News Release

Humus/Mineral interaction

Peer-Reviewed Publication

Penn State

University Park, Pa. --- A group of Penn State-led researchers has shown that, for some fossil fuel-based pollutants, increasing the humus content of the soil increases, rather than decreases, the likelihood that the contaminant will move to ground water.

Dr. Jon Chorover, assistant professor of environmental soil chemistry, says, "The general belief is that, as you increase the organic matter in soil, you increase the retention of contaminants. We found that that is not always the case. It depends on the nature of the compound."

Chorover and his colleagues at Penn State's Environmental Resources Research Institute and Ohio State University looked at quinoline, a nitrogen heterocyclic compound (NHC), that has been little studied to date. Quinoline belongs to the broad group of environmental contaminants, termed ionizable PACs (polycyclic aromatic compounds), often found in sites polluted by fossil fuels, solvents, greases, creosote and coal tar.

They found that if a soil is low in organic matter, quinoline is more likely to become strongly bound to the soil and less likely to move to ground water. However, in its strongly bound state, the pollutant is also less likely to be broken down by microrganisms.

The researchers detail their results in the just released current issue of the Soil Science Society of America Journal in a paper, "Quinoline Sorption on Kaolinite-Humic Acid Complexes."

Chorover's co-authors are Mary Kay Amistadi, research support associate in Penn State's Department of Agronomy; Dr. William D. Burgos, Penn State assistant professor of civil and environmental engineering; and Dr. Patrick G. Hatcher, professor of environmental chemistry, Ohio State University.

The study also shows that mineral interactions with humus were key to whether quinoline was retained in soil. When humic substances coated the mineral phase, quinoline was less likely to adhere. However, when the mineral phase was uncoated, quinoline bound strongly. The data also suggest that quinoline is relatively mobile in subsurface soil environments.

Chorover says the next step in the research program will focus on what happens during quinoline's interactions with microorganisms. He notes that preliminary data suggests that "enrichment cultures" may be used to inoculate the soil and break down the pollutant.

"Understanding the binding of pollutants to mineral and organic constituents is key to developing our capability to decontaminate soils. One of the main goals of our research is to see whether strongly bound pollutants can still be broken down in the soil or whether they are inaccessible to microorganisms," he adds.

The research was supported in part by a grant from the U.S. Department of Energy, Office of Biological and Environmental Research Joint Bioremediation Program.

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EDITORS: Dr. Chorover is at 814-863-5394 or jdc7@psu.edu by email.


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