Semiarid region

Jojoba. Jojoba oil [61789-91-1] is obtained from the seeds of the jojoba plant grown in semiarid regions of Costa Rica, Israel, Mexico, and the United States. The oil is made up of ca 80 wt % of esters of eicos-ll-enoic and docos-13-enoic acids, and eicos-ll- -l-ol, and docos-13- -l-ol, ca 17 wt % of other hquid esters, with the balance being free alcohols, free acids, and steroids. Jojoba oil is used primarily in the formulation of cosmetics. Hydrogenated jojoba oil is a wax used in candles and other low volume specialty apphcations. 

Evaporation. Evaporation of the water held in the pit is often the first step in reserve pit remediation, due to economic considerations over trucking and disposal. The evaporation may be mechanically driven or take place naturally. Natural evaporation is very effective in the semiarid regions. The Meyer Equation 4-385 as derived from Dalton s law may be used to estimate the local natural evaporation [224]. These are. 

Nutrient Inputs from Urban Wastewaters and Global Change in Semiarid Regions... 

Inputs of organic matter and nutrients, benthic metabolism, and nutrient retention at each stream section depend on diffuse and point sources. Yet, under low flow conditions, water and matter transport downstream becomes impeded or discontinued due to stream contraction and fragmentation during dry periods. Therefore, nutrient export from rivers in semiarid regions will depend, more so than in more humid regions, on the interplay between the spatial configuration of organic matter... 

C12-0101. Brackish water, with a salt content around 0.5% by mass, is found in semiarid regions such as the American southwest. Assuming that brackish water contains only sodium chloride and that the ions form no ion pairs, estimate the osmotic pressure of brackish water at 298 K. 

Penrose WR, Polzer WL, Essington EH, et al. 1990. Mobility of plutonium and americium through a shallow aquifer in a semiarid region. Environ Sci Technol 24(2) 228-234. 

Nyhan, J.W., A seven-year water balance study of an evapotranspiration landfill cover varying in slope for semiarid regions, Vadose Zone Journal, 4, 466-480, 2005. 

Martmez-Cob A, Tejero-Juste M (2004) A wind-based qualitative calibration of the Hargreaves ETO estimation equation in semiarid regions. Agric Water Manage 64 251-264... 

Dry deposition can also be a very important mechanism for removing pollutants from the atmosphere in the absence of precipitation. Indeed, even in such places as eastern England, the ratio of dry to wet removal of S02 has been estimated to be 2 1 (Davies and Mitchell, 1983). If this is the case, then in arid and semiarid regions such as much of the western United States dry deposition is clearly important. 

The reduction of soil moisture by weeds is critical in arid and semiarid regions and elsewhere at times when moisture is inadequate. Water use by weeds decreases its availability for crops, making production more costly. In mature... 

Since practically all nitrates are soluble in water, one would not expect to find extensive deposits of these salts in nature excepting in arid or semiarid regions. In addition to the nitrate deposits in Chile, limited quantities of potassium nitrate occur in East Asia. Most of the potassium nitrate used at the present time is made by the metatheti-cal reaction between sodium nitrate and potassium chloride,... 

In the arid Tropics, potential evaporation is higher than rainfall and net water movement is thus directed upwards. The water carries soluble compounds, such as carbonates, gypsum, or haloids to the topsoil or soil surface, where they accumulate and often cause salinity. This process occurs naturally in lower parts of arid areas and forms the landscape there. Human agricultural activities have resulted in additional salinity, which has become one of the most serious land use constraints in arid and semiarid regions (Qadir et al. 2000). 

Fig. 2.15 Many escarpments and mountain slopes have no springs, especially in semiarid regions. This shows that in such regions the vertical downflow paths of the local recharge water are relatively deep, meeting a lateral base flow zone that is situated deeper than the base of the escarpment.

Rivers and shallow groundwater are often saline in arid or semiarid regions. Examples are common in northeastern Brazil in crystalline rocks, remote from the sea, and in regions where no marine transgression has occurred for 100 million years. Hence, evaporation was for a long time... 

There are a number of allelochemicals among the mono-, sesqui-, and diterpenoids. In particular, plants in arid and semiarid regions produce diverse volatile terpenoids with allelopathic activity.5 Among the volatile monoterpenes, 1,8-cineole (4) and camphor (5) exhibit strong growth inhibitory effects on plants and are considered to be involved in plant competition. 1,4-Cineole (6), a minor isomer of 1,8-cineole, is a potent inhibitor of asparagine synthetase.6 -Menthane-3,8-diols (fir 7 and frw .r8), -menth-2-en-l-ols (cis 9 and trans 10), thymol (11), carvacrol (12), 1,8-cineole, cr-pinene (13), and /3-pinene (14) were isolated as allelopathic monoterpenes from Eucalyptus species.7 Eucalyptus trees also produce allelopathic sesquiterpenes including spathulenol (15), and a-, (3-, and 7-eudesmols (16-18).7... 

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