Development and testing of a field screening method based on bubbling extraction and photoionization detection for measurement of benzene and total VOCs

Published in:
Groundwater Monitoring & Remediation, September 2014

Peter Bennett and Murray Einarson, Haley & Aldrich; Catalina Espino Devine, Karen Synowiec, Sheldon Nelson, and Rachel Mohler from Chevron Energy Technology Company

A field screening method was developed for rapid measurement of benzene and gasoline range total petroleum hydrocarbons (TPHg) concentrations in groundwater. The method is based on collecting photoionization detector (PID) measurements from vapor samples. The vapor samples are collected by bubbling air through groundwater samples (air sparging) with a constant volume, temperature and sparging rate. The level of accuracy, sensitivity, precision, and statistical significance of the estimated concentrations, derived from the screening method, are comparable to conventional laboratory analytical results at concentrations equal to or greater than 150 μg/L for benzene and greater than 50 μg/L for TPHg. The method’s concentration estimations can assist in making real-time decisions regarding location of dissolved plumes and light nonaqueous phase liquid (LNAPL) source zones at many fuel release sites. The screening method was tested in the laboratory and in the field with 208 and 107 samples, respectively. The study concludes that the screening method can be used as a tool to aid in completing a site conceptual model as well as analyzing groundwater from monitoring wells.

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