Soil sorption

MR = molar refractivity B = class-specific constant parachor = the product of the molar volume and a surface tension term. 

Because of the considerable uncertainties in the estimated boiling temperatures, measured values, which for many chemicals are in the literature, are recommended as input parameters for, for example, vapour pressure computations, so as not to increase the propagated errors unnecessarily. 

The sorption to soil components is a determinant factor for the mobility of contaminants, accounting for their distribution among soil, sediment and water phases. The extent to which chemicals partition between the solid and solution phases in soil, or between water and sediment in aquatic ecosystems, determines the likelihood of the contaminants leaching through the soil or being immobile. The soil sorption hence influences the elution of compounds into groundwater bodies as well as their availability for transformation by soil microbes, their volatilization from soil surfaces and their bioavailability for exposed organisms. 

The extent of sorption to soils is governed by a variety of physico-chemical properties of both the soil and the contaminant. The soils heterogeneous chemistry and physics resulting from the varying proportions of the major 

Sorption occurs if the free energy of interaction between the soil components and the chemical is negative. The underlying processes of physisorption and chemisorption may be caused by (Oepen, Kordel and Klein, 1991)  

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Considerable research has been conducted to investigate the soil sorption and mobiUty of dinitroaniline herbicides. In general, these herbicides are strongly sorbed by soil (354), and sorption has been correlated to both soil organic matter and clay content (355). Dinitroaniline herbicides are not readily leached in most soils (356), although leaching of triduralin is enhanced by addition of surfactants (357). 

Acid amide herbicides are nonionic and moderately retained by soils. The sorption of several acid amide herbicides has been investigated (369). Acetochlor [34256-82-1] is sorbed more than either alachlor or metolachlor, which are similarly sorbed by a variety of soils. Sorption of all the herbicides is well correlated to soil organic matter content. In a field lysimeter study, metolachlor has been found to be more mobile and persistent than alachlor (370) diphenamid [957-51-7] and napropamide [15299-99-2] have been found to be more readily leached (356). 

Sulfonylurea herbicides ate weak acids and, in general, ate not strongly sorbed to soils. Sorption of chlotsulfuton and metsulfuron—methyl is inversely related to soil pH (407) and is positively correlated to soil organic matter (408). 

An extensive pesticide properties database was compiled, which includes six physical properties, ie, solubiUty, half-life, soil sorption, vapor pressure, acid pR and base pR for about 240 compounds (4). Because not all of the properties have been measured for all pesticides, some values had to be estimated. By early 1995, the Agricultural Research Service (ARS) had developed a computerized pesticide property database containing 17 physical properties for 330 pesticide compounds. The primary user of these data has been the USDA s Natural Resources Conservation Service (formerly the Soil Conservation Service) for leaching models to advise farmers on any combination of soil and pesticide properties that could potentially lead to substantial groundwater contamination. 

Kenaga EE. 1980. Predicted bioconcentration factors and soil sorption coefficients of pesticides and other chemicals. Ecotoxicol Environ Safety 4 26-38. 

Swann R, Laskowski D, McCAll P, et al. 1983. A rapid method for the estimation of the environmental parameters octanol/water partition coefficient, soil sorption constant, water to air ratio, and water solubility. Residue Rev 85 18-28. 

ECD Electron capture detection Ko, Kqc Soil sorption coefficients... 

Vapor pressure (VP), water solubility ( w), and soil sorption coefficients Koc) are key properties that govern volatilization of agrochemicals from soil. Volatile compounds such as 5 -ethyl dipropylthiocarbamate (EPTC) (VP 4.5 Pa,... 

Sabljia, A., On the prediction of soil sorption coefficients of organic pollutants from molecular structure application of molecular topology model, Environ. Sci. Technol., 21, 358-366, 1987. 

Soil Sorption Constant - Soil/Water (Knp.). The distribution of a chemical between soil and water can be described with an equilibrium expression that relates the amount of chemical sorbed to soil or sediment to the amount in the water at equilibrium. 

Kenaga, E. E. Goring, C.A.I. "Relationship Between Water Solubility, Soil Sorption, Octanol-Water Partioning, and Bioconcentration of Chemicals in Biota, ASTM, Third Aquatic Toxicology Symposium October 17-18, 1978. 

Lambert M (1968) Omega (Q) a useful index of soil sorption equilibria. J Agric Food Chem 15 340-343... 

Laird DA, Barriuso E, Dowdy RH, Koskinen WC (1992) Adsorption of atrazine on smectites. Soil Sci Soc Am J 56 62-67 Laird DA, Fleming PD (1999) Mechanisms for adsorption of organic bases on hydrated smectite surfaces. Environ Toxicol Chem 18 1668-1672 Lambert SM (1967) Functional relationship between sorption in soil and chemical structure. J Agric Food Chem 15 572-576 Lambert SM (1968) Omega, a useful index of soil sorption equilibria. J Agric Food Chem 16 340-343... 

Sabljic A (1989) Quantitative modeling of soil sorption for xenobiotic chemicals. Environ Health Persp 83 179-190... 

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

Kenaga, E. E., Goring, C. A. I. (1980) Relationship between water solubility, soil sorption, octanol-water partitioning, and concentration of chemicals in biota. In Aquatic Toxicology. ASTM STP 707, Eaton, J. G., Parrish, P. R., Hendrick, A. C., Eds., pp. 78-115, Am. Soc. for Testing and Materials, Philadelphia, PA. 

Meylan, W. M., Howard, P. H., Boethling, R. S. (1992) Molecular topology/fragment contribution for predicting soil sorption coefficient. Environ. Sci. Technol. 26, 1560-1567. 

Reddy, K. N., Locke, M. A. (1994) Relationships between molecular properties and log p and soil sorption (K(X ) of substituted phenylureas QSAR models. Chemosphere 28, 1929-1941. 

Sabljic, A. (1984) Predictions of the nature and strength of soil sorption of organic pollutants by molecular topology. J. Agric. Food Chem. 32, 243-246. 

Captina silt loam pH 4.97 McLaurin sandy loam pH 4.43, batch equilibrium, Walton et al. 1992) 1.75 (average of 5 soils, sorption isotherms by batch equilibrium method-GC, Xing et al. 1994)... 

Sabljic, A., Glisten, H., Verhaar, H., Hermens, J. (1995) QSAR modelling of soil sorption. Improvements and systematics of log vs. log KqW correlations. Chemosphere 31, 4489 -514. 

Sutton. C., Calder, J.A. (1975) Solubility of alkylbenzenes in distilled water and seawater at 25°C. J. Chem Eng. Data 20, 320-322. Swann, R.L., Laskowski, D.A., McCall, P.J., Vender Kuy, K., Dishburger, J.J. (1983) A rapid method for the estimation of the environmental parameters octanol/water partition coefficient, soil sorption constant, water to air ratio, and water solubility. Res. Rev. 85, 17-28. 

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