Soil and groundwater contamination by nonaqueous phase liquids (NAPLs) has become a serious environmental issue. This study applied the thermo‐time domain reflectometry (TTDR) technique to determine the effects of NAPL contamination on the thermal and electromagnetic properties of unsaturated soils. Furthermore, the applicability of TTDR to determine the NAPL content was evaluated, and a new calibration equation was established to estimate the NAPL saturation level in unsaturated soils. Multiple unsaturated sand and silt loam samples at a constant water content were mixed with various amounts of motor and sunflower seed oils. The TTDR probes were then applied to simultaneously measure the dielectric constant, electrical conductivity, thermal conductivity, and heat capacity. An independent experiment was conducted to compare the NAPL content estimated using the new calibration equation and the known content. The results show that the NAPL content had no effect on the dielectric constant, and the soil dielectric constant maintained a steady value at the same water content, which ranged from 5 to 20 with increasing water content. At a constant water content, the soil electrical conductivity slightly decreased as the NAPL content increased. The soil thermal conductivity generally increased with the addition of NAPLs. There was a linear correlation between the total liquid content in the soil and the volumetric heat capacity. A new calibration equation was established to determine the NAPL saturation in soils from the relationship between the soil saturation, volumetric heat capacity, and water content as measured by time domain reflectometry. Independent validation indicated that the calibration equation was able to provide accurate NAPL saturation data in the laboratory, with a RMSE of 0.042.

中文翻译：

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热时域反射仪可评估被非水相液体污染的非饱和土壤

非水相液体（NAPL）对土壤和地下水的污染已成为严重的环境问题。这项研究应用热时域反射仪（TTDR）技术来确定NAPL污染对非饱和土壤的热和电磁特性的影响。此外，评估了TTDR确定NAPL含量的适用性，并建立了一个新的校准方程来估算非饱和土壤中NAPL的饱和度。将多个恒定水含量的不饱和沙和粉质壤土样品与各种量的汽车用和葵花籽油混合。然后将TTDR探针应用于同时测量介电常数，电导率，热导率和热容量。进行了独立的实验，以比较使用新校准方程估算的NAPL含量和已知含量。结果表明，NAPL含量对介电常数没有影响，在相同含水量下土壤介电常数保持稳定值，随着含水量的增加，介电常数在5〜20之间。在恒定的水含量下，土壤电导率随NAPL含量的增加而略有下降。随着NAPL的增加，土壤的热导率通常会增加。土壤中的总液体含量与​​体积热容之间存在线性关系。建立了一个新的校准方程，根据土壤饱和度，体积热容，以及通过时域反射法测量的水含量。独立验证表明，校准方程能够在实验室中提供准确的NAPL饱和数据，RMSE为0.042。