Fate of geothermal mercury from Yellowstone National Park in the Madison and Missouri Rivers, USA

► About 7.0 kg/y of geothermal Hg exits Yellowstone National Park via the Madison River. ► 87% of that Hg load lost to sedimentation and volatilization in first downstream lake ► Hg concentrations in water, sediment, and trout are high upstream from lake. ► Hg concentrations in water, sediment, and fish are not elevated below lake. ► Bioaccumulation of Hg in fish correlated with total Hg in water and sediment.