Mercuric Hg2+ ion forms strong complexes with dissolved organic matter (DOM) in natural waters. The complexation of Hg2+ by sulfhydryl groups of DOM was regarded as the main mechanism for Hg2+-DOM ...interactions, particularly in anoxic sulfur and DOM-rich environments. In the present study, the influences of pH and sulfide addition on the molecular structure of Hg2+-DOM complexes and the characteristics of Hg2+ binding to DOM were investigated using FT-IR and synchronous fluorescence two-dimensional correlation spectroscopic analysis. Results showed that, during the Hg2+ binding process, the aromatic hydrogen CH in humic acids (HA) gave the fastest responses to pH perturbation and the S-reacted HA (S-HA) exhibited different reaction patterns from the unreacted HA. In S-HA, the esters/alcohols CO and carboxyl CO gave the fastest responses to Hg2+ binding. In the process of S-HA binding to Hg2+, the protein-like fractions including proteins, amino acids or monoaromatics played the leading role. Sulfide addition of HA enhanced the reactivity of small molecular weight compounds with low aromaticity and improved the binding ability of protein-like fractions to Hg2+. These findings provide a better understanding of the interaction mechanisms between Hg2+ and DOM at a molecular level and have important environmental implications in Hg2+ biogeochemical transformation, transport and cycling.
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•Aromatic hydrogen CH in HA gave the fastest responses to pH during Hg2+ binding.•Esters/alcohols CO and carboxyl CO in S-HA gave the fastest responses to Hg2+.•Protein-like fractions played the leading role in the process of S-HA binding to Hg2+.•Sulfide addition of HA enhanced the reactivity of small molecular weight compounds.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•FeRB dominated in Hg methylator community, followed by methanogens.•SRB had high abundance but less containing hgcA.•Eh had significantly positive correlation with MeHg ...concentration.•C/N and Eh value was the key role predicting Hg methylator community structure.
Subalpine peatlands are a critical sink of mercury (Hg) and source of methylmercury (MeHg). However, little is known about the identity of Hg methylators or the geochemical factors controlling their distribution. Here, high-throughput sequencing of 16S rRNA and hgcA genes were used to investigate the community composition of Hg methylating microbes and their relating geochemical factors in Dajiuhu, which is a subalpine Sphagnum peatland. The results showed that MeHg content in the soils varied from 0.9 to 13.3 ng·g−1, while the ratio of MeHg to total Hg varied between 0.98% and 8.13%. The majority of the hgcA sequences clustered with Geobacteraceae, followed by Methanoregulaceae. The ratio of hgcA abundance and quantitative PCR (qPCR) gene copy numbers (hgcA/qPCR) showed that iron-reducing bacteria (FeRB) have the highest Hg methylator proportion within it, followed by methanogens. Although a high abundance of sulfate-reducing bacteria (SRB) was observed based on 16S rRNA, the abundance that contained hgcA sequences was low. Notably, as the MeHg concentration increased, the community structure of Hg methylating microbes shifted from FeRB dominance to FeRB and methanogen dominance, which was predicted by the redox potential (Eh) and C/N value.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Microplastics are widespread in estuarine, coastal, and deep sea sediments. The influence of microplastics on mercury (Hg) methylation in paddy soils with different characteristics, however, has not ...been well reported. In this research, we conducted a microcosmic experiment using red soil and alkaline soil with 2%, 7% and 10% polyvinyl chloride microplastics (PVC-MPs). Diffusive gradients in thin film (DGT) were used to test bioavailable Hg2+ and bioavailable methylmercury (MeHg) in soils. Results showed that PVC-MPs could decrease bioavailable MeHg concentrations both in red soil and alkaline soil. We demonstrated that these decreases could be due to three possible mechanisms: (1) PVC-MPs affected DOM composition, which resulted in a difference in combining capacity for bioavailable Hg2+; (2) PVC-MPs decreased MeHg via changing soil properties (including sulfate and dissolved Fe); (3) PVC-MPs affected the abundance of Proteobacteria, Firmicutes, and hgcA gene in soils. Our results emphasized the significance of investigating effects of microplastics on specific contaminants to implement effective environmental remediation strategies in polluted paddy soils.
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●The first time to demonstrated the influences of microplastics on Hg methylation in paddy soils.●DOM and bioavailable Hg2+ in two soils showing opposite trend when microplastics addition.●DGTs were used to accurate quantification the bioavailable Hg2+ and MeHg.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Hg isotopic composition of 1-year-old Norway spruce (Picea abies) shoots collected from Saarland cornurbation Warndt, Germany, since 1985 by the German Environmental Specimen Bank, were measured ...for a better understanding of the temporal trends of Hg sources. The isotopic data showed that Hg was mainly taken up as gaseous element mercury (GEM) and underwent oxidation in the spruce needles; this led to a significant decrease in the δ202Hg compared with the atmospheric Hg isotopic composition observed for deciduous leaves and epiphytic lichens. Observation of the odd mass-independent isotopic fractionation (MIF) indicated that Δ199Hg and Δ201Hg were close to but slightly lower than the actual values recorded from the atmospheric measurement of the GEM isotopic composition in non-contaminated sites in U.S. and Europe, whereas observation of the even-MIF indicated almost no differences for Δ200Hg. This confirmed that GEM is a major source of Hg accumulation in spruce shoots. Interestingly, the Hg isotopic composition in the spruce shoots did not change very significantly during the study period of >30 years, even as the Hg concentration decreased significantly. Even-MIF (Δ200Hg) and mass-dependent fractionation (MDF) (δ202Hg) of the Hg isotopes exhibited slight decrease with time, whereas odd-MIF did not show any clear trend. These results suggest a close link between the long-term evolution of GEM isotopic composition in the air and the isotopic composition of bioaccumulated Hg altered by mass-dependent fraction in the spruce shoots.
•The shoots serve as passive samplers for airborne pollutants.•Hg isotopic compositions of one-year-old spruce shoots were measured using CV-MC-ICP-MS.•Δ199Hg and Δ201Hg did not significantly change during the study period.•Δ200Hg and δ202Hg exhibited slight decreasing trends over time.•Such decreases may be attributed to changes in the global and local Hg emissions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
(PhSe)
2Hg reacts initially with HgX
2 (X = Cl, I) and further with triphenylphosphine/DMF to give (PhSe)
7Hg
4ClPy
n
(
1) and (PhSe)
7Hg
4I(DMF)
n
(
2), polymeric assemblies of (μ-Se)Hg clusters ...obtained through coordinating intermediary ligands. Each single adamantoid molecule of
1 and
2 presents the Hg
II ions with a distorted tetrahedral configuration linked through asymmetric μ-(Ph)Se
− bridges. (PhSe)
7Hg
4ClPy
n
and (PhSe)
7Hg
4I(DMF)
n
are further examples of extended one-dimensional chains of closed anisotropic ME (E
=
S, Se, Te) systems. In these reactions the features of the intermediary ligands should determine the template which leads to single adamantane moieties or to fused ones.
(PhSe)
2Hg reacts initially with HgX
2 (X
=
Cl, I) and further with triphenylphosphine/DMF to give (PhSe)
7Hg
4ClPy
n
(
1) and (PhSe)
7Hg
4I(DMF)
n
(
2), polymeric assemblies of (μ-Se)Hg clusters obtained through coordinating intermediary ligands. Each single adamantoid molecule of
1 and
2 presents the Hg
II ions with a distorted tetrahedral configuration linked through asymmetric μ-(Ph)Se
− bridges. (PhSe)
7Hg
4ClPy
n
and (PhSe)
7Hg
4I(DMF)
n
are further examples of extended one-dimensional chains of closed anisotropic ME (E
=
S, Se, Te) systems. In these reactions the features of the intermediary ligands should determine the template which leads to single adamantane moieties or to fused ones.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Mercury (Hg) is a globally distributed toxic metal and could pose serious harm to birds, which may ultimately threaten human health through poultry consumption. However, the avian Hg metabolism ...remains unclear. Poultry, like chickens, are more accessible human dietary sources than wild birds and are ideal proxies to study Hg metabolism in birds. In this study, the avian Hg metabolism is carefully investigated with hens fed by Hg-spiked (both inorganic mercury IHg and methylmercury MeHg) foods. Our results demonstrate that feces and eggs are the main removal pathways of Hg from hens, rather than feathers. Eggs show particularly rapid responses towards Hg exposures, thus could be more sensitive to environmental Hg pollution than feathers, feces or internal organs (and tissues). Egg yolk (with THg peak of 55.92 ng/g on Day 6) and egg white (THg peak of 1195.03 ng/g on Day 4) react as an effective bioindicator for IHg and MeHg exposure, respectively. In 90-day-single-dose exposure, IHg is almost completely excreted, while approximately 11% of MeHg remains in internal organs. Our study provides new insight into the metabolism and lifetime of IHg and MeHg in birds, advancing the understanding of the dynamics for human exposure to Hg through poultry products.
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●Hg metabolism is carefully investigated with hens fed by Hg-spiked food.●Feces and eggs are the main removal pathways of Hg from hens, rather than feathers.●Eggs are more sensitive to Hg pollution than feathers, feces or internal organs.●IHg and MeHg are more easily accumulated in egg yolk and egg white, respectively.●MeHg is more preferentially retained in hen’s bodies than IHg.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Graphitic carbon nitride quantum dots (g-CNQDs) were prepared by a simple method.•K3Fe(CN)6 was used as an oxidant in chemiluminescence (CL) system of g-CNQDs.•Hg(II) ion has a diminishing effect on ...the g-CNQDs–K3Fe(CN)6 CL system.•A simple and sensitive chemosensor was constructed for Hg(II) ion detection.•The method was successfully applied to determine Hg(II) ion in various real samples.
In this research, graphitic carbon nitride quantum dots (g-CNQDs) were prepared by a simple and one-step microwave-assisted approach and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The chemiluminescence (CL) emission of the synthesized g-CNQDs induced by K3Fe(CN)6 as an oxidant along with the CL mechanism were investigated. Based on the diminishing effect of Hg(II) ion on the g-CNQDs–K3Fe(CN)6 CL system, a simple and sensitive chemosensor was constructed for Hg(II) ion detection in aqueous solutions. A response surface methodology was used to optimize the experimental parameters affecting the analytical signal. Under the optimized experimental conditions, the calibration graph was linear in the range of 0.25–10ngmL−1 with a detection limit of 0.08ngmL–1. The inter-day and intra-day relative standard deviations for six replicate determinations of 4ngmL–1 Hg(II) ion were 3.4% and 2.8%, respectively. The developed method was successfully applied for the selective and sensitive determination of Hg(II) in water and food samples with recoveries in the range of 95.7–102.8% for the spiked samples. The accuracy of the method was evaluated by analyzing a certified reference material (SRM 1566b).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Bioplastics have emerged to minimize the ecological footprint of non-degradable plastics. However, the effect of their degradation in aquatic systems, including the interaction with toxic metals, is ...still unexplored. In this work, the influence of UV-aging on structure, chemistry, wettability, rigidity, and Hg-sorption of commercially available bioplastic (BIO)- and polyethylene (PE)-based films was studied. To mimetize the materials disposal in fresh-/saltwaters, non-saline/saline aqueous solutions were used in Hg-sorption studies. ATR-FTIR spectra revealed that the BIO film was a coblended starch/polyester-based material, whose microstructure, physicochemical, and mechanical properties changed after UV-aging to a higher extent than in PE film. AFM and kinetic modelling pointed out electrostatic interactions/complexation as the mechanisms involved in the increased Hg-sorption by the UV-aged BIO film. An increased salinity did not impair its Hg-sorption. Therefore, when disposed in aquatic systems, starch/polyester-based bioplastics can play a potential vector for amplifying Hg along the food chain.
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•BIO film revealed to be a coblended starch/polyester-based material.•BIO film had higher Hg-sorption ability than the PE film.•UV-aging highly increased the BIO film Hg sorption capacity.•Hg was caught by the BIO film through electrostatic/complexation mechanisms.•Starch/polyester-based films may amplify the Hg in aquatic environments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Highly selective poly(vinyl chloride) (PVC) membrane electrodes based on recently synthesized mercury complexes including Hg(Nmpntb)2 and Hg(Npdntb)2 as new carriers for iodide‐selective electrodes ...by incorporating the membrane ingredients on the surface of graphite electrodes are reported. The effect of various parameters including the membrane composition, pH and possible interfering anions were investigated on the response properties of the electrodes. Both sensors exhibited Nernstian responses toward iodide over a wide concentration range of 7×10−7 to 0.1 M and 1×10−6 to 0.1 M, with slopes of 59.6±0.8 and 58.9±0.9 mV per decade of iodide concentration and detection limit of 3×10−7 M and 7×10−7 for Hg(Npdntb)2 and Hg(Nmpntb)2, respectively, over a wide pH range of 3–11. The sensors have response times of ≤5 s and can be used for at least 2 months without any considerable divergence in their potential response. The proposed electrodes show good ability to discriminate iodide over several inorganic and organic anions. The electrodes were successfully applied to direct determination of iodide in synthetic mixture, waste water and drinking water and as indicator electrodes in precipitation titrations.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Mercury-antimony (HgSb) mining activities are important anthropogenic sources of Hg and Sb to the local environment. The Xunyang HgSb mine situated in Shaanxi Province is an active Hg mine in China. ...To understand the emission, transportation, and deposition of Sb through HgSb mining activities, current study systematically monitored the Sb concentration in precipitation in the Xunyang HgSb mining district. Five groups of experimental pots were carefully designed to further investigate the influence of HgSb mining activities on the Sb contamination in the local surface soil. Based on the overtime increasing of the Sb concentrations in soil from experimental pots, for the first trial, we estimated the atmospheric deposition flux/mass of Sb in the Xunyang HgSb mining district. Our results showed that the concentrations of Sb in precipitation in the Xunyang HgSb mining district ranged from 0.71 μg L−1 to 19 μg L−1 (mean = 4.2 ± 4.5 μg L−1), which was orders of magnitude higher than that at the control site. As expected, the concentration of Sb in precipitation was highly elevated near of the HgSb smelter and gradually decreased with distance from the smelter. After 12 months exposure, Sb concentrations in soil of experimental pots were increased by 1.2–8.5 times. The average atmospheric wet and dry deposition flux of Sb in the Xunyang HgSb mining district were 7.2 ± 6.9 μg m−2 day−1 and 2.1 ± 4.7 mg m−2 day−1, respectively; the annual wet and dry deposition mass of Sb through HgSb mining activities were estimated to be 1.6 t y−1 and 158 t y−1, respectively, indicating that dry deposition was the dominant pathway (98 ± 1.2%) for the removal of Sb from the atmosphere. Our results confirmed that the ongoing HgSb mining activities resulted to serious Sb contamination to terrestrial ecosystems, posing a potential threat to local residents in the Xunyang HgSb mining district.
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•Sb concentrations in precipitation and rice paddy soil were highly elevated near of the HgSb smelter.•Dry deposition was the dominant pathway for the removal of Sb from the atmosphere.•The ongoing HgSb mining activities resulted to serious Sb contamination to surface terrestrial ecosystems.
Dry deposition was the dominant pathway for removal of Sb from the atmosphere and the ongoing HgSb mining activities resulted to serious Sb contamination to surface terrestrial ecosystems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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