Plants growing in polluted soils exhibit several strategies to coping with the toxicity of HMs including preventing their accumulation, detoxification or metal excretion from the tissues. In nature certain plant species can stock very high quantities of toxic HMs to levels which exceed the soil contents. Last, some recent innovative technologies for improving phytoremediation and future prospects like over expression of foreign genes in non-tolerant plants, nanoparticles (NPs) addition and phytoremediation assisted with phytohormones, microbial and AMF inoculation are presented. This critical review describes the effective mechanisms of phytoremediation, the promising potential of hyper-accumulator plants and the biotechnological approach for HMs decontamination. These limitations need to be overcome by transgenic approach applications to improve HMs tolerance/accumulation of these plants. However, there are some limitations for these plants to become efficient at large scale. Plant hyper-accumulators have received greater attention in recent decades, due to its potential to HMs contamination. Hence this green technology can be very useful for remediation of HMs contaminated soils/agro-ecosystems. Plants were classified to be tolerant and/or hyper-accumulator to HMs when they show rapid growth, high biomass and are capable to extract and accumulate high amounts of HMs in their shoots, without signs of toxicity when grown in contaminated soils (Table 3). According to the soil conditions, pollutant and the species of plants used, five types of phytoremediation have been applied: phytodegradation, phytofiltration, phytoextraction phytostabilization and phytovolatilization. This technology is considered as well-efficient, cheap and adaptable with the environment. Phytoremediation is a green strategy that uses hyper-accumulator plants and their rhizospheric microorganisms to stabilize, transfer or degrade pollutants in soil, water and environment. The modification of soil properties (especially pH), risk of soil fertility loss, small-scale application and by-product generations are the main disadvantages and drawbacks of these techniques. Ĭhemical methods for HMs decontamination such as excavation, precipitation, heat treatment, electroremediation and chemical leaching are still costly and depend on the pollutant and soil characteristics. These pollutants can be accumulated in food chains, causing harmful effects on plants, animals and humans (damage to the endocrine system, impact on immunity, neurological disorders and cancer). For a long time, humans have supplemented great quantities of pollutants to the soil, water and atmosphere biotopes as a consequence of industrial activities, such as mining of ores, gas emission, pesticide application and municipal waste production. The progress of demographic population combined with high industrial development causes serious environmental hazards. Last, some recent innovative technologies for improving phytoremediation are highlighted. In this review, aspects of HMs toxicity and their depollution procedures with focus on phytoremediation are discussed. Traditional phytoremediation method presents some limitations regarding their applications at large scale, so the application of genetic engineering approaches such as transgenic transformation, nanoparticles addition and phytoremediation assisted with phytohormones, plant growth-promoting bacteria and AMF inoculation has been applied to ameliorate the efficacy of plants as candidates for HMs decontamination.
Five types of phytoremediation technologies have often been employed for soil decontamination: phytostabilization, phytodegradation, rhizofiltration, phytoextraction and phytovolatilization. Such a strategy uses green plants to remove, degrade, or detoxify toxic metals. Among these, phytoremediation is a promising method based on the use of hyper-accumulator plant species that can tolerate high amounts of toxic HMs present in the environment/soil. However, many strategies are being used to restore polluted environments. Chemical methods for heavy metal's (HMs) decontamination such as heat treatment, electroremediation, soil replacement, precipitation and chemical leaching are generally very costly and not be applicable to agricultural lands. Toxic metal contamination of soil is a major environmental hazard.
0 kommentar(er)
