Metals in soil

Practical measurements providing data on corrosion risk or cathodic protection are predominantly electrical in nature. In principle they concern the determination of the three principal parameters of electrical technology voltage, current, and resistance. Also the measurement of the potential of metals in soil or in electrolytes is a high-resistance measurement of the voltage between the object and reference electrode and thus does not draw any current (see Table 3-1). 

The transition resistance between the surface of the metal and the electrolyte with uncoated iron anodes in coke backfill, the transition resistance is usually low. With metals in soil, it can be increased by films of grease, paint, rust or deposits. It contains in addition an electrochemical polarization resistance that depends on the current [see Eq. (2-35)]. 

Polarisation-curve procedures The Denison method is to measure the current at various degrees of polarisation of metal in soil in a special cell. While this test is considered quite accurate, it has the disadvantage that the measurements are made in the laboratory and cannot be made in the field. 

The factors influencing the corrosion of metals in soil are more numerous than those prevailing in air or water, and the electrochemical effects are more pronounced. Moreover, soils vary widely in their composition and behaviour even over very short distances. It is difficult therefore to obtain reliable data. It is evident, however, that zinc has considerable resistance to corrosion when buried, and the greatest attack is caused by soils which are acid or contain large amounts of soluble salts. 

Schuhmacher M, Granero S, Belles M, Llobet JM and Domingo JL (1996) Levels of metals in soils and vegetation in the vicinity of a municipal solid waste incinerator. Toxicol Environ Chem 56 119-132. 

Ecologically, copper is a trace element essential to many plants and animals. However, high levels of copper in soil can be directly toxic to certain soil microorganisms and can disrupt important microbial processes in soil, such as nitrogen and phosphorus cycling. Copper is typically found in the environment as a solid metal in soils and soil sediment in surface water. There is no evidence that biotransformation processes have a significant bearing on the fate and transport of copper in water. 

Baath, E., Effects of heavy metals in soil on microbial processes and populations (a review), Water, Air, SoilPollut, 47 (3), 335-379, 1989. 

Most primary and secondary minerals found in soil systems are barely soluble in the soil solution. The amount of mass from the bulk phase to hydrated ions in soil solution is negligible compared to the total mass of the solid phase. In arid and semi-arid soils, concentrations of most trace metals in soil solution may be controlled by their carbonates and to some extent by their hydroxides. Other than carbonates, trace elements in arid and semi-arid soils may also occur as sulfate, phosphate or siliceous compounds, or as a minor component adsorbed on the surface of various solid phase components. The solubility of carbonates, sulfates and other common minerals of trace elements in arid and semi-arid soils will be discussed in Chapter 5. Badawy et al. (2002) reported that in near neutral and alkaline soils representative of alluvial, desertic and calcareous soils of Egypt, the measured Pb2+ activities were undersaturated with regard to the solubility of... 

There are a number of selective sequential dissolution procedures which have been developed for specific elements, matrices, regional soils, and specific purposes (Table 4.1). Additionally, various extractants are used in different sequential procedures for the similar targeted solid-phase component. The review on the extractants of individual fractions of metals in soil was made by Shuman (1991). However, in most protocols the trace elements/heavy metals in their native and waste-amended soils are divided into the following physicochemical forms ... 

In summary, the removal of organic matter and Fe oxides significantly changes the physicochemical and surface chemical properties of soils. Thus, this pretreatment affects the overall reactivity of heavy metals in soils. The removal of organic matter and Fe oxides may either increase or decrease heavy metal adsorption. The mechanisms responsible for the changes in metal adsorption in soils with the removal of organic matter and Fe oxides include increases in pH, surface area, CEC and electrostatic attraction, decreases in the ZPC, shifts of positive zeta potentials toward... 

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)...

RESIDENCE TIME OF METALS IN SOIL SOLUTION OF METAL-CONTAMINATED ISRAELI ARID SOILS... 

Mining and industrial activities produce large quantities of volatiles and dust particles and increase concentrations of trace elements and heavy metals in soils, waters, and vegetation. When mineral deposits containing concentrated trace elements and heavy metals are exposed at the earth s... 

Chemical remediation refers to the application of various minerals or chemicals to adsorb, bind, precipitate or co-precipitate trace elements and heavy metals in soils and waters thereby reducing their bioavailability, toxicity, and mobility. In situ immobilization refers to the treatment of contaminants in place without having to excavate the soils or waste, often resulting in substantial cost savings. However, in situ immobilization or extraction by these physicochemical techniques can be expensive and are often only appropriate for small areas where rapid and complete decontamination is required. 

Beckett P.H.T. The use of extractants in studies on trace metals in soils, sewage sludges and sludge-treated soils. Adv Soil Sci 1989 9 143-176. 

Hamel S.C., Buckley B., Lioy P.J. Bioaccessibility of metals in soils for different liquid to solid ratios in synthetic gastric fluid. Environ Sci Technol 1998 32 358-362. 

Misra A., Sarkunan K. V., Das M., Nayar P.K. Transformation of added heavy metals in soils under flooded condition. J India Soc Soil Sci 1990 38 416-418. 

Renella G., Landi L., Nannipieri P. Degradation of low molecular weight organic acids complxed with heavy metals in soil. Geoderma 2004 122 311-315. 

Ross S.M. Toxic Metals in Soil-Plant Systems. Chichester, UK John Wiley Sons, 1994. 

Zeien H., Brummer G.W. Determination of the mobility and binding of heavy metals in soil by sequential extraction. Mitteilungen der deutschen bodenkundlichen gesellschaft. 1991 66 397-400. 

Bacteria and their composites with soil minerals or organic matter are capable of taking up a wide range and variety of toxic metals in soil environments. Research done over the last decade or so has greatly improved our understanding of the mechanisms on biosorption of metals and bacte-ria-metal-soil component interactions. However, more studies from molecular level are needed in order to enhance the ability of bacteria and their association with soil components to remediate toxic metals-contaminated soils. The focus of future investigations should be on the mechanisms by which metals are sorbed and bound by bacterial cell surfaces and bacteria-soil/mineral composites. In this connection, X-ray absorption spectroscopy (XAS) is a promising technique because it can provide information about... 

Alloway BJ (1995) Cadmium. In Alloway BJ (ed) Heavy metals in soils. Blackie Academic and Professional, Glasgow, pp 122-151... 

Doelman P, Jansen E, Michels M, Van-Til M (1994) Effects of heavy metals in soil on microbial diversity and activity as shown by the sensitivity-resistance index, an ecological relevant parameter. Biol Fertil Soils 17 177-184... 

Toxicity of six toxicants (Zn2+ > ethidium bromide > sodium pentachloro- 208 phenate > Cu2+ > 2,4-dichlorophenoxyacetic acid sodium dodecyl sulfate = no) on a recombinant Escherichia coli Toxicity of metals in soils amended with sewage sludge 209... 

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