Preservative leaching from weathered CCA-treated wood

Area of Science:

• Environmental Science
• Waste Management
• Materials Science

Background:

• Chromated copper arsenate (CCA)-treated wood disposal in landfills poses risks due to preservative leaching.
• Unweathered CCA wood often exceeds the toxicity characteristic (TC) limit for arsenic (5 mg/L) when leached.
• Weathering during use may alter the leaching characteristics of CCA-treated wood.

Purpose of the Study:

• To evaluate the leaching of arsenic, copper, and chromium from weathered CCA-treated wood.
• To compare leaching results using the Toxicity Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP), and Waste Extraction Test (WET).
• To determine if weathered CCA-treated wood meets TC hazardous waste criteria.

Main Methods:

• Collected CCA-treated wood from various sources with different weathering histories.
• Leached wood samples using TCLP, SPLP, and WET.
• Analyzed leachate for arsenic, copper, and chromium concentrations.

Main Results:

• Average TCLP arsenic concentrations ranged from 3.2 to 13 mg/L across 14 sources.
• 60% of 100 tested wood samples exceeded the 5 mg/L TC limit for arsenic via TCLP.
• WET leachate concentrations were approximately 10 times higher than TCLP concentrations.

Conclusions:

• CCA-treated wood, even after years of weathering, frequently exceeds the TC arsenic limit.
• Leaching behavior differs among TCLP, SPLP, and WET, with WET showing higher concentrations.
• CCA-treated wood may require management as hazardous waste if not for current regulatory exemptions.