Determination of oil content of oil contaminated soil

Characterization of disaggregated nonwettable surface soils found at old crude oil spill sites. Can. J. Soil Sci. 78: 331-344. We characterized some of the physical, chemical, and microbiological properties of soils that have become severely water-repellent and disaggregated several years or decades following oil contamination. A growing number of patches (usually <2 ha) of disaggregated water-repellent soils have recently been discovered throughout the province of Alberta at 20 to 50-yr-old crude oil spill sites. The disaggregated water-repellent soil is usually confined to a dry and powdery surface layer 10 to 15 cm deep, which no longer smells, feels, or looks like it contains any oil. These soils appear to have permanently lost the ability to support plant growth and recover through natural processes. We analyzed samples of disaggregated water-repellent and adjacent normal soils from three old crude oil spill sites to provide a background set of information about these poorly known soils and assist in the development of hypotheses concerning the development and persistence of soil water repellency and structural degradation. Compared with normal adjacent soils, disaggregated nonwettable soils are characterized by: (1) a strong resistance to wetting, as determined by the molarity of ethanol droplet (MED) test; (2) a smaller population of viable and culturable microorganisms, which contains at least some representatives from nonspore-forming bacterial genera; (3) a high content of mineral N and total C, a comparable pH and ratio of exchangeable cations, but a lower cation exchange capacity; (4) a slightly lower clay content, as determined by the Bouyoucos hydrometer method; (5) a comparable water desorption behaviour following forced saturation with water; (6) dry aggregates of a smaller mean weight diameter (MWD), as determined by dry sieving and scanning electron miscroscopic (SEM) analyses; (7) slightly less pronounced thermal reactions when heated up to 525°C, as determined by differential thermal analyses (DTA); and (8) a reduced ability to support plant growth. From these observations, we infer that disaggregated water-repellent soils found at old crude oil spill sites do not differ appreciably from normal adjacent soils in terms of their inorganic chemistry. Nonwettable and adjacent wettable soils differ mostly in terms of some physical and biological characteristics, which probably stem from differences in the quality of the organic matter they contain. Key words:Crude oil spills, petroleum hydrocarbons, soil water repellency, soil disaggregation, soil hydrophobicity Roy, J. L. et McGill, W. B. 1998. Caractérisation des sols de surface non mouillables désagrégés observés aux anciens emplacements de déversement de pétrole brut. Can. J. Soil Sci. 78: 331-344. Nous avons caractérisé certaines des propriétés physiques, chimiques et microbiologiques de sols qui sont devenus fortement hydrophobes et désagrégés plusieurs années, voire des décennies, après leur contamination par du pétrole brut un nombre crois...

Section: Site Selection and Soil Preparationmentioning

confidence: 99%

Characterization of disaggregated nonwettable surface soils found at old crude oil spill sites

Roy¹,

McGill²

1998

“…The concentration of solvent-extractable organics was determined gravimetrically as described by McGill and Rowell (1980). Briefly, the extracted organics dissolved in solvent were concentrated on a rotary evaporator, transferred into preweighed aluminum dishes, and allowed to dry to constant mass in a fume hood.…”

Section: Solvent Extraction Of Putative Water-repellent Substances Prmentioning

confidence: 99%

Petroleum residues as water-repellent substances in weathered nonwettable oil-contaminated soils

Roy¹,

McGill²,

Rawluk³

1999

Roy, J. L., McGill, W. B. and Rawluk, M. D. 1999. Petroleum residues as water-repellent substances in weathered nonwettable oil-contaminated soils. Can. J. Soil Sci. 79: 367-380. Some soils develop severe water repellency several years or decades following oil contamination. We previously reported on the characteristics of three such soils. Here we report on the characteristics of putative water-repellent substances in them. We examined the effectiveness of various polar, nonpolar and amphiphilic solvents for removal of water-repellent substances in three nonwettable soils. Only the amphiphilic solvent mixture isopropanol/14.8 M ammonia (7:3, vol/vol) (IPA/NH 4 OH) completely eliminated soil water repellency in all three soils. We thus define putative water-repellent substances as those substances whose removal from soil by IPA/NH 4 OH removes water repellency. High-resolution CPMAS 13 C-NMR spectroscopy and thermal desorption followed by conventional gas chromatography/mass spectroscopy with electron impact ionization (GC/EI/MS) and GC/MS with chemical ionization (GC/CI/MS) were used to characterize extracted putative water-repellent substances. We conclude that: (i) the identified representatives of these substances consist mostly of homologous series of long-chain and polycyclic aliphatic organic compounds; namely, n-fatty acids, n-alkanes, and cycloalkanes, and that (ii) they are of petroleum origin rather than plant or microbial origin.

“…During the second run, precautions were taken not to disturb the soil mass during and between extraction steps. Extractable material obtained after each extraction step was determined gravimetrically, as described by McGill and Rowell (1980). All sequential extraction steps were performed in triplicate with 175-200 mL solvent for 24 h at the refluxing rate of 10 cycles h -1 .…”

Section: Water Repellency Following Sequential Soxhlet Extractions Wimentioning

confidence: 99%

Flexible conformation in organic matter coatings: An hypothesis about soil water repellency

Roy¹,

McGill²

2000

Flexible conformation in organic matter coatings: An hypothesis about soil water repellency. Can. J. Soil Sci. 80: 143-152. Some soils develop severe water repellency several years or decades following oil contamination. We previously reported that soil water repellency is completely eliminated by extraction with amphiphilic solvents, but barely reduced by extraction with nonpolar solvents. We report here on solvent-induced reversible soil water repellency. Our results indicate that: (i) water repellency is completely eliminated following extraction with amphiphilic solvent, but partially restored following subsequent exposure to nonpolar, non-H-bonding solvent; (ii) extraction with nonpolar, non-H-bonding solvent generates water repellency in readily wettable control wettable soils, but not in pristine wettable soils, and (iii) repeated sequential extractions alternating between amphiphilic and nonpolar, non-H-bonding solvent increase extractable material and reduce the magnitude of solvent-induced soil water repellency with time.We attribute reversible soil water repellency to solvent-induced changes in the conformation of causative agents of soil water repellency. Recent literature reports on the structural flexibility of "insoluble" organic macromolecules are discussed for supporting evidence. We propose that exposure to nonpolar, non-H-bonding solvents induces stretching of surface-exposed, nonpolar moieties (i.e. alkyl chains), whereas exposure to polar, H-bonding solvents induces their coiling. These solvent-induced conformational changes are retained upon solvent removal. Our results indicate that the wettability of oil-contaminated soils depends on both the interfacial conformation and the fractional coverage of their surface-exposed nonpolar moieties. Certains sols acquièrent une grave imperméabilisation à l'eau plusieurs années, voire des décennies, après une contamination par le pétrole. Dans une précédente communication, nous signalions que l'imperméabilité à l'eau est complètement éliminée par extraction au moyen de solvants amphiphiles, mais qu'elle est à peine diminuée en présence de solvants non polaires. Nous traitons ici de l'imperméabilité réversible induite par des solvants. Il ressort de nos observations que i) ce type d'imperméabilité est éliminé complètement après extraction au moyen de solvants amphiphiles, mais qu'il est rétabli partiellement après exposition subséquente à un solvant non polaire sans liaison hydrogène, ii) l'extraction par un solvant de ce type provoque l'imperméabilité dans les sols contaminés témoins à mouillage facile, mais pas dans les sols mouillables non contaminés et iii) ces extractions séquentielles répétées, utilisant en alternance un solvant amphilile et un solvant sans liaison hydrogène non polaire produisent davantage de matériel extractible et réduisent à terme l'importance de l'hydrophobicité du sol due au solvant. Cette réversibilité de l'hydrophobicité du sol est attribuée au changement solvanto-induit de conformation des agents causaux de l'hydrophobic...