The mixed soil contamination of salts and petroleum hydrocarbons has become a worldwide concern since these pollutants can cause serious environmental and human health problems. An advanced remediation method -- ultrasonic enhanced soil washing was evaluated for its ability of remediating such contamination. The impacts of five factors including initial total petroleum hydrocarbon (TPH) concentration, salinity, soil type, ultrasonic treatment time and soil washing flow rate were investigated through experimental design using orthogonal arrays, and the results indicated that all these factors could significantly affect the treatment performance. Two mechanisms of ultrasonic soil remediation of TPH were proved to be desorption and degradation. The combination of ultrasound and soil washing successfully enhanced the TPH removal and the best treatment efficiency at optimized conditions was 96.17 ± 3.56%. The application of soil washing in ultrasonic treatment greatly reduced the negative effect of salt. --P. ii.
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