Copper (Cu) Ligand Distribution Across Multiple Detection Windows in Natural Waters: Influence of pH, DOC Abundance, and Ligand Composition

Yale University, New Haven CT

Investigators

Abstract

Proposal 0838404 Abstract This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This first study to measure Cu binding ligand abundance across the full range of strength from very weak to very strong in two lakes would cover a range of pH, DOC (dissolved organic carbon) amount and composition, trophic status, and level of watershed development (both clean and contaminated sites). Chemical speciation controls a metal?s environmental behavior and biological availability in natural waters. Speciation is largely controlled in aquatic systems by metal-binding ligands that decrease the free (aquo) metal ion concentration through the formation of stable metal complexes. I hypothesize that the relationship between abundance ([CL]) and stability (K?) of naturally occurring, copper-binding, aquatic ligands follows the form [CLi]  K?i-n, and that this is caused by the relative abundance and strength of functional groups based on the elements O, N, and S. Scatter around this trend is introduced by variations in pH and amount of DOC. The relationship between CL and K? has a profound influence on the relative importance of strong and weak ligands, the concentration of free reactive copper (Cu2+), and the environmental behavior, toxicity, and bioavailability of copper. I will test these hypotheses across the full range of ligand strength (logK? from 5 to 15) with multiple detection windows (≥ 5) via a range of analytical methods. DOC composition (O, N, S), the importance of reduced S ligands, a possible DOC-CL correlation, and the influence of pH will all be measured as well. Finally, I hope to evaluate the utility of pseudopolarography for measuring Cu binding ligands in fresh waters.