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Form and toxicity of copper released into marine systems from conventionally and nano-sized copper treated lumber
Citation:
Parks, Ashley, M. Cashman, S. Fogg, M. Cantwell, D. Katz, K. Ho, AND R. Burgess. Form and toxicity of copper released into marine systems from conventionally and nano-sized copper treated lumber. Society of Environmental Toxicology and Chemistry (SETAC) 37th Annual Meeting, Orlando, FL, November 06 - 11, 2016.
Impact/Purpose:
In this work, the goal was to determine the rate, concentration, and form of copper released from commercially available pressure treated lumber samples (blocks and sawdust) exposed to an aqueous system. Overall these results suggest that the form of copper released from treated lumber is ionic and that little nanocopper is present in the aqueous phase. This finding suggests the risk associated with nanocopper treated lumber can be addressed with existing copper ion-based modeling approaches and regulations.
Description:
The fate and effects of pristine engineered nanomaterials (ENMs) in simplified systems have been widely studied; however, little is known about the potential release and impact of ENMs from consumer goods, especially lumber that has been treated with micronized copper. Micronized copper solutions contain copper complexes predominately in the 10-700 nm size range, and are used in lumber to prevent microbial degradation and fouling. In this work, the goal was to determine the rate, concentration, and form of copper released from commercially available pressure treated lumber samples (blocks and sawdust) exposed to an aqueous system. Lumber tested included Southern Yellow Pine (SYP) treated with micronized copper azole (MCA) at 0.96 and 2.4 Kg/m3, alkaline copper quaternary (ACQ) at 0.30 and 9.6 Kg/m3, and chromated copper arsenate (CCA) at 40 Kg/m3. Of the different chemical treatments, only MCA included nano- and micro-sized copper complexes. The experimental system included wood cubes cut from the outer 2 cm surface of the lumber or the equivalent mass (4 g) of sawdust submerged in 250 mL of media (0, 1, 10, and 30 ppt filtered natural seawater) in polyethylene bottles, and mixed on a shaker table at 120 rpm. Water samples were taken at 8 hours, and on days 1, 2, 7, 14, and 28 for the blocks and days 1, 2, 3, 7, 17, and 28 for the sawdust. Subsamples included unfiltered water (defined as 0.45 µm - filtered water for the sawdust), and water filtered through a 0.1 µm polyethersulfone (PES) syringe filter, and a 3000 Dalton centrifugal filter, which were analyzed using ICP-AES to determine the total, nano+ionic copper (< 0.1 µm subsample), and approaching ionic copper (<3 KDa subsample). Results for the blocks showed that all treatments reached a steady state of copper release. Lumber treated with higher copper concentrations released more copper into the water, and all treatments released ionic copper rather than particulate copper (nano or micro). The sawdust released copper as a pulse input rather than gradually. Ion selective electrode measurements and the magnitude of toxicity to marine mysids (Americamysis bahia) were used to confirm the results of the size-based analyses for the 0 and 30 ppt treatments, respectively. Overall these results suggest that the form of copper released from treated lumber is ionic and that little nanocopper is present in the aqueous phase. This finding suggests the risk associated with nanocopper treated lumber can be addressed with existing copper ion-based modeling approaches and regulations.