Engineered Nanomaterials for Phytoremediation of Metal/Metalloid-Contaminated Soils: Implications for Plant Physiology

Nanomaterials, including engineered nano-sized iron oxides, manganese oxides, cerium oxides, titanium oxides, or zinc oxides, provide specific affinity for metal/metalloids adsorption and their application is being rapidly extended for environmental management. Their significant surface area, high number of active surface sites, and high adsorption capacities make them very promising as cost-effective amendments for the remediation of contaminated soils. The alleviation of the toxicities of metal/metalloids by their immobilization in the soil stimulates the growth and development of plants during phytoremediation, but there is a body of evidence indicating that nanomaterials themselves can yield both beneficial and harmful effects in plant systems at the physiological, biochemical, nutritional, and genetic levels. Nanoecotoxicological studies are providing a good understanding of their interactions with plants, and an increasing number of publications have attempted to clarify and quantify their potential risks and consequences for plants. However, many results are contradictory and the safety of engineered nanomaterials still represents a barrier to their wide, innovative use in phytoremediation. Both their positive and negative effects on plants will have to be taken into account to evaluate their applicability, and the scientific community faces a challenge to understand deeply the factors which can determine their relevance in environmental science and technology.