Mercury
Each spring, when sunlight returns to the Arctic, it also triggers chemical reactions that release mercury from the atmosphere. A group of scientists is finding that this mercury is falling into arctic lakes but the sun also changes the mercury into a form that fish don't pick up.
Mercury enters the atmosphere in natural ways as Earth's crust degasses, and from the burning of fossil fuels, especially coal. The toxic element often swirls in the air for about a year until it falls out with the help of rain, snow, or dust particles. Mercury can find its way to the Arctic from across the globe; a coal fire in Ireland may release mercury that ends up in Toolik Lake on Alaska's north slope.
Mercury in the atmosphere falls into lakes and rivers worldwide. Mercury then settles into lake sediments, where sulphate-reducing bacteria gobble it up and convert it to methylmercury, the form living creatures can absorb. Plankton in the lakes take up the methylmercury, larger plankton eat them, small fish eat the plankton, predators eat those fish, and larger animals like bears and even humans catch and eat the fish and get dosed with methylmercury. Mercury Policy Link.
March 27, 2006 6:37 AM | Category: Chemicals