Source Types for Benzene Concentration Without Similar Elevated TEX Concentrations

Ask the Expert Question:
At a remediation site we are working on, there is a monitoring well that had soil samples taken during the drilling process and analyzed for BTEX. All concentrations were below 1 part per million. However, the groundwater analysis is presenting an extremely elevated level of benzene with comparable levels of the TEX components. Other wells in the area are either non-detect or have low concentrations for benzene. The data has been verified and is accurate.

We do not understand the elevated Benzene constituent. What type of source would yield such a high Benzene concentration without similar elevated TEX concentrations?

Experts Response:
When benzene is present in environmental samples it is typically an indication of contamination by gasoline or some type of hydrocarbon based fuel. In those cases, however, other aromatics such as toluene, ethyl benzene, and xylenes are present along with numerous alkanes and alkenes. In this sample, the volatiles analysis did not indicate the presence of the other gasoline constituents that we would normally expect.

Benzene was used in various commercial products up until the late 1970’s. These included Liquid Wrench, model cement, paint strippers, rubber cements, and degreasers. It was available commercially in hardware stores for various applications, much like mineral spirits and turpentine are today. Given the presence of benzene in this sample and the absence of other gasoline related constituents, it seems likely that the contamination resulted from a relatively pure source of benzene used for one of these applications.

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