Mercury Accumulation Research Articles

Proteome changes in methylmercury-exposed mouse primary cerebellar granule neurons and astrocytes

Methylmercury (MeHg) is a neurotoxicant, with the cerebellum as the main target of toxicity; however, the toxic effects of MeHg on specific cell types remain unclear. Here, primary cerebellar granule neurons (CGNs) and cerebellar astrocytes were isolated and analyzed for total mercury accumulation, cellular reactive oxygen species (ROS) production, and whole-cell proteome expression after exposure to 0–10 μM MeHg for 24 h. Intracellular mercury and ROS levels showed dose-dependent increases. Mercury accumulation was greater in CGNs than astrocytes. The proteomic analysis identified a total of 1966 and 3214 proteins in CGNs and astrocytes, among which 183 and 262 proteins were differentially expressed after mercury exposure, respectively. Enrichment analysis revealed mitochondrial-associated organelles as the main targets of MeHg in both cell types. Whereas multiple functions/pathways were affected in CGNs, the oxidation–reduction process was the most significantly changed function/pathway in astrocytes. CGNs were more sensitive to MeHg-mediated neurotoxicity than astrocytes. The two cell types showed distinct mechanistic responses to MeHg. In astrocytes, the mitochondrion was the primary target of toxicity, resulting in increases in oxidation–reduction process responses. In CGNs, the neurotrophin signaling pathway, cytoskeleton, cAMP signaling pathway, and thyroid hormone signaling pathway were affected.

Oleanolic acid 3-glucoside, a synthetic oleanane-type saponin, alleviates methylmercury toxicity in vitro and in vivo

Methylmercury (MeHg) is one of the most toxic environmental pollutants, presenting a serious health hazard worldwide. In this study, we examined the potential of derivatives of oleanolic acid (OA), such as OA 3-glucoside, OA 28-glucoside, and OA 3,28-diglucoside, to mitigate MeHg toxicity in vitro and in vivo. We found that OA 3-glucoside suppressed the cellular MeHg uptake by 63.4% compared with that of the control and improved the cell viability from 75.4% to 107.9% upon exposure to cytotoxic MeHg in Caco-2 cells. To verify the anti-MeHg activity of OA 3-glucoside, mice were orally administered MeHg (0, 1.0, or 5.0 mg kg−1·d−1), with or without OA 3-glucoside, and then mercury accumulation was measured in various organs of the mice. The mice co-treated with MeHg and OA 3-glucoside showed significantly lower mercury content in organs such as the cerebrum, cerebellum, liver, kidney, and spleen, with 83.1%, 68.7%, 71.7%, 82.1%, and 18.2% of those in the OA 3-glucoside-untreated group, respectively. This suggested OA 3-glucoside had the potential as an anti-MeHg compound, owing to its ability to suppress the distribution of MeHg into organs. Supporting this hypothesis, the mice treated with MeHg and OA 3-glucoside showed a tendency to survive one day longer than the control mice. Our findings suggest OA 3-glucoside administration alleviates the toxicity of MeHg by suppressing MeHg accumulation in organs.

Mercury accumulation, speciation, and temporal trends in Atlantic Stingrays (Hypanus sabinus)

Mercury (Hg) deposited into aquatic sediments can be converted into the more toxic methylmercury (MeHg) by microbial activity. Atlantic stingrays (Hypanus sabinus) are an estuarine and nearshore species found in coastal regions of the western North Atlantic, occurring in multiple habitat types, and feeding mainly on benthic invertebrates. Mercury dynamics and speciation in stingrays have not been well examined. This study quantified total Hg and Hg species (Hg (II) and MeHg) in Atlantic stingrays sampled from Florida's Indian River Lagoon (IRL) from 2012 to 2013. Tissues (muscle and liver) collected from 29 stingrays were lyophilized and homogenized before being analyzed using a direct mercury analyzer. Concentrations of total Hg in muscle were positively related to stingray disk width, but concentrations in liver were not. Mean (±SD) total Hg in muscle (0.56 ± 0.30 mg/kg dw) was significantly higher than mean total Hg in liver (0.23 ± 0.19 mg/kg dw). Within liver tissue, percent MeHg (of total Hg) ranged from 31 to 99%. The ratio between total Hg in liver and total Hg in muscle was <1 for nearly all individuals, suggesting a lack of active hepatic demethylation and sequestration mechanisms. Concentrations of Hg in IRL Atlantic stingrays fall below concentrations known to result in direct toxicity to fishes; however, effects thresholds are not well understood for elasmobranchs. Comparisons of Hg concentrations in IRL Atlantic stingrays sampled previously (37 individuals in 1994) indicate that total Hg concentrations in muscle of Atlantic stingrays have decreased over the past two decades, suggesting a reduction in the bioavailable Hg in the IRL ecosystem.

The Effects of Mercury Chloride (Hgcl2) on the Changes in Hematology and Blood Sugar Level in Carps (Cyprinus carpio)

One of the increasingly heavy metals concentration is mercury (Hg). Exposure to mercury (Hg) can cause changes to blood hematology of fish caused by accumulation of mercury (Hg) that occurs in various types of organs, especially in the kidneys and liver which can suppress hematopoiesis tissue activity. The purpose of this study is to determine the hematological changes, including erythrocyte, leukocyte, Hb, Hematocrit and blood sugar levels in carps. The method used was an experimental method with Completely Randomized Design (RAL) with 4 treatments and 5 replications at the doses of 0 (control), 0.05, 0.10 and 0.15 ppm. The results show that there is a significant difference in each treatment and parameter. There is a decrease of erythrocytes by 1,678,000 cells/mm3 in treatment D (0.015 ppm), leukocyte increase by 16,360 cells/mm3 in treatment D (0.015 ppm), Hemoglobin decrease by 6.7g/dl in treatment D (0.015 ppm), hematocrit decrease by 10.24% in treatment D (0.015 ppm) and an increase in blood sugar by 99 mg/dl in treatment D (0.015 ppm).

A Comparative GIS tree‑pollution analysis between arsenic, chromium, mercury, and uranium contents in soils of urban and industrial regions in Qatar

This study compared the applicability of several geographic information systems (GIS) regression tree-based models (n = 136) to precisely define the most influencing environmental predictor parameters on arid soils. The study focused on the accumulation of arsenic, chromium, mercury, and uranium in the arid soils of Qatar using GIS tools. The rates of the built reference trees (based on environmental parameters) vary among chosen toxic metals as follows: Hg (80%), U (77%), As (72%), and Cr (70%); and this affects considerably the developed correlations (reflected as relative importance in %) between these toxic metals and the chosen environmental parameters. These parameters influence differently the investigated As/Cr/Hg/U, with higher quantitative impact (importance varying according to the metal into question) of anthropogenic parameters (distance to environmental hotspots 85–90%, land cover/use 78–82%, and proximity to roads 62–82%) than for the geopedological (soil type 30–76%, parent material 17–60%, and distance to geological structures 12–42%) and hydromorphological (elevation 7–53%, slope gradient 10–41%, distance to drainage line 15–30%, slope gradient 0–5%, and slope aspect 0–3%) parameters. The results can be used to prioritize the choice of remediation measures, and can be applied to other arid areas sharing analogous environmental/socio-economic conditions and pollution causes.

Holocene mercury accumulation calibrated by peat decomposition in a peat sequence from the Sanjiang Plain, northeast China

Peatlands are ideal archives that are widely used to reconstruct historical Hg accumulation around the world. However, decomposition of peat soils leads to Hg enrichment or depletion in peat profiles. To evaluate the impact of peat decomposition on historical Hg accumulation records, a 7800-year peat sequence from the Shenjiadian peatland (SJD-2, Sanjiang Plain, northeast China) was selected in this study. Based on the degree of peat humification and a generalized additive model (GAM), Hg accumulation rates (Hg ARs) were reconstructed and calibrated from the middle Holocene onward. The results showed that the Hg concentrations in the SJD-2 peat profile ranged from 11.9 to 55.3 ng g−1 and that the Hg AR ranged from 0.4 to 7.0 μg m−2 yr−1; these values for both parameters were lower than their corresponding values observed in other peatlands around the world. Peat decomposition led to Hg depletion in peat soils to some extent, and the GAM could be used to evaluate the impact of peat decomposition on historical Hg ARs in peat sequences based on the degree of peat humification and calibration of Hg ARs. Before the Industrial Revolution, anthropogenic Hg sources caused the calibrated Hg ARs in the SJD-2 peat profile to slightly increase around 1300 cal yr BP. Similar to other regions around the world, the calibrated Hg AR on the Sanjiang Plain also obviously increased from 3 to 8 μg m−2 yr−1 after global Hg emissions began to increase during the Industrial Revolution.

Potential mechanisms of cellular injury following exposure to a physiologically relevant species of inorganic mercury

Mercury is a toxic metal that is found ubiquitously in the environment. Humans are exposed to different forms of mercury via ingestion, inhalation, and/or dermal absorption. Following exposure, mercuric ions may gain access to target cells and subsequently lead to cellular intoxication. The mechanisms by which mercury accumulation leads to cellular injury and death are not understood fully. Therefore, purpose of this study was to identify the specific intracellular mechanisms that are altered by exposure to inorganic mercury (Hg2+). Normal rat kidney (NRK) cells were exposed to a physiologically relevant form of Hg2+, as a conjugate of cysteine (10 μM or 50 μM). Alterations in oxidative stress were estimated by measuring lipid peroxidation and mitochondrial oxidative stress. Alterations in actin and tubulin were measured using specific fluorescent dyes. Calcium levels were measured using Fluo-3 AM Calcium Indicator while autophagy was identified with Premo™ Autophagy Sensor LC3B-GFP. The current findings show that exposure to Hg2+ leads to enhanced oxidative stress, alterations in cytoskeletal structure, increases in intracellular calcium, and enhanced autophagy. We have established a more complete understanding of intoxication and cellular injury induced by a relevant form of Hg2+ in proximal tubule cells.

A Study on the Knowledge and Awareness among Dental Students of Mercury Toxicity and Amalgam Disposal

Dental amalgam consists of 50% mercury. An average amalgam filling consists of 1 gram of mercury which continously leaks mercury vapour due to the low vapour pressure of mercury. Mercury vapour can spread rapidly throughout the human body. It crosses cell membranes easily. Mercury can penetrate the blood brain barrier and result in mercury accumulation in the brain. Mercury is among the top three most toxic substances that affects people in large numbers. Amalgam is the largest source of mercury. As amalgam is the number one source of mercury production, dentists and dental students are at a very high risk of mercury poisoning due to repeated exposure to dental amalgam. This study intends to assess the knowledge and awareness levels among dental students of mercury toxicity and its potential risks, and the various disposal methods for amalgam. Though most of the students were aware of mercury toxicity and amalgam disposal methods as a whole, only a handful were aware about the absorption efficiency rate and the critical threshold of mercury, which was as low as 20.83% and 21.66% respectively. Almost 50% of the students interviewed had answered less than 8 out of 15 questions correctly. It is recommended that more effective methods for delivering information regarding mercury, its complications and management are deviced.

Effect of Tribulus terrestris in mercuric chloride-induced renal accumulation of mercury and nephrotoxicity in rat.

Mercury generates free radicals and subsequently increases oxidative stress, which leads to renal injury. Tribulus terrestris (TT) has good anti-inflammatory and antioxidant properties. Hydroalcoholic extract of different dose of TT was evaluated against mercuric chloride-induced nephrotoxicity. Rats (n = 6) were treated with TT at doses of 100, 200, and 300 mg/kg. Drugs were administered orally for 7 days. Single dose of mercuric chloride (5 mg/kg, intraperitoneal) on the 5th day caused significant elevation of blood urea nitrogen, serum creatinine, malondialdehyde, liver fatty acid binding protein, kidney injury molecule-1, and kidney mercury level and fall in glutathione, superoxide dismutase, glutathione peroxidase, and histopathological changes in disease control as compared to normal control group (P < 0.001). Dose of TT 200 and 300 mg/kg significantly (P < 0.001) prevented the renal injury, and mercury accumulation in kidney tissues significantly decreases in higher dose, i.e., 300 mg/kg as compared to control group. Our result indicates that the treatment of TT exerted significant protection against renal damage induced by mercuric chloride possibly due to its antioxidant and anti-inflammatory properties and by decreasing the renal accumulation of mercury.

Hg2+-binding peptide decreases mercury ion accumulation in fish through a cell surface display system

Mercury is a potentially toxic trace metal that poses threats to aquatic life and to humans. In this study, a mercury-binding peptide was displayed on the surface of Escherichia coli cells using an N-terminal region ice nucleation protein anchor. The surface-engineered E. coli facilitated selective adsorption of mercury ions (Hg2+) from a solution containing various metal ions. The Hg2+ adsorption capacity of the surface-engineered cell was four-fold higher than that of the original E. coli cells. Approximately 95% of Hg2+ was removed from solution by these whole-cell sorbents. The transformed strains were fed to Carassius auratus, so that the bacteria could colonize fish intestine. Engineered bacteria-fed C. auratus showed significantly less (51.1%) accumulation of total mercury when compared with the group that had not been fed engineered bacteria. The surface-engineered E. coli effectively protected fish against the toxicity of Hg2+ in aquatic environments by adsorbing more Hg2+. Furthermore, the surface-engineered E. coli mitigated microbial diversity changes in the intestine caused by Hg2+ exposure, thereby protecting the intestinal microbial community. This strategy is a novel approach for controlling Hg2+ contamination in fish.

Investigation of the differential transport mechanism of cinnabar and mercury containing compounds

BackgroundCinnabar has a long history of uses in Chinese traditional medicines as an ingredient in various remedies. However, the detailed mechanism of cinnabar in medication remains unclear, and the toxicity of cinnabar has been a debate due to its containing mercury sulfide. This study was designed to investigate the differential transport mechanism of cinnabar and other Hg-containing compounds HgCl2, MeHg and HgS, and to determine if organic anion transporters OAT1 and OAT3 were involved in the differential transport mechanism. Materials and methodsThe 293T cells were employed to investigate and compare the differential transport mechanism of cinnabar and HgCl2, MeHg and HgS. Cells were incubated with a low dose (5 μM HgCl2 and MeHg, 200 μM HgS and cinnabar), medium dose (10 μM HgCl2 and MeHg, 400 μM HgS and cinnabar), and high dose (20 μM HgCl2 and MeHg, 800 μM HgS and cinnabar) of HgCl2, MeHg, HgS and cinnabar for 24 h. Following treatment, the cells were collected and the cell viability was determined by MTT assay. The intracellular mercury content was measured at 1, 4, and 24 h after treatment with 10 μM of the tested agents by an atomic fluorescence spectrophotometer. The effect of these tested agents on mitochondrial respiration was determined in a high-resolution oxygraphyat 24 h following treatment. Furthermore, the effect of modulation of expression of transporters OAT1 and OAT3 on the transport and cytotoxicity of the tested agents was evaluated. The up and down regulation of OAT1 and OAT3 were achieved by overexpression and siRNA transfection, respectively. ResultsCompared with HgCl2 and MeHg, the cytotoxicity of cinnabar and HgS was lower, with cell viability at the high dose cinnabar and HgS being about 65%, while MeHg and HgCl2 were 40% and 20%, respectively. The intracellular mercury accumulation was time-dependent. At 24 h the intracellular concentrations of HgCl2 and MeHg were about 7 and 5 times higher, respectively, than that of cinnabar. No significant difference was found in the intracellular mercury content in cells treated with cinnabar compared to HgS. The knockdown and overexpression of the transporter OAT1 resulted in significant reduction and increase, respectively, in mercury accumulation in HgCl2 -treated cells in relative to control cells, while no significant changes were observed in cells treated with cinnabar, MeHg, and HgS. In addition, the knockdown and overexpression of the transporter OAT3 caused significant reduction and increase, respectively, in mercury accumulation in both HgCl2 and MeHg-treated cells in relative to control cells, while no significant changes were observed in cells treated with cinnabar and HgS. Furthermore, it was found that cells transfected with siOAT1 caused significant resistance to the cytotoxicity induced by HgCl2, while no noticeable changes in cell viability were observed in cells treated with other tested agents. Additionally, cells transfected with OAT3 did not change cell sensitivity to cytotoxicity induced by all of the four tested agents. ConclusionThis study demonstrates that differential transport and accumulation of mercury in 293T cells exists among cinnabar and the three mercury-containing compounds HgCl2, MeHg and HgS, leading to distinct sensitivity to mercury induced cytotoxicity. The kidney organic anion transporters OAT1 and OAT3 are partially involved in the regulation of the transport of HgCl2 and MeHg, but not in the regulation of the transport of cinnabar.

The distribution and accumulation of mercury and methylmercury in surface sediments beneath the East China Sea.

China is a massive mercury emitter, responsible for a quarter of the world's mercury emissions, which transit the atmosphere and accumulate throughout its watercourses. The Changjiang (Yangtze) River is the third largest river in the world, integrating mercury emissions over its 1.8 × 106km2 catchment and channelling them to the East China Sea where they can be buried. Despite its potential global significance, the importance of the East China Sea as a terminal mercury sink remains poorly known. To address this knowledge gap, total mercury and methylmercury concentrations were determined from 51 surface sediment samples revealing their spatial distribution, whilst demonstrating the overall pollution status of the East China Sea. Sedimentary mercury distributions beneath the East China Sea are spatially heterogeneous, with high mercury concentrations (> 25ngg-1) corresponding to areas of fine-grained sediment accumulation. In contrast, some sites of fine-grained sediment deposition have significantly lower values of methylmercury (< 15ngg-1), such as the Changjiang estuary and some isolated offshore areas. Fine-grained particles and organic matter availability appear to exert the dominant control over sedimentary mercury distribution in the East China Sea, whereas in situ methylation serves as an additional control governing methylmercury accumulation. Estimated annual sedimentary fluxes of mercury in the East China Sea are 51 × 106g, which accounts for 9% of China's annual mercury emissions.

Patterns of Mercury Accumulation in Tissues of Western Sandpipers (Calidris mauri ) Wintering on the Coast of Sinaloa, Mexico

Mercury concentration was quantified in liver, muscle, and primary feathers of pooled samples of Western Sandpiper (Calidris mauri) collected in December-January 2010 (wintering) and March-April 2011 (premigration) in Ensenada Pabellones and Bahia Santa Maria, Sinaloa, Mexico, to test for differences between sites, stages, tissues, and age-sex groups. During the winter, mercury concentrations were greater in individuals from Ensenada Pabellones than those from Bahia Santa Maria (0.81 ± 0.05 vs. 0.57 ± 0.05 mg/kg dry weight, respectively), and greater in liver than in muscle (0.89 ± 0.05 vs. 0.49 ± 0.05mg/kg dry weight, respectively). In the comparison between the stages, wintering birds had greater concentrations of mercury than those of premigration period (0.62 ± 0.05 vs. 0.48 ± 0.05 mg/kg dry weight, respectively). These mercury concentrations were lower than those found in other wintering sites in North America (mean = 4.4 mg/kg dry weight). Although these concentrations suggest that Western Sandpipers wintering on the coast of Sinaloa, Mexico, were being exposed to low mercury concentrations and had not accumulated mercury, it appears that mercury in their tissues decreased during the nonbreeding season. However, these conclusions are based on low numbers in some categories and require further work with individual, rather than pooled, samples.

Effect of body length, trophic position and habitat use on mercury concentrations of sharks from contrasted ecosystems in the southwestern Indian Ocean

The non-essential metal mercury (Hg) can have deleterious effects on health of organisms, and tends to bioaccumulate with age in long-lived organisms and to biomagnify along food webs. Because elasmobranchs are fished for human consumption and their Hg levels are frequently above the maximum Hg concentration recommended for fish consumption, understanding the drivers of Hg concentration is of considerable interest. Total Hg concentrations were analysed in muscle tissues of 14 shark and 2 batoid species (n = 339 individuals) sampled across multiple habitats (coastal, open ocean and bathyal) in the southwestern Indian Ocean. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) were analysed to assess whether relative trophic position and foraging habitats affected Hg concentrations. Hg concentrations increased with δ15N and body length, highlighting the mechanisms of bioaccumulation and biomagnification in relation with the trophic position and size of the individuals. Habitats where elasmobranchs were collected also affected their Hg concentrations. Bathyal sharks had high Hg concentrations that were almost similar to those of oceanic species, despite their lower relative trophic position. Higher bioavailability of Hg due to its enhanced methylation in deeper waters was considered as the most likely explanation for this result. These results highlight that multiple factors contribute to mercury accumulation in elasmobranchs.

Correction to: Patterns and controls of mercury accumulation in sediments from three thermokarst lakes on the Arctic Coastal Plain of Alaska

In the original publication, the incorrect GIS map projection was used to calculate lake surface areas and catchment areas that were presented

Dynamic mercury methylation and demethylation in oligotrophic marine water

Abstract. Mercury bioaccumulation in open-ocean food webs depends on the net rate of inorganic mercury conversion to monomethylmercury in the water column. We measured significant methylation rates across large gradients in oxygen utilization in the oligotrophic central Pacific Ocean. Overall, methylation rates over 24 h incubation periods were comparable to those previously published from Arctic and Mediterranean waters despite differences in productivity between these marine environments. In contrast to previous studies that have attributed Hg methylation to heterotrophic bacteria, we measured higher methylation rates in filtered water compared to unfiltered water. Furthermore, we observed enhanced demethylation of newly produced methylated mercury in incubations of unfiltered water relative to filtered water. The addition of station-specific bulk filtered particulate matter, a source of inorganic mercury substrate and other possibly influential compounds, did not stimulate sustained methylation, although transient enhancement of methylation occurred within 8 h of addition. The addition of dissolved inorganic cobalt also produced dramatic, if transient, increases in mercury methylation. Our results suggest important roles for noncellular or extracellular methylation mechanisms and demethylation in determining methylated mercury concentrations in marine oligotrophic waters. Methylation and demethylation occur dynamically in the open-ocean water column, even in regions with low accumulation of methylated mercury.

Dynamics and features of mercury accumulation in coniferous trees of Tomsk region

This article performs an analysis of mercury concentration in uneven-aged needles of various wood species in peat bog ecosystems of Tomsk region. New data are given on mercury accumulation and distribution depending on the type of conifers, needle age, and landscape and climate conditions. The level of the mercury concentration data obtained in Tomsk region does not exceed the mercury concentration levels in the literature. In general, it lies within the range of average concentrations for Siberia and the total area of Russia.

MEMORIES OF PROFESSOR ARISTEO RENZONI

Here were reported Memories of Professor Aristeo Renzoni, University of Siena. Among the first Professors of Ecology in Italy and internationally recognized scientist. In almost 60 years of research he published over 250 scientific papers. The main ecological and environmental topics of his research were the histology of reproductive structures of bivalves, the histology of the pineal gland in birds, the accumulation of mercury in large pelagic predators of Mediterranean Sea, the contamination of organochlorine compounds in bird eggs, the lead shot pollution from hunters activities in wetlands.

The Role of Climate: 71 ka of Atmospheric Mercury Deposition in the Southern Hemisphere Recorded by Rano Aroi Mire, Easter Island (Chile)

The study of mercury accumulation in peat cores provides an excellent opportunity to improve the knowledge on mercury cycling and depositional processes at remote locations far from pollution sources. We analyzed mercury concentrations in 150 peat samples from two cores from Rano Aroi (Easter Island, 27° S) and in selected vegetation samples of present-day flora of the island, in order to characterize the mercury cycling for the last ~71 ka BP. The mercury concentrations showed values ranging between 35 and 200 ng g−1, except for a large maxima (~1000 ng g−1) which occurred at the end of the Last Glacial Maximum (LGM, ~20 ka cal BP) in both peat cores. Low temperatures during the LGM would accelerate the atmospheric oxidation of Hg(0) to divalent mercury that, coupled with higher rainfall during this period, most likely resulted in a very efficient surface deposition of atmospheric mercury. Two exceptional short-lived Hg peaks occurred during the Holocene at 8.5 (350 ng g−1) and 4.7 (1000 ng g−1) ka cal BP. These values are higher than those recorded in most peat records belonging to the industrial period, highlighting that natural factors played a significant role in Hg accumulation—sometimes even more so than anthropogenic sources. Our results suggest that wet deposition, linked to atmospheric oxidation, was the main process controlling the short-lived Hg events, both in the mire and in the catchment soils.

Total mercury in surficial bottom sediments of Volga River’s reservoirs in Central Russia

The total mercury content of the surface layer (0–5 cm) of different types of bottom sediment in Gorky and Cheboksary reservoirs was determined. The content of mercury in bottom sediments varied within a wide range, 0.001–0.234 mg/kg. In spite of large industrial enterprises near the watersheds, which are potential sources of mercury in the environment, the content is comparable to background values. Depending on the sediment type, the metal concentration rises within a sequence: sand and loamy sand > sandy loams > clay and silt. The content of mercury positively correlates with the amount of organic matter in bottom sediments (r = 0.49–0.86, p ≤ 0.001) and the proportion of clay silt particles (r = 0.55–0.76, p ≤ 0.001). This relationship indicates the presence of two forms of mercury: sorbed on fine particle surfaces and as part of complex compounds. A negative correlation between Hg concentration and the flow velocity in the reservoir was revealed (r = − 0.40 to − 0.58, p ≤ 0.05). This relationship is due to the effect of pulsating discharge and wind currents on sedimentation conditions, and thus on the accumulation of mercury. The rate of accumulation was calculated as 15 kg/year in Gorky reservoir and 9 kg/year in Cheboksary, with average concentrations of 0.057 and 0.046 mg/kg, respectively, in the surface layer of bottom sediments.