Magnetic isotope effect for mercury nuclei in photolysis of bis(p-trifluoromethylbenzyl)mercury

Buchachenko, A. L.; Иванов, В. Л.; Roznyatovskii, V. A.; Artamkina, G. A.; Vorob'ev, A. Kh.; Ustynyuk, Yu. A.

doi:10.1134/s0012501607030013

Cited by 39 publications

(35 citation statements)

References 5 publications

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“…This minimization should occur in order for HFC to be dominant and to cause manifestation of significant magnetic effects. On the other hand, significant MIF of Hg during photochemical transformations, as recently observed by two groups Buchachenko et al, 2007), and likely caused due to magnetic effects, can possibly be explained by a number of characteristics of photon induced transformations. Unlike biological pathways, which in the absence of light would lead to formation of singlet states, photon absorption permits efficient formation of triplet state radical pairs (Grissom, 1995).…”

Section: Absence Of Mif During Other 'Dark' Biological Hg Transformatmentioning

confidence: 94%

Mass dependent stable isotope fractionation of mercury during mer mediated microbial degradation of monomethylmercury

Kritee

Barkay

Blum

2009

Geochimica et Cosmochimica Acta

192

211

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Controlling bioaccumulation of toxic monomethylmercury (MMHg) in aquatic food chains requires differentiation between biotic and abiotic pathways that lead to its production and degradation. Recent mercury (Hg) stable isotope measurements of natural samples suggest that Hg isotope ratios can be a powerful proxy for tracing dominant Hg transforming pathways in aquatic ecosystems. Specifically, it has been shown that photo-degradation of MMHg causes both mass dependent (MDF) and mass independent fractionation (MIF) of Hg isotopes. Because the extent of MDF and MIF observed in natural samples (e.g., fish, soil and sediments) can potentially be used to determine the relative importance of pathways leading to MMHg accumulation, it is important to determine the potential role of microbial pathways in contributing to the fractionation, especially MIF, observed in these samples. This study reports the extent of fractionation of Hg stable isotopes during degradation of MMHg to volatile elemental Hg and methane via the microbial Hg resistance (mer) pathway in Escherichia coli carrying a mercury resistance (mer) genetic system on a multi-copy plasmid. During experimental microbial degradation of MMHg, MMHg remaining in reactors became progressively heavier (increasing d 202 Hg) with time and underwent mass dependent Rayleigh fractionation with a fractionation factor a 202/198 = 1.0004 ± 0.0002 (2SD). However, MIF was not observed in any of the microbial MMHg degradation experiments indicating that the isotopic signature left by mer mediated MMHg degradation is significantly different from fractionation observed during DOC mediated photo-degradation of MMHg. Additionally, a clear suppression of Hg isotope fractionation, both during reduction of Hg(II) and degradation of MMHg, was observed when the cell densities increased, possibly due to a reduction in substrate bioavailability. We propose a multi-step framework for understanding the extent of fractionation seen in our MMHg degradation experiments and, based on estimates of the rates of the various steps involved in this mer mediated pathway, suggest which steps in the process could contribute towards the observed extent of fractionation. This framework suggests that at lower cell densities catalysis by MerB was the rate limiting step while at higher cell densities transport into the cell, which does not cause fractionation, became the rate limiting step. In addition to presenting evidence for absence of MIF during mer mediated Hg transformations, based on the nature of Hg compounds and microbe-Hg interactions, we suggest that the nuclear spin dependent MIF (i.e., the magnetic isotope effect) is also unlikely to occur during other non mer mediated 'dark' microbial Hg transformations (e.g., formation of MMHg and oxidative degradation of MMHg). Because of the important implications of the absence of MIF during biological processes on Hg isotope systematics, we discuss theoretical considerations and experimental strategies that could be used to confirm this suggestion.

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Section: Absence Of Mif During Other 'Dark' Biological Hg Transformatmentioning

confidence: 94%

Mass dependent stable isotope fractionation of mercury during mer mediated microbial degradation of monomethylmercury

Kritee

Barkay

Blum

2009

Geochimica et Cosmochimica Acta

192

211

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“…The magnetic isotope effect for mercury has been investigated and claimed to be observed in the reaction of kreatine kinase and methylmercury by gas source mass spectrometry (Buchachenko et al, 2004) and in the photolysis of Bis(p-trifluoromethylbenzyl)mercury by nuclear magnetic resonance (Buchachenko et al, 2007). Hg isotope fractionation during photoreduction of Hg 2+ and MeHg in the presence of dissolved organic carbon (DOC) in aqueous solution was conducted by Bergquist and Blum (2007) using CV-MC-ICP-MS and showed 199 Hg and 201 Hg isotope enrichment for mercury remaining in solution relative to MDF.…”

Section: Isotope Fractionation Lawsmentioning

confidence: 99%

“…Recent works denoted significant non-mass-dependent fractionation (NMF) of the odd isotopes ( 199 Hg and 201 Hg) of mercury in biogeological samples (Jackson et al, 2006;Bergquist and Blum, 2007;Epov et al, 2008;Biswas et al, 2008;Ghosh et al 2008;Jackson et al, 2008). In contrast to MDF, which is governed by chemical energy of the starting and transition states of reactant molecules, NMF reported on Hg isotopes in experimental and natural processes have been suggested to result from either magnetic interactions (magnetic isotope effect) (Buchachenko et al, 2004;Bergquist and Blum, 2007;Buchachenko et al, 2007) or from nuclear volume effects (also known as nuclear field shift effect) (Schauble, 2007).…”

Section: Introductionmentioning

confidence: 95%

Mercury isotope fractionation during liquid–vapor evaporation experiments

Estrade

Carignan

Sonke

et al. 2009

Geochimica et Cosmochimica Acta

246

249

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“…Hg), the combined result of nuclear volume effect (NVE) and magnetic isotope effect (MIE), can provide additional insight to Hg biogeochemical cycling (Schauble, 2007;Buchachenko et al, 2007). Laboratory experiments quantifying elemental Hg 0 volatilization (Estrade et al, 2009;Ghosh et al, 2013), equilibrium Hg-thiol complexation (Wiederhold et al, 2010), and dark aqueous Hg(II) reduction (Zheng and Hintelmann, 2010a) Hg ranging from 1.00 to 1.30 Hintelmann, 2009, 2010b;Rose et al, 2015;Chandan et al, 2014).…”

mentioning

confidence: 99%

Sedimentary records of mercury stable isotopes in Lake Michigan

Yin

Lepak

Krabbenhoft

et al. 2016

Elementa: Science of the Anthropocene

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Mercury (Hg) concentrations and Hg isotopic composition were investigated in three sediment cores in Lake Michigan (LM). Two cores were collected from Green Bay, a region heavily impacted by Hg contamination and one core from an offshore region of LM absent of direct point source Hg. Historical trends of Hg influxes suggest increased Hg deposition began in the 1890s in Green Bay and in the early 1800's in offshore LM. Recently deposited sediment reflecting more anthropogenic influence shows similar d202 Hg values (-1.0 to -0.5‰) for all three cores however, deep core sediments, reflecting pre-industrial eras, show much lower d 202Hg values (-1.7 to -1.2‰). Using a binary mixing model based on d 202Hg signatures, the proportion of anthropogenic Hg was estimated. Model output confirms that Green Bay is more contaminated by local point source than the offshore LM. An increase in positive D199 Hg values (-0.02 to +0.27‰) was observed from inner Green Bay to the offshore of LM, which may indicate increased input of atmospheric Hg and decreased watershed inputs along this transect. Overall, this study suggests that sedimentary Hg isotopes maybe a useful tracer in understanding Hg sources and history of Hg contamination in large lakes.

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Magnetic isotope effect for mercury nuclei in photolysis of bis(p-trifluoromethylbenzyl)mercury

Cited by 39 publications

References 5 publications

Mass dependent stable isotope fractionation of mercury during mer mediated microbial degradation of monomethylmercury

Mass dependent stable isotope fractionation of mercury during mer mediated microbial degradation of monomethylmercury

Mercury isotope fractionation during liquid–vapor evaporation experiments

Sedimentary records of mercury stable isotopes in Lake Michigan

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