Organic matter-clay interactions

The water-rock/soil and organic matter-minerals (including soil organic matter-clay), interactions can also be studied by infrared spectroscopy (Chapter 2, Section 2.1.2). 

EFFECTS OF ORGANIC MATTER-CLAY INTERACTIONS IN SOILS... 

Birkel, U., Gerold, G., and Niemeyer, J. (2002). Abiotic reactions of organics on clay mineral surfaces. In Soil Mineral-Organic Matter-Microorganism Interactions and Ecosystem Health Dynamics, Mobility and Transformation of Pollutants and Nutrients. Violante, A., Huang, P. M., Bollag, J.-M. and Gianfreda, L., eds., Elsevier Science B.V., Amsterdam,The Netherlands, pp. 437 447. 

In contrast to humic acids, proteins constitute a class of compounds that are chemically well defined, prevalent in soils, and able to form complexes with clay surfaces. Therefore, in order to study the interactions of anthropogenic chemicals with organic matter/clay complexes, we have started a series of MD simulations dealing with the adsorption of proteins by phyllosilicate surfaces. These investigations can be extended to humic acid coated clays, because many of the functional groups in proteins are the same as those in humic acids. 

Interactions Between Organophosphorus Compounds and Soil Materials I. Adsorption of Ethyl-methylphosphonofluoridate by Clay and Organic Matter Preparations and by Soils," M. H. B. Hayes, P. R. Lundie and M. Stacey, Pestic. Sci., 3 (1972) 619-629. 

A. S. Boyd and M. M. Mortland, Enzyme interactions with clays and clay-organic matter complexes. Soil Biochemistry, Vol. 6 (J.-M. Bollag and G. Stotzky, eds.), Marcel Dekker, New York, 1990, p. I. 

Carbonates, organic matter, Fe and Mn oxides, and clay minerals play important roles in controlling overall reactivity of trace elements in soils and sediments. This chapter addresses the interaction of trace elements with carbonates, organic matter, Fe and Mn oxides and clay minerals. Analytical techniques for trace element speciation in solid-phase and their distribution among various solid-phase components in arid and semi-arid soils are reviewed. Solubilities of trace elements in solid phases and their mineralogical characteristics in arid and semi-arid soils also are discussed. 

Oades JM, Gillman GP, Uehara G (1989) Interactions of soil organic matter and variable-charge clays. In Coleman DC, Oades JM, Uehara, G (eds) Dynamics of soil organic matter in tropical ecosystems. Nif TAL Project. University of Hawaii, Honolulu, USA, pp 69-95... 

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... 

The solid portion of soil is composed of inorganic sand, silt, clay, and organic matter (OM), which interact to produce the large soil features1 (i.e., peds, profiles, pedons, and landscapes). These features, not considering rock, are discussed in this chapter. In Chapter 3, components smaller than rock, which soil scientists define as those inorganic particles smaller than 2.00 mm in... 

As noted in Chapter 2, sand, silt, clay, and organic matter do not act independently of each other in soil. Thus, one or several types of chemical bonds or interactions—ionic, polar covalent, covalent, hydrogen, polar-polar interactions, and van der Waals interactions—will be important in holding soil components together. The whole area of chemical bonding is extremely complex, and thus, in addition to specific bonding considerations, there are also more... 

At the boundary between uplands and wetlands there is, in some circumstances, an interaction between organic matter accumulation in sediments and the development of wetland conditions. Some level of organic matter accumulation is required to drive anaerobic metabolism. But also, because, in general, well-decomposed organic matter improves the water holding capacity of mineral soils, particularly in medium to coarse texmred sediments, and particularly if the clay mineralogy is dominated by low activity kaolinitic clays, there is a feedback between organic matter accumulation and the extent and duration of water saturation. 

Bollag JM, LoU Ml (1983) Incorporation of xenobiotics in soil humus. Experentia 39 1221-1225 Bollag JM, Myers CJ, Minard RD (1992) Biological and chemical interactions of pesticides with soil organic matter. Sci Total Environ 123/124 205-217 Bolt GH (1955) Ion adsorption by clays. Soil Sd 79 267-278... 

Sorption coefficients quantitatively describe the extent to which an organic chemical is distributed at equilibrium between an environmental solid (i.e., soil, sediment, suspended sediment, wastewater solids) and the aqueous phase it is in contact with. Sorption coefficients depend on (1) the variety of interactions occurring between the solute and the solid and aqueous phases and (2) the effects of environmental and/or experimental variables such as organic matter quantity and type, clay mineral content and type, clay to organic matter ratio, particle size distribution and surface area of the sorbent, pH, ionic strength, suspended particulates or colloidal material, temperature, dissolved organic matter (DOM) concentration, solute and solid concentrations, and phase separation technique. 

Figure 3.6. Modes of interaction of natural organic matter with a clay mineral surface. The figure depicts cation (M) and water bridging, along with van der Waals interactions (through the sugar moiety). Reprinted with permission from Stevenson, F. J., and Ardakani, M. S. (1972). Organic matter reactions involving micronutrients in soils. In Micronutrients in Agriculture, Mortvedt, J. J., Giordano, P. M., and Lindsay, W. L., eds., Soil Science Society of America, Madison, WI, pp. 79-114.

Acidic pesticides such as 2,4-D, 2,4,5-T, picloram, and dinoseb can ionize in aqueous solutions forming anionic species (Saltzman and Yaron, 1986). Sorption of these pesticides on soils has also been correlated with soil organic matter content (Hamaker et al., 1966), and in their anionic form they can be sorbed on soils, clays, and amorphous materials at low pH. The mechanisms of sorption for these compounds are proton association and, for the molecular form, van der Waals sorption (Saltzman and Yaron, 1986). Hydrogen bonding and electrostatic interactions are other possible mechanisms for sorption. 

Normally, because of the small size of soil particles and the presence of small capillaries and pores in the soil, the water phase is not totally independent of soil solid matter. Water present in larger spaces in soil is relatively more available to plants and readily drains away. Water held in smaller pores or between the unit layers of clay particles is held much more firmly. Water in soil interacts strongly with organic matter and clay minerals. 

---