Mercury in the Environment and Water Supply




Mercury Analysis (Univ. of Alberta)













New Research in Mercury Cycle

Forest Fires:


“We have identified forest fires as a principal factor in the mercury cycle because of the ability of fire to volatilize mercury sequestered in forest floor organic material.”
“These findings, when combined, show that fire history plays an important and previously under-appreciated role in the mercury cycle in northern forests. Forest fire burning through a watershed decreases the mercury load contributed to the aquatic system in response to short- (during the fire) and long-term (years following fire) mercury losses. The decrease in mercury load apparently can persist for decades,even as the mercury content of soils gradually increases due to continued atmospheric input. Although many other factors must be considered, fires may lessen the possibility of severe mercury contamination in fish by cleansing a watershed of mercury that had been sequestered at the forest floor by decades of accumulation.”

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Photochemical Reactions:


“Photochemical reactions have long been known to affect the phase, redox state, partitioning, transport, and fate of many metals in aquatic environments. Probably no metal is more affected by exposure to sunlight (photosensitivity) in terms of its environmental behavior than Hg. Sunlight drives two important photochemical processes involving mercury: photochemical reduction and photochemical demethylation. Photochemical Hg reduction involves both redox and phase changes, from ionic Hg (II) to dissolved gaseous Hg (0). Dissolved gaseous mercury (DGM) is sparingly soluble in water, and will seek to evade from the water to the atmosphere, thereby removing Hg from the aquatic environment. Methylmercury (MeHg), the most bioaccumulative form of Hg, is also photosensitive and can undergo photochemical degradation to Hg (II), and then possibly reduced to DGM. This two step process serves two important roles, demethylation of MeHg to a less toxic form of Hg, and then possibly elimination of Hg from the aquatic ecosystem by evasion.”

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