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4E - Food Safety (WEP/203) Risk assessment of cyanide contaminated gas work soil. Larsen, Morten1, Trapp, Stefan 1, 1 Technical University of Denmark, Kgs. Lyngby, DK, Denmark ABSTRACT- Risk assessment of old gas work sites has mainly been focusing on tars, PAHs and other organic contaminants, while cyanide has been considered secondary. However, cyanide need to be considered in plans for remediation and use of the sites. Volatilization of cyanide from polluted gas work soil was measured with two different methods. The first method uses passive samplers placed on site. In the second method was the soil placed in an desiccator under artificial light, and the volatilizing cyanide caught in a NaOH trap. The uptake of different cyanide species into consumable plants was measured. The plant species (potato (Solanum tuberosum), radish (Raphanus sativus), carrot (Daucus carota ssp. sativus) and strawberry (Fragaria x ananassa)) were grown in boxes and irrigated with water containing known concentrations of either free cyanide or thiocyanate. Plants were also grown in old gas work soil to measure the uptake of iron complexed cyanide. Results from the experiments will be presented. Phytotoxicity of cyanide to different plant species has also been measured. Sorghum (Sorghum bicolor) irrigated with 80 ml water containing 125 mg KCN L-1 showed no sign of toxicity after a period of 60 days. Analysis of the cyanide concentrations in soil, roots and stems showed increased concentrations in the compartments irrigated with cyanide, but only about 1% of the cyanide was recovered. Evaporation was found to account for 5-20 % of the cyanide loss, while the rest was taken up by the plants and metabolized or degraded by bacteria. Key words: cyanide , gas works, volatilization, plant uptake |
