Heavy metal/metalloid mobility

Adsorption to mineral surfaces such as Fe and Al (hydr)oxides has long been known to be an important process that limits the mobility of heavy metals and metalloid species in aqueous systems (e.g., Stumm 1992). The sorption of ionic species in MSWI bottom ash has been recently studied in detail by Meima Comans (1998, 1999). These authors used a sequence of selective chemical extractions to determine sorbent concentration, namely Fe and Al (hydr)oxides. Their model calculations suggested that Zn(II) and M0O4 sorbed to Fe (hydr)oxides, while Pb(II) and Cu(II) appeared to have a greater affinity for Fe (hydr)oxides. The sorption of Cd(Il) was found to be very weak. The interpretation of... 

The biohazard in soils attributable to heavy metals, and to metalloids such as arsenic, has often been assessed by determination of their total soil contents and national guidelines based on such total contents are currently in use (see for example, Appendices 3-6 in Alloway, 1995). Total soil contents, however, reflect the geological origins of soils as well as the anthropogenic inputs such as pollutants from industrial processes and are poor indicators of mobility or bioavailability. A more relevant assessment of the contents of elemental contamination can be made by measuring the pseudototal element contents of a soil by the... 

Microorganisms can transfer methyl groups to various heavy metals and metalloids (e.g., Se, As), which results in mobilizing these heavy metals and promoting their potentiation as environmental toxicants. Such methylation is attributed to the enzymatic system involved in the anaerobic generation of methane, where the methyl donor is methylcobal-amin (methyl vitamin B12). This is exemplified by the case of mercury (see Figure 9.12). 

Recently, we have carried out studies on the effect of LMMOAs on the adsorption of selected heavy metals and metalloids onto/from metal oxides, variable-charge soils, and organomineral complexes. The aim of this work is to present some of our significant findings on the effect of biomolecules, usually present in the rhizosphere, on the mobility of trace elements in soil environments. We also compare our results with those reported in the literature. 

In general, the electroremediation of heavy metals and metalloids in Table 4.1 are dependent mainly on the development of an acidic front through the soil since the acidification aids mobilization. In most of the experiments, the acidification had not reached through the whole soil specimen during the remediation period, and the remediation percentages given in the table were obtained only in a short distance from the anode. 

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