Quantum Chemical Investigation of the Adsorption of Oxidized Mercury on Snow Surfaces

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Project Abstract

Mercury (Hg) is a heavy metal present in various chemical forms. It forms toxic methylmercury compounds that bioaccumulate up aquatic food chains, leading to elevated levels in fish, piscivorous mammals and the environment. The respective transport ranges of mercury species, atmospheric physical and chemical transformations, and interaction with Earth’s surfaces, contribute to the global cycling of toxic mercury. In essence, anthropogenic mercury emissions oxidize to gaseous Hg (II) compounds by halogens, ozone, and nitro species under ultraviolet light. The oxidized form of mercury deposit onto surface environments. Atmospheric reduction of Hg (II) competes with deposition, thereby, modifying the magnitude and pattern of Hg deposition. One possible pathway is the deposition on arctic snow surfaces. Arctic seasonal snowpack is suspected to contribute to the contamination of aquatic life during snowmelt. However, limited studies have been conducted on mercury concentrations in the polar cryosphere and the factors affecting the distribution of mercury within arctic snow are poorly understood. To root out the fate of deposited mercury, a quantum-chemical investigation was carried out using Density Functional Theory (DFT) to analyze the adsorption energies between various mercury molecules and snow clusters of differing sizes. Results shows that BrHgXO (X = Cl, Br, and I) compounds had the highest adsorption energies when oriented parallel in all snow cluster sizes. Further understanding of the fate of mercury in the Arctic environment will lead to advancements that can reduce exposure to mercury’s neurotoxic effects.

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