Sorption coefficient usefulness

Winget, P., Cramer, C.J., Truhlar, D.G. (2000) Prediction of soil sorption coefficients using a universal solvation model. Environ. Sci. Technol. 34, 4733 1740. 

Fig. 9. Parametric simulation using the MSD model of water flux vs feed concentration as a function of organic sorption coefficient, where for A,...

Because many studies have shown a direct relationship between pesticide sorption and organic carbon content of sod, attempts have been made to develop a universal sorption coefficient based on sorption of the pesticide to sod organic carbon (44). Sorption based on sod organic carbon is expressed as C, where is pesticide sorbed per unit mass sod organic carbon, and C is pesticide solution concentration after equdibration. If. is the fraction of organic carbon, can be obtained from i in the equation. Assumptions in the use of this approach include... 

Indirect methods of estimating sorption have been used when actual measurement of sorption isotherm is impossible (44). For instance, sorption coefficients have been estimated from soil organic carbon and a specific surface of soil, and from semiempidcal equations using pesticide properties. 

Bahnick, D. A., Doucette, W. J. (1988) Use of molecular connectivity indices to estimate soil sorption coefficients for organic chemicals. Chemosphere 17, 1703-1715. 

Pollutants with high VP tend to concentrate more in the vapor phase as compared to soil or water. Therefore, VP is a key physicochemical property essential for the assessment of chemical distribution in the environment. This property is also used in the design of various chemical engineering processes [49]. Additionally, VP can be used for the estimation of other important physicochemical properties. For example, one can calculate Henry s law constant, soil sorption coefficient, and partition coefficient from VP and aqueous solubility. We were therefore interested to model this important physicochemical property using quantitative structure-property relationships (QSPRs) based on calculated molecular descriptors [27]. 

Frequently it is convenient, when conducting sorption experiments, to use a cosolvent such as methanol to facilitate transfer of a volatile or insoluble solute. Equation 31 may be used to estimate the effect of the cosolvent on measured sorption coefficient. If fc equals 10- and a is conservatively chosen as unity, the methanol is predicted to decrease the sorption of anthracene (ac = 9.76 log Kow = 4.54 50) by 1% relative to the case of no cosolvent. The effect of the cosolvent should be smaller for solutes with smaller HSA (or KQW), which is consistent with the observed negligible impact of methanol at f. < 10 3.6 52). ... 

The validation data set constitutes 42 PAHs (Table 11) comprising both unsubstituted and substituted compounds with a wide range of physical and chemical properties. Predictive models developed for PAH compounds in the training data set (Fig. 15) were used to predict values of sorption coefficients. All predicted and observed values were regressed, and recorded significant R2 values as shown in Figs. 16 and 17, while the difference between such values are presented in Table 11. 

Celorie, J.A., Woods, S.L., Vinson, T.S., and Istok, J.D. A comparison of sorption equilibrium distribution coefficients using... 

Equilibrium thermodynamics is one of the pillars supporting the safety analyses of radioactive waste repositories. Thermodynamic constants are used for modelling reference porewaters, calculating radionuclide solubility limits, deriving case-specific sorption coefficients, and analysing experimental results. It is essential to use the same data base in all instances of the modelling chain in order to ensure internally consistent results. 

Isophorone has a water solubility of 12,000 ppm, a log octanol/water partition coefficient of 1.67, a Henry s Law constant of 4.55 X 10 atm m mof, a vapor pressure of 0.3 mm Hg at 20 C, a log sediment sorption coefficient of approximately 1.46, and a log bioconcentration factor (BCF) of 0.85. Isophorone is released to air and water from its manufacturing and use. Based on its water solubility, some isophorone may wash out of the atmosphere however, only limited amounts will be washed out because of the short atmospheric half-life of isophorone. Particularly during the day, when hydroxyl radical (HO) concentrations are highest, very little atmospheric transport will occur due to its fast reaction with HO. ... 

In order to evaluate the ability of natural organic materials to sorb organic pollutants, it is useful to define an organic carbon normalized sorption coefficient ... 

While the exact sorption mechanism may not be clear, the available literature suggests the following generalizations. First, coarser particles (e.g., silica sand) exhibit less binding per mass of solid than corresponding finer particles made of the same material (e.g., porous silica). This is presumably due to the influence of increased solid surface area per mass of sorbent. Thus, values of sorption coefficients for minerals (Kimm = Cimin/Ciw.Mr) are more useful if they are normalized to the solid s surface area rather than its mass. The second tendency we see is that for any... 

The ability to predict the behavior of a chemical substance in a biological or environmental system largely depends on knowledge of the physical-chemical properties and reactivity of that compound or closely related compounds. Chemical properties frequently used in environmental assessment include melting/boiling temperature, vapor pressure, various partition coefficients, water solubility, Henry s Law constant, sorption coefficient, bioconcentration factor, and diffusion properties. Reactivities by processes such as biodegradation, hydrolysis, photolysis, and oxidation/reduction are also critical determinants of environmental fate and such information may be needed for modeling. Unfortunately, measured values often are not available and, even if they are, the reported values may be inconsistent or of doubtful validity. In this situation it may be appropriate or even essential to use estimation methods. 

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