Comparison of the Efficiency of Micro- and Nanoparticles of Zero-Valent Iron in the Detoxification of Technogenically Polluted Soil

The safety of micro- and nanoparticle sorbents based on zero-valent iron and their detoxifying activity in peat eutrophic soil (Eutric Histosol) polluted by the emissions of a copper-nickel (Cu/Ni) plant in the Kola Peninsula are studied. Both iron nanoparticles and microparticles at a dose of 2% have emerged to be nontoxic according to the results of three standard bioassays based on the response of test organisms of different taxonomic affiliations. The toxicity is assessed according to the change in the root length of Sinapis alba L. seedlings in uncontaminated peat as well as the survival rate of the crustacean Ceriodaphnia affinis Lilljeborg and the protozoan Paramecium caudatum Ehrenberg in water extracts obtained of samples. Iron-containing preparations in a statistically significant manner reduce the ecotoxicity of soil caused by an extremely high content of copper (6877 mg/kg) and nickel (2580 mg/kg). The tested preparations differ in their remediation capacity. Soil phytotesting demonstrates that iron nanoparticles significantly outperform the detoxifying effect of microparticles (iron powder). However, analysis of water extracts does not show any advantage of nanoparticles in reducing the soil toxicity. The dependence of the assessed detoxifying capacity of zero-valent iron nanoparticles on soil properties and the plant species used in phytotesting is discussed. The phytoeffect of nanoparticles in standard S. alba tests is 1.5-fold higher as compared with iron microparticles (root length of 117 ± 4.3 and 80 ± 7.6 mm, respectively). However, the chronic phytotoxicity assessment of the same soils using perennial ryegrass Lolium perenne L. fails to find any differences between the effects of micro- and nanoparticles of zero-valent iron.