Comparison of soil-to-water suspension ratios for determining electrical conductivity of oil-production-water-contaminated soils

Abstract

Soil salinity caused by oil-production-water (brine) contamination is a major issue in regions of oil and gas development. However, rapid site assessment tools such as soil-to-water suspension electrical conductivity (EC) methods and conversion equations have not been previously calibrated and validated for brine-contaminated soils. Our objective was to compare three soil EC methods and derive conversion equations for EC values commonly observed at brine-spill sites. Brine-contaminated soils from western North Dakota were assessed for salinity. Electrical conductivity was determined using 1:1 and 1:5 soil-to-water suspensions (EC 1:1 , EC 1:5 ) and saturated paste extracts (EC e ). Soil EC equilibration times for soil-to-water suspensions were also assessed. Significant relationships (r 2 = 0.91 to 0.97, P < 0.0001) existed among all methods for EC values ranging between 0 and 126 dS m −1 . Conversion equations were developed based on these relationships and then validated with an independent data set. These new equations reduced EC e prediction errors by 2 to 4.5 times when compare with 14 predictive equations reported in the literature. The conversion equations developed here are recommended for use in remediation efforts when converting EC 1:1 and EC 1:5 data to EC e on brine-contaminated and noncontaminated soils where EC e is highly correlated to Na concentrations.Key words: soil salinity, electrical conductivity, oil production, saturated paste, soil-to-water suspension, brine.Résumé : La salinité du sol résultant de la contamination de ce dernier par l'eau des puits de pétrole (saumure) est un problème majeur dans les régions où l'on exploite des nappes de pétrole et de gaz. Cependant, les outils d'évaluation rapide des sites comme la conductivité électrique (CE) d'une suspension de sol dans l'eau et les équations de conversion n'ont jamais été étalonnés ni validés pour les sols contaminés de la sorte. Les auteurs voulaient comparer trois méthodes reposant sur la CE et dériver les équations de conversion pour les valeurs les plus couramment observées là où de la saumure a été accidentellement déversée. Pour cela, ils ont évalué la salinité de sols de l'ouest du Dakota Nord pollués par de la saumure. La conductivité électrique a été déterminée grâce à des suspensions 1: 1 et 1: 5 de sol dans l'eau (EC 1:1 , EC 1:5 ) et à des extraits de pâte de papier saturée (EC e ). Parallèlement, ils ont établi le temps nécessaire pour que les suspensions de sol dans l'eau parviennent à la CE d'équilibre. Il existe des relations significatives (r 2 = 0,91 à 0,97, P < 0,0001) entre les différentes méthodes testées pour les valeurs de la CE situées entre 0 et 126 dS par m. Des équations de conversion ont été élaborées d'après ces relations, puis validées avec un jeu de données indépendant. Les nouvelles équations réduisent les erreurs de prévision pour EC e par un facteur de 2 à 4,5 comparativement à 14 équations similaires trouvées dans la littérature. Les auteurs préconisent l'utilisation de leurs équations da...

Assessment of Saturated Soil Paste Salinity from 1:2.5 and 1:5 Soil-Water Extracts for Coarse Textured Soils

“…The results of our study are similar to reportedthose reported by other researchers who found that highly (Ozcan et al, 2006;Sonmez et al, 2008;Aboukila and Norton, 2017) or 1:5 extracts (Ozcan et al, 2006;Sonmez et al, 2008;Chi and Wang, 2010;Khorsandi and Yazdi, 2011;He et al, 2013;Klaustermeier et al, 2016;Monteleone et al, 2016;Aboukila and Norton, 2017). Neither the slopes nor the R 2 are changed much when intercepts are not included in the regression equations (Table 1).…”

“…The computed ECe for 1:5 soil to water ratios using the regression equations of Chi and Wang (2010), Khorsandi and Yazdi (2011), Monteleone et al (2016), and Klaustermeier et al (2016) were 0.98, 3.57, 5.57, and 3.31 dS m -1 , respectively. The calculated ECe means were significantly different than mean of the actual measured ECe (Table 4).…”

“…Good relationships have been reported between ECe and 1:1 extracts and suspensions (Wagenet and Jurinak, 1978;Fowler and Hamm, 1980;Hogg and Henry, 1984;Pitman et al, 2002;Zhang et al, 2005;Klaustermeier et al, 2016;Monteleone et al, 2016), 1:2 extracts and suspensions (McKenzie et al, 1983;Hogg and Henry, 1984;Khorsandi and Yazdi 2007;Monteleone et al, 2016), 1:2.5 extracts (Ozcan et al, 2006;Sonmez et al, 2008;Aboukila and Norton, 2017) and 1:5 extracts and suspension (Alavi Panah and De Dapper, 2001;Khorsandi and Yazdi, 2011;He et al, 2013;Klaustermeier et al, 2016;Monteleone et al, 2016;Aboukila and Norton, 2017).…”

“…In contrast to SP extracts, soil-water extracts can be composed and derived in a much easy way. To determine the EC values of soils, soil-water extracts of 1:1, 1:2, 1:2.5, 1:5, and 1:10 have been commonly utilized in soil laboratories (Hogg and Henry, 1984;Zhang et al, 2005;Sonmez et al, 2008;Chi and Wang, 2010;Khorsandi and Yazdi, 2011;He et al, 2013;Klaustermeier et al, 2016;Monteleone et al, 2016;Aboukila and Norton, 2017). The 1:5 ratio is preferably used as a method for calculating soil salinity in Australia, China, and Central Asia (Shirokova et al, 2000;Wang et al, 2011) as well as 1:1 ratio in the United States and Canada (Hogg and Henry, 1984;He et al, 2013).…”

“…The advantages of soil-water extracts are that they require less labor, quicker and can be useful when the objectives are to evaluate the relative changes rather than the absolute solute content (McKenzie et al, 1983;Rhoades, 1996). Since soil-water extract methods can be conducted with relative ease, there have been theoretical relationships developed to convert soil-water extraction results to a SP extraction equivalents (USDA, 1954;Hogg and Henry, 1984;Zhang et al, 2005;Sonmez et al, 2008;Chi and Wang, 2010;Khorsandi and Yazdi, 2011;He et al, 2013;Klaustermeier et al, 2016;Monteleone et al, 2016;Aboukila and Norton, 2017). Despite the reports of highly correlated relationships between the two methods for particular soils, converted values are often imprecise and inaccurate (Wagenet and Jurinak, 1978;Franzen, 2003) especially, if conversion equations are applied to larger regions or different soils (He et al, 2013).…”