Articles | Volume 17, issue 3
Research article
 | Highlight paper
15 Feb 2017
Research article | Highlight paper |  | 15 Feb 2017

Trend of atmospheric mercury concentrations at Cape Point for 1995–2004 and since 2007

Lynwill G. Martin, Casper Labuschagne, Ernst-Günther Brunke, Andreas Weigelt, Ralf Ebinghaus, and Franz Slemr

Abstract. Long-term measurements of gaseous elemental mercury (GEM) concentrations at Cape Point, South Africa, reveal a downward trend between September 1995 and December 2005 and an upward one from March 2007 until June 2015, implying a change in trend sign between 2004 and 2007. The trend change is qualitatively consistent with the trend changes in GEM concentrations observed at Mace Head, Ireland, and in mercury wet deposition over North America, suggesting a change in worldwide mercury emissions.

Seasonally resolved trends suggest a modulation of the overall trend by regional processes. The trends in absolute terms (downward in 1995–2004 and upward in 2007–2015) are highest in austral spring (SON), coinciding with the peak in emissions from biomass burning in South America and southern Africa. The influence of trends in biomass burning is further supported by a biennial variation in GEM concentration found here and an El Niño–Southern Oscillation (ENSO) signature in GEM concentrations reported recently.

Short summary
Currently the Cape Point GAW GEM record is a very sought-after data record for international modelers and scientist alike, as the data set of 20 years represents the longest record in the Southern Hemisphere (SH). CPT was the only monitoring site on the African continent and one of eight GMOS ground-based monitoring sites located in the SH. The increasing Hg trend observed at CPT is of global importance as treaties such as the Minamata Convention on Mercury is there to combat Hg pollution.
Final-revised paper