Citation:

Johnson, M.G., J. Reichman, T. Luxton, P. Rygiewicz, M.A. Bollman, G. King, M. Storm, AND C.P. Andersen. Transformation and Release of Micronized Cu Used as a Wood Preservative in Treated Wood in Wetland Soil. 27th Annual Meeting of Society of Environmental Toxicology & Chemistry, Corvallis, OR, March 08 - 10, 2018.

Impact/Purpose:

Engineered nanoparticles (ENPs) have been recognized as valuable components of novel technologies and are currently being used in a variety of consumer products due to their unique physical, chemical, and electrical properties. The properties that make these particles functionally unique also influence their behavior and interactions with biotic and abiotic components of the environment. One of the challenges scientists face when examining the potential environmental health and safety aspects of ENPs is to understand the underlying chemistry of these interactions in order to better predict and model potential adverse environmental effects. WED scientists are investigating micronized Cu (μ-Cu), which is used as a wood preservative, replacing toxic Chromated Copper Arsenates. One concern is that nano-sized Cu (n-Cu) may move out of the wood and into the soil, where it might adversely affect beneficial soil fauna and flora. WED scientists monitored the amount and form of Cu released into surface water and deep soil leachate and found that surface water Cu released from the treated wood reached maximum levels 3 days after stake installation and remained elevated. Sequential filtering of these solutions indicated that some of the Cu in solution was associating with soluble organics, but there was no evidence for free n-Cu in solution. After 5 months of exposure, XAS analysis indicated that Cu concentrations in the treated wood decreased, and increased in the adjacent soil. However, n-Cu from the treated wood was not found in the adjacent soil. These results indicate that Cu in the μ-Cu treated wood dissolves and leaches into adjacent wetland soil and waters primarily in ionic form (e.g., Cu2+) and not as nano-sized Cu particles. This research provides preliminary evidence that μ-Cu treated wood does not appear to be a source of n-Cu to the environment, and therefore may not present a unique exposure risk specific to nano forms of copper. This Abstract contributes to CSS10.04.

Description:

Micronized Cu (µ-Cu) is used as a wood preservative, replacing toxic Chromated Copper Arsenates. Micronized Cu is Malachite [Cu2CO3(OH)2] that has been milled to micron/submicron particles, many with diameters less than 100 nm, and then mixed with quat or azol biocides. In addition to concerns about the fate of the Cu from µ-Cu, there is interest in the fate of the nano-Cu (n-Cu) constituents as µ-Cu treated wood frequently contacts the ground. We examined movement of µ-Cu from treated wood after placing treated wood stakes into model wetland ecosystems. Release of Cu into surface water and deep soil leachate was monitored. After 5 months, Cu in thin-sections of treated wood and adjacent soil was localized and characterized with X-Ray Absorption Spectroscopy (XAS). Surface water Cu reached maximum levels 3 days after stake installation and remained elevated. Sequential filtering indicated that some of the Cu in solution was associating with soluble organics, but there was no evidence for n-Cu in solution. Deep leachate Cu levels were 10% of surface water levels at day 3 and increased gradually thereafter. Localization and speciation of Cu in the wood and adjacent soil using XAS, clearly indicated that Cu concentrations in the treated wood decreased, and increased in the adjacent soil. However, n-Cu from the treated wood was not found in the adjacent soil. These results indicate that Cu in the µ-Cu treated wood dissolves and leaches into adjacent wetland soil and waters primarily in ionic form (e.g., Cu2+) and not as nano-sized Cu particles.

Record Details: