Petroleum spills cleaned up by plants

The Environmental Protection Agency and industry researchers are using plants to clean up at petroleum spills at sites across the US. The techniques, developed by research team at Purdue University, Indiana are proving efficient and cost effective in breaking down soil pollutants.

Phytoremediation is the direct use of living green plants in situ, to reduce risks from contaminated soil, sludges, sediments, and ground water, through contaminant removal, degradation, or containment.

Soil microbes actually break down the petroleum contaminants but plants accelerate the microbes’ action in the soil. They stimulate microbes to degrade contaminants by getting more oxygen into the soil and by supplying nutrients through their roots. Other biological clean-up methods can do the job faster, but phytoremediation costs much less and leaves the soil structure intact.

Katharine Banks, professor of civil engineering and agronomy professor Paul Schwab are working with the EPA and Indiana Gas Co to compare the efficiency of several bioremediation methods at the contaminated site of a coal-to-natural gas refinery. The team have used plants to help clean up a Texas oil pipeline spill, contamination at an Indiana manufactured-gas plant, an industrial sludge site in California and diesel spills at naval bases in Virginia and California.

Petroleum is one of the major soil contaminants around the world. It is not very mobile, adhering tightly to components of the soil and staying in the top six feet of the soil. Phytoremediation can be very effective as the contaminants are in direct contact with plant roots. Standard methods entail digging the soil out and incinerating, composting or landfilling the contaminated material.

For phytoremediation to be effective, the right plant must be chosen. The species must be appropriate for the climate, and the plant must be able to survive in contaminated areas and encourage microbial growth. Fescue, Bermuda grass, clovers and alfalfa all look promising in certain situations.

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