Extraction of Heavy Metals from Contaminated Soil by Two Amaranthus spp.

Abstract

Two medicinal species of amaranth, Amaranthus viridis L. and A. caudatus L. were evaluated for their ability to uptake heavy metals from a contaminated soil. Twenty healthy plants of each species were transplanted to plastic pots containing the soil contaminated with elevated concentrations of Cd, Cr, Cu, Ni, Pb, and Zn. The plants were harvested after 45 days. Below‐ and above‐ground tissues (roots and shoots) were analyzed separately to determine metals concentrations. Compared with the control group, the effects of S,S‐ethylenediaminedisuccinic acid (S,S‐EDDS) on the uptake of Cd, Cr, Cu, Ni, Pb, and Zn by two medicinal plants were also investigated. The initial contaminant concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in soil were 2.34, 30.53, 16.14, 20.99, 35.77, and 102.31 mg/kg, respectively. The results of metal accumulation with EDDS application showed that EDDS was more efficient at solubilizing Cu and Zn than the control group. Translocation of metals from roots to shoots was most pronounced for Cu and Zn. The only metal that did not result in a transfer factor (TF) ≥0.3 for at least one of the two test species was Pb. The enrichment factor (E) was also low for Pb. The lower TF and E for Pb illustrated the tendency of that metal to remain bound to soil particles and not transfer into plant tissues. These data suggest that these two medicinal species of Amaranthus could be hyperaccumulators of several of these metals, and were particularly effective in accumulating Zn and Cu. Pb and Cd, while accumulated in measurable amounts, did not decrease significantly in the soil, suggesting these species may not be the best choice for plants to be used when bioremediating Pb‐ or Cd‐contaminated areas.

A meta-analysis on the heavy metal uptake in Amaranthus species

“…After studying six leafy vegetables out of which two were Amaranthus lividus L. and Amaranthus gangeticus L., Ahmed et al ( 2022 ) found the lowest Cu concentrations for the two Amaranthus species. Furthermore, soil amendments (e.g., S,S-EDDS) were found especially effective in solubilizing Cu and triggering its translocation into the leaves of A. viridis and A. caudatus (Ko et al 2013 ). We observed this pattern without the use of any substances, indicating the effectiveness of Amaranthus leaves in Cu accumulation based on its inherent ability.…”

Metabolic responses to zinc stress in Amaranthus caudatus roots and leaves

“…Amaranthus species attract a special interest in the context of Zn stress due to their importance as a source for valuable nutrient-rich foods and fodder crops (Achigan-Dako et al, 2014) with pronounced stress tolerance and well-characterized potential for HM phytoremediation (Watanabe et al, 2009;Bosiacki et al, 2013;Ko et al, 2014). From the point of primary metabolism, this genus is featured with C4 type of photosynthesis (Ludwig, 2016) and elevated production of oxalic acid (Gélinas and Seguin, 2007;Osmolovskaya et al, 2018a).…”

Microbial‐Enhanced Phytoremediation of Lead Contaminated Calcareous Soil by Centaurea cyanus L

“…Phytoremediation, the use of plants along with their microbial association for remediation of contaminated soils, is a promising solar‐driven, cost‐effective and environmentally suitable alternative for restoration of PTEs‐contaminated soils . However, most hyperaccumulator plants usually have low biomass and slow growth, which limits their application in large‐scale operations . Furthermore, while the total Pb concentrations are high in many of the contaminated sites, the bioavailable fraction of Pb is often very low in the soil environment, especially in calcareous soils due to complexation with various organic and inorganic soil colloids, sorption on oxides and clays, and precipitation as carbonate minerals .…”