Phytotoxicity of ionic, micro- and nano-sized iron in three plant species

Potential environmental impacts of engineered nanoparticles (ENPs) can be understood taking into consideration phytotoxicity. We reported on the effects of ionic (FeCl3)​, micro- and nano-​sized zerovalent iron (nZVI) about the development of three macrophytes: Lepidium sativum, Sinapis alba and Sorghum saccharatum. Four toxicity indicators (seed germination, seedling elongation, germination index and biomass) were assessed following exposure to each iron concn. interval: 1.29-​1570 mg​/L (FeCl3)​, 1.71-​10.78 mg​/L (micro-​sized iron) and 4.81-​33,​560 mg​/L (nano-​iron)​. Exposure effects were also obsd. by optical and transmission electron microscopy. Results showed that no significant phytotoxicity effects could be detected for both micro- and nano-​sized zerovalent irons, including field nanoremediation concns. Biostimulation effects such as an increased seedling length and biomass prodn. were detected at the highest exposure concns. Ionic iron showed slight toxicity effects only at 1570 mg​/L and, therefore, no median effect concns. were detd. By microscopy, ENPs were not found in palisade cells or xylem. Apparently, aggregates of nZVI were found inside S. alba and S. saccharatum, although false positives during sample prepn. cannot be excluded. Macroscopically, black spots and coatings were detected on roots of all species esp. at the most concd. treatments.