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This work presents quality control results on the mercury concentrations in different environmental (river sediments, forest soils, river suspended matter and fish) and human samples from the lower Madeira River, Amazon sampled between 2001 and 2003, about 15-20 years after the nearly cessation of gold mining activities in the region, which reached its peak in the late 1980s. The study aimed to compare mercury concentrations in these environmental samples with those reported by other authors during the gold rush of the Madeira River Basin. Today, in the Madeira River the releases of mercury register a sudden reduction due the gold price fall in the international trade. However, about 100 t of Hg were released to the atmosphere and to aquatic systems in the region during the gold rush. The present survey shows that notwithstanding the reduction of Hg emissions to the Madeira River Basin from gold mining proper, concentrations in fish and humans are similar to those measured during the gold rush. Reduction in Hg concentrations is restricted to areas close to old point sources and only for abiotic compartments (air and sediments). Remobilization of Hg from bottom sediments plus re-emission from soils due to land use changes are probably responsible for keeping high Hg concentrations in biological samples.

Evaluation of Hg in urban air is a quite complex and expensive task since conventional sampling systems are fragile and need special attention if long-term sampling is needed. Tillandsia usneoides, a Bromeliacea, is an epiphyte that captures all its nutrients from the atmosphere, and concomitantly accumulates heavy metals, among them mercury. Its morphology, with millimetric dimensions of the leaves and no roots, makes it ideal for handling and preparation of transplanting systems and due to its high relation between surface area and mass, has a high efficiency for Hg accumulation. One hundred systems of two baskets each with T. usneoides were distributed through Alta Floresta city}MT and recovered after an exposure of 15 and 45 days during the dry season August)September, . . . 1995 and also repeated during the rainy season February)March, 1996 . Each compartment basket contained 5 g of plants previously collected in a clean area. Only the younger parts were selected for transplantation experiments. Systems were hung at 2)20 m height in open areas, close to and in the surroundings of the gold shops as well as in control areas. Relative occupational exposure was also evaluated with systems installed inside gold dealer shops. Concentrations of Hg in the exposed plants were remarkably high in the shops, reaching values up to 26 ppm parts . per million or 300 times higher than in the control plants. Q 1998 Elsevier Science B.V.

Metallic mercury used in gold prospecting is being dispersed over Amazon ecosystems through atmospheric emissions as well as directly to aquatic systems. Total mercury concentrations in the more representative environmental (air, soil, bottom sediments, fishes and plants) and human (hair and urine) indicators, collected in the last 7 years in different goldmining areas (garimpos) are presented and discussed. Critical exposure situations, pathways, areas and human groups are indicated. The goldminers (garimpeiros) that manipulate a major part of the Hg are not the critical group either from exposure to metallic mercury (Hg0) by inhalation or exposure to methylmercury by ingestion of contaminated fish. Results obtained from air and urine sampling show that people working in gold dealers shops are the critical group concerning Hg0 risk, while riverine communities are the risk group with respect to methylmercury.

Mercury is being released in the Amazon in an abusive way due to goldmining activities. The Tapajós river basin was the first to be intensively exploited in the modern Amazon gold rush. Fish and hair samples as the best indicators of human methylmercury contamination were investigated in the main cities and villages along the Tapajós river basin. The upper basin has typical fish fauna with much larger carnivorous fish with higher mercury levels reaching an average value of 0.69 microgram.g-1 wet wt. in 43 fish. This was accompanied by high levels in hair of the human population living in the same area. The maximum hair value reach 151 micrograms.g-1 dry wt. with two villages presenting an average value close to 25 micrograms.g-1 dry wt. An analytical laboratory intercalibration exercise was performed between Japanese and Brazilian laboratories for total mercury analysis. Critical fish, areas, and more exposed human groups are identified.

Total mercury concentrations in water, sediments and fish from the gold-mining areas of Brazil, especially the Amazon region, are presented. Mercury concentrations were variable among rivers, with the highest values found in samples from tributary forest rivers. Concentrations in water samples varied between 0.1 and 8.6 micrograms l-1, while in bottom sediments they reached 19,800 micrograms kg-1. Concentrations in edible parts of locally consumed fish reached up to 2700 micrograms kg-1 wet wt, surpassing by almost five times the Brazilian advisory level for human consumption.