Effects of deck washes and brighteners on the leaching of CCA components

There has been concern that bleaching and-other agents in commercial deck w ashes and brighteners could aggressively leach chromated copper arsenate (C CA) components from treated wood. Natural rain water drippage was collected over several rain events from small-scale CCA type C treated southern pine decks and from an approximately 12-year-old CCA-C treated spruce/pine/fir deck installed in New Brunswick, Canada. The decks were then treated with a number of commercial deck washes/brighteners, and the CCA components in th e wash solution were compared to those from water wash only and from the na tural rain events. Treatments containing phosphoric acid, citric acid, and oxalic acid resulted in relatively high copper losses during the washing tr eatment and slightly increased losses of the other components. Strong oxidi zing agents such as sodium hypochlorite and sodium percarbonate resulted in oxidation of chromium to the hexavalent state and subsequent loss of solub le hexavalent chromium. Alkaline sodium hydroxide and sodium berate treatme nts also mobilized some hexavalent chromium. Losses were much higher from n ew decking than from a deck that had been in service for approximately 12 y ears.