Photoreactions of Mercury in Aquatic Systems

Vost, Emma; Amyot, Marc; O’Driscoll, Nelson J.

doi:10.1002/9781118146644.ch6

Cited by 16 publications

(22 citation statements)

References 91 publications

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“…The reaction for LIW can perfectly fit the model of a first order reaction and the rate constants were 1.3 × 10 −6 s −1 for LIW 1μm and 2.2 × 10 −6 s −1 for LIW unfiltered . These gross values are comparable to dark (or low light) gross values from incubations for the Baltic Sea (1.5 AE 0.5 × 10 −6 s −1 ) (Kuss et al 2015) and Chesapeake Bay and coastal shelf waters (0.67-1.8 × 10 −6 s −1 ) (Whalin et al 2007), but rate constants of microbial production can be one to two orders of magnitude lower than those attributable to photochemical transformation at the ocean surface (O'Driscoll et al 2006;Whalin et al 2007;Qureshi et al 2009;Vost et al 2012).…”

Section: Lee and Fishersupporting

confidence: 60%

“…Hg 0 formation in the surface mixed layer can involve a variety of complex abiotic and biotic processes. Abiotic processes such as photochemical reduction of Hg(II) has been shown to produce Hg 0 , where solar radiation (visible and ultraviolet), dissolved organic matter, and inorganic free radicals are considered key factors involved in the photochemical formation of Hg 0 from Hg(II) (Nriagu ; Amyot et al ; Costa and Liss , ; Vost et al ). In addition, photodegradation of MeHg can also produce Hg 0 (Suda et al ; Sellers et al ).…”

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Microbial generation of elemental mercury from dissolved methylmercury in seawater

Lee

Fisher

2018

Limnology & Oceanography

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Elemental mercury (Hg0) formation from other mercury species in seawater results from photoreduction and microbial activity, leading to possible evasion from seawater to overlying air. Microbial conversion of monomethylmercury (MeHg) to Hg0 in seawater remains unquantified. A rapid radioassay method was developed using gamma‐emitting 203Hg as a tracer to evaluate Hg0 production from Hg(II) and MeHg in the low pM range. Bacterioplankton assemblages in Atlantic surface seawater and Long Island Sound water were found to rapidly produce Hg0, with production rate constants being directly related to bacterial biomass and independent of dissolved Hg(II) and MeHg concentrations. About 32% of Hg(II) and 19% of MeHg were converted to Hg0 in 4 d in Atlantic surface seawater containing low‐bacterial biomass, and in Long Island Sound water with higher bacterial biomass, 54% of Hg(II) and 8% of MeHg were transformed to Hg0. Decreasing temperatures from 24°C to 4°C reduced Hg0 production rates cell−1 from Hg(II) 3.3 times as much as from a MeHg source. Because Hg0 production rates were linearly related to microbial biomass and temperature, and microbial mercuric reductase was detected in our field samples, we inferred that microbial metabolic activities and enzymatic reactions primarily govern Hg0 formation in subsurface waters where light penetration is diminished.

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Section: Lee and Fishersupporting

confidence: 60%

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confidence: 99%

Microbial generation of elemental mercury from dissolved methylmercury in seawater

Lee

Fisher

2018

Limnology & Oceanography

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“…36 Our results show that high DOC in seawaters favored the Hg(II) photoreduction (SI Figure S6) and decreased the Hg(0) photo-oxidation (SI Figure S9). This finding is consistent with the study of Costa and Liss, 8 who observed that seawaters spiked with humic acid had enhanced Hg(II) reduction rates.…”

Section: Discussionmentioning

confidence: 80%

“…4−35 Therefore, a wide range of rate constants of Hg(II) reduction and Hg(0) oxidation have been reported. 36 As a key component of the regional and global Hg research framework, model study is an important tool for understanding the global Hg cycle. 1,3 One of the most important knowledge gaps of current Hg model study is the lack of representative and comprehensive kinetic data of Hg redox reactions in seawaters.…”

Section: Introductionmentioning

confidence: 99%

Mercury Redox Chemistry in Waters of the Eastern Asian Seas: From Polluted Coast to Clean Open Ocean

Zhang

Yin

et al. 2016

Environ. Sci. Technol.

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We performed incubation experiments using seawaters from representative marine environments of the eastern Asian seas to determine the mercury (Hg) available for photoreduction (Hgr(II)), to investigate the Hg redox reaction kinetics, and to explore the effect of environmental factors and water chemistry on the Hg redox chemistry. Results show that Hgr(II) accounted for a considerable fraction of total Hg (THg) (%Hgr(II)/THg: 24.90 ± 10.55%, n = 27) and positively correlated with THg. Filtration decreased the Hgr(II) pool of waters with high suspended particulate matter (SPM). The positive linear relationships were found between pseudo-first order rate constants of gross Hg(II) photoreduction (k r ) and gross Hg(0) photo-oxidation (k o ) with photosynthetically active radiation (PAR). Under the condition of PAR of 1 m mol m −2 s −1 , the k r were significantly (p < 0.05) lower than k o (k r /k o : 0.86 ± 0.22). The Hg(0) dark oxidation were significantly higher than the Hg(II) dark reduction. The Hg(II) dark reduction was positively correlated to THg, and the anaerobic condition favored the Hg(II) dark reduction. Filtration significantly influenced the Hg photoredox chemistry of waters with high SPM. UVB radiation was important for both Hg(II) photoreduction and Hg(0) photo-oxidation, and the role of other wavebands in photoinduced transformations of Hg varied with the water chemistry.

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“…Elemental mercury can then volatilize to the atmosphere, thereby decreasing the levels of mercury in the ocean (Andersson et al, 2011;Ci et al, 2011;Soerensen et al, 2013). This process is facilitated by wind and surface layer disturbances (O 'Driscoll et al, 2003a, b;Orihel et al, 2007;Vost et al, 2012). Reduction of mercury can be both photochemical (Amyot et al, 1994Zhang and Lindberg, 2001) and biotic (Mason et al, 1995;Siciliano et al, 2002).…”

Section: Mercury Reduction and Oxidation Processes In The Oceanmentioning

confidence: 99%

Chemical and physical transformations of mercury in the ocean: a review

Batrakova¹,

Travnikov²,

Rozovskaya³

2014

Ocean Sci.

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Abstract.Mercury is well known as a dangerous neurotoxin enriched in the environment by human activities. It disperses over the globe, cycling between different environmental media. The ocean plays an important role in the global mercury cycle, acting both as a dispersion medium and as an exposure pathway. In this paper, we review the current knowledge on the major physical and chemical transformations of mercury in the ocean. This review describes the mechanisms and provides a compilation of available rate constants for the major processes in seawater, including oxidation and reduction reactions under light and dark conditions, biotic and abiotic methylation/demethylation, and adsorption by particles. These data could be useful for the development of transport models describing processes undergone by mercury in the ocean.

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Photoreactions of Mercury in Aquatic Systems

Cited by 16 publications

References 91 publications

Microbial generation of elemental mercury from dissolved methylmercury in seawater

Microbial generation of elemental mercury from dissolved methylmercury in seawater

Mercury Redox Chemistry in Waters of the Eastern Asian Seas: From Polluted Coast to Clean Open Ocean

Chemical and physical transformations of mercury in the ocean: a review

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