Phytoremediation and Microorganisms-Assisted Phytoremediation of Mercury-Contaminated Soils: Challenges and Perspectives

Abstract

Mercury (Hg) pollution is a global threat to human and environmental health because of its toxicity, mobility and long-term persistence. Although costly engineering-based technologies can be used to treat heavily Hg-contaminated areas, they are not suitable for decontaminating agricultural or extensively-polluted soils. Emerging phyto- and bioremediation strategies for decontaminating Hg-polluted soils generally involve low investment, simple operation, and in situ application, and they are less destructive for the ecosystem. Current understanding of the uptake, translocation and sequestration of Hg in plants is reviewed to highlight new avenues for exploration in phytoremediation research, and different phytoremediation strategies (phytostabilization, phytoextraction and phytovolatilization) are discussed. Research aimed at identifying suitable plant species and associated-microorganisms for use in phytoremediation of Hg-contaminated soils is also surveyed. Investigation into the potential use of transgenic plants in Hg-phytoremediation is described. Recent research on exploiting the beneficial interactions between plants and microorganisms (bacteria and fungi) that are Hg-resistant and secrete plant growth promoting compounds is reviewed. We highlight areas where more research is required into the effective use of phytoremediation on Hg-contaminated sites, and conclude that the approaches it offers provide considerable potential for the future.

Nodulated White Lupin Plants Growing in Contaminated Soils Accumulate Unusually High Mercury Concentrations in Their Nodules, Roots and Especially Cluster Roots

“…Hg concentrations in roots and nodules are much higher than those previously published for roots of L. albus cv. Marta [13,60,71], eggplant [72], lavender [73], barley [74], rice [75], mung bean [34], olive tree [76] or many other plant species ( [52] and references therein). Some ferns have been reported to accumulate very high Hg concentration in roots, and Nephrolepis exaltata has been proposed as a potential Hg rhizostabilizer [77].…”

“…Even though more than 700 plant species have been described as hyperaccumulators of heavy metals, very few have proven utility in the phytoremediation of contaminated soils since most of them have a high metal specificity (they only accumulate one metal) and are slow-growing, low biomass-producing species [50,51]. To date, no Hg hyperaccumulator species have been identified, although considerable progress has been made in identifying plant species that can grow on Hg-contaminated soil [52]. Thus, Hg rhizostabilization/phytosequestration might represent more feasible phytoremediation strategies to reduce environmental and health risks associated to the presence of Hg in soils.…”

NBS Framework for Agricultural Landscapes

“…The uptake and translocation of antibiotics in maize is another example of the potential use of agricultural crops for phytoremediation (Zhang et al, 2019). A recent review illustrates the efficiency of agriculture and forestry plants in metal extraction from mercury-contaminated soils and water, and also risks of accumulation in edible tissues for animal and human health (Tiodar et al, 2021).…”

The Endophytic Fungus Piriformospora Indica-Assisted Alleviation of Cadmium in Tobacco

“…Combing plants and their associated microorganisms to eliminate contaminants provides a cost-effective, in-situ, and promising technology [ 16 ]. The root-associated microorganisms, such as mycorrhizal fungi and endophytic fungi, can remove, inactivate, or degrade harmful environmental contaminants [ 17 , 18 , 19 ].…”