Diffusion of heterocyclic compounds from a complex mixture of coal-tar compounds in natural clayey till

The diffusion of coal-tar compounds in natural clayey till was studied expe rimentally. Cores were exposed to a solution with near constant concentrati on of coal-tar compounds in a multi-component mixture for 5 months, the cor es were subsequently sub-sampled and analyzed, Diffusion profile data stron gly indicates highly non-linear sorption isotherms. For dibenzofuran, diben zothiophene, 2-methylquinoline, carbazole, phenanthrene, and fluorene, the profiles indicated significantly stronger sorption at high solute concentra tions than at low solute concentrations, and than expected based on linear sorption isotherms. This corresponds with observed dramatic increase in sor ption of these compounds at high surface density. For benzofuran, benzothio phene, quinoline, phenols, naphthalenes, and BTEXs the profiles indicated s ignificantly weaker sorption at high solute concentrations than at low solu te concentrations and than expected based on linear or Freundlich isotherms . The observed diffusion profiles have important implications with respect to transport of dissolved coal-tar compounds in multi-component mixtures of high concentrations as expected near immiscible phase coal-tar sources. Br eakthrough times and concentration levels are affected significantly. (C) 1 999 Elsevier Science B.V. All rights reserved.