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The concentration and bioavailability of Ni, Cu, Cd, Zn, and Pb in the sediments and leaves of grey mangrove, Avicennia marina, were studied throughout Sirik Azini creek (Iran) with a view to determine heavy metals bioavailability, and two methods were used. Results show that Zn and Ni had the highest concentrations in the sediments, while Cd and Cu were found to have the lowest concentrations in the sediments. Compared to the mean concentrations of heavy metals in sedimentary rock (shales), Zn and Cu showed lower concentration, possibly indicating that the origin of these heavy metals is natural. A geo-accumulation index (Igeo) was used to determine the degree of contamination in the sediments. Igeo values for Zn, Cu, Pb, and Ni showed that there is no pollution from these metals in the study area. As heavy metal concentrations in leaves were higher than the bioavailable fraction of metals in sediments, it follows that bioconcentration factors (leaf/bioavailable sediment) for some metals were higher than 1.

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In recent years, development of nanotechnology as well as the toxicity potential of nanomaterials on the environment has received much attention. In order to assess the potential toxic impact of nanoparticles on aquatic environments, we used three kinds of nanoparticles, including titanium dioxide (TiO2), copper oxide (CuO), and zinc oxide (ZnO) on an aquatic model species, Daphnia magna. In fact, Daphnia magna was exposed to different concentrations for 24, 48, 72, and 96 h at 20-25°C. All the important water quality parameters, such as temperature, pH, and dissolved oxygen (DO) were controlled to meet the standard requirements during the experiment. The LC50 values for 24, 48, 72, and 96 h were estimated statistically using Probit methods. The LC50 48 h values for TiO2, CuO, and ZnO were 171.88 mg/l, 6.62 mg/l, and 3.23 mg/l, respectively.