Organic Mercury Concentrations Research Articles

Degradation of organic mercury in high salt environments by a marine aerobic bacterium Alteromonas macleodii KD01

Mercury (Hg), particularly organic mercury, poses a global concern due to its pronounced toxicity and bioaccumulation. Bioremediation of organic mercury in high-salt wastewater faces challenges due to the growth limitations imposed by elevated Cl− and Na+ concentrations on microorganisms. In this study, an isolated marine bacterium Alteromonas macleodii KD01 was demonstrated to degrade methylmercury (MeHg) efficiently in seawater and then was applied to degrade organic mercury (MeHg, ethylmercury, and thimerosal) in simulated high-salt wastewater. Results showed that A. macleodii KD01 can rapidly degrade organic mercury (within 20 min) even at high concentrations (>10 ng/mL), volatilizing a portion of Hg from the wastewater. Further analysis revealed an increased transcription of organomercury lyase (merB) with rising organic mercury concentrations during the exposure process, suggesting the involvement of mer operon (merA and merB). These findings highlight A. macleodii KD01 as a promising candidate for addressing organic mercury pollution in high-salt wastewater.

The protective role of virgin olive oil and vitamin E on mercury-induced hepatic, renal, testicular and adrenal toxicity in the rabbit (Oryctolagus cuniculus)

This study aimed to strengthen the antioxidant defenses against the toxic effect of mercury, by administering a synthetic antioxidant (vitamin E) and a natural product rich in antioxidant compounds (virgin olive oil) to rabbits. Hepatic and renal biomarker levels, cortisol and testosterone synthesis, mercury concentration, relative weight of organs, and tissue architecture were studied. The results showed a significant decrease in the plasma alkaline phosphatase (ALP), plasma aspartate aminotransferase (AST), serum alanine aminotransferase (ALT), plasma testosterone levels, and relative weight of the liver, testes, and adrenal in the mercury treated group (group M), while the other indices were significantly increased in the m-group compared to the control (group C). However, the group treated with olive oil combined with mercury (group O) showed a significant decrease in the ALP, AST, ALT, testosterone levels, and adrenal relative weight, while plasma creatinine, uric acid levels, mercury concentration in organs, and the kidney relative weight were significantly increased. Vitamin E supplementation (group E) led to a significant decrease in the ALP, testosterone levels, and adrenal relative weight, a significant increase was observed in plasma levels of triglycerides, creatinine, and uric acid. Histological sections of the liver, kidney, testis, and adrenal of group M showed severe tissue damage, while the other groups showed less important tissue alterations demonstrating that supplementation with natural or synthetic antioxidants can protect against the toxicity of heavy metals such as mercury, improving the health of rabbits.

Impact of mercury discharged from submarine volcano on inner bay ecosystems

Organic mercury, inorganic mercury and total mercury concentrations in phytoplankton (<0.1 mm) and zooplankton (>0.1 mm) collected in Kagoshima Bay, Japan were measured from 2017 to 2019 to estimate the impact of mercury discharged from submarine volcanoes on ecosystems; submarine volcanic activity continues at a depth of 200 m in the inner part of Kagoshima Bay. The total mercury concentrations in phyto- and zooplankton collected by vertical hauling at 0–200 m at just above the submarine volcano were in the range of 0.11–2.0 mg kg−1 (avg. 0.67 mg kg−1) and 0.090–0.56 mg kg−1 (avg. 0.21 mg kg−1), respectively. These values were one order of magnitude higher than the values in plankton collected in the central part of Kagoshima Bay. Organic mercury concentrations in phyto- and zooplankton were <0.010–0.071 mg kg−1 (avg. 0.028 mg kg−1) and 0.012–0.25 mg kg−1 (avg. 0.10 mg kg−1), respectively, for the inner part, and <0.010–0.040 mg kg−1 (avg. 0.010 mg kg−1) and <0.010–0.025 mg kg−1 (avg. 0.012 mg kg−1), respectively, for the central part. The values obtained in the inner part of the bay increased in summer and decreased in winter, which was consistent with changes in seawater mercury concentrations affected by volcanic activity. The organic mercury concentration in zooplankton collected just above the submarine volcano showed a size dependency, and a higher value was observed in the larger size, which suggested that the discharged mercury from the volcano was absorbed and concentrated through the ecosystem.

The Total Mercury Concentration in Organs of Eurasian Magpies (Pica pica) and Common Woodpigeons (Columba palumbus) from the Warsaw Municipal Area.

Mercury is a toxic element widely distributed in the natural environment, affecting animals' health. It is released into the environment from both natural and anthropogenic sources. The present study analyzed the mercury concentrations in liver, kidney, heart and muscle tissue in two species of birds from the Warsaw area, which were used as bioindicators of local environmental pollution with this metal. The mercury content in the examined samples was determined using atomic absorption spectrometry (AAS) utilizing automatic mercury analyzer type AMA 254. The highest mercury content was found in the body of Eurasian magpies, in which it was 0.025; 0.021; 0.006; 0.0037 and 0.029 mg kg-1 of tissue wet weight for kidney, liver, heart, thigh muscles and pectoral muscles, respectively. In the case of common woodpigeons, the content of this metal was significantly lower, amounting to 0.007; 0.005; 0.002; 0.001 and 0.001 mg∙kg-1 wet weight for kidney, liver, heart, thigh muscles and pectoral muscles, respectively. In light of data from the available literature, the values obtained should be considered low, not causing a risk to animal health. The results obtained indicate low environmental exposure to this element.

The dynamics of mercury around an artisanal and small-scale gold mining area, Camarines Norte, Philippines.

To elucidate the dynamics of mercury emitted and released by artisanal and small-scale gold mining (ASGM) activity and to estimate its impact on the ecosystems of the bay, the distribution of mercury in the atmosphere, soil, water, and sediment around Mambulao Bay, Camarines Norte, Philippines, was investigated. The ASGM operations use mercury to extract gold from ore and are located on the east shore side of the bay. Samplings were conducted in August 2017 and September 2018. The samples were used for determination of total mercury (T-Hg) and organic mercury (org-Hg) concentrations, total organic carbon (TOC) content, and chemical composition. The atmospheric mercury concentration on the east shore side, 6.1-25.8ngm-3, was significantly higher than the value of 1.4-9.9ngm-3 observed on the west shore side. The average concentrations of T-Hg in the forest soils of the west shore side and those of the east shore side were 0.081 ± 0.028mgkg-1 and 0.496 ± 0.439mgkg-1, respectively. In the vertical distribution of T-Hg in the soil of the east shore side, a higher concentration was observed near the surface. For the vertical variations in T-Hg in the marine sediment, higher values were observed near the estuary, and the vertical variations in core samples showed an increase in mercury concentration toward the surface. The highest concentration of T-Hg in sediment, 9.5mgkg-1, which was 2 orders of magnitude higher than the background levels of this area, was found near the river mouth. The T-Hg, org-Hg, and TOC levels showed a positive correlation, suggesting that the rivers are the main sources of T-Hg and org-Hg in the bay. Although the fish sample containing a mercury content higher than the regulatory level for fish and shellfish of 0.4mgkg-1 in Japan was only one of 42 samples, the percentage of org-Hg in fish samples was 91 ± 18%. Mercury released into the surroundings by the ASGM activities can be converted into methylmercury and affect the bay's ecosystem.

Carbon cycle perturbation and mercury anomalies in terrestrial Oceanic Anoxic Event 1b from Jiuquan Basin, NW China

Abstract Oceanic Anoxic Event (OAE) 1b is well documented in western Tethys; however, records in Eurasia are still lacking. Here, we carried out high-resolution organic carbon isotope (δ 13 C org ), total organic carbon (TOC) content and mercury (Hg) concentration analysis of the lacustrine sediments from the Xiagou and Zhonggou formations in the Hanxiagou section of the Jiuquan Basin, NW China. The lacustrine δ 13 C org curve presents three stages of negative excursions above the basalt layer dated at 112.4 ± 0.3 Ma in the lowermost Zhonggou Formation. The three negative δ 13 C org excursions correspond well with the three sub-events (Kilian, Paquier and Leenhardt) of the OAE 1b in the Poggio le Guaine (central Italy), Vocontian Basin (SE France) and St Rosa Canyon (NE Mexico) sections, supporting the record of the terrestrial OAE 1b in the Jiuquan Basin. Five mercury enrichment intervals in Hg/TOC ratios were recognized, indicating that the pulsed volcanism from the Southern Kerguelen Plateau likely triggered OAE 1b. However, the decoupling between negative isotopic excursion shifts and mercury enrichments, signifying another carbon reservoir (with no link to mercury), probably contributed to the global carbon cycle perturbation during the OAE 1b period. Our results provide direct evidence to link OAE 1b and the terrestrial ecosystem in Eurasia.

Coupled hydrological and geochemical impacts of wildfire in peatland-dominated regions of discontinuous permafrost

Naturally-ignited wildfires are increasing in frequency and severity in northern regions, contributing to rapid permafrost thaw-induced landscape change driven by climate warming. Low-severity wildfires typically result in minor organic matter loss. The impacts of such fires on the hydrological and geochemical dynamics of peat plateau-wetland complexes have not been examined. In 2014, a low-severity wildfire, with minimal ground surface damage, burned approximately one-half of a 5 ha permafrost plateau in the wetland-dominated landscape of the Scotty Creek watershed, Northwest Territories, Canada, in the discontinuous permafrost zone. In March 2016, hydrometeorological and permafrost conditions on the burned and unaffected plateaus were monitored including snowpack characteristics and surface energy dynamics. Pore water samples were collected from the saturated layer as thaw progressed throughout the growing season on the burned and unaffected plateaus. Repeated probing of the frost table depth was coupled with laboratory analyses of peat physical and hydraulic characteristics performed on peat cores collected from the top 20 cm of the ground surface in the burned and unaffected plots. The higher transmissivity of the burned forest canopy accelerated snowmelt promoting earlier onset of the thawing season and increased the ground heat flux to melt ground ice. Wildfire increased the thickness of the supra-permafrost layer, including the active layer and talik, resulting in a more uniform subsurface with limited depressional storage capacity and reduced preferential runoff flowpaths across the burned plateau. The incorporation of ash and char into the peat matrix reduced pore diameters, promoting greater subsurface soil moisture retention and longer pore water residence times ultimately providing greater opportunity for soil-water interaction and biogeochemical reactions. Consequently, pore water showed elevated dissolved solutes, dissolved organic matter and mercury concentrations in the burned site. Low-severity wildfires have the potential to trigger a series of complex, inter-related hydrological, thermal and biogeochemical processes and feedbacks.

Total and Organic Mercury in Fish from Different Geographical Areas in the North Atlantic Ocean and Health Risk Assessment

Fish consumption is considered the main route of exposure to mercury for the human population. In this sense, this study analysed the total and organic mercury content present in the muscle tissue of 38 fish species caught in different geographical areas of the North Atlantic Ocean (included in FAO fishing areas 27 and 31). The potential risk to human health through fish consumption was assessed using the maximum limit for mercury intake of 1.3 μg methylmercury Kg body weight−1 week−1. The results show that carnivorous species presented higher mercury content (range 0.03–0.88 μg g−1) when compared to omnivorous (range 0.003–0.19 μg g−1) in all sampling sites. Furthermore, demersal fish exhibited higher mercury levels (range 0.01–0.88 μg g−1) than the pelagic species (range 0.003–0.38 μg g−1) did. From the 38 species analysed only Zeus faber presented mercury levels (0.68 ± 0.07 μg g−1) above the maximum limit (0.5 μg g−1) established for human consumption. On the other hand, mercury intake can be higher than the recommended due to the consumption of 13 species from fishing area 27 (Azores archipelago and Northwest Portuguese coast) and one species (Cynoscion nebulosus) from fishing area 31 (Southeast Mexican coast). However, only the consumption of Zeus faber and Aphanopus carbo from the fishing area 27 is discouraged. Thus, the fish consumption per capita in a specific area can exceed the limits of mercury ingestion, even when the mercury content in the fish is below the recommended for consumption.

Total and organic Hg in fish from the reservoir of a chlor-alkali plant in Tainan, Taiwan

Total mercury (THg) and organic mercury (OHg) concentrations were determined by cold-vapor AAS in ten species of fish, which were caught in the reservoir of a chlor-alkali plant in Tainan, Taiwan that had been abandoned for 22 years. The fishes, including Elops machnata, Pelates quadrilineatus, Gerres filamentosus, Leiognathus equulus, Thryssa hamiltonii, Orechromis spp., Nematalosa come, Liza macrolepis, Mugil cephalus and Chanos chanos, were sampled from September to October 2003. THg and OHg concentrations (μg/g flesh wt.) in fish muscles were 0.43 ± 0.36 and 0.31 ± 0.21, respectively, similar to values reported from various chlor-alkali plants worldwide. Of the OHg values, 37% exceeded the food safety limit of 0.3 μg/g set by the World Health Organization. Moreover, 77% of the tested OHg values were over 0.17 μg/g, which had been suggested for seafood safety limit in Taiwan. Finally, 100 g of fish muscle is the maximum allowable weekly consumption amount for the adult residents to avoid health treat that arise from ingesting toxic OHg.

Distribution of total and organic mercury in soils around an artisanal and small-scale gold mining area in West Java, Indonesia

This study was conducted to understand the environmental behavior of mercury released by artisanal and small-scale gold mining (ASGM) activities. For this purpose, we attempted to assess the effect of diffused mercury on mercury concentrations in soil, demonstrate the presence of methylmercury in soil affected by the deposited mercury and determine the reactions associated with methylmercury production. The vertical profiles of mercury were obtained from two sites in the forest of the ASGM village in Pongkor (West Java, Indonesia) and from two sites in Mount Halimun-Salak National Park, which is approximately 12 km from the ASGM village. The highest total mercury concentration, 8.9 mg kg−1, was observed for soil samples collected at the ASGM village. The mercury was concentrated at the surface or in the subsurface layers, and the concentrations were several times to more than ten times higher than the lowest values observed in the deeper layers at each site. Even in the national park, the highest concentration of 1.9 mg kg−1 was observed in the upper soil layer. These results suggest that the primary source of mercury in the forest soil is atmospheric deposition; fallen plant leaves also deliver accumulated mercury to the soil surface. The organic mercury percentages of the total mercury were 0.2 ± 0.1% for the national park and 0.3 ± 0.2% for ASGM sites. The vertical variation in organic mercury concentration did not always match that in total mercury concentration, which suggested that the formation of methylmercury in soil was closely related to the decomposition of organic matter near the surface. The soil surface is an important reaction field for methylmercury production in forested areas.

Mercury concentrations in paddy field soil and freshwater snails around a small-scale gold mining area, West Java, Indonesia

To estimate the impact of mercury released from an artisanal small-scale gold mining (ASGM) activities on the ecosystem. Total and organic mercury concentrations in paddy field soil and freshwater snails around an artisanal small-scale gold mining area were investigated. Paddy field soil samples and freshwater snails were collected from ten sites along the Cikaniki River. A site located in a national park, which was approximately 12 km upstream from the ASGM site, was considered the reference site for this study. The organic mercury concentration in soil samples collected at the ASGM site was n.d.–0.018 mg kg−1 and that at the reference site was 0.005–0.008 mg kg−1. The organic mercury concentrations in the freshwater snails collected at the ASGM and reference sites were 0.38 ± 0.21 mg kg−1 (31.0 ± 26.6% of total mercury, n = 38) and 0.056 ± 0.032 mg kg−1 (40.5 ± 11.5% of total mercury, n = 16), respectively. Although the original form of mercury in the mining waste was elemental mercury and/or Hg2+, the mercury form changed to organic mercury in environment and the organic mercury was concentrated two orders of magnitude, even in low-order organisms.

Oxidative Damage in Human Periodontal Ligament Fibroblast (hPLF) after Methylmercury Exposure.

Human exposure to mercury (Hg) is primary associated with its organic form, methylmercury (MeHg), through the ingestion of contaminated seafood. However, Hg contamination is also positively correlated with the number of dental restorations, total surface of amalgam, and organic mercury concentration in the saliva. Among the cells existing in the oral cavity, human periodontal ligament fibroblast (hPLF) cells are important cells responsible for the production of matrix and extracellular collagen, besides sustentation, renewal, repair, and tissue regeneration. In this way, the present study is aimed at investigating the potential oxidative effects caused by MeHg on hPLF. Firstly, we analyzed the cytotoxic effects of MeHg (general metabolism status, cell viability, and mercury accumulation) followed by the parameters related to oxidative stress (total antioxidant capacity, GSH levels, and DNA damage). Our results demonstrated that MeHg toxicity increased in accordance with the rise of MeHg concentration in the exposure solutions (1-7 μM) causing 100% of cell death at 7 μM MeHg exposure. The general metabolism status was firstly affected by 2 μM MeHg exposure (43.8 ± 1.7%), while a significant decrease of cell viability has arisen significantly only at 3 μM MeHg exposure (68.7 ± 1.4%). The ratio among these two analyses (named fold change) demonstrated viable hPLF with compromised cellular machinery along with the range of MeHg exposure. Subsequently, two distinct MeHg concentrations (0.3 and 3 μM) were chosen based on LC50 value (4.2 μM). hPLF exposed to these two MeHg concentrations showed an intracellular Hg accumulation as a linear-type saturation curve indicating that metal accumulated diffusively in the cells, typical for metal organic forms such as methyl. The levels of total GSH decreased 50% at exposure to 3 μM MeHg when compared to control. Finally, no alteration in the DNA integrity was observed at 0.3 μM MeHg exposure, but 3 μM MeHg caused significant damage. In conclusion, it was observed that MeHg exposure affected the general metabolism status of hPLF with no necessary decrease on the cell death. Additionally, although the oxidative imbalance in the hPLF was confirmed only at 3 μM MeHg through the increase of total GSH level and DNA damage, the lower concentration of MeHg used (0.3 μM) requires attention since the intracellular mercury accumulation may be toxic at chronic exposures.

Seabird-Transported Contaminants Are Reflected in the Arctic Tundra, But Not in Its Soil-Dwelling Springtails (Collembola).

Arctic-breeding seabirds contain high levels of many anthropogenic contaminants, which they deposit through guano to the tundra near their colonies. Nutrient-rich soil in vicinity to seabird colonies are favorable habitats for soil invertebrates, such as springtails (Collembola), which may result in exposure to seabird-derived contaminants. We quantified a wide range of lipid-soluble and protein-associated environmental contaminants in two springtail species (Megaphorura arctica and Hypogastrura viatica) and their respective habitats (soil/moss) collected underneath seabird cliffs. Although springtails are commonly used in laboratory toxicity tests, this is the first study to measure concentrations of persistent organic pollutants (POPs) and mercury (Hg) in springtails from the field, and to study biotransportation of contaminants by seabirds to soil fauna. We categorized the sites a priori as of low, medium, or high seabird influence, based on the seabird abundance and species composition. This ranking was reflected in increasing δ15N values in soil/moss and springtails with increasing seabird influence. We found clear indications of seabirds impacting the terrestrial soil environments with organic contaminants, and that concentrations were higher in soil and moss close to the bird cliff, compared to farther away. However, we did not find a relationship between contaminant concentration in springtails and the concentrations in soil/moss, or with level of seabird influence. Our study indicates a low uptake of contaminants in the soil fauna, despite seabird-derived contamination of their habitat.

Baseline concentrations of mercury species within sediments from Qatar's coastal marine zone

Baseline concentration of total mercury (THg), organic extractable mercury and methylmercury (CH3Hg) concentrations in sediments from the northeastern, eastern and southeastern parts of the Arabian Gulf were assessed. Surface sediments were collected from eleven stations from the coastal waters of Qatar. All analyses were performed on homogenised samples. Total mercury analysis was performed by Cold Vapour Atomic Absorption Spectrometry (CVAAS), and methylmercury was analysed by Cold Vapour Atomic Fluorescence spectrometry (CVAFS) after aqueous phase ethylation of the extracted samples. Total mercury (THg) in sediments varied from 8.0 μg/kg to 34.3 μg/kg. Methylmercury was detected in all stations and ranged from 1.46 μg/kg to 3.10 μg/kg accounting for 5.4% to 18.4% of total mercury. Total organic carbon (TOC) ranged from 0.16 to 0.72%, while Organic extractable mercury ranged from 1.55 μg/kg to 13.3 μg/kg. Analysis, the grain size within these sediments, was carried out previously paving the way for studying the influence of these parameters on the sedimentary mercury concentration. Speciation was also assessed, as were relations between the measured mercury fractions.

Tuna byproducts as a fish-meal in tilapia aquaculture

Potentiality of the use of tuna byproducts as a fish-meal replacement on Nile tilapia (Oreochromis niloticus) was examined for 84 weeks by tracking the concentrations of cadmium and mercury in the internal organs, muscles and fish whole body through generation including their immature eggs and their larvae. The results confirmed that the tuna byproducts can be used as a fish-meal substitute in tilapia aquaculture, because their acceptable ranges for cadmium and mercury consequently did not exceed the food safety values (both < 0.5 mg kg−1), despite their proportional increases in the fish body. The use of tuna byproducts as a protein source is expected to reduce the cost of feed with other fishmeal substitutes in tilapia aquaculture. However, fish (flounder) indiscriminately consuming tuna byproduct feed were prohibited and recalls of sales were issued by the government (July 2018, Republic of Korea), as the threshold for mercury in the fish bodies had been exceeded (0.6–0.8 mg kg−1). Further study of the use of tuna byproducts as fishmeal replacements for other species in aquaculture is needed, as concentration ratios can vary depending on the species.

Role of bacterial esterase on mercury dynamics in mangrove sediments

Tropical estuarine areas present microbial and geochemical conditions that have been pointed out as important conditions to trigger the mechanisms of mercury methylation improving its bioavailability to higher trophic levels. Despite the potential risk of these mechanisms to human health, few studies have reported in situ analysis in costal subtropical ecosystems, relating bacterial activity and mercury concentrations. In the present work we analyze the relationship between some relevant environmental parameters that may stimulate the bacterial activity and control mercury concentrations in the sediments of a tropical mangrove tidal flat. Forty-four samples were collected and analyzed for total organic carbon, bacterial organic carbon, lipids, proteins, esterase activity and mercury concentrations and SEM/AVS. The redox potential, temperature and pH were also measured in situ. The results showed intense bacterial activity and increasing mercury levels when compared with local backgrounds. The use of SEM/AVS indicator recommended by USEPA as a criterium to check the sediment quality, did not show enough accuracy to predict the ecological bioavailability risk in sediments with high organic matter content. This methodology requires new approach to help decision making.

Spatial variability in total and organic mercury levels in Antarctic krill Euphausia superba across the Scotia Sea

Total and organic mercury concentrations were determined for males, females and juveniles of Euphausia superba collected at three discrete locations in the Scotia Sea (South Orkney Islands, South Georgia and Antarctic Polar Front) to assess spatial mercury variability in Antarctic krill. There was clear geographic differentiation in mercury concentrations, with specimens from the South Orkney Islands having total mercury concentrations 5 to 7 times higher than Antarctic krill from South Georgia and the Antarctic Polar Front. Mercury did not appear to accumulate with life-stage since juveniles had higher concentrations of total mercury (0.071 μg g−1 from South Orkney Islands; 0.014 μg g−1 from South Georgia) than adults (0.054 μg g−1 in females and 0.048 μg g−1 in males from South Orkney Islands; 0.006 μg g−1 in females and 0.007 μg g−1 in males from South Georgia). Results suggest that females may use egg laying as a mechanism to excrete mercury, with eggs having higher concentrations than the corresponding somatic tissue. Organic mercury makes up a minor percentage of total mercury (15–37%) with the percentage being greater in adults than in juveniles. When compared to euphausiids from other parts of the world, the concentration of mercury in Antarctic krill is within the same range, or higher, highlighting the global distribution of this contaminant. Given the high potential for biomagnification of mercury through food webs, concentrations in Antarctic krill may have deleterious effects on long-lived Antarctic krill predators.

Levels of Mercury in Fish-Eating Children, With and Without Amalgam Restoration.

Background:Mercury is a naturally occurring metal that exists in three forms: elemental (metallic), inorganic, and organic mercury. Amalgam, which is an alloy of inorganic mercury, is used as a restorative material in dentistry. Organic mercury gets ingested in the body mainly by the consumption of seafood. Mercury is also stated to cause various adverse health effects such as gastrointestinal disturbances, dermatitis, muscle weakness, and neurological disorders. In recent years, the use of amalgam has become a controversy stating the various adverse effects of mercury. Hence, the study was conducted to determine and compare the variation in levels of organic and inorganic mercury in fish-eating children before and after placement of amalgam restoration.Materials and Methods:Seventy-five subjects, 42 males (56%) and 35 females (44%) of age group ranging 7–13 years, living in South Canara district of Karnataka, India, were selected as a part of the study. Hair and urine samples were collected for estimation of organic and inorganic levels of mercury, respectively. Informed consent was collected from all the participating subjects.Results:On comparison between organic and inorganic mercury levels during the study period, the concentration of organic mercury in hair samples was greater irrespective of amalgam restorations present (1.172 and 0.085, respectively; P < 0.001).Conclusion:Thus inorganic levels of mercury do not seem to pose a threat as much as the organic levels observed in hair, which remain fairly constant for a longer period of time. Hence in a coastal region where this study was undertaken and fish being a staple food, the risk could probably be attributed to more of an organic toxicity than an inorganic one. Thus amalgam is relatively safe to be practiced and the controversy against it should be reevaluated.

Trapped river otters (Lontra canadensis) from central Saskatchewan differ in total and organic mercury concentrations by sex and geographic location

Mercury (Hg) in wildlife remains of great concern, especially for apex piscivores. Despite this, exposure information from many species in many areas is lacking, so that management decisions are hampered. Here we examine Hg concentrations in fur, liver, and kidney tissues from river otters ( Lontra canadensis (Schreber, 1777)) ( n = 203) to quantify existing Hg concentrations over a broad geographic area in Saskatchewan. Mean fur total Hg (THg) (9.68 ± 7.52 mg/kg fresh weight (f.w.)) was significantly correlated with THg and organic Hg (OHg) in liver and kidney tissue, showcasing the potential for using fur as a noninvasive method of monitoring Hg in top-level mammals. Livers of males had higher mean OHg concentrations than livers of females (males: 2.71 mg/kg d.w., females: 1.87 mg/kg d.w.), but not significantly so. No sex-related differences were observed in kidney OHg concentrations. THg concentrations in otter fur collected in the Boreal Shield ecozone (Churchill River Upland) were significantly higher (mean = 16.1 mg/kg f.w.) than in otter fur collected from the Boreal Plain ecozone (mean = 8.59 mg/kg f.w.). Fur from otters ( n = 20; trapping block N66) trapped near a decommissioned smelter contained the highest concentrations of THg in the study (mean = 18.4 mg/kg f.w.).

Influence of dissolved organic matter (DOM) characteristics on dissolved mercury (Hg) species composition in sediment porewater of lakes from southwest China

The origin and composition of dissolved organic matter (DOM) in porewater of lake sediments is intricate and decisive for fate of pollutants including mercury (Hg). While there are many reports on the relationship between dissolved organic carbon concentration (DOC) and mercury (Hg) concentrations in aquatic systems, there are few in which DOM compositional properties, that may better explain the fate of Hg, have been the focus. In this study, porewaters from sediments of three lakes, Caihai Lake (CH), Hongfeng Lake (HF) and Wujiangdu Lake (WJD), all located in southwest China, were selected to test the hypothesis that DOM optical properties control the fate of Hg in aquatic ecosystems. Porewater DOM was extracted and characterized by UV–Vis absorption and fluorescence spectroscopy. A two end-member (autochthonous and allochthonous DOM) mixing model was used to unveil the origin of DOM in porewaters of the three lakes. Our results show a higher input of terrestrial DOM in the pristine lake CH, as compared to lakes HF and WJD lakes, which were both influenced by urban environments and enriched in autochthonous DOM. While the relationships between the concentrations of DOC and the different chemical forms of Hg forms were quite inconsistent, we found important links between specific DOM components and the fate of Hg in the three lakes. In particular, our results suggest that allochthonous, terrestrial DOM inhibits Hg(II) availability for Hg methylating micro-organisms. In contrast, autochthonous DOM seems to have been stimulated MeHg formation, likely by enhancing the activity of microbial communities. Indeed, DOM biodegradation experiments revealed that differences in the microbial activity could explain the variation in the concentration of MeHg. While relationships between concentrations of DOC and Hg vary among different sites and provide little information about Hg cycling, we conclude that the transport and transformation of Hg (e.g. the methylation process) are more strongly linked to DOM chemical composition and reactivity.