Mobility in soils

Cumene is expected to exist almost entirely in the vapor phase in the atmosphere (13). In water, mixed cultures of microorganisms collected from various locations and depths in the Atiantic Ocean were all found to be capable of degrading cumene (14). A number of studies have examined the aerobic degradation of cumene in seawater and in groundwater (15,16). The results indicate that cumene would normally be naturally degraded to below detectable limits within a week to ten days. Cumene is tightly adsorbed by soil and is not significantly mobile in soil (17). 

Environmental Fate. A portion of releases to land and water will quickly evaporate, although some degradation by microorganisms will occur. Xylene are moderately mobile in soils and may leach into groundwater, where they may persist for many years. Xylenes are VOCs. As such, xylene will react with other atmospheric components, contributing to the formation of ground-level ozone and other air pollutants. 

The relative immobility of the chlorodioxins is expected, based on the very low solubility of these compounds in water (0.6 / g/liter). In contrast, the herbicide, 2,4,5-T, is relatively mobile in sandy soils, but movement decreases as soil organic matter increases. What does this information tell us, and how does it compare with other organic compounds A mobility scale has been devised for a large number of pesticides (3). Higher mobility numbers reflect increased compound mobility in soils. The dioxins would be in Class 1—i.e., they are immobile in soils and would compare with several chlorinated hydrocarbon insecticides. 

Most of the trichloroethylene used in the United States is released into the atmosphere by evaporation primarily from degreasing operations. Once in the atmosphere, the dominant trichloroethylene degradation process is reaction with hydroxyl radicals the estimated half-life for this process is approximately 7 days. This relatively short half-life indicates that trichloroethylene is not a persistent atmospheric compound. Most trichloroethylene deposited in surface waters or on soil surfaces volatilizes into the atmosphere, although its high mobility in soil may result in substantial percolation to subsurface regions before volatilization can occur. In these subsurface environments, trichloroethylene is only slowly degraded and may be relatively persistent. 

In soil, the chances that any enzyme will retain its activity are very slim indeed, because inactivation can occur by denaturation, microbial degradation, and sorption (61,62), although it is possible that sorption may protect an enzyme from microbial degradation or chemical hydrolysis and retain its activity. The nature of most enzymes, particularly size and charge characteristics, is such that they would have very low mobility in soils, so that if a secreted enzyme is to have any effect, it must operate close to the point of secretion and its substrate must be able to diffuse to the enzyme. Secretory acid phosphatase was found to be produced in response to P-deficiency stress by epidermal cells of the main tap roots of white lupin and in the cell walls and intercellular spaces of lateral roots (63). Such apoplastic phosphatase is safe from soil but can be effective only when presented with soluble organophosphates, which are often present in the soil. solution (64). However, because the phosphatase activity in the rhizo-sphere originates from a number of sources (65), mostly microbial, and is much higher in the rhizosphere than in bulk soil (66), it seems curious that plants would have a need to secrete phosphatase at all. 

The polar character of neonicotinoids makes them, in general, potentially mobile in soil. Acetamiprid and nitenpyram have short soil persistence. Imidacloprid and thi-amethoxam, however, are sufficiently persistent in soil to be used for soil treatment. The definition of soil residues for the various neonicotinoid compounds except for imidacloprid are the parent compound and it metabolites. The metabolites of acetamiprid are lM-1-2, lM-1-4 and lC-0 (Figure 6). The metabolites of nitenpyram are 2-[N-(6-chloro-3-pyridyl-methyl)-A-ethyl]amino-2-methyliminoacetic acid (CPMA) and A-(6-chloro-3-pyridylmethyl)-Ai-ethyl-A -methylformamidine] (CPMF). 

Acids, alkalines, other corrosives many are highly mobile in soil. 

Soil pH affects the transformation of Cr between Cr(III) and Cr(VI) in soils. Since Cr(VI) has greater bioavailability and mobility in soils than Cr(III), which is strongly bound by soil solid matrix (Han and Banin, 1997). Cr(III) can be oxidized by soil manganese oxides into Cr(VI), while Cr(VI) can be reduced by organic matter, Fe(II) and microorganisms in soils. Reduction of Cr(VI) has been found to occur much slower in alkaline soils compared to acid soils (Cary et al., 1997). 

Mullins, C.L., Martens D.C., Miller W.P., Komegay E.T., Hallock D.L. Copper availability, form and mobility in soils from three annual copper-enriched hog manure applications. J Environ Quail982 11 316-320. 

Dao, T.H. 1977. Factors Affecting Atrazine Adsorption, Degradation, and Mobility in Soil. Ph.D. Thesis. University of Nebraska, Lincoln, NE. 68 pp. 

Smith, E.A. and C.I. Mayfield. 1978. Paraquat determination, degradation, and mobility in soil. Water Air Soil Pollut. 9 439-452. 

Based on calculated soil adsorption factors (log Koc of 2.24, 2.98, and 4.3), hexachloroethane is expected to have medium to low mobility in soil (Howard 1989). Thus, leaching to groundwater could occur. Results of studies with low organic carbon (0.02%) soil material indicate that sorption to aquifer materials retards hexachloroethane migration in groundwater (Curtis et al. 1986). In aquatic environments, moderate to slight adsorption to suspended solids and partitioning to sediments is likely (Howard 1989). 

There are also natural geochemical anomalies where soils are enriched by cadmium, for example, in the central parts of Sweden. Here the cultivation of crops accumulating cadmium (grains, potato, some grasses) is not recommended. In the coastal marine areas the cadmium mobility in soils is stimulated by its complexation with chlorine. 

Phosphorus oxyanions are entirely different from nitrogen oxyanions. First, the oxyanion species present is controlled by the pH also, phosphate oxyanions are generally not mobile in soil. However, sandy soils and soils high in phosphorus are exceptions to this rule. Any soil, though, can lose phosphate by erosion and this phosphate can cause environmental problems. Because of its unique chemistry, phosphorus will be discussed separately later. 

Sulfur oxyanions are similar to nitrate and nitrite in that they are mobile in soil and can be converted to many different forms (see Chapter 4, Figure 4.8). However, they are different from the other oxyanions in that they are the source of the essential nutrient, sulfur, and are deposited on soil from the atmosphere. Sulfate species can be determined by X-ray fluoresence (XRF), making their determination easier than the other oxyanions [21,22], Sulfur is discussed in more detail in Section 6.2.23. 

Both nitrite and nitrate are highly mobile in soil and easy to extract. However, it is also possible to reduce each individually to ammonia, steam-distill the ammonia, capture it, and titrate it as described earlier for ammonia. If this... 

No studies on the environmental transport and partitioning of endrin aldehyde could be found in the available literature. Values of the estimated log Kow for endrin aldehyde vary widely, ranging from 3.1 to 5.6 (see Table 3-2). Based on the lowest estimated log Kow, the Koc value for endrin aldehyde can be estimated to be approximately 1,000 (Lyman 1990), indicating a low mobility in soil (Swann et al. 1983). Using the higher estimated values of log Kow (4.7-5.6), the K00 value for endrin aldehyde can be estimated to range from 8,500 to 380,000 (Lyman 1990), indicating that this compound will be virtually immobile in most soils (Swann et al. 1983). Because of its low vapor pressure of... 

Other examples of nonionic compounds (Fig. 10, Table 3) are the phenyl-amide herbicides (e. g., Diphenamid, moderately water soluble and nonvolatile), thiocarbamate, and carbothioate herbicides (e. g., Thiobencarb, low water solubility, high vapor pressure, relative mobility in soil systems) and benzonitrile herbicides (e.g., Dichlobenil, low water solubility, low vapor pressure, relative immobility in most soils) [151]. 

Another method (EPA 3611) that focuses on the to separation of groups or fractions with similar mobility in soils is based on the use of alumina and silica gel (EPA 3630) that are used to fractionate the hydrocarbon into ahphatic and aromatic fractions. A gas chromatograph equipped with a boiling-point column (nonpolar capillary column) is used to analyze whole soil samples as weU as the aliphatic and aromatic fractions to resolve and quantify the fate-and-transport fractions. The method is versatile and performance based and therefore can be modified to accommodate data quality objectives. 

Businelli, D. Pig slurry amendment and herbicide coapplication effects on s-triazine mobility in soil an adsorption-desorption... 

Helling, C.S. Pesticide mobility in soils 11. Applications of soil thin-layer chromatography, SoilSci. Soc. Am. Proc., 35 737 -743, 1971. 

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