HR: 16:45h
AN: B52F-04 INVITED     [PDF]
TI: Determination of Strong Metal Ligands (S(II-))in Natural Waters
AU: * Kramer, J
EM: kramer@mcmaster.ca
AF: McMaster University, School of Geography/Geology, Hamilton, ON L8S 4K1 Canada
AU: Smith, D S
AF: Wilfrid Laurier University, Dept. of Chemistry, Waterloo, ON N2L 3C5
AU: Bell, R A
AF: McMaster University, Deot. of Chemistry, Hamilton, ON L8S 4M1 Canada
AU: Ernste, M
AF: McMaster University, Deot. of Chemistry, Hamilton, ON L8S 4M1 Canada
AB: Reduced sulfide (S(II-)) ligands have been measured in oxic freshwaters at 1-100s nM. "Group B" metals, such as Ag(I), Hg(II), Cu(I) and Pb(II) bind strongly to S(II-) ligands. Their role in aqueous metal speciation and suppression of metal toxicity make S(II-) ligands an important analytical challenge. S(II-) is probably stabilized in oxic environments as metal-sulfide (M-S) clusters within natural organic matter (NOM). S(II-) species are measured by Cr(II) reduction of M-S, acid reaction, purge and trap to capture H2S and measurement as the methylene diamine complex (CRS). But CRS may also detect other sulfur species. Silver is an excellent probe metal for determination of strong ligand sites(SLS)in NOM. A competitive ligand method, using Ag(I), is demonstrated. The bound Ag-ligand and the "free" silver ion concentration are measured during the titration. The total strong ligand (Lt) is determined by a Grans' approach. These values are used to determine the (Lt) and the conditional binding constant, K'. Measured Lt concentrations match CRS concentrations, and conditional stability constants for a 1:1 M-L stoichiometry range from log K'= 11+ to 13, consistent with known Ag-S(II-) values. Furthermore SLS and Lt correlate with water-effect ratios (WERs) for silver
DE: 1045 Low-temperature geochemistry
DE: 1065 Trace elements (3670)
DE: 1806 Chemistry of fresh water
DE: 4809 Colloids
SC: Biogeosciences [B]
MN: 2003 Fall Meeting