MERCURY IN ENVIRONMENTAL-SAMPLES FROM A WATERBODY CONTAMINATED BY GOLD MINING IN COLOMBIA, SOUTH-AMERICA

Environmental samples from a marsh, which receives mercury discharges from a gold mine in Colombia (South America), were evaluated for total mercury content. Mercury concentrations were analyzed in sediments, m acrophytes and fish species from different trophic levels. The Mean me rcury levels in sediments oscillated between 140 and 355 mu g/kg where as in the macrophyte Eichornia crassipes levels were between 219 and 2 77 mu g/kg with practically no interseasonal variations. The mercury c ontent in the muscle of fish varied depending on the position in the t rophic chain and the feeding habits of each species, oscillating betwe en non-detectable (< 7.4 mu g/kg) and 1084 mu g/kg. Seasonal variation s were only observed in fish species whose habitats are mostly the bot tom sediment. The presence of mercury in some fish appeared to be the result of bioaccumulation rather than a biomagnification processes. Th is was clearly evidenced in the detritivorous species Triportheus magd alenae which obtain their food within the sediments and whose mercury concentrations were significantly higher when compared to the other sp ecies including carnivorous. The relatively low mercury concentrations found in fish may be due to both the dispersion of the contaminant on ce it reaches the waterbody and the migrational characteristics of the fish species. (C) 1998 Elsevier Science B.V. All rights reserved.