Abstract

Batch microcosm experiments were conducted to examine the impact of soil organic matter (SOM) on the sorption and phase distribution of 20% butanol-blended gasoline (B20) compounds in the vadose zone. SOM was found to promote the sorption of B20 gasoline compounds in the vadose zone. It also affected the phase distribution of B20 gasoline compounds in the vadose zone by increasing adsorption on the soil solid and reducing concentrations in the soil air and soil water. These impacts increased with decreasing hydrophobicity of gasoline compounds. However, when compared with unblended gasoline, the SOM-induced increase in sorption coefficient for B20 gasoline compounds was reduced by a maximum of 66% for the cycloalkanes, 60% for the aromatics and 37% for the alkanes, implying a general reduction in the sorptive capability of SOM. Therefore, the use of high butanol volume such as 20% in gasoline to combat climate change is likely to reduce the retentive capability of SOM in the vadose zone and thus may increase groundwater contamination with gasoline compounds.

Key words: Butanol-blended gasoline, sorption, phase distribution, vadose zone, soil organic matter.