The current distribution of mercury in the environment may be substantially altered by climate change, prompting an even more urgent need to address mercury pollution at its sources. 

That conclusion was reported by scientists with the U.S. Geological Survey(USGS), who just released the results of a study conducted with researchers from Harvard University.  According to a USGS news release, the study casts a light on one previously unanticipated effect of climate change and “how interrelated many environmental issues truly are.”

Pollution sources

Small-scale artisanal gold mining, in which mercury is used to separate gold from rock deposits, has moved ahead of coal-fired power generation as the largest worldwide source of releases.  Artisanal gold mining releases mercury to the air, water, and soil.  Power plant releases are almost entirely atmospheric, but mercury in the air gets deposited to the earth’s surface.  Mercury in water is taken up by microorganisms, resulting in the formation of methylmercury, a neuro-toxin that bioaccumulates in the food chain. 

The researchers found that higher temperatures and weaker air circulation patterns caused by climate change will likely have significant impacts on the atmospheric lifetime and patterns of mercury deposition.  In most climate change scenarios, storms will be less frequent but more intense.  This will result in larger amounts of mercury being released through erosion and ending up in rivers, lakes, and oceans, say the researchers.  

Which scenario?

Current human releases of mercury into the environment total 2,000 metric tons per year.  Under the best-case scenario for curbing human releases and mitigating climate change, that number could fall to 800 metric tons per year by 2050.  If no actions are taken and business-as-usual continues, the number will likely increase to 3,500 metric tons per year by 2050. 

In 2011, the U.S. EPA issued the first-ever regulations to control mercury emissions from power plants.  However, the United States accounts for only 6 percent to 10 percent of global mercury releases. 

New treaty

During an October 9 to 11, 2013, meeting in Japan, 90 nations ratified the Minamata Convention on Mercury, a binding resolution that includes a ban on new mercury mines, the phaseout of existing ones, control measures for air emissions, and the international regulation of artisanal and small-scale gold mining.  The United States had planned to sign the treaty but did not because of the shutdown of the U.S. government. 

Information on the USGS/Harvard study