Abstract

High mercury wet deposition in southeastern United States has been noticed for many years. Previous studies came up with a theory that it was associated with high-altitude divalent mercury scavenged by convective precipitation. Given the coarse resolution of previous models (e.g. GEOS-Chem), this theory is still not fully tested. Here we employed a newly developed WRF-GEOS-Chem (WRF-GC) model implemented with mercury simulation. We conduct extensive model benchmarking by comparing WRF-GC with different resolutions (from 50 km to 25 km) to GEOS-Chem output (4° × 5°) and data from Mercury Deposition Network (MDN) in July–September 2013. The comparison of mercury wet deposition from two models both present high mercury wet deposition in southeastern United States. We divided simulation results by heights, different types of precipitation and combination of these two variations together and find most of mercury wet deposition concentrates on higher space and caused by convective precipitation. Therefore, we conclude that it is the deep convection caused enhanced mercury wet deposition in the southeastern United States.

Highlights

  • We develop a new simulation capacity (WRF-GC-Hg v1.0) for atmospheric Hg emission, transport, chemistry, and 65 deposition based on the WRF-GC v1.0, which is fully described by Lin et al, 2020 and Feng et al, 2021

  • The average Hg0 concentrations are 1.25±0.22 ng m-3 for the eight sites in the southeast US, while both Goddard Earth Observation System (GEOS)-Chem (1.27±0.06 ng m-3) and WRF-GC (1.55±0.20 ng m-3) models agree with the observations relatively well

  • The WRF-GC model simulates more elevated Hg0 concentrations in the Ohio River Valley regions than the GEOS-Chem, by which the 160 coarse resolution smoothens out the higher anthropogenic emissions from mainly utility coal burning (Zhang et al, 2012)

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Summary

Introduction

Mercury (Hg) is one of the most toxic heavy metals in our environment and undergoes long-range transport (Ariya et al, 2015). It undergoes three major forms in the atmosphere: gaseous elemental mercury (GEM), gaseous oxidized mercury 30 (GOM) and particle-bound mercury (PBM). GEM has extremely low water solubility with a relatively long (~0.5-1 year) residence time in the atmosphere. GEM is slowly oxidized to GOM in the atmosphere initialized by bromine atoms (Holmes et al, 2010), especially in the high-altitudes due to low temperature (Lyman and Jaffe, 2012). Discussion started: 6 January 2022 c Author(s) 2022.

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