Copper migration from preservative-treated Douglas-fir decking: models vs laboratory leaching data

The ability of a model to predict copper migration from Douglas-fir treated with organic metallic substances into a freshwater slough was evaluated against data generated through simulated overhead leaching. The model predicted very high loadings of ammoniacal copper zinc arsenate, alkaline copper quaternary or copper azole that had the potential to impact water quality while data from the experimental overhead leaching apparatus were often 10-fold lower. The data support the premise that the model is inherently conservative, but the dramatic differences suggest the need for further studies to better understand that nature of the variations.