|HUNDAL, LAKHWINDER - IOWA STATE UNIVERSITY
|THOMPSON, MICHAEL - IOWA STATE UNIVERSITY
|CARMO, ANA - IOWA STATE UNIVERSITY
Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2001
Publication Date: N/A
Interpretive Summary: Contamination of ground water by organic pollutants is a serious concern in many locations. To predict the fate and potential risk posed by organic pollutants in soils and sediments, it is necessary to understand how organic pollutants interact with various organic and mineral particles that make up soils and sediments. We have discovered that clay minerals have a wide range in their ability to adsorb a particular organic pollutant known as phenanthrene. We also found evidence that phenanthrene is adsorbed on clays by physical forces rather than forming chemical bonds. Our study will help scientists understand how organic pollutants behave in soils and sediments, and help engineers design better techniques for cleaning up contaminated soils and sediments.
Technical Abstract: Soil and sediments with low organic carbon content commonly retain nonionic hydrophobic compounds (HOCs) to a greater extent than can be explained by partitioning into organic matter alone. Due to their larger surface area and abundance in many soils, smectites may greatly influence the fate and transport of HOCs in the environment. We used phenanthrene as a probe to explore the potential of reference smectites to sorb HOCs from aqueous solutions. Batch experiments were used to construct phenanthrene sorption isotherms, and possible sorption mechanisms were inferred from the shape of the isotherms. Our results demonstrate that smecitites can retain large amounts of HOCs from water. Phenanthrene sorption capacities of the reference smectites investigated in this study were comparable to those of soil clays containing considerable amount of organic matter. Hectorite exhibited the highest sorption affinity and capacity followed by Panther Creek montmorillonite. The lack of correlations between phenanthrene sorption (K'f) and indices of charge or hydrophobicity, suggests that sorption of phenanthrene by smectites is primarily a physical phenomenon. Capillary condensation into a network of nano- or micropores created by quasicrystals is likely to be a dominant mechanism of phenanthrene retention by smectites.