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

Abstract

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.

Recent decrease trend of atmospheric mercury concentrations in East China: the influence of anthropogenic emissions

“…In South Korea, the observed GEM concentration also showed a significant decrease in recent years (Kim et al, 2016). In South Africa, annual average GEM concentration at Cape Point decreased from 1.29 in 1996 to 1.19 ng m −3 in 2004 (Slemr et al, 2008) and increased from 0.93 ng m −3 in 2007 (Slemr et al, 2015) until 2016 (Martin et al, 2017). However, limited GEM monitoring sites and relative short -time spans in China restricted the view of long-term trends in atmospheric Hg concentration in this region.…”

“…The atmosphere is an important channel for global Hg transport. Once atmospheric Hg deposits to the aquatic system, it can be transformed into methylmercury (MeHg), which bioaccumulates through the food web and affects the central nervous system of human beings (Mason et al, 1995). Hg is therefore on the priority list of several international agreements and conventions dealing with environmental protection, including the Minamata Convention on Mercury.…”

A synthesis of research needs for improving the understanding of atmospheric mercury cycling

“…Limited long-term data have also been applied in assessing Hg trends in the atmosphere and the effects of emission control policies (Brown et al, 2015;Castro and Sherwell, 2015;Cole et al, 2013Cole et al, , 2014Martin et al, 2017;Steffen et al, 2005).…”

Increasing mercury trend observed at Cape Point Global Atmosphere Watch (GAW) Station from 2007 – 2015

“…In a recent study by (Martin et al, 2017) -briefly summarized here the long-term dataset collected at CPT was analyzed using The Mann-Kendal test for trend detection. ).…”

“…We report here an upward trend for mercury concentrations at CPT for the period [2007][2008][2009][2010][2011][2012][2013][2014][2015] Martin et al 2017] trends of GEM concentrations at CPT result from the trend of worldwide mercury emissions and are modulated by regional influences. Combining all this evidence, we conclude that the worldwide mercury emissions are now increasing, after a decade or two of decreasing emissions.…”