Potentially toxic metals soils

Many lakes in northeastern North America and Scandinavia have become so acidic that fish are no longer able to live in them. The low pH not only directly affects fish but also contributes to the release of potentially toxic metals, such as aluminum, from the soil. The maximum effect occurs when there is little buffering of the acid by soils or rock components. Maximum fish kills occur in early spring due to the acid shock ... 

Chemical Speciation to Assess Potentially Toxic Metals (PTMs ) Bioavailability and Geochemical Forms in Polluted Soils... 

Figure 9 1 The major forms of potentially toxic metals (PTMs) in soil.

Figure 9.2 Potentially toxic metals (PTMs ) pools of different mobility, target organisms and routes of transfer in and from the soil.

Table 9.1 Amounts of some potentially toxic metals (PTMs) measured in the soil matrix (mg- kg a) and soil solution (ug L a) obtained by various techniques from uncontaminated and contaminated soils... 

Figure 9 3 Major plant and soil factors affecting plant-available potentially toxic metals ...

Table 9.4 Examples of potentially toxic metals (PTMs ) bioaccessibility values (% of soil total content in mg-kg ) in contaminated soils determined with different in vitro digestion models... 

Figure 9.8 Potentially toxic metals (PTMs ) distribution in the BCR sequentially extracted fractions from the Bagnoli industrial ex-ILVA soil (0-72-cm depth). (HOAc = acetic acid-extractable red = reducible oxi = oxidisable res = residual) (from Adamo et al., 2002a).

Figure 9.9 Thin-section micrograph (PPL) of a pore in the 72-80-cm depth horizon from Bagnoli soil completely covered by dark clay coatings and potentially toxic metals (PTMs j quantification (mg kg ) in the coatings as determined by the wavelength dispersive spectroscopy (WDS) (average of 40 points around the pore) (from Adamo et al., 2002a).

Weis, 2004). If the rhizosphere plays an important role in the sequestration of metals in wetland soils, fluxes of potentially toxic metals out of the wetland to adjacent aquatic systems will, in theory, be reduced. However, plants may also increase metal mobilization through rhizosphere acidification and the oxidation of metal-sulfide complexes (Jacob and Otte, 2003). They may also represent only a temporary sink for metals if rhizosphere Fe plaque is reduced following plant senescence. Furthermore, metals can be exported from the ecosystem if contaminated plant parts are consumed by people or wildlife. The pathways and possible health effects of metal consumption have been especially well studied in Southeast Asia, where metal contamination (notably As) of rice crops is a serious public health issue (e.g., Meharg and Rahman, 2003 Meharg, 2004). 

This paper [353] also appears to be based on the assumption that as long as phytotoxic symptoms and reduction in yield in crops are avoided, it does not really matter how much metal-contaminated sludge is applied to agricultural soils. On the basis of this view and rather dubious assumptions about the relationship between zinc equivalent and phytotoxic potential, carte blanche has been given in England in recent years for the application of sludges to agricultural land, with little reference to their contents of potentially toxic metals other than zinc, copper and nickel. Since the maximum proposed application is 50 tons dry matter/acre/annum and this would be equivalent to... 

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)...

Han F.X., Banin A. Long-term transformations and redistribution of potentially toxic heavy metals in arid-zone soils. I Incubation under saturated conditions. Water Air Soil Pollut 1997 95 399 123. 

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