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Common Properties of Chemicals of Concern and Soil Matrices
Published in Cristiane Q. Surbeck, Jeff Kuo, Site Assessment and Remediation for Environmental Engineers, 2021
Cristiane Q. Surbeck, Jeff Kuo
The octanol-water partition coefficient is the ratio of the concentration of a chemical dissolved in octanol (an organic solvent) to the concentration of the chemical dissolved in water (i.e., in the aqueous phase). See a listing in Table 2.2. High Kow values indicate that chemicals are likely to adsorb to organic materials and soil rather than be dissolved in water. These chemicals would be considered hydrophobic (from the Greek words for “water” and “fear”). Low Kow chemicals tend to be hydrophilic (from the Greek words for “water” and “love”), stay dissolved in the aqueous phase, and have low adsorption to soil. In soil and groundwater contamination, we would expect a chemical with high Kow to adsorb onto the soil matrix more than dissolving in water. Figure 2.9 shows a container with water and octanol (an LNAPL), plus a chemical dissolved in both. The dots signify the dissolved chemical. With more dots in the octanol column than in the water column, the chemical is shown to have a higher affinity to octanol. Therefore, the chemical has a high Kow.
Basic Chemical Hazards to Wildlife
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
Hydrophobic chemicals partition from the water column and bioconcentrate in aquatic organisms. Besides the method given above, from Cockerham and Shane, Howard suggests that regression equations can be used to correlate BCF with physical data, such as the octanol–water partition coefficient and water solubility, when the receiving biota do not metabolize the xenobiotic efficiently. If water solubility is greater than 1,000 ppm, the xenobiotic is highly mobile and the half-life will probably be low enough to minimize bioaccumulation. If water solubility is less than 10 ppm, bioaccumulation is expected. For a water solubility between 10 and 1,000 ppm, anyone can guess at bioaccumulation. Appendix 1 gives the solubility in water for several chemicals. The octanol-water partition coefficient, Kow, indicates the affinity for bioaccumulation in fatty tissue. When Kow is greater than 1,000, expect the xenobiotic to accumulate in the food chain in fatty tissue. If less than 500, the chemical will probably not bioaccumulate.
The Effect of Soil Type on Absorption of Toluene and Its Bioavailability
Published in Edward J. Calabrese, Paul T. Kostecki, Principles and Practices for Petroleum Contaminated Soils, 2019
Rita M. Turkall, Gloria A. Skowronski, Mohamed S. Abdel-Rahmaii*
The tissue distribution pattern of oral toluene-derived radioactivity was unaffected by the presence of either soil. In all treatment groups, stomach (the site of administration) and fat exhibited the highest percentage of radioactivity. Pyykko et al.13 also reported high concentrations of radioactivity in the same organs following gastric intubation of rats with 3H-toluene. The high concentration of radioactivity in fat is most likely unmetabolized 14C-toluene which has a high octanol/water partition coefficient. The higher a compound’s octanol/water partition coefficient, the more readily it would be bioaccumulated into biological tissues.23’24 Compared to the oral route, a smaller percentage of radioactivity distributed to fat when 14C-toluene was administered by the dermal route. The difference may be a consequence of slower absorption of radioactivity into blood following dermal exposure, resulting in more extensive metabolism of toluene and less unmetabolized toluene in blood for distribution to tissues including fat.
Degradation of emerging contaminants by acclimated activated sludge
Published in Environmental Technology, 2018
The octanol/water partition coefficient (Kow) is defined as the ratio of a chemical’s concentration in the octanol phase to its concentration in the aqueous phase of a two-phase octanol/water system, which can be used to estimate the hydrophilic property of the specific pollutant. Based on reference [3], the log Kow of the selected pollutants was in the following order: sulfamethoxazole (0.89) < trimethoprim (0.91) < carbamazepine (2.45) < methyl 3,5-dichloro-4-hydroxybenzoate (2.88) < diclofenac (4.5) < triclosan (4.76). The value in the bracket is the corresponding log Kow of the pollutants, indicating that sulfamethoxazole has the highest hydrophilic property, followed by trimethoprim, carbamazepine, methyl 3,5-dichloro-4-hydroxybenzoate, diclofenac and triclosan. In addition, the maximum rate constant was obtained with sulfamethoxazole. Considering the rate constant with the log Kow values, it seems that log Kow of the pollutant was related to its rate constant. The higher the log Kow is, the lower the rate constant is. However, triclosan and carbamazepine are exceptions. Both log Kow and rate constant of triclosan are higher than that of diclofenac and 3,5-dichloro-4-hydroxybenzoic. Furthermore, for carbamazepine, its log Kow is lower than that of triclosan, but its rate constant was far lower than that of triclosan, suggesting that the rate constant of the pollutant was not only related to the log Kow, but also to the physicochemical property of the pollutants. Other factors such as the toxicity of the pollutants to the microorganisms might be also involved.
Utilization of quaternary solvent mixtures for extraction of lipids from Scenedesmus obliquus microalgae
Published in Cogent Engineering, 2020
Sherif Ishola Mustapha, Yusuf Makarfi Isa
The octanol-water partition coefficient (Kow), soil adsorption potential (Koc) and bioconcentration factor (BCF) of the solvent mixtures were determined from the thermodynamic model and the result is presented in Figure 3. The octanol-water partition coefficient (Kow) values are important for predicting a chemical’s potential impact on the aqueous environment. Kow values are also useful for estimating ecosystem risk factors such as bioconcentration factor (BCF) because partition coefficients in octanol-water systems display similarities to partition effects with natural organic substances and biological components in water (Gobas, 2001). Understanding the way that solvents would impact the ecosystem will be helpful for regulatory agencies setting standards, such as maximum contaminant levels in aqueous waste streams. Kow, Koc, and BCF values of various solvent would also be of interest when selecting solvent or solvent mixture with minimal environmental impact prior to bulk or industrial implementation. As shown in Figure 3, the Kow, Koc, and BCF values of the proposed quaternary solvent mixture composition were compared with that of the values of the commonly used binary solvent mixture of chloroform and methanol in varying solvent composition of (1:2 v/v) (Bligh & Dyer, 1959), (1:1 v/v) (Lee et al., 2010), and (2:1 v/v) (Iverson et al., 2001). The result (as shown in Figure 3) shows that the proposed quaternary solvent mixture composition has the least values of 38.75, 51.02, and 5.11 for Kow, Koc, and BCF, respectively. When compared with the binary solvent mixture composition (1:2 v/v), (1:1 v/v), and (2:1 v/v) chloroform-methanol, significant reduction of Kow, Koc, and BCF values were observed confirming the proposed quaternary solvent mixture composition resulted in lower toxicity.
Toward an integrated framework for assessing micropollutants in marine mammals: Challenges, progress, and opportunities
Published in Critical Reviews in Environmental Science and Technology, 2021
Edmond Sanganyado, Ran Bi, Charles Teta, Lucas Buruaem Moreira, Xiaoxuan Yu, Sun Yajing, Tatenda Dalu, Imran Rashid Rajput, Wenhua Liu
Physicochemical properties play a key role in the chemodynamics, bioaccumulation, and biomagnification of micropollutants in marine ecosystems and mammals (Freed et al., 1977). Hence, QSAR tools for predicting toxicity are often based on actual and predicted values of a compound’s octanol-water partition coefficient (log KOW). For example, compounds with an octanol-water partition coefficient (log KOW) > 5 have been shown to have high bioaccumulation potential in marine biota including marine mammals (Brooke & Burns, 2010). However, the log KOW is a useful tool for predicting the bioaccumulation potential of hydrophobic contaminants via dietary intake or dermal absorption, but not for hydrophilic and amphiphilic compounds. Estimating internal dose based on log KOW overlooks the bilayer structure of the epithelial membrane created by phospholipids (O’Connor et al., 2013). Hydrophilic micropollutants exhibit different affinities for the different regions of the bilayer membrane. In addition, the ionizable fraction of micropollutants often has high polarity and low permeability across membranes compared to the neutral fraction (Rendal et al., 2011). Hence, basic and acidic micropollutants at high pH and low pH exhibit high toxicity and bioaccumulation potential, respectively (Rendal et al., 2011). QSAR tools do not normally include inhalation and respiration as potential exposure and elimination pathways for micropollutants. Previous studies showed low log KOW and high octanol-air partition coefficient (log KOA) had high bioaccumulative potential in air-breathing marine mammals (Moses et al., 2015). Hence, micropollutant polarity and hydrophobicity as well as log KOA should be incorporated in QSAR to improve the quality of the predicted toxicity and environmental fate.