The commercial usage of Al2O3 nanoparticles (Al2O3 NPs) has gone up significantly in the recent times, enhancing the risk of environmental contamination with these agents and their consequent adverse effects on living systems. The current study has been designed to evaluate the cytogenetic potential of Al2O3 NPs in Allium cepa (root tip cells) at a range of exposure concentrations (0.01, 0.1, 1, 10, and 100 μg/mL), their uptake/internalization profile, and the oxidative stress generated. We noted a dose-dependent decrease in the mitotic index (42 to 28 %) and an increase in the number of chromosomal aberrations. Various chromosomal aberrations, e.g. sticky, multipolar and laggard chromosomes, chromosomal breaks, and the formation of binucleate cells, were observed by optical, fluorescence, and confocal laser scanning microscopy. FT-IR analysis demonstrated the surface chemical interaction between the nanoparticles and root tip cells. The biouptake of Al2O3 in particulate form led to reactive oxygen species generation, which in turn probably contributed to the induction of chromosomal aberrations.

In the present communication, we report a comparative study of Cr (VI) removal using biologically synthesized nano zero valent iron (BS-nZVI) and chemically synthesized nZVI (CS-nZVI), both immobilized in calcium alginate beads. The parameters like initial Cr (VI) concentration, nZVI concentration, and the contact time for Cr (VI) removal were optimized based on Box-Behnken design (BBD) by response surface modeling at a constant pH 7. Under the optimized conditions (concentration of nZVI = 1000 mg L(-1), contact time = ∼ 80 min, and initial concentration of Cr (VI) = 10 mg L(-1)), the Cr (VI) removal by the immobilized BS-nZVI and CS-nZVI alginate beads was 80.04 and 81.08 %, respectively. The adsorption of Cr (VI) onto the surface of alginate beads was confirmed by scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM-EDX), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) analysis. The applicability of the process using both the sorbents was successfully test medium Cr (VI) spiked environmental water samples. In order to assess the ecotoxic effects of nZVI, the decline in cell viability, generation of intracellular reactive oxygen species (ROS), cell membrane damage, and biouptake was studied at 1000 mg L(-1) concentration, with five indigenous bacterial isolates from chromium-contaminated lake sediments and their consortium.

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Cr­(VI) removal was investigated in a fixed-bed column using nanozerovalent iron-immobilized calcium alginate beads (nZVI–C–A beads) and a biofilm formed on nZVI–C–A beads. The removal studies were performed at various initial Cr­(VI) concentrations, different flow rates, and bed heights. Under optimal conditions, nZVI–C–A beads showed 91.35 ± 1.57% Cr­(VI) removal and 320.66 ± 3.87 mg/g removal capacity. For biofilm-coated nZVI–C–A beads, the removal percentage and removal capacity were found to be 97.84 ± 0.56% and 473.9 ± 4.84 mg/g, respectively. Breakthrough data were successfully described by the Thomas and Yoon–Nelson model for removal of Cr­(VI) using nZVI–C–A and a biofilm on nZVI–C–A beads. Cr­(VI) sorption on nZVI–C–A beads and biofilm-coated nZVI–C–A beads were confirmed by X-ray diffraction, energy-dispersive analysis of X-rays, and Fourier transform infrared.

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The present study deals with the toxicity assessment of two differently synthesized zero valent iron nanoparticles (nZVI, chemical and biological) as well as Fe ions on Artemia salina at three different initial concentrations of 1, 10, and 100 mg/L of these particles. The assessment was done till 96 h at time intervals of 24 h. EC value was calculated to evaluate the 50% mortality of Artemia salina at all exposure time durations. Between chemically and biologically synthesized nZVI nanoparticles, insignificant differences in the level of mortality were demonstrated. At even 24 h, Fe ion imparted complete lethality at the highest exposure concentration (100 mg/L). To understand intracellular oxidative stress because of zero valent iron nanoparticles, ROS estimation, SOD activity, GSH activity, and catalase activity was performed which demonstrated that ionic form of iron is quite lethal at high concentrations as compared with the same concentration of nZVI exposure. Lower concentrations of nZVI were more toxic as compared with the ionic form and was in order of CS-nZVI > BS-nZVI > Fe . Cell membrane damage and bio-uptake of nanoparticles were also evaluated for all three concentrations of BS-nZVI, CS-nZVI, and Fe using adult Artemia salina in marine water; both of which supported the observations made in toxicity assessment. This study can be further explored to exploit Artemia salina as a model organism and a biomarker in an nZVI prone aquatic system to detect toxic levels of these nanoparticles. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1617-1627, 2017.