Increasing attention has been paid to persulfate activation for the degradation of organic contaminants due to its high efficiency and low cost. However, most previous studies have overlooked the detection of generated reactive oxygen species (ROS), which plays an important role in the transformation of contaminants. In this study, the activation of persulfate by ultrasonic field (UF) for the degradation of 1,1,1-trichloroethane (TCA) and solvent stabilizer 1,4-dioxane (1,4-D), and the possible reaction mechanism were investigated. The results showed that the contaminants can be efficiently degraded under the optimal conditions of pH(0) = 7.0, Temp. 15 +/- 2 degrees C, persulfate 1.50 mmol/L, ultrasonic frequency 400 kHz, power 100 W and ultrasonic density 2.67 W/cm(2) with initial TCA similar to 20 mg/L and 1,4-D similar to 1.0 mg/L. Coexisting 10 mmol/L inorganic anions slowed down the contaminant degradation to different degrees, and the inhibiting effect followed the order of CO32- > HCO3- > Cl- > SO42- > NO3-. The electron paramagnetic resonance (EPR) technique was used to detect and identify the ROS. Results show that the applied UF could effectively activate persulfate and produce more hydroxyl radicals ((OH)-O-center dot) and sulfate radicals (SO), accordingly resulting in the enhanced degradation of the contaminants. Twenty-three and eight degradation intermediates were detected and identified for TCA and 1,4-D, respectively. Results indicate that the sono-activated persulfate process is a promising technique to simultaneously eliminate of TCA and 1,4-D from water or groundwater. (C) 2015 Elsevier B.V. All rights reserved.