Column leaching and sorption experiments to assess the mobility of potentially toxic elements in industrially contaminated land

Made-up ground collected from layers of a trial pit excavated on a former i ndustrial site was treated with artificial rainwater in a series of column leaching and sorption experiments. Metal mobility and the ability of variou s layers of material obtained from the pit to act as sources or sinks of po tentially toxic elements were assessed. Samples from different layers varie d in their abilities to raise the pH of rainwater applied at pH 3.5 and 4.3 , and this was reflected in the amounts of metals mobilised by the rainwate r as it percolated through the soil column. Material from the top two layer s of the pit released cadmium, copper, manganese, lead, nickel and zinc to the aqueous phase, but the lower layers, with higher buffering capacity, we re able to resist acidification even when the equivalent of 12 months' rain fall (western UK) was applied. Column sorption experiments confirmed the ab ility of material from layer 4 (48-50 cm) to take up copper, manganese and zinc. Metals were determined in the leachates by flame and electrothermal a tomic absorption spectrometry and principle anions by ion chromatography.