Mercury is a pervasive global pollutant that cannot be destroyed. Historically, it was widely used in industrial, manufacturing and mining processes which has left a legacy of contaminated hotspots around the world. Today, mercury is most often released into the atmosphere as a by-product coal-fired power plants and small-scale artisanal mining. Once in the atmosphere, mercury can be transported globally where it contaminates ecosystems far from original sources. Humans have dramatically altered the global mercury cycle (image left) causing average mercury inputs to global ecosystems to be at least three times higher than pre-anthropogenic levels.

Atmospheric mercury is most often deposited to oceans and watersheds through precipitation like rain and snow. On land, it can accumulate in plants and soils or be washed into local streams, creeks and rivers during precipitation events. Once in bodies of water, non-pathogenic microorganisms can transform mercury into methylmercury, a highly toxic form of mercury that easily enters food webs, bioaccumulates and threatens the health of top predators – including humans. In the United States, thousands of estuaries and freshwater areas are listed as impaired by the Environmental Protection Agency (EPA) due to high mercury concentrations in fish, often resulting in fish consumption warnings.

To address this global pollutant, SERC scientists study the microbial methylation process by looking at which microorganisms are responsible for methylation, what environmental conditions facilitate methylation and what types of ecosystems are most sensitive to mercury. They continue to develop remediation tools that aim to prevent methylmercury from entering food webs in areas with contaminated sediments and soils. Understanding the microbial methylation process and developing remediation tools helps provide policy makers and managers with the necessary information to design effective controls and regulations for mercury pollution.