Vegetative layer

The top layer in the landfill profile is the vegetative layer. In the short term, this layer prevents wind and water erosion, minimizes the percolation of surface water into the waste layer, and maximizes evapotranspiration, the loss of water from soil by evaporation and transpiration. The vegetative layer also functions in the long term to enhance aesthetics and to promote a self-sustaining ecosystem on top of the landfill. The latter is of primary importance because facilities may not be maintained for an indefinite period of time by either government or industry. 

For sites on very arid land or on steep slopes, an armoring system, or hardened cap, may be more effective than a vegetative layer for securing a landfill. Operators should not depend on an agricultural layer for protection in areas where vegetation cannot survive. Many States allow asphalt caps as an alternative to vegetative covers. Some closures at industrial sites have involved constructing... 

The homestead irrespective of ecologically distinct locations has a multilayered spatial arrangement of vegetation (Fig. 16.7). Vegetation layer varies from homestead to homestead, which may usually range from three to five (Yoshino 1996 Ahmed 1999 Bashar 1999 Basak 2002 Hussain and Miah 2004) and even up to... 

Within the canopy stands, the air motion is significantly decelerated, but nevertheless it is of a considerable value and evidently of vital importance for agrometeorolog-ical practice. The internal motion is expected to be less or more depended also on how dense is the vegetated layer. The most popular relation derived theoretically by Inoue... 

The problem in a vertical plane is formulated for a wide channel, ideally for an infinitely wide one, of a constant depth assuming that the flow pattern is approximately the same in each vertical plane along the flow direction, as it has been depicted in Fig. 1.5. A usual vertical velocity distribution that follows formula (1.1) takes place only above the vegetation submerged in the water flow. This distribution becomes complex and uncommon within the vegetation layer where a significant motion of the water still takes place. A number of experimental data given in [69, 172, 347, 370, 617] confirms... 

No approaches were known however for the velocity distribution within the vegetated layer. Bennovitsky stated that formulas (1.3) may be approximately applied. So both kinds of hydraulic problems turned out to be similar to the forest canopy problem. 

The SM2-U model (Dupont and Mestayer, 2004 [158] Dupont et al., 2005 [160]) is based on the force-restore model of Noilhan and Planton 1989 [469] for the transfers between the atmosphere, one vegetation layer, and three soil layers in its most recent version, ISBA-3L (Boone et al., 1999 [66]). It keeps the principal characteristics of this soil model and was developed as a pre-processor for fine resolution sub-mesoscale simulations. The surface dynamic influence is represented through roughness lengths... 

Shimizu, Y and Tsujimoto, T. (1994) Numerical analysis of turbulent open-channel flow over a vegetation layer using a k-e turbulence model, J. Hydroscience and Hydraulic Engineering, 11(2), 57-67. 

Soil provides a habitat for many yeasts either permanently or as a temporary home to escape desiccation. Desiccation is often prevented by the secretion of extracellular slime by the yeasts. Poor soil, such as seashore sand, may contain few yeasts but rich agricultural soils often have as many as 40 000 viable yeasts per gram of soil. Leaves and other plant material, particularly rotting fruit, are also rich sources of yeasts. From the vegetative layer above the soil surface, yeasts are blown by air currents. The dominant yeasts encountered in one survey of urban New Zealand air were species of Crypto-coccus, Rhodotorula, Sporobolomyces and Debaryomyces, On average there was one viable yeast cell per 0 56 m (per 2 ft ). A wide range of yeasts has also been identified in samples taken in marine areas, including species of Candida, Cryptococcus Rhodotorula and Debaryomyces,... 

Fig. 4. Integrated vault technology for low level waste disposal where A represents waste containers that are placed in concrete overpacks and sealed with grout B, closed modules covered with a multiple-layer earthen cover, to direct water away from modules, and short rooted vegetation for erosion control and C, overpacks placed in reinforced concrete modules which are closed with a reinforced concrete roof Courtesy of Chem-Nuclear Systems, Inc.

Sulphates, silicates, carbonates, colloids and certain organic compounds act as inhibitors if evenly distributed, and sodium silicate has been used as such in certain media. Nitrates tend to promote corrosion, especially in acid soil waters, due to cathodic de-polarisation and to the formation of soluble nitrates. Alkaline soils can cause serious corrosion with the formation of alkali plumbites which decompose to give (red) lead monoxide. Organic acids and carbon dioxide from rotting vegetable matter or manure also have a strong corrosive action. This is probably the explanation of phenol corrosion , which is not caused by phenol, but thought to be caused by decomposition of jute or hessian in applied protective layers. ... 

Fruit juices, meat products, milk and milk products, fish and most vegetables, in which tin is likely to be anodic to steel, can be handled open to the air in tinned steel vessels. Some corrosion of the tin occurs at rates similar to those found for pure tin and in due course retinning may be necessary. The alloy layer in hot-dipped tin coatings is cathodic to both tin and steel and, under aerated conditions may stimulate the corrosion of both metals, but this effect appears to be unimportant in practice. 

Coal, a black mineral of vegetable origin, is believed to have come from the accumulation of decaying plant material in swamps during prehistoric eras when warm, wet climatic conditions permitted rapid growth of plants. The cycles of decay, new growth, and decay, caused successive layers of plant material to form and gradually build up into vast deposits. The accumulation of top layers of this material and of sedimentary... 

The structure of vegetation also has an influence on surface roughness and on local wind patterns and rates of mixing in the boundary layer of the atmosphere. Forests have a dampening affect on wind, slowing it and causing increased... 

Mohnen, D., Eberhard, S., Marfi, V., Doubrava, N., Toubart, P., Gollin, D.J., Gruber, T.A., Nuri, W., Albersheim, P., and Darvill, A. (1990) The control of root, vegetative shoot and flower morphogenesis in tobacco thin cell-layer explants (TCLs). Development, 108 191-201. 

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