NONLINEAR TCE SORPTION IN SEDIMENTARY ROCKS FROM THE NEWARK BASIN

TCE sorption isotherms were created for four different lithologic units from a fractured sedimentary rock aquifer near West Trenton, NJ to determine the dominant mechanism of sorption. Samples were sourced from the contaminated site at the former Naval Air Warfare Center (NAWC). There are four major lithologies present at the NAWC site: carbon rich laminated mudstone, dark-gray laminated mudstone, light-gray massive mudstone, and red massive mudstone. The lithologic units exhibit more than an order of magnitude range in fraction organic carbon (f_oc) and represent a range of depositional environment and age.

Sorption measurements were conducted with pulverized samples in well mixed batch systems to determine the extent that TCE sorbs to each native rock. The initial TCE concentration and carbon content in the native rocks were treated as variables and were used to compare resultant isotherms. Concentrations were measured by an HP 5890 gas chromatograph (GC) and an electron capture detector (ECD). Mass balances were conducted to ensure that the mass losses were not significant. The resulting isotherm shape is used to infer the sorption mechanism; a linear result suggests a partitioning mechanism, while a curved isotherm suggests a pore-filling mechanism.

The sorbed mass in the rock matrix plays a significant role in the targeted remediation of a contaminated rock environment. The matrix can act as long term storage for TCE and after aqueous concentrations are reduced TCE can be desorbed, affecting a plume’s longevity. Once translated to other fractured rock sites, understanding the mass sorbed as a function of aqueous concentration in the system can play a vital role in maximizing remediation efforts.