Sequestration Specificity of Single or Co-existing Benzene, 1,3,5-Trimethylbenzene, and Naphthalene in Soil

The sequestration (aging) of petroleum hydrocarbons in soil can have a significant effect on the remediation of contaminated sites, but organic chemicals and how they co-exist can result in different sequestration abilities. In this study, sorption, methanol extraction, and sequestration of single and co-existing benzene, 1,3,5-trimethylbenzene, and naphthalene in soil were investigated to evaluate their sequestration ability in soil and the influence of co-existing organic chemicals. A higher linear adsorption coefficient based on the linear sorption equation ( k e ) was observed for naphthalene (11.5–25.0) compared with benzene (3.8–3.9) and 1,3,5-trimethylbenzene (2.8–5.6), followed by a lower linear methanol extraction coefficient based on the methanol extraction equation ( k m = 0.3) and a higher linear sequestration coefficient based on the linear sequestration equation ( k s = 0.7). The co-existence of benzene, 1,3,5-trimethylbenzene, and naphthalene increased the sorption ability of 1,3,5-trimethylbenzene ( k e increased from 2.8 in the single system to 5.6 in the mixed system) and naphthalene ( k e increased from 11.5 in the single system to 25.0 in the mixed system) due to their larger molecular size and higher molecular polarity; however, this was not observed for benzene ( k e ranged from 3.8 to 3.9 in the single and mixed systems). In summary, the co-existence of benzene, 1,3,5-trimethylbenzene, and naphthalene does not affect methanol extraction and sequestration ability.