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

Abstract

Investigation into mechanisms leading to the development, spread and persistence of soil water repellency following contamination by crude oil. Can. J. Soil Sci. 80: 595-606. 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. Nous avons cherché à déterminer 1) si l'imperméabilisation du sol à l'eau aux emplacements de déversement de pétrole brut serait due à la sorption par le sol des composés pétroliers en phase vapeur, 2) si son extension se fait par dispersion et par mélange mécanique et 3) si la persistance est due à l'association des agents causaux avec les humines et avec les surfaces des minéraux du sol. Formation -Des sols facilement mouillables devenaient imperméables à l'eau au bout de 60 j de stockage en présence de matière du soussol pollué par le pétrole. Ces changements étaient imputés à la sorption par le sol des composés pétroliers en phase vapeur émanant des matières contaminées. Nous citons des documents publiés selon lesquels les composés pétrochimiques en phase liquide sont également capables de causer l'imperméabilisation. À cet égard nous expliquons comment nous avons testé, et finalement rejeté, l'hypothèse voulant que la sorption des asphaltènes du pétrole seraient l'unique cause du phénomène. Extension -Nous montrons comment le mélange d'une unité massique de sol imperméabilisé avec 2 à 4 unités de sol jouxtant mouillable était suffisant pour imperméabiliser gravement les sols provenant de trois emplacements. Persistance -L'hydrophobicité observée aux emplacements d'anciens déversements de pétrole brut est très résistante aux mécanismes naturels d'altération sur place et aux t...

Longevity of soil water repellency in a former wastewater disposal tree stand and potential amelioration

“…Whatever breakdown has occurred since has been insufficient to eliminate soil WR. This is in agreement with findings from crude oil-contaminated sites studied in Canada by Roy and McGill (2000), but contrasts the typically shorter-lived increases in soil WR associated with the transformation and condensation of organic compounds in the soil during vegetation fires (Doerr et al, 2000).…”

Methods for determining soil water repellency on field‐moist samples

“…Examples include waxy substances from leaves [ Passialis and Voulgaridis , 1999], root exudates [ Dekker and Ritsema , 1996a; Doerr , 1998], fungi [ Fidanza et al , 2007], microbes [ Hallett and Young , 1999] and decomposing organic matter [ McGhie and Posner , 1981]. Furthermore soil water repellency might also develop locally because of oil spills [ Roy and McGill , 2000b], extensive oil fires as observed in Kuwait [ Suleiman and Bhat , 2004], or wildfires [ DeBano , 2000]. Recently it has also been shown that regular irrigation applications of treated sewage water can lead to the development of soil water repellency due to dissolved organic substances in the sewage water [ Tarchitzky et al , 2007].…”

Effect of crude petroleum on water repellency in a clayey alluvial soil

“…Although some authors have shown that in naturally occurring water repellent soils, increasing organic matter concentrations are positively correlated with higher water repellency values (Vogelmann et al 2013), researchers investigating soils that have become water repellent due to petroleum contamination have found that water repellency is due more to the kind of SOM rather than the amount (Roy and McGill 2000), and that the addition of organic amendments may reduce water repellency by several orders of magnitude, apparently by increasing the water holding capacity of the soil (Córdova 2010, cited in Adams 2011. This may maintain the in situ water content above the critical threshold at which water repellency becomes manifest.…”

“…In addition to the type and amount of SOM being correlated with soil hydrophobicity, texture has also been implicated. Generally, soils with higher clay contents are less likely to suffer water repellency in the field, due to the greater surface area available, and greater water holding capacity (Vogelmann et al 2013;Roy and McGill 2000). Thus, it is important to exercise caution when using this particular model-applying only to this soil or other, very similar soils in terms quantity and type of clay and organic matter.…”