Thermodynamics of Hg(II) Bonding to Thiol Groups in Suwannee River Natural Organic Matter Resolved by Competitive Ligand Exchange, Hg L<sub>III</sub>-Edge EXAFS and <sup>1</sup>H NMR Spectroscopy

Song, Yu; Jiang, Tao; Liem-Nguyen, Van; Sparrman, Tobias; Björn, Erik; Skyllberg, Ulf

doi:10.1021/acs.est.8b00919

Cited by 53 publications

(93 citation statements)

References 54 publications

(136 reference statements)

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“…It has long been suggested that OM mediates the transport of Hg from terrestrial to the adjacent aquatic environment. Negatively charged surfaces of OM are enriched with carboxyl functional groups (RCOO − ), and thiolates (RS − ) in OM behave as ligands to form a transition metal thiolate complex, which leads to a strong binding affinity with trace metals including Hg [34][35][36] . These associations among OM, thiolates, and THg contents can explain the positive relationships among them as observed in the Svalbard fjords ( Fig.…”

Section: Discussionmentioning

confidence: 99%

Input of terrestrial organic matter linked to deglaciation increased mercury transport to the Svalbard fjords

Kim

Kwon

Lee

et al. 2020

Sci Rep

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Deglaciation has accelerated the transport of minerals as well as modern and ancient organic matter from land to fjord sediments in Spitsbergen, Svalbard, in the European Arctic Ocean. Consequently, such sediments may contain significant levels of total mercury (THg) bound to terrestrial organic matter. The present study compared THg contents in surface sediments from three fjord settings in Spitsbergen: Hornsund in the southern Spitsbergen, which has high annual volume of loss glacier and receives sediment from multiple tidewater glaciers, Dicksonfjorden in the central Spitsbergen, which receives sediment from glacifluvial rivers, and Wijdefjorden in the northern Spitsbergen, which receive sediments from a mixture of tidewater glaciers and glacifluvial rivers. Our results showed that the THg (52 ± 15 ng g −1) bound to organic matter (OM) was the highest in the Hornsund surface sediments, where the glacier loss (0.44 km 3 yr −1) and organic carbon accumulation rates (9.3 ~ 49.4 g m −2 yr −1) were elevated compared to other fjords. Furthermore, the δ 13 C (-27 ~-24‰) and δ 34 S values (-10 ~ 15‰) of OM indicated that most of OM were originated from terrestrial sources. Thus, the temperature-driven glacial melting could release more oM originating from the meltwater or terrestrial materials, which are available for THg binding in the European Arctic fjord ecosystems. Increasing temporal trends of total mercury (THg) concentration in the sediments of the Arctic continental shelves and lakes have recently been reported 1,2. These increasing levels have been proposed to be caused by the long-distance transport of anthropogenic mercury (Hg) from industrialized countries to the Arctic, given its long atmospheric lifetime of 0.3 to 2 years 3,4. In addition, it has been shown that ' Atmospheric Mercury Depletion Events' (AMDE) in the spring can lead to high Hg deposition in the Arctic Ocean. Reactive Hg (Hg 2+) is rapidly formed through in situ oxidation of gaseous Hg° by halogens (i.e., atomic Br and radical BrO), which are generated by solar irradiation through O 3 destruction 5-7. However, previous measurements of atmospheric Hg deposition in the Arctic regions have revealed relatively low deposition rates of <5 µg m −2 yr −1 8. Recent studies have suggested that natural processes governing Hg release via riverine transport 9 , soil runoff, and/or discharge of water coming from thawing permafrost 10 could be important sources of Hg to the Arctic environments. Fjords on Svalbard, the main island of the Svalbard archipelago, is among the most studied fjord systems in the world 11. Previous studies have focused on the effects of local and/or long-range transport, oceanic currents, and long-term sediment deposition rates (i.e., geological and chemical processes that control Hg distribution in surface and core sediments) 4,12-17 on spatial distribution and the extent of accumulation of Hg in the fjord sediment. Recent studies have shown that fjords are effective sequesters of organic carbon among other marine

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Section: Discussionmentioning

confidence: 99%

Input of terrestrial organic matter linked to deglaciation increased mercury transport to the Svalbard fjords

Kim

Kwon

Lee

et al. 2020

Sci Rep

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“… 19 The method has been previously used to determine the concentration of RSH groups associated with natural organic matter (NOM) functional groups, using either MeHg or Hg as the probe. 26 − 28 …”

Section: Introductionmentioning

confidence: 99%

Toward an Internally Consistent Model for Hg(II) Chemical Speciation Calculations in Bacterium–Natural Organic Matter–Low Molecular Mass Thiol Systems

Song

Adediran

Jiang

et al. 2020

Environ. Sci. Technol.

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To advance the scientific understanding of bacteria-driven mercury (Hg) transformation processes in natural environments, thermodynamics and kinetics of divalent mercury Hg(II) chemical speciation need to be understood. Based on Hg L III -edge extended X-ray absorption fine structure (EXAFS) spectroscopic information, combined with competitive ligand exchange (CLE) experiments, we determined Hg(II) structures and thermodynamic constants for Hg(II) complexes formed with thiol functional groups in bacterial cell membranes of two extensively studied Hg(II) methylating bacteria: Geobacter sulfurreducens PCA and Desulfovibrio desulfuricans ND132. The Hg EXAFS data suggest that 5% of the total number of membranethiol functionalities (Mem-RS tot = 380 ± 50 μmol g –1 C) are situated closely enough to be involved in a 2-coordinated Hg(Mem-RS) 2 structure in Geobacter . The remaining 95% of Mem-RSH is involved in mixed-ligation Hg(II)-complexes, combining either with low molecular mass (LMM) thiols like Cys, Hg(Cys)(Mem-RS), or with neighboring O/N membrane functionalities, Hg(Mem-RSRO). We report log K values for the formation of the structures Hg(Mem-RS) 2 , Hg(Cys)(Mem-RS), and Hg(Mem-RSRO) to be 39.1 ± 0.2, 38.1 ± 0.1, and 25.6 ± 0.1, respectively, for Geobacter and 39.2 ± 0.2, 38.2 ± 0.1, and 25.7 ± 0.1, respectively, for ND132. Combined with results obtained from previous studies using the same methodology to determine chemical speciation of Hg(II) in the presence of natural organic matter (NOM; Suwannee River DOM) and 15 LMM thiols, an internally consistent thermodynamic data set is created, which we recommend to be used in studies of Hg transformation processes in bacterium–NOM–LMM thiol systems.

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“…Hg, a soft Lewis acid, has a strong affinity for thiol functional groups in DOM. Song et al [27] reported that Hg interacting with natural organic matter had high thermodynamic stability. Past research has suggested that the complexation of Hg by DOM thiol groups could hinder nanoparticle β-HgS growth [38,39].…”

Section: Resultsmentioning

confidence: 99%

“…Xia et al [48] reported that reduced S in SRHA analyzed by XANES was in the form of thiol/sulfide and thiophene. The thiol functional group on DOM was the major binding site with Hg [27,28]. Among the ligands, sulfur-containing ligands bind Hg much more strongly than oxygen-containing ligands, which appear in AC [28].…”

Section: "Hg + Dom" Conditionmentioning

confidence: 99%

“…Importantly, Hg interacted with DOM increased the methylating rate in comparison to Hg 2+ ; moreover, the β-HgS nanoparticles formed by Hg mixed with sulfide and DOM have a higher availability than β-HgS microparticles for bacterial methylation [26]. Recent studies have also shown that thiol functional groups are the major binding sites which mainly increases solubility, mobility and toxicity of Hg [27,28].…”

Section: Introductionmentioning

confidence: 99%

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Influence of sulfide, chloride and dissolved organic matter on mercury adsorption by activated carbon in aqueous system

Chen

Ch’ng

et al. 2020

Sustain Environ Res

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Using activated carbon (AC) as thin layer capping to reduce mercury (Hg) released from contaminated sediment is a feasible and durable remediation approach. However, several aqueous factors could greatly affect the Hg fate in the aquatic system. This study thus intends to clarify the influences on Hg adsorption by AC with the presence of sulfide, dissolved organic matter (DOM), and chloride. The lab-scale batch experiments were divided into two parts, including understanding (1) AC adsorption performance and (2) Hg distribution in different phases by operational definition method. Results showed that the Hg adsorption rate by AC was various with the presence of sulfide, chloride, and DOM (from fast to slow). Hg adsorption might be directly bonded to AC with Hg-Cl and Hg-DOM complexes and the rate was mainly controlled by intraparticle diffusion. In contrast, “Hg + sulfide” result was better described by pseudo-second order kinetics. The Hg removal efficiency was 92–95% with the presence of 0–400 mM chloride and approximately 65–75% in the “Hg + sulfide” condition. Among the removed Hg, 24–29% was formed into aqueous-phase particles and about 30% Hg was adsorbed on AC with 2–20 μM sulfide. Increasing DOM concentration resulted in more dissolved Hg. The proportion of dissolved Hg increased 31% by increasing DOM concentration from 0.25 to 20 mg C L− 1. Simultaneously, the proportion of adsorbed Hg by AC decreased by 47%. Overall, the presence of chloride increases the Hg adsorption by AC. In contrast, the presence of sulfide and DOM causes a negative effect on AC adsorption.

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Thermodynamics of Hg(II) Bonding to Thiol Groups in Suwannee River Natural Organic Matter Resolved by Competitive Ligand Exchange, Hg L_III-Edge EXAFS and ¹H NMR Spectroscopy

Cited by 53 publications

References 54 publications

Input of terrestrial organic matter linked to deglaciation increased mercury transport to the Svalbard fjords

Input of terrestrial organic matter linked to deglaciation increased mercury transport to the Svalbard fjords

Toward an Internally Consistent Model for Hg(II) Chemical Speciation Calculations in Bacterium–Natural Organic Matter–Low Molecular Mass Thiol Systems

Influence of sulfide, chloride and dissolved organic matter on mercury adsorption by activated carbon in aqueous system

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Thermodynamics of Hg(II) Bonding to Thiol Groups in Suwannee River Natural Organic Matter Resolved by Competitive Ligand Exchange, Hg LIII-Edge EXAFS and 1H NMR Spectroscopy

Cited by 53 publications

References 54 publications

Input of terrestrial organic matter linked to deglaciation increased mercury transport to the Svalbard fjords

Input of terrestrial organic matter linked to deglaciation increased mercury transport to the Svalbard fjords

Toward an Internally Consistent Model for Hg(II) Chemical Speciation Calculations in Bacterium–Natural Organic Matter–Low Molecular Mass Thiol Systems

Influence of sulfide, chloride and dissolved organic matter on mercury adsorption by activated carbon in aqueous system

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Product

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Thermodynamics of Hg(II) Bonding to Thiol Groups in Suwannee River Natural Organic Matter Resolved by Competitive Ligand Exchange, Hg L_III-Edge EXAFS and ¹H NMR Spectroscopy