and thereby predict the migration of PCP from this source into the environment.

Effect of post-treatment processing on copper migration from Douglas-fir lumber treated with ammoniacal copper zinc arsenate

“…1). Previous studies (Simonsen et al, 2008) showed that preservative migration was independent of both temperature and Fig. 1.…”

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

“…At faster rates of rainfall the water would have less contact time with the wood, and a higher proportion of water would run-off the specimens without causing leaching. The lack of effect of rainfall rate observed in an earlier laboratory study (Simonsen et al 2008) may be a function of the type of preservative, wood species or study methodology. That study evaluated an oil-based preservative (pentachlorophenol) applied to Pseudotsuga menziesii (Douglas-fir), a wood species with limited permeability.…”

“…When expressed on the basis of mass of preservative leached per unit rainfall, greater amounts of biocide appear to be released at slower rainfall rates (Cockroft and Laidlaw 1978, Cooper 2003, Evans 1987, presumably because the wood is wetted for a longer period and a greater proportion of the rainfall is absorbed by the wood. However, one laboratory study found that rate of rainfall had little effect on leaching of pentachlorophenol from pressure-treated wood (Simonsen et al 2008). In addition, the interval between rainfall events has been reported to influence leaching, with greater amounts leached after longer resting periods.…”

“…The rainfall rates evaluated also differed, with the lowest rainfall rate evaluated in that study (20 mm/h) approximately equivalent to the highest rainfall rate evaluated in the research reported in this paper. Specimens in the Simonsen, et al 2008 study had also been pre-leached prior to rainwater exposure in an effort to simulate release from weathered wood. The role of rainfall rate in leaching from wood after extended exposure may warrant further evaluation.…”

Effect of post-treatment steaming on preservative migration from pentachlorophenol-treated wood

“…The rainfall struck the wide face of a sample and then flowed into a container for collection. Previous studies (Simonsen et al 2008) have shown PCP migration to be independent of both temperature and rainfall rate so the device was operated at room temperature (20-28°C) and a rainfall rate ranging from 0.1 to 0.3 cm h −1 .…”