Quantitative determination of toluene, ethylbenzene, and xylene degradation products in contaminated groundwater by solid-phase extraction and in-vial derivatization

Abstract

Benzylsuccinic acid (BSA) and methylbenzylsuccinic acids (mBSAs) are unambiguous indicators of anaerobic toluene and ethylbenzene/xylene degradation, and so the determination of these compounds in landfill leachates and contaminated groundwater is highly relevant. Samples were diluted to <0.8 mS cm⁻¹ in order to reduce their ionic strength, and subsequently extracted through strong anion exchange disks, followed by simultaneous in-vial elution and methylation. A detection limit of 0.1 µg L⁻¹ was obtained for 100 mL samples. Using this method, 19.3 µg L⁻¹ of BSA was measured in a landfill leachate, and low µg L⁻¹ levels of all of the mBSAs were measured in gasoline-contaminated groundwater. The results were compared with the findings of BSAs at 16 other contaminated sites, and BSAs as indicators of biodegradation were evaluated. The estimation of biodegradation rates based on parent hydrocarbons and BSA concentrations or ratios is questionable. However, the degradation products serve as good qualitative in situ indicators for anaerobic biodegradation in contaminated groundwater.

Keywords:

• Benzylsuccinic acid
• Solid-phase extraction
• GC/MS
• Landfill leachate
• Groundwater
• Biodegradation

Acknowledgements

Assistance provided in the laboratory from Ms Anja Foverskov and Mrs. Lena Troelsen is gratefully acknowledged. The authors would also like to express their gratitude to Dr Jennifer Field and Dr Torben Nilsson for their valuable comments on the experimental procedure. Funding for this study was provided by the Groundwater Research Center/Environment & Resources DTU and the Technical University of Denmark. The Danish Petroleum Industry's Association for Remediation of Retail Sites (OM) and the County of Storstroem kindly provided access to the Radsted field site.