Arsenic availability from chromated copper arsenate (CCA)-treated wood

Area of Science:

• Environmental Science
• Soil Science
• Agricultural Science

Background:

• Lumber for raised garden beds often uses chromated copper arsenate (CCA) for preservation.
• CCA contains arsenic (As), copper (Cu), and chromium (Cr), raising concerns about soil and crop contamination.

Purpose of the Study:

• To quantify the diffusion of As, Cu, and Cr from CCA-treated wood into adjacent soil.
• To assess the uptake of these elements by common garden crops.
• To investigate the impact of CCA on soil bacterial resistance.

Main Methods:

• Soil samples were collected from near CCA-treated wood and control sites.
• Carrot, spinach, bush bean, and buckwheat were grown in these soils under greenhouse conditions.
• Plant tissues were analyzed for As using inductively coupled plasma-hydride generation (ICP-HG).
• Bacterial resistance to CCA solutions was tested using dilution plates.

Main Results:

• Arsenic, copper, and chromium were found to diffuse from CCA-treated wood into the surrounding soil.
• Crops grown in contaminated soil showed higher As concentrations than those in control soil.
• As levels in all tested crops remained below the US Public Health Service recommended limit.
• Soil bacteria from areas near CCA-treated wood exhibited greater resistance to CCA solutions.

Conclusions:

• CCA-treated wood contributes to soil contamination with As, Cu, and Cr.
• While crops absorb these elements, levels remain within safe limits.
• Soil microbial communities adapt to CCA contamination, developing increased resistance.