Soil cover

Adequate area soil cover and depth to groundwater usually greater than 1.5 m (4 ft). Slope should not exceed 5 to 8 percent. Soil type, including ion-exchange capacity. 

Fig. 3-31 Equipotential lines on the soil surface above a defect in the pipe coating (DN 700, thickness of soil covering 1.5 m).

In 1955 it was discovered that mixtures of ammonium nitrate and fine coal dust have satisfactory blasting capabilities in large (9 inch) holes used in open-pit coal mines to remove the rock and soil covering the coal. Polyethylene bags containing this material deform to fit the hole and provide moderate water resistance. ANFO is used in open-pit iron and copper mines and for construction such as road building. The mixture is air blown into 2-inch holes or less m maiiv underground mines. 

Where easily weathered lithologies such as carbonates and evaporites are near the surface, such as in the lower Amazon valley, their contribution to the rivers appears minor, probably because thick residual soil covers have devel-... 

Because of the water-holding properties of soils and the fact that most precipitation returns to the atmosphere via ET, it is possible to devise a landfill cover to meet remediation requirements, and yet contain no barrier layer. The ET cover consists of a layer of soil covered by native grasses it contains no barrier or impermeable layers. The ET cover uses two natural processes to control infiltration (1) soil provides a water reservoir and (2) natural evaporation from the soil plus plant transpiration (ET) empties the soil water reservoir.32-38 The ET cover is an inexpensive, practical, and easily maintained biological system that will remain effective during extended periods of time—perhaps centuries—at low cost. 

The soil should allow rapid and prolific root growth in all parts of the soil cover. 

The soil cover construction process is important because it has the power to assure success or cause poor performance of the cover. The ET cover uses a different mechanism to control water... 

The plant cover should have potential rooting depth greater than the thickness of the soil cover. Many native species have potential rooting depths of 2 m or more.14... 

Fayer, M.J. and Gee, G.W., Multiple-year water balance of soil covers in a semiarid setting, Journal of Environmental Quality, 35 (1), 366-377, 2006. 

The minimum thickness specification for an FML top liner covered with a layer of soil is 0.75 mm for an FML without a soil cover layer, the specification is 1.14 mm. An FML in a composite bottom liner system must be at least 0.75 mm thick. Even though these FML thicknesses meet U.S. EPA specifications, 0.75mm is not a suitable thickness for all FML materials. In fact, most FML materials installed at landfills are in the range of 1.50-2.50 mm in thickness. Other key factors affecting the selection of FML materials include chemical compatibility with waste leachate, aging and durability characteristics, stress and strain characteristics, ease of installation, and water vapor/ chemical permeation. 

Long-term exposure can be stopped using either soil or a nonwoven fabric to cover the membrane in a surface impoundment. Another option is to drape a heavy, nonwoven fabric with base anchors in it over the membrane. This nonwoven material is cheaper, safer, and more readily repaired than a soil cover. 

An example, when intercropping suppressed the weed growth more than sole, is a leek (Allium ampeloprasum var. porrum (L.) J.Gay) - celery (Apium graveo-lens L.) intercrop sown in a row-by-row layout decreased relative soil cover of weeds by 41%, reduced the density and biomass of groundsel (Senecio vulgaris L.) by 58% and 98%, respectively, and increased the total crop yield by 10% (Baumann et al. 2000). Increased weed suppression and the crop yield were also demonstrated in cereal-legume intercrops in many different environments (Ofori et al. 1987). 

Kovda, V. A. (1984). Biogeochemistry of Soil Cover. Nauka Publishing House, Moscow, 261 pp. 

The typical Munsell color chart for soils covers only those colors described as being yellow or red or some combination of the two. This is not to say that... 

Jacinthe PA, Lai R. Effects of soil cover and land-use on the relations flux-concentrations of trace gases. Soil Sci. 2004 169 243-259. 

Further biodegradation in water, sediment and soil covering degradation rate and identification of relevant degradants... 

If complete burial of slurry can be guaranteed then the return of grazing animals to injected pasture would be controlled more by the state of the sward rather than the potential pathogen content of the slurry. Andrews et al (16) and Dickson and Tribe (17) have confirmed that the soil cover over injected sludge is an effective barrier to infection and that numbers of organisms fall rapidly following injection. 

Roquin, C., Freyssinet, Ph., Novikoff, A., Tardy Y. 1991. Geochemistry of Termitaria and soils covering ferricrete. Application to gold exploration in Western Africa. European Network on tropical laterite and global Environment, EurolatQI, 133-137. 

Diffusion Experiment Results of the diffusion experiment are shown in Table VI. One or more cm of untreated soil covering 20 g of soil treated with 100 ppm c DDT was very effective in preventing toxic concentrations of DDT from diffusing into water for one year. If any DDT did diffuse through the soil into water, the concentration was not sufficiently high to affect the survival or reproduction of daphnids. A 60% reproductive impairment has been reported when daphnids were exposed to 100 ng/L DDT W. Therefore, on the basis of the daphnid bioassay, the concentration of DDT in water over the 1 cm of soil was at or below 100 ng/L. On the other hand, where untreated soil did not cover the DDT layer, daphnids never survived more than 7 days. This result is very similar to those from the microecosystem experiment. The 1-ml water samples indicated a total DDT concentration of 10 to 20 ppb. In addition, TLC analysis of treated soil extracts after one year showed the expected conversion of DDT to DDD, but only when covered by 1 or more cm of soil. For the uncovered soil, 87% of the radioactivity was DDT. Apparently, 1 cm of soil was sufficient to produce the anaerobic conditions known to be necessary for conversion of DDT to DDD (j 2). 

On the other hand, slgnlhcant differences (p < 0.05) were observed among the three organic cultivations, with the highest value observed in the plums grown on soil covered with trlfollum. (From hombardi-Boccia et ah, 2004)... 

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