Are Grasses Really Useful for the Phytoremediation of Potentially Toxic Trace Elements? A Review.

Flávio Henrique Silveira Rabêlo,Antony Van Der Ent,Luís Reynaldo Ferracciú Alleoni,Alan J M Baker,Jaco Vangronsveld

doi:10.3389/fpls.2021.778275

Abstract

The pollution of soil, water, and air by potentially toxic trace elements poses risks to environmental and human health. For this reason, many chemical, physical, and biological processes of remediation have been developed to reduce the (available) trace element concentrations in the environment. Among those technologies, phytoremediation is an environmentally friendly in situ and cost-effective approach to remediate sites with low-to-moderate pollution with trace elements. However, not all species have the potential to be used for phytoremediation of trace element-polluted sites due to their morpho-physiological characteristics and low tolerance to toxicity induced by the trace elements. Grasses are prospective candidates due to their high biomass yields, fast growth, adaptations to infertile soils, and successive shoot regrowth after harvest. A large number of studies evaluating the processes related to the uptake, transport, accumulation, and toxicity of trace elements in grasses assessed for phytoremediation have been conducted. The aim of this review is (i) to synthesize the available information on the mechanisms involved in uptake, transport, accumulation, toxicity, and tolerance to trace elements in grasses; (ii) to identify suitable grasses for trace element phytoextraction, phytostabilization, and phytofiltration; (iii) to describe the main strategies used to improve trace element phytoremediation efficiency by grasses; and (iv) to point out the advantages, disadvantages, and perspectives for the use of grasses for phytoremediation of trace element-polluted soils.

Highlights

The concentrations of potentially toxic trace elements in the environment have been increasing year by year due to anthropogenic activities such as mining, smelting, untreated sewage disposal, and use of pesticides and fertilizers in agriculture (Kabata-Pendias, 2011)
In order to screen grasses according to their use for trace element phytoremediation, we briefly described below the main aspects associated with phytoextraction, phytostabilization, and phytofiltration, and examples of appropriate species for each strategy, considering the fact that there exists trace element specificity within most grass species
The most existing studies aiming to better understand the physiological processes of the induction of trace element toxicity and how grasses cope with this toxicity are based on acute trace elements exposure

Summary

Introduction

The concentrations of potentially toxic trace elements in the environment have been increasing year by year due to anthropogenic activities such as mining, smelting, untreated sewage disposal, and use of pesticides and fertilizers in agriculture (Kabata-Pendias, 2011). Grasses and Trace Elements that can seriously affect both environmental quality and human health (Food and Agriculture Organization of the United Nations [FAO] and United Nations Environment Programme [UNEP], 2021). For this reason, many civil engineering remediation processes such as chemical extraction, ion exchange, membrane separation, and electrokinetics were developed to reduce trace element contamination in the soil (Selvi et al, 2019). Plant-based technologies, generally termed phytoremediation, that are considered environmentally friendly, non-invasive, energy-efficient (mainly sun-powered), and cost-effective to remediate sites with low-to-moderate concentrations of trace elements are proposed as alternative approaches (Vangronsveld et al, 2009). If phytoremediation is chosen to remediate trace element pollution, the question is which kind of plant is the most suitable for this purpose? No general answer to this question can be given, as there exist different options for different cases (Tordoff et al, 2000; Vangronsveld et al, 2009)

Objectives

Findings

Conclusion