An ultrasound-enhanced elution system employing water at a temperature of 70 degrees C was used to remedy weathered soils contaminated with severely biodegraded heavy oil (SBHO). The effect of varying the ultrasonic irradiation time from 0 to 1800s on the elution of SBHO and three characteristic biomarkers (C26-34 17 alpha 25-nothopanes, C26-28 TAS, and C27-29 MTAS) was analyzed using GC/MS, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Elution of the three biomarkers was closely related to the carbon number of the marker. C26-34 17 alpha 25-norhopanes and C26-28 TAS species with higher carbon numbers and C27-29 MTAS species with lower carbon numbers were more readily eluted using sonication times of 1080-1800s, while smaller TAS homologs were more readily eluted after sonication times of 0-360s. SEM images of samples treated for longer periods revealed larger "bare patches" on the soil surface. The results of XRD and energy spectroscopy experiments indicated that ultrasound irradiation for 1080s negatively affected the deposition of CaCO3, but overall improved the mineral and chemical compositions of treated soils and removal of SBHO. (c) 2010 Elsevier B.V. All rights reserved.