pathways and lead to diseases related to human cardiovascular, nervous, kidney, and
bone [9].
Other classes of pollutants present in soil are organic pollutants. Organic pollutants may be hydrocarbons characterized by saturated, unsaturated, linear, or openchain structures and aromatic hydrocarbon or derivative compounds such as pesticides. Some pesticides are non-biodegradable and are persistent organic pollutants.
Their behavior in soil can affect their fate, degree of removal, sequestration, and
potential intervention to the microflora [10]. Studies show that most of the polycyclic
aromatic hydrocarbons are mutagenic, toxic, and carcinogenic. Their high solubility
in lipids facilitates the absorption to the mammalian body. Naphthalene and pyrene
can adhere to the kidney, liver, and lung cells [11]. Other organic contaminants like
PAH and PCB are found to contaminate the soil too [12]. The degree of retention of
pesticides and their transformation products depend on soil-pesticide interactions
which in turn depend on the soil characteristics and pesticide properties. The organic
matter content, pH, and surface charges of the soil influence the adsorption of
pesticides and transformation products [13, 14]. They can harm beneficial soil
microorganisms and reduce soil fertility. Pesticides can reach surface water or
groundwater through runoff or percolation from treated soil. Many pesticides are
highly toxic to fish and cause the death of fish in waterways near treated fields
[13]. Organochlorine or organophosphate or carbamate pesticides are considered as
endocrine disrupters.
The non-biodegradable organic pollutants and heavy metals present in the soil
accumulate in the environment. This leads to the risk to the environment by making
the soil unsuitable for agricultural activities. The runoff waters from the soil contaminate the surface water and groundwater, making water unsuitable for drinking.
Contaminants in the soil and water enter into the plant bodies or aquatic animals and
accumulate in the living tissues of an organism which ascend to a higher living
organism through food chain. Thus, remediation of contaminated soil is essential.
1.3 Soil Remediation
Physical, chemical, or biological methods are used to remediate the contaminated
soil. The treatment methods may be in situ or ex situ. In in situ methods, contaminated soil is treated at the site of its occurrence [15]. In ex situ methods, the
contaminated soil is excavated and taken to the place of treatment for remediation
[16]. Chemical and physical treatments of contaminated soil are excavation and
removal, extraction, electrochemical treatment, soil washing to remove the contaminants, thermal treatment, oxidation, and reduction [17, 18] However, physical and
chemical treatments could potentially [19] cause a deleterious impact on the soil
properties. Besides, extraction of contaminants from the soil is laborious because it
contains a number of heavy metals like lead, chromium, and mercury; other inorganic ions such as arsenic, cesium, and strontium; organic compounds like trichloroethylene; radioactive materials like uranium; explosives such as 1,3,5-trinitroPhytoremediation of Soil for Metal and Organic Pollutant Removal
47
bone [9].
Other classes of pollutants present in soil are organic pollutants. Organic pollutants may be hydrocarbons characterized by saturated, unsaturated, linear, or openchain structures and aromatic hydrocarbon or derivative compounds such as pesticides. Some pesticides are non-biodegradable and are persistent organic pollutants.
Their behavior in soil can affect their fate, degree of removal, sequestration, and
potential intervention to the microflora [10]. Studies show that most of the polycyclic
aromatic hydrocarbons are mutagenic, toxic, and carcinogenic. Their high solubility
in lipids facilitates the absorption to the mammalian body. Naphthalene and pyrene
can adhere to the kidney, liver, and lung cells [11]. Other organic contaminants like
PAH and PCB are found to contaminate the soil too [12]. The degree of retention of
pesticides and their transformation products depend on soil-pesticide interactions
which in turn depend on the soil characteristics and pesticide properties. The organic
matter content, pH, and surface charges of the soil influence the adsorption of
pesticides and transformation products [13, 14]. They can harm beneficial soil
microorganisms and reduce soil fertility. Pesticides can reach surface water or
groundwater through runoff or percolation from treated soil. Many pesticides are
highly toxic to fish and cause the death of fish in waterways near treated fields
[13]. Organochlorine or organophosphate or carbamate pesticides are considered as
endocrine disrupters.
The non-biodegradable organic pollutants and heavy metals present in the soil
accumulate in the environment. This leads to the risk to the environment by making
the soil unsuitable for agricultural activities. The runoff waters from the soil contaminate the surface water and groundwater, making water unsuitable for drinking.
Contaminants in the soil and water enter into the plant bodies or aquatic animals and
accumulate in the living tissues of an organism which ascend to a higher living
organism through food chain. Thus, remediation of contaminated soil is essential.
1.3 Soil Remediation
Physical, chemical, or biological methods are used to remediate the contaminated
soil. The treatment methods may be in situ or ex situ. In in situ methods, contaminated soil is treated at the site of its occurrence [15]. In ex situ methods, the
contaminated soil is excavated and taken to the place of treatment for remediation
[16]. Chemical and physical treatments of contaminated soil are excavation and
removal, extraction, electrochemical treatment, soil washing to remove the contaminants, thermal treatment, oxidation, and reduction [17, 18] However, physical and
chemical treatments could potentially [19] cause a deleterious impact on the soil
properties. Besides, extraction of contaminants from the soil is laborious because it
contains a number of heavy metals like lead, chromium, and mercury; other inorganic ions such as arsenic, cesium, and strontium; organic compounds like trichloroethylene; radioactive materials like uranium; explosives such as 1,3,5-trinitroPhytoremediation of Soil for Metal and Organic Pollutant Removal
47