Study of the remediation of a site contaminated with arsenic

Soil and rock-like material was collected from a former industrial site (arsenic factory) in order to study the degree to which the site is contaminated. Characterisation of the soil and rock-like samples indicated that the site is highly contaminated with arsenic: the soil material contains 2.5–3.5% (dry wt.%) of arsenic, the rock-like material up to 20%. According to Flemish norms (VLAREBO, 1996) concerning the contamination of soils for industrial sites, remediation of the soil is required on a short-term basis when a value of 300 mg As/kg of dry solid is exceeded. In this paper, solidification/stabilisation with cement and/or lime for remediation of the site was studied. If later the solidified site material is landfilled, one of the criteria is that the arsenic concentration in the leachate, determined according to the DIN 38 414 S4 extraction test (Deutsches Institut für Normung, 1984), must be lower than 1 mg/l (VLAREM II, 1995). Solidification proved to be an efficient method to lower the amount of arsenic leached from the material to below the norm of 1 mg/l. The results of a semi-dynamic leach test indicated that arsenic was released very slowly from the solidified material: over the period of the leach test only 0.10% of the arsenic initially present was leached.