Modeling of the structure-specific kinetics of abiotic, dark reduction of Hg(II) complexed by O/N and S functional groups in humic acids while accounting for time-dependent structural rearrangement

Jiang, Tao; Skyllberg, Ulf; Wei, Shiquiang; Wang, Dingyong; Lu, Song; Jiang, Zhenmao; Flanagan, D. C.

doi:10.1016/j.gca.2015.01.011

Cited by 67 publications

(68 citation statements)

References 70 publications

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“…There are only a few reports on the Hg contamination in Chinese estuaries, where high levels of Hg commonly are encountered, caused by the rapid industrial developments (Wang et al, 2009, Luo et al, 2012Gao et al, 2014;Ci et al, 2011). It is well known that DOM regulates Hg dynamics in aquatic environments through its chemical bonding to reduced sulfur groups (Ravichandran, 2004;Skyllberg et al, 2006), by its induction of photoreactions (Jeremiason et al, 2015), and by its control of dark redox transformations (Gu et al, 2011, Jiang et al, 2015. Additionally, DOM plays a dual role (i.e., enhancement or inhibition) in the production of MeHg due to its effect on Hg speciation and bioavailability (Graham et al, 2012;Zhang et al, 2014;Hsu-Kim et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Characteristics of dissolved organic matter (DOM) and relationship with dissolved mercury in Xiaoqing River-Laizhou Bay estuary, Bohai Sea, China

Jiang

Skyllberg

Björn

et al. 2017

Environmental Pollution

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104

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a b s t r a c tBecause of heterogeneous properties, dissolved organic matter (DOM) is known to control the environmental fate of a variety of organic pollutants and trace metals in aquatic systems. Here we report absorptive and fluorescence properties of DOM, in concurrence with concentrations of dissolved mercury (Hg), along the Xiaoqing River-Laizhou Bay estuary system located in the Bohai Sea of China. A mixing model consisting of the two end-members terrestrial and aquatic DOM demonstrated that terrestrial signatures decreased significantly from the river into the estuary. Quasi-conservative mixing behavior of DOM sources suggests that the variations in the average DOM composition were governed by physical processes (e.g., dilution) rather than by new production and/or degradation processes. In contrast to some previous studies of river-estuary systems, the Xiaoqing River-Laizhou Bay estuary system displayed a non-significant correlation between DOM and Hg quantities. Based on this and the variation of Hg concentration along the salinity gradient, we concluded that Hg showed a non-conservative mixing behavior of suggested end-member sources. Thus, rather than mixing, Hg concentration variations seemed to be controlled by biogeochemical processes.

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Section: Introductionmentioning

confidence: 99%

Characteristics of dissolved organic matter (DOM) and relationship with dissolved mercury in Xiaoqing River-Laizhou Bay estuary, Bohai Sea, China

Jiang

Skyllberg

Björn

et al. 2017

Environmental Pollution

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104

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“…2a and b). The latter tracer can be assumed to rapidly bind (within seconds) (Hintelmann and Harris, 2004; Jiang, et al, 2015) to easily available adsorption sites (O and N) in the sediment POM matrix, which are much more abundant than any pore water DOM ligands, and with time migrate to less available, but more thermodynamically stable, POM binding sites (reduced sulfur sites) (Jiang, et al, 2015). In contrast to our results, adsorption of Hg II complexed to organic matter (OM) derived from a peat soil has previously been demonstrated to reduce the availability of Hg II for methylation in a brackish water sediment (Jonsson, et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

“…In more traditional methylation assays, where Hg II (aq) is used as the methylation tracer, the Hg II (aq) added is assumed to quickly partition to easily available binding sites in the sediment (Hintelmann, et al, 2000; Hintelmann and Harris, 2004; Jiang, et al, 2015) and with time migrate to less available and more stable binding sites thereby adopting an overall binding strength resembling that of ambient Hg (Hintelmann, et al, 2000; Jonsson, et al, 2012). If our assumption was incorrect, a rapid increase in the concentration of MeHg formed from the Hg II (aq) tracer would be expected within the first minutes of such incubation experiments.…”

Section: Discussionmentioning

confidence: 99%

Enhanced availability of mercury bound to dissolved organic matter for methylation in marine sediments

Mazrui

Jonsson

Thota

et al. 2016

Geochimica et Cosmochimica Acta

112

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The forms of inorganic mercury (HgII) taken up and methylated by bacteria in sediments still remain largely unknown. From pure cultures studies, it has been suggested that dissolved organic matter (DOM) may facilitate the uptake either by acting as a shuttle molecule, transporting the HgII atom to divalent metal transporters, or by binding HgII and then being transported into the cell as a carbon source. Enhanced availability of Hg complexed to DOM has however not yet been demonstrated in natural systems. Here, we show that HgII complexed with DOM of marine origin was up to 2.7 times more available for methylation in sediments than HgII added as a dissolved inorganic complex (HgII(aq)). We argue that the DOM used to complex HgII directly facilitated the bacterial uptake of HgII whereas the inorganic dissolved HgII-complex adsorbed to the sediment matrix before forming bioavailable dissolved HgII complexes. We further demonstrate that differences in net methylation in sediments with high and low organic carbon content may be explained by differences in the availability of carbon to stimulate the activity of Hg methylating bacteria rather than, as previously proposed, be due to differences in HgII binding capacities between sediments.

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“…If the thiol % was not determined for the used Leonardite HA, a range of thiol % was available in the literature for various humic acids [51][52][53][54][55][56][57], mainly determined from XAS records. This range varied from 10% to 50% of S tot as thiol groups.…”

Section: Fitting the Binding Parametersmentioning

confidence: 99%

“…Moreover, the only S tot amount was not sufficient to determine the thiol concentrations in humic substances. The concentrations of thiol groups varied from 1% to 46.9% [51][52][53][54][55][56][57]. To better understand the binding of As(III) to thiol groups, it is therefore absolutely necessary to determine thiol concentrations.…”

Section: Implications Of the Direct Binding Mechanism Evidencedmentioning

confidence: 99%

Thiol groups controls on arsenite binding by organic matter: New experimental and modeling evidence

Catrouillet

Davranche

Dia

et al. 2015

Journal of Colloid and Interface Science

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Although it has been suggested that several mechanisms can describe the direct binding of As(III) to organic matter (OM), more recently, the thiol functional group of humic acid (HA) was shown to be an important potential binding site for As(III). Isotherm experiments on As(III) sorption to HAs, that have either been grafted with thiol or not, were thus conducted to investigate the preferential As(III) binding sites. There was a low level of binding of As(III) to HA, which was strongly dependent on the abundance of the thiols. Experimental datasets were used to develop a new model (the modified PHREEQC-Model VI), which defines HA as a group of discrete carboxylic, phenolic and thiol sites. Protonation/deprotonation constants were determined for each group of sites (pKA=4.28±0.03; ΔpKA=2.13±0.10; pKB=7.11±0.26; ΔpKB=3.52±0.49; pKS=5.82±0.052; ΔpKS=6.12±0.12 for the carboxylic, phenolic and thiols sites, respectively) from HAs that were either grafted with thiol or not. The pKS value corresponds to that of single thiol-containing organic ligands. Two binding models were tested: the Mono model, which considered that As(III) is bound to the HA thiol site as monodentate complexes, and the Tri model, which considered that As(III) is bound as tridentate complexes. A simulation of the available literature datasets was used to validate the Mono model, with logKMS=2.91±0.04, i.e. the monodentate hypothesis. This study highlighted the importance of thiol groups in OM reactivity and, notably, determined the As(III) concentration bound to OM (considering that Fe is lacking or at least negligible) and was used to develop a model that is able to determine the As(III) concentrations bound to OM.

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Modeling of the structure-specific kinetics of abiotic, dark reduction of Hg(II) complexed by O/N and S functional groups in humic acids while accounting for time-dependent structural rearrangement

Cited by 67 publications

References 70 publications

Characteristics of dissolved organic matter (DOM) and relationship with dissolved mercury in Xiaoqing River-Laizhou Bay estuary, Bohai Sea, China

Characteristics of dissolved organic matter (DOM) and relationship with dissolved mercury in Xiaoqing River-Laizhou Bay estuary, Bohai Sea, China

Enhanced availability of mercury bound to dissolved organic matter for methylation in marine sediments

Thiol groups controls on arsenite binding by organic matter: New experimental and modeling evidence

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