Aqueous phase methylation as a potential source of methylmercury in wet deposition

Hammerschmidt, Chad R.; Lamborg, Carl H.; Fitzgerald, William F.

doi:10.1016/j.atmosenv.2006.10.032

Cited by 83 publications

(44 citation statements)

References 41 publications

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“…Supersaturation of Arctic surface seawater over a wide area by DMHg [19,29] and the presence of elevated GEM in the marine boundary layer in areas rich in sea ice [26] point to the potential importance of this process in the Arctic MeHg cycle. Other possible mechanisms of MeHg production, such as methylation of Hg II through abiotic processes, [151] by microbial activity, or by aqueous phase methylation in the atmosphere [152] may occur. These processes have been investigated in temperate locations [153] but their significance in the Arctic is unknown.…”

Section: Controls On Arctic Food Chain Mercury Accumulation By Methylmentioning

confidence: 99%

The fate of mercury in Arctic terrestrial and aquatic ecosystems, a review

Douglas

Loseto²,

Macdonald³

et al. 2012

Environ. Chem.

119

147

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Environmental context. Mercury, in its methylated form, is a neurotoxin that biomagnifies in marine and terrestrial foodwebs leading to elevated levels in fish and fish-eating mammals worldwide, including at numerous Arctic locations. Elevated mercury concentrations in Arctic country foods present a significant exposure risk to Arctic people. We present a detailed review of the fate of mercury in Arctic terrestrial and marine ecosystems, taking into account the extreme seasonality of Arctic ecosystems and the unique processes associated with sea ice and Arctic hydrology.Abstract. This review is the result of a series of multidisciplinary meetings organised by the Arctic Monitoring and Assessment Programme as part of their 2011 Assessment 'Mercury in the Arctic'. This paper presents the state-of-the-art knowledge on the environmental fate of mercury following its entry into the Arctic by oceanic, atmospheric and terrestrial pathways. Our focus is on the movement, transformation and bioaccumulation of Hg in aquatic (marine and fresh water) and terrestrial ecosystems. The processes most relevant to biological Hg uptake and the potential risk associated with Hg exposure in wildlife are emphasised. We present discussions of the chemical transformations of newly deposited or transported Hg in marine, fresh water and terrestrial environments and of the movement of Hg from air, soil and water environmental compartments into food webs. Methylation, a key process controlling the fate of Hg in most ecosystems, and the role of trophic processes in controlling Hg in higher order animals are also included. Case studies on Eastern Beaufort Sea beluga (Delphinapterus leucas) and landlocked Arctic char (Salvelinus alpinus) are presented as examples of the relationship between ecosystem trophic processes and biologic Hg levels. We examine whether atmospheric mercury depletion events (AMDEs) contribute to increased Hg levels in Arctic biota and provide information on the links between organic carbon and Hg speciation, dynamics and bioavailability. Long-term sequestration of Hg into non-biological archives is also addressed. The review concludes by identifying major knowledge gaps in our understanding, including:(1) the rates of Hg entry into marine and terrestrial ecosystems and the rates of inorganic and MeHg uptake by Arctic microbial and algal communities; (2) the bioavailable fraction of AMDE-related Hg and its rate of accumulation by biota and (3) the fresh water and marine MeHg cycle in the Arctic, especially the marine MeHg cycle.

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Section: Controls On Arctic Food Chain Mercury Accumulation By Methylmentioning

confidence: 99%

The fate of mercury in Arctic terrestrial and aquatic ecosystems, a review

Douglas

Loseto²,

Macdonald³

et al. 2012

Environ. Chem.

119

147

View full text Add to dashboard Cite

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“…This implied that decomposition reactions of MeHg dominated when concentrations were elevated above 100-200 pg/L. The lack of MeHg formation in the samples spiked with Hg(II) show the absence of a mechanism that could compete with MeHg decomposition to produce steady state MeHg concentrations, or photo-associated increases in MeHg as has been proposed in other studies (Hammerschmidt et al, 2007;Kieber et al, 2008). The experiments were conducted in closed batch reactions meaning that they did not allow for replenishing of the removed MeHg by gas-particle partitioning of atmospheric gaseous MeHg to the cloud or fog droplet.…”

Section: Rain and Simulated Cloud Water Experimentsmentioning

confidence: 81%

“…MeHg concentrations in rain water may be determined by a variety of competing processes: 1) abiotic formation in fog and cloud droplets; 2) heterogeneous formation of methylmercury on particles suspended in atmospheric waters; 3) dissolution of methylmercury from particles suspended in atmospheric waters; 4) photo-degradation in fog and cloud droplets; 5) gas-droplet partitioning ; and, 6) scavenging of gases and particulate matter by precipitation during rain events (Gardfeldt et al, 2003;Hammerschmidt et al, 2007;Kieber et al, 2008) The objective of this study was to determine if there was either formation or photodecomposition of MeHg in matrices of natural rain water or simulated cloud water under summer temperature and sunlight conditions. Sunlight exposure experiments, similar to those done previously (Sellers et al, 1996;Krabbenhoft et al, 1998;Sellers et al, 2001;Lean and Siciliano, 2003), were conducted using rain water and simulated cloud water.…”

Section: Introductionmentioning

confidence: 99%

Photodecomposition of Methylmercury in Atmospheric Waters

Bittrich

Rutter

Hall

et al. 2011

Aerosol Air Qual. Res.

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Experiments were conducted to empirically examine net changes in methylmercury concentration of atmospheric waters as function of irradiance. Methods were developed to allow experiments to be conducted at atmospherically relevant concentrations using trace metal clean techniques, over a range of aqueous matrices. Rain water was collected at Devil's Lake State Park, WI, and simulated cloud water was created by water extraction of particulate matter collected at the same site. These waters were spiked with methyl mercury chloride and mercuric chloride and exposed to sunlight on the roof of a building. Experiments were conducted during typical summer conditions with respect to temperature, sunlight intensity and sunlight duration. For all cases, exposure to sunlight resulted in net loss of methylmercury: -0.022 ± 0.002 1/hr in rainwater at a total UVB flux of 8 kWhrs/m 2 ; -0.008 ± 0.001 1/hr in simulated cloud water at a total UVB flux of 5.5 kWhrs/m 2 . For dark cases, no statistically significant formation in methylmercury from inorganic mercury was detected. Furthermore, laboratory experiments to form methylmercury from mercuric-acetate complexes did not give detectable yields. Given the results of this study, and the results of studies cited in this article, it is unlikely that homogeneous MeHg formation is fast enough to lead to the net formation of MeHg in atmospheric waters exposed to sunlight.

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“…Microorganisms, such as sulfate-reducing bacteria and ion-reducing bacteria (Bridou et al, 2011;Fleming et al, 2006), are the major microbial contributors to MeHg production in the environment. However, the abiotic methylation of Hg, which has been validated as an important pathway for MeHg production (Hammerschmidt et al, 2007), has not been studied thoroughly. Abiotic methylation of inorganic Hg by dissolved organic matter (DOM) under solar radiation is considered an important source of MeHg in lakes (Siciliano et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Identification of mercury methylation product by tert-butyl compounds in aqueous solution under light irradiation

Chen

et al. 2015

Marine Pollution Bulletin

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a b s t r a c tThe methylation of mercury (Hg) is of great concern as methylmercury (MeHg), the most toxic species, is produced. This study examined the possibilities of tert-butyl compounds (tert-butyl alcohol (TBA) and tert-butyl hydroperoxide (TBH)) and other alcohols serving as methyl donors for Hg photo-methylation under light irradiation. The yield of MeHg varied among the methyl donors, and it was also significantly influenced by salinity and pH. MeHg could be generated in the presence of TBH under visible light irradiation. The hydroxyl radical ( Å OH) was found to promote MeHg production at low levels, but degrade MeHg in excess. The photo-production of MeHg was tentatively proposed via the complexation of Hg and methyl donors, the formation of an intermediate (, and the intramolecular methyl transfer from methyl donors to Hg. This study implicates photoreactions between Hg and organic pollutants in understanding the fate and transformation of Hg in the aquatic environment.

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Aqueous phase methylation as a potential source of methylmercury in wet deposition

Abstract: The source of monomethylmercury (MMHg) in wet deposition is unknown. Volatilization of gaseous

Cited by 83 publications

References 41 publications

The fate of mercury in Arctic terrestrial and aquatic ecosystems, a review

The fate of mercury in Arctic terrestrial and aquatic ecosystems, a review

Photodecomposition of Methylmercury in Atmospheric Waters

Identification of mercury methylation product by tert-butyl compounds in aqueous solution under light irradiation

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