A critical review on the bio-removal of hazardous heavy metals from contaminated soils: Issues, progress, eco-environmental concerns and opportunities

Abstract

a b s t r a c tMechanism of four methods for removing hazardous heavy metal are detailed and comparedchemical/physical remediation, animal remediation, phytoremediation and microremediation with emphasis on bio-removal aspects. The latter two, namely the use of plants and microbes, are preferred because of their cost-effectiveness, environmental friendliness and fewer side effects. Also the obvious disadvantages of other alternatives are listed. In the future the application of genetic engineering or cell engineering to create an expected and ideal species would become popular and necessary. However, a concomitant and latent danger of genetic pollution is realized by a few persons. To cope with this potential harm, several suggestions are put forward including choosing self-pollinated plants, creating infertile polyploid species and carefully selecting easy-controlled microbe species. Bravely, the authors point out that current investigation of noncrop hyperaccumulators is of little significance in application. Pragmatic development in the future should be crop hyperaccumulators (newly termed as "cropaccumulators") by transgenic or symbiotic approach. Considering no effective plan has been put forward by others about concrete steps of applying a hyperaccumulator to practice, the authors bring forward a set of universal procedures, which is novel, tentative and adaptive to evaluate hyperaccumulators' feasibility before large-scale commercialization.

Screening Indian Mustard Genotypes for Phytoremediating Arsenic‐Contaminated Soils

“…The As accumulation was higher in shoot than in the root, implying that a considerable amount of As was translocated to the aerial plant parts. A similar observation was also previously reported [5,11,[50][51][52][53][54][55][56][57][58][59][60][61].…”

“…Moreover, the inhibition of biomass accumulation may also result from inhibition of cell division resulting in the decline in growth [45]. At higher As concentrations it might be due to the reduced enzyme activity [46][47][48] and/or the As-induced oxidative stress [39,48].We have also been observed in our earlier studies, as influenced by heavy metals induced oxidative stress in Indian mustard by modulation of antioxidant enzymes [49][50][51][52][53][54][55][56][57].…”

Phytoremediation of Cadmium‐Contaminated Soil by Two Jerusalem Artichoke (Helianthus tuberosus L.) Genotypes

“…However, a lot of studies have focused on the metal tolerance and metal concentration in hyperaccumulator tissues [39,[46][47][48][49][50][51][52][53][54][55][56][57][58][59], but ignored the biomass production, which limited the applicability of results in terms of actual phytoextraction. For example, fast-growing plant as poplar (Populus deltoids  Populus nigra) exhibited high phytoextraction efficiency with high biomass production (Tab.…”

Copper changes the yield and cadmium/zinc accumulation and cellular distribution in the cadmium/zinc hyperaccumulator Sedum plumbizincicola

“…Dry plant samples (∼0.25 g DM) and the residues from the sequential extraction were digested with a mixture of 6 ml HNO 3 and 4 ml HClO 4 . Digestion solutions were determined for Cd, Zn and Cu using AAS (Varian SpectrAA 220 FS).…”

“…Phytoremediation using hyperaccumulator plants to remove contaminants from soils is an environmentally friendly and relatively inexpensive technique [3][4][5]. However, most hyperaccumulators can typically remediate only a very limited number of pollutants so that other nonaccumulated metals (i.e.…”