Arid areas/environments

High arsenic concentrations can develop in groundwaters as As(V) is released from oxide minerals and clays at high pH. High pH conditions frequently develop in arid areas as a result of extensive mineral weathering with proton uptake. This is especially true in environments dominated... 

Salinity in dryland environment is a natural phenomenon derived from a long-term accumulation of salts on the ground and a lack of adequate flushing in the unsaturated zone. Salt accumulation and efflorescent crusts have been documented in the upper unsaturated zone (e.g., Gee and Hillel, 1988 Nativ et al., 1997 Leaney et al., 2003) and in fracture surfaces (Weisbrod et al., 2000) in many arid areas. The salt formation has been attributed to surface evaporation (Allison and Barnes, 1985), wetting and drying cycles (Drever and Smith, 1978), soil capillarity, and capillarity transport of water and salts from the bulk rock matrix towards fracture surfaces (Weisbrod et al., 2000). 

Stanton J., Olson D. K., Brook J. H., and Gordon R. S. (2001) The environmental and economic feasibility of alternative crops in arid areas considering mesquite in Baja Cahfornia, Mexico. J. Arid Environ. 48, 9-22. 

The physical environment in which people live affects their lives in many ways. In colder regions, for example, adequate clothing and shelter is essential to survive the elements. In arid areas, the availability of water is a critical consideration. The physical environment can provide or lack important mineral, water, or other resources. Different environments make different demands and require different responses from society. Archaeologists investigate the environmental context of ancient societies in detail. 

The term acid rain is commonly used to describe phenomena associated with both wet and dry deposition. The effects of man-made airborne substances on indoor surfaces are expected to be different from and less dramatic than those on outdoor surfaces. In the outdoor environment, both the species contained in the rain or fog droplets and the added influence of substances previously deposited on the surfaces by dry deposition will impact the surfaces. For very brief rain events, the surface concentrations of many species are likely to be substantial, due to the combined effects of accumulated dry deposition and the high concentrations of species that have been commonly associated with the early stages of a rain event. The available data indicate that roughly 70 percent of the total deposition is dry deposition. Hansen and Hidy (2), in their assessment of existing rain chemistry data, discuss the influence of geographical factors on pH and state that in western arid areas of the United States, soil-derived substances elevate the pH in the early stages of a rain event, while in the northeastern... 

In hot arid areas where the continental shelf meets the land, marine sabkha-type environments exist. For example, on theTrucial coast ofAbu Dhabi shallow marine carbonate sediments are reworked and bound by microbial mats. In the upper intertidal zone these mats... 

Loess is a special kind of wind-blown deposit under arid-semiarid environment in Quaternary period. Its physical and mechanical properties are related to the forming environment. The stratum and physical properties are general identical under a definite environment, therefore the study for a particular case can provide reference in the area of same deposit unit. 

Many inland lakes in arid areas possess high dissolved salt concentrations, e.g. the Dead Sea contains 32 per cent dissolved salts. The high osmotic pressure of such environments limits the availability of water to any organism present and the number of species able to survive such conditions is low. This is also the basis of the preservation of foods, by salting or sugar syrups. 

In arid environments, where the soluble products of weathering are not completely removed from the soil, saline solutions may circulate in the soil as well as in rock fractures. If upon evaporation the salt concentration increases above its saturation point, salt crystals form and grow (Goudie et al, 1970). The growth of salt crystals in crevices can force open fractures. Salt weathering occurs in cold or hot deserts or areas where salts accumulate. Boulders, blocks. 

Movement of carbonates and salts can also occur in a similar fashion. As these minerals are weathered in the upper soil profile, their component ions go into solution and are moved down through the soil by rainfall entering the soil. As the water moves down the soil there may not be enough water to move the ions out of the soil, so they precipitate in a lower horizon where they accumulate. Such accumulations are common in arid environments with limited rainfall. In high rainfall areas, carbonates and salts are usually completely removed from the soil through leaching. 

On die other hand, the measure of the afforestation is also classified into no-regrettable one from the viewpoint of environment. Furthermore, most of desert area is said to be formed by partly somewhat human activities. The activities of afforestation of arid land without crop production are also a no-regrettable measure [14-17]. 

Nicolas J, Chiari M, Crespo J, Orellana IG, Lucarelli F, Nava S, Pastor C, Yubero E (2008) Quantification of Saharan and local dust impact in an arid Mediterranean area by the positive matrix factorization (PMF) technique. Atmos Environ 42(39) 8872-8882... 

Atrazine is the key herbicide facilitating ecofallow corn and sorghum production in the semi-arid Great Plains, where crop production is often uncertain and profits to farmers are often marginal. The success of atrazine in ecofallow is attributable to its duration of weed control as a soil-applied herbicide, the broad spectrum of weeds controlled, the low cost per area treated, and its safety to crops. In this semi-arid environment, maintaining weed-free fallow with repeated applications of nonresidual herbicides is not an economically viable alternative to atrazine. 

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