Mercury Bioaccumulation by Aquatic Biota in Hydroelectric Reservoirs: Review and Consideration of the Mechanisms
The mercury bioaccumulation process in man-made reservoirs is a phenomenon recently (1969) recognized in several countries such as USA, Canada, Sweden, Finland, Brazil. In many cases, no specific pollution source is identified and many occurrences of elevated Hg levels in tissues of fish have been detected in regions considered to be remote from sources of Hg. In impoundments the increase of mercury bioavailability are usually related with quality and amount of flooded vegetation, bacterial activitiy in sediments and high level of humosity of the surface waters. Dissolved organic acids, abundant in darkwater aquatic systems, increase the reactivity of all forms of mercury both present in flooded sediments and deposited from atmosphere. The recent discovery of water-soluble species of mercury in the atmosphere, usually produced by coal-wood combustion, named reactive gaseous mercury (RGM), has heightened concerns that this form of mercury can react quickly in large surface reservoirs increasing the bioavailability of the pollutant. It has also been demonstrated the capability of some organisms of methylating mercury organic complexes in their intestines.
07 May 2010 by iwlearn