Contaminação por mercúrio no Brasil: fontes industriais vs garimpo de ouro

This paper reviews the history of Hg contamination in Brazil by characterizing and quantifying two major sources of Hg emissions to the environment: industrial sources and gold mining. Industry was responsible for nearly 100% of total Hg emissions from the late 1940's to the early 1970's, when efficient control policies were enforced, leading to a decrease in emissions. Gold mining, on the other hand was nearly insignificant as a Hg source up to the late 1970's, but presently is responsible for over 80% of total emissions. Presently, over 115 tons of Hg are released into the atmosphere in Brazil annually. Nearly 78 tons come from gold mining operations, 12 tons come from chlor-alkali industry and 25 tons come from all other industrial uses. Inputs to soils and waters however, are still unknown, due to lack of detailed data base. However, emissions from diffuse sources rather than well studied classical industrial sources are probably responsible for the major inputs of mercury to these compartments.

A presença de mercúrio em casa constitui um risco de contaminação humana e / ou ambiental? Relato de um caso

Mercury kept in a garage of a residencial building in Rio de Janeiro was accidentally released and caused local (environmental and human) contamination. The concentration of mercury in indoor air of the most critical site reached 15.5 mg/m³. Outdoor air samples showed concentrations ranging from 0.37 to 6.6 mg/m³ . Seventy five per cent of the urine samples collected from 22 residents in the contaminated building showed levels of mercury higher than those observed in non exposed individuals (>6.9 mg/L); in 30% of these samples, the concentration was higher than 20 mg/L. These values show a high level of human contamination and the final consequences were not so serious owing to the quick action taken by one of the residents.

Os três princípios e as doenças: a visão de dois filósofos químicos

Paracelsus (1493 - 1541) developed a theory about three principles (sulphur, mercury, and salt) that would constitute matter, and whose mutual interactions within man's body could cause diseases. This paper discusses the influence of this theory on the work of two chemical philosophers. Oswald Crollius (1560 - 1609) considered that the conceptions of matter and disease were strongly related because of the macro - microcosm analogy, and classified diseases in sulphurean, mercurial and saline. On the other hand, J. B. Van Helmont (1579 - 1644) stated that sulphur, mercury, and salt were not true principles, and that every disease would have a specific origin. Instead of the principles, Van Helmont put the Archeus at the center of both his medical and matter theories.

Determinação de elementos-traço: relatório de dois exercícios interlaboratoriais

Results of two intercomparison exercises are reported. In the first one, the participants were asked to determine Cd, Cu, Pb and Zn, at the sub mg mL-1 level, in an acidified aqueous solution. In the second one, the participants were asked to determine mercury (total) in two homogeneous biological samples, hair and fish. The exercises were considered satisfactory and few reported results were discharged (3s criteria).

Metals and Selenium as bioindicators of geographic and trophic segregation in Giant Petrels Macronectes spp.

We analysed concentrations of cadmium, lead, mercury and selenium in blood from males and females of the 2 sibling species of giant petrels, the northern Macronectes halli and the southern M. giganteus, breeding sympatrically at Bird Island (South Georgia, Antarctica). Blood samples were collected in 1998 during the incubation period, from 5 November to 10 December. Between species, cadmium and lead concentrations were significantly higher for northern than for southern giant petrels, which probably resulted from northern giant petrels wintering in more polluted areas (mainly on the Patagonian Shelf and Falkland Islands) compared to southern giant petrels (wintering mainly around South Georgia and the South Sandwich Islands). Between sexes, cadmium concentrations were significantly higher for females than for males in both species, corresponding to the more pelagic habits of females compared to the more scavenging habits of males. Lead and cadmium concentrations in circulating blood decreased significantly over the incubation period, suggesting that when breeding at Bird Island, exposure to the source of pollution had ended, and these metals had been cleared from the blood and excreted, or rapidly transferred to other tissues. Association of lead and cadmium with a common source of pollution was further corroborated by a significant positive correlation between the levels of the 2 elements found. Mercury levels were similar between the species, but showed an opposite trend between sexes, with males showing higher levels than females in northern giant petrels, and the opposite was true in southern giant petrels, with no changes throughout incubation. Selenium levels were similar between sexes, but significantly greater for northern than for southern giant petrels. Moreover, there was a significant increase in the selenium levels over the incubation period in northern giant petrels. Age of adult birds did not affect metal concentrations. Coefficients of variation of metal levels were consistently lower for northern than for southern giant petrels, particularly for mercury, suggesting that the former species is more dietary specialised than the latter. Contaminant analyses, when combined with accurate information on seabird movements, obtained through geolocation or satellite tracking, help us to understand geographic variation of pollution in the marine environment.

Redução seletiva aplicada à especiação de mercúrio em peixes: uma adaptação do método de Magos

In the selective reduction procedure proposed by Magos SnCl2 was used as reductant for inorganic mercury while total mercury was determined after reduction with a mixture of SnCl2 and CdCl2. The difference between total mercury and inorganic mercury determines the content of organic mercury. The procedure of the present work differs of Magos in that the mercury vapour is carried to the absorption cell after magnetic stirring of the solution in the reaction flask; in the Magos procedure, mercury vapour is carried by bubbling the gas in to the solution. In contrast to the Magos procedure this slight modification overcame the necessity of at calibration by analyte addition, saving time and gainning accuracy.

Utilização de eletrodos potenciométricos de amálgama em estudos de complexação de substâncias húmicas

Potentiometric amalgam electrodes of lead, cadmium, and zinc are proposed to study the complexation properties of commercial and river sediment humic acids. The copper complexation properties of both humic acids were studied in parallel using the solid membrane copper ion-selective electrode (Cu-ISE). The complexing capacity and the averaged conditional stability constants were determined at pH 6.00 ± 0.05 in medium of 2x10-2 mol L-1 sodium nitrate, using the Scatchard method. The lead and cadmium amalgam electrodes presented a Nernstian behavior from 1x10-5 to 1x10-3 moles L-1 of total metal concentration, permitting to perform the complexation studies using humic acid concentrations around of 20 to 30 mg L-1, that avoids colloidal aggregation. The zinc amalgam electrode showed a subnernstian linear response in the same range of metal concentrations. The Scatchard graphs for both humic acids suggested two classes of binding sites for lead and copper and one class of binding site for zinc and cadmium.

Investigação espectroscópica dos carbonilos heterobimetálicos cis-[Fe(CO)4(HgX)2], X = Cl, Br,I

The series of compounds cis-[Fe(CO)4(HgX)2], X=Cl,Br,I shows an octahedral geometry around the iron atom with the two HgX groups cis to each other. In this paper the assignment for the carbonyl stretching modes and the calculation of their force constants were performed on the basis of the Cotton-Krainhanzel model. Taking into account all the data from the IR, 199Hg NMR and UV-vis spectra it is possible to verify the influence of X on the electronic densities at the metallic centers.

Compostos de mercúrio. Revisão de métodos de determinação, tratamento e descarte

This review article on mercury compounds deals with the differences on toxicity of different forms of this metal, the Brazilian regulation for its disposal and the usual methods of determination. Besides that, the text gives special emphasis on the methods used for the treatment and disposal of residues containing mercury, as well as the new developments being made in this area.

O uso de sílica gel organofuncionalizada como agente sequestrante para metais

An overview about the homogeneous and heterogeneous methods of synthesizing silylating agents and applications of the organofunctionalized silica-gel samples was explored. The pendant molecules attached covalently to the inorganic surface displayed important properties to act as sequestrating agents for metals in aqueous and non-aqueous solutions. The large variety of basic centres anchored on organic molecules improve the capacity in adsorbing cations. The increase in adsorption is dependent on the number of basic atoms disposed on the pendant molecules on the surface. The combination of acidic and basicity properties favours the selectivity, such is exemplified by the thiol modified silicas towards mercury (II) cations.

Uma célula eletroquímica de fluxo para modificação permanente de tubo de grafite empregado em absorção atômica

A flow cell assembled on the original geometry of a graphite tube to achieve permanent chemical modifier is proposed. The graphite tube operates as the working electrode. A stainless steel tube, positioned downstream from the working electrode, was used as the auxiliary electrode. The potential value applied on the graphite electrode was measured against a micro reference electrode (Ag/AgCl) inserted into the auxiliary electrode. Palladium solutions in acetate buffer (100 mmol L-1, pH = 4.8), flowing at 0.5 mL min-1 for 60 min was used to perform the electrochemical modification. A mercury solution (1 ng) was used to evaluate the performance of the permanent palladium modifier.

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