Researchers characterize atmospheric mercury depletion events at the Dead Sea in Israel and the atmospheric chemistry responsible for these events.

Through a National Science Foundation (NSF) grant, Drs. Daniel Obrist, DRI Associate Research Professor in the Division of Atmospheric Sciences and Menachem Luria, Professor at Hebrew University and an Adjunct Professor at DRI, headed out to the Dead Sea this summer in search of answers to important questions regarding the chemical compounds and pathways responsible for mercury oxidation.

Building on research first conducted at the Dead Sea in summer 2006, researchers are performing intensive summer and winter measurement campaigns to characterize atmospheric chemistry, and use a modeling component, to identify how reactive halogens lead to so-called Atmospheric Mercury Depletion Events (AMDE). During AMDE, relatively inert elemental mercury is converted to highly reactive oxidized mercury which leads to high atmospheric mercury depositions. Such processes are frequently occurring in the Arctic and Antarctic atmosphere during polar sunrise contributing to increased mercury levels in Arctic food supplies and native people, but they have never been characterized under temperate conditions.

Because the Dead Sea is one of the of the most saline lakes in the world, with concentrations of bromide and chloride exceeding concentration of regular ocean water by a factor of 11 and 86, it serves as a natural laboratory for the study of halogen chemistry.

“There are many open questions in regards to oxidation of mercury in the atmosphere outside of the polar atmosphere,” Obrist said. “We hope to find out about pathways that lead to AMDE in temperate areas and about the conditions needed to initiate them.”

The findings may have global implications and help researchers understand to what degree similar processes contribute to mercury deposition across the oceans of the world. First results show substantial oxidation of mercury over the Dead Sea.

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