Biodisponibilidade de Metilmercúrio, Zinco e Cobre em Distintas Fra es Granulométricas de Solo Contaminado Utilizando Oligoquetas da Espécie Eisenia andrei.

The scientifi c community has been concerned about heavy metals contamination and their effects on human health andthe environment. Rural areas of Descoberto municipality, southern Minas Gerais State, were submitted to gold extraction usingrudimentary techniques of mineral processing. In 2002, local population detected metallic mercury presence on soil surface, andin 2005 Environmental Foundation of Minas Gerais State (FEAM) delimited a critical contamination area. This works proposesbioavailability assessment of mercury (Hg), zinc (Zn) and copper (Cu) in distinct grain sizes of a soil sample collected into the criticalarea delimited by FEAM. Granulometric analysis was done using nylon sieves of 200 # (75 μm), 100 # (150 μm), 80 # (180 μm), 42# (350 μm) and 10 # (1700 μm). Mineralogical characterization was executed using X-ray difratometry. Earthworms acute toxicity testfollows ASTM (2004) procedures. Metals determination in soil and earthworms was performed using Atomic Absorption technique.Methylmercury (MeHg) quantifi cation was made using Gas Chromatography. Grain sizes analysis showed sand predominance. Totalchemical analysis demonstrated a very high level of contamination of Hg, Zn and Cu, confi rming previous studies executed by FEAM.It was observed an affi nity between grain size and metals concentrations, which is related to increasing specifi c surface. Acute toxicitytest denoted that earthworms absorbed Hg and Cu from the soil, and Zn uptake involved absorption and bioaccumulation for smallergrain sizes. Total chemical analysis of metals in earthworms revealed that fi ner granulometric intervals showed higher levels of heavymetals bioavaibility. MeHg quantifi cation denoted concentrations about 21 a 33% of total Hg. In conclusion, it is expected that theseresults can give an important support for future decisions in medical geology programs and in environmental control actions.