Mobility of the constituents of chromated copper arsenate in a shallow sandy soil

Small volumes of a commercial timber preservative containing approximately 60% w/w chromated copper arsenic (CCA) were applied to 15-cm-deep, undisturbed soil monolith lysimeters containing the surface horizon of a mildly acidic, sandy loam soil extracted from within the forestry plantation region of south-west Victoria. The collected leachate and samples of the core profiles were analysed by inductively coupled plasma emission spectroscopy (ICP-ES) for a total of 28 elements, including the active ingredients of the preservative, copper, chromium, and arsenic. After application of CCA, of the metals studied, only the concentrations of arsenic, calcium, chromium, sodium, and potassium in the leachate differed from background concentrations during the irrigation of the cores. Copper concentrations in all leachate remained at background levels throughout the experiment. Up to 36% of the applied dose of chromium was detected in the leachate, with breakthrough at 15 cm soil depth occurring within 20 days of preservative application. Up to 13% of the applied dose of arsenic was detected in the leachate collected at 15 cm depth, although in this case breakthrough was not observed until 25 days after preservative application. The applied copper was immobilised in the top 4 cm of the soil. Elevated concentrations of arsenic and chromium were found in the top 6 cm of the soil profile.