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Abstract Title: Event-based atmospheric precipitation uncovers significant even/odd-Hg isotopes anomalies associated with the circumpolar vortex
Presenter Name: Shengliu Yuan
Company/Institution: Department of Chemistry, Trent University
Session: Atmospheric Hg cycling: Source and Emissions
Day and Session: Wednesday 27th July - Session Three
Start Time: 14:00 UTC
Co-Authors: Shengliu Yuan,Jiubin Chen,Holger Hintelmann

Abstract Information :

Hg in precipitation presumably integrates the properties of Hg present in the upper atmosphere (or free atmosphere) and the atmospheric boundary layer (ABL) and could provide insights into the deposition of atmospheric Hg. The determination of even-MIF (?200Hg) in atmospheric samples adds another intriguing feature to the Hg isotope system. Despite our lack of sufficient experimental verification and momentary absence of a valid mechanism to explain its occurrence, it could be instrumental in understanding the cycle and deposition of atmospheric Hg. In contrast to slightly positive ?200Hg (< 0.30?) values frequently observed in most atmospheric samples, significant ?200Hg (up to 1.24?) in precipitation from Peterborough (Ontario, Canada) stands out and adds to the mystery of the origin of even-MIF.
Here, we report a systematic analysis of rainfall and snowfall samples collected during cold weather in winter. Dissolved and particulate Hg both displayed large variations of odd-MIF (from -0.93? to 2.02? for ?199Hg), whereby the negative odd-MIF in particulate Hg is likely a result of long-range transport of arctic atmospheric Hg(II). Dissolved Hg revealed significant even-MIF (from 0.25? to 1.19? for ?200Hg) and a negative relationship between ?200Hg and ?204Hg, which provide further evidence for the previously proposed model of ?200Hg formation developed by Chen et al (2012). Opposing odd-MIF and even-MIF trends were detected in sequentially collected precipitation samples, which further suggests different sources for both ?199Hg and ?200Hg. Particularly, the high ?200Hg values may highlight the potential source of stratospheric Hg during polar vortex periods. The new ?200Hg data for particulate Hg add to existing information on atmospheric Hg(II) worldwide, which suggests a global distribution of even-MIF in the atmosphere, and further constrains the model of atmospheric Hg deposition.



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