Microbial mercury methylation in Antarctic sea ice

Gionfriddo, Caitlin M.; Tate, Michael T.; Wick, Ryan R.; Schultz, Mark B.; Zemła, Adam; Thelen, Michael P.; Schofield, Robyn; Krabbenhoft, David P.; Holt, Kathryn E.; Moreau, John W.

doi:10.1038/nmicrobiol.2016.127

Cited by 154 publications

(184 citation statements)

References 84 publications

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“…Capturing the seasonality of atmospheric Hg in the Arctic using GEOSChem required parameterization of unique sea ice, oceanic, and riverine dynamics (Fisher et al, , 2013Y. Zhang et al, 2015); a similar analysis for the Southern Ocean region, with its distinct productivity dynamics impacting Hg cycling (e.g., Cossa et al, 2011;Gionfriddo et al, 2016), has not yet been performed.…”

Section: Seasonalitymentioning

confidence: 99%

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

et al. 2017

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Abstract. Mercury (Hg) is emitted to the atmosphere mainly as volatile elemental Hg 0 . Oxidation to water-soluble Hg II plays a major role in Hg deposition to ecosystems. Here, we implement a new mechanism for atmospheric Hg 0 / Hg II redox chemistry in the GEOS-Chem global model and examine the implications for the global atmospheric Hg budget and deposition patterns. Our simulation includes a new coupling of GEOS-Chem to an ocean general circulation model (MITgcm), enabling a global 3-D representation of atmosphereocean Hg 0 / Hg II cycling. We find that atomic bromine (Br) of marine organobromine origin is the main atmospheric Hg 0 oxidant and that second-stage HgBr oxidation is mainly by the NO 2 and HO 2 radicals. The resulting chemical lifetime of tropospheric Hg 0 against oxidation is 2.7 months, shorter than in previous models. Fast Hg II atmospheric reduction must occur in order to match the ∼ 6-month lifetime of Hg against deposition implied by the observed atmospheric variability of total gaseous mercury (TGM ≡ Hg 0 + Hg II (g)). We implement this reduction in GEOS-Chem as photolysis of aqueous-phase Hg II -organic complexes in aerosols and clouds, resulting in a TGM lifetime of 5.2 months against deposition and matching both mean observed TGM and its variability. Model sensitivity analysis shows that the interhemispheric gradient of TGM, previously used to infer a longer Hg lifetime against deposition, is misleading because Southern Hemisphere Hg mainly originates from oceanic emissions rather than transport from the Northern Hemisphere.The model reproduces the observed seasonal TGM variation at northern midlatitudes (maximum in February, minimum in September) driven by chemistry and oceanic evasion, but it does not reproduce the lack of seasonality observed at southern hemispheric marine sites. Aircraft observations in the lowermost stratosphere show a strong TGM-ozone relationship indicative of fast Hg 0 oxidation, but we show that this relationship provides only a weak test of Hg chemistry because it is also influenced by mixing. The model reproduces observed Hg wet deposition fluxes over North America, Europe, and China with little bias (0-30 %). It reproduces qualitatively the observed maximum in US deposition around the Gulf of Mexico, reflecting a combination of deep convection and availability of NO 2 and HO 2 radicals for second-stage HgBr oxidation. However, the magnitude of this maximum is underestimated. The relatively low observed Hg wet deposition over rural China is attributed to fast Hg II reduction in the presence of high organic aerosol concentrations. We find that 80 % of Hg II deposition is to the global oceans, reflecting the marine origin of Br and low concentrations of organic aerosols for Hg II reduction. Most of that deposition takes place to the tropical oceans due to the availability of HO 2 and NO 2 for second-stage HgBr oxidation.

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Section: Seasonalitymentioning

confidence: 99%

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

et al. 2017

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“…However, significant positive correlations have been found between K meth and %MeHg in many environments (Drott et al 2008), and %MeHg values in boreal wetlands tracked the ratio of K meth to K demeth (Tjerngren et al 2012a), suggesting that if both rates are measured, steady state net MeHg production rates can be estimated. Very recently, measurements of potential rates have been replaced with measurements of the genetic potential of the microbial community (e.g., Gionfriddo et al 2016) due to the recent discovery of a gene cluster responsible for mercury methylation (see below), and developments in this area will be useful in addressing many of the questions previously addressed using the measurements of potential rates. While methylation may occur abiotically in some environments (Celo et al 2006;Eckley and Hintelmann 2006;Monperrus et al 2007a;Perrot et al 2013), biotic methylation by microbes is the primary source of MeHg in aquatic environments.…”

Section: Why Is Net Methylmercury Production Important and How It Is mentioning

confidence: 99%

“…In fact, studies using molecular techniques to directly examine potential sites of methylation are currently being published. For example, Gionfriddo et al (2016) have identified Antarctic sea ice as a possible environment conducive to the growth of a marine microaerophilic bacterium (Nitrospina) by isolating the hgcAB genes Sulfate reducing bacteria inhibitors (Compeau and Bartha 1985;Kerry et al 1991;Gilmour et al 1992;Choi and Bartha 1993;Choi et al 1994) Correlations with SO 4 concentrations (Devereux 1996;King et al 1999; Eckley and Hintelmann 2006) Presence of hgc gene cluster Parks et al 2013;Sonke et al 2013;Podar et al 2015) Stable isotope assays only Bacteria Deltaproteobacteria Geobacter metallireducens Desulfuromonas palmitatis Geobacter hydrogenophilus Geobacter sulfurreducens Where does methylation occur?…”

Section: Why Is Net Methylmercury Production Important and How It Is mentioning

confidence: 99%

Recent advances in the study of mercury methylation in aquatic systems

Paranjape

Hall

2017

FACETS

117

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With increasing input of neurotoxic mercury to environments as a result of anthropogenic activity, it has become imperative to examine how mercury may enter biotic systems through its methylation to bioavailable forms in aquatic environments. Recent development of stable isotope-based methods in methylation studies has enabled a better understanding of the factors controlling methylation in aquatic systems. In addition, the identification and tracking of the hgcAB gene cluster, which is necessary for methylation, has broadened the range of known methylators and methylation-conducive environments. Study of abiotic factors in methylation with new molecular methods (the use of stable isotopes and genomic methods) has helped elucidate the confounding influences of many environmental factors, as these methods enable the examination of their direct effects instead of merely correlative observations. Such developments will be helpful in the finer characterization of mercury biogeochemical cycles, which will enable better predictions of the potential effects of climate change on mercury methylation in aquatic systems and, by extension, the threat this may pose to biota.

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“…Being contrary to organic degradation, mercury is not biodegradable and can be bio‐accumulated along the food chain. Hg(II) is a solvated ion with high cellular toxicity and carcinogenic potential and becomes stronger toxicity speciation through microbial mercury methylation even in polar marine environments (Gionfriddo et al, ). These organic mercury speciations contain methylmercury, ethylmercury, and phenylmercury.…”

Section: Introductionmentioning

confidence: 99%

“…cellular toxicity and carcinogenic potential and becomes stronger toxicity speciation through microbial mercury methylation even in polar marine environments (Gionfriddo et al, 2016). These organic mercury speciations contain methylmercury, ethylmercury, and phenylmercury.…”

mentioning

confidence: 99%

Development and optimization of an immunoassay for the detection of Hg(II) in lake water

Jin

et al. 2019

Food Science & Nutrition

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In this paper, an indirect competitive enzyme‐linked immunosorbent assay (IC‐ELISA) has been developed and optimized to detect Hg(II) in tap water and lake water based on a monoclonal antibody (mAb‐A24). Some stabilizing additives (Gelatin, bovine serum albumin [BSA], polyvinyl alcohol [PVA], and polyvinyl pyrrolidone [PVP]) and surfactant (Tween‐20) have been investigated thoroughly in the optimization process. Under the optimal condition, the 50% half maximal inhibitory concentration (IC 50 ) and limit of detection (LOD) were 1.68 and 0.079 ng/ml, respectively. These anti‐Hg mAbs also have some affinity with methyl mercury (CH 3 Hg) and with no cross‐reactivity with other thirteen metal ions. The developed method has shown satisfactory recovery of Hg(II), ranged between 91% and 116%, from tap water and lake water. Therefore, this immunoassay can be used to detect trace Hg(II) in environment water.

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Microbial mercury methylation in Antarctic sea ice

Cited by 154 publications

References 84 publications

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

Recent advances in the study of mercury methylation in aquatic systems

Development and optimization of an immunoassay for the detection of Hg(II) in lake water

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