The mercury cycle

Various sources emit elemental mercury into the air, which settles into bodies of water where methylmercury, the most toxic form of mercury, is formed by bacteria in the water. In this cycle, mercury is changed from its elemental form into its ionic form as well as the organic methylmercury form. Small fish eat phytoplankton, which have accumulated methylmercury; larger fish eat smaller fish. When larger fish eat smaller fish, the methylmercury bioconcentrates in the fish that are higher on the food chain. Humans, who are highest on the food chain, eat fish and are inadvertently exposed to methylmercury in the muscle tissue of the fish.


Alt Text:  Mercury from the air settles into the soil and water via deposition and runoff. In the water, this settles on the bottom as sediment deposits in the form of methylmercury C H sub 3 H g. This is put back into the water via sediment resuspension and methylation via bioconcentration. This cycle is as follows. methylation to C H sub 3 H G to demethylation to elemental mercury H G superscript 0 to reduction to mercury salts H g superscript 2 plus back to methylation.

The elemental mercury is then put back into the air via volatization and deposition.