Relationship between Water Repellency and Native and Petroleum-Derived Organic Carbon in Soils
- J. L. Roy *a,
- W. B. McGillb,
- H. A. Lowenc and
- R. L. Johnsond
- a Imperial Oil Resources, Research Centre, 3535 Research Rd. N.W., Calgary, AB, Canada T2L 2K8
b College of Science and Management, Univ. of Northern British Columbia, 3333 University Way, Prince George, BC, Canada V2N 4Z9
c Matrix Solutions Inc., 230, 319-2 Avenue S.W., Calgary, AB, Canada T2P 0C5
d Alberta Research Council, P.O. Box 4000, Vegreville, AB, Canada T9C 1T4
Some soils develop severe and persistent water repellency following contamination with crude oil. This study was conducted to characterize and compare the spatial distribution of soil water repellency and residual oil contamination at 12 such sites. The molarity of ethanol droplet (MED) test was used to assess soil water repellency and the content of dichloromethane-extractable organics (DEO) was used to quantify residual oil in soil. We found a relatively strong positive correlation between MED and DEO in soil (r 2 = 0.74). Both variables tended to decrease abruptly with depth at 11 of the 12 study sites. Dichloromethane-extractable organics similarly decreased with depth in control adjacent soil (MED = 0 M), but from an average concentration one to two orders of magnitude lower than in water-repellent soil. Using data from corresponding control adjacent and water-repellent soils, we determined that approximately 29 and 10% of measured total organic carbon in water-repellent A- and B-horizon soil, respectively, consists of dichloromethane-insoluble organic carbon of petroleum origin. We propose that this fraction contains most of the causative agents of soil water repellency at the studied sites.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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