step. The application of mulching film that contains metal elements is also a threat to
the soil environment. Sewage irrigation generally refers to using disposed urban
sewage to irrigate farmland, forest, and grassland. The rapid development of urban
industrialization causes a large amount of industrial wastewater to flow into wastewater treatment plants, so that many of the HM ions contained in urban sewage then
enter the soil. Generally, the closer to industrial areas the more serious is pollution in
the soil environment.
In a word, many avenues will contaminate the soil, either industry sources or
agriculture sources. The entire world faces the challenge of HM contamination in
soil. It is understood from previous reports that in the United States many fields, such
as 600,000 brownfields, were severely polluted with HM and require proper reclamation (McKeehan 2000). Similarly, irrigation water in the country of Georgia has
been contaminated over the decades by HM-laden mining wastes (Felix-Henningsen
et al. 2010); more than 1,400,000 sites in Western Europe have become contaminated with HMs (Wei et al. 2005).
2.6 Biosolids and Livestock Manure Application
Wastewater treatment plants and livestock industries all over the world produce large
amounts of biosolids and manures, which contain huge quantities of organic matter,
nutrients, trace elements, and a variety of infective agents (Chen et al. 2010; Awasthi
et al. 2016). The traditional application of biosolids and manures onto agricultural
lands over a period of time leads to the accumulation of toxic metals and also affects
the ecosystem with a range of contaminants as well as odor pollution (Lüo et al.
2014). However, many technological solutions have been tried to overcome these
problems by effective methods for reducing the levels of HM toxicity in biosolids
and manures (Külcü and Yaldiz 2014), and also by converting toxic organic matter
to a stable, safe, and sanitary fertilizer (Bernal et al. 2009). The excessive application
and presence of high concentrations of HMs during the past two decades suggest
several disadvantages of amendments in the soil and organic farming.
2.7 Fertilizer and Pesticide Application
Various heavy metals such as Cd, Zn, Pb, Cu, and As have begun to accumulate in
the soils because of the extensive use of fertilizers and pesticides over time (Ali et al.
2013). The quality and growth capacity of a plant are consequently influenced by the
accumulation of HMs in the upper soil surfaces from the excessive application of
chemical pesticides and fertilizers, and also, from their production, as runoff from
agricultural fields and industries (Sarwar et al. 2017). Many of the agriculturally
dependent developing countries such as China and India are severely affected by
these problematic issues.
4 Recent Advances in Phytoremediation of Toxic Metals from Contaminated. . .
85
the soil environment. Sewage irrigation generally refers to using disposed urban
sewage to irrigate farmland, forest, and grassland. The rapid development of urban
industrialization causes a large amount of industrial wastewater to flow into wastewater treatment plants, so that many of the HM ions contained in urban sewage then
enter the soil. Generally, the closer to industrial areas the more serious is pollution in
the soil environment.
In a word, many avenues will contaminate the soil, either industry sources or
agriculture sources. The entire world faces the challenge of HM contamination in
soil. It is understood from previous reports that in the United States many fields, such
as 600,000 brownfields, were severely polluted with HM and require proper reclamation (McKeehan 2000). Similarly, irrigation water in the country of Georgia has
been contaminated over the decades by HM-laden mining wastes (Felix-Henningsen
et al. 2010); more than 1,400,000 sites in Western Europe have become contaminated with HMs (Wei et al. 2005).
2.6 Biosolids and Livestock Manure Application
Wastewater treatment plants and livestock industries all over the world produce large
amounts of biosolids and manures, which contain huge quantities of organic matter,
nutrients, trace elements, and a variety of infective agents (Chen et al. 2010; Awasthi
et al. 2016). The traditional application of biosolids and manures onto agricultural
lands over a period of time leads to the accumulation of toxic metals and also affects
the ecosystem with a range of contaminants as well as odor pollution (Lüo et al.
2014). However, many technological solutions have been tried to overcome these
problems by effective methods for reducing the levels of HM toxicity in biosolids
and manures (Külcü and Yaldiz 2014), and also by converting toxic organic matter
to a stable, safe, and sanitary fertilizer (Bernal et al. 2009). The excessive application
and presence of high concentrations of HMs during the past two decades suggest
several disadvantages of amendments in the soil and organic farming.
2.7 Fertilizer and Pesticide Application
Various heavy metals such as Cd, Zn, Pb, Cu, and As have begun to accumulate in
the soils because of the extensive use of fertilizers and pesticides over time (Ali et al.
2013). The quality and growth capacity of a plant are consequently influenced by the
accumulation of HMs in the upper soil surfaces from the excessive application of
chemical pesticides and fertilizers, and also, from their production, as runoff from
agricultural fields and industries (Sarwar et al. 2017). Many of the agriculturally
dependent developing countries such as China and India are severely affected by
these problematic issues.
4 Recent Advances in Phytoremediation of Toxic Metals from Contaminated. . .
85