The Ecotoxicity of Nanoparticles Co2O3 and Fe2O3 on Daphnia magna in Freshwater

Despite all advantages of nanoparticles and their widespread utilization, the potential contamination caused by nanoparticles should be considered. They may enter aquatic media and cause the environmental concerns and adverse effects on living organisms, especially the aquatic animals. Iron oxide and cobalt oxide NPs are among the most widely used metal nanoparticles by the useful properties in wastewater treatment, biomedicine, sensors. There is the possibility to enter the environment and cause toxicity and interaction with ecosystem organisms. This study investigates the acute toxicity of iron oxide and cobalt oxide NPs on Daphnia magna which is the source of food chain after phytoplankton in aquatic ecosystems and the biological indicator in bioassay tests. Using OECD method (202), the different concentrations of Fe 2 O 3 and Co 2 O 3 nanoparticles were exposed to D. magna in the periods of 24, 48, 72, and 96 h at the temperature of 20–24°C. LC 50 of iron oxide and cobalt oxide NPs were analyzed by Probit method for the determination of D. magna proportion in each solution following 96 h and respectively the following amounts of 163.21 and 121.04 mg L –1 were observed, affected by concentration and time ( p < 0.05). According to aquatic hazard classification of USEPA, nanoparticles with LC 50 value above 100 mg L –1 have lower acute toxicity for aquatic animals. Still, they may have a more negative impact on ecosystems and aquatic organisms in long run. However, they were less toxic than other nanoparticles, but with a certain trend in different environments and combined with other substances. The results of the study showed the lower rate of toxic effect in nano-iron oxide compared to nano-cobalt oxide in D. magna. Finally, proposed two new values for SAR and SAFE Coefficients.