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Treatment of water-repellent petroleum-contaminated soil from Bemidji, Minnesota, by alkaline desorption
Adams, R. H.; Cerecedo-López, R. A.; Alejandro-Álvarez, L. A.; Domınguez-Rodrıguez, V. I. & Nieber, J. L.
Abstract
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.
Keywords
Critical moisture content; Hydrocarbon; Hydrophobicity; Remediation
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