Parent material and soils

The distribution of Al and a number of other elements in soil profiles across the W-E transect appears to be strongly dependant on climate gradients rather than significant changes in soil parent materials and soil age. This observation provides important information about the relative importance of a number of geochemical processes that are not revealed in studies at more detailed (local) scales. 

The background site must be of similar characteristics, that is, same topographical location, similar soil physical characteristics, similar water regimen, and similar parent material and soil forming process. 

The values ofBCw were determined on a basis of FAO soil nomenclature, soil parent material and soil texture according to UBA (1996) and values of Ci, and Q were applied to accounting biogeochemical cycling intensity and duration of active temperature period (see Chapter 7, Section 1). The root zone was assumed to be equal to 0.5m. 

There are a number of ways of classifying soil for crop prodnction. Soils have been grouped into soil associations. Each association consists of a nnmber of soil series each of which has distinct characteristics, both of parent material and soil profile. The soil series is usually named after the place where the soil was first described. The same soil series can occur in cfifterent regions. Soil characteristics, together with relief and climate and cropping potential, have also been used to classify land for farming (Appendix 7). 

Strong correlations occur between concentrations of trace elements in Californian soils. Nickel concentrations in soils are strongly correlated with Cr (r = 0.95) Cu contents are also significantly correlated with Co (r = 0.81). Strong correlations between Ni and Cr and between Cu and Co are observed as well (Marrett et al., 1992). This strong correlation between trace elements indicates that these elements associate in parent materials and suggests similar physical-chemical processes governing soil formation (Bradford et al., 1996). 

At the continental- to subcontinental-scale the relative proportions of major minerals in soils are largely controlled by parent material and climate factors. In turn, the distributions of many major and trace elements are strongly influenced by soil mineralogy, especially the presence or absence of quartz (Eberl Smith 2009 Bern 2009). 

Mineralogy and soil geochemistry along the W-E transect reflect both the influence of soil parent materials and effect of hemispheric climate gradients. The quartz dilution effect described by Bern (2009) dominates the distribution of a number of elements Al is given as an example in Figure 2. 

Wetlands occur on the valley floors and the lower slopes. The soils vary widely with parent materials and other factors, bnt there are some general patterns. On the valley floors, slopes decrease from the top to the bottom and the age and texture of the deposits vary accordingly. Where deposition is most active, the soils are yonng and have little profile development. These are Entisols. But most soils in the valley bottoms show at least some profile development and are Inceptisols or Alfisols where there is a prononnced dry season. 

Most of the products identified in these studies are considerably more biodegradable than the parent materials and should be degraded or bound more rapidly than the parent compounds in biologically active soils. 

Harradine, F., and Jenny, H. (1958). Influence of parent material and climate on texture and nitrogen and carbon contents of virgin California soils I. Texture and nitrogen contents of soils. Soil Sci. 85(5), 235-243. 

Climate Heat, rain, ice, snow, wind, sunshine, and other environmental forces break down the parent material and affect how fast or slow soil processes proceed. 

In nature this common set is typically further restricted over wide geographic areas because of the influence or otherwise of soil-forming factors, the most important of which are parent material and degree of weathering. Thus, a typical sample of soil will contain a suite of around six to ten different major minerals. A major mineral may be defined as one that is present at a concentration of a few percent or more, at which it will be readily detectable by routine techniques such as x-ray provider diffraction (XRPD). It is also known as energy-dispersive x-ray analysis (EDXA) or energy-dispersive analysis of x-ray (EDAX) or microscopic examination, either optical or electron. It is also not uncommon for several other minerals to be present in any given soil but usually in amounts that put them below the routine detection limits of many techniques. Nonetheless, these accessory, or trace, minerals can often be concentrated by some means that separates the soil sample into different physical or chemical fractions. Such procedures effectively lower... 

Cicchella et al. (2005, 2008b) demonstrated how the Pb concentrations in the volcanic soils of the city of Napoli, Italy, were derived from both the natural content of Pb from underlying parent materials and by the use of fuels containing Pb additives (Fig. 8.3). 

The result of these various processes is that the Earth s cmst, the parent material for soils, is dominated (in mass) by eight elements (oxygen, silicon, aluminum, iron, calcium, sodium, magnesium, and potassium). These elements, with the exception of oxygen, are not the dominant elements of the solar system. Thus, soils on Earth form in a matrix dominated by oxygen and silicon, the elements which form the backbone of the silicate minerals that dominate both the primary and secondary minerals found in soils. 

Soil production is a function of sod depth (Heimsath et al., 1997), parent material, and environmental conditions (Heimsath et al.,1999). As soil thickens, the rate of the conversion of the underlying rock or sediment to sod decreases. This has been shown using field observations of the relation between soil thickness and the abundance of cosmogenic nuclides ( °Be and A1) in the quartz grains at the rock-soil interface (Figure 24). From this work, soil production can be described by... 

A particularly valuable approach to investigating the effect of time on chemical weathering has been the use of soil chronosequences which are defined as a group of soils that differ in age and, therefore, in duration of weathering. These soils have similar parent materials and have formed under similar climatic and geomorphic conditions (Jenny, 1941). Individual soils, therefore, provide snapshots of the progressive nature of chemical weathering with time. 

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