S.C. Wetzel¹, M.K. Banks¹ and A.P. Schwab²

¹Department of Civil Engineering and ²Department of Agronomy, Kansas State University, Manhattan, KS, 66506


Contamination of soil by polycyclic aromatic hydrocarbons (PAHs) is of considerable importance because of their carcinogenic and mutagenic potential. PAHs are non-polar hydrophobic organic compounds characterized by two or more fused benzene rings in various arrangements. Although these compounds occur ubiquitously, the primary source to the environment is anthropogenic activity, particularly through the incomplete combustion of petroleum hydrocarbons. As a result, PAHs can be highly sorbed to soil organic matter, thus making remediation difficult. Recent evidence suggests the potential exists for enhanced biodegradation of toxic organic compounds in the presence of rhizosphere soil due to increased indigenous microbial activity and root exudations. The study utilizes three soil types: sterile, rhizosphere and non-rhizosphere. The soils were amended with anthracene and pyrene at concentrations of 100 ppm and were placed in small bioreactors in quadruplicate. Two amendments were added daily to the soils, with half the bioreactors receiving 0.01 M calcium chloride solution, while the remaining reactors received an organic acid mixture simulating root exudation in the rhizosphere. The soil treatments were maintained at optimum water content. The bioreactors were disassembled at predetermined times over a 56 day period and a mass balance was performed using gas chromatography.


polycyclic aromatic hydrocarbons, rhizosphere, biodegradation

This paper is from the Proceedings of the 10th Annual Conference on Hazardous Waste Research 1995, published in hard copy and on the Web by the Great Plains/Rocky Mountain Hazardous Substance Research Center.