Abstract

Atmospheric mercury species (gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM)), trace pollutants (O3, SO2, CO, NO, NOY, and black carbon), and meteorological parameters have been continuously measured since 2007 at an Atmospheric Mercury Network (AMNet) site that is located on the northern coast of the Gulf of Mexico in Moss Point, Mississippi. For the data that were collected between 2007 and 2018, the average concentrations and standard deviations are 1.39 ± 0.22 ng m−3 for GEM, 5.1 ± 10.2 pg m−3 for GOM, 5.9 ± 13.0 pg m−3 for PBM, and 309 ± 407 ng m−2 wk−1 for mercury wet deposition, with interannual trends of −0.009 ng m−3 yr−1 for GEM, −0.36 pg m−3 yr−1 for GOM, 0.18 pg m−3 yr−1 for PBM, and 2.8 ng m−2 wk−1 yr−1 for mercury wet deposition. The diurnal variation of GEM shows lower concentrations in the early morning due to GEM depletion, likely due to plant uptake in high humidity events and slight elevation during the day, likely due to downward mixing to the surface of higher concentrations of GEM in the air aloft. The seasonal variation of GEM shows higher levels in winter and spring and lower levels in summer and fall. Diurnal variations of both GOM and PBM show broad peaks in the afternoon likely due to the photochemical oxidation of GEM. Seasonally, PBM measurements exhibit higher levels in winter and early spring and lower levels in summer with rising levels in fall, while GOM measurements show high levels in late spring/early summer and late fall and low levels in winter. The seasonal variation of mercury wet deposition shows higher values in summer and lower values in winter, due to larger rainfall amounts in summer than in winter. As expected, anticorrelation between mercury wet deposition and the sum of GOM and PBM, but positive correlation between mercury wet deposition and rainfall were observed. Correlation among GOM, ozone, and SO2 suggests possible different GOM sources: direct emissions and photochemical oxidation of GEM, with the possible influence of boundary layer dynamics and seasonal variability. This study indicates that the monitoring site experiences are impacted from local and regional mercury sources as well as large scale mercury cycling phenomena.

Highlights

  • Mercury (Hg) is a potent neurotoxin that is damaging to the development of fetuses, infants, and young children [1]

  • High gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM) events were observed with the GOM concentration up to 256 pg m−3 in 2008 and the PBM concentration up to 970 pg m−3 in 2014

  • SO2 remained at low levels of less than 1.5 ppbv until a peak of SO2 up to 9 ppbv appeared around midnight, with a simultaneous peak of GOM up to 30 pg m−3, while there was no significant enhancement in gaseous elemental mercury (GEM) or PBM

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Summary

Introduction

Mercury (Hg) is a potent neurotoxin that is damaging to the development of fetuses, infants, and young children [1]. While Hg ubiquitously exists in the natural environment, anthropogenic activities have moved previously sequestered materials (e.g., Hg in coal and metallurgical ores) into the ecosphere and increased its bioavailability [2]. It is when mercury deposits to land and water surfaces that it becomes a potential issue. The current primary pathway of ecosystem contamination is the emissions of Hg from both natural and anthropogenic sources to the atmosphere, followed by Hg deposition. Once deposited to watersheds and receiving waters, Hg can be converted to highly toxic methylmercury, which can be incorporated into the food chain and increase with trophic levels through bioaccumulation. Consumption advisories for fish and other seafood due to mercury contamination are widespread throughout the United States and worldwide [6,7]

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