Zuzana Michálková

Evaluating the potential of three Fe- and Mn-(nano)oxides for the stabilization of Cd, Cu and Pb in contaminated soils.

The potential of three Fe- and Mn-(nano)oxides for stabilizing Cd, Cu and Pb in contaminated soils was investigated using batch and column experiments, adsorption tests and tests of soil microbial activity. A novel synthetic amorphous Mn oxide (AMO), which was recently proposed as a stabilizing amendment, proved to be the most efficient in decreasing the mobility of the studied metals compared to nano-maghemite and nano-magnetite. Its application resulted in significant decreases of exchangeable metal fractions (92%, 92% and 93% decreases of Cd, Cu and Pb concentrations, respectively). The adsorption capacity of the AMO was an order of magnitude higher than those recorded for the other amendments. It was also the most efficient treatment for reducing Cu concentrations in the soil solution. No negative effects on soil microorganisms were recorded. On the other hand, the AMO was able to dissolve soil organic matter to some extent.

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.

Nano Zero-Valent Iron Mediated Metal(loid) Uptake and Translocation by Arbuscular Mycorrhizal Symbioses

Nano zero-valent iron (nZVI) has great potential in the remediation of metal(loid)-contaminated soils, but its efficiency in metal(loid) stabilization in the plant-microbe continuum is unclear. This study investigated nZVI-mediated metal(loid) behavior in the arbuscular mycorrhizal (AM) fungal-maize ( Zea mays L.) plant association. Plants with AM fungal inoculation were grown in metal(loid)- (mainly Zn and Pb) contaminated soils (Litavka River, Czech Republic) amended with/without 0.5% (w/w) nZVI. The results showed that nZVI decreased plant metal(loid) uptake but inhibited AM development and its function in metal(loid) stabilization in the rhizosphere. AM fungal inoculation alleviated the physiological stresses caused by nZVI and restrained nZVI efficiency in reducing plant metal(loid) uptake. Micro proton-induced X-ray emission (μ-PIXE) analysis revealed the sequestration of Zn (possibly through binding to thiols) by fungal structures in the roots and the precipitation of Pb and Cu in the mycorrhizal root rhizodermis (possibly by Fe compounds originated from nZVI). XRD analyses further indicated that Pb/Fe mineral transformations in the rhizosphere were influenced by AM and nZVI treatments. The study revealed the counteractive effects of AM and nZVI on plant metal(loid) uptake and uncovered details of metal(loid) behavior in the AM fungal-root-nZVI system, calling into question about nZVI implementation in mycorrhizospheric systems.