Copper release and transformation following natural weathering of nano-enabled pressure-treated lumber

Ronald S Lankone; Katie Challis; Leila Pourzahedi; David P Durkin; Yuqiang Bi; Yan Wang; Michael A Garland; Frank Brown; Kiril Hristovski; Robert L Tanguay; Paul Westerhoff; Greg Lowry; Leanne M Gilbertson; James Ranville; D Howard Fairbrother

doi:10.1016/j.scitotenv.2019.01.433

Copper release and transformation following natural weathering of nano-enabled pressure-treated lumber

Sci Total Environ. 2019 Jun 10:668:234-244. doi: 10.1016/j.scitotenv.2019.01.433. Epub 2019 Feb 27.

Authors

Affiliations

¹ Johns Hopkins University, Department of Chemistry, Baltimore, MD 21218, United States of America.
² Colorado School of Mines, Department of Chemistry and Geochemistry, Golden, CO 80401, United States of America.
³ Carnegie Mellon University, Department of Civil and Environmental Engineering, Pittsburgh, PA 15213, United States of America.
⁴ United States Naval Academy, Department of Chemistry, Annapolis, MD 21402, United States of America.
⁵ Arizona State University, School of Sustainable Engineering and The Built Environment, Tempe, AZ 85287-3005, United States of America.
⁶ University of Pittsburgh, Department of Civil and Environmental Engineering, Pittsburgh, PA 15261, United States of America.
⁷ Oregon State University, The Sinnhuber Aquatic Research Laboratory, Corvallis, OR 97333, United States of America.
⁸ Arizona State University, The Polytechnic School, Ira. A Fulton Schools of Engineering, Mesa, AZ 85212, United States of America.
⁹ Johns Hopkins University, Department of Chemistry, Baltimore, MD 21218, United States of America. Electronic address: howardf@jhu.edu.

PMID: 30852200
DOI: 10.1016/j.scitotenv.2019.01.433

Abstract

Commercially available lumber, pressure-treated with micronized copper azole (MCA), has largely replaced other inorganic biocides for residential wood treatment in the USA, yet little is known about how different outdoor environmental conditions impact the release of ionic, nano-scale, or larger (micron-scale) copper from this product. Therefore, we weathered pressure treated lumber for 18 months in five different climates across the continental United States. Copper release was quantified every month and local weather conditions were recorded continuously to determine the extent to which local climate regulated the release of copper from this nano-enabled product during its use phase. Two distinct release trends were observed: In cooler, wetter climates release occurred primarily during the first few months of weathering, as the result of copper leaching from surface/near-surface areas. In warmer, drier climates, less copper was initially released due to limited precipitation. However, as the wood dried and cracked, the exposed copper-bearing surface area increased, leading to increased copper release later in the product lifetime. Single-particle-ICP-MS results from laboratory prepared MCA-wood leachate solutions indicated that a) the predominant form of released copper passed through a filter smaller than 0.45 micrometers and b) released particles were largely resistant to dissolution over the course of 6 wks. Toxicity Characteristic Leaching Procedure (TCLP) testing was conducted on nonweathered and weathered MCA-wood samples to simulate landfill conditions during their end-of-life (EoL) phase and revealed that MCA wood released <10% of initially embedded copper. Findings from this study provide data necessary to complete a more comprehensive evaluation of the environmental and human health impacts introduced through release of copper from pressure treated lumber utilizing life cycle assessment (LCA).

Keywords: Climate; Copper nanoparticles; Life cycle assessment; Micronized copper azole; Single-particle ICP-MS.