Sorbent Wicking Device for Sampling Hydrophobic Organic Compounds in Unsaturated Soil Pore Water. II: Chemical Capture, Recovery, and Analysis

Abstract

Experiments investigated the chemical capture and quantitative recovery of chlorinated hydrophobic organic compounds (HOCs) sampled from the pore-water of unsaturated soils with a new in situ sorbent wicking device. The sampling device is comprised of an annular porous stainless-steel interface encasing granular-activated carbon and a fiberglass wick. Laboratory column studies using Ottawa sand spiked with tri- and tetrachlorobenzenes evaluated the accuracy of the sampling device in assessing average pore-water concentrations. The findings from these experiments showed that the sorbent-wick sampler provided reliable and repeatable estimates of the pore-water concentrations of the chlorobenzenes in the unsaturated soil columns at pore-water concentrations as low as several parts per billion. Field trials were conducted in a land biotreatment unit containing industrial soil/sludge materials to assess the availability of trace levels of aqueous-phase polychlorinated biphenyls (PCBs). The land treatment unit had undergone 5 years of intrinsic remediation and the test results indicated that the samplers were able to replicate the aqueous-phase PCB homolog pattern measured in ex situ aqueous extraction tests. Orthosubstituted PCBs were dominant in sorbent-wick samples and aqueous extracts; these PCBs appear relatively recalcitrant in land biotreatment units. The sorbent-wicking device offers the ability to obtain time-averaged mass and volumetric flux rates of HOCs in land treatment units.