problem for the characterization of soil pollution from an environmental point
of view.
The first approach to assessing pollution is to determine the total concentration of
metals; the assessment of their bioavailability is necessary to have proper knowledge
of risk assessment. Soil parameters that influence the mobility of HMs are the redox
potential, pH, and cation exchange capacity.
These parameters determine the solubility and the adsorption capacity of soils.
Soil is characterized by the concentration in HMs (which depends on the type of soil
and its composition) and soil contamination with these metals provided by human
activity. Pb has a pronounced tendency to accumulate in soil due to minimal mobility
even at low pH values.
In the phosphate-containing soil, Pb forms hardly soluble lead phosphate deposits
(Pb 3 (PO 4 ) 2 , Pb 4 O(PO 4 ) 2 , and Pb 5 (PO 4 ) 3 OH). In carbonate-containing soils, lead
carbonate is formed (PbCO 3 ). Under lead conditions, lead sulfide (PbS) is formed.
High levels of Pb pollution are reported in the vicinity of industrial areas and waste
incinerators, where dust particles are removed.
Because plants are more resistant to Pb than humans, it is important to avoid
contamination of food from areas that are too polluted with Pb. Concentrations of Cd
depend on the geological origin of soil material, its texture, the intensity of degradation processes, OM, and other factors. The accumulation of Cd in the soil is partly
due to industrial activities and can be explained by the composition and geological
origin of the rock material. Cd enters the soil in smaller amounts than Pb and can
reach the soil through the air. It can come from incineration gases and phosphatebased fertilizers. In acidic soils with pH <6, Cd is very mobile and does not
accumulate. Cd compounds with humic acids are somewhat stable. In a reducing
medium and in the presence of the sulfate ion, CdS is formed. Cu is more mobile
than Cd and its solubility increases to pH <5. Although Cu counts among the trace
elements necessary for life, in the case of plants, 20 mg/kg of dry material produces
toxic effects. Cu ions are toxic to MOs at concentrations of about 0.1 mg/L. Zn is one
of the most mobile metals in the soil. The solubility of Zn in soil increases especially
at pH <6. At higher pH and in the presence of phosphates, Zn allotted to plants can
be significantly reduced. The pH-dependent process of adsorption on clay and
various oxides is the most significant regulating process for the availability of Zn
in soils. Concerning the environmental risk and the trophic chain caused by Zn
remains an open question because Zn deficiency in diet can be a problem.
Furthermore, it seems that Zn has a role in controlling Cd fixation in soils
contaminated with Cd when the Zn:Cd ratio is greater than 100. It has been deduced
that neural networks can be considered as a tool for predicting spatial analysis of
processes controlling the transfer metals with the soil–plant system. Neural calculation can support decision-making processes at different levels, to improve harvest
management based on monitoring data and to assess the risk of soil metal transfer to
plants (Pratush et al. 2018).
4 Advanced Technologies for Ecological Reconstruction and Bioremediation of. . .
93
of view.
The first approach to assessing pollution is to determine the total concentration of
metals; the assessment of their bioavailability is necessary to have proper knowledge
of risk assessment. Soil parameters that influence the mobility of HMs are the redox
potential, pH, and cation exchange capacity.
These parameters determine the solubility and the adsorption capacity of soils.
Soil is characterized by the concentration in HMs (which depends on the type of soil
and its composition) and soil contamination with these metals provided by human
activity. Pb has a pronounced tendency to accumulate in soil due to minimal mobility
even at low pH values.
In the phosphate-containing soil, Pb forms hardly soluble lead phosphate deposits
(Pb 3 (PO 4 ) 2 , Pb 4 O(PO 4 ) 2 , and Pb 5 (PO 4 ) 3 OH). In carbonate-containing soils, lead
carbonate is formed (PbCO 3 ). Under lead conditions, lead sulfide (PbS) is formed.
High levels of Pb pollution are reported in the vicinity of industrial areas and waste
incinerators, where dust particles are removed.
Because plants are more resistant to Pb than humans, it is important to avoid
contamination of food from areas that are too polluted with Pb. Concentrations of Cd
depend on the geological origin of soil material, its texture, the intensity of degradation processes, OM, and other factors. The accumulation of Cd in the soil is partly
due to industrial activities and can be explained by the composition and geological
origin of the rock material. Cd enters the soil in smaller amounts than Pb and can
reach the soil through the air. It can come from incineration gases and phosphatebased fertilizers. In acidic soils with pH <6, Cd is very mobile and does not
accumulate. Cd compounds with humic acids are somewhat stable. In a reducing
medium and in the presence of the sulfate ion, CdS is formed. Cu is more mobile
than Cd and its solubility increases to pH <5. Although Cu counts among the trace
elements necessary for life, in the case of plants, 20 mg/kg of dry material produces
toxic effects. Cu ions are toxic to MOs at concentrations of about 0.1 mg/L. Zn is one
of the most mobile metals in the soil. The solubility of Zn in soil increases especially
at pH <6. At higher pH and in the presence of phosphates, Zn allotted to plants can
be significantly reduced. The pH-dependent process of adsorption on clay and
various oxides is the most significant regulating process for the availability of Zn
in soils. Concerning the environmental risk and the trophic chain caused by Zn
remains an open question because Zn deficiency in diet can be a problem.
Furthermore, it seems that Zn has a role in controlling Cd fixation in soils
contaminated with Cd when the Zn:Cd ratio is greater than 100. It has been deduced
that neural networks can be considered as a tool for predicting spatial analysis of
processes controlling the transfer metals with the soil–plant system. Neural calculation can support decision-making processes at different levels, to improve harvest
management based on monitoring data and to assess the risk of soil metal transfer to
plants (Pratush et al. 2018).
4 Advanced Technologies for Ecological Reconstruction and Bioremediation of. . .
93