Decrease In Hg Concentration Research Articles

Granite weathering profiles accumulate vegetation-derived mercury

Weathering of silicate rocks, particularly granitic rocks, generates the pedosphere that is of crucial importance in functioning terrestrial ecosystems. The pedosphere hosts large amounts of mercury (Hg). The source of Hg in granite weathering products is currently poorly constrained, however. Here we conducted Hg isotopic analyses on two weathering profiles developed on granitic plutons in Central and South China. Soils from both profiles show a downward decrease in Hg concentration but consistently negative ∆199Hg values. Mercury in precipitation, granites, and vegetation display positive, near-zero, and negative ∆199Hg values, respectively. The negative ∆199Hg values in the two weathering profiles are consistent with estimates of vegetation-derived Hg, supporting that Hg in weathering profiles are dominantly sourced from vegetation. Hg in vegetation is transported into surface soil firmly bonded to organic matter and migrates downwards weathering profiles. This study provides insights into the biogeochemical cycle of Hg in the granite-weathering crust and helps to explain the negative ∆199Hg values observed in terrestrial-derived sedimentary rocks.

The effect of phytoremediation on the reduction of mercury-contaminated water from gold processing using water kale (Ipomoea aquatica Forsk)

Gold ore processing is carried out by amalgamation techniques where mercury (Hg) is used as a medium to bind gold which results in water pollution around the processing area, so it is necessary to remediate water. One way in managing mercury-contaminated water is phytoremediation of the use of water kale (ipomoea aquatica forsk) and to help the phytoremediation process, ingredients are needed that can help the growth of water kale in increasing the absorption of Hg concentrations, namely the addition of liquid NPK fertilizer. This study aims to analyze water kale without liquid NPK fertilizer, and use liquid NPK fertilizer against water kale in reducing the concentration of Hg, pH and TSS metals in water. This study used an experimental method with an experimental box (container) consisting of 4 treatments, then an Analysis of Variance (ANOVA) test of 5% and Duncan Multiple Rang Test were carried out. The results showed that liquid NPK fertilizer had an influence on reducing the concentration of Hg, pH and TSS in water. Based on the results of experiments using liquid NPK fertilizer, the best treatment results were obtained in mercury absorption by water kale and reducing Hg concentration in water, namely treatment D (contaminated water + water kale + liquid NPK fertilizer) on the 14th day, as evidenced by a decrease in Hg concentration in water by 0.56 mg / l to 0.00486 mg / l, pH 10.1 to 6.86 and TSS 1695 mg / l to 1 mg / l and an increase in nitrate levels, Phosphate and potassium in water can accelerate absorption by water kale.

Total body burden of neurotoxicant Hg in Chinese mitten crab (Eriocheir sinensis) - Considerations of distribution and human risk assessment

The Chinese mitten crab (Eriocheir sinensis) is considered one of the 100 most invasive alien species in the world. Despite this, its role in ecosystems, among others, in the trophodynamics of pollutants including mercury, is still not fully understood. Becoming an increasingly important and widespread element of the trophic chain in new areas arouses interest from humans as consumers. Hence it is important to determine the level of contaminants (including Hg) in alien species. In the present study, great attention was paid separately to the soft tissues and hard tissues of the exoskeleton, which may play an important role in the detoxification of the crab's body from toxic Hg. The study was conducted on crabs collected in 2011–2021 in the Vistula Lagoon. Concentrations of total mercury and its forms were carried out using a Direct Mercury Analyzer, DMA-80 (Milestone, Italy). The present study showed that mercury accumulation of the crab's body largely occurred through the gills, followed by the oral route. The distribution of Hg in the crab's organs was related to the trophic origin of the mercury, while halide-bound mercury and semilabile forms from the respiration (filtration) process were redistributed into the crab's exoskeleton. Male crabs, compared to females, had a higher Hg burden on internal organs such as their hepatopancreas and gonads. Hg concentration in hard tissues was closely related to the type of mineralization of the carapace. The elimination of Hg from the muscles and from the hepatopancreas into the carapace was one of the important detoxification processes of the crab's body. Thus, moulting crabs effectively remove Hg protecting its body from the neurotoxin. As a result, a smaller Hg load is biomagnified, making the crab's muscle tissue fit for human consumption. The observed decrease in Hg concentrations from 2011 to 2021, as well as the spatial variability of Hg in the crab's muscles, testify that the crab can serve as a biomonitor for ecosystem changes.

Mercury deposition to lake sediments near historic gold mines in northern Canada

Mercury (Hg) contamination in aquatic systems can lead to adverse human and environmental health outcomes. Yellowknife, a city in Canada’s Northwest Territories, is a historic mining community, with two large gold mines (Giant Mine and Con Mine) that used Hg amalgamation methods to extract gold between ∼1938 and 1960. We analyzed dated sediment cores from 20 small lakes to investigate the spatial and temporal Hg deposition patterns within 50 km of Giant Mine. Breakpoint analysis of the within-lake z-score normalized anthropogenic Hg flux indicates two significant time periods of changing emission rates. The first is a significant increase in Hg deposition rate (∼1925) during the time of gold exploration in the region and onset of Hg amalgamation (1938) and the second is a significant decrease in deposition rate that begins around the time of the cessation of Hg amalgamation at Giant Mine (∼1959). Sediment Hg concentrations exceeded the Canadian Council for Ministers of the Environment Interim Sediment Quality Guideline (ISQG) for Hg (0.17 mg/kg dw) in 55% of the lakes (n = 11) during mining (1948–1999). All lakes within 5 km of the Giant Mine roaster stack exceeded CCME ISQG during mining (n = 8), with a 4-fold increase in total Hg concentration observed during mining at these near-field (<5 km from stack) sites. We observed evidence of enriched Hg in near-field, mid-field, and far-field sites. The elevated sedimentary Hg concentrations during mining in near-field sites would have posed a hazard to human and wildlife health during the height of emissions, however the significant decrease in Hg concentrations since the closure of mines in the region demonstrate the potential for recovery in these aquatic ecosystems.

Divergent Temporal Trends of Mercury in Arctic Char from Paired Lakes Influenced by Climate-Related Drivers.

Climate-driven changes including rising air temperatures, enhanced permafrost degradation, and altered precipitation patterns can have profound effects on contaminants, such as mercury (Hg), in High Arctic lakes. Two physically similar lakes, East Lake and West Lake at the Cape Bounty Arctic Watershed Observatory on Melville Island, Nunavut, Canada are being affected by climate change differently. Both lakes have experienced permafrost degradation in their catchments; however, West Lake has also undergone multiple underwater Mass Movement Events (MMEs; beginning in fall 2008), leading to a sustained 50-fold increase in turbidity. This provided the unique opportunity to understand the potential impacts of permafrost degradation and other climate-related effects on Hg concentrations and body condition of landlocked Arctic char (Salvelinus alpinus), an important sentinel species across the Circum-Arctic. Our objectives were to assess temporal trends in char Hg concentrations and to determine potential mechanisms driving the trends. There was a significant decrease in Hg concentrations in East Lake char, averaging 6.5%/year and 3.8%/year for length-adjusted and age-adjusted means, respectively, from 2008 to 2019. Conversely, in West Lake there was a significant increase, averaging 7.9%/year and 8.0%/year for length-adjusted and age-adjusted mean Hg concentrations, respectively, for 2009 to 2017 (the last year with sufficient sample size). The best predictors of length-adjusted Hg concentrations in West Lake were carbon and nitrogen stable isotope ratios, indicating a shift in diet including possible dietary starvation brought on by the profound increase in lake turbidity. Our study provides an example of how increasing lake turbidity, a likely consequence of climate warming in Arctic lakes, may influence fish condition and Hg concentrations. Environ Toxicol Chem 2023;42:2712-2725. © 2023 His Majesty the King in Right of Canada and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Volcanism intensity and associated climate-ocean-land dynamics during the Cryogenian interglaciation: Insights from mercury isotopes

The Cryogenian interglaciation (ca. 660 Ma to 650 Ma) was an interlude between the Sturtian glaciation (ca. 717 Ma to 660 Ma) and Marinoan glaciation (ca. 650 Ma to 635 Ma). Recent observations of anomalously high mercury (Hg) concentrations in Cryogenian interglacial sediments at basinal settings in the Nanhua Rift Basin, South China, imply that large volcanism can be a possible driving force of the Cryogenian interglaciation. To test this hypothesis and understand the potential linkage between large volcanism and climate-ocean-land dynamics during the Cryogenian interglaciation, we investigate mercury (Hg) concentrations and isotopic composition of Cryogenian interglacial sediments at shallow water (shelf/slope) settings in the Nanhua Rift Basin, South China. The basal Mn-bearing black shales show an increased pattern in Hg concentrations (318 to 4400 ppb) and Hg/TOC ratios (243 to 1730 ppb/wt%), and overall positive Δ199Hg values (0.00 to 0.10‰), suggesting increasing volcanic Hg input into the ocean via atmospheric Hg(II) deposition in the early Cryogenian interglaciation. The upper siltstone samples show a dramatic decrease in Hg concentrations (from 5110 to 459 ppb) and a drop of Δ199Hg values (from 0.04 to −0.05‰), suggesting weakened volcanism during the middle-late Cryogenian interglaciation. Combined with the analyses of major and trace elements proxies, we demonstrate that (1) greenhouse climate in the early Cryogenian interglaciation induced high oceanic productivity, high organic burial on the seafloor and high terrestrial sulfate input into the ocean, which favors the deposition of Mn-bearing black shales in the ocean; and (2) weakened volcanism and continued continental weathering exhausted atmospheric CO2 and drove the global climate to the Marinoan glaciation. This study, therefore, provides important insights into the climate-ocean-land dynamics during the Cryogenian interglaciation.

Mercury loss and isotope fractionation during high-pressure and high-temperature processing of sediments: Implication for the behaviors of mercury during metamorphism

Metamorphic rocks show much lower mercury (Hg) levels than sedimentary rocks, which may be due to the loss of Hg during high-pressure and high-temperature conditions during metamorphism. To test this hypothesis, we conduct high-pressure and high-temperature experiments on ancient and modern sediments (WH black shale and GSS-4 soil). Under 0.3 GPa, the Hg concentrations decrease while the δ202Hg values increase with rising temperatures (WH black shale: 333–89 ppb, −1.34 to −0.79‰, 250–700 °C; GSS-4: 545–265 ppb, −1.39 to −1.01‰, 400–700 °C), suggesting the loss of isotopically light Hg isotopes under high-temperature conditions. Under constant temperatures of both 200 °C and 500 °C, with increasing pressure (0.5–1.4 GPa), GSS-4 shows only a slight decrease in Hg concentration with no variation in δ202Hg, suggesting that high-pressure conditions restrain the loss of isotopically lighter isotopes. Consistent Δ199Hg and Δ200Hg values were observed in both samples during our experiment, implying no Hg isotope mass-independent fractionation (Hg-MIF) under high-temperature and high-pressure conditions. While results of this imply that metamorphism may lead to the emission of isotopically lighter Hg from sedimentary rocks to the surface environment, the lack of Hg-MIF during metamorphism provides important support for the use of Hg isotopes for paleoenvironment reconstruction.

The Importance of Dead Seagrass (Posidonia oceanica) Matte as a Biogeochemical Sink

We assessed the potential of dead seagrass Posidonia oceanica matte to act as a biogeochemical sink and provide a coherent archive of environmental change in a degraded area of the Mediterranean Sea (Augusta Bay, Italy). Change in sediment properties (dry bulk density, grain size), concentration of elements (Corg, Cinorg, N, Hg) and stable isotope ratios (δ13C, δ 15N) with sediment depth were measured in dead P. oceanica matte and unvegetated (bare) sediments in the polluted area, and an adjacent P. oceanica meadow. Principal Component Analysis (PCA) revealed a clear clustering by habitat, which explained 72% of variability in our samples and was driven mainly by the accumulation of N and Hg in finer sediments of the dead matte. Assessment of the temporal trends of Corg, N and Hg concentrations in the dead matte revealed changes in the accumulation of these elements over the last 120 years, with an increase following the onset of industrial activities 65 y BP (i.e., yr. 1950) that was sustained even after seagrass loss around 35 y BP. Despite a decrease in Hg concentrations in the early 1980s following the onset of pollution abatement, overall Hg levels were 2-fold higher in the local post-industrial period, with a Hg enrichment factor of 3.5 in the dead matte. Mean stocks of Corg, N and Hg in 25 cm thick sediment deposits (4.08 ± 2.10 kg Corg m-2, 0.14 ± 0.04 kg N m-2, 0.19 ± 0.04 g Hg m-2) and accumulation in the last 120 yr (35.3 ± 19.6 g Corg m-2 y-1, 1.2 ± 0.4 g N m-2 y-1, 0.0017 ± 0.0004 g Hg m-2 y-1) were higher in the dead matte than bare sediment or adjacent P. oceanica meadow. Our results indicate that dead P. oceanica matte maintained its potential as a biogeochemical sink and, like its living counterpart, dead matte can serve as an effective archive to allow for reconstructing environmental change in coastal areas of the Mediterranean where severe perturbations have led to P. oceanica loss. Appropriate management for contaminated areas should be prioritized to prevent release of pollutants and carbon from dead mattes.

A U-Turn for Mercury Concentrations over 20 Years: How Do Environmental Conditions Affect Exposure in Arctic Seabirds?

Mercury (Hg) is highly toxic in its methylated form (MeHg), and global change is likely to modify its bioavailability in the environment. However, it is unclear how top predators will be impacted. We studied blood Hg concentrations of chick-rearing black-legged kittiwakes Rissa tridactyla (2000-2019) in Svalbard (Norway). From 2000 to 2019, Hg concentrations followed a U-shaped trend. The trophic level, inferred from nitrogen stable isotopes, and chlorophyll a (Chl a) concentrations better predicted Hg concentrations, with positive and U-shaped associations, respectively. As strong indicators of primary productivity, Chl a concentrations can influence production of upper trophic levels and, thus, fish community assemblage. In the early 2000s, the high Hg concentrations were likely related to a higher proportion of Arctic prey in kittiwake's diet. The gradual input of Atlantic prey in kittiwake diet could have resulted in a decrease in Hg concentrations until 2013. Then, a new shift in the prey community, added to the shrinking sea ice-associated release of MeHg in the ocean, could explain the increasing trend of Hg observed since 2014. The present monitoring provides critical insights about the exposure of a toxic contaminant in Arctic wildlife, and the reported increase since 2014 raises concern for Arctic seabirds.

Mercury Concentrations in Double-Crested Cormorant Chicks Across Canada.

Mercury (Hg) biomagnifies in aquatic food chains and can reach high concentrations in fish-eating birds. Spatial patterns of Hg have been found in freshwater ecosystems across Canada for many taxa, including fish and birds. However, it often is challenging to sample a representative population size of adult birds to monitor concentrations of contaminants over a large spatial scale. Moreover, adult birds can migrate and can show a contaminant profile that may not be representative of local resources. The goals of this study were (1) to determine if there was a spatial pattern of Hg concentrations in piscivorous birds, (2) to develop a model to estimate Hg concentrations in breeding adults using chicks as proxy, and (3) to develop predictive equations among non-lethal tissues that are representative of local resources in adults (blood and growing feathers). Double-crested Cormorant (Phalacrocorax auritus) chick growing feathers were sampled at 19 sites across Canada. Adult tissues (freshly grown feathers and blood) were sampled at five of those locations to establish correlations between age classes and between adult tissues. We found an increase in Hg concentrations with latitude up to 50°N followed by a decrease. There was a decrease in Hg concentrations from west to east, which contradicts previous studies. We found a good correlation of Hg concentrations between adults and chicks and among adult tissues. Our study shows that chicks are representative of adults and can be a suitable proxy for monitoring local mercury concentrations across Canada.

Temporal trend of mercury in polar bears (Ursus maritimus) from Svalbard using teeth as a biomonitoring tissue

We examined the use of mercury (Hg) and nitrogen and carbon stable isotopes in teeth of polar bear (Ursus maritimus) from Svalbard as biotracers of temporal changes in Hg pollution exposure between 1964 and 2003. Teeth were regarded as a good matrix of the Hg exposure, and in total 87 teeth of polar bears were analysed. Dental Hg levels ranged from 0.6 to 72.3 ng g(-1) dry weight and increased with age during the first 10 years of life. A decreasing time trend in Hg concentrations was observed over the recent four decades while no temporal changes were found in the stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C). This suggests that the decrease of Hg concentrations over time was more likely due to a lower environmental Hg exposure in this region rather than a shift in the feeding habits of Svalbard polar bears.

Acute intraperitoneal mercury chloride contamination and distribution in liver, muscle and gill of a neotropical fish Hoplias malabaricus (BLOCK, 1794)

The present study investigated with the distribution of mercury chloride in muscle, liver and gills of Hoplias malabaricus contaminated through intraperitoneal injection (6 µg in 0.1mL of PBS) for a period of 24, 48, 72 and 96h. The liver, gill and muscle were analyzed for mercury content in an ICP/AES (Varian Liberty II) with vapor generating accessory (VGA 77). The muscle and liver tissues presented the same contamination pattern increasing concentrations in 24 h of exposure with a decrease in Hg concentration with 72 h and a new increase in Hg concentrations with 96 h of exposure. The Hg concentrations in contaminated organisms were always higher than the control although only for liver samples the difference was statistically significant. Liver samples always presented higher Hg contents when compared with gill and muscle samples.

Mercury isotopic composition of hydrothermal systems in the Yellowstone Plateau volcanic field and Guaymas Basin sea-floor rift

To characterize mercury (Hg) isotopes and isotopic fractionation in hydrothermal systems we analyzed fluid and precipitate samples from hot springs in the Yellowstone Plateau volcanic field and vent chimney samples from the Guaymas Basin sea-floor rift. These samples provide an initial indication of the variability in Hg isotopic composition among marine and continental hydrothermal systems that are controlled predominantly by mantle-derived magmas. Fluid samples from Ojo Caliente hot spring in Yellowstone range in δ 202Hg from − 1.02‰ to 0.58‰ (± 0.11‰, 2SD) and solid precipitate samples from Guaymas Basin range in δ 202Hg from − 0.37‰ to − 0.01‰ (± 0.14‰, 2SD). Fluid samples from Ojo Caliente display mass-dependent fractionation (MDF) of Hg from the vent (δ 202Hg = 0.10‰ ± 0.11‰, 2SD) to the end of the outflow channel (δ 202Hg = 0.58‰ ± 0.11‰, 2SD) in conjunction with a decrease in Hg concentration from 46.6 pg/g to 20.0 pg/g. Although a small amount of Hg is lost from the fluids due to co-precipitation with siliceous sinter, we infer that the majority of the observed MDF and Hg loss from waters in Ojo Caliente is due to volatilization of Hg 0 (aq) to Hg 0 (g) and the preferential loss of Hg with a lower δ 202Hg value to the atmosphere. A small amount of mass-independent fractionation (MIF) was observed in all samples from Ojo Caliente (Δ 199Hg = 0.13‰ ±1 0.06‰, 2SD) but no significant MIF was measured in the sea-floor rift samples from Guaymas Basin. This study demonstrates that several different hydrothermal processes fractionate Hg isotopes and that Hg isotopes may be used to better understand these processes.

Estimation of the Long-range Transport of Mercury, Cadmium, and Lead to Northern Finland on the Basis of Moss Surveys

Nation-wide surveys of the accumulation of 10 heavy metals in mosses were carried out in Finland in 1985, 1990, 1995, and 2000. Separate investigations were carried out, on the basis of these surveys, into the atmospheric deposition of Hg, Cd, and Pb beyond the Arctic Circle in northern Finland. These metals are readily distributed in the form of long-range transboundary pollution, and particular concern has been raised about the transport and accumulation of these metals into Arctic areas. The Hg, Cd, and Pb concentrations in mosses in northern Finland were low. There was a clear decrease in Cd and Pb concentrations during the period 1985–2000. The Pb concentration decreased, on the average, from 8 to 2 μg g−1, and the Cd concentration from 0.3 to 0.1 μg g−1. Hg concentrations, which were analyzed in 1995 and 2000, decreased only slightly from 0.037 to 0.031 μg g−1. The slight decrease in Hg concentrations in northern Finland appears to reflect the decreasing Hg emissions and the high mobility of this metal. Factors leading to the decrease in Pb and Cd concentrations in mosses in northern Finland include a decrease in local emissions and a decrease in transboundary air pollution. The past two decades have been characterized by decreases in heavy metal emissions of throughout Europe. The greatest reductions have been in Pb emissions, due to the introduction of unleaded fuels.

Comparison of total mercury levels in relation to diet and molt for nine species of marine birds

Total mercury (Hg) concentrations were analyzed for tissues of nine species of marine birds from the Quoddy region, New Brunswick, Canada, including cormorants (Phalacrocorax auritus), eiders (Somateria mollissima), guillemots (Cepphus grylle), phalaropes (Phalaropus lobatus), gulls (Larus argentatus, L. Philadelphia), terns (Sterna hirundo, S. paradisaea) and kittiwakes (Rissa tridactyla). There was a progressive decrease in Hg concentration from the innermost to the outermost primary feather in Bonaparte's gulls, herring gulls, black-legged kittiwakes and Arctic terns. Primaries of common terns and black guillemots showed no significant trend. Cormorants, guillemots and eiders, which feed on benthic organisms, and common terns, which feed predominantly on fish, had the highest tissue Hg levels, whereas birds such as kittiwakes and phalaropes, which consume mainly pelagic invertebrates, had the lowest Hg levels.