A pipeline right-of-way contaminated with light crude in 1979 and subsequently burned shows severe hydrophobicity, poor infiltration rates, and loss of vegetative cover. To evaluate alkaline desorption as a treatment method, surface soil samples were collected and analyzed pre- and post-treatment. Samples had total petroleum hydrocarbon concentrations of 2800–63,100 mg/kg, severe water repellency, critical moisture 2–5 times above the in situ moisture content, but no acute toxicity. Thus, water repellency, rather than toxicity, is causing the loss of vegetation. Samples were treated with 0.1 N NaOH in two doses (1:3; soil/solution), with complete drainage between doses. Finally, each soil sample was washed with an equal volume or water and allowed to drain completely. For more hydrophobic samples, repeated treatments, without rinsing between each treatment, were made. Post-treatment, the samples were re-analyzed for water repellency and critical moisture content. In samples with initial water repellency values in the range of 5.0–6.7 M, the repellency was reduced 94–100 % and below critical levels to avoid soil hydrophobicity in field conditions. The other samples with initial water repellency values in the range of 10–13 M could not be recovered with single treatment, but sequential treatments reduced the hydrocarbon content up to 87 % and reduced the hydrophobicity to levels low enough or nearly low enough to avoid severe water repellency in the field. Currently, field studies are being carried out to evaluate this treatment method at the site, as a stand-alone method and in combination with organic amendment.
|Original language||English (US)|
|Number of pages||12|
|Journal||International Journal of Environmental Science and Technology|
|State||Published - Sep 1 2016|
Bibliographical noteFunding Information:
We would like to thank the US Geological Survey, in conjunction with the Minnesota Pollution Control Agency for financial support and access to the contaminated site, and also, the University of Minnesota and the Universidad Juárez Autónoma de Tabasco for additional funding and logistical support. This study was carried out with grants from the 2014 and 2015 Request for Proposals (RFPs) for Research at the National Crude Oil Spill Fate and Natural Attenuation Research Site titled: Evaluation of Remediation Methods for Water-Repellent Petroleum Contaminated Sites; and Evaluation of Water Repellency and Vegetation Composition at the Bemidji Oil Spill Site. Funding was provided from the National Crude Oil Spill Fate and Natural Attenuation Research Site, a collaborative venture of the USGS, Enbridge Energy Limited Partnership, the Minnesota Pollution Control Agency, and Beltrami County. Additional support was provided through the U.S. Geological Survey’s Toxic Substances Hydrology Program. J.L. Nieber's effort on this project was partially supported by the USDA National Institute of Food and Agriculture, Hatch/Multistate project 12-059.
© 2016, Islamic Azad University (IAU).
- Critical moisture content