Assessing natural clays of a contaminated site to stabilize and reduce the ecotoxicity of a coal tar

Stabilization/solidification is widely used for the immobilization of pollutants in matrices. This work addresses the effect of illite amendment to a liquid coal tar on organic compounds (OCs) immobilization, especially PAHs and BTEX. For practical purpose, illite was selected as raw clay material available on the coal tar contaminated site. Contaminants availability and ecotoxicity of clay/tar matrices at various ratios and considering several treatments were assessed. Varying the tar mass fraction from 1 to 0.12, strongly viscous pastes, pellets and powders were obtained successively, with minimal contaminant mobility observed for tar fractions ranging from 0.28 to 0.80. Pellets obtained for the tar fraction of 0.33 were particularly studied for toxicity tests, because of their ease of handling. Using the land snail Cantareus aspersus as an ecotoxicity probe, mechanisms of PAHs bioavailability considering several treatments were studied. Considering either land snails for direct contact or exposed to vapors, or Lymnaea stagnalis for contact with leachates, toxicity of matrices decreased with ageing or even better with incineration.