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Effect of crude petroleum on water repellency in a clayey alluvial soil
Marín-García, D.C.; Adams, R.H. & Hernández-Barajas, R.
Abstract
Water repellency was studied in a clayey soil
contaminated with light (36.6°API), medium (27.4°API),
and heavy (15.0°API) crude oils at concentrations of 1, 2,
4, and 8 %. Higher water drop penetration times (WDPTs)
were observed in dry soil as the density and concentration
of petroleum increased, resulting in logarithmic functions
which could be modeled from API gravity and oil concentration
(R2 = 0.986). WDPTs varied from 2.1 to 8.7 s
with light crude, 11.1 to 44.9 s for medium crude, and 39.4
to 134.5 s for heavy crude. Only heavy crude-contaminated
soil, at >2 % resulted in significant hydrophobicity. Critical
moisture content in these hydrophobic soils was
insignificant at moisture contents >12.8 % at 2 % heavy
crude and >14.6 % at 4 % heavy crude. Only at a concentration
of 8 % heavy crude was the critical moisture
content ( >17.2 %) higher than that observed in the field
during the dry season (14.8 %). Thus, only (clayey) soil
contaminated with very high concentrations of heavy oil is
likely to present hydrophobicity in this monsoon climate.
This study shows that the development of models to
describe soil water repellency may be useful to propose
remediation criteria which reduce or avoid the risk of water
repellency.
Keywords
°API; Critical moisture content; Hydrophobicity; Oil contamination
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