A146-0006
Is oxidation of atmospheric mercury controlled by different mechanisms in the polluted continental boundary layer vs. remote marine boundary layer?

Monday, 14 December 2020
Poster
Maor Gabay, Hebrew University of Jerusalem, Soil & Water Sciences, Jerusalem, Israel, Shira Raveh-Rubin, Weizmann Institute of Science, Rehovot, Israel, Mordechai Peleg, Hebrew University of Jerusalem, Institute of Earth Sciences, Jerusalem, Israel, Erick Fredj, The Jerusalem College of Technology, Jerusalem, Israel and Eran Tas, Hebrew University of Jerusalem, Soil and Water Sciences, Rehovot, Israel
Abstract:
Deposition of atmospheric mercury is of global concern, primarily due to health effects associated with efficient bioaccumulation of mercury in marine food webs. Although oxidation of gaseous elementary mercury (GEM), the major fraction of atmospheric mercury, is a critical stage in regulating atmospheric mercury deposition efficiency, this oxidation is currently not well-characterized, limiting modeling-based assessments of mercury in the environment.

Based on a previous study, we hypothesized that the oxidation of GEM is predominantly controlled by multistep bromine- and chlorine-induced oxidation (MBCO) in the remote marine boundary layer (RMBL), and by photochemical smog oxidants, primarily ozone (O3) and hydroxyl radical (OH), in the polluted continental boundary layer (PCBL). To test this hypothesis, we used the following analyses: (i) application of a newly developed criterion to evaluate the gaseous oxidized mercury (GOM)–O3 association based on previous studies in the RMBL and PCBL; (ii) measurement-based box simulations of GEM oxidation in the RMBL and at a PCBL site; and (iii) measurement-based analysis of photochemical oxidation vs. other processes which potentially influence GOM.

Our model simulations indicated that the MBCO mechanism can reproduce GOM levels in the RMBL, but not in the PCBL. Our data analysis suggested the important role of photochemical smog oxidants in GEM oxidation in the PCBL, potentially masked by the effect of relative humidity and entrainment of free tropospheric air.

Overall, our study indicates that photochemical air pollution plays a key role in atmospheric mercury oxidation in the polluted boundary layer, probably via heterogeneous processes.

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