Depletion of CCA-C from Ground-Contact Wood: Results from Two Field Sites with Significantly Different Soils

Summary

Two field test sites with different soil types were selected. Analysis showed that the two soils had considerable between-site variation in texture, base saturation, acidity, levels of metals, and cation exchange capacity. The sites also had moderate differences in average seasonal temperatures and rainfall. Stakes, made from defect-free southern yellow pine (SYP) sapwood and measuring 19×19×559mm, were treated to about 0.40 pcf (6.4 kg/m³) with chromated copper arsenate (CCA-type C). The stakes were installed at the two sites and sets of ten or more samples pulled after 55 and 66 months of exposure. The depletion of the individual components (chromium, copper and arsenic, oxide basis) from below-ground sections of each stake was then determined. No significant site effect on depletion was observed despite the large contrasts in chemical and physical properties between the two soils. Of the individual components, copper generally had the least depletion on a pcf weight loss basis while the greatest loss was observed with arsenic in three of the four time/site sets. The exposure times examined had no influence on depletion.