Sulfate-reducing bacteria and sulfur-oxidizing bacteria interactions at redox interfaces: Implications for mercury methylation.

Methylmercury (MeHg), the most neurotoxic and bioaccumulative mercury (Hg) species, poses significant risks to human and ecosystem health. Predicting these risks requires elucidating the drivers of MeHg production, which peaks at redox interfaces in aquatic systems where the primary Hg methylators, sulfate-reducing bacteria (SRB), are most active. Elevated Hg(II) methylation at these zones is primarily driven by the active sulfur cycling, primarily mediated by Hg-methylating SRB and sulfur-oxidizing bacteria (SOB) interactions.

Chemically recalcitrant molecules are the primary components regulating the electron-donating capacity (EDC) of dissolved organic matter.

The electron-donating capacity (EDC) of dissolved organic matter (DOM) plays a central role in regulating environmental redox processes, and is closely governed by the DOM characteristics. As DOM increasingly becomes a focal point in carbon sequestration strategies aimed at mitigating climate change, understanding how its molecular characteristics influence redox functionality is critical. However, the role of DOM chemodiversity, including molecular diversity, functional diversity, and compositional traits, in governing its EDC remains underexplored at the molecular scale.

Organic ligands control microbial uptake of Hg(II): effects on Hg(II) speciation and bacterial physiology.

How organic ligands regulate microbial Hg(II) bioavailability remains a critical knowledge gap in elucidating methylmercury production and subsequent bioaccumulation in biota. Six model ligands with different functional groups (ethylenediaminetetraacetate [EDTA], citrate [CTA], cysteine [CYS], glutathione [GSH], 2, 3-dimercapto-1-propanesulfonate [DMPS], and 3-mercapto-1-propanesulfonate [MPS]) were applied to probe their impacts on Hg(II) bioavailability, by direct measurement of active cellular Hg(II) and cell physiology using a Hg(II)-specific (Escherichia coli PRL) and a constitutive biosensor (E. coli PJL), respectively.

Rhizobial symbiosis modulates mercury accumulation and metabolic adaptation under hydrological extremes.

Phytoremediation offers a sustainable strategy for mitigating mercury (Hg) contamination, yet its efficacy under variable water availability remains poorly understood. Robinia pseudoacacia, a leguminous tree with notable phytoremediation potential, was investigated under combined Hg exposure and water stress-drought (HgD) or flooding (HgF)-with or without rhizobia inoculation. In a controlled greenhouse study, HgD exposure enhanced root dry biomass, increased nodule nitrogenase activity, and promoted root Hg accumulation, indicating a detoxification mechanism via root retention.

Effects of redox-modified biochar on mercury reduction and methylation on electron transfer in Geobacter sulfurreducens PCA.

Geobacterplays a key role in mercury (Hg) methylation and reduction in rice fields.Biochar boosts microbial electron transfer, but its impact on Hg reduction and methylation remains unclear. This study investigates how oxidative (OBC) and reductive (RBC) biochar influence Hg reduction and methylation by Geobacter sulfurreducens PCA.

Role of Methanosarcina in mercuric mercury transportation and methylation in sulfate-driven anaerobic oxidation of methane with municipal wastewater sludge.

Sulfate-driven anaerobic oxidation of methane (AOM) and anaerobic digestion (AD) with municipal wastewater sludge containing heavy metals may provide favorable conditions for the biogeochemical transformation of mercury (Hg) by methanogens and methanotrophs. However, it remains largely unclear what Hg-methylators functioned and what role Methanosarcina played in these processes. Here, we performed sulfate-driven AOM following AD with Hg-containing wastewater sludge and investigated the role of microbes, especially Methanosarcina, in the biogeochemical transformation of Hg based on 16S rRNA amplicon and metatranscriptomic sequencing.

Thiolated non-conjugated nano polymer network for advanced mercury removal from water.

Developing advanced adsorbents for selectively deducing mercury (Hg) in water to one billionth level is of great significance for public health and ecological security, but achieving the balance among efficiency, cost and environmental friendliness of adsorbents still faces enormous challenges. Herein, we present a high thiol content non-conjugated nano polymer network (PVB-SH) through simple microemulsion polymerization for efficient Hg ion (Hg(II)) removal. The PVB-SH is prepared by conventional commercial reagents and does not consume toxic organic solutions.

Climate and vegetation controlling accumulation and translocation of heavy metals in water tower regions of Qinghai-Tibet Plateau.

Understanding how climate and vegetation influencing accumulation and translocation of heavy metals (HMs) in soils and vegetation in the Qinghai-Tibet Plateau (QTP) is critical to assess the ecological risk induced by HMs under the global warming. To accompany this goal, we comprehensively determined the accumulation and translocation of HMs within the interface of soil-vegetation in water tower regions of the QTP. The PMF model results show that 54 %-86 % of cobalt (Co), nickel (Ni), arsenic (As), zinc (Zn) and lead (Pb) in the surface soil are mainly from rock weathering and 54 % of cadmium (Cd) comes from effect of litter return.

Mercury methylation and bioaccumulation in purple paddy soil systems with different acid-base properties.

Paddy soil is recognized as a hotspot for mercury (Hg) transformation. Soil acid-base property (expressed as pH) plays a crucial role in Hg methylation and accumulation in paddy systems. However, it is challenging to study this process in soils with varying pH values due to the rarity of a single soil type spanning a wide pH range.

How ambient temperature rise affects mercury dynamics and its pools in secondary forests.

The forest ecosystem is a significant pool for capturing atmospheric mercury (Hg) deposition, with most Hg accumulating in forest soils. As secondary forests now dominate global forest cover, they are particularly sensitive to changes in ambient temperature. However, the impact of these changes on Hg dynamics in secondary forests remains poorly understood.

Mercury reduction by agricultural organic waste-derived dissolved organic matter: Kinetic analysis and the role of light-induced free radicals.

Agricultural organic wastes can leach dissolved organic matter (DOM) into surrounding water bodies, establishing them as significant sources of aquatic DOM. Given the importance of DOM in biogeochemical cycling of mercury (Hg), this DOM may mediate divalent Hg (Hg(II)) reduction, a process that remains poorly understood. This study investigated Hg(II) reduction using DOM derived from six representative agricultural wastes, categorized into livestock manure (chicken, pig, cow) and crop straw (rice, corn, rapeseed), with systematic considerations of the kinetics of reduction processes and the involvement of key free radicals.

Influences of wildfire on the soil dissolved organic matter characteristics and its electron-donating capacity.

Global increases in the intensity and frequency of wildfires are driving major changes in soil organic matter (SOM) characteristics, including soil dissolved organic matter (DOM). As the most crucial component of SOM, soil DOM plays a pivotal role in the carbon cycle and regulates the environmental fate of contaminants through its versatile reactivities, including electron-donating capacity (EDC). However, it is still being determined how wildfire influences key characteristics of soil DOM and subsequent effects on EDC in forest soils.

Identifying heavy metal sources and health risks in soil-vegetable systems of fragmented vegetable fields based on machine learning, positive matrix factorization model and Monte Carlo simulation.

Urban fragmented vegetable fields offer fresh produce but pose a potential risk of heavy metal (HM) exposure. Thus, this study investigated HM sources and health risks in the soil-vegetable systems of Chongqing's central urban area. Results indicated that Cd was the primary pollutant, with 28.

The different effects of molybdate on Hg(II) bio-methylation in aerobic and anaerobic bacteria.

In nature, methylmercury (MeHg) is primarily generated through microbial metabolism, and the ability of bacteria to methylate Hg(II) depends on both bacterial properties and environmental factors. It is widely known that, as a metabolic analog, molybdate can inhibit the sulfate reduction process and affect the growth and methylation of sulfate-reducing bacteria (SRB). However, after it enters the cell, molybdate can be involved in various intracellular metabolic pathways as a molybdenum cofactor; whether fluctuations in its concentration affect the growth and methylation of aerobic mercury methylating strains remains unknown.

The duality of sulfate-reducing bacteria: Reducing methylmercury production in rhizosphere but enhancing accumulation in rice plants.

Sulfate-reducing bacteria (SRB) are known to alter methylmercury (MeHg) production in paddy soil, but the effect of SRB on MeHg dynamics in rhizosphere and rice plants remains to be fully elucidated. The present study investigated the impact of SRB on MeHg levels in unsterilized and γ-sterilized mercury-polluted paddy soils, with the aim to close this knowledge gap. Results showed that the presence of SRB reduced MeHg production by ∼22 % and ∼17 % in the two soils, but elevated MeHg contents by approximately 55 % and 99 % in rice grains, respectively.

Soil organic matter degradation and methylmercury dynamics in Hg-contaminated soils: Relationships and driving factors.

Biodegradation of soil organic matter (SOM), which involves greenhouse gas (GHG) emissions, plays an essential role in the global carbon cycle. Over the past few decades, this has become an important research focus, particularly in natural ecosystems. SOM biodegradation significantly affects contaminants in the environment, such as mercury (Hg) methylation, producing highly toxic methylmercury (MeHg).

[Pollution Source Apportionment of Heavy Metals in Cultivated Soil Around a Red Mud Yard Based on APCS-MLR and PMF Models].

In order to explore the characteristics and sources of heavy metal pollution in cultivated soil around a red mud yard in Chongqing， the content and spatial distribution characteristics of eight heavy metal elements （Cd， Cr， Hg， Ni， Pb， As， Cu， and Zn） in the soil were analyzed， and the single factor pollution index method and Nemerow comprehensive pollution index method were used to evaluate the characteristics of heavy metal pollution in soil. On the basis of correlation analysis， the APCS-MLR and PMF models were used to quantitatively analyze the sources of heavy metals. The results showed that the average contents of the other seven heavy metal elements were higher than the background values of Chongqing soil， except for that of Cr.

Efficient and selective capture of various mercury species from water using an exfoliated thiocellulose.

The primary challenge in mercury (Hg) adsorbents for large-scale practical applications is to achieve the balance between performance and economy. This work attempts to address this issue by synthesizing an exfoliated thiocellulose (CU-SH) with high thiol density and hierarchical porosity using in-situ ligands grafting combined with chemical stripping. The prepared CU-SH shows remarkable physical stability and chemical resistance, and the micron sized fiber is conducive to separation from water.

Anthropogenic activities enhance mercury methylation in sediments of a multifunctional lake: Evidence from dissolved organic matter and mercury-methylating microorganisms.

Multifunctional lakes are highly susceptible to anthropogenic influences, potentially introducing exogenous pollutants or nutrients into aquatic sediments. This, in turn, affects the mercury (Hg) methylation in the sediments. This study was conducted in the Changshou Lake, a representative multifunctional lake in southwestern China, with a specific focus on investigating the Hg variations, the potential of Hg methylation, and the influential factors affecting the methylation process within sediments across different functional areas.

Selenium- and chitosan-modified biochars reduce methylmercury contents in rice seeds with recruiting Bacillus to inhibit methylmercury production.

Biochar could reshape microbial communities, thereby altering methylmercury (MeHg) concentrations in rice rhizosphere and seeds. However, it remains unclear whether and how biochar amendment perturbs microbe-mediated MeHg production in mercury (Hg) contaminated paddy soil. Here, we used pinecone-derived biochar and its six modified biochars to reveal the disturbance.

Assessment of tree-ring mercury radial translocation and age effect in Masson pine: Implications for historical atmospheric mercury reconstruction.

The tree ring has been regarded as an emerging archive to reconstruct historical atmospheric mercury (Hg) trends, but with the large knowledge gaps in the reliability. In this study, we comprehensively evaluated the Hg source, radial translocation and age effect of Masson pine (Pinus massoniana) tree ring at Mt. Jinyun in Chongqing, to assess the suitability of such tree ring as the archive of atmospheric Hg.