The objective was to determine the significance of site and wood species on preservative depletion for a copper chrome arsenate preservative (CCA) from 20 x 20 x 500 mm field test stakes after 5.5 and 4.5 years for pine and beech respectively. At least 5 sacrificial stakes were used to produce site means. Site and wood species had a major effect on copper, chromium and arsenic loss from CCA treated pine and beech. At the most severe site above and below ground percentage losses for pine were, 36 and 73 for copper, 22 and 22 for chromium and 31 and 49 for arsenic. At the least severe site losses were close to zero for both above and below ground. Based on mean loss across all sites, the above ground portion of CCA treated pine lost less than 1% copper compared to 8% for chromium and 15% for arsenic. Increased copper (30%) loss for the below ground portion compared to the above ground portion (<1%), was much greater than for chromium (8 versus 9%) and arsenic (15 versus 22%). Whereas copper loss was most affected by below ground exposure for pine, for beech arsenic was most affected. All three elements were more susceptible to loss from beech than pine for both above and below ground exposure, except below ground copper (30% loss for pine and 28% for beech). Arsenic in particular was more susceptible to loss from beech for both above ground (32% for beech versus 15% for pine) and below ground (53% for beech versus 22% for pine). The finding that waterlogged sites, and/or sites with low pH caused greatest loss to all treatments irrespective of wood species, in the light of low loss at horticultural sites suggested that the influence of extremes of water availability and of low pH was more important than other mechanisms such as cationic exchange reactions with soil. Particularly high loss occurred at sites where soil was likely to have contained a high organic acid concentration.

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