Investigation into mechanisms leading to the development, spread and persistence of soil water repellency following contamination by crude oil

We investigated mechanisms by which soil water repellency may develop, spread and persist at old crude oil spill sites. We tested if its development may be due to soil sorption of vapour-phase petroleum compounds, its spread due to mechanical dispersal and mixing, and its persistence due to associat...

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Bibliographic Details
Published in:Canadian journal of soil science 2000-11, Vol.80 (4), p.595-606
Main Authors: Roy, J.L, McGill, W.B
Format: Article
Language:English
Subjects:
fulvic acids
humic acids
hydrocarbons
petroleum
petroleum asphaltenes
polluted soils
repellency
soil pollution
sorption
vapor phase petroleum compounds
volatile compounds
water repellent soils
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Summary:We investigated mechanisms by which soil water repellency may develop, spread and persist at old crude oil spill sites. We tested if its development may be due to soil sorption of vapour-phase petroleum compounds, its spread due to mechanical dispersal and mixing, and its persistence due to association of causative agents with humin and soil mineral surfaces. Development. Readily wettable soils acquired water repellency following 60 d of storage in the presence of oil-contaminated subsoil material. Change in soil wettability was attributed to soil sorption of vapour-phase petroleum compounds emanating from the contaminated material. We cite literature reports indicating that liquid-phase petroleum compounds can also cause soil water repellency. To that effect, we report how we tested and finally rejected the hypothesis that sorption of petroleum asphaltenes might be the sole cause of soil water repellency. Spread. We describe how mixing one mass unit of water-repellent soil with two to four mass units of wettable adjacent soil is sufficient to impart severe water repellency to soil mixes from three sites. Persistence. The water-repellent condition found at old crude oil spill sites is highly resistant to natural weathering and nondestructive extraction procedures. We show here that it also resists exhaustive extraction with 0.1 M NaOH and conclude that causative agents of soil water repellency are at least not solely associated with humic and fulvic acid fractions. Key words: Soil water repellency, asphaltenes, cultivation, humic acids, sorption, crude oil
ISSN:0008-4271
1918-1841
DOI:10.4141/S99-091