Why are we so concerned about mercury in the environment ?
♦ Released ♦ Volatile ♦ Travels ♦ Reactive ♦ Methylmercury
♦ Sulfur role
♦ Fertilizers ♦ Run-off ♦ Food chain
♦ Fish ♦ TOXIC !
Mercury (Hg) is a metallic element that is toxic to cells and life. Mercury poisoning (also known as hydrargyria or mercurialism) is a disease caused by exposure to mercury or its compounds. The consumption of fish is by far the most significant source of ingestion-related mercury exposure in humans and animals, although plants and livestock also contain mercury due to bioaccumulation of mercury from soil, water and atmosphere.
Mercury is liquid at ambient temperatures and volatilizes (evaporates) easily. In vapor state it can travel easily in the atmosphere. Eventually scrubbed by rain it is deposited in the environment (soil, water).
Mercury is very reactive and compounds of mercury such as Methylmercury (MeHg) tend to be much more toxic than the element itself and it is the major source of organic mercury for individuals.
Mercury and MeHg from bacteria and plants bioaccumulate throughout the food chain - humans could be exposed to high levels of mercury from food - particularly fish. Toxic effects include damage to the brain, kidney, and lungs - eventually leading to death. Common symptoms of mercury poisoning include peripheral neuropathy (presenting as paresthesia or itching, burning or pain), skin discoloration (pink cheeks, fingertips and toes), swelling, and desquamation (shedding of skin).
Human-generated sources such as coal plants emit approximately half of atmospheric mercury, with natural sources such as volcanoes responsible for the remainder. An estimated 2/3 of human-generated mercury comes from stationary combustion, mostly of coal. Other important human-generated sources include gold production, non-ferrous metal production, cement production, waste disposal, human crematoria, caustic soda production, pig iron and steel production, mercury production (mostly for batteries), and biomass (forests !) burning.
Elevated sulfur-compound levels in stagnant water bodies promote MeHg synthesis through bacterial action. From this level, Hg bioaccumulates in higher and higher organisms throughout the food chain.
Dr. Naja's slide presentation highlights the basis of Mercury occurence - and threat - in the Everglades.
Courtesy of the Everglades Foundation
Obviously, due to the globe-wide releases of mercury and its deposition from the atmosphere, the control of mercury very much depends on locally controling mainly the sulfur compounds in sensitive (aqueous) environments such as Florida Everglades where fishing represents a large and ubiquitous activity. Follow up on:
"The 3rd Workshop on Mercury and Sulfur in So-Florida Wetlands" (June 21-22, 2011 at SFWMD, West Palm Beach, FL).
Some Press and Media about Mercury in the Everglades