IMPACTS ON SORPTION FROM ORGANIC CARBON CONSTITUENTS IN SEDIMENTARY AQUIFERS

Sorption of hydrophobic organic compound plumes in soils and sediments is predominantly controlled by the organic matter (OM). Past research has shown that even a minor fraction of highly-sorbing OM can govern the sorption of these plumes within an aquifer. Samples that contain nonlinearly sorbing OM types such as kerogen and char indicate that there are multiple sorption regimes influencing the overall sorption behavior. This highly sorbing OM can be found in sedimentary lithic fragments in low organic carbon sandy aquifers, a geological setting common to much of the glaciated North Central United States.

Sorption and fraction organic carbon (foc) values were evaluated and compared for lithic fragments representative of two sedimentary aquifers: Borden, Ontario (Canada) and Binghamton, New York (USA). These marine-derived sedimentarylithic fragments exhibit similar sorption capacities and the same foc (0.07%). However, the Borden samples equilibrate more rapidly than the New York samples, indicating a difference in organic matter type.

Source rock material typical of the lithocomponents found in the aquifer settings will be analyzed to identify carbonaceous matter (CM) proportions. A parallel series separation method to isolate specific organic carbon constituents was developed using methods previously established by the scientific community. A combination of chemical treatments (HCl, TFA, and NaOH) and density separation are used to isolate kerogen, char, humic acid and fulvic acid. The isolated fractions are analyzed for total organic content and sorption. Comparison between results from bulk sample analysis and the individual CM constituents evaluate CM-specific trends. These results will provide insight to CM constituents within a sedimentary aquifer and their impacts on sorption behavior.