Soil-water partition coefficients

The calculation is illustrated in Table 1.5.5 for pentachlorophenol. The experimental aqueous solubility is 14.0 g/m3 at a pH of 5.1. The environmental pH is 7. Higher environmental pH increases the extent of dissociation, thus increasing the Z value in water, increasing the apparent solubility, decreasing the apparent KqW and Henry s law constant and the air-water partition coefficient, and decreasing the soil-water partition coefficient. 

Calculated Zw values and some partition coefficients at different environmental pHs for pentachlorophenol (PCP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and p-cresol at 25°C. Kaw is the air-water partition coefficient and Ksw is the soil-water partition coefficient... 

Girvin, D.C. and Scott, A.J. Polychlorinated biphenyl sorption by soils measurement of soil-water partition coefficients at equilibrium, Chemosphere, 35 (9) 2007-2025. 1997. 

As discussed earlier, the proportion of the molecules in the vapor state within the soil near a source is around 6 orders of magnitude less than the sorbed or dissolved portions. This condition was stated for 50% moisture saturation. For extremely dry soils, this ratio becomes even more pronounced. Phelan and Barnett defined a soil-air partitioning coefficient, Kd>, in a manner parallel to the soil-water partitioning coefficient, Kd [12] ... 

Abiotic soil desorption measurements are probably the most important tests to precede measurement of microbial degradation. Desorption tests measure the site-specific soil/water partition coefficients for the contaminants of interest. Several experimental protocols are available for measuring partition coefficients (Wu Gschwend, 1986 Rogers, Tedaldi Kavanaugh, 1993). At the two extremes of bioavailability and biodegradability, contaminants can either be detected near their solubility limit or can be undetectable in the aqueous phase. Measurements of aqueous phase and soil phase concentrations in equilibrium may... 

The soil-water partition coefficient, soil-water is a conditional and not a fundamental physicochemical compound property. Xsoii-water is included here because of its great practical significance. Its value depends on a number of soil and solution characteristics, such as the organic carbon (OC) or organic matter (OM) content, clay content and type, pore volume, pore size and distribution, and solution conditions. soil—water can be defined as the ratio of the sorbate s mass sorbed per unit volume of soil to the mass dissolved per unit volume of aqueous phase with both phases at equilibrium ... 

Soil-Water partition coefficient normalised for organic carbon content Soil-Organic matter partition coefficient Octanol-Water partition coefficient Apparent Octanol-Water partition coefficient... 

The soil-water partition coefficients were obtained using three different soils from different locations from the PPI sites at several depths with four harbinger compounds (1,4-dichlorobenzene, 1,2 dichloroethane, 1,1,2,2-tetrachloroethane, and 1,1,2-trichloroethane). The soils provided a broad horizon and chemicals are major ones of concern at the sites. Average values were calculated from triplicate samples and used in plots mentioned above to determine log Koc and log Kmin, which were correlated to log Kow to arrive at the general predictive equation for PPI soils given below [7] ... 

Kommalapati RR,Valsaraj KT, Constant WD (2000) Soil-water partition coefficients, adsorption/desorption hysteresis, desorption kinetics and bioavailability of chlorinated organic compounds at the PPI site. Submitted to Hazardous Substance Research Center, Louisiana State University, Baton Rouge, LA... 

They carry out this process by extrapolating the octanol-water partition coefficient (jBTow) of a particular organic contaminant to the SOM-water partition coefficient (K0 and finally to the soil-water partition coefficient (KD) as follows. Consider that... 

Physical and Chemical Properties. Several important physical properties of 2-butoxyethanol and 2-butoxyethanol acetate have yet to be experimentally determined. These include their octanol-water and soil-water partition coefficients, Henry s law constants, and bioconcentration factors in aquatic organisms. These data are important in estimating the fate of tlie released compounds in the environment and in determining the potential for human exposure. However, reliable estimated values for these parameters are available (ASTER 1995a, 1995b Howard 1993 HSDB 1995 Lyman et al. 1982) and there is no critical need for experimental confirmation of the estimated values. 

Soil sorption partition coefficient (or soil-water partition coefficient), denoted as Kqc or logKoc accounts for sorption from water into soil. Because this often depends primarily on the soil s organic carbon content, measured values are usually normalized for the organic carbon (OC) content of soil, in which case the soil sorption equilibrium constant is expressed as... 

Table IX, Organic Carbon Soil-Water Partition Coefficients...

Retardation Parameters Soil fraction organic carbon (foe) content. Soil-water partitioning coefficient (k ). For organic constituents, estimate k,/ = K0Cxfoc. Measure foe on representative background soil samples or use conservative default value per soil type. For metals, run soil leaching test (SPLP) to estimate kj. 

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