Transport and biodegradation of creosote compounds in clayey till, a fieldexperiment

The transport and biodegradation of 12 organic compounds (toluene, phenol, o-cresol, 2,6-, 3,5-dimethylphenol, naphthalene, l-methylnaphthalene, benzo thiophene, dibenzofuran, indole, acridine, and quinoline) were studied at a field site located on the: island of Funen, Denmark, where a clayey till 1 0-15 m deep overlies a sandy aquifer. The upper 4.8 m of till is highly fra ctured and the upper 2.5 m contains numerous root and worm holes,:A 1.5-2 m thick sand lens is encountered within the till at a depth of 4.8 m. Sampli ng points were installed at depths of 2.5 m, 4 m, and in the sand lens (5.5 m) to monitor the downward migration of a chloride tracer and the organic compounds. Water containing organic compounds and chloride was infiltrated into a 3 m x 4.8 m basin at a rate of 8.8 m(3) day(-1) for 7 days. The mass of naphthalene relative to chloride was 0.39-0.98 for the sampling points located at a depth of 2.5 m, 0.11-0.61 for the sampling points located at a depth of 4 m, and 0-0.02 for the sampling points located in the sand lens. A similar pattern was observed for eight organic compounds for which relia ble results were obtained (toluene, phenol, o-cresol, 2,6-, 3,5-dimethylphe nol, 1-methylnaphthalene, benzothiophene, and quinoline). This shows that t he organic compounds were attenuated during the downward migration through the till despite the high infiltration rate. The attenuation process may be attributed to biodegradation. (C) 2000 Elsevier Science B.V. All rights re served.