sterols (e.g., dihydrocholesterol, cholesterol and coprostanol), flame retardants (e.g.,
polybrominated diethyl ethers, bisphenol-A and hexabromocyclododecanes),
nitrosamines (e.g., nitrose dimethylamine, nitrose-di-n-propylamine, nitrose
diethyl-amine and nitrosopyrrolidine) and their fate compounds (Fig. 16.3).
16.4 Factors Affecting Toxicity of Organic and Inorganic
Pollutants in Soil
Even though wide range of pollutants is present, their reactivity and bioavailability
in soil are controlled by many of their physico-chemical and biological properties
(Kabata-Pendias and Pendias 2011; Kodešová et al. 2011).
16.4.1 Soil Texture and Mineralogy
Soil texture signifies the relative amounts of sand, silt and clay proportions in soil.
High clay (particles size < 0.002 mm) fraction in soil has strong ability to bind
positively charged ions due to their layered structure, large specific surface area,
chemical and mechanical stability and high cation exchange capacity (Uddin 2017).
On contrary, sandy soils have larger pore size and lower sorption capacity which
lead to the movement of pollutants to ground and surface water (Uddin 2017). Thus,
soils having higher amounts of clay and humus have high buffering and sorption
capacity which, despite the increase in concentrations of contaminants, do not cause
adverse biological effects (Różański et al. 2016). Presence of minerals such as
layered silicates, oxides/hydroxides of Fe and Al, carbonates, sulphates, allophane
and associated amorphous clays is inorganic, while humus is organic colloid, which
has high cation adsorption capacity. Fijałkowski et al. (2012) showed the affinity of
metal cations for clay minerals in a series Cu
2+
>Cd
2+
>Fe
2+
>Pb
2+
> Ni
2+
>Co
2
+
>Mn
2+
>Zn
2+ .
16.4.2 The pH and Electrical Conductivity
16.4.2.1 Changes in Surface Charge
Change in pH and salinity of soil greatly influences the net negative charge on the
charged colloids (clays, silicates, oxides/hydroxides of Fe and Al), their ion
exchange capacities and the binding energies of their sorption sites (Proust 2015;
Violante et al. 2010). Thus, increase in surface charge on inorganic and organic
colloids lowers the availability of pollutants in soil.
16.4.2.2 Competition for Adsorption Sites
Under acidic condition of soil, more protons are available to the binding sites of
clays, organic matter and oxides, thus enabling organic and inorganic species more
available to biological organisms (Rampazzo et al. 2013). On the contrary, under
460
M. Gautam et al.
polybrominated diethyl ethers, bisphenol-A and hexabromocyclododecanes),
nitrosamines (e.g., nitrose dimethylamine, nitrose-di-n-propylamine, nitrose
diethyl-amine and nitrosopyrrolidine) and their fate compounds (Fig. 16.3).
16.4 Factors Affecting Toxicity of Organic and Inorganic
Pollutants in Soil
Even though wide range of pollutants is present, their reactivity and bioavailability
in soil are controlled by many of their physico-chemical and biological properties
(Kabata-Pendias and Pendias 2011; Kodešová et al. 2011).
16.4.1 Soil Texture and Mineralogy
Soil texture signifies the relative amounts of sand, silt and clay proportions in soil.
High clay (particles size < 0.002 mm) fraction in soil has strong ability to bind
positively charged ions due to their layered structure, large specific surface area,
chemical and mechanical stability and high cation exchange capacity (Uddin 2017).
On contrary, sandy soils have larger pore size and lower sorption capacity which
lead to the movement of pollutants to ground and surface water (Uddin 2017). Thus,
soils having higher amounts of clay and humus have high buffering and sorption
capacity which, despite the increase in concentrations of contaminants, do not cause
adverse biological effects (Różański et al. 2016). Presence of minerals such as
layered silicates, oxides/hydroxides of Fe and Al, carbonates, sulphates, allophane
and associated amorphous clays is inorganic, while humus is organic colloid, which
has high cation adsorption capacity. Fijałkowski et al. (2012) showed the affinity of
metal cations for clay minerals in a series Cu
2+
>Cd
2+
>Fe
2+
>Pb
2+
> Ni
2+
>Co
2
+
>Mn
2+
>Zn
2+ .
16.4.2 The pH and Electrical Conductivity
16.4.2.1 Changes in Surface Charge
Change in pH and salinity of soil greatly influences the net negative charge on the
charged colloids (clays, silicates, oxides/hydroxides of Fe and Al), their ion
exchange capacities and the binding energies of their sorption sites (Proust 2015;
Violante et al. 2010). Thus, increase in surface charge on inorganic and organic
colloids lowers the availability of pollutants in soil.
16.4.2.2 Competition for Adsorption Sites
Under acidic condition of soil, more protons are available to the binding sites of
clays, organic matter and oxides, thus enabling organic and inorganic species more
available to biological organisms (Rampazzo et al. 2013). On the contrary, under
460
M. Gautam et al.