Heavy metal distribution trends in sediments from the Beagle Channel, Tierra del Fuego (Argentina): results of the 1993-2003 decade

AMÍN, O.; GIL, M.; WILLERS, V.; BOTTÉ, S.E.; DEL BLANCO, L.; CHIARELLO, M.N.; MARCOVECCHIO, J.E.

Buzios/Rio de Janeiro, Brasil

Simposio; 4th International SYMPOSIUM ENVIRONMENTAL GEOCHEMISTRY IN TROPICAL COUNTRIES; 2004

Departamento de Geoquímica da Universidade Federal Fluminense

During the last two decades, bays close Ushuaia city (54º48´ S, 68º19´ W, Tierra del Fuego, Argentina) have been receiving inputs of some pollutants from urban and industrial waste since the increase population, establish electronics factories and ship traffic in the area.  Then, a monitoring programme directed to assess several heavy metal (Cd, Pb, Cu, Zn, Fe) concentrations within surface littoral sediments has been developed since the ´90s. The studied metal distribution trends have been identified during this period, as well as their corresponding potential sources. Metals were analyzed in the fine fraction (< 62µm), in order to reduce grain size effects. Extraccions were performed in order to determine the most bioavailable fraction using AAS after internationally standardized protocols. Cd has shown an homogeneous distribution along the whole period, with values oscillating between nd and 1 µg.g-1, with exceptional records close to 6.4 µg.g-1 (at the Industrial Zone in 1996). Pb distribution has seemed to be more variable, with levels ranging between nd and 129 µg.g-1 (as recorded in sediments collected next to the “Orion” oil marine gas station  in 1993 and 1996); in a similar way, Cu has presented values oscillating between 1 and 73 µg.g-1, with the highest one also close to the “Orion” area. Zn has presented a more homogeneous distribution, with higher values linked with the two above mentioned potential source areas (Industrial Zone and “Orion” area), and reaching up to levels of 341 µg.g-1, and agreeding with the distribution as observed for Fe, which has shown values up to 160 mg.g-1.  Metal levels have been standardized against Fe concentration (because of its ability as a natural reference element) in order to discriminate natural contents of anthropogenically enriched ones. This way, Cd has shown a throughout natural distribution, with only a couple of eventual biased points. Unlike this, Pb, Cu and Zn have presented a larger scatter distribution model, which pointed out the occurrence of anthropogenic inputs of these elements.  The corresponding time-trend series were discussed within this framework, highligthing the use of this kind of evaluation to assess the environmental quality of coastal systems like that here reported.