**2. Soils contaminated by heavy metals**

Currently, the agricultural soils suffer from high concentrations of metals, such as As, Cd, Cr, Cu, Pb, Ni, Zn [11, 12] and Hg [13], exceeding the maximum permissible levels and causing a potential risk; industrial soils can be up to 2600 mg kg−<sup>1</sup> of lead [14], being important to know your inputs and outputs [15]. The countries with the highest cadmium concentrations are Jamaica (200 mg kg−<sup>1</sup> ), India and Pakistan (19–20 mg kg−<sup>1</sup> ), Tunisia, and UK (10–16 mg kg−<sup>1</sup> ) [16]. Other sources of soil contamination are the mining industries and the processing of minerals, which have been found in ascending values: Cd (0.7) → Cu (3.9) → Mn (76) → Fe (79) → Zn (110) → Pb (126) [17].

**3. Soils contaminated by hydrocarbons**

in China, they have found between 131,019 m3

**Figure 1.** Scheme of the interaction of the pollutant with the agroecosystem.

The global economy based on the oil industry has deteriorated natural resources around the world, with soil being one of the most affected [31]. Total petroleum hydrocarbons (TPH) contain fractions that are toxic to the beneficial organisms of the soil and for humans; this has become an important issue for the development of public policies, food safety, and environmental health

Introductory Chapter: Soil Contamination and Alternatives for Sustainable Development

Oil activities have mainly affected the tropical areas; this pollution has deteriorated soil sustainability, because its toxic effect decreases the ability to support living organisms [33], disrupts the biogeochemical cycles deteriorating ecosystems and altering fertility [34], and reduces quality of soil and agricultural potential [35]. Even hydrocarbons such as benzo[a]pyrene (BaP), belonging to one of the most toxic polycyclic aromatic hydrocarbons (PAHs) in the soil–plant system, are potentially mutagenic and carcinogenic for humans [36]. According to results from researchers

[a] pyrene; it should be mentioned that pollutants are accumulated mainly in the first layer of the site (0–1 meter) [37]. Its main impact on human health is centered on its genotoxic properties (teratogenic, mutagenic, and carcinogenic) (**Figure 1**). The International Agency for Research on Cancer (IARC) and the World Health Organization (WHO) have reported as probable human carcinogens to benzo [a] anthracene, benzo [a] pyrene and dibenzo [a, h] anthracene, benzo [ b] fluoranthene, benzo[k]fluoranthene, indene, pyrene and naphthalene; where some researchers have proposed the combination of risk assessments (governmental and computational) [38].

The refining and processing of petroleum can also send numerous chemical compounds to the atmosphere, such as naphthalene, which is considered a dangerous compound in the air

and 146,783 m3

of soil contaminated with benzo

http://dx.doi.org/10.5772/intechopen.83720

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because it produces changes in structure and function of soil ecosystems (**Figure 1**) [32].

However, this pollution problem is an important issue for public policies, because the risk assessment must be integrated into the framework of public health and environmental security [18], because concentrations of heavy metals have been found in crops closely related to soil contamination, for example, according to the Chinese environmental quality standard for soil (GB15618–1995), 64.4, 78.9, 67.5, and 94.1% of the soil samples in Dexing, Yangjiazhangzhi, Hongqiling, and Baiyin exceed the maximum allowed concentration of Cd for farmland, respectively [19]. The risk assessment has indicated that priority attention is required due to the carcinogenic risk of Cr, Cd, and As in soil and rice grains, as well as the potential ecological risks [20].

In addition to this, associations have been found between some bacterial genera (*Geodermatophilus* spp., *Rhodovibrio* spp., and *Rubrobacter* spp.) with the presence of heavy metals such as copper, lead, and zinc, respectively [21]. In this regard, **Table 1** shows some examples of heavy metal remediation.

The cost and duration of soil remediation depend on the technique and the site specific, up to \$500 tons−<sup>1</sup> (\$1500 m−<sup>3</sup> soil or \$100 m−<sup>2</sup> soil) and 15 years [30], while it has estimated 20 million hectares of land contaminated by heavy metal.


**Table 1.** Examples of remediation of soils contaminated by heavy metals.
