Research Information System
2nd International Conference on Recycling and Reuse, İstanbul, Turkey, 4 - 06 June 2014, pp.253-254, (Full Text)
Soils are polluted by actions like unreasonable utilization of fertilizers, pesticides, soil regulators and hormones used for increasing the amount and quality of agricultural production, discharge of soil and liquid wastes, performing wastewater sludge applications, using polluted waters in agricultural irrigation, atmospheric precipitations and radioactive sprays.
Recently, contamination of soils with heavy metal is an important environmental issue. Since heavy metals are toxic to the living organisms even at very low concentrations, heavy metal pollution is very unfavorable to the environment (Memon and Schröder, 2009).
Phytoremediation uses several plants named as accumulators to remove pollutants from water and soil to reduce, completely extract, control or immobilize them. Several different families like small annual grass to perennial bushes and trees can accumulate the metals. The ideal plant species for remediation or cleaning of the heavy metal contaminated soils are the ones which can produce high amounts of biomass, and can accumulate and tolerate the pollutants (Wu et al., 2007).
Some plants can hyperaccumulate metal ions which can be hazardous to essentially all other organisms at low dosages. This feature could be used to clean up metal-contaminated soils. On the other hand, it is known that the accumulation of heavy metals by plants determines both the micronutrient content and the toxic metal content of our food. The rates of metal uptake and storage are controlled by complex interactions of transport and chelating activities. Recently, several key steps have been identified at the molecular level, enabling scientists to initiate transgenic approaches to engineer the transition metal content of plants (Clemens et al. 2002).
In removing pollutant from soil by plants, acceptable soil conditions should exist. The most important parameter in pollutant removal from soil is the soil pH value. However, many other factors affect the heavy metal intake capacity of the plant (Martens and Boyd, 1994; Fergusson, 1990; USDA, 2000). The elements, after gaining mobility, are retarded by the root cells of the plant. After bounding to the cellular wall, they are passed through the membrane with transport systems and intracellular binding regions. It is thought that the intake of element ions is carried out by the channel and/or carrier proteins. The negative charge of inner plasma membrane plays an important role for the cation intake (Clemens et al., 2002). Excessive heavy metal presence causes toxic symptoms to occur, which are caused by interactions on cellular and molecular level. Besides, the excess amount of heavy metals also causes oxidative stress. The reason of the oxidative stress is the promotion of free radicals and reactive oxygen species (Hall, 2002).
This paper reviews the phytoremediation technology for remediation of heavy metal-contaminated soils. Phytoremediation technology has been recently extensively reviewed. However, in this paper, the hyperaccumulator plants used in phytoremediation are considered and particular focus is given to the hyperaccumulator plants which are common and native throughout Turkey.