Atmospheric mercury in the Southern Hemisphere – Part 1: Trend and inter-annual variations in atmospheric mercury at Cape Point, South Africa, in 2007–2017, and on Amsterdam Island in 2012–2017

Franz Slemr,Philippe Garat,Hélène Angot,Aurélien Dommergue,Michel Ramonet,Casper Labuschagne,Johannes Bieser,Lynwill Martin,Olivier Magand,Thumeka Mkololo

doi:10.5194/acp-20-7683-2020

Abstract

Abstract. The Minamata Convention on Mercury (Hg) entered into force in 2017, committing its 116 parties (as of January 2019) to curb anthropogenic emissions. Monitoring of atmospheric concentrations and trends is an important part of the effectiveness evaluation of the convention. A few years ago (in 2017) we reported an increasing trend in atmospheric Hg concentrations at the Cape Point Global Atmosphere Watch (GAW) station in South Africa (34.3535∘ S, 18.4897∘ E) for the 2007–2015 period. With 2 more years of measurements at Cape Point and the 2012–2017 data from Amsterdam Island (37.7983∘ S, 77.5378∘ E) in the remote southern Indian Ocean, a more complex picture emerges: at Cape Point the upward trend for the 2007–2017 period is still significant, but no trend or a slightly downward trend was detected for the period 2012–2017 at both Cape Point and Amsterdam Island. The upward trend at Cape Point is driven mainly by the Hg concentration minimum in 2009 and maxima in 2014 and 2012. Using ancillary data on 222Rn, CO, O3, CO2, and CH4 from Cape Point and Amsterdam Island, the possible reasons for the trend and its change are investigated. In a companion paper this analysis is extended for the Cape Point station by calculations of source and sink regions using backward-trajectory analysis.

Highlights

Mercury (Hg) is an environmental toxicant emitted by both natural and anthropogenic sources – the latter regulated by the Minamata Convention
A few years ago, we reported an upward trend in atmospheric mercury concentrations at the Cape Point Global Atmosphere Watch (GAW) station at Cape Point (CPT; 34.3535◦ S, 18.4897◦ E) in South Africa for the 2007–2015 period (Martin et al, 2017)
Downward trends in atmospheric mercury concentrations and in mercury wet deposition have been reported for many sites in the Northern Hemisphere (Temme et al, 2007; Cole et al, 2014; Steffen et al, 2015; Weigelt et al, 2015; Weiss-Penzias et al, 2016; Marumoto et al, 2019), but Cape Point has been the only station in the Southern Hemisphere with a long-enough mercury concentration record to Published by Copernicus Publications on behalf of the European Geosciences Union

Summary

Introduction

Mercury (Hg) is an environmental toxicant emitted by both natural and anthropogenic sources – the latter regulated by the Minamata Convention. This convention, which entered into force in August 2017, requires periodic effectiveness evaluation (Article 22) to ensure that it meets its objectives. This evaluation will be based on a combination of Hg monitoring data, including levels of Hg and Hg compounds in air, biota, and humans. Downward trends in atmospheric mercury concentrations and in mercury wet deposition have been reported for many sites in the Northern Hemisphere (Temme et al, 2007; Cole et al, 2014; Steffen et al, 2015; Weigelt et al, 2015; Weiss-Penzias et al, 2016; Marumoto et al, 2019), but Cape Point has been the only station in the Southern Hemisphere with a long-enough mercury concentration record to Published by Copernicus Publications on behalf of the European Geosciences Union

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Results

Conclusion