Mass-independent fractionation of Hg isotopes by biological processes

Jackson, Togwell A.; Whittle, D. Michael; Evans, Michael S.; Muir, Derek C. G.

doi:10.1016/j.gca.2006.06.577

Cited by 7 publications

(14 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In accordance with my previous work on Hg isotopes , 202 Hg was used as the denominator in the calculation of Hg isotope ratios because it is the most abundant isotope and therefore gives the highest precision (lowest analytical error) in analyses performed by the methods employed in my research. This procedure conforms to the customary practice of using the most abundant isotope of an element as the denominator when reporting values of isotope ratios of the element.…”

Section: Methodsmentioning

confidence: 88%

See 1 more Smart Citation

Isotopic and chemical characteristics of mercury in organs and tissues of fish in a mercury‐polluted lake: Evidence for fractionation of mercury isotopes by physiological processes

Jackson

2017

Enviro Toxic and Chemistry

View full text Add to dashboard Cite

Organs and tissues of whitefish and trout from mercury (Hg)-polluted Lake Ontario were analyzed for Hg isotopes, methylmercury (CH Hg ), and inorganic Hg to investigate possible mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes by physiological processes of the fish. Isotope signatures of different body parts were defined by δ-values of Hg/ Hg, Hg/ Hg, Hg/ Hg, and Hg/ Hg ratios and by Δ-values representing effects of MIF on Hg/ Hg and Hg/ Hg ratios. The research yielded the following evidence for MDF and MIF, including MIF of isotopes with even as well as odd mass numbers, by metabolic activities: 1) anomalously low δ-values for whitefish kidneys but not for trout kidneys; 2) widely varying differences between the δ-values of different body parts of whitefish but practically uniform differences for those of trout; 3) different relationships between Δ Hg and Δ Hg for whitefish than for trout; 4) nonlinear correlation between δ Hg and δ Hg for whitefish but linear correlation for trout; 5) an inverse correlation between the δ Hg values and CH Hg concentrations of whitefish and trout; 6) an inverse correlation between the δ Hg/δ Hg and CH Hg /inorganic Hg ratios of trout kidneys and gills (and lipids of trout near the sources of pollution) but a positive correlation for muscle, liver, and gut; and 7) inverse correlations between Δ Hg and the CH Hg /inorganic Hg ratio for trout liver, kidneys, and gut. Environ Toxicol Chem 2018;37:515-529. © 2017 SETAC.

show abstract

Section: Methodsmentioning

confidence: 88%

“…Analysis of CH 3 Hg þ and inorganic Hg extracted from fish proved that the anomalies were mostly confined to the CH 3 Hg þ fraction [9]. The discovery of the apparently universal occurrence of anomalous 199 Hg and 201 Hg enrichment in fish [9,21,22] has been confirmed independently many times [17,[24][25][26][27].…”

Section: Introductionmentioning

confidence: 96%

Isotopic and chemical characteristics of mercury in organs and tissues of fish in a mercury‐polluted lake: Evidence for fractionation of mercury isotopes by physiological processes

Jackson

2017

Enviro Toxic and Chemistry

View full text Add to dashboard Cite

show abstract

“…For massdependent fractionation (MDF), only one delta value needs to be reported and we suggest 202 Hg. Mass-independent fractionation (MIF) of the odd-mass Hg isotopes has also been observed in aquatic systems (Jackson et al, 2006;Bergquist et al, 2006) and requires additional nomenclature. Following the convention used for MIF of O and S we report MIF as the deviation in isotope ratios from the theoretical mass dependent kinetic isotope fractionation ( xxx Hg).…”

Section: Regulation Of Acidity Generation and Consumption In Sedimentmentioning

confidence: 99%

“…Hg isotope analysis by MC-ICPMS is an important new tool for identifying Hg sources and tracking Hg transformations in the environment (Smith et al, 2005; Jackson et al, 2006; Bergquist et al, 2006;Kritee et al, 2007), with most measured natural samples displaying mass-dependent isotope fractionation (MDF). A small body of data suggests that natural samples also display massindependent isotope fractionation (MIF) of the odd Hg isotopes(Jackson et al, 2006;Bergquist et al, 2006).…”

mentioning

confidence: 99%

Goldschmidt Abstracts 2007- B

2007

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

Both dynamic and static recrystallization of serpentinite to soapstone have been reported from ultramafic massifs in the oceans. While the development of talceous schists is common in detachment faults that are loci of large time-integrated fluid fluxes, static replacement of serpentine by talc is more difficult to explain. We report on observations made in ODP drill core from Leg 209, Hole 1268, at the Mid-Atlantic Ridge (MAR) 15°N, where soapstone is abundant. Talc appears in blackwalls at the contact to small (<10 m) gabbroic units, but the majority of soapstone is not formed diffusively at mafic/ultramafic contacts. Static replacement of serpentinite by talc starts along anastomosing vein networks and continues to pervasive steatitization, during which the serpentine hourglass texture is preserved. To transform magnesian serpentine (Mg/Si=1.5) to talc (Mg/Si=0.75) massive removal of Mg or addition of Si is required. As the solubility of Mg is very low in fluids with pH>3, metasomatic enrichment of silica seems the most likely explanation. It appears that, except for obvious blackwalls, this metasomatism was facilitated by ingress of aqueous fluids. Serpentinite in Hole 1268 does not contain any brucite, suggesting that even the serpentinite has undergone silica metasomatism, as the precursor harzburgites and dunites had <15-20% orthopyroxene so that brucite would be expected to form during isochemical serpentinization. Gabbros in Hole 1268 do also show evidence for interactions with fluids with high silica activities since they are not rodingized but instead show common greenschist alteration to chlorite, albite, and actinolite. This is unlike other drill holes in the MAR 15°N area and elsewhere, where brucite-bearing serpentinites host rodingitized gabboic dikes.We propose two possible explanations for the variability in aqueous fluid silica activity suggested by the phase assemblages of oceanic metaperidotites. (1) They are a result of the variable distribution of mafic units in a composite mafic/ultramafic crust, or (2) they are a consequence of the temperature-dependent reaction sequences taking place along the fluid flow path. To further explore the second possibility, we conducted isobaric (500 bar) geochemical model calculation. At temperatures >350°C, olivine is stable and hydration of pyroxenes imposes high silica activities to the fluids. Low aqueous silica activities can only develop at temperatures <<350°C, in particular when fluid pH is high due to the hydrolysis of olivine. Brucite-bearing serpentinite as well as rodingite are expected to form under those conditions. Steatitization, in contrast, requires two condi-tions: high fluid flux and high silica activities. Sulfide assemblages in Hole 1268 suggest that oxygen and sulfur fugacities were high during silica metasomatism, which is consistent with our geochemical model predictions of coupled decreases in H 2 fugacity and pH with increasing fluid flux.The number of factors affecting metal fluxes within hydrothermal systems is large and the evol...

show abstract

“…Since then, numerous studies have charted the large variation in natural mass-dependent fractionation (MDF) of Hg isotopes ($1.75&/amu) and the processes that govern them (Lauretta et al, 2001;Hintelmann and Lu, 2003;Jackson et al, 2004;Smith et al, 2005;Xie et al, 2005;Foucher and Hintelmann, 2006;Kritee et al, 2007;Zheng et al, 2007;Smith et al, 2008;Sonke et al, 2008;Zambardi et al, 2008). 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: 99%