Assessing toxicity and mobilisation of impregnation salts at a contaminated site

Severe soil contamination is often encountered at wood-impregnation plants due to spills, dripping and deposition of sludge associated with dissolved salts of copper, chromium and arsenic (CCA). Soil samples from a CCA-plant in southern Norway were analysed via a factorial extraction design to investigate mobilisation of contaminated soils. Various concentrations of organic acids, sea-salts, and pH showed that contaminants were not stable, and could be mobilised to the aqueous phase. To further investigate mobilisation of impregnation salts, soil solution collectors were installed at various depths at the site. Concentrations varied considerably. Hydrological changes revealed elevated levels of dissolved salts, which agree with the factorial experiment. Soil chemical processes (not total solid-phase concentrations) dominated the mobilisation and subsequent leaching. Soil solutions were tested for changes in toxicity by chemical analysis and degree of inhibition of luminescence in Vibrio fisheri (Microtox). Changes in toxicity corresponded to changes in soil solution.