Soils soil aeration

Other important soil properties of the ET landfill cover may be controlled by adequate design and good construction practices. The properties that govern root and plant growth and are important to design of ET landfill covers include soil density, aeration, pH, and nutrients. For a complete list of soil properties refer to Table 25.2. 

The S.A.V.E. (soil aeration-vapor extraction) technology combines air stripping, vacuum extraction, and combustion technologies for the remediation of soil, groundwater, and... 

Based on the successful laboratory soil microcosm experiment, the most heavily contaminated soil was excavated from the surface (2 m) layerand treated ex situ. The soil was placed in an enclosed rectangular bed and its moisture content maintained at 15% (w/w). The soil was aerated with an agricultural spading machine. Surfactant, organic nutrients, and inorganic nutrients were applied to maintain an optimum C N P ratio (data not presented). The isolated microorganisms were inoculated into the soil as dilute suspensions on five separate occasions. 

In particular, soil color should be determined on dry and moist samples using Munsell Soil Color Charts (1994). Soil color is usually the first property recorded in a morphological description of soils (and may be the only feature of significance to a layperson) and provides an indicator of redox status because soil color relates to soil aeration and organic matter content (Fitzpatrick, McKenzie, and Maschmedt 1999). Soil color has been found to be extremely useful in forensic soil identification by Sugita and Marumo (1996). 

The presence of salinity in soil and water can affect plant growth in three ways (1) it can increase the osmotic potential and hence decrease water availability (2) it can induce specific-ion effects by increasing the concentration of ions with an inhibitory effect on biological metabolism and (3) it can diminish soil-water permeability and soil aeration by adversely affecting soil structure. The adverse effects of soil salinity on plant growth and productivity varies with the type of plant being grown. 

Whereas diffusion of gas at depth is widespread, mass flow is often localised (near the ground surface, in faults) or intermittent (volcanic emptions). Mass flow is an important consideration in the application of gas geochemistry to mineral because of its significant role in the interchange of atmospheric air and soil air, and therefore its influence on gas composition in the shallow subsurface from where most samples and measurements are taken. Lovell (1979) reviewed soil aeration in this context. 

Source of soil aeration Percentage of total air exchange... 

Tackett, J.L., 1968. Theory application of gas chromatography in soil aeration research. Proc. Soil Sci. Soc. Am., 32 346-50. 

Sheppard, S. C., Sheppard, M. L, and Evenden, W. G. (1990). A novel method used to examine variation in Tc sorption among 34 soils, aerated and anoxic. J. Environ. Qual. 11, 215-233. 

The opportunity for co-precipitation and solid solution formation is higher with Fe and Mn oxides than A1 oxides or aluminosilicates. The reason for this is the higher solubility of the former two minerals under anaerobic conditions (see Chapter 7). Soil reduction generates the soluble ions, Fe and Mn, which then reoxidize to again form the insoluble oxides once the soil is aerated. The possibihty exists for co-precipitation of trace metals during these cycles of alternating reduction and oxidation. Furthermore, the fresh precipitates may also be effective adsorbates for trace metals. 

The oxidation of small sulfide particles is rapid once soils are aerated, so that acidification is immediate and extreme when anaerobic sulfide-bearing soils are drained. Long-term low-level acidification may occur in soils containing large sulfide particles (perhaps pyrites inherited from the parent material). Measurement of the oxidative dissolution of pyrite and other sulfides has produced the following rate law ... 

This result shows that, even in acid soil solutions, the equilibrium activity of Fe would be far below detectable levels if the soil is aerated. Furthermore, as is easily shown by equation 7.51, traces of dissolved oxygen in solution would be sufficient to keep the Fe concentration well below detection. That these predictions are not borne out in soils may suggest, as for the Mn case, that equilibrium is not usually attained with O2 in soil solution and that soluble organics may reduce Fe even when O2 is present. Alternatively, reduced zones may exist in aerated soils because of slow O2 diffusion into micropores, or the O2—H2O half-reaction may not be the appropriate one to express the oxidative potential of O2 (see discussion in section 7.2a). 

Qualitative evaluation of water table aqnifers vulnerability we have conducted considering the depths to water-table from land snrface and thickness of poorly permeable soils in aeration zone. According to this method following types of soils have been distinguished in the cross-section of aeration zone ... 

Table 1 presents numerical scores assigned to depth to water table and to poorly permeable soils in aeration zone based on their thickness. 

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