Behavior, toxicity and diffusive flux of metals in a sediment core and pore-water from Anzali wetland

Concentrations of metals along with pH, potential redox (Eh), total dissolved solid (TDS), electrical conductivity (EC) and salinity were measured for sediments of different layers, pore and surface water in the Anzali wetland. Also, the diffusive flux of metals was calculated ad compared with the values in other aquatic bodies. The abundance of metals in sediments was Al > Fe > Ca > Ti > Mn > Zn > V > Cr > Ni > Cu > Pb > Co > As > Mo > Ag > Cd, while the pore-water results indicated a different concentration profile: Ca > Mn > Fe > Al > V > Mo > As > Ni > Cu > Co. Anzali wetland is classified within a high ecological risk. Pore-water toxicity test showed it is in non-polluted condition. Eh-pH diagrams showed that all species of elements are in a stable state in surface and pore-waters. However, Mn and Co (in some layers) are in soluble form and free ions and thus are bioavailable to the organisms. V and As are also present in the form of hydrogen compounds and Ni in the form of hydroxides, therefore, they are toxic to aquatic animals due to their solubility and ionic forms. Diffusive fluxes for As, Al, Fe, Ca, Cu, Mn, Mo, Ni and V are 0.43, 1.80, 48.52, 43,147.50, 0.12, 1.47, 0.15, 1.28, 0.21 mu g/m(2)/day, respectively. Cluster analysis showed that in a solid phase of sediments, elements such as Cr, As and Ti are of petroleum and terrestrial origin. In pore-waters, Cu is of petroleum and biological origin, and Mo, As, Cu and Co are controlled by pH.

Automated summary

This study measured and analyzed the concentrations of metals and other environmental factors in sediments and water in the Anzali wetland. The results showed that the wetland is classified as having a high ecological risk, but the pore-water was found to be non-polluted. It was also observed that certain metals are present in a soluble form and are toxic to aquatic animals.