Toxicity Assessment of Aircraft De-Icier

Toxicity Assessment of Aircraft De-Icier In order to guarantee safety and regularity of air traffic at airports located in cold climates, large amounts of de-icer and anti-icing fluids (ADAF) are used on runways and aircrafts prior to take-off in order to remove ice from the ground and airplanes? surfaces. Aircraft ADAF are aqueous solutions of a glycol or mixture of glycols, with some proprietary additives. Depending on the formulation required, the additives might include a surfactant, polymer thickening agent, pH buffer, corrosion inhibitor, flame retardant, or a dye. Most airports operate ADAF collection systems and treat or recycle the spent fluids. But a portion of the ADAF escapes through storm sewer systems to receiving surface waters, groundwater systems, or are stored into snowbanks. The most known environmental effects of the discharge of ADAFs in the environment are those associated with glycols, thus causing a potential reduction of the dissolved oxygen in receiving waters (because of an increased biochemical oxygen demand) and the potential toxicity of ADAF additives. Still, the environmental route and impact of many of the additives in the de-icing agents is poorly understood. Recently, American scientists have taken samples from snowbanks and snowbank runoff at a medium-size airport over a 4-year period in order to characterise ADAF components and assessed their toxicity. They used biosensor-based measurement systems for predicting the potential toxicity effects. The results suggest that the environmental risk of various Aircraft ADAF components may be more difficult to assess than previously estimated. The authors found that the toxicity associated with ADAF remained after glycol had been removed during periods of warm weather when the snowbanks had started to melt. This suggests that only part of the toxicity of ADAF can be explained by these compounds, and therefore additional toxic additives exist and need to be studied. In the snowbank samples the authors identified alkylphenol ethoxylates, nonionic surfactants that can be toxic to aquatic organisms and degrade into the known endocrine disrupters nonylphenol and octylphenol. A second group of additives was the toxic corrosion inhibitors benzotriazoles and tolyltriazoles. These compounds have been detected in receiving waters near investigated airports. Some forms of benzotriazole are not readily biodegradable and are not adequately removed in wastewater treatment plants. Overall, the results of the current study indicate that airports cannot simply monitor glycol levels as an indicator for the fate of all the de-icer components, because glycols do not provide a complete picture of the fate and transport of ADAF additives. Further investigations have to be made regarding this issue in order to minimise the potential impacts on the local environment (around the airports). Source: Corsi, S. R. et al (2006) Ť Characterization of Aircraft Deicer and Anti-Icer Components and Toxicity in Airport Snowbanks and Snowmelt Runoff ť, Environ. Sci. Technol.; doi: 10.1021/es052028m.Contact: srcorsi@usgs.gov

ZDROJ: Science for Environment Policy