Role of Phytoremediation in Reducing Cadmium Toxicity in Soil and Water

Abstract

Heavy metals are a noxious form of pollutants present in soil and water. A new plant-based solar energy driven technology, phytoremediation, emerges as eco-friendly and cost-effective approach to remove heavy metal from various media with the help of hyperaccumulating plant species. This review paper aims to provide information on phytoremediation and its mechanisms for heavy metal removal especially to focus on Cadmium (Cd) metal and highlights the role of various hyperaccumulating plants for Cd metal remediation in soil and water. It complies various field case studies which play the important role in understanding the Cd removal through various plants. Additionally, it pinpoints several sources and the effects of Cd and other technologies used for Cd remediation. This paper provides the recent development in mechanisms of Cd hyperaccumulation by different plants, in order to motivate further research in this field.

Cadmium Hyperaccumulation and Translocation in Impatiens Glandulifera: From Foe to Friend?

“…Indeed, the tall stems of I. glandulifera provide a large surface area over which to accumulate Cd. Though hyperaccumulators such as Arabidopsis halleri and Thlapsi caerulescens possess very high tolerance for Cd, the use of these species is limited due to the limited range of environmental conditions in which they can thrive [63]. As I. glandulifera is an invasive, it may be possible to cultivate this species in a broader range of environmental conditions.…”

“…In one study, H. cannabinus was cultivated in such a way as to collect the leaves as they fell from the plant during the growing season. This consideration may be worthwhile for future I. glandulifera plant trials (particularly field trials) to prevent Cd leaching back into the environment [63][64][65]. The flowers of I. glandulifera accumulated Cd up to 136 mg/kg (see Table 3).…”

“…Similar to I. glandulifera, other phytoaccumulator species have attained BCFs of up to 100 [70]. Impressively, the roots of the floating macrophyte Azolla pinnata, which is especially good at bioaccumulating Cd when exposed to levels less than 1 mg/kg, were reported to have a BCF of 24,000 [63]. The translocation factor, which indicates the plant's ability to translocate the pollutant from the roots to the aerial parts of the plant, for I. glandulifera was low-only plants in Cd-50 achieved a TF value greater than unity (see Table 2).…”

“…Though many phytoaccumulator plants such as Brassica juncea or Panicum virgatum are not effective at removing Cd when soil levels are low, there are many species that show great potential to be used to bioaccumulate Cd in soils with levels as low as 0.33 mg/kg. These species include T. caerulescens, Hibiscus cannabinus, Azolla pinnata, Lemna minor, Vertiever grass, rice, maize, and sugar beet [63,64,70,72]. Indeed, even H. annus grown in control soil and not treated with Cd was found to accumulate Cd, though at a lesser extent than the Cd treatments [61].…”

“…The ability to translocate Cd to the aboveground parts is critical for efficacious phytoremediation. However, species with high tolerance and BCF values that cannot effectively translocate Cd to the stems are often useful for phytostabilization [63,76].…”