Phytomanagement of Metal(loid)-Contaminated Soils: Options, Efficiency and Value

Abstract

The growing loss of soil functionality due to contamination by metal(loid)s, alone or in combination with organic pollutants, is a global environmental issue that entails major risks to ecosystems and human health. Consequently, the management and restructuring of large metal(loid)-polluted areas through sustainable nature-based solutions is currently a priority in research programs and legislation worldwide. Over the last few years, phytomanagement has emerged as a promising phytotechnology, focused on the use of plants and associated microorganisms, together with ad hoc site management practices, for an economically viable and ecologically sustainable recovery of contaminated sites. It promotes simultaneously the recovery of soil ecological functions and the decrease of pollutant linkages, while providing economic revenues, e.g. by producing non-food crops for biomass-processing technologies (biofuel and bioenergy sector, ecomaterials, biosourced-chemistry, etc.), thus contributing to the international demand for sustainable and renewable sources of energy and raw materials for the bioeconomy. Potential environmental benefits also include the provision of valuable ecosystem services such as water drainage management, soil erosion deterrence, C sequestration, regulation of nutrient cycles, xenobiotic biodegradation, and metal(loid) stabilization. Phytomanagement relies on the proper selection of (i) plants and (ii) microbial inoculants with the capacity to behave as powerful plant allies, e.g., PGPB: plant growth-promoting bacteria and AMF: arbuscular mycorrhizal fungi. This review gives an up-to-date overview of the main annual, perennial, and woody crops, as well as the most adequate cropping systems, presently used to phytomanage metal(loid)-contaminated soils, and the relevant products and ecosystems services provided by the various phytomanagement options. Suitable bioaugmentation practices with PGPB and AMF are also discussed. Furthermore, we identify the potential interest of phytomanagement for stakeholders and end-users and highlight future opportunities boosted by an effective engagement between environmental protection and economic development. We conclude by presenting the legal and regulatory framework of soil remediation and by discussing prospects for phytotechnologies applications in the future.

Remediation of Agricultural Soils with Long-Term Contamination of Arsenic and Copper in Two Chilean Mediterranean Areas

“…The present study is one of the first attempts to evaluate amendments to remediate contaminated soils in critical agricultural areas coexisting with the mining industry in central Chile. We obtained promising results, but these are not enough to fulfill a holistic remediation approach as is required nowadays by research programs and legislation worldwide [66,67]. A holistic remediation approach must consider the potential human health risks, the interlinks between contaminant exposure, the remediation technology, and the ecological effects, including climate change.…”

Reflections and Insights on the Evolution of the Biological Remediation of Contaminated Soils

“…Importantly, most environmental legislations are based on total metal concentrations, not on bioavailable metal concentrations, leading to the impracticability of this phytotechnology from a legal point of view. This fact invalidates all those phytoremediation options aimed at removing the bioavailable contaminant fraction ("bioavailable contaminant stripping"), a target which considerably reduces the length of time required for soil remediation while addressing contaminant linkages (Moreira et al, 2021). In some countries, regulators are starting to consider bioavailability in risk assessment frameworks, but its implementation remains complicated because scientific developments on bioavailability are not easily translated into ready-to-use approaches for regulators (Ortega-Calvo et al, 2015).…”

“…Finally, plant-assisted bioremediation, based on the potential stimulatory effect of plant growth on the activity of rhizosphere microorganisms (e.g., via the exudation of easily degradable carbon sources and oxygen transport), presents some of the same limitations associated to all plant-based remediation technologies: root depth, area covered by the roots (contaminants can be in the bulk soil), time required for plant growth, etc. (Moreira et al, 2021). In order to overcome these limitations, the use of transgenic plants in phytoremediation has often been proposed (Doty, 2008;Ozyigit et al, 2021).…”

Induced dormancy in Indian meal moth Plodia interpunctella (Hübner) and its impact on the quality improvement for mass rearing in parasitoid Habrobracon hebetor (Say)

“…The mechanistic basis for diapause or other forms of dormancy reducing the efficacy of fumigants like phosphine in stored-product pests is currently unknown. However, insects that have become dormant either through programmed diapause or environmental factors, like low temperature or low humidity, also frequently have both lower respiration rates that could limit the entrance of gaseous fumigants into the insect's body, and increased expression of a number of stress hardiness mechanisms such as antioxidants that could help reduce intracellular damage due to off-target effects of pesticide metabolism by mixed-function oxidases (Denlinger, 2002; Hahn and Denlinger, 2011; Sahoo et al ., 2018; Moreira et al ., 2021).…”