Cd and proton binding onto bacterial surfaces and humic and fulvic acids

摘要

Bacteria and humic and fiilvic acids strongly complex metals in natural waters. The mobility of these metals largely depends upon which of these components the metals are bound. In this study, we build a surface complexation model that describes the competition between bacteria and humic/fulvic acids for protons and Cd. We apply the model to determine the relative importance of bacteria and humic/fulvic acids in binding Cd in natural waters. In the examples presented here, and for many natural waters, Cd-humic/fulvic complexes dominate over Cd-bacterial surface complexes. However, Cd-bacterial surface complexes likely dominate in some groundwater and marine systems with low humic/fulvic acid concentrations. This model is a powerful tool for determining the relative importance of dissolved (humic/fulvic acid) versus solid (bacteria) metal-organic complexes in specific environments. This approach can be extended to incorporate competition with different and/or multiple metals and other adsorbing surfaces.