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Environmental Geochemistry and Health Mar 2024To assess the total daily mercury intake and main exposure sources of residents, six food groups, including marine fish, freshwater fish, poultry, livestock, vegetables,...
To assess the total daily mercury intake and main exposure sources of residents, six food groups, including marine fish, freshwater fish, poultry, livestock, vegetables, and cereals, were collected from five districts of Chengdu, China. The median concentrations of total mercury (THg) and methylmercury (MeHg) were 12.8 and 6.94 μg kg ww, respectively. Cereals (32.2%), vegetables (30.5%), and livestock (16.2%) contributed to a much larger extent to the total consumption for the participants in Chengdu. All food categories that contributed the most of THg (2.16 μg day) and MeHg 1.44 (μg day) to the daily intake in Chengdu were cereals and marine fish, respectively. The total Hazard Ratios values below 1 in this study indicate that there is no health risk associated with Hg ingestion from the consumption of these foods for the residents in Chengdu.
Topics: Animals; Humans; Mercury; Environmental Monitoring; Food Contamination; Methylmercury Compounds; Diet; Risk Assessment; Vegetables; Fishes; Edible Grain; China
PubMed: 38483661
DOI: 10.1007/s10653-024-01910-x -
Journal of Environmental Management Apr 2024Biodegradation of soil organic matter (SOM), which involves greenhouse gas (GHG) emissions, plays an essential role in the global carbon cycle. Over the past few...
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). However, the potential link between GHG production from SOM turnover in contaminated soils and biogeochemical processes involving contaminants remains unclear. In this study, we investigated the dynamics of GHG, MeHg production, and the relationship between biogeochemical processes in soils from two typical Hg mining sites. The two contaminated soils have different pathways, explaining the significant variations in GHG and MeHg production. The divergence of the microbial communities in these two biogeochemical processes is essential. In addition to the microbial role, abiotic factors such as Hg species can significantly affect MeHg production. On the other hand, we found an inverse relationship between CH and MeHg, suggesting that carbon emission reduction policies and management could inadvertently increase the MeHg levels. This highlights the need for an eclectic approach to organic carbon sequestration and contaminant containment. These findings suggest that it is difficult to establish a general pattern to describe and explain the SOM degradation and MeHg production in contaminated soils within the specific scenarios. However, this study provides a case study and helpful insights for further understanding the links between environmental risks and carbon turnover in Hg mining areas.
Topics: Methylmercury Compounds; Soil; Ecosystem; Soil Pollutants; Mercury; Carbon; Biodegradation, Environmental; Environmental Monitoring; Oryza
PubMed: 38479282
DOI: 10.1016/j.jenvman.2024.120432 -
Journal of Environmental Quality 2024Methylmercury (MeHg) is a human and environmental toxin produced in flooded soils. Little is known about MeHg in rice (Oryza Sativa L.) fields in Sacramento Valley,...
Methylmercury (MeHg) is a human and environmental toxin produced in flooded soils. Little is known about MeHg in rice (Oryza Sativa L.) fields in Sacramento Valley, California. The objectives of this study were to quantify mercury fractions in irrigation water and within rice fields and to determine their mercury pools in surface water, soil, and grain. Soil, grain, and surface water (dissolved and particulate) MeHg and total mercury (THg) were monitored in six commercial rice fields throughout a winter fallow season and subsequent growing season. Both dissolved and particulate mercury fractions were higher in fallow season rice field water. Total suspended solids and particulate mercury concentrations were positively correlated (r = 0.99 and 0.98 for THg and MeHg, respectively), suggesting that soil MeHg was suspended in the water column and potentially exported. Dissolved THg and MeHg concentrations were positively correlated with absorbance at 254 nm (r = 0.47 and 0.58, respectively) in fallow season field water. In the growing season, fields with higher irrigation water MeHg concentrations (due to recycled water use) had elevated field-water MeHg (r = 0.86) and grain MeHg concentrations (r = 0.96). Based on a mass balance analysis, soil mercury pools were orders of magnitude larger than surface water or grain mercury pools; however, fallow season drainage and grain harvest were the primary pathways for MeHg export. Based on these findings, reducing (1) discharge when water is turbid, (2) straw inputs, and (3) use of recycled irrigation water could help reduce mercury exports in rice field drainage water.
Topics: Oryza; Mercury; Agricultural Irrigation; Environmental Monitoring; Soil; Soil Pollutants; Water Pollutants, Chemical; California; Methylmercury Compounds
PubMed: 38468600
DOI: 10.1002/jeq2.20557 -
Environmental Pollution (Barking, Essex... Apr 2024Methylmercury (MeHg) is one of the most worrisome pollutants in marine systems. MeHg detoxification is mediated by merB and merA genes, responsible for the demethylation...
Methylmercury (MeHg) is one of the most worrisome pollutants in marine systems. MeHg detoxification is mediated by merB and merA genes, responsible for the demethylation of MeHg and the reduction of inorganic mercury, respectively. Little is known about the biological capacity to detoxify this compound in marine environments, and even less the bacterial transcriptional changes during MeHg detoxification. This study provides the genomic and transcriptomic characterization of the deep ocean bacteria Alteromonas mediterranea ISS312 with capacity for MeHg degradation. Its genome sequence revealed four mer operons containing three merA gene and two merB gene copies, that could be horizontally transferred among distant related genomes by mobile genetic elements. The transcriptomic profiling in the presence of 5 μM MeHg showed that merA and merB genes are within the most expressed genes, although not all mer genes were equally transcribed. Besides, we aimed to identify functional orthologous genes that displayed expression profiles highly similar or identical to those genes within the mer operons, which could indicate they are under the same regulatory controls. We found contrasting expression profiles for each mer operon that were positively correlated with a wide array of functions mostly related to amino acid metabolism, but also to flagellar assembly or two component systems. Also, this study highlights that all merAB genes of the four operons were globally distributed across oceans layers with higher transcriptional activity in the mesopelagic deeper waters. Our study provides new insights about the transcriptional patterns related to the capacity of marine bacteria to detoxify MeHg, with important implications for the understanding of this process in marine ecosystems.
Topics: Methylmercury Compounds; Ecosystem; Mercury; Bacteria; Gene Expression Profiling; Genomics; Alteromonas
PubMed: 38467369
DOI: 10.1016/j.envpol.2024.123725 -
Food Chemistry Jul 2024This study enhances the current limited understanding of the interaction between mercury (Hg) and selenium (Se) species in fish. Rainbow trout (Oncorhynchus mykiss), a...
This study enhances the current limited understanding of the interaction between mercury (Hg) and selenium (Se) species in fish. Rainbow trout (Oncorhynchus mykiss), a model aquaculture fish, was exposed to Hg and Se species through controlled dietary conditions. Over a 6-month feeding trial, the impact of dietary Se on Hg bioaccumulation in fish, including flesh, brain, and liver, was tracked. Twelve dietary conditions were tested, including plant-based diets (0.25 µgSe g) and tuna byproduct diets (0.25 µgHg g, 8.0 µgSe g) enriched with methylmercury and/or Se as selenite or selenomethionine. The tuna byproduct diet resulted in lower Hg levels than the plant-based diets, with muscle Hg content below the European Commission's safe threshold. This study highlights the significant impact of specific Se compounds in the diet, particularly from tuna-based aquafeed, on Hg bioaccumulation. These promising results provide a strong recommendation for future use of fisheries byproducts in sustainable aquafeeds.
Topics: Animals; Oncorhynchus mykiss; Selenium; Mercury; Selenomethionine; Diet; Selenious Acid
PubMed: 38461719
DOI: 10.1016/j.foodchem.2024.138865 -
The Science of the Total Environment May 2024Methylmercury (MeHg), as a global environmental pollutant, is of concern globally due to its neurodevelopmental toxicity. Mitochondria-associated membranes (MAMs) are...
Methylmercury (MeHg), as a global environmental pollutant, is of concern globally due to its neurodevelopmental toxicity. Mitochondria-associated membranes (MAMs) are highly dynamic sites of endoplasmic reticulum (ER)-haemocyte contact. MAMs are closely associated with the pathophysiology of neurological disorders due to their role in the transfer of calcium ions (Ca) between mitochondria and the ER. However, the molecular mechanisms that control these interactions in MeHg-induced neurotoxicity have not yet been characterized. In the current study, MeHg caused increases in the levels of both cytosolic and mitochondrial Ca in PC12 cells and promoted MAMs formation in both in vivo and in vitro experiments. Of note, MeHg perturbed mitochondrial dynamics, promoting a shift toward a fission phenotype, and this was supported by the dysregulation of fission regulators. Interestingly, the MeHg-induced promotion of MAMs formation and increase in Ca levels were effectively attenuated by the inhibition of mitochondrial fission using Mdivi-1, a DRP1 inhibitor. Furthermore, MeHg triggered the AMPK pathway, and most of the aforementioned changes were significantly rescued by Compound C. Mechanistic investigations revealed a reciprocal relationship between AMPK- and Ca-mediated mitochondrial fission. The specific inhibitor of Ca uniporter, ruthenium-red (RuR), effectively abolished the feedback regulation of mitochondrial dynamics and MAMs formation mediated by AMPK in response to MeHg-induced Ca overload. This study reveals a novel role of AMPK-DRP1-mediated mitochondrial fragmentation in the coupling of ER-mitochondrial calcium microdomains in MeHg-induced neurotoxicity. The findings provide valuable insights for the development of strategies to regulate mitochondrial imbalances in neurological diseases.
Topics: Rats; Animals; Calcium; Mitochondrial Dynamics; Methylmercury Compounds; AMP-Activated Protein Kinases; Mitochondria; Endoplasmic Reticulum; Homeostasis
PubMed: 38442753
DOI: 10.1016/j.scitotenv.2024.171398 -
Environmental Pollution (Barking, Essex... Apr 2024Straw amendment significantly enhances mercury (Hg) methylation and subsequent methylmercury (MeHg) bioaccumulation in Hg-contaminated paddy fields by releasing...
Straw amendment significantly enhances mercury (Hg) methylation and subsequent methylmercury (MeHg) bioaccumulation in Hg-contaminated paddy fields by releasing dissolved organic matter (DOM). This study comprehensively investigates the regulatory mechanisms of DOM and its different molecular weights derived from sulfur-rich rape straw (RaDOM) and composted rape straw (CRaDOM) applied in the rice-filling stage on soil MeHg production and subsequent bioaccumulation in rice grains. The results indicated that the amendment of RaDOM and CRaDOM significantly reduced soil MeHg content by 42.40-62.42%. This reduction can be attributed to several factors, including the suppression of Hg-methylating bacteria in soil, the supply of sulfate from RaDOM and CRaDOM, and the increase in the humification, molecular weight, and humic-like fractions of soil DOM. Additionally, adding RaDOM increased the MeHg bioaccumulation factor in roots by 27.55% while inhibiting MeHg transportation by 12.24% and ultimately reducing MeHg content in grains by 21.24% compared to the control group. Similarly, CRaDOM enhanced MeHg accumulation by 25.19%, suppressed MeHg transportation by 39.65%, and reduced MeHg levels in the grains by 27.94%. The assimilation of sulfate derived from RaDOM and CRaDOM into glutathione may be responsible for the increased retention of MeHg in the roots. Over the three days, there was a significant decrease in soil MeHg content as the molecular weight of RaDOM increased; conversely, altering the molecular weight of CRaDOM demonstrated an inverse trend. However, this pattern was not observed after 12 days. Applying sulfur-rich rape DOM can help mitigate MeHg accumulation in paddy fields by regulating the quality of soil DOM, sulfur cycling, and Hg-methylating bacteria.
Topics: Methylmercury Compounds; Mercury; Soil; Oryza; Dissolved Organic Matter; Soil Pollutants; Sulfates; Methylation; Brassica rapa
PubMed: 38428787
DOI: 10.1016/j.envpol.2024.123657 -
Properties influencing flux and diatom uptake of mercury and methylmercury from estuarine sediments.Environmental Pollution (Barking, Essex... Apr 2024Mercury (Hg) is a conspicuous and persistent global pollutant. Ionic Hg can be methylated into noxious methylmercury (CHHg), which biomagnifies in marine tropic webs and...
Mercury (Hg) is a conspicuous and persistent global pollutant. Ionic Hg can be methylated into noxious methylmercury (CHHg), which biomagnifies in marine tropic webs and poses a health risk to humans and organisms. Sediment Hg methylation rates are variable, and the output flux of created CHHg are dependent on sediment characteristics and environmental factors. Thus, uncertainties remain about the formation and flux of CHHg from sediment, and how this could contribute to the bioaccumulative burden for coastal organisms in shallow ecosystems. Cores were collected from 3 estuarine locations along the Eastern USA to examine how sediments characteristics influence the introduction of Hg and CHHg into the base of the food chain. Stable isotopes of inorganic Hg and CHHg were injected into sediments of individual cores, with cultured diatoms constrained to overlying waters. Five different treatments were done on duplicate cores, spiked with: (1) no Hg isotopes (control); (2) inorganic Hg; (3) CHHg; (4) both Hg and CHHg isotopes, (5) both Hg and CHHg into overlying waters (not sediment). Experimental cores were incubated for 3 days under temperature and light controlled conditions. These results demonstrate that upper sediments characteristics lead to high variability in Hg cycling. Notably, sediments which contained abundant and peaty organic material (∼28 %LOI), had the highest pore water DOC (3206 μM) and displayed bands of sulfur reducing bacteria yielded the greatest methylation rate (1.97 % day) and subsequent diatom uptake of CHHg (cell quota 0.18 amol/cell) in the overlying water.
Topics: Humans; Mercury; Methylmercury Compounds; Diatoms; Ecosystem; Water Pollutants, Chemical; Geologic Sediments; Isotopes; Water; Environmental Monitoring
PubMed: 38423275
DOI: 10.1016/j.envpol.2024.123604 -
Environmental Research Jun 2024During the last few decades, inputs of mercury (Hg) to the environment from anthropogenic sources have increased. The Ebro Delta is an important area of rice production...
During the last few decades, inputs of mercury (Hg) to the environment from anthropogenic sources have increased. The Ebro Delta is an important area of rice production in the Iberian Peninsula. Given the industrial activity and its legacy pollution along the Ebro river, residues containing Hg have been transported throughout the Ebro Delta ecosystems. Rice paddies are regarded as propitious environments for Hg methylation and its subsequent incorporation to plants and rice paddies' food webs. We have analyzed how Hg dynamics change throughout the rice cultivation season in different compartments from the paddies' ecosystems: soil, water, rice plants and fauna. Furthermore, we assessed the effect of different agricultural practices (ecological vs. conventional) associated to various flooding patterns (wet vs. mild alternating wet and dry) to the Hg levels in rice fields. Finally, we have estimated the proportion of methylmercury (MeHg) to total mercury in a subset of samples, as MeHg is the most bioaccumulable toxic form for humans and wildlife. Overall, we observed varying degrees of mercury concentration over the rice cultivation season in the different compartments. We found that different agricultural practices and flooding patterns did not influence the THg levels observed in water, soil or plants. However, Hg concentrations in fauna samples seemed to be affected by hydroperiod and we also observed evidence of Hg biomagnification along the rice fields' aquatic food webs.
Topics: Oryza; Spain; Mercury; Environmental Monitoring; Agriculture; Seasons; Animals; Methylmercury Compounds; Rivers; Soil Pollutants; Water Pollutants, Chemical
PubMed: 38412914
DOI: 10.1016/j.envres.2024.118555 -
Ecotoxicology (London, England) Mar 2024Terrestrial soils in forested landscapes represent some of the largest mercury (Hg) reserves globally. Wildfire can alter the storage and distribution of...
Terrestrial soils in forested landscapes represent some of the largest mercury (Hg) reserves globally. Wildfire can alter the storage and distribution of terrestrial-bound Hg via reemission to the atmosphere or mobilization in watersheds where it may become available for methylation and uptake into food webs. Using data associated with the 2007 Moonlight and Antelope Fires in California, we examined the long-term direct effects of wildfire burn severity on the distribution and magnitude of Hg concentrations in riparian food webs. Additionally, we quantified the cross-ecosystem transfer of Hg from aquatic invertebrate to riparian bird communities; and assessed the influence of biogeochemical, landscape variables, and ecological factors on Hg concentrations in aquatic and terrestrial food webs. Benthic macroinvertebrate methylmercury (MeHg) and riparian bird blood total mercury (THg) concentrations varied by 710- and 760-fold, respectively, and Hg concentrations were highest in predators. We found inconsistent relationships between Hg concentrations across and within taxa and guilds in response to stream chemical parameters and burn severity. Macroinvertebrate scraper MeHg concentrations were influenced by dissolved organic carbon (DOC); however, that relationship was moderated by burn severity (as burn severity increased the effect of DOC declined). Omnivorous bird Hg concentrations declined with increasing burn severity. Overall, taxa more linked to in situ energetic pathways may be more responsive to the biogeochemical processes that influence MeHg cycling. Remarkably, 8 years post-fire, we still observed evidence of burn severity influencing Hg concentrations within riparian food webs, illustrating its overarching role in altering the storage and redistribution of Hg and influencing biogeochemical processes.
Topics: Animals; Ecosystem; Wildfires; Rivers; Water Pollutants, Chemical; Invertebrates; Mercury; Methylmercury Compounds; Food Chain; Birds; Environmental Monitoring; Burns
PubMed: 38381206
DOI: 10.1007/s10646-024-02730-6