ORGANIC-CARBON DOMINATED TRICHLOROETHENE SORPTION IN A CLAY-RICH GLACIAL DEPOSIT

The relative contributions of organic carbon and mineral matter to tri chloroethene (TCE) sorption were determined for a natural, clay-rich t ill from Sarnia, Ont. using laboratory batch tests. Linear TCE sorptio n coefficients of the two till samples (approximataely 12 to 15 m dept h) were 64.2 l/kg and 151 l/kg and the organic carbon contents (f(oc)) were 0.68% and 1.95%, respectively. To ascertain the importance of so rption to mineral matter versus organic carbon, till samples were trea ted by baking. The f(oc) was reduced by 44 to 90% in treated samples c ompared to natural samples. TCE sorption coefficients were also reduce d to 0.48 to 4.64 l/kg in treated samples. Surface area measurements s uggested that treating the till samples appeared to have little effect on the mineral matter. The results indicated that TCE sorption is dom inated by the naturally occurring organic carbon. The organic carbon n ormalized sorption coefficients (K-oc) for the natural (untreated) sam ples were 16 to 500 times greater than those typically reported for se diment and soil samples, indicating the more lipophilic character of t he organic matter in the till. K-oc estimates which accounted for the oxidation state of the organic carbon in the till assuming the carbon is primarily from Devonian-age shale fragments resulted in values clos e to (within a factor of 2 to 5) these observed. Thus, both tbe nature and amount of organic carbon in the till play major roles in controll ing the magnitude of TCE sorption in this clay-rich deposit.