GEOC 57 |
| George W. Luther III1, David Rickard2, Timothy F. Rozan1, and Stephen M. Theberge3. (1) College of Marine Studies, University of Delaware, Lewes, DE 19958, (2) Department of Earth Sciences, Cardiff University, Cardiff CF103YE, United Kingdom, (3) Department of Chemistry, Merrimack College, 315 Turnpike St, North Andover, MA 01845 |
| Metal complexation in oxic waters of the environment has been generally studied with three voltammetric methods - anodic stripping voltammetry, cathodic stripping voltammetry competitive ligand experiments or pseudovoltammetry. The latter gives concentration information on each actual ligand bound to the metal as well as the thermodynamic stability constant of each complex in solution whereas the other two methods give information on conditional stability constants for one complex. Sulfide at low concentrations is also present in oxic waters in addition to anoxic waters of lakes and marine basins. In this paper, we describe how sulfide binds with metals by forming soluble molecular clusters, which have higher thermodynamic stability constants than metal-organic complexes and which are kinetically inert. We present field and laboratory data using a variety of techniques (e.g.; voltammetry, UV-VIS, NMR, ESR, mass spectrometry) to show the existence of metal sulfide clusters for several metals (e.g.; Fe, Cu, Zn, Pb, Ag) with stoichiometries such as Zn4S6(H2O)42-, Cu3S3(H2O)6. These clusters display the basic structural elements found in minerals. Metal sulfide cluster formation is a metal and a sulfide detoxification process because metals and sulfide, when not bound, can be toxic to organisms. |
|
Chemistry of Metals in Terrestrial and Aquatic Systems
8:00 AM-11:30 AM, Tuesday, March 30, 2004 Marriott -- Marquis NE, Oral
Division of Geochemistry |