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Mercury cycling between the water column and surface sediments in a contaminated area

Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.14%
Mercury cycling in the water column and upper sediments of a contaminated area, the Largo do Laranjo, Aveiro (Portugal), was evaluated after determination of reactive and non-reactive mercury concentrations in the water column and pore waters of sediments, collected in several places of this bay. In the water column, reactive mercury concentrations varied between 10 and 37 pmol dm−3, the highest values being observed near the mercury anthropogenic source. However, reactive mercury was a narrowly constrained fraction of the total mercury, making up only 4–16% of the total, showing evidence of the importance of dissolved organic matter on mercury transport. In sediments, higher concentrations of mercury were also determined near industrial discharges. Results indicate the existence of an equilibrium between solid and liquid phases, determined by solid sediment/pore water distribution coefficients. Much of the mercury present in the solid fraction is associated with organic matter (r=0.837) and iron oxyhydroxides (r=0.919), but as oxides begin to dissolve in reduced sediments and organic matter decays, the adsorbed mercury is released. In fact, the mercury concentrations in pore waters of those contaminated sediments largely exceeded the values determined in the water column. As molecular diffusion may contribute to the dissolved mercury distribution in the overlying water column...

Mercury behaviour in the water column of an impacted coastal lagoon: Ria de Aveiro (Portugal) as a case study

Ramalhosa, Elsa; Pereira, Eduarda; Duarte, Armando
Fonte: Nova Science Publishers Publicador: Nova Science Publishers
Tipo: Parte de Livro
ENG
Relevância na Pesquisa
37.15%
As mercury presents high toxicity and is of great concern when dealing with protection of human health, mercury pollution related issues are the main subject of this work. At first, two general themes are discussed, namely: I) Mercury: highlights of physicochemical and biogeochemical properties of interest and of the main natural and anthropogenic metal sources; and II) Biogeochemical cycling of mercury in the water column of natural waters. Secondly, a case study performed in Ria de Aveiro (Portugal) during the last 10 years will be presented, focusing on water column processes. Ria de Aveiro is a coastal lagoon, located along the Atlantic Ocean on the north-western coast of Portugal, which was subjected to a discharge of an effluent rich in mercury from a chlor-alkali industry, during more than five decades. In the last seventeen years, the industry changed its technology and the discharge of anthropogenic mercury diminished considerably. However, the dissolved total and reactive mercury concentrations, as well as the total mercury contents determined in the suspended particulate matter, obtained in a particular area of Ria de Aveiro, namely Largo do Laranjo, during the years of 1997 to 2000, are still high in comparison to other locals located world wide. In Largo do Laranjo water column...

Mercury mobility in a salt marsh colonised by Halimione portulacoides

Válega, M.; Lillebø, A. I.; Caçador, I.; Pereira, M. E.; Duarte, A. C.; Pardal, M. A.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
37.11%
The present study intends to increase the knowledge on the mobility of mercury in a salt marsh colonised by Halimione portulacoides. Mercury distribution in the sediment layers and its incorporation into the plant biomass were assessed, as well as the potential export of mercury from the contaminated area to the adjacent environment. Mercury pools in the sediments ranged from 560 to 943 mg m-2 and are largely associated with the solid fraction, with just a small amount being associated with the pore waters. Estimated diffusive fluxes of reactive mercury ranged from 1.3 to 103 ng m-2 d-1. Despite the above ground biomass values being comparatively higher than below ground biomass values, the mercury pools were much higher in the root system (0.06-0.16 mg m-2 and 29-102 mg m-2, respectively). The annual bioaccumulation of mercury in above ground tissues was estimated in 0.11 mg m-2 y-1, while in below ground biomass the values were higher (72 mg m-2 y-1). The turnover rates of H. portulacoides biomass suggest higher mercury mobility within the plant rhizosphere. Taking into account the pools of mercury in above ground biomass, the export of mercury by macro-detritus following the "outwelling hypothesis" is not significant for the mercury balance in the studied ecosystem. The mercury accumulated in the below ground part of the plant is quite mobile...

Macroalgae response to a mercury contamination gradient in a temperate coastal lagoon (Ria de Aveiro, Portugal)

Coelho, J. P.; Pereira, M. E.; Duarte, A.; Pardal, M. A.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
37.11%
Primary producers represent an important pathway for mercury incorporation in aquatic food webs. With eutrophication processes occurring worldwide, macroalgae may represent a substantial pool of mercury, as a result of its high growth rate and capacity to bind trace metals. The main aim of this work was to evaluate the response of the macroalgae to a human-induced environmental mercury gradient in a temperate coastal lagoon, by assessing the total and organic mercury contamination levels of the dominant species (Enteromorpha, Fucus and Gracilaria). Total mercury in the plant tissues ranged from 0.02 to 2.1 [mu]g g-1 dwt. Fucus was the most contaminated algae, followed by Gracilaria and Enteromorpha. As a whole, organic mercury never exceeded 15% of total mercury content, but tended to increase with distance to metal source on all macroalgae indicating complex physiological responses from these primary producers in areas of high and low mercury concentrations. Sessile macroalgae may be important mercury immobilisation agents, while free-floating algae (Enteromorpha) play an important role in mercury transport from contaminated areas (±10 g ha-1) to other areas of the lagoon and even to coastal waters. Based on the present results the use of macroalgal biomass from contaminated areas for direct or indirect human use (e.g. agricultural...

Avaliação da contaminação por mercúrio em peixes do Alto Pantanal ; Evaluation of mercury fish contamination in Alto Pantanal

Kuno, Rubia
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 18/06/2003 PT
Relevância na Pesquisa
37.17%
Para avaliar a contaminação por mercúrio em peixes do Alto Pantanal, foram analisadas 74 amostras de peixes piscívoros das espécies Pseudoplatystoma fasciatum(cachara), Pirinanpus pirinanpu (barbado), Serrasalmus spp. (piranha), Pseudoplatystoma coruscans (pintado), Salminus maxillosus (dourado), Hemisorubin plathyrhynchos (jurupoca) e Surubin lima (jurupensém). Também foram analisadas amostras de sedimento e de material particulado em suspensão na água. As amostras foram coletadas no ano de 2000. As determinações de mercúrio total foram feitas por espectrometria de absorção atômica sem chama utilizando-se gerador de vapor frio VGA 77 da Varian® acoplado a um espectrômetro Varian® 220. As concentrações de mercúrio total nas amostras de peixe variaram de 0,02 ug/g (piranha) a 0,80 ug/g (cachara). As concentrações de mercúrio em piranhas variaram de 0,02 ug/g a 0,50 ug/g, com média de 0,16 ug/g +/- 0,12. A área CBA 2 (baías do rio Cuiabá, região próxima de Barão de Melgaço) foi a que teve as concentrações mais elevadas em relação às áreas BNG 1 (rio Bento Gomes, Poconé) (p=0,003), PAG 3 (rio Paraguai, Taiamã e Descalvado) (p=0,002) e PAG 5 (rio Paraguai, confluência com rio Cuiabá) (p<0,001)...

Estudo de Tilápias do Nilo (Oreochromis niloticus) como bioindicadores da poluição por mercúrio nos lagos do Parque Ibirapuera e do Parque Ecológico do Tietê na Grande São Paulo; Study on Nile Tilapia (Oreochromis niloticus) as mercury pollution bioindicators at Parque Ibirapuera and Parque Ecológico do Tietê lakes at Greater São Paulo

Carretero, Maria Eugenia
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 17/12/2012 PT
Relevância na Pesquisa
37.08%
A Grande São Paulo, composta por 39 municípios, apresenta crescimento urbano e industrial expoente que contribuem para o constante acúmulo de poluentes no ambiente. Ainda assim, exibe áreas verdes remanescentes que contribuem para a sustentabilidade ambiental da cidade, como por exemplo, o Parque Ibirapuera e o Parque Ecológico do Tietê. Nesse contexto, o presente estudo visa verificar a viabilidade em utilizar as O. niloticus como bioindicadoras da poluição por mercúrio no ecossistema aquático dos dois parques da Grande São Paulo. Obteram-se para as tilápias do Nilo do Parque Ibirapuera pertencentes aos pontos de coleta A, B e C durante o inverno as respectivas concentrações de mercúrio total no sangue 2,72±4,20µg/L, 2,45±1,90µg/L e 1,19±0,05µg/L e, no hepatopâncreas as respectivas concentrações de mercúrio de 0,07±0,02 µg/g, 0,06 ±0,005 µg/g e 0,16 ±0,07 µg/g. No verão as tilápias do Parque Ibirapuera apresentaram nos mesmos pontos de coleta as respectivas concentrações de mercúrio total no sangue 2,50±0,84µg/L, 2,67±1,03µg/L e 2,430±0,790µg/L e, no hepatopâncreas as respectivas concentrações de mercúrio de 0,08 ±0,03 µg/L, 0,16 ±0...

Lipid peroxidation vs. antioxidant modulation in the bivalve Scrobicularia plana in response to environmental mercury-Organ specificities and age effect

Ahmad, I.; Mohmood, I.; Mieiro, C. L.; Coelho, J. P.; Pacheco, M.; Santos, M. A.; Duarte, A. C.; Pereira, E.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.11%
This study aimed at the assessment of mercury burden and its association to damage vs. antioxidant protection in the bivalve Scrobicularia plana environmentally exposed to mercury. Inter-age and organ-specific approaches were applied by using different annual size classes (2+, 3+, 4+ and 5+ year old) and assessing specific organs (gills, digestive gland), respectively. Bivalves were collected from moderately and highly contaminated sites at Laranjo basin – Ria de Aveiro (Portugal), where a mercury gradient was identified, and compared with those from a reference site. Besides total and organic mercury accumulation, endpoints combining lipid peroxidation (LPO), as a damage sign, and antioxidant protection (catalase, CAT; glutathione peroxidase, GPX; glutathione S-transferase, GST, activities) were determined. The whole-body accumulation as total mercury changed according to the environmental gradient for all age classes, while in terms of organic mercury, only 5+-year-old animals showed increased accumulation with increased environmental mercury level. Mercury induced peroxidative damage, showing that antioxidative mechanisms were insufficient. The adaptive capacity to pro-oxidant challenge, expressed as antioxidant induction and lesser vulnerability to enzyme inhibition...

Salt marsh macrophyte Phragmites australis strategies assessment for its dominance in mercury-contaminated coastal lagoon (Ria de Aveiro, Portugal)

Anjum, N. A.; Ahmad, I.; Valega, M.; Pacheco, M.; Figueira, E.; Duarte, A. C.; Pereira, E.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.14%
Introduction and aims The dominance of a plant species in highly metal-contaminated areas reflects its tolerance or adaptability potential to these scenarios. Hence, plants with high adaptability and/or tolerance to exceptionally high metal-contaminated scenarios may help protect environmental degradation. The present study aimed to assess the strategies adopted by common reed, Phragmites australis for its dominance in highly mercury-contaminated Ria de Aveiro coastal lagoon (Portugal). Materials and methods Both plant samples and the sediments vegetated by monospecific stand of Phragmites australis were collected in five replicates from mercury-free (reference) and contaminated sites during low tide between March 2006 and January 2007. The sediments’ physico-chemical traits, plant dry mass, uptake, partitioning, and transfer of mercury were evaluated during growing season (spring, summer, autumn, and winter) of P. australis. Redox potential and pH of the sediment around roots were measured in situ using a WTW-pH 330i meter. Dried sediments were incinerated for 4 h at 500°C for the estimation of organic matter whereas plant samples were oven-dried at 60°C till constant weight for plant dry mass determination. Mercury concentrations in sediments and plant parts were determined by atomic absorption spectrometry with thermal decomposition...

Contribution of primary producers to mercury trophic transfer in estuarine ecosystems: possible effects of eutrophication

Coelho, J. P.; Pereira, M. E.; Duarte, A. C.; Pardal, M. A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.08%
There is an ongoing eutrophication process in the Ria de Aveiro coastal lagoon (Portugal), with progressive replacement of rooted primary producers for macroalgae. Taking advantage of a well-defined environmental contamination gradient, we studied mercury accumulation and distribution in the aboveground and the belowground biomass of several salt marsh plants, including the seagrass species Zostera noltii and the dominant green macroalgal species Enteromorpha sp. The results of these experiments were then placed into the context of the estuarine mercury cycle and transport from the contaminated area. All salt marsh plants accumulated mercury in the root system, with Halimione portulacoides showing the highest levels, with up to 1.3 mg kg−1 observed in the most contaminated area. Belowground/aboveground ratios were generally below 0.4, suggesting that salt marsh plants are efficient immobilizers and retainers of mercury agents. Moreover, due to their sediment accretion capacities, salt marsh plants seem to play an important role in the sequestration of mercury in estuarine sediments. Seagrasses, on the other hand, accumulated considerable amounts of mercury in the aboveground biomass with belowground/aboveground ratios reaching as high as 1.4. These results may be due to their different routes of uptake (roots and foliar uptake) which suggests that seagrass meadows can be an important agent in the export of mercury from contaminated areas...

Mercury cycling between the water column and surface sediments in a contaminated area

Ramalhosa, E.; Segade, S. R.; Pereira, E.; Vale, C.; Duarte, A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.14%
Mercury cycling in the water column and upper sediments of a contaminated area, the Largo do Laranjo, Aveiro (Portugal), was evaluated after determination of reactive and non-reactive mercury concentrations in the water column and pore waters of sediments, collected in several places of this bay. In the water column, reactive mercury concentrations varied between 10 and 37 pmol dm−3, the highest values being observed near the mercury anthropogenic source. However, reactive mercury was a narrowly constrained fraction of the total mercury, making up only 4–16% of the total, showing evidence of the importance of dissolved organic matter on mercury transport. In sediments, higher concentrations of mercury were also determined near industrial discharges. Results indicate the existence of an equilibrium between solid and liquid phases, determined by solid sediment/pore water distribution coefficients. Much of the mercury present in the solid fraction is associated with organic matter (r=0.837) and iron oxyhydroxides (r=0.919), but as oxides begin to dissolve in reduced sediments and organic matter decays, the adsorbed mercury is released. In fact, the mercury concentrations in pore waters of those contaminated sediments largely exceeded the values determined in the water column. As molecular diffusion may contribute to the dissolved mercury distribution in the overlying water column...

Mercury contamination in the vicinity of a chlor-alkali plant and potential risks to local population

Reis, A. T.; Rodrigues, S. M.; Araújo, C.; Coelho, J. P.; Pereira, E.; Duarte, A. C.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.14%
A mercury-cell chlor-alkali plant operated in Estarreja (North-western Portugal) for 50 years causing widespread environmental contamination. Although production by this process ceased in 2002, mercury contamination from the plant remains significant. The main objective of this study was to investigate mercury impact on the nearby environment and potential risks to local population. To assess the level of contamination soil samples were collected from agricultural fields in the vicinity of the plant, extending the study by taking samples of the predominant vegetation suitable for animal and human consumption, water samples, and fish species from a nearby coastal lagoon, to gain a preliminary insight into the potential for contamination of the terrestrial and aquatic food web. To determine population exposure to mercury, hair samples were collected from local residents. Total mercury concentration in the 0–15 cm layer of soil was found to be highly variable, ranging between 0.010 and 91 mg kg− 1, although mercury contamination of soils was found to be restricted to a confined area. Lolium perenne roots contained between 0.0070 and 2.0 mg kg− 1, and there is evidence that root systems uptake mercury from the soil. Levels of mercury in the aerial parts of plants ranged between 0.018 and 0.98 mg kg− 1. It appears that plants with higher mercury concentration in soils and roots also display higher mercury concentration in leaves. Total mercury concentration in water samples ranged between 12 and 846 ng L− 1...

Mercury mobility in a salt marsh colonised by Halimione portulacoides

Valega, M.; Lillebo, A. I.; Caçador, I.; Pereira, M. E.; Duarte, A. C.; Pardal, M. A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.11%
The present study intends to increase the knowledge on the mobility of mercury in a salt marsh colonised by Halimione portulacoides. Mercury distribution in the sediment layers and its incorporation into the plant biomass were assessed, as well as the potential export of mercury from the contaminated area to the adjacent environment. Mercury pools in the sediments ranged from 560 to 943 mg m−2 and are largely associated with the solid fraction, with just a small amount being associated with the pore waters. Estimated diffusive fluxes of reactive mercury ranged from 1.3 to 103 ng m−2 d−1. Despite the above ground biomass values being comparatively higher than below ground biomass values, the mercury pools were much higher in the root system (0.06–0.16 mg m−2 and 29–102 mg m−2, respectively). The annual bioaccumulation of mercury in above ground tissues was estimated in 0.11 mg m−2 y−1, while in below ground biomass the values were higher (72 mg m−2 y−1). The turnover rates of H. portulacoides biomass suggest higher mercury mobility within the plant rhizosphere. Taking into account the pools of mercury in above ground biomass, the export of mercury by macro-detritus following the “outwelling hypothesis” is not significant for the mercury balance in the studied ecosystem. The mercury accumulated in the below ground part of the plant is quite mobile...

Mercury contamination and oxidative stress responses in the eye of wild fish (Liza aurata); Contaminação por mercúrio e respostas de stresse oxidativo nos olhos de peixes selvagens (Liza aurata)

Pereira, Ricardo Jorge Silva
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
ENG
Relevância na Pesquisa
37.09%
Every animal uses the eyes to monitor the surrounding environment and maintain homeostasis. Mercury (Hg) (including methylmercury - MeHg) is a pernicious and ubiquitous contaminant in natural waters but the assessment of its potential to interfere with fish eyes is an almost unexplored issue. This thesis will contribute to fill this knowledge gap by the evaluation of mercury accumulation in grey mullet eye wall (Liza aurata) together with the assessment of biochemical endpoints related with the oxidative stress status. This approach was complemented by the characterization of environmental contamination profiles (both in water and sediment). The study was performed at Aveiro lagoon (Portugal), where a well-established mercury historical contamination gradient provides a good background for the assessment of mercury accumulation and its toxic effects under realistic conditions. Sampling was conducted in two sites distancing around 10 km, namely: Largo do Laranjo (LAR) located in the most contaminated area, and São Jacinto (SJ) closer to the lagoon inlet and selected as reference site. Keeping in view that water temperature could affect Hg accumulated levels and biochemical responses, sampling was carried out both in winter (February 2013) and summer (June 2013). L.aurata specimens (n=20) were caught at each site/season and eye wall was removed and preserved in the field. Eye wall was analysed for total Hg and MeHg levels...

Anthropogenic Impacts on Global Storage and Emissions of Mercury from Terrestrial Soils: Insights from a New Global Model

Smith-Downey, Nicole V.; Sunderland, Elsie M.; Jacob, Daniel James
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.09%
We develop a mechanistic global model of soil mercury storage and emissions that ties the lifetime of mercury in soils to the lifetime of the organic carbon pools it is associated with. We explore the implications of considering terrestrial mercury cycling in the framework of soil carbon cycling and suggest possible avenues of future research to test our assumptions and constrain this type of model. In our simulation, input of mercury to soil is by atmospheric deposition, in part through leaf uptake and subsequent litter fall, and is moderated by surface photoreduction and revolatilization. Once bound to organic carbon, mercury is transferred along a succession of short-lived to long-lived carbon pools and is ultimately reemitted by respiration of these pools. We examine the legacy of anthropogenic influence on global mercury storage and emissions and estimate that storage of mercury in organic soils has increased by (sim20\%) since preindustrial times, while soil emissions have increased by a factor of 3 ((2900 Mg yr^{−1}) versus (1000 Mg yr^{−1})). At steady state, mercury accumulates in the most recalcitrant soil carbon pools and has an overall lifetime against respiration of 630 years. However, the impact of anthropogenic emissions since preindustrial times has been concentrated in more labile pools...

The burden of chronic mercury intoxication in artisanal small-scale gold mining in Zimbabwe: data availability and preliminary estimates

Steckling, Nadine; Bose-O’Reilly, Stephan; Pinheiro, Paulo; Plass, Dietrich; Shoko, Dennis; Drasch, Gustav; Bernaudat, Ludovic; Siebert, Uwe; Hornberg, Claudia
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.08%
Background: Artisanal small-scale gold mining (ASGM) is a poverty-driven activity practiced in over 70 countries worldwide. Zimbabwe is amongst the top ten countries using large quantities of mercury to extract gold from ore. This analysis was performed to check data availability and derive a preliminary estimate of disability-adjusted life years (DALYs) due to mercury use in ASGM in Zimbabwe. Methods: Cases of chronic mercury intoxication were identified following an algorithm using mercury-related health effects and mercury in human specimens. The sample prevalence amongst miners and controls (surveyed by the United Nations Industrial Development Organization in 2004 and the University of Munich in 2006) was determined and extrapolated to the entire population of Zimbabwe. Further epidemiological and demographic data were taken from the literature and missing data modeled with DisMod II to quantify DALYs using the methods from the Global Burden of Disease (GBD) 2004 update published by the World Health Organization (WHO). While there was no disability weight (DW) available indicating the relative disease severity of chronic mercury intoxication, the DW of a comparable disease was assigned by following the criteria 1) chronic condition...

Study of Mercury-containing Lamp Waste Management in Sub-Saharan Africa

World Bank
Fonte: Washington, DC Publicador: Washington, DC
EN_US
Relevância na Pesquisa
37.14%
The overall amount of mercury in the mercury containing lamps (MCL) market in Sub-Saharan Africa is low compared to other sources of mercury, yet it can be further reduced up-stream by improving lamp lifetime and mercury content. One of the main objectives of this report is to provide policy-makers with the knowledge and tools they need when confronted with a potentially significant flow of end of life mercury containing lamps and the potential mercury pollution it could generate, either airborne or by seeping through the ground to water bodies. The risks related to MCL waste are either low or easily controllable in the business-as-usual scenario with a domestic waste collection scheme and landfills. The design of the landfill, which should be engineered, is essential to reduce human exposure, environmental impact and associated risks. The most effective solutions to reduce overall mercury emissions, which are incineration with activated carbon filters and mercury extraction and which require a separate collection scheme...

Avaliação dos efeitos da curcumina sobre a hepatotoxicidade induzida pelo mercúrio em células humanas HepG2; Evaluation of the effects of curcumin on the hepatotoxicity induced by mercury in human HepG2 cells

Pinto, Fabio Henrique Villa
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 10/06/2015 PT
Relevância na Pesquisa
37.11%
O mercúrio é um dos metais mais nocivos presentes no ambiente, advindo tanto de fontes naturais quanto antropogênicas. Os indivíduos estão expostos a diferentes formas do mercúrio através de diversas vias, como a alimentação, principalmente no caso do metilmercúrio presente em peixes. Suas formas orgânicas são muito significativas do ponto de vista toxicológico, considerando-se a exposição da população e seus efeitos pró-oxidantes e genotóxicos envolvidos na origem de inúmeras doenças. Por outro lado, é suposto que compostos polifenólicos e outros antioxidantes da dieta podem exercer atividade protetora contra os efeitos deletérios do mercúrio. A curcumina é um pigmento amarelo polifenólico extraído do rizoma da planta Curcuma longa Linn (Zingiberaceae). Diversas evidências apontam para suas propriedades antioxidantes, de modulação da sinalização celular e alteração da expressão gênica, além da possibilidade de sua utilização na prevenção dos efeitos deletérios dos metais no organismo. Assim sendo, este trabalho teve por objetivo avaliar os efeitos da associação entre o mercúrio e a curcumina, investigando a citotoxicidade de dois compostos orgânicos de mercúrio, metilmercúrio e etilmercúrio...

Investigating the Effects of Mercury Emissions in the Four Corners Area on Local Deposition Levels and Ambient Concentrations

Weidner, Kristin
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project Formato: 6998431 bytes; application/pdf
Publicado em 11/09/2007
Relevância na Pesquisa
37.14%
In 2005, the United States Environmental Protection Agency (EPA) issued the Clean Air Mercury Rule (CAMR) as a means for regulating mercury emissions from coal-fired utility boilers in the United States. However, there is concern that this rule may result in local ‘hot spots’ of increased mercury in the environment surrounding these facilities. Citizens of the Four Corners region in the southwest are particularly concerned about this rule due to the presence of two of the highest mercury-emitting facilities in the country. While studies have shown that an increase in atmospheric levels of mercury lead to a global increase in mercury deposition, little is known on the effects air emissions from point sources on local mercury levels in the environment. In this study, mercury emissions from the Four Corners Power Plant and the San Juan Generating Station of New Mexico were investigated for their possible impacts on local mercury levels in the environment. The analysis included statistical and back trajectory analysis of deposition data at a nearby monitoring site, as well as SCREEN dispersion modeling of mercury emissions to calculate mercury concentrations in the ambient air. Results of the statistical analysis of the deposition data showed a relationship between precipitation and deposition levels...

Sources and Biogeochemical Transformation of Mercury in Aquatic Ecosystems

Deonarine, Amrika
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2011
Relevância na Pesquisa
37.22%

Mercury contamination in aquatic ecosystems is a concern as anaerobic aquatic sediments are the primary regions of methylmercury production in freshwater and coastal regions. Methlymercury is a bioaccumulative neurotoxin, and human exposure to methylmercury can result in impaired functioning of the central nervous system and developmental disabilities in children. To minimize the risk of human exposure to methylmercury, it is important to be knowledgeable of the various sources which can supply mercury to aquatic ecosystems as well as have a complete understanding of the biogeochemical processes which are involved in methylmercury production in aquatic systems. In this dissertation work, both mercury biogeochemical speciation in anaerobic aquatic sediments and sources of mercury to aquatic systems were addressed.

The biogeochemical speciation of mercury is a critical factor which influences the fate and transformation of mercury in aquatic environments. In anaerobic sediments, mercury chemical speciation is controlled by reduced sulfur groups, such as inorganic sulfide and reduced sulfur moieties in dissolved organic matter (DOM). The formation of mercury sulfide nanoparticles through stabilization by dissolved organic matter (DOM) was investigated in precipitation studies using dynamic light scattering. Mercury sulfide nanoparticles (particle diameter < 100 nm) were stabilized through precipitation reactions that were kinetically hindered by DOM. To further investigate the interaction between DOM and metal sulfides...

Total mercury in terrestrial systems (air-soil-plant-water) at the mining region of San Joaquín, Queretaro, Mexico

Martínez-Trinidad,Sergio; Hernández Silva,Gilberto; Ramírez Islas,Martha Elena; Martínez Reyes,Juventino; Solorio Munguía,Gregorio; Solís Valdez,Sara; García Martínez,Rocío
Fonte: Instituto de Geofísica, UNAM Publicador: Instituto de Geofísica, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2013 EN
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37.09%
Deficient management of cinnabar mining left the San Joaquín region with high concentrations of mercury in its soils (2.4 - 4164 mg kg-1). Numerous cinnabar mines have contributed to the dispersion of mercury into agricultural (0.5 - 314 mg kg-1) and forest (0.2 - 69 mg kg-1) soils. Sediments are a natural means of transportation for mercury, causing its spreading, especially in areas near mine entrances (0.6 - 687 mg kg-1). The nearness of maize crops to mines favors mercury accumulation in the different plant structures, such as roots, stems, leaves, and grain (0.04 - 8.2 mg kg-1); these being related to mercury volatilization and accumulation in soils. Mercury vapor present in the settlements could indicate a constant volatilization from lands and soils (22 - 153 ng m-3). The mercury levels found in the soils, in maize grain, and in the air resulted greater than the standards reported by the Official Mexican Norm (NOM) and the World Health Organization (WHO). Mercury in rainwater is due mainly to the presence of suspended atmospheric particles, later deposited on the surface (1.5 - 339 µg l-1). Mercury dissolution was found in the drinking water (10 - 170 ng l-1), with concentrations below those established by the NOM and the WHO. The contamination existing in the San Joaquín region does not reach the levels of the world's greatest mercury producers: Almaden (Spain) and Idrija (Slovenia). It is...