Mercury (Hg) is a global pollutant that is released into the environment through natural processes and anthropogenic activities. Large-scale reactive transport modeling and simulations based on thermodynamic stability constants (log K) are used to understand chemical speciation, transport, and availability of Hg in the environment. Aqueous binding affinities of Hg for various ligands largely control chemical speciation and availability of Hg in the environment. However, experimental log K values are not available for many relevant complexes and for others can span ranges in excess of 10 log units. We have developed a rapid and reliable quantum chemical approach for calculating stability constants of Hg complexes (HgL, HgL2, and LHgL’) that contain one or more S, N, or O- donor functional groups in the ligand molecules. Density functional theory in combination with a modified SMD solvent model, which we refer to as SMDlogK, was used to calculate the log K values. A mean unsigned error of 1.4 log units was obtained for a benchmark set of 37 Hg complexes (Figure 1). The SMDlogK approach can be readily extended to include other environmentally and biologically relevant metals and ligands. This approach can be used to provide a more complete and consistent data for use in Hg biogeochemical speciation and transport modeling.

Computational approach for quantifying the interactions of mercury with low molecular weight organic compounds

2019 Spring National Meeting

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