Mercury is one of most toxic metals of global importance, which lead to the biomagnification and bioaccumulation of organomerucry via aquatic food web. Previous studies suggested that many Hg(II) compounds can be decomposed by sunlight, both in the gaseous and in the aqueous phase. Nanomolar to millimolar levels of thiols has been reported in both seawater and freshwater systems. Studies have suggested that strong natural ligands in low concentrations and with high conditional stability constants, possibly sulfides and thiols, could be primarily responsible for dissolved mercury complexation in estuarine waters. However, no experimental study has been performed on the photolytical behavior of Hg(II) with 3-mercaptopropionic acid detected in natural waters. We hereby present the first kinetic and product study on the photochemistry of oxidized mercury species with 3-mercaptoproponic acid at near environmental conditions. The kinetic data were obtained using ultraviolet-visible spectrometry (UV-VIS). The reaction products were analyzed by cold vapor atomic fluorescence spectrometry (CVAFS) and high resolution transmission electron microscopy coupled with energy dispersive spectrometer (HRTEM-EDS). Our results indicated that the aqueous mercaptopropionic acid (MPA) may react with Hg(II) to form 1:1 and 2:1 coordination complexes. The Hg(MCA)22- complex may be photo-stable, yet, the Hg(MCA) complex may undergo photochemical reactions to form elemental mercury and metacinnabar (β-HgS). Our future work and its potential environmental implication will be discussed.

Aquatic photochemical reaction of divalent mercury with 3-mercaptopropionic acid and its environmental implications

255th National Meeting (2018)

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