Sorption, organic chemicals

A variety of mechanisms or forces can attract organic chemicals to a soil surface and retain them there. For a given chemical, or family of chemicals, several of these mechanisms may operate in the bonding of the chemical to the soil. For any given chemical, an increase in polarity, number of functional groups, and ionic nature of the chemical can increase the number of potential sorption mechanisms for the chemical. 

Although most nonionic organic chemicals are subject to low energy bonding mechanisms, sorption of phenyl- and other substituted-urea pesticides such as diuron to sod or sod components has been attributed to a variety of mechanisms, depending on the sorbent. The mechanisms include hydrophobic interactions, cation bridging, van der Waals forces, and charge-transfer complexes. 

Doucette, W.J. (2003) Quantitative Structure-Activity Relationships for Predicting SoU-Sediment Sorption Coefficients for Organic Chemicals. Environmental Toxicology and Chemistry, 22(8), 1771-1788. 

WASP/TOXIWASP/WASTOX. The Water Quality Analysis Simulation Program (WASP, 3)is a generalized finite-difference code designed to accept user-specified kinetic models as subroutines. It can be applied to one, two, and three-dimensional descriptions of water bodies, and process models can be structured to include linear and non-linear kinetics. Two versions of WASP designed specifically for synthetic organic chemicals exist at this time. TOXIWASP (54) was developed at the Athens Environmental Research Laboratory of U.S. E.P.A. WASTOX (55) was developed at HydroQual, with participation from the group responsible for WASP. Both codes include process models for hydrolysis, biolysis, oxidations, volatilization, and photolysis. Both treat sorption/desorption as local equilibria. These codes allow the user to specify either constant or time-variable transport and reaction processes. 

Alien-King R, Grathwohl P, Ball W (2002) New modeling paradigms for the sorption of hydrophobic organic chemicals to heterogeneous carbonaceous matter in soils, sediments, and rocks. Adv Water Resour 25 985-1016... 

Carrizosa MJ, Hermosin MC, Koskinen WC, Cornejo J (2004) Interactions of two sulfonylurea herbicides with organoclays. Clays Clay Miner 52 643-649 Celis R, Hermosin MC, Cornejo J (2000) Heavy metal adsorption by functionalized clays. Environ Sci Technol 34 4593-4599 Chappell MA, Laird DA, Thompson ML, Li H, Teppen BJ, Johnston CT, Boyd SA (2005) Influence of smectite hydration and swelling on atrazine sorption behavior. Environ. Sci Technol 39 3150-3156 Chiou CT (1989) Theoretical considerations of the partition uptake of nonionic organic compounds by soil organic matter. In Sawhney BL, Brown K (eds) Reactions and movement of organic chemicals in soils. Soil Science Society of America, Madison, WI, pp 1-29... 

Hassett JJ, Banwart WL (1989) The sorption of nonpolar organics by soils and sediments. In Sawhney BL, Brown K (eds) Reactions and movement of organic chemicals in soils. Soil Science Society of America, Madison, WI, pp 31-44... 

Another important factor influencing the bioavailability of organic contaminants is the contact time between the contaminant and soil/sorbent, often referred to as aging. Aging often increases the sorption of organic chemicals by allowing more time for the chemicals to partition deeper into... 

Bioavailability is also influenced by certain, albeit poorly understood, characteristics of bacteria. To degrade soil-sorbed molecules, bacteria must either use sorbed molecule directly or facilitate desorption in some manner. Mechanisms underlying the apparent availability of sorbed chemicals are complex due to the divergent properties of chemicals considered, the resultant sorption/desorption mechanisms, the metabolic diversity of microorganisms, and the heterogeneity of soils. Several microbial-based mechanisms have been proposed for the access of soil-sorbed organic chemicals (i) production of bio surfactants (Desai and Banat 1997 Alexander 1999) ... 

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

Perlinger, J.A., Eisenreich, S J., Capel, P.D. (1993) Apphcation of headspace analysis to the study of sorption of hydrophobic organic chemicals to a-Al203. Environ. Sci. Technol. 27, 928-937. 

Nkedi-Kizza, P, Rao, P.S.C., Hornsby, A.G. (1985) Influence of organic cosolvent on sorption of hydrophobic organic chemicals by soils. Environ. Sci. Technol. 19, 975-979. 

Stauffer, T.B., MacIntyre, W.G., Wickman, D.C. (1989) Sorption of nonpolar organic chemicals on low-carbon-content aquifer materials. Environ. Toxicol. Chem. 8, 845-852. 

Linn DM, Carski TH, Brusseau ML, Chang FH, eds. Sorption and Degradation of Pesticides and Organic Chemicals in Soil. Madison, WI Soil Science Society of America and American Agronomy Society of Agronomy 1993. 

Since sorption is primarily a surface phenomenon, its activity is a direct function of the surface area of the solid as well as the electrical forces active on that surface. Most organic chemicals are nonionic and therefore associate more readily with organic rather than with mineral particles in soils. Dispersed organic carbon found in soils has a very high surface-to-volume ratio. A small percentage of organic carbon can have a larger adsorptive capacity than the total of the mineral components. 

The net result of sorption on organic contaminated soils is to retard the movement of contaminants. When a pollutant is adsorbed onto soil, it can be released only when the equilibrium between it and the passing fluid (water or air) is disrupted. Retardation is the term used to describe the apparent discrepancy between the actual migration rate of aquifer water and that of a dissolved organic chemical (somewhat slower). The difference in travel rates is the result of sorption of the chemical onto the aquifer matrix and release into water by the concentration gradient and time of contact. A general equation used for gross estimation of the retardation factor Rj is... 

Several factors govern the transport and fate of hydrophobic organic chemicals in sediment/water environments microbially mediated reactions and sorption are major processes affecting the fate of these compounds in aquatic systems [166,366-368]. Aryl halides have been shown to undergo microbially-mediated dehalogenation under anaerobic conditions [38, 52, 68, 105, 116,... 

Brusseau, M.L., Jessup, R.E., and Rao, P.S.C. Sorption kinetics of organic chemicals evaluation of gas-purge and miscible-displacement techniques, Environ. Sci. Technol, 24(5) 727-735, 1990. 

Jepsen, R. and Lick, W. Nonlinear and interactive effects in the sorption of hydrophobic organic chemicals by sediments. Environ. Toxicol. Chem., 18(8) 1627-1636, 1999. 

Mader, B.T., Uwe-Goss, K., and Eisenreich, S.J. Sorption of nonionic, hydrophobic organic chemicals to mineral surfaces. 

Schrap, S.M., de Vries, P.J., and Opperhuizen, A. Experimental problems in determining sorption coefficients of organic chemicals an example of chlorobenzenes, Chemosphere, 28(5) 931-945, 1994. 

Schrap, S.M. and Opperhuizen, A. Relationship between bioavailability and hydrophobicity reduction of the uptake of organic chemicals by fish due to the sorption of particles. Environ. Toxicol. Chem., 9(6) 715-724,1990. 

Welke, B., Ettlinger, K., and Riederer, M. Sorption of volatile organic chemicals in plant surfaces. Environ. Sci. TechnoL, 32(8) 1099-1104,1998. 

Woodburn, K.B., Lee, L.S., Suresh, P., Rao, C., and Delfino, J J. Comparison of sorption energetics for hydrophobic organic chemicals by synthetic and natural sorbents from methanol/water solvent mixtures. Environ. Sci. Technol, 23(4) 407-413, 1989. 

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