Analytical Sciences

Assessment for Less than 20-ppm Oil Leakage in Soil Using Terahertz Wave

Ru CHEN,* Yan ZHANG,* Zhaohui MENG,* Honglei ZHAN,** Kun ZHAO,** Xiaodong WU,*** Wenzheng YUE,* and Encheng SUN***

*State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
**Beijing Key Laboratory of Optical Detection Technology for Oil and Gas, China University of Petroleum, Beijing 102249, China
***Technology Inspection Center, Shengli Oil Field, Sinopec, Shandong 257000, China

Although an accurate detection of trace oil leaks is of the utmost important for soil protection, the typically used techniques fail to provide rapid assessment of less than 20 parts per million (ppm) of oil in soil. Terahertz (THz) time-domain spectroscopy, an optical method with high sensitivity to polar organics, was used to characterize the content of crude oil in soils. A linear model was built between the concentration of crude oil and the THz attenuation coefficient, which predicted the limit of detection ranging from 4.11 to 16.2 ppm. Some organics, such as aromatic and aliphatic compounds, contribute to larger absorption in the THz range than minerals. Effective-medium theory was optimized to elucidate the crude oil content dependence of THz dielectric constants. Consequently, THz technology could be an effective method for detecting trace oil leakage in soil.

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