Long-term degradation of toluene and phenol in soil: Identification of transformation products and pathways via HRMS-based suspect and non-target screening

Abstract

In this study, the long-term fate of toluene and phenol in the soil was investigated, and the transformation products (TPs) and pathways of these compounds were studied by a high resolution mass spectrometry (HRMS)-based suspect and non-target screening approach for the first time, and 9 and 12 transformation products were identified for toluene and phenol, respectively in the lab-exposed soil samples. Salicylaldehyde, 4-hydroxybenzaldehyde, and benzaldehyde were identified in toluene-contaminated field soil samples for the first time, and the main mechanisms involved in the biodegradation and detoxification of toluene and phenol in soil were oxidation, carboxylation, dehydroxylation, and ring fission amongst others. 2-oxoglutarate, TP165-A, TP165-B, TP172, and TP195 were identified as novel phenol transformation products, while salicylaldehyde, 2-oxoglutarate, TP165-A, and TP165-B were identified as novel toluene transformation products, providing new possible evidence for additional degradation pathways, which could give new insights into the fate of toluene and phenol during the natural attenuation process in the environment. Finally, salicylaldehyde, 4-OH-benzaldehyde, and 4-OH-benzoic acid which were detected at Level 1 identification confidence were suggested as indicator chemicals of toluene and phenol exposure in the contaminated field.