Phytoremediation of Aircraft De-icer and Antifreeze Formula- Tions

Key words: aircraft de-icing fluid (ADF), phytoremediation, tolyltriazole, propylene glycol, ethylene glycol Aircraft de-icer fluids (ADFs) and antifreeze solutions are mainly formulations of either propylene or ethylene glycol and additives such as benzotriazole methyl substitution isomers (tolyltriazoles), and surfac-tants. Although the formulations are proprietary, in general the glycols are present in concentrations that vary from 20 to 95 % and the triazoles at levels up to 1 g/L. The ADFs are used and discharged to the environment in large quantities, constituting a terrestrial and aquatic environmental risk. Although the in situ biodegrada-tion of glycols has been achieved under controlled conditions, the (bio)degradation potential and mode of toxicity of the triazoles remain uncertain. Triazoles are identified as possible carcinogens and inducers of toxic responses in aquatic flora and fauna. Lignin peroxidase, which is the catalyst in the lignification process in higher plants, is an enzyme that is able to degrade triazole. We found a threshold for toxicity of triazoles to common grass and to sunflowers, of about 0.1 g/L. It was not possible to extract triazoles from the treated plants. The presence of glycols and surfactants in the ADF mixture impacts plant growth and health. These compounds can reduce the ability for the plant to immobilize the triazoles.