Natural soils

Possible negative environmental effects of fertilizer use are the subject of iatensive evaluation and much discussion. The foUowiag negative effects of fertilizer usage have been variously suggested (113) a deterioration of food quaUty the destmction of natural soil fertility the promotion of gastroiatestiaal cancer the pollution of ground and surface water and contributions toward the destmction of the ozone layer ia the stratosphere. 

These problems can be dealt with by usiag artificial test cloths impregnated with various approximations of natural soils such as vacuum cleaner dust, dirt from air conditioner filters, clays, carbon black, fatty acids, dirty motor oil, and artificial sebum, either alone or ia combination (37,94—98). The soils are appHed by sprayiag, immersion, or padding. If the soils are carefully appHed, reproducible results can be obtained. Soil test cloths can be of great help ia detergency studies, when used with an understanding of their limitations. 

D. B. Knaebel, T. W. Federle, D. C. McAvoy, and J. R. Vestal, Effect of mineral and organic soil constituents on microbial mineralisation of organic compttunds in a natural soil. Applied and Environmental Microbiology 60 4500 (1994). 

Embankment and fill applications are the biggest end-user of spent foundry sand. Natural soils are often composed primarily of sand, clay, and water. Most spent foundry sands have these same constituents, which suggests spent foundry sand as a good fill material. The immediate benefits include saving virgin soil materials and reduce the bottom line of the foundry industry. It is also reported that foundry sand as a fill material may present better performance then conventional materials, including better resistance to freeze-thaw distress. 

For compacted, low-permeability soil liners, the U.S. EPA draft guidance recommends natural soil materials, such as clays and silts. However, soils amended or blended with different additives (e.g., lime, cement, bentonite clays, and borrow clays) may also meet the current selection criteria of low hydraulic conductivity, or permeability, and sufficient thickness to prevent hazardous constituent migration out of the landfill unit. Therefore, U.S. EPA does not exclude compacted soil liners that contain these amendments. Additional factors affecting the design and construction of CCLs include plasticity index (PI), Atterburg limits, grain sizes, clay mineralogy, and attenuation properties. 

It is possible to make soils more resistant to chemical attack. Many of the same methods used to lower hydraulic conductivity can stabilize materials against leachate attack, including greater compaction, an increase in overburden stress, and the mixing of additives such as lime cement or sodium silicate with the natural soil materials.25... 

Area fraction fresh water in continental system (excl. sea) Area fraction natural soil in continental system (excl. sea) Area fraction agricultural soil in continental system (excl. sea) Area fraction urban/industrial soil in continental system (excl. sea)... 

Area fraction natural soil in continental system (total)... 

Organic matter is also the essential component of natural soils and its association with microorganisms may influence the behavior and fate of toxic metals. A variety of batch complexation experiments were performed by Borrok et al. (2007) in single, binary and ternary systems for the three components natural organic matter (NOM), bacterium (B. subtilis) and metals (Pb, Cu, Cd, and Ni) to determine the significance of ternary complexation. They found that the formation of bacteria-metal-NOM complex is a rapid, fully-reversible chemical process. The stability of bacteria-metal-NOM complexes increases with the decrease of pH. All NOM fractions form ternary complexes to similar extents at circumneutral pH, but humic acid becomes the dominant NOM fraction in ternary complexes at low pH. The abundance of humic acid in ternary form is greatest with Ni or Cd systems and less with Pb and Cu systems. Their results suggest that... 

Rippen, G., Ilgenstein, M., Klopffer, W., Poreniski, H.J. (1982) Screening of the adsorption behavior of new chemicals natural soils and model adsorbents. Ecotox. Environ. Saf. 6, 236-245. 

In order to assess natural soil geochemical background concentrations, samples were collected from various soil horizons and discrete depth intervals from hand-dug pits. A total of 72 sites were sampled during the 2007 and 2008 field seasons yielding an average density of approximately 1 site per 800 km2 that is double the nominal density of a site per 1600 km2 for the NASGLP. Samples were collected from the surface layer (0 to 5... 

Phenolic acids can be allelopathic but their presence in soil is ephemeral due to rapid degradation and/or sorption by soil particles (Inderjit 2004). Sorption of benzoic acid onto soil particles increased with concentration and it may explain the reason for the limited allelopathic effect of benzoic acid at concentrations often recorded in natural soil (Inderjit 2004). Microorganisms help to generate allelochemicals, but they may also modify toxic compounds into nontoxic compounds (Khanh et al. 2005). Allelochemicals are changed in composition and quantity during the residue decomposition. Allelopathy plays an important function in nutrient recycling (Rice 1984). 

Two basic concepts are used in developing the naming of different soils. First is the idea that a soil s characteristics will determine which group it falls into and its name. Another idea is that soils will be related to a reference soil. In both cases, the natural soil horizons are used in the soil description. In Soil Taxonomy, horizons used for naming the soil are called diagnostic horizons. In the reference soils, the horizons are called reference horizons. The general concepts are similar in all systems, and so are many names for soil characteristics. The names are often descriptive in that they give an idea of the characteristic of the soil. 

A more recent study of the effect of drying on various species of phosphate in soil showed that drying had little effect on some species while having a pronounced effect on others [13]. In nature, soil is never heated to the temperatures used in oven drying, and thus the results of analysis of oven-dried soils are not considered representative of the soils natural conditions. 

Contamination of soil often leads to a situation where the contaminants are not only in the soil but are also in the soil air. These can be analyzed using the same or similar methodologies that are used to analyze natural soil air constituents. 

The suitability of the ELISA for soil analysis was initially tested by assaying a number of control soil samples, fortified after extraction and neutralisation with Paraquat in the range 10-300mg kgy1. The results in Table 9.19 were close to the expected values and thus confirmed that natural soil components did not interfere with the determination. These results justified the further refinement of the method for soil analysis. 

Table 4.6 Octanol-water Coefficients and Partition Coefficients of Organic Substances on Natural Soil Materials (Modified from Schwarzenbach et al., 1983)...

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