Aridity index

One expression of the combined influence of both precipitation and temperature is the de Martonne aridity index based on the formula... 

Where the aridity index (Ia) is equal to the mean annual precipitation in mm (Pmm) divided by the mean annual temperature in °C plus 10. According to this index, values below 5 characterize true deserts, values of approximately 10 define dry steppes, values of about 20 represent prairies, and values above 30 typify forest. 

Thus, the Martonne aridity index defines not only climatic parameters but also vegetational ones. Seasonality of precipitation is another climatic factor that affects desert and steppe boundaries. For a given mean annual temperature, the boundary of a steppe will extend into wetter climates if its precipitation falls mainly in the summer. This is because summer evapotranspiration depletes soil moisture more thoroughly than winter evapotranspiration. For similar reasons, the size of a desert will be larger if its precipitation falls in the summer rather than in the winter (Monger et al., 2004). 

An aridity definition that takes account of the relation precipitation/potential evaporation is the Aridity Index used in the Atlas of Desertification (UNEP, 1993). Four different degrees of aridity can be recognized. These are best defined using the Aridity Index (AI), calculated as the ratio P/PET, where P stands for precipitation and PET for (potential) evapotranspiration. AI values of <1.0 indicate an average annual moisture deficit. According to this criterion, four subzones can be discussed ... 

Levin NE, Cerling TE, Passey BH, Harris JM, Ehleringer JR (2006) A stable isotope aridity index for terrestrial... 

Fairchild et al. (2000), who showed that it was enhanced during the dry season at Clamouse cave in southern France. The associated high Mg/Ca and Sr/Ca ratios have been used to develop an aridity index (McMillan et al., 2005). Seasonally increased degassing occurs when drip rates are slow and the aquifer contains more gas spaces. Second, the pC02 of cave air can be seasonally lowered as described in section 7.2.4. 

SipOoifir gravity Optical roialici r, rtelraciivr index Arid value... 

Calcium—In general, calcium (as CaCOs) below 800 ppm should not result in calcium sulfate scale. In arid climates, however, the critical level may be much lower. For calcium carbonate scaling tendencies, calculate the Langelier Saturation Index or the Ryznar Stability Index. 

The partition index (IR, which will be discussed in details below) of Cd, Cu, Cr, Ni and Zn in both soils rapidly increased from time zero (calculated value) to one day and further to one year. This was especially true for Cr, Cu and to some extent Ni and Cd (Table 6.5). This result indicates that added trace metals are initially and rapidly transferred from the labile EXC fraction into the more stable fractions. Furthermore, IR of trace metals in native arid soils incubated under the saturated paste regime decreased at the end of year. This indicates mobilization of trace elements in these soils as saturation (Table 6.5). Also, it can be seen that IR decreased, for any given time, with an increase of the loading level (Table 6.5, Fig. 6.5). This means that higher additions of soluble metals result in higher metal content in the labile fractions and lower metal binding intensity in soils. 

Table 6.5. Reduced partition index (IR) of trace metals in arid-zone soils incubated under saturated paste regime (after Han and Banin, 1997. Reprinted from Water Air Soil Pollut, 95, Han F.X., Banin A., Long-term transformations and redistribution of potentially toxic heavy metals in arid-zone soils. I Incubation under saturated conditions, p 411, Copyright (1997), with permission from Springer Science and Business Media)...

Two parameters, the redistribution index (Uts) and the reduced partitioning parameter (IR), are used to describe the redistribution processes of trace elements in contaminated arid soils (Figs. 6.5-6.6) (Han et al., 2003a). The redistribution index depicts the removal or attainment of element-contaminated soils from or to the fractional distribution pattern characteristic of non-amended soils. However, the reduced partitioning parameter quantifies the relative binding intensity of trace elements in soils. 

Figure 6.5. The initial reduced partition index, Ir, of six metals in two Israeli arid soils. Two soils were treated with metal nitrates at various loading levels. Soils were incubated under the field capacity moisture regime (modified after Han and Banin, 1999, with permission from Springer Science and Business Media)...

The reduced partitioning index (mean IR values) of Cd, Cr, Cu, Ni and Zn in 45 Israeli arid-zone soils is presented in Fig. 6.7. The trends for mean IR values for five heavy metals in these soils were as follows Cr > Zn = Cu > Ni > Cd (Fig. 6.7) (IR is calculated from Banin et al., 1997a). This indicates that Cr is strongly bound to solid-phase components, possessing... 

Figure 6.7. Ranges (arithmetic mean and standard deviation) of the reduced partition index (IR) of Cd, Cu, Cr, Ni and Zn in 45 Israeli arid-zone soils (after Han et al., 2003a. Reprinted from Adv Environ Res, 8, Han F.X., Banin A., Kingery W.L., Triplett G.B., Zhou L.X., Zheng S.J., Ding W.X., New approach to studies of redistribution of heavy metals in soils, p 118, Copyright (2003), with permission from Elsevier)...

The fractional loading isotherms of Cr in a contaminated Israeli loessial soil at an initial (one hour) period and after 48 weeks. The fractional loading isotherms of Ni in a contaminated Israeli loessial soil at an initial (one hour) period and after 48 weeks. The fractional loading isotherms of Zn in a contaminated Israeli loessial soil at an initial (one hour) period and after 48 weeks. The initial reduced partition index, IR of six metals in two Israeli arid soils. Two soils were treated with metal nitrates at various loading levels. Soils were incubated under the field capacity moisture regime (modified after Han and Banin, 1999, with permission from Springer Science and Business Media). 

The cryoscopic index is always determined on fresh milk, as it is influenced by the aridity of the milk, by heating it and by the addition of preservative or saccharine substances. 

Figure 22 Predicted pattern of Holocene pedogenic carbonate accumulation in a cm column in a semi-arid, thermic climate (leaching index = 3.5 cm). External carbonate flux rate = 1.5 X 10 g cm yr PcOj = 1-5 X 10 atm in compartment 1 increasing to 10 atm in compartment 5 (20-25 cm). Below compartment 5, the pco decreases to a minimum value of 10 atm in compartment 20 (95-100 cm). Dotted line shows carbonate distribution at r = 0. Gray area indicates final simulated distribution. Depth = absolute infiltration depth in <2 mm fraction (McFadden et al, 1991) (reproduced by permission of Soil Science Society of America from Occurrence, Characteristics, and Genesis of Carbonate, Gypsum and Silica Accumulations in...

Hydrologists have adopted the concept of a water stress index" based on an approximate minimum level of water required per capita to maintain an adequate quality of life in a moderately developed country in an arid zone. Although the indicators are only approjimate, it has been found that a country or region whose renewable fresh water availability exceeds about 1700-2000 m per person per year will suffer only occasional or local water problems. Below this threshold the lack of water begins to become a serious problem. Two rough benchmark levels have been adopted ... 

Features Imparts adhesion to metals arid wide variety ot plastic substrates good chem. resist., flexibility stable rheology Properties Gardner 3.5 clear liq. sp.gr. 1.0763 vise. 6220 cps acid no. 4.8 ref. index 1.4666 CN902J75 [Sartomer]... 

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