Avaliação da contaminação mercurial mediante análise do teor de Hg total em amostras de cabelo em comunidades ribeirinhas do Tapajós, Pará, Brasil

Este estudo avalia a contaminação mercurial em comunidades de pescadores em quatro localidades nas margens do rio Tapajós: Rainha, Barreiras, São Luís do Tapajós e Paraná-Mirim. Análises toxocológicas das amostras de cabelo foram realizadas por espectofotometria de absorção atômica. Os níveis de mercúrio total em amostras de cabelo variaram entre 2,9µg/g e 71,5µg/g. Os valores mais baixos foram encontrados na comunidade de Paraná-Mirim. Os mais elevados, em São Luís do Tapajós e Barreiras, cerca de seis a sete vezes superiores ao valor estabelecido. As diferenças entre as concentrações médias de mercúrio total nas amostras, coletadas em populações ribeirinhas, a montante e a jusante do rio Tapajós em Itaituba, não apresentaram significância estatística (p > 0,05). Conclui-se que a exposição humana ao mercúrio por ingestão de peixes contaminados constitui risco potencial para o aparecimento de sintomas e sinais da doença de Minamata, o que recomenda a manutenção de um programa de vigilância epidemiológica.

Determinação de mercúrio total no material particulado atmosférico do Distrito Federal, Brasil

Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Tecnologia Química e Biológica, 2016.

Nitrous oxide emissions from irrigated cotton soils of northern Australia

An automated gas sampling methodology has been used to estimate nitrous oxide (N2O) emissions from heavy black clay soil in northern Australia where split applications of urea were applied to furrow irrigated cotton. Nitrous oxide emissions from the beds were 643 g N/ha over the 188 day measurement period (after planting), whilst the N2O emissions from the furrows were significantly higher at 967 g N/ha. The DNDC model was used to develop a full season simulation of N2O and N2 emissions. Seasonal N2O emissions were equivalent to 0.83% of applied N, with total gaseous N losses (excluding NH3) estimated to be 16% of the applied N.

Determinação de alguns parâmetros indicadores de poluição por efluente líquido de um aterro sanitário

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Manifestações neurológicas em ribeirinhos de áreas expostas ao mercúrio na Amazônia brasileira

No presente estudo, foram avaliados comparativamente os níveis atuais de exposição ao mercúrio e as manifestações neurológicas em ribeirinhos residentes em comunidades situadas no Estado do Pará, Brasil. Participaram do estudo 78 ribeirinhos de Barreiras (bacia do rio Tapajós), 30 de São Luiz do Tapajós (bacia do rio Tapajós) e 49 do Furo do Maracujá (bacia do rio Tocantins). As concentrações de mercúrio total foram quantificadas, em cabelo, pela espectrofotometria de absorção atômica, e a avaliação neurológica foi realizada por meio de testes de rotina. As concentrações de mercúrio nas comunidades do Tapajós foram maiores que as do Tocantins (p < 0,01). A avaliação das alterações neurológicas não mostrou diferença significativa entre as comunidades das áreas expostas e controle para os resultados observados pelo exame neurológico convencional, exceto para desvio da marcha (p < 0,05). Concluiu-se que, apesar dos níveis de exposição ao mercúrio, houve uma baixa frequência de alterações somatossensoriais encontradas por meio de exames neurológicos convencionais.

Untersuchungen zur biotischen Bildung von Methylquecksilber aus anorganischem Quecksilber durch intestinale Sulfat-reduzierende Bakterien und die Bestimmung alkylierter Quecksilberverbindungen mittels GC-ICP-MS und Isotopenverdünnungsanalyse

Alkylierte Quecksilberspezies sind hundertfach toxischer als anorganisches Quecksilber (Hg) und werden in der Nahrungskette mit zunehmender Trophieebene im Gewebe von Tieren und dem Menschen akkumuliert. Aufgrund der Relevanz für die Umwelt und den Effekt auf die menschliche Gesundheit kommt der biotischen Transformation von anorganischem Hg zu Monomethylquecksilber (MeHg) eine große Bedeutung zu. Es ist bekannt, dass Sulfat-reduzierende Bakterien zu den Hauptproduzenten von MeHg gehören. Darüber hinaus gibt es jedoch nur wenige Untersuchungen über die biologischen Mechanismen und die Zusammenhänge in terrestrischen und insbesondere in intestinalen Systemen. Die vorliegende Arbeit leistet daher einen wichtigen Beitrag zur Abschätzung des Potentials zur Hg-Methylierung durch intestinale Bakterien und vertieft die Kenntnisse zu der damit verbundenen Akkumulation der organischen Schwermetallverbindung im Gewebe des Kompostwurms Eisenia foetida (E. foetida). rnIm Rahmen dieser Arbeit wurde erstmals unter Anwendung der Gas Chromatographie mit induktiv gekoppelter Massenspektrometrie (GC-ICP-MS) und Isotopenverdünnungsanalyse verschiedene Kulturen intestinaler Sulfat-reduzierender Bakterien auf die Bildung von organischem Monomethylquecksilber aus Hg(II) untersucht. Da in komplexen bakteriellen Nährlösungen mit hohem Sulfidgehalt Matrixeffekte auftreten und die Analyse von MeHg im Ultraspurenbereich erschweren können, erfolgte die Probenvorbereitung mittels der Methanol-Kaliumhydroxid-Extraktion unter Verwendung eines Maskierungsreagenzes und der Derivatisierung mit Natriumtetrapropylborat. Das Detektionslimit für MeHg in bakteriellen Nährlösungen betrug 0,03 ng/mL. Die Wiederfindung von zertifiziertem Referenzmaterial ERM® CE-464 Tuna Fish war sehr gut und lag in einem Bereich zwischen 98 – 105%. rnDie Resultate der Untersuchung von 14 verschiedenen Rein- und Anreicherungskulturen Sulfat-reduzierender Bakterien zeigten, dass neun Kulturen innerhalb von 12 h nach einer Inkubation mit 0,1 mg/L Hg2+ im Durchschnitt 100 bis 1200 pg/mL MeHg produzierten. Darunter waren zwei Desulfovibrio sp. Stämme, die Spezies Desulfovibrio piger, Desulfovibrio giganteus, Desulfovibrio termitidis, Desulfotomaculum ruminis, Desulfobulbus propionicus sowie Anreicherungskulturen aus dem Intestinaltrakt einer Zygoptera-Larve Zy1 und E. foetida EF4. Die Fähigkeit zur Hg-Methylierung durch eine Spezies der Ordnung Desulfotomaculum aus der Gruppe der Gram-positiven Firmicutes wurde hiermit erstmals beobachtet.rnWeiterhin wurde gezeigt, dass im Intestinaltrakt von E. foetida im Gegensatz zu mikrobiellen Bodenproben eine signifikante biotische Methylierung von Hg(II) durchgeführt wird. Dass diese Transformationen in hohem Maße von der intestinalen Region ausgeht und somit zur Akkumulation von MeHg im Gewebe beiträgt, konnte durch weiterführende Experimente mittels Laserablations-ICP-MS an histologischen Gefrierschnitten des Invertebraten darge-stellt werden. rn

Methylmercury, total mercury and total selenium in four common freshwater fish species from Ya-Er Lake, China

Snakehead fish (Ophiocephalus argus cantor), silver carp (Hypophthalmichthys molitrtix), crucian carp (Carassius carassius), and common carp (Cyprinus carpio) are four common freshwater fish species in China. In this study, the level of methylmercury (MeHg), total mercury (T-Hg), and total selenium (T-Se) in muscle samples of these four fish species from Ya-Er Lake, China, were analyzed using atomic fluorescence spectrometry coupled with high-performance liquid chromatography, and inductively coupled plasma mass spectrometry. The concentrations of MeHg in all the fish species were significantly correlated with those of T-Hg. Higher T-Hg and MeHg concentrations had accumulated in the snakehead fish, which is a strongly predatory fish, than in the other three species. The concentration ratios of MeHg and T-Hg in the muscles of these four fish species were almost equal. Conversely, there was negative correlation between the concentrations of T-Hg and T-Se, which implies that there is a competition between these two elements with respect to bioaccumulation. It is noteworthy that of all the muscle samples tested, the level of T-Hg exceeded the maximum allowable limit in fish [0.4 mg kg(-1) (w/w) recommended by the World Health Organization] in 38.46% of those of the silver carp, 18.18% of those of the crucian carp, and 100% of those of snakehead fish. These results show that the consumption of contaminated fish is a potential threat to human health and that necessary preventive measures to safeguard public health should be emphasized.

Analytical procedure for total mercury determination in fishes and shrimps by chronopotentiometric stripping analysis at gold film electrodes after microwave digestion

A method for the total mercury determination in fish and shrimps employing chronopotentiometric stripping analysis on gold film electrodes is described. Fish and shrimp tissues were digested using a microwave oven equipped with closed vessels. We developed a microwave heating program which decomposed all the samples employing diluted nitric acid and hydrogen peroxide. The proposed method was validated by analyzing a certified reference material and then applied for different fish species from fresh water and seawater acquired in local markets of São Paulo city, Brazil. The Brazilian legislation establishes 0.5 and 1 mg per kilogram of fish as upper limit of mercury for omnivorous and predator species, respectively. Except for blue shark tissues, the mercury content was situated below 0.5 mu g g(-1) for all the analyzed samples. The detection limit of the proposed method was calculated as 5 ng g(-1) of sample utilizing 5 minutes of electrodeposition (+300 mV vs. Ag/AgCl) on the gold electrode. (c) 2006 Elsevier Ltd. All rights reserved.

Mercury species concentrations near Casey station, Antarctica and along the SR3 CASO-GEOTRACES transect

We present here the first mercury speciation study in the water column of the Southern Ocean, using a high-resolution south-to-north section (27 stations from 65.50°S to 44.00°S) with up to 15 depths (0-4440 m) between Antarctica and Tasmania (Australia) along the 140°E meridian. In addition, in order to explore the role of sea ice in Hg cycling, a study of mercury speciation in the 'snow-sea ice-seawater' continuum was conducted at a coastal site, near the Australian Casey station (66.40°S; 101.14°E). In the open ocean waters, total Hg (Hg(T)) concentrations varied from 0.63 to 2.76 pmol/L with 'transient-type' vertical profiles and a latitudinal distribution suggesting an atmospheric mercury source south of the Southern Polar Front (SPF) and a surface removal north of the Subantartic Front (SAF). Slightly higher mean Hg(T) concentrations (1.35 ± 0.39 pmol/L) were measured in Antarctic Bottom Water (AABW) compared to Antarctic Intermediate water (AAIW) (1.15 ± 0.22 pmol/L). Labile Hg (Hg(R)) concentrations varied from 0.01 to 2.28 pmol/L, with a distribution showing that the Hg(T) enrichment south of the SPF consisted mainly of Hg(R) (67 ± 23%), whereas, in contrast, the percentage was half that in surface waters north of PFZ (33 ± 23%). Methylated mercury species (MeHg(T)) concentrations ranged from 0.02 to 0.86 pmol/L. All vertical MeHg(T) profiles exhibited roughly the same pattern, with low concentrations observed in the surface layer and increasing concentrations with depth up to an intermediate depth maximum. As for Hg(T), low mean MeHg(T) concentrations were associated with AAIW, and higher ones with AABW. The maximum of MeHg(T) concentration at each station was systematically observed within the oxygen minimum zone, with a statistically significant MeHg(T) vs Apparent Oxygen Utilization (AOU) relationship (p <0.001). The proportion of Hg(T) as methylated species was lower than 5% in the surface waters, around 50% in deep waters below 1000 m, reaching a maximum of 78% south of the SPF. At Casey coastal station Hg(T) and Hg(R) concentrations found in the 'snow-sea ice-seawater' continuum were one order of magnitude higher than those measured in open ocean waters. The distribution of Hg(T) there suggests an atmospheric Hg deposition with snow and a fractionation process during sea ice formation, which excludes Hg from the ice with a parallel Hg enrichment of brine, probably concurring with the Hg enrichment of AABW observed in the open ocean waters. Contrastingly, MeHg(T) concentrations in the sea ice environment were in the same range as in the open ocean waters, remaining below 0.45 pmol/L. The MeHg(T) vertical profile through the continuum suggests different sources, including atmosphere, seawater and methylation in basal ice. Whereas Hg(T) concentrations in the water samples collected between the Antarctic continent and Tasmania are comparable to recent measurements made in the other parts of the World Ocean (e.g., Soerensen et al., 2010; doi:10.1021/es903839n), the Hg species distribution suggests distinct features in the Southern Ocean Hg cycle: (i) a net atmospheric Hg deposition on surface water near the ice edge, (ii) the Hg enrichment in brine during sea ice formation, and (iii) a net methylation of Hg south of the SPF.

Total mercury and total methylmercury during the POLARSTERN cruise ARK-XXVI/3 (TransArc)

Methylmercury (MeHg) is a neurotoxic compound that threatens wildlife and human health across the Arctic region. Though much is known about the source and dynamics of its inorganic mercury (Hg) precursor, the exact origin of the high MeHg concentrations in Arctic biota remains uncertain. Arctic coastal sediments, coastal marine waters and surface snow are known sites for MeHg production. Observations on marine Hg dynamics, however, have been restricted to the Canadian Archipelago and the Beaufort Sea (<79°N). Here we present the first central Arctic Ocean (79-90°N) profiles for total mercury (tHg) and MeHg. We find elevated tHg and MeHg concentrations in the marginal sea ice zone (81-85°N). Similar to other open ocean basins, Arctic MeHg concentration maxima also occur in the pycnocline waters, but at much shallower depths (150-200 m). The shallow MeHg maxima just below the productive surface layer possibly result in enhanced biological uptake at the base of the Arctic marine food web and may explain the elevated MeHg concentrations in Arctic biota. We suggest that Arctic warming, through thinning sea ice, extension of the seasonal sea ice zone, intensified surface ocean stratification and shifts in plankton ecodynamics, will likely lead to higher marine MeHg production.

Particle and gaseous emissions from commercial aircraft at each stage of the landing and takeoff cycle

A novel technique was used to measure emission factors for commonly used commercial aircraft including a range of Boeing and Airbus airframes under real world conditions. Engine exhaust emission factors for particles in terms of particle number and mass (PM2.5), along with those for CO2, and NOx were measured for over 280 individual aircraft during the various modes of landing/takeoff (LTO) cycle. Results from this study show that particle number, and NOx emission factors are dependant on aircraft engine thrust level. Minimum and maximum emissions factors for particle number, PM2.5, and NOx emissions were found to be in the range of 4.16×1015-5.42×1016 kg-1, 0.03-0.72 g.kg-1, and 3.25-37.94 g.kg-1 respectively for all measured airframes and LTO cycle modes. Number size distributions of emitted particles for the naturally diluted aircraft plumes in each mode of LTO cycle showed that particles were predominantly in the range of 4 to 100 nm in diameter in all cases. In general, size distributions exhibit similar modality during all phases of the LTO cycle. A very distinct nucleation mode was observed in all particle size distributions, except for taxiing and landing of A320 aircraft. Accumulation modes were also observed in all particle size distributions. Analysis of aircraft engine emissions during LTO cycle showed that aircraft thrust level is considerably higher during taxiing than idling suggesting that International Civil Aviation Organization (ICAO) standards need to be modified as the thrust levels for taxi and idle are considered to be the same (7% of total thrust) [1].