Thiol-functionalized cellulose for mercury polluted water remediation: Synthesis and study of the adsorption properties.

Mercury pollution poses a global health threat due to its high toxicity, especially in seafood where it accumulates through various pathways. Developing effective and affordable technologies for mercury removal from water is crucial. Adsorption stands out as a promising method, but creating low-cost materials with high selectivity and capacity for mercury adsorption is challenging. Here we show a sustainable method to synthesize low-cost sulfhydrylated cellulose with ethylene sulfide functionalities bonded glucose units. Thiol-functionalized cellulose exhibits exceptional adsorption capacity (1325 mg g-1) and selectivity for Hg(II) over other heavy metals (Co, Cu, Zn, Pb) and common cations (Ca++, Mg++) found in natural waters. It performs efficiently across a wide pH range and different aqueous matrices, including wastewater, and can be regenerated and reused multiple times without significant loss of performance. This approach offers a promising solution for addressing mercury contamination in water sources.

Multistress Interplay: Time and Duration of Ocean Acidification Modulate the Toxicity of Mercury and Other Metals.

The current understanding of multistress interplay assumes stresses occur in perfect synchrony, but this assumption is rarely met in the natural marine ecosystem. To understand the interplay between nonperfectly overlapped stresses in the ocean, we manipulated a multigenerational experiment (F0-F3) to explore how different temporal scenarios of ocean acidification will affect mercury toxicity in a marine copepod Pseudodiaptomus annandalei. We found that the scenario of past acidification aggravated mercury toxicity but current and persistent acidification mitigated its toxicity. We specifically performed a proteomics analysis for the copepods of F3. The results indicated that current and persistent acidification initiated the energy compensation for development and mercury efflux, whereas past acidification lacked the barrier of H+ and had dysfunction in the detoxification and efflux system, providing a mechanistic understanding of mercury toxicity under different acidification scenarios. Furthermore, we conducted a meta-analysis on marine animals, demonstrating that different acidification scenarios could alter the toxicity of several other metals, despite evidence from nonsynchronous scenarios remaining limited. Our study thus demonstrates that time and duration of ocean acidification modulate mercury toxicity in marine copepods and suggests that future studies should move beyond the oversimplified scenario of perfect synchrony in understanding multistress interaction.

Effects of sulfur nanoparticles on rhizosphere microbial community changes in oilseed rape plantation soil under mercury stress.

In the present study, experiments were conducted to assess the influence of nanoscale sulfur in the microbial community structure of metallophytes in Hg-contaminated rhizosphere soil for planting rapeseed. The results showed that the richness and diversity of the rhizobacteria community decreased significantly under Hg stress, but increased slightly after SNPs addition, with a reduction in the loss of Hg-sensitive microorganisms. Moreover, all changes in the relative abundances of the top ten phyla influenced by Hg treatment were reverted when subjected to Hg + SNPs treatment, except for Myxococcota and Bacteroidota. Similarly, the top five genera, whose relative abundance decreased the most under Hg alone compared to CK, increased by 19.05%-54.66% under Hg + SNPs treatment compared with Hg alone. Furthermore, the relative abundance of Sphingomonas, as one of the dominant genera for both CK and Hg + SNPs treatment, was actively correlated with plant growth. Rhizobacteria, like Pedobacter and Massilia, were significantly decreased under Hg + SNPs and were positively linked to Hg accumulation in plants. This study suggested that SNPs could create a healthier soil microecological environment by reversing the effect of Hg on the relative abundance of microorganisms, thereby assisting microorganisms to remediate heavy metal-contaminated soil and reduce the stress of heavy metals on plants.

In this manuscript, we first comprehensively investigated the changes in the rhizosphere microbial community structure of metallophytes in Hg-contaminated soil with SNPs addition, as well as the relationship between soil microbiology and plant resistance to Hg stress. Our results demonstrated that SNPs exhibit a significant advantage in improving rhizosphere microecology by increasing the abundance of beneficial rhizobacteria, thereby alleviating heavy metal toxicity, and promoting plant growth. This study is the first study describing the response of soil microorganisms coexposed to heavy metals and SNPs, providing valuable information for the potential use of SNPs to assist phytoremediation of toxic metal pollution and its impact on soil microbial communities.

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. Hg(II) adsorption tests in water demonstrate that CU-SH has broad working pH range (1-12), fast kinetics (0.64 g/(mg‧min)), high adsorption capacity (652.9 mg/g), outstanding selectivity (Kd = 6.2 × 106 mg/L), and excellent reusability (R > 95 % after 20 cycles). Importantly, CU-SH exhibits good resistance to various coexisting ions and organic matter, and can efficiently remove Hg(II) from different real water. CU-SH can be made into a Point of Use (POU) device for continuous and efficient removal of Hg(II) from drinking water. 0.1 g CU-SH filled device can purify 3.2 L of Hg(II) (0.5 ppm) contaminated tap water before the breakthrough point of 2 ppb. Moreover, CU-SH also reveals good adsorption affinity for Hg-dissolved organic matter complexes (Hg(II)-DOM) in water, chloro(phenyl)mercury (PMC) in organic media and Hg0 vapor in air, suggesting the great practical potential of CU-SH.

Spatial and temporal variations in the pollution status and sources of mercury in the Jiaozhou bay.

In the past few decades, mercury (Hg) discharged into the coastal bays of China has significantly increased; however, long-term trends regarding the pollution status and sources of Hg in these bays have yet to be clear. Focusing on this issue, surface sediments and core sediments were collected in the Jiaozhou Bay (JZB), a typical bay highly affected by human activities in China, to analyze the concentrations and stable isotopic composition of Hg. Total mercury (THg) concentrations in surface sediment varied from 7 to 163 ng/g, with higher levels located in the eastern JZB, possibly attributed to intensive industrial and population density. THg in sediment cores 14 and 20 displayed fluctuating increasing trends from 1936 to 2019, reflecting the deterioration of Hg pollution. In contrast, THg in sediment core 28 near the river mouth exhibited a declining trend, possibly due to the river dam construction. Using a stable isotope mixing model, contributions of various sources (atmospheric, riverine, and industrial emissions) to Hg in the JZB were estimated. The results showed that industrial emissions were the main source (over 50%) of mercury in the JZB in 2019. Sediment cores recorded an increase in industrial Hg due to early industrialization and Reform and Opening-up before 2000. In addition, sediment core 20 demonstrated a rise in the percentage of riverine Hg due to land reclamation at the bay's mouth during 2000-2007.

Accumulation and risk assessment of mercury in soil as influenced by mercury mining/smelting in Tongren, Southwest China.

To investigate the influence of mercury (Hg) mining/smelting on the surrounding soil environment, ninety soil samples were collected around Hg mining/smelting areas in Tongren city, Guizhou Province, Southwest China. The total mercury (THg), methylmercury (MeHg), bioavailability and fractions of Hg in the soil and their potential risk were evaluated. The results showed that Hg mining/smelting significantly increased the soil pH and decreased the soil organic matter content (p < 0.05). The THg content in the surrounding soil was much higher than that at the control site, with almost all the samples exceeding the national standard in China (3.4 mg/kg, GB15618-2018). Similarly, the concentrations of MeHg (0.09-2.74 µg/kg) and bioavailable Hg (0.64-62.94 µg/kg) in these soil samples were also significantly higher than those in the control site. However, the MeHg/THg ratio was significantly lower in mining/smelting influenced soils (0.01-0.68%) than in control soils (0.60-3.72%). Fraction analysis revealed that residual (RES-Hg) and organic matter-bounded (OM-Hg) Hg accounted for more than 50% of the THg. Ecological risk assessment revealed that the potential ecological risk for most of the Hg mining/smelting-influenced soils (30.16 ≤ Er ≤ 2280.02) were higher than those at the control site (15.12 ≤ Er ≤ 27.1). In addition, these Hg mining/smelting-influenced soils posed acceptable noncarcinogenic risks to adults (except for two soil samples), with hazard indices (HIs) ranging from 0.04 to 1.11 and a mean HI of 0.44. However, children suffer serious noncarcinogenic risks, with HIs ranging from 0.34 to 7.43 and a mean HI of 3.10.

Catchment land use effect on mercury concentrations in lake sediments: A high-resolution study of Qinghai Lake.

Mercury (Hg) contamination in aquatic environments presents a significant ecological and human health concern. This study explored the relationship between catchment land use and Hg concentrations within Qinghai Lake sediment, the largest lake in China, situated on the Qinghai-Tibet plateau. The study entailed detailed mapping of Hg sediment concentrations and a subsequent environmental risk assessment. Considering the complex nature of the plateau landform and surface vegetation, the study area was delineated at a 100 km radius centered on Qinghai Lake, which was divided into 30 sectors to quantify relationships between land use and the sediment Hg concentration. The results revealed a mean sediment Hg concentration of 29.91 µg/kg, which was elevated above the background level. Kendall's correlation analysis revealed significant but weak associations between sediment Hg concentrations and three land use types: grassland (rangeland and trees) (rs = 0.27, p < 0.05), crops (rs = -0.37, p < 0.05), and bare ground (rs = -0.25, p < 0.1), suggesting that growing areas of grassland correlated with higher Hg levels in the lake sediment, in contrast to bare ground or crops area, which correlated with lower Hg concentrations. Multiple linear regression models also observed weak negative relationships between bare ground and crops with sediment Hg concentration. This research methodology enhances our understanding of the impact of land use on Hg accumulation in lake sediments and underscores the need for integrated watershed management strategies to mitigate Hg pollution in Qinghai Lake.

Metabolisms of both inorganic and methyl-mercury in hens reveal eggs as an effective bioindicator for environmental Hg pollution.

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.

Tailored bacteria tackling with environmental mercury: Inspired by natural mercuric detoxification operons.

Mercury (Hg) and its inorganic and organic compounds significantly threaten the ecosystem and human health. However, the natural and anthropogenic Hg environmental inputs exceed 5000 metric tons annually. Hg is usually discharged in elemental or ionic forms, accumulating in surface water and sediments where Hg-methylating microbes-mediated biotransformation occurs. Microbial genetic factors such as the mer operon play a significant role in the complex Hg biogeochemical cycle. Previous reviews summarize the fate of environmental Hg, its biogeochemistry, and the mechanism of bacterial Hg resistance. This review mainly focuses on the mer operon and its components in detecting, absorbing, bioaccumulating, and detoxifying environmental Hg. Four components of the mer operon, including the MerR regulator, divergent mer promoter, and detoxification factors MerA and MerB, are rare bio-parts for assembling synthetic bacteria, which tackle pollutant Hg. Bacteria are designed to integrate synthetic biology, protein engineering, and metabolic engineering. In summary, this review highlights that designed bacteria based on the mer operon can potentially sense and bioremediate pollutant Hg in a green and low-cost manner.

Integrated transcriptomics and metabolomics reveal the toxic mechanisms of mercury exposure to an endangered species Tachypleus tridentatus.

Mercury (Hg) pollution is threatening the health of endangered Tachypleus tridentatus whereas the toxic mechanism is still unclear. This study combined transcriptomic and metabolomics technology to reveal the toxic mechanisms of mercury (Hg 2+, 0.025 mg/L) exposing to T. tridentatus larvae for 15 days. Mercury induced cellular toxicity and cardiovascular dysfunction by dysregulating the genes related to endocrine system, such as polyubiquitin-A, cathepsin B, atrial natriuretic peptide, etc. Mercury induced lipid metabolic disorder with the abnormal increase of lysoPC, leukotriene D4, and prostaglandin E2. Cytochrome P450 pathway was activated to produce anti-inflammatory substances to reconstruct the homeostasis. Mercury also inhibited arginine generation, which may affect the development of T. tridentatus by disrupting the crucial signaling pathway. The mercury methylation caused enhancement of S-adenosylmethionine to meet the need of methyl donor. The mechanisms described in present study provide new insight into the risk assessment of mercury exposure to T. tridentatus.

Revisiting the mercury cycle in marine sediments: A potential multifaceted role for Desulfobacterota.

Marine sediments impacted by urban and industrial pollutants are typically exposed to reducing conditions and represent major reservoirs of toxic mercury species. Mercury methylation mediated by anaerobic microorganisms is favored under such conditions, yet little is known about potential microbial mechanisms for mercury detoxification. We used culture-independent (metagenomics, metabarcoding) and culture-dependent approaches in anoxic marine sediments to identify microbial indicators of mercury pollution and analyze the distribution of genes involved in mercury reduction (merA) and demethylation (merB). While none of the isolates featured merB genes, 52 isolates, predominantly affiliated with Gammaproteobacteria, were merA positive. In contrast, merA genes detected in metagenomes were assigned to different phyla, including Desulfobacterota, Actinomycetota, Gemmatimonadota, Nitrospirota, and Pseudomonadota. This indicates a widespread capacity for mercury reduction in anoxic sediment microbiomes. Notably, merA genes were predominately identified in Desulfobacterota, a phylum previously associated only with mercury methylation. Marker genes involved in the latter process (hgcAB) were also mainly assigned to Desulfobacterota, implying a potential central and multifaceted role of this phylum in the mercury cycle. Network analysis revealed that Desulfobacterota were associated with anaerobic fermenters, methanogens and sulfur-oxidizers, indicating potential interactions between key players of the carbon, sulfur and mercury cycling in anoxic marine sediments.

Bridged EGFET Design for the Rapid Screening of Sorbents as Sensitisers in Water-Pollution Sensors.

We further simplify the most 'user-friendly' potentiometric sensor for waterborne analytes, the 'extended-gate field effect transistor' (EGFET). This is accomplished using a 'bridge' design, that links two separate water pools, a 'control gate' (CG) pool and a 'floating gate' (FG) pool, by a bridge filled with agar-agar hydrogel. We show electric communication between electrodes in the pools across the gel bridge to the gate of an LND150 FET. When loading the gel bridge with a sorbent that is known to act as a sensitiser for Cu2+ water pollution, namely, the ion exchanging zeolite 'clinoptilolite', the bridged EGFET acts as a potentiometric sensor to waterborne Cu2+. We then introduce novel sensitisers into the gel bridge, the commercially available resins PurometTM MTS9140 and MTS9200, which are sorbents for the extraction of mercury (Hg2+) pollution from water. We find a response of the bridged EGFET to Hg2+ water pollution, setting a template for the rapid screening of ion exchange resins that are readily available for a wide range of harmful (or precious) metal ions. We fit the potentiometric sensor response vs. pollutant concentration characteristics to the Langmuir-Freundlich (LF) model which is discussed in context with other ion-sensor characteristics.

Efficient and selective removal of mercury ions from aqueous solution by 2,5-dimercaptothiadiazole covalently grafted chitosan derivative.

The increasingly serious problem of mercury pollution has caused wide concern, and exploring the adsorbent materials with high adsorption capacity is a simple and effective approach to address this concern. In this study, chitosan (CS), 2,5-dimercaptothiadiazole (DMTD) and formaldehyde solution are used as raw materials to prepare the modified CS material (DMTD-CS) by one-pot method. Adequate characterizations suggest that DMTD-CS is highly cross-linked, and the specific surface area and pore volume are 126.91 m2/g and 0.6702 cm3/g, respectively. By investigating the Hg(II) adsorption properties of DMTD-CS, the maximum adsorption capacity at 318 K reaches 628.09 mg/g, this value is higher than that of CS and most of the reported CS derivatives. Adsorption kinetics and isotherms indicate that the adsorption behaviors of DMTD-CS conform to the pseudo-second-order kinetic model and Langmuir isotherm model, and in the coexistence of various metal ions, DMTD-CS shows very good selectivity for Hg(II). Additionally, the removal of DMTD-CS to Hg(II) is still at 80.06 % after six adsorption-desorption cycles, demonstrating outstanding recyclability. The further FT-IR and XPS analysis suggest that the synergistic complexation of O, N and S atoms on DMTD-CS with Hg(II) is an important factor leading to the high adsorption capacity.

High and diurnally fluctuating carbon dioxide exposure produces lower mercury toxicity in a marine copepod.

Coastal waters have experienced fluctuations in partial pressure of carbon dioxide (pCO2) and mercury (Hg) pollution, yet little is known concerning how natural pCO2 fluctuations affect Hg biotoxicity. Here, a marine copepod Tigriopus japonicus was interactively exposed to different seawater pCO2 (ambient 400, steady elevated 1000, and fluctuating elevated 1000 ± 600 µatm) scenarios and Hg (control, 2 µg/L) treatments for 7 d. The results showed that elevated pCO2 decreased Hg bioaccumulation, and it was even more under fluctuating elevated pCO2 condition. We found energy depletion and oxidative stress under Hg-treated copepods, while combined exposure initiated compensatory response to alleviate Hg toxicity. Intriguingly, fluctuating acidification presented more immune defense related genes/processes in Hg-treated copepods when compared to steady acidification, probably linking with the greater decrease in Hg bioaccumulation. Collectively, understanding how fluctuating acidification interacts with Hg contaminant will become more crucial in predicting their risks to coastal biota and ecosystems.

[Mercury Pollution in Dryland Soil and Evaluation of Maize Safety Production in Guizhou Province].

Guizhou Province is the province with the largest Hg production and reserves in China, and maize is the second largest grain crop in Guizhou Province. It is necessary to identify the status of soil Hg content in Guizhou Province and evaluate the safety of maize production. A total of 990 soil-maize samples and 270 single soil samples were collected in the main maize-producing areas to determine soil pH, cation exchange capacity (CEC), and organic matter content (SOM), as well as Hg content in soil and maize. The results showed that the pH of dryland soil in Guizhou Province ranged from 3.93 to 9.82, the geometric mean of ω(SOM) was 27.5 g·kg-1, and the geometric mean of CEC was 11.7 cmol·kg-1. Soil ω(Hg) ranged from 0.005 to 686 mg·kg-1, the geometric mean was 0.632 mg·kg-1, and the over-standard rate was 7.22%. Among them, the soil Hg pollution in Tongren was the most prominent, with the exceedance rate of 21.3%. At the county level, Danzhai County, Qiandongnan Miao and Dong Autonomous Prefecture, and Tongren City Wanshan District and Bijiang District had high exceedance rates of Hg. According to the Limit of Pollutants in Food according to National Standards for Food Safety (GB 2762-2017), the exceedance rate of Hg content in maize grains was 1.11%, and the exceedance points were mainly distributed around industrial and mining activity areas such as Wanshan District in Tongren City and Xixiu District in Anshun City. According to the results, there was serious soil Hg pollution in Guizhou Province. On the whole, maize can be safely planted, but it is necessary to pay close attention to the Hg content in grains and the Hg exposure risk of residents around industrial and mining areas.

Chitosan-Based Polymer Nanocomposites for Environmental Remediation of Mercury Pollution.

Mercury is a well-known heavy metal pollutant of global importance, typically found in effluents (lakes, oceans, and sewage) and released into the atmosphere. It is highly toxic to humans, animals and plants. Therefore, the current challenge is to develop efficient materials and techniques that can be used to remediate mercury pollution in water and the atmosphere, even in low concentrations. The paper aims to review the chitosan-based polymer nanocomposite materials that have been used for the environmental remediation of mercury pollution since they possess multifunctional properties, beneficial for the adsorption of various kinds of pollutants from wastewater and the atmosphere. In addition, these chitosan-based polymer nanocomposites are made of non-toxic materials that are environmentally friendly, highly porous, biocompatible, biodegradable, and recyclable; they have a high number of surface active sites, are earth-abundant, have minimal surface defects, and are metal-free. Advances in the modification of the chitosan, mainly with nanomaterials such as multi-walled carbon nanotube and nanoparticles (Ag, TiO2, S, and ZnO), and its use for mercury uptake by batch adsorption and passive sampler methods are discussed.

Emerging mercury and methylmercury contamination from new artisanal and small-scale gold mining along the Nile Valley, Egypt.

The past decade witnessed the initiation and boom of the Artisanal and Small-scale Gold Mining (ASGM) activities in the hyper-arid southern Egypt. The ores are mined in the Eastern Desert and then transported to the densely populated farming communities in the Nile Valley, where the river provides the water resources needed for ore processing. In search for economic benefits, the poorly educated farmers with limited technical resources transformed their cultivated lands into ASGM operations, exposing themselves, their families, the residents, and the Nile ecosystems to several environmental and occupational health problems. Using integrated remote sensing, field, geochemical, and isotopic analyses, we report the first inventory of ASGM-related total mercury (THg) and methylmercury (MeHg) levels in tailings, amalgamation-tailing ponds, and surface and groundwater with emphasis on the Edfu city and its surroundings. The field and remote sensing-based mapping of ASGM activities reveals clustering around the Nile waterways and suggests interaction of Hg contamination sources with their surrounding receptors. Common ASGM practices include release of contaminated water from unlined amalgamation-tailing ponds into irrigation and drainage canals, and spreading of tailings over cultivated soils. In a short period (10 years), the released Hg contaminated multiple media, including the surface water, the shallow and deep aquifers, and possibly the soil, crops, and livestock. THg levels in amalgamation-tailing ponds (1200-8470 ng/L) are fourfold higher than US EPA and eightfold the WHO thresholds. The contaminated waters released from amalgamation-tailing ponds raised THg levels in surface water (irrigation canals: 50-100 ng/L; drainage canals: THg: > 200 ng/L) and groundwater (shallow and deep aquifers: 80-500 ng/L). Our findings highlight the need to extend the adopted approach to cover the entire length of the Nile River and its valley and the importance of conducting awareness campaigns to educate residents and health care providers about potential ASGM-related environmental and health hazards.

Mercury in multimedia system of Itacaiúnas Basin, Brazilian Amazon: An integrated approach to understand its distribution, origin, and ecological risk.

This study presents the first integrated study on total Hg (THg) level in surface soil (SS), bottom soil (BS), stream sediments (SD), lake sediments (LS), stream water (SW), and lake water (LW) of Itacaiúnas River Watershed (IRW), Brazil to investigate the source and distribution of Hg in different environmental media considering contrasts of geological domains and sub-basins and its potential ecological and human risk. Hg content in most of the soils and sediments were above the upper crustal average values (56 µg/kg), however, when compared to the legal limits set by the Resolution CONAMA (Conselho Nacional de Meio Ambiente: soil 500 µg/kg; sediment 486 µg/kg), only 1 soil sample from Parauapebas sub-basin and 4 sediment samples from Violão Lake exceeded the limit. None of the SW and LW samples (<0.2 µg/L; CONAMA limit for Class II freshwater) are markedly contaminated by Hg. The SS and BS show similar contents and spatial distribution of Hg with higher contents being registered mostly in the Itacaiúnas and Parauapebas sub-basins, which are closely correlated with SD. This suggests that Hg levels are largely of geogenic origin and anthropogenic effect is highly limited. Principal Component Analysis (PCA) results show that Hg is strongly associated with total organic carbon (TOC), loss on ignition (LOI), and SO3, indicating organic matter as the main factor controlling the distribution of Hg and this is the major cause of accentuated Hg enrichment in lake sediments. The ecological risk index revealed a low pollution risk for most of the solid samples, except 11% LS and <1.5% SS and SD samples, which registered moderate risk. Health risk assessment indicated no adverse non-carcinogenic health effect on either adults and children in terms of Hg contamination. This information will be useful for Hg risk assessment in the Carajás region and future environmental research in this direction in the Amazonia.

The spatial analysis, risk assessment and source identification for mercury in a typical area with multiple pollution sources in southern China.

Mercury (Hg) has always been a research hot spot because of its high toxicity. This study conducted in farmland near rare earth mining area and traffic facilities, which considered multiple pollution sources innovatively. It not only analyzed Hg spatial characteristics using inverse distance weighting and self-organizing map (SOM), but also assessed its pollution risk by potential ecological risk index (Er) as well as geoaccumulation index (Igeo), and identified the pollution sources with positive matrix factorization. The results showed that there was no heavy Hg pollution in most farmland, while a few sampling sites with Hg pollution were close to highway, railway station and petrol station in Xinfeng or in the farmland of Anyuan, which were divided into the cluster with highest Hg concentration in SOM. The vehicle exhaust emission and pesticide as well as fertilizer additions significantly contributed to the local Hg pollution. Besides, there was moderate pollution and high ecological risk in Anyuan assessed by Igeo and Er, respectively. In contrast, Xinfeng had the moderate and considerable ecological risks in a larger scale. The enriched Hg might harmed not only the nearby ecological environment, but also the human health when it entered human body through food chain. The three factors that contributed to mercury concentration in this area according to positive matrix factorization were natural source, traffic source and agricultural source, respectively. This study about Hg pollution in the typical area would provide scientific evidence for the particular treatment of Hg pollution from various pollution sources like traffic source, agricultural source, etc.

Total mercury in different egg tissues provides insights to mercury metabolisms in bird bodies.

Mercury (Hg) pollution in birds has been widely reported, but the metabolism of Hg in bird bodies remains unclear. Measurement of Hg concentrations in bird tissues (muscles and organs) could provide insights into the metabolism of Hg in bird bodies, however, this approach is often invasive. To avoid invasive procedures, we conducted feeding experiments using chickens and used eggs as a proxy for understanding Hg metabolism in chicken bodies. For the control group, various THg concentrations were observed in egg whites, egg yolks, and eggshells, but the THg concentration trends for different egg tissues were not statistically different (P > 0.05). For the Hg feeding group (0.3 mg/kg body weight, feeding once), Hg peaks were observed in egg yolks and egg whites at different time periods, suggesting different response time to dietary Hg in chicken body tissues. Mercury in egg yolks peaked at Day 6, suggesting their quick response to dietary Hg. Egg whites reached Hg peak at Day 20, exhibiting a slower response to dietary Hg. Eggshells did not show a Hg peak, perhaps due to their predominant inorganic components that do not trigger Hg bioaccumulation. We measured THgyolk/THgwhite ratios in various chicken eggs purchased from three areas in Guizhou, SW China. The THgyolk/THgwhite ratios for Huaxi, Hezhang and Wuchuan were 1.33 (0.57-2.41), 7.89 (4.27-19.47) and 2.64 (1.68-4.22), respectively, to suggest different exposure history for chickens. This study provides new insights into the metabolism and lifetime of Hg in bird bodies.