Uncovering geochemical fractionation of the newly deposited Hg in paddy soil using a stable isotope tracer

Liu, Jiang; Zhao, Lei; Kong, Kun; Abdelhafiz, Mahmoud A.; Tian, Senlin; Jiang, Tao; Meng, Bo; Feng, Xinbin

doi:10.1016/j.jhazmat.2022.128752

Cited by 9 publications

(9 citation statements)

References 81 publications

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“…Furthermore, the availability of nanoparticulate metacinnabar depends on its crystal structure . The nanoparticulate metacinnabar that is converted from the newly deposited atmospheric Hg has a mineral facet containing more binding sites for bacteria, and thus it is preferentially methylated. − The variation of the MeHg concentration in soils could have affected MeHg accumulation by rice plants.…”

Section: Resultsmentioning

confidence: 99%

New Insights into MeHg Accumulation in Rice (Oryza sativa L.): Evidence from Cysteine

Man,

Wang,

Wang

et al. 2024

Environ. Sci. Technol.

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The intake of methylmercury (MeHg)-contaminated rice poses immense health risks to rice consumers. However, the mechanisms of MeHg accumulation in rice plants are not entirely understood. The knowledge that the MeHg−Cysteine complex was dominant in polished rice proposed a hypothesis of co-transportation of MeHg and cysteine inside rice plants. This study was therefore designed to explore the MeHg accumulation processes in rice plants by investigating biogeochemical associations between MeHg and amino acids. Rice plants and underlying soils were collected from different Hgcontaminated sites in the Wanshan Hg mining area. The concentrations of both MeHg and cysteine in polished rice were higher than those in other rice tissues. A significant positive correlation between MeHg and cysteine in rice plants was found, especially in polished rice, indicating a close geochemical association between cysteine and MeHg. The translocation factor (TF) of cysteine showed behavior similar to that of the TF of MeHg, demonstrating that these two chemical species might share a similar transportation mechanism in rice plants. The accumulation of MeHg in rice plants may vary due to differences in the molar ratios of MeHg to cysteine and the presence of specific amino acid transporters. Our results suggest that cysteine plays a vital role in MeHg accumulation and transportation inside rice plants.

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Section: Resultsmentioning

confidence: 99%

New Insights into MeHg Accumulation in Rice (Oryza sativa L.): Evidence from Cysteine

Man,

Wang,

Wang

et al. 2024

Environ. Sci. Technol.

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“…In fact, the effectiveness of in situ amendments to Hg is based on stoichiometric considerations (the amendments active binding sites should exceed that of Hg in sediments) and the distribution coefficients (Kd) of the amendment for Hg since the amendment functions by competing Hg against the natural sorbents [ 49 ]. In this study, the main reason for this phenomenon could be that Hg readily formed complexes with soil organic matter [ 31 , 50 ], reducing free Hg adsorption on biochar. Overall, our results indicate that biochar has limited adsorption to Hg in soil.…”

Section: Resultsmentioning

confidence: 99%

“…Overall, humus-like components with higher aromaticity and molecular weight are difficult to be biodegraded and thus present relatively high complexation ability to reduce the Hg phytoavailability [ 26 ]. Protein-like substances with relatively simple and unstable molecular structures may release “new” Hg from the soil through mineralization of organic matter and microbial metabolism [ 31 , 87 ].…”

Section: Resultsmentioning

confidence: 99%

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Unveiling the Role of Dissolved Organic Matter on the Hg Phytoavailability in Biochar-Amended Soils

Chen

Yang

et al. 2023

IJERPH

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Biochar can effectively reduce the phytoavailability of mercury (Hg) in soil, but the mechanisms are not fully understood. In this study, the dynamic changes in Hg content adsorbed by the biochar (BC-Hg), Hg phytoavailability in the soil (P-Hg), and soil dissolved organic matter (DOM) characteristics were determined over a 60-day treatment period. Biochar obtained at 300 °C, 500 °C and 700 °C reduced the P-Hg concentration assessed by MgCl2 extraction by 9.4%, 23.5% and 32.7%, respectively. However, biochar showed a very limited adsorption on Hg, with the maximum BC-Hg content only accounting for 1.1% of the total amount. High-resolution scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) results showed that the proportion of Hg atoms in biochar after 60 d was barely detectable. Biochar treatment can shift soil DOM toward higher aromatic content and molecular weight. Additionally, the addition of high-temperature biochar increased more humus-like components, but low-temperature biochar increased more protein-like components. Correlation analysis and partial least squares path modeling (PLS-PM) showed that biochar promoted humus-like fractions formation to reduce the Hg phytoavailability. This research has deepened the understanding of the mechanisms by which biochar stabilizes Hg in agricultural soils.

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“…Furthermore, most existing studies have only investigated bulk concentration changes in Hg species in rice paddies, with little study of interconversion processes. ,,, Again, this has limited our understanding of net MeHg production mechanisms. Several studies have spiked stable Hg isotope tracers into rice paddy systems to simultaneously trace different transformation processes, including methylation and demethylation, ,,, partitioning and redistribution, and rice plant uptake and translocation. ,, However, only Hg II or MeHg tracers have been applied to date, and only isotopic signals of THg or MeHg were measured in these studies. As a result, the redox processes of Hg in rice paddy systems have not yet been precisely traced.…”

Section: Introductionmentioning

confidence: 99%

Mercury and Sulfur Redox Cycling Affect Methylmercury Levels in Rice Paddy Soils across a Contamination Gradient

Liu

Chen

Poulain

et al. 2023

Environ. Sci. Technol.

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Methylmercury (MeHg) contamination in rice via paddy soils is an emerging global environmental issue. An understanding of mercury (Hg) transformation processes in paddy soils is urgently needed in order to control Hg contamination of human food and related health impacts. Sulfur (S)-regulated Hg transformation is one important process that controls Hg cycling in agricultural fields. In this study, Hg transformation processes, such as methylation, demethylation, oxidation, and reduction, and their responses to S input (sulfate and thiosulfate) in paddy soils with a Hg contamination gradient were elucidated simultaneously using a multi-compound-specific isotope labeling technique (200HgII, Me198Hg, and 202Hg0). In addition to HgII methylation and MeHg demethylation, this study revealed that microbially mediated reduction of HgII, methylation of Hg0, and oxidative demethylation–reduction of MeHg occurred under dark conditions; these processes served to transform Hg between different species (Hg0, HgII, and MeHg) in flooded paddy soils. Rapid redox recycling of Hg species contributed to Hg speciation resetting, which promoted the transformation between Hg0 and MeHg by generating bioavailable HgII for fuel methylation. Sulfur input also likely affected the microbial community structure and functional profile of HgII methylators and, therefore, influenced HgII methylation. The findings of this study contribute to our understanding of Hg transformation processes in paddy soils and provide much-needed knowledge for assessing Hg risks in hydrological fluctuation-regulated ecosystems.

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Uncovering geochemical fractionation of the newly deposited Hg in paddy soil using a stable isotope tracer

Cited by 9 publications

References 81 publications

New Insights into MeHg Accumulation in Rice (Oryza sativa L.): Evidence from Cysteine

New Insights into MeHg Accumulation in Rice (Oryza sativa L.): Evidence from Cysteine

Unveiling the Role of Dissolved Organic Matter on the Hg Phytoavailability in Biochar-Amended Soils

Mercury and Sulfur Redox Cycling Affect Methylmercury Levels in Rice Paddy Soils across a Contamination Gradient

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