Polymer-ligands: A novel chemical device for monitoring heavy metals in the aquatic environment?

Abstract

Major problems involved in using bio-indicators to monitor heavy metals in the marine environment include standardizing a great variety of physical and biological factors which have a significant effect on metal accumulation. The fact that different species may have different accumulation strategies for different metals, and also that the natural distribution of indicator species is limited, often prevents comparison between monitoring results in different geographic areas and hydrographic conditions. Furthermore, environmental effects on the uptake and depuration of the metals in the biological indicators are not well understood. In the present study, uptake of Cd, Pb and Zn by four polymer-ligands (i.e. Chelex® 100, Poly(4-vinylpyridine), Sephadex Sp C-25 and Amberlite IR-122) were studied. Laboratory results showed that Chelex® 100 was most effective in taking up the soluble fractions of these three metals at low ambient concentrations (0.1-10 mg l-1). Equilibrium at low concentrations was reached in about 21 days. Concentration factors after 21 days exposure ranged from 2500 to 5500, depending upon the metal species and ambient concentration. Both uptake and release of metals by Chelex are directly responsive to ambient concentrations and exposure time. Results of field transplantation of Chelex and mussels (Perna virvidis) also showed that Chelex accumulated significantly higher levels of Cd, Cr and Pb, similar levels of Cu, and a lower level of Zn than those of mussels under natural field conditions. Coefficients of variations of metal uptake were also much smaller with Chelex. The suitability of using Chelex® 100 as a novel chemical device for monitoring metal pollution in the aquatic environment is evaluated against selection criteria established for metal bioindicators.