Binding to Soils

In the preceding chapters, we revisited the interaction of ions with soil components, mainly minerals, and humic substances. As it should be apparent, there are a high number of studies on sorption of ions to soil components, and in many aspects, it is a field fairly well known. All these are laboratory studies, under well-controlled conditions. Now, the question arising is. How do we apply all these results to a natural soil, where the components are interacting between themselves, and the conditions are changing due to climate, human, and animal activity There is no easy answer to this question, and in fact, nowadays, we are rather far away from satisfactory results in this respect. In this chapter, we will try to reflect the state-of-the-art response to this problem. 

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Owing to its low water solubility and high octanol/water partition coefficients, dinitroaniline herbicides adsorb and bind to soil macromolecules and show minimal leaching potential. Dinitroanilines herbicides show good soil residue activities with soil half-lives ranging from 30 days for benfluralin and oryzalin to 6-7 months for trifluralin. Al-Dealkylation (aerobic conditions) and reduction of the nitro group to an amino moiety (anaerobic conditions) have been reported as major soil degradation pathways. 

University of Wisconsin, Madison, Determining the soil conditions where lead Wl binds to soils... 

Less is known about what happens to thiocyanates when they enter the environment. In soil and water, thiocyanates are changed into other chemical forms by microorganisms. At near normal temperatures (30 °C), evaporation or sorption (binding to soil) does not seem to be important for thiocyanates in soil. 

Because 1,4-dichlorobenzene does not dissolve easily in water, the small amounts that enter bodies of water quickly evaporate into the air. If it is released to groundwater, it may be transported to surface water. Depending on conditions, some 1,4-di chlorobenzene may bind to soil and sediment. 1,4-Dichlorobenzene in soil is not usually easily broken down by soil organisms. There is evidence that plants and fish absorb 1,4-di chlorobenzene. It has been detected at concentrations up to 400 ppb in fish. 

Hexanone, also known as methyl n-butyl ketone or MBK, is a clear, colorless liquid with a somewhat sharp odor. The liquid form can easily evaporate into the air as a vapor. It is a waste product of wood pulping, coal gasification, and oil shale operations. 2-Hexanone was formerly used in paint and paint thinner and in various chemical substances. However, since it was found to have harmful health effects, it is no longer made in the United States, and its uses have been restricted. There are no known major natural sources of 2-hexanone in the environment. When 2-hexanone is released to rivers or lakes, it dissolves very easily, and it may evaporate into the air in a few days. We do not know if 2-hexanone binds to soil. When 2-hexanone is released to the water, air, or soil, it is probably broken down into smaller products, possibly within a few days. 

Literature data regarding the fate and transport of hexachlorobutadiene are limited. Much of the available information consists of modeling based on the physical and chemical properties of hexachlorobutadiene, and the monitoring data. These data indicate that hexachlorobutadiene will bind to soil particles and sediments, and is found in air and water bound to particulates. Some volatilization of hexachlorobutadiene from surface waters and soils may also occur. The bioconcentration of hexachlorobutadiene has been reported in fish and shellfish with considerable variability between species (EPA 1976 Oliver and Niimi 1983 Pearson and McConnell 1975). 

Most analytical methods for nickel in environmental samples do not distinguish between compounds of nickel or the nature of its binding to soil and particulate matter. It is generally impossible to say with certainty what forms of nickel are released from natural and anthropogenic sources, what forms are deposited or occur in environmental samples, and to what forms of nickel people are exposed. The form... 

Polycyclic aromatic hydrocarbons represent a class of compounds of great environmental concern due to their suspected mutagenic and carcinogenic properties [42-47]. Unease over the potential adverse health effects of polycyclic aromatic hydrocarbons is evident in the recent inclusion of P6 polyaromatic hydrocarbons in the Environmental Protection Agency s priority contaminates list. Polycyclic aromatic hydrocarbon contaminates pose several potential health risks due to the persistence of these compounds in the environment [48,49], their tendency to strongly bind to soil surfaces [50-52], and their presence in a wide variety of common media (air, dust, soil and food) [53]. Possible risks are associated with skin contact, inhalation or ingestion of contaminated dust, soil, or air, and ingestion of contaminated food. 

There is a need to resume studies of soil saccharides and peptides. These can compose as much as 30-40% (when account is taken of the compositions of humin materials). Much is known about how polysaccharides of known structures interact with soil colloids, but it has not been possible as yet to know in sufficient detail the structures of the polysaccharides that persist in the soil. Hence we do not know the mechanisms of their binding to soil mineral colloids. The same applies for the peptide materials, though it is clear that polysaccharides and peptides have important roles in soil structure formation and stabilization. 

Chemical stabilization of SOM occurs as a result of chemical or physico-chemical binding to soil mineral surfaces (Polubesova et al., 2008). Reversible sorption of labile substrates decreases their concentration in the soil solution and slows... 

Pirimicarb has been widely used in agriculture as a systemic aphicide. Unlike many carbamates, it is rather persistent, with a strong tendency to bind to soil. 

Metals constitute an important source of pollution in soils. As discussed in Chapters 5 and 6, they can bind to soils through humic substances, surface complex-ation, or ion exchange. In some cases more than one type of interaction can occur, as in clay minerals (e.g., montmorillonite and vermiculite) that bind metals through ion exchange as well as surface com-... 

Gustafsson, J. P. Pechova, P. Berggren, D. Modeling Metal Binding to Soils The Role of Natural Organic Matter, Environ. Sci. Technol. 2003, 37, 2767-2774. 

M MgCb or CH3COONH4, pH 7 For metal ions binding to soil by ionic interactions 10 mM Tris-HCl, pH 7.4 For peptides from the vacuole and cytosol... 

HCN is lighter than air and has a long half-life in air. However, in open spaces, HCN is rapidly dispersed and is diluted to nontoxie concentrations. Cyanide does not bind to soil or plant material, but can mix with water. Contaminated water can be treated with ozone, hydrogen peroxide, or ealeium/sodium hypochlorite bleach. Rescue personnel should wear boots, gloves, goggles, Ml protective clothes, and a self-contained positive pressure breathing apparatus as the potential for secondary contamination is high (AAR, 2000). 

Released BP is moderately persistent in the environment. It readily binds to soils and should not leach to groundwater, though it has been detected in some groundwater. If released into water, it will adsorb strongly to sediments and particulate matter. In most waters and sediments it will resist breakdown by microbes and reactive chemicals. BP is expected to bioconcentrate in aquatic organisms that cannot metabolize it, including plankton, oysters, and some fish. 

Coumarin is readily biodegradable. Coumarin is unlikely to bind to soil. Coumarin does not bioaccumulate the bioconcentration factor has been determined to be <10-40. Various environmental fate studies have shown that coumarin in the environment would biodegrade and be lost to volatilization. Losses resulting from photolysis may also occur. 

The predominant form of methylamine under environmental conditions is the ionized (protonated) species, which is expected to bind to soil constituents, suspended sediments, and bed sediments to a greater degree than the neutral form. As such, migration from soil to groundwater is expected to be less than would be anticipated for the neutral form. Volatilization from moist soils or surface water is not expected to be an important fate process. Biodegradation is expected to be an important loss process in both soil and water. The potential for bioconcentration in aquatic biota is low. 

In terrestrial systems, octachlorostyrene is expected to bind to soil particles. In the atmosphere, octachlorostyrene (in the vapor phase) is degraded by reactions with photochemically produced hydroxyl radicals. Octachlorostyrene weakly absorbs ultraviolet light between 295 and 310 nm with slow photolysis. Major transformation products of photolysis include heptachlorostyrene and two isomers of hexa-chlorostyrene, while minor transformation products of photolysis include pentachlorostyrene and tetra-chlorostyrene. 

In soil, o-toluidine will be eliminated by biodegradation, oxidation, and binding to soil components. In water, toluidine will be eliminated by biodegradation, oxidation, and photooxidation as well as some adsorption to sediment. In the atmosphere, toluidine will photodegrade (half-life about 2 h). 

Reduction to amino funtional groups enhances binding to soil organic matter... 

Hydrazines can also dissolve in water or bind to soil. The extent to which these processes occur depends on soil and water conditions. Hydrazines can move with water through soil as it flows underground. This is particularly true in sandy soils. In water and soil, some microorganisms (tiny plants or animals) can break down hydrazines to form less toxic compounds. Most of the hydrazines in soil and water are gone within a few weeks. 

Tandlich, R. (2004). Microbial PCB degradation and binding to soil components. PhD thesis, North Dakota State University, Fargo, ND, USA. 

Johnson CJ, Pedersen JA, Chappell RJ et al (2007) Oral transmissibility of prion disease is enhanced by binding to soil particles. PLoS Pathog 3 e93... 

Organic chemicals are often much more soluble in organic solvents and fats than in water and are said to be lipophilic. The BCF and also to a great extent the binding to soil are dependent on the lipophilic nature of the compound. In principle, this is simple to measure experimentally by shaking a small amount of the substance in a separating funnel with n-octanol and water. The two solvents separate into two phases, and the substance distributes between them. The distribution constant at equilibrium (KOW) is defined as... 

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