Effect of alcohol addition on the movement of petroleum hydrocarbon fuels in soil

Abstract

Groundwater contamination by fuel spills from aboveground and underground storage tanks has been of growing concern in recent years. This problem has been magnified by the addition of oxygenates, such as ethanol and methyl-tertiary-butyl ether (MTBE) to fuels to reduce vehicular emissions to the atmosphere. These additives, although beneficial in reducing atmospheric pollution, may, however, increase groundwater contamination due to the co-solvency of petroleum hydrocarbons and by the provision of a preferential substrate for microbial utilisation. With the introduction of ethanol to diesel fuel imminent and the move away from MTBE use in many states of the USA, the environmental implications associated with ethanol additive fuels must be thoroughly investigated. Diesel fuel movement was followed in a 1-m soil column and the effect of ethanol addition to diesel fuel on this movement determined. The addition of 5% ethanol to diesel fuel was found to enhance the downward migration of the diesel fuel components, thus increasing the risk of groundwater contamination. A novel method using soil packed HPLC columns allowed the influence of ethanol on individual aromatic hydrocarbon movement to be studied. The levels of ethanol addition investigated were at the current additive level (approx. 25%) for ethanol additive fuels in Brazil and values above (50%) and below (10%) this level. An aqueous ethanol concentration above 10% was required for any movement to occur. At 25% aqueous ethanol, the majority of hydrocarbons were mobilised and the retention behaviour of the soil column lessened. At 50% aqueous ethanol, all the hydrocarbons were found to move unimpeded through the columns. The retention behaviour of the soil was found to change significantly when both organic matter content and silt clay content was reduced. Unexpectedly, sandy soil with low organic matter and low silt clay was found to have a retentive behaviour similar to sandy subsoil with moderate silt clay, but little organic matter. It was concluded that sand grains might have a more important role in the adsorption of petroleum hydrocarbons than first realised. This method has shown that soil packed HPLC columns can be used to provide a quick estimate of petroleum hydrocarbon, and possibly other organic contaminant, movement in a variety of different soil types.

Evaluation of bioventing on a gasoline?ethanol contaminated undisturbed residual soil

“…When spills occur, ethanol reaches subsurface waters much more rapidly than gasoline components [10]. In gasoline-ethanol contaminated aquifers, ethanol is preferentially utilised, and therefore degraded, over other persistent gasoline compounds, mainly benzene, toluene, ethyl-benzene, and xylenes (BTEX).…”

Vapour phase transport of ethanol- and butanol-blended gasoline compounds in the vadose zone: a lysimeter experiment

“…Generally, the transport behaviour of B20-pentane was midway between E20-pentane and UG-pentane. Theoretically, E20 and B20 should partitioned more into the soil water than UG due to the cosolvent effect of alcohol [1][2][3]20], and UG should be adsorbed more on the soil solids than B20 and E20 due to its higher hydrophobicity [25]. Therefore, the observed lower vapour phase concentration and transport for UGpentane suggests that more adsorption on the soil solids than partitioning to the soil water of pentane occurred in this study.…”

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“…Metals taken up via roots and passes easily to edible leaves of fruits and seeds. It will also accumulate in animal milk and fatty tissues 11,12 .…”