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A new bioavailability/bioaccessibility risk assessment index (BRAI) was used to assess heavy metals' (Cu, Cr, Zn, Pb, Ni, Cd) bioavailability/bioaccessibility of the aquatic sediments of Anzali International Wetland. This wetland, registered under the Ramsar Convention, is located along the southwestern part of the Caspian Sea coast. Heavy metal concentrations in the surface sediments of Anzali wetland were determined. Four single extraction tests (with, respectively, CaCl, ammonium acetate, EDTA and glycine as extractants) were conducted to assess both the metal bioavailability and the human bioaccessibility of 15 surface sediment samples from the study area. In the different single extraction tests, higher extraction of Cd and Pb was observed than for the other metals under study. The results of the tests revealed that 21.3, 36.4, 57.3, and 70 % of Cd were extracted by CaCl, ammonium acetate, EDTA and glycine, respectively. When the new BRAI index was applied, the results showed high bioavailability/bioaccessibility of heavy metals in the surface sediments of the study area. [ABSTRACT FROM AUTHOR]

The co-precipitation method was used to synthesize nano-magnetic adsorbent MnFe 2 O 4 (nMFO), characterized through XRD, SEM, EDS, and BET techniques. The synthesized nMFO was used for hexavalent and trivalent chromium ions elimination from the aqueous phase. The optimum pH for the adsorption of Cr (VI) and Cr (III) was determined as 2 and 5, respectively. The chromium ions adsorption behavior was well interpreted through the pseudo-second order kinetics model. Furthermore, isotherm studies were conducted, and the obtained results indicated that Langmuir isotherm model could well justify the chromium ions adsorption process. Quick removal (less than 10 min) of both chromium ions and high removal efficiency were occurred using nMFO. The utmost adsorption capacity of trivalent and hexavalent chromium ions were determined as 39.6 and 34.84 mg g -1 , respectively. Thermodynamic studies on chromium adsorption revealed positive value for ΔH and negative value for ΔG, representing that chromium ions adsorption was an endothermic and spontaneous process. The multilinearity in the graphs of chromium ions adsorption was observed using intra-particle diffusion model. In this regard, the external mass transfer of chromium ions on synthesized nanoparticles was the important and controlling step in the adsorption process., (Copyright © 2020 Elsevier Ltd. All rights reserved.)