A risk assessment index for bioavailability of metals in sediments: Anzali International Wetland case study

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, CaCl₂, 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 CaCl₂, 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.