Wanderley Rodrigues Bastos

Mercury and methylmercury in fish and human hair from the Tapajós river basin, Brazil

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.

Mercury concentrations in inland waters of gold-mining areas in Rondônia, Brazil

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.

An assessment of Hg pollution in different goldmining areas, Amazon Brazil

Abstract 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 dispersal in water, sediments and aquatic biota of a gold mining tailing deposit drainage in pocone, Brazil

In the Pocone district, Brazil, Hg distribution was studied in a small watershed which drains tailings from a 10 yr old gold mining operation. Heavy regional rains are responsible for continuous weathering, thereby making it possible to transport Hg into the ecologically important Pantanal area. Mercury concentrations in creek sediments range from < 0.02 to 0.18 mg. kg−1. The highest concentrations occur close to the tailings deposit. Mercury concentrations in the water were always below the detection limit of the analytical method used (<0.04 µg. L−1). Suspended matter samples collected before, during and after a storm, showed a Hg peak value of 0.61 mg kg−1. about 30 min after the event. Dissolved Hg concentration still fell below the detection limit. Among the biota, molluscs accumulated moderately high concentrations of Hg, while macrophytes and fish did not. Mercury concentrations in molluscs were dependent on size, with larger animals presenting higher Hg concentration. We conclude that Hg present in the tailings shows low mobility and that its eventual transport into the drainage system is dependent on the erosion of fine material from the wastes during rains, resulting in a restricted contamination of the area and low Hg concentration in the biota.

Mercury in the Madeira River ecosystem, Rondônia, Brazil

Abstract A survey of mercury levels in river water and sediments, forest soils, fish, air and human hair is presented for the Madeira River watershed in southwest Amazonia, Brazil. Mercury levels appeared particularly high in tributary rivers close to major gold-mining areas. High Hg levels in fish (up to 2.7 ppm) were also found in such areas. Atmospheric Hg levels were mostly close to background, but can reach high values (3.2 mg/m3) in the proximity of the HgAu reburning complex. Human-hair levels, however, reach values up to 26.7 ppm, indicating high exposure rates of the local population.

Mercury distribution in sediment profiles from lakes of the high pantanal, Mato Grosso State, Brazil

Sediment cores from lakes located in the Pantanal Swamp, Central Brazil were analysed for the distribution of mercury released by the local gold mining. Atmospheric transport is the only pathway of mercury contamination of these remote lakes. Mercury concentrations were higher at the surface of sediments (62 to 80 ug.kg−1) decreasing to values of 20 to 30 ug.kg−1 in deeper layers. Mercury deposition rate was estimated as 90 to 120 ug Hg.m−2yr−1 Although mercury concentrations were much lower than in industrialized areas, mercury deposition rate for these Pantanal lakes is of the same order of magnitude of deposition rates measured in lakes in industrialized areas

Use of epiphyte plants as biomonitors to map atmospheric mercury in a gold trade center city, Amazon, Brazil

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.

Mercury in Black-Waters of the Amazon

Negro river, the largest black-water tributary of the Amazon, has soils naturally rich in mercury (Hg) that is leached to the aquatic ecosystem by pedologic processes. The flooded areas of its basin are conducive to mercury methylation. Therefore, highest mercury concentrations have been observed in its black-water and biota even in regions without anthropogenic impacts. Here we show an integrated analysis of total mercury (THg) and methylmercury (MeHg) data of environmental samples collected along the Negro basin. THg concentrations in whole water of Negro river and its tributaries did not vary between two hydrological seasons, but in suspended matter were highest during high-water season showing that mercury was more associated to particulate form during this time. During high-water season, waters of Negro river and its tributaries showed highest MeHg concentrations, were more acid, and less oxygenated. The %MeHg in relation to THg of plankton from floodplain lakes of Negro basin was in the same range or higher than the values observed in plankton from natural lakes or reservoirs. Therefore, some processes can occur specially in the environmental conditions of Negro basin such as highest and fastest MeHg absorption by plankton and greater availability of MeHg to bioaccumulation. We conclude that probably MeHg is formed mainly in the flooded area, where dissolved oxygen in depleted and the microbial activity of anoxic organisms is increased. The Amazonian lakes are hot spots for MeHg absorption by planktonic communities and can have an important contribution to Hg concentrations of the basin by exporting large MeHg levels associated to these organisms. Along the food chain of the Negro basin, it was possible to observe the biomagnification of mercury from phytoplankton to dolphin, with increase of mercury concentrations around one order of magnitude from one trophic level to other. Amazon basins, including Negro, have been frightened by diverse land use that can change the mercury cycle and increase concentrations in aquatic systems.

Exposure to metallic mercury in workers in a tropical chloralkali plant evaluated through urine analysis, Rio de Janeiro, Brazil.

Occupational exposure to Hg vapour was investigated in 78 workers during three periods with different temperatures: August 1991, December 1991, and February 1992. Each individual was sampled twice in each period; before and after a six working days period (with a two free days interval). As an attempt to normalise Hg excretion urine was sampled always after a normal 8 hours night sleeping and immediately frozen. Mineralisation was done with acid and oxidant mixture and determination by cold vapour Atomic Absorption Spectrophotometry (Varian VGA-76 and AA-1475). Analytical accuracy was controlled by routine analysis of certified reference material (Seronorm TM trace elements, Nycome As diagnostics Olso - Norway) and all samples were analysed in triplicates. Of a total of 355 samples analysed 13% were over the maximum limit for occupational exposure (50 µg.l-1 or ppb). From the 78 individuals investigated 13% presented average value smaller than 10 ppb; just 8% had the average over 50 ppb; 64% showed averages smaller than 30 ppb; and 28% were between 30 and 50 ppb. Seasonal variation was observed with the highest values in the hottest periods. High variability was observed in the same individual even within an interval of just few days (seven days). No increase of Hg in urine after the six days of exposure was observed when compared with the values after the two free days interval.