Ene Glória da Silveira

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.

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.

Preference ratios for mercury and other chemical elements in the Madeira River, Brazil

Samples of water, suspended solids, and bottom sediments from the Madeira River, Rondonia state, Brazil, were physically and chemically analyzed to investigate the actual Hg mobilization in the aquatic environment and compare it with that of other heavy metals and elements in the area. Two dimensionless Hg preference ratios were defined, expressing (1) the ratio of Hg and other elements in the liquid phase divided by the ratio of Hg and other elements in bottom sediments (Pl.phase) and (2) the ratio of Hg and other elements in the particulate matter divided by the ratio of Hg and other elements in bottom sediments (Ps.solids). These preference ratios are useful for comparing Hg transport in three different phases (liquid, particulate matter, and bottom sediments). They also were applicable to any analyzed element in the area studied, because they generated an almost constant value when the maximum calculated was divided by the minimum (Pl.phase=2931; Ps.solids=84) and because of their sensitivity to the dominance of sorption processes by Fe oxides and hydroxides. Mercury could be transported preferentially to other analyzed elements in the particulate phase only if its concentration reached values at least 104-fold higher than those expected or quantified in the area.

Dose de exposição radiométrica de granitos do estado de Rondônia, Brasil

This work evaluated the activity concentration of the radioelements K, eU and eTh in samples of granites from Rondonia State, Brazil. The statistical analysis of the data indicated that they fit lognormal distributions. The modal values correspond to about 11% for K, 29 ppm for eU and 85 ppm for eTh. Directsignificant correlations were found among the concentrations of the three radioelements, i.e. r = 0.71 (between K and eU), r = 0.72 (between K and eTh), andr = 0.72 (between eU and eTh), suggesting congruency of their accumulation in minerals occurring in the rocks analyzed. The activity concentration data allowed estimate the absorbed dose rate in air at 1 m above the ground, which also fits a lognormal distribution characterized by a mode of 2.7 mSv/y that is slightly higher than the average worldwide exposure of 2.4 mSv/y. The results obtained also allowed evaluate if the granites analyzed are radiometrically suitable as building and ornamental materials.

Assessing mercury pollution in Amazon River tributaries using a Bayesian Network approach

Mercury pollution of water bodies exerts significant human and ecosystem health impacts due to high toxicity. Relatively high levels of mercury have been detected in the Amazon River and its tributaries and associated lakes. The study employed a Bayesian Network approach to investigate the contribution from geogenic sources to mercury pollution of lakes in the Madeira River basin, which is the largest tributary of the Amazon River. It was found that the source indicators of naturally occurring mercury have both, positive and negative relationships with mercury in lake sediments. Although the positive relationships indicated the influence of geological and soil formations, the negative relationships implied that the use of mercury amalgam for gold extraction in artisanal and small-scale mining (ASM), which is the primary anthropogenic source of mercury, also contribute to mercury in Amazon tributaries. This was further evident as mercury concentrations in lake sediments were found to be significantly higher than those in the surrounding rocks. However, potential anthropogenic mercury was attributed to historical inputs from gold mining due to the recent decline of ASM mining practice in the region.