Mercury in Natural Waters: A Mini-Review

Mousavi, Aliyar; Chávez, Rose D.; Ali, Abdul-Mehdi S.; Cabaniss, Stephen E.

doi:10.1080/15275922.2010.547549

Cited by 49 publications

(36 citation statements)

References 21 publications

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“…Hg(II) is water soluble but sorbs strongly onto iron oxides and interacts with dissolved organic matter (7). Hg(0), the least toxic form, is both a liquid and a gas at room temperature and can evaporate from surface waters and soils (8,9).…”

mentioning

confidence: 99%

Mercury Reduction and Methyl Mercury Degradation by the Soil Bacterium Xanthobacter autotrophicus Py2

Petrus

Rutner

Liu

et al. 2015

Appl Environ Microbiol

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Two previously uncharacterized potential broad-spectrum mercury (Hg) resistance operons (mer) are present on the chromosome of the soil Alphaproteobacteria Xanthobacter autotrophicus Py2. These operons, mer1 and mer2, contain two features which are commonly found in mer operons in the genomes of soil and marine Alphaproteobacteria, but are not present in previously characterized mer operons: a gene for the mercuric reductase (MerA) that encodes an alkylmercury lyase domain typical of those found on the MerB protein, and the presence of an additional gene, which we are calling merK, with homology to glutathione reductase. Here, we demonstrate that Py2 is resistant to 0.2 M inorganic mercury [Hg(II)] and 0.05 M methylmercury (MeHg). Py2 is capable of converting MeHg and Hg(II) to elemental mercury [Hg(0)], and reduction of Hg(II) is induced by incubation in sub toxic concentrations of Hg(II). Transcription of the merA genes increased with Hg(II) treatment, and in both operons merK resides on the same polycistronic mRNA as merA. We propose the use of Py2 as a model system for studying the contribution of mer to Hg mobility in soil and marine ecosystems. Bacterial mercury (Hg) resistance genes (mer) are important drivers in the biogeochemical cycle of Hg. These operons catalyze the conversion of inorganic mercury [Hg(II)] and sometimes methylmercury (MeHg) to elemental mercury [Hg(0)] (1). MeHg, which is more toxic than Hg(II) or Hg(0), is the form that biomagnifies in aquatic food webs (2, 3) and can cause toxicity to humans and animals that consume contaminated fish (4-6). Hg(II) is water soluble but sorbs strongly onto iron oxides and interacts with dissolved organic matter (7). Hg(0), the least toxic form, is both a liquid and a gas at room temperature and can evaporate from surface waters and soils (8, 9).All mer operons contain a gene encoding mercuric reductase, MerA, which converts Hg(II) to Hg(0), thereby conferring resistance (10). Some mer operons, called broad-spectrum mer operons, contain an additional gene encoding MerB, or alkylmercury lyase (AML), which degrades MeHg to Hg(II) and methane (11). Many mer operons contain genes for the transcriptional regulators MerR and MerD (12), as well the Hg transporters encoded by merT, merC, and merF, as well as additional Hg transfer proteins encoded by merP and merE (11, 13). Regulation of mer and the enzymatic activity of MerA is known in great detail for some operons and enzymes (10).It has been demonstrated that mer can influence the Hg cycle in lakes (14), but at present we know much less about the contribution of mer to the Hg cycle in soil and the terrestrial subsurface. It was long thought that Hg was relatively immobile in the subsurface due to sorption on sediment components such as iron oxides (1), but this assumption has come under scrutiny, since Hg has been unexpectedly found in groundwater at numerous sites, such as the Kirkwood-Cohansey aquifer in New Jersey (15, 16), the Waquoit Bay near Cape Cod, MA (17), and the coasts of California, northern ...

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mentioning

confidence: 99%

Mercury Reduction and Methyl Mercury Degradation by the Soil Bacterium Xanthobacter autotrophicus Py2

Petrus

Rutner

Liu

et al. 2015

Appl Environ Microbiol

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“…The cycle is completed by the incorporation of mercury species in precipitation, bioconversion into volatile and soluble forms, release to the atmosphere or bioaccumulation in aquatic organisms. [6][7][8] The toxicity of mercury is one of the main reasons for scientific investigation of its behavior. In the Amazon region, Branches et al 9 identified symptoms such as vertigo, palpitations, headaches and trembling in patients exposed to mercury vapor.…”

Section: Introductionmentioning

confidence: 99%

Influence of seasonality on the interaction of mercury with aquatic humic substances extracted from the Middle Negro River Basin (Amazon)

Oliveira¹,

Botero²,

Santos³

et al. 2012

J. Braz. Chem. Soc.

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As elevadas concentrações de mercúrio em diferentes matrizes ambientais na Amazônia têm sido atribuídas a atividades mineradoras. Entretanto, altas concentrações de mercúrio também estão presentes no solo e na água em locais como a Bacia do médio Rio Negro, distantes de fontes emissoras antropogênicas. A região Amazônica é caracterizada por dois diferentes regimes sazonais, bem definidos em períodos de cheias e vazantes. O objetivo deste trabalho foi investigar as influências sazonais na interação entre mercúrio e substâncias húmicas aquáticas (AHS), que são os principais complexantes orgânicos naturais. Os resultados obtidos por análise estatística multivariada dos dados mostraram que as substâncias húmicas possuem diferentes características estruturais, dependendo do período sazonal. A capacidade das substâncias húmicas em formar complexos com Hg(II) não está diretamente relacionada ao seu teor de carbono, mas sim à natureza e disponibilidade dos grupos funcionais presentes em sua estrutura. Os grupos funcionais carboxílicos e aromáticos estão diretamente relacionados à maior capacidade de complexação de AHS por íons mercúrio.High mercury concentrations in different environmental matrices in the Amazon have been attributed to mining activities. However, high concentrations of mercury are also present in the soil and water in places like in the middle of the Negro River Basin, which is far away from any anthropogenic emission sources. The Amazon region is characterized by two different regional seasons, with well-defined flood and low water periods. The objective of this work was to investigate the seasonal influences of the interaction between mercury and aquatic humic substances (AHS), which are the main agents of the natural organic complexation capacity. The results of the multivariate statistical analysis of the data showed that the humic substances had different structural characteristics, depending on each season. The ability of humic substances to form complexes with Hg(II) is not directly related to their carbon content, but to the nature and availability of the functional groups present in its structure. The functional groups are carboxylic and aromatic directly related to the higher complexation capacity of AHS by mercury ions.

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“…methylmercury) is predominant and has a high propensity to accumulate in fish tissue through ingestion and absorption (Beyrouty & Chan, 2006). Therefore, dietary consumption of fish and other aquatic animals is a major route o f Hg exposure amongst human and wildlife populations (Mousavi et al, 2011) and the effects of high Hg exposure are well documented (Beyrouty & Chan, 2006).…”

Section: Background and Context Of The Studymentioning

confidence: 99%

“…Hg is third (after arsenic and lead) on the 2011 Agency for Toxic Substances and Disease Registry (ATSDR) priority list of 275 hazardous substances, which includes substances that present the most significant potential threats to human health in the United States 1 (ATSDR, 2011). It is released into the environment through both natural and anthropogenic sources and can exist in three forms: elemental, inorganic, and organic (Bhavsar, 2010;Mousavi et al, 2011). In freshwater ecosystems, the organic form (e.g.…”

Section: Background and Context Of The Studymentioning

confidence: 99%

“…Due to its high toxicity to both humans and animals, Hg is one o f the most commonly studied trace elements in the environment (Mousavi et al, 2011). Hg is third (after arsenic and lead) on the 2011 Agency for Toxic Substances and Disease Registry (ATSDR) priority list of 275 hazardous substances, which includes substances that present the most significant potential threats to human health in the United States 1 (ATSDR, 2011).…”

Section: Background and Context Of The Studymentioning

confidence: 99%

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Development of a risk assessment tool for mercury in fish.

Pahal¹

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Mercury in Natural Waters: A Mini-Review

Cited by 49 publications

References 21 publications

Mercury Reduction and Methyl Mercury Degradation by the Soil Bacterium Xanthobacter autotrophicus Py2

Mercury Reduction and Methyl Mercury Degradation by the Soil Bacterium Xanthobacter autotrophicus Py2

Influence of seasonality on the interaction of mercury with aquatic humic substances extracted from the Middle Negro River Basin (Amazon)

Development of a risk assessment tool for mercury in fish.

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