Edinaldo de Castro e Silva

Mercury net methylation in five tropical flood plain regions of Brazil: high in the root zone of floating macrophyte mats but low in surface sediments and flooded soils.

Mercury net methylation in five tropical flood plain regions of Brazil: high in the root zone of floating macrophyte mats, but low in surface sediments and flooded soils

Fish mercury concentration in the Alto Pantanal, Brazil: influence of season and water parameters

The tropical flood plain Pantanal is one of the worlds largest wetlands and a wildlife sanctuary. Mercury (Hg) emissions from some upstream gold mining areas and recent findings of high natural Hg levels in tropical oxisols motivated studies on the Hg cycle in the Pantanal. A survey was made on total Hg in the most consumed piscivorous fish species from rivers and floodplain lakes in the north (Cáceres and Barão de Melgaço) and in the south part of Alto Pantanal (around the confluence of the Cuiabá and Paraguai rivers). Samples were collected in both the rainy and dry seasons (March and August 1998) and included piranha (Serrasalmus spp.), and catfish (Pseudoplatystoma coruscans, pintado, and Pseudoplatystoma fasciatum, cachara or surubim). There was only a small spatial variation in Hg concentration of the 185 analyzed fish samples from the 200 x 200 km large investigation area, and 90% contained total Hg concentration below the safety limit for regular fish consumption (500 ng g(-1)). Concentration above this limit was found in both Pseudoplatystoma and Serrasalmus samples from the Baia Siá Mariana, the only acid soft-water lake included in this study, during both the rainy and dry seasons. Concentration above this limit was also found in fish outside Baia Siá Mariana during the dry season, especially in Rio Cuiabá in the region of Barão de Melgaço. The seasonal effect may be connected with decreasing water volumes and changing habitat during the dry season. The results indicate that fertile women should restrict their consumption of piscivorous fishes from the Rio Cuiabá basin during the dry season. Measures should be implanted to avoid a further deterioration of fish Hg levels.

Relationship of mercury with aluminum, iron and manganese oxy-hydroxides in sediments from the Alto Pantanal, Brazil

Sediments from nine floodplain lakes in Pantanal were analyzed for a large-scale (300 km) survey of mercury (Hg) load in sediments and soils of the Alto Pantanal and to study the relationship between Hg and reactive aluminum, iron, and manganese oxy-hydroxides. The results were compared with the Hg content in river and stream sediments from the Poconé gold mining area, where Hg has been extensively used and still is in use. The results indicate that the Hg concentrations were elevated in river sediment close to the mining area in Bento Gomes river basin (average in the < 74-microm fraction 88.9 ng Hg g(-1) dry wt.; interquartile range 50.3-119.5), but there was no clear indication that the local Hg emissions have contaminated the remote floodplain lakes, where concentrations were surprisingly low (average in the < 74-microm fraction 33.2 ng Hg g(-1) dry wt. sediment; interquartile range 18.4-46.8), in particular when considering geochemical characteristics of the sediment. The sediment from the floodplain lakes contained less Hg-tot and more reactive iron oxy-hydroxides than soils from the Tapajós area in the Amazon basin. This resulted in a mass ratio between Hg and amorphous oxy-hydroxides of only 5 x 10(-6) for Hg-tot/Fe-oxa (interquartile range 3-7 x 10(-6).

Mercury Behavior in a Tropical Environment: The Case of Small-Scale Gold Mining in Poconé, Brazil

An estimated 50 tons of mercury (Hg) have been emitted by gold miners in the Bento Gomes river basin, in the municipality of Poconé, Brazil, since the 1980s. Since the mid-l990s, the state agency for environmental protection, FEMA (Fundação Estadual do Meio Ambiente de Mato Grosso), has enforced regulations to reduce Hg emissions to air and water and has also implemented an environmental assessment program. The objectives of this study were to evaluate efforts to reduce emissions of Hg to air and water from nine improved amalgamation centers, and to assess the pollution level in sediment at 25 sites around Poconé. In spite of the fact that retorts were used, results showed large emissions of Hg when burning amalgam, resulting in Hg air concentrations above the limit for occupational air (50 μg/m3) at all centers except one. Keeping washing water in closed systems and dumping residues in specially prepared sites reduced Hg emissions to watercourses. The average Hg concentration of fine sediments (<74 μm) in the Bento Gomes river basin was 104 ng Hg/g dry weight, three to four times higher than the background level; large amounts of Hg-contaminated sediments are re-suspended during the rainy season. In conclusion, present emissions to local watercourses have been efficiently reduced, but the use of retorts in improved amalgamation centers has not adequately reduced Hg emissions to air, which is why the use of Hg remains an occupational and environmental problem.

Falta de saneamento básico e as águas subterrâneas em aquífero freático: região do Bairro Pedra Noventa, Cuiabá (MT)

This study aimed to assess the impacts on the bacteriological and chemical quality of groundwater, the water table aquifer in the area Neighborhood Ninety Stone in Cuiaba (MT). For this, we selected 31 wells venly distributed throughout this neighborhood. The analysis results led to the following conclusions: 1 - Chemical parameters studied did not show very high concentrations, although the pH, ammonia, nitrate and phosphate have showed concentrations outside the Permissible Maximum Values for human consumption, required by Ordinance 2.914/2011; probably originate from septic tanks, which are widespread in the region and decomposing organic matter falling in open wells. 2 - Concentration of chemical elements between periods of drought and rain changed in all parameters evaluated. This indicates that there were seasonal fluctuations in quality, with the largest concentrations in the rainy season and lower in the dry season, probably due to leaching processes are more intense than the processes of dilution. 3 - The bacteriological analyzes (total coliforms and Escherichia coli) had concentrations above the Maximum Allowable Values for human consumption, probably due to septic tanks intensely distributed in the region. 4 - Changes in groundwater probably are due to lack of sanitation in the region.

Composição química das águas de chuva em áreas tropicais continentais, Cuibá-MT: aplicação do sistema clima urbano (S.C.U.)

Avaliou-se a composicao quimica de aguas da chuva em Cuiaba-MT sob a perspectiva do Sistema Clima Urbano (S.C.U.), considerando-se as fontes emissoras, as caracteristicas geograficas/topograficas da cidade, e a relacao entre o homem e a natureza. O periodo de amostragem foi entre os dias 21/02 e 02/07 de 2006, representando o final da estacao chuvosa e inicio da estacao seca da regiao. No total de 38 amostras determinaram-se a acidez (medidas de pH), a condutividade eletrica e a concentracao dos ânions nitrato, sulfato, cloreto, nitrito e fosfato. Tambem foi observada a influencia do numero de dias anteriores sem chuvas ao evento na variabilidade da composicao quimica destas amostras. Os resultados mostraram que mesmo com valores de pH inferiores a 5,6, portanto, chuvas ligeiramente acidas; as concentracoes dos ânions foram baixas, indicando a existencia de chuvas limpas. Para o periodo do estudo, pode-se considerar Cuiaba representando area continental ainda nao impactada com atividades antropicas.

ESTUDO DA DISPOSIÇÃO FINAL DE RESÍDUOS SÓLIDOS DE CURTUME COMO FONTE DE ALTERAÇÃO DA QUALIDADE DAS ÁGUAS SUBTERRÂNEAS

This work aim to study the impacts caused by the disposal of residues from two tanneries localized in the municipalities of Cuiaba and Varzea Grande in Mato Grosso State, particularly on groundwater. In one of the tanneries (tannery 1), the final residue disposal was done over an impermeable blanket inside a trench covered with amianthus tiles while in the other (tannery 2) the residues were disposed directly on the soil covered with the impermeable blanket. To achieve this objective, physical chemical and chemical properties which could indicate alteration of groundwater quality in the areas of final disposal of tannery residues were determined. Groundwater samples were collected in monitoring wells built in those areas. The analysis of the physical chemical and chemical variables allowed the following conclusions: i) the residues disposal in tannery 1 contributed to increase chromium concentrations, pH; electrical conductivity and also total dissolved solids; ii) the residues disposal in tannery 2, contributed to increase the concentrations of chloride, electrical conductivity and as a consequence total dissolved solids. Although the two tanneries are at work for different times (tannery 1 from 2000 and tannery 2 from 1986) using different residues disposal procedures, no significant difference were observed in the alteration of groundwater quality in the two sites.