Lower Hg Concentrations Research Articles

First observation of mercury species on an important water vapor channel in the southeastern Tibetan Plateau

Abstract. The Tibetan Plateau is generally considered to be a significantly clean area owing to its high altitude; however, the transport of atmospheric pollutants from the Indian subcontinent to the Tibetan Plateau has influenced the Tibetan environments. Nyingchi is located at the end of an important water vapor channel. In this study, continuous monitoring of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (PBM) was conducted in Nyingchi from 30 March to 3 September 2019, to study the influence of the Indian summer monsoon (ISM) on the origin, transport, and behavior of Hg. The GEM and PBM during the preceding Indian summer monsoon (PISM) period (1.20±0.35 ng m−3 and 11.4±4.8 pg m−3 for GEM and PBM, respectively) were significantly higher than those during the ISM period (0.95±0.21 ng m−3, and 8.8±6.0 pg m−3); the GOM during the PISM period (13.5±7.3 pg m−3) was almost at the same level as that during the ISM period (12.7±14.3 pg m−3). The average GEM concentration in the Nyingchi region, obtained using passive sampler, was 1.12±0.28 ng m−3 (from 4 April 2019 to 31 March 2020). The GEM concentration showed that the sampling area was very clean compared to other high-altitude sites. The GEM has several patterns of diurnal variation during different periods. Stable high GEM concentrations occur at night and low concentrations occur in the afternoon during PISM, which may be related to the nocturnal boundary layer structure. High values occurring in the late afternoon during the ISM may be related to long-range transport. Low concentrations of GEM observed during the morning in the ISM may originate from vegetation effects. The results of the trajectory model demonstrate that the sources of pollutants at Nyingchi are different with different circulation patterns. During westerly circulation in the PISM period, pollutants mainly originate from central India, northeastern India, and central Tibet. During the ISM period, the pollutants mainly originate from the southern part of the SET site. The strong precipitation and vegetation effects on Hg species during the ISM resulted in low Hg concentrations transmitted to Nyingchi during this period. Further, principal component analysis showed that long-distance transport, local emissions, meteorological factors, and snowmelt factors are the main factors affecting the local Hg concentration in Nyingchi. Long-distance transport factor dominates during PISM and ISM3, while local emissions is the major contributor between PISM and ISM3. Our results reveal the Hg species distribution and possible sources of the most important water vapor channel in the Tibetan Plateau and could serve as a basis for further transboundary transport flux calculations.

Impact assessment of Hg–Sb wastes to urban soils and shallow groundwater in the mining region of Huitzuco, Guerrero (southern Mexico) using mineralogical, geochemical and Sr–Pb isotopic tools

Concentrations of Hg, Sb and the related potentially toxic elements (RPTEs) As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn were determined in tailings from the Hg–Sb mining region of Huitzuco, Guerrero (southern Mexico) to evaluate their impact on urban soils and shallow groundwater. Tailings are entirely composed of fragments from the ore-hosting Morelos Formation and contain residues of cinnabar, terlinguaite, livingstonite, stibnite and Fe–Ti oxides, whereas urban soils are derived from rocks of the Tilzapotla Formation with a minor contribution from the Morelos Formation. Tailings typically contain lower concentrations of Hg, Sb and RPTEs than urban soils strongly suggesting more than one source of elements. Shallow groundwater is of Ca–HCO3 and Ca–SO4 types with most samples having concentrations of Hg and Sb above the Mexican and EPA guidelines and concentrations of all RPTEs below these guidelines. At Huitzuco, tailings are the most important source of Hg and Sb and a significant source of Mn, Fe, Cr and Ni, whereas As, Pb, Cd, Cu, Zn, V and Co derive from neighboring lithologies. Neighboring rocks are also significant contributors of Sb, Mn, Fe and Ni. Besides lithology and mineralization, the Pb isotopes indicate the participation of a still unidentified, low radiogenic source in urban soils and groundwater with an isotopic signature similar to house paints. Unlike other nearby mining zones, at Huitzuco, only Hg and Sb represent a serious menace to ecosystems and inhabitants, Cu a moderate risk around tailings, and Pb, Zn and Cd a low risk.

Extraction and Quantification of Nanoparticulate Mercury in Natural Soils.

Nanoparticulate mercury (Hg-NPs) are ubiquitous in nature. However, the lack of data on their concentration in soils impedes reliable risk assessments. This is due to the analytical difficulties resulting from low ambient Hg concentrations and background interferences of heterogeneous soil components. Here, coupled to single particle inductively coupled plasma-mass spectrometry (spICP-MS), a standardized protocol was developed for extraction and quantification of Hg-NPs in natural soils with a wide range of properties. High particle number-, particle mass-, and total mass-based recoveries were obtained for spiked HgS-NPs (74-120%). Indigenous Hg-NPs across soils were within 107-1011 NPs g-1, corresponding to 3-40% of total Hg on a mass basis. Metacinnabar was the primary Hg species in extracted samples from the Wanshan mercury mining site, as characterized by X-ray absorption spectroscopy and transmission electron microscopy. In agreement with the spICP-MS analysis, electron microscopy revealed comparable size distribution for nanoparticles larger than 27 nm. These indigenous Hg-NPs contributed to 5-65% of the measured methylmercury in soils. This work paves the way for experimental determinations of indigenous Hg-NPs in natural soils, which is critical to understand the biogeochemical cycling of mercury and thereby the methylation processes governing the public exposure to methylmercury.

Mercury concentrations and stable isotope ratios (δ13C and δ15N) in pelagic nekton assemblages of the south-western Indian Ocean

Mercury (Hg) concentrations and stable isotope values (δ13C and δ15N) were investigated in micronekton collected from La Pérouse and MAD-Ridge seamounts, Reunion Island and the southern Mozambique Channel. Organisms occupying epipelagic habitats showed lower Hg concentrations relative to deeper dwelling benthopelagic ones. Increasing Hg concentrations with increasing body size were recorded in the Mozambique Channel and Reunion Island. Positive relationships were observed between Hg levels and δ15N values in pelagic nekton assemblages collected at MAD-Ridge seamount and the southern Mozambique Channel, suggesting biomagnification of Hg. Concentrations of Hg in organisms across the south-western Indian Ocean were within the same range of values. Total Hg concentrations depend on a range of factors linked to habitat range, body size and trophic position of the individuals. To our knowledge, this is the first study investigating the patterns of Hg concentrations in pelagic nekton assemblages from the south-western Indian Ocean.

Coprecipitation of Mercury from Natural Iodine-Containing Seawater for Accurate Isotope Measurement.

Oceans play a key role in the global mercury (Hg) cycle, but studies on Hg isotopes in seawater are rare due to the extremely low Hg concentration and the lack of a good preconcentration method. Here, we introduce a new coprecipitation method for separating and preconcentrating Hg from seawater for accurate isotope measurement. The coprecipitation was achieved by sequential addition of 0.5 mL of 0.5 M CuSO4, 1 mL of 0.5 M Na2S, and 1 mL of 0.5 M CuSO4 reagents, which allowed for quantitatively precipitating Hg from up to 10 L of seawater. The protocol was validated by testing synthetic solutions with varying Hg and iodide (I-) concentrations and by comparing the reaction times of various reagents added. The method resulted in a quantitative recovery of 98 ± 12% (n = 32, two standard deviations, 2 SD) and a relatively low procedure blank (103 pg of Hg, n = 8). The precipitates were filtrated and analyzed for Hg isotopes. Repeated measurements of synthetic seawaters spiked with certificated standard materials (NIST 3133 and 3177) using the entire method gave identical Hg isotope ratios with near-quantitative Hg recovery, indicating no isotope fractionation during preconcentration. A total of six nearshore seawater samples from the Yellow Sea and the Bohai Sea (China) were analyzed using the coprecipitation method. The data showed a large fractionation of Hg isotopes and revealed the possible impact of both atmospheric and anthropogenic inputs to the coastal seawater Hg budget, implying the potential application of this method in studying marine Hg systematics and global Hg cycling.

Exposure to cumulative stressors affects the laying phenology and incubation behaviour of an Arctic-breeding marine bird

Wildlife are exposed to multiple stressors across life-history stages, the effects of which can be amplified as human activity surges globally. In Arctic regions, increasing air and ocean temperatures, more severe weather systems, and exposure to environmental contaminants all represent stressors occurring simultaneously. While Arctic vertebrates, including marine birds, are expected to be at risk of adverse effects from these individual stressors, few studies have researched their combined impacts on breeding behaviour and reproductive success. The interactive effects of environmental conditions and mercury (Hg) contamination on laying phenology and incubation behaviour were examined in female common eiders (Somateria mollissima, mitiq, ᒥᑎᖅ ᐊᒪᐅᓕᒡᔪᐊᖅ) nesting at Canada’s largest Arctic breeding colony. Conditions with higher pre-breeding air temperatures were linked to females with higher egg Hg concentrations laying earlier than those with lower Hg values. Furthermore, examination of a total of 190 days of incubation behaviour from 61 eiders across two years revealed a negative relationship between wind speed and the frequency of incubation interruptions. Importantly, exposure to higher air temperatures combined with lower Hg concentrations was significantly correlated with increased incubation interruptions. Although previous research has shown that warmer spring temperatures could afford lower quality females more time to improve body condition to successfully lay, results suggest these females may face stronger cumulative fitness costs during incubation in warmer years, potentially in combination with the effects of Hg on physiological stress and hormone secretion. This study highlights how multiple stressors exposure, driven by human-induced environmental changes, can have a complex influence on reproduction.

Ecosystem change and carbon cycle perturbation preceded the end-Triassic mass extinction

During the Phanerozoic, major global upheavals in life history and the carbon cycle are predominantly linked to the emplacement of large igneous provinces, but the delineation of a cause and effect framework remains unclear. The end-Triassic mass extinction (ETE) is temporally associated with emplacement of the Central Atlantic magmatic province (CAMP). A better understanding of precursor events to the ETE is essential if the mechanisms for this mass extinction are to be fully delineated. Here, we present new high-resolution data integrating petrographic, biotic, mercury, and carbon isotope analyses of the pre-extinction interval at the Ferguson Hill locality, Nevada (USA). We document the “precursor” carbon isotope excursion along with low Hg concentrations and sulphidic sediments prior to the ETE. A combination of proxies reveals disruptions to shallow marine ecosystems and biogeochemical cycles prior to the main phase of CAMP volcanism. We propose that episodic anoxic conditions led to the restructuring of shallow marine benthic ecosystems towards overall lower diversity, including more low oxygen tolerant taxa preceding the ETE. The timing of the initial marine ecosystem restructuring in eastern Panthalassa could be related to the early phase of CAMP emplacement, and implies that an early intrusive event initiated the ecosystem changes. These restructured marine ecosystems reflect the deteriorating environmental conditions leading up to the ETE that ultimately resulted in the ETE.

Mercury bioaccumulation by higher plants and mushrooms around chlor-alkali and metallurgical industries in the Baikal region, Southern Siberia, Russia

ABSTRACT This investigation identified specific features of mercury bioaccumulation by higher plants and mushrooms growing around chlor-alkali and metallurgical plants. All samples analysed by the atomic absorption method. Various plant organs differently accumulate mercury that is regulated by their biochemical and physiological functions. Examination of different plant parts points out that the leaves and bark of trees and the leaves of herbs are the main Hg accumulators, which is explained both by the absorption of soil mercury and Hg input from the atmospheric air. The plants from the АМР surroundings show lower Hg concentrations (average 0.008 mg kg−1) when compared with those from the САР surroundings (average 0.040 mg kg−1). Mushrooms exhibit the highest bioaccumulation of Hg amount in the studied samples. The average Hg concentrations in mushrooms in CAP and AMP amount to 0.78 and 0.19 mg kg−1, accordingly. These concentrations are higher than Hg concentrations in soils, in which these mushrooms were growing. The ability of plants and mushrooms to take up mercury is directly related to its bioavailable forms in soils. The Hg–organic complexes play a crucial role the Hg bioaccumulation that is evidenced by a significant positive correlation in the ‘organic Hg fraction–plants’ system.

Mercury accumulation response of rice plant (Oryza sativa L.) to elevated atmospheric mercury and carbon dioxide

New observations and updated models now suggest terrestrial ecosystems are net sink of atmospheric mercury (Hg), and the critical constrained process to identify the strengths of terrestrial sink is whether the large amount of Hg stored in vegetation originates from the soil as well as from the atmosphere. In this study, field open top chambers (OTCs) experiments reveal that rice plant can assimilate gaseous elemental mercury (GEM, Hg0) from the atmosphere through stomata, and Hg concentrations in rice leaves, upper and bottom stalks and grains increased with Hg0 levels in air, showing significantly quadratic linear relationships. Coupling field stable isotope soil amendment experiments, atmospheric source of Hg in rice plant is quantified with more than 90% of Hg accumulation in rice aboveground biomass from air and approximately 80% of rice root Hg from soil. Furthermore, elevated atmospheric carbon dioxide (CO2) exposure led to lower Hg concentration in rice tissues through reduction stomatal conductance of rice leaf, and subsequently impact the capacity of Hg storage in rice aboveground parts from the atmosphere. The findings from experiments provide a foundation for future quantification of atmospheric sink of crops in local and larger scales and comprehensive evaluation atmosphere - terrestrial processes and exposure risks in the global Hg cycling.

Mercury Anomaly in Oligocene–Miocene Maykop Group Sediments (Caucasus Continental Collision Zone): Mercury Hosts, Distribution, and Sources

The Oligocene–Miocene Maykop Group sediments, mainly composed of illite–smectite, store mercury in strongly variable concentrations from 10 to 920 μg/kg. Extremely high Hg levels (98–920 μg/kg) coupled with abnormal mercury-to-total organic carbon (TOC) ratios (Hg/TOC = 109 to 3000 μg/kg/wt%; TOC = 0.2 wt% to 1.2 wt%) were measured in the Middle Maykop marine shales that were deposited in the deepwater Indol–Kuban Basin under anoxic conditions. The Middle Maykop shales contain up to 70% of total mercury in sulfide form. In heavy mineral fractions, abundant Hg-bearing pyrite (with up to 4810 µg/kg Hg in hand-picked concentrates) is accompanied by sporadic cinnabar. Relative to the Middle Maykop sediments, the Upper Maykop shales have much lower Hg concentrations and Hg/TOC ratios: 10 to 63 μg/kg (34 μg/kg on average) and 7.7 to 137 μg/kg/wt% (39 μg/kg/wt% on average), respectively. Mercury sequestration is inferred to occur mostly by binding in sulfide hosts in the Middle Maykop anoxic deep-sea sediments and in organic matter, Fe3+-(oxy)hydroxides, and clay particles in the Upper Maykop shales which were deposited in a more oxygenated environment. Mercury inputs to the marine shales during Maykopian sedimentation were possibly associated with local Oligocene–Lower Miocene volcanic activity in the Caucasus Continental Collision Zone. At the same time, the mode of Hg binding in sediments was controlled by redox conditions which changed from anoxic to disoxic and suboxic at the Middle-to-Upper Maykop transition.

Heavy Metals in the Muscle and Hepatopancreas of Red Swamp Crayfish (Procambarus clarkii) in Campania (Italy).

Simple SummaryHeavy metals can represent a serious threat to marine and freshwater fauna through exposure, bioaccumulation and biomagnification processes. The aim of this study was to evaluate the presence of non-essential and essential elements in freshwater crayfish (Procambarus clarkii) edible tissues to establish the healthiness of this product and to evaluate the pollution status of the sampling sites from Campania region (Italy). The results suggest that crayfish were safe for human consumption and indicated mild contamination of heavy metals of the sampling areas. The aim of this study was to carry out a quali-quantitative analysis of the presence of non-essential and essential trace elements in freshwater crayfish (Procambarus clarkii) edible tissues to establish the healthiness of this product and to evaluate the pollution status of the sampling sites included in the present study. P. clarkii is one of the most common species of freshwater crustaceans in Italy, regularly consumed by local people. Moreover, the crayfish, due to its trophic position and diet, can be considered as an excellent bioindicator of the health status of the ecosystem. We collected sixty crayfish samples from two different sites in Campania (Italy): Villa Literno and Sessa Aurunca. Concentrations of trace elements were determined by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Our data showed low concentrations of Cd, Hg and Pb, with values below the European Commission MRL (Commission Regulation (EC) 1881/2006). We suggest that data obtained from this study showed that crayfish collected from Villa Literno and Sessa Aurunca were safe for human consumption. Furthermore, the results of this research indicated mild contamination of heavy metals of the sampling sites, indicating a good health status of the area’s aquatic ecosystem.

Mercury in the hydrothermal fluids and gases in Paleochori Bay, Milos, Greece

Seafloor hydrothermal activity may constitute a considerable mercury (Hg) source to the oceans, but the flux from marine shallow-water hydrothermal systems (MSWHS) remains poorly constrained to date. To study the presence of Hg in MSWHS in Paleochori Bay (Milos Island, Greece), sea surface, bottom, pore fluid and hydrothermal gas samples were collected in June of 2017, October of 2018 and July of 2020, and analyzed for Cl, Br, SO4, As, Ca, Fe, K, Mg, Mn, Na, Si, Sr, H2S, unfiltered total Hg (THg), and filtered Hg (Hgdiss). Specific sites were selected for the analysis of volatile elemental Hg (Hgo), dimethylmercury (DMHg), monomethylmercury (MMHg), and Hg in the gas phase (Hggas). Concentrations of THg observed in samples collected from the sea surface were elevated compared to surface samples taken outside Paleochori Bay. The highest surface water concentrations (~10 to 15 pM) were measured in samples collected directly above shallow-water hydrothermal discharge areas. Pore fluids outside Paleochori Bay were significantly lower in THg (0.8 to 8.6 pM) than those taken inside (17.4 to 1511 pM). Porewaters collected from areas with visible gaseous or fluid emission were highly variable but generally elevated in THg concentrations (185 to 5066 pM). Concentrations within gases ranged from 0.7 to 2791 nmol/m3. The vast majority of samples with highly elevated THg (> 100 pM) had low Na/K ratios (< 15), indicative of rapidly rising fluid. Concentrations of Hg0, DMHg, and MMHg were below detection limits in all samples.Bottom substrate type (e.g., rocky vs. sediment covered) likely affected infiltration rates of oxygenated seawater below the sediment-water interface, thereby affecting Hg speciation and removal by precipitation. Flux rates from porewaters compared to those with gaseous emission were high (12.56 to 1088 mol THg/year and 0.37 to 1.85 mol THg/year). Sites with slow gaseous emission rates are hypothesized to have extended subsurface reaction times, resulting in lower Hg concentrations emitted to bottom waters. However, increasing rates of gas emission did not necessarily indicate higher Hg concentrations. The scavenging of Hg in the sediments and advective flux out of Paleochori Bay likely prevent significant accumulations of THg in the water column of Paleochori Bay. The total atmospheric flux from Paleochori Bay using average flux calculations over the entire surface area would contribute 6 mmol Hg/year to the atmosphere.We hypothesize that Hg concentrations within the pore fluids of Paleochori Bay reflect a balance between mixing and precipitation in the subsurface. A three-component mixing system of vapor, brine and seawater determines THg concentrations; however, precipitation due to sulfur cycling, changes in redox conditions and temperature, all play a crucial role in removing Hg from emitted fluids and gases.

Different Design Strategies for Metal Sulfide Sorbents to Capture Low Concentrations of Gaseous Hg0 in Coal-Fired Flue Gas and High Concentrations of Gaseous Hg0 in Smelting Flue Gas.

Capturing gaseous Hg0 using regenerable metal sulfides is a promising technology to recover gaseous Hg0 from both coal-fired flue gas (CFG) and smelting flue gas (SFG) for the centralized control. Gaseous Hg0 concentration in SFG is 2-3 orders of magnitude higher than that in CFG; therefore, the design strategy of metal sulfides for capturing gaseous Hg0 from CFG is quite different from that from SGF. In this work, the structure-activity relationship of metal sulfides to capture Hg0 was investigated according to the remarkable difference in MoO3 loading on sulfureted FeTiOx to capture low/high concentrations of gaseous Hg0. The rate of Hg0 adsorption onto metal sulfides was mainly related to the amounts of adsorption sites and S22- on the surface, the affinity of adsorption sites to gaseous Hg0, and the gaseous Hg0 concentration. Meanwhile, the capacity for Hg0 adsorption was approximately equal to the less of the amount of adsorption sites and S22- on the surface. Furthermore, capturing low concentrations of gaseous Hg0 from CFG required the metal sulfide sorbents having more adsorption sites with strong affinity to gaseous Hg0, while capturing high concentrations of gaseous Hg0 from SFG required the sorbents with enough adsorption sites.

Short-Term Legacy Effects of Mercury Contamination on Plant Growth and nifH-Harboring Microbial Community in Rice Paddy Soil.

Methylmercury (MeHg), which is formed in rice paddy soil, exhibits strong neurotoxicity through bioaccumulation in the food chain. A few groups of microorganisms drive both mercury methylation and nitrogen fixation in the rhizosphere. Little is known about how the shifted soil microbial community by Hg contamination affects nitrogen fixation rate and plant growth in paddy soil. Here, we examined how stimulated short-term Hg amendment affects the nitrogen fixing microbial community and influences plant-microbe interactions. Soil was treated with low (0.2 mg/kg) and high (1.1 mg/kg) concentrations of Hg for 4 weeks; then, rice (Oryza sativa) was planted and grown for 12 weeks. The nitrogen-fixation rate and rice growth were measured. The diversity and structure of the microbial community were analyzed by sequencing the nifH gene before and after rice cultivation. Hg treatments significantly decreased the nitrogen fixation rate and dry weight of the rice plants. The structure of the nifH-harboring community was remarkably changed after rice cultivation depending on Hg treatments. Iron- or sulfate-reducing bacteria, including Desulfobacca, Desulfoporosimus, and Geobacter, were observed as legacy response groups; their abundances increased in the soil after Hg treatment. The high abundance of those groups were maintained in control, but the abundance drastically decreased after rice cultivation in the soil treated with Hg, indicating that symbiotic behavior of rice plants changes according to the legacy effects on Hg contamination. These results suggested that Hg contamination can persist in soil microbial communities, affecting their nitrogen-fixation ability and symbiosis with rice plants in paddy soil.

Patterns and Determinants of Essential and Toxic Elements in Chinese Women at Mid-Pregnancy, Late Pregnancy, and Lactation.

Maternal status of essential and toxic elements affects the health of the mother, developing fetus, or breastfeeding infant. However, few studies have examined the patterns of these elements and their determinants in pregnant or lactating women. Plasma samples of 1211 healthy mid-pregnant, late pregnant, and lactating women enrolled in coastland, lakeland, and inland areas of China from May–July 2014, were analyzed for concentrations of 15 elements, using inductively coupled plasma mass spectrometry. The adjusted median concentrations of elements varied by physiologic stage and region. Lactating versus pregnant women showed higher concentrations of Zn, Cr, Mo, Ni, Sb, Cd and Pb, but lower concentrations of Cu, I, Al and Hg. In pregnant women, the concentrations of Fe, Zn, I, Mo, Ni, Al, Hg and Cd were higher in mid- versus late-pregnancy. Overall, the highest concentrations were observed in Zn, I, Mn, Al, and Pb in coastland, in Hg in lakeland, and in Fe in inland area. Element concentrations varied by maternal age, pre-pregnancy BMI, education, parity, delivery mode, feeding practice, and intakes of aquatic products and mutton. In conclusion, essential and toxic elements coexisted in pregnant and lactating women, and their concentrations varied by physiologic stages, regions, maternal socio-demographic characteristics and dietary factors.

Spatial and temporal trends in mercury levels in the down of black stork chicks in central Europe.

Piscivorous avian species may be affected by mercury (Hg) which tends to accumulate in aquatic environments and biomagnifies across the food webs. One of such species is the black stork, whose population increase recently slowed down due to unknown reasons. At the same time Hg contamination and its effects were almost unaudited for this species, so it may have exerted deleterious effects on the population and an evaluation is necessary. This is the first study of this species concerning Hg contamination. Thus, Hg concentrations were investigated in the down of black stork chicks (N=90) from breeding locations in central and southern Poland (Europe) between 2015 and 2017. As well as Hg levels, morphometric parameters and age were evaluated. Mean Hg concentrations reached 0.7μg/g d.w. and differed significantly between years, from the lowest value noted in 2017 (mean 0.5μg/g), through 2016 (0.7μg/g), to the highest one in 2015 (0.9μg/g), and between nest locations where higher Hg levels were generally found in northern parts of the study area. Hg concentrations were also unrelated to morphometric parameters. Contrarily, morphometric parameters revealed high correlations between themselves, which was confirmed by the cluster analysis (revealing only two clusters) and principal component analysis (the first PC explained 96.8% of the variance). Hg levels in the down of black storks were rather low with the fluctuation between years and nest locations probably caused by parental exposure during wintering, migration, pre-breeding season and recent exposure through food provided by parents. Such low Hg concentrations seemed not to affect the population from the region studied.

Evaluation of engineered sorbents for the sorption of mercury from contaminated bank soils: a column study

As a global environmental pollutant, mercury (Hg) threatens our water resources and presents a substantial risk to human health. The rate and extent of immobilization of Hg2+ (hereafter, Hg) on engineered sorbents (Thiol-SAMMS®, pine biochar, SediMite™, Organoclay™ PM-199, and quartz sand as a control) was evaluated using flow-through column experiments. The effectiveness of the sorbents was based on (1) the percentage of Hg removed in relation to the total amount of Hg passing the sorbent column, and (2) the rate of Hg uptake compared to the nonreactive tracer bromide (Br−). All sorbents removed Hg to a certain extent, but none of the sorbents removed all the Hg introduced to the columns. Thiol-SAMMS showed the highest mean percentage of Hg removed (87% ± 2.9%), followed by Organoclay PM-199 (71% ± 0.4%), pine biochar (57% ± 22.3%), SediMite (61% ± 0.8%), and the control quartz sand (11% ± 5.6%). Thiol-SAMMS was the only sorbent to exhibit retardation of Hg in comparison to the conservative tracer Br−. For the remaining sorbents, Br− along with low concentrations of Hg were eluted within the first 3 pore volumes, indicating limited retardation of Hg. Overall, removal of Hg by sorbents was substantial, suggesting that sorbents might be suitable for deployment in contaminated environments. High concentrations of DOM leaching from the soil columns likely influenced the speciation of Hg and inhibited sorption to the sorbents. Incomplete removal of Hg by any sorbent suggests that additional optimization is needed to increase efficiency.

Preferential Liver Accumulation of Mercury Explains Low Concentrations in Muscle of Caiman yacare (Alligatoridae) in Upper Amazon.

Caiman yacare is considered one of the top predators in the Amazon basin, and understanding pollutant distribution within its tissues may help its sustainable management. As a top predator, C. yacare should have the highest mercury concentrations, but has lower Hg concentrations than carnivorous fish (Rivera et al. 2016), which are part of their diet. We compared total Hg among liver, kidney, fat, and muscle of C. yacare, and whether trends in the distribution of Hg among tissues were like other crocodilians, aquatic birds, omnivorous, and carnivorous fish. Fat had the lowest concentrations (0.025 ± 0.03 mg kg-1) followed by muscle (0.15 ± 0.06 mg kg-1), kidney (0.57 ± 0.30 mg kg-1) and liver (1.81 ± 0.80 mg kg-1). Such preferential accumulation makes C. yacare meat a safer alternative for human consumption than carnivorous fish. The relation between Hg accumulation in liver and muscle is highest in crocodilians, which has evolutive and environmental implications.

Atmospheric mercury sources in a coastal-urban environment: a case study in Boston, Massachusetts, USA.

Mercury (Hg) is an environmental toxicant dangerous to human health and the environment. Its anthropogenic emissions are regulated by global, regional, and local policies. Here, we investigate Hg sources in the coastal city of Boston, the third largest metropolitan area in the Northeastern United States. With a median of 1.37 ng m-3, atmospheric Hg concentrations measured from August 2017 to April 2019 were at the low end of the range reported in the Northern Hemisphere and in the range reported at North American rural sites. Despite relatively low ambient Hg concentrations, we estimate anthropogenic emissions to be 3-7 times higher than in current emission inventories using a measurement-model framework, suggesting an underestimation of small point and/or nonpoint emissions. We also test the hypothesis that a legacy Hg source from the ocean contributes to atmospheric Hg concentrations in the study area; legacy emissions (recycling of previously deposited Hg) account for ∼60% of Hg emitted annually worldwide (and much of this recycling takes place through the oceans). We find that elevated concentrations observed during easterly oceanic winds can be fully explained by low wind speeds and recirculating air allowing for accumulation of land-based emissions. This study suggests that the influence of nonpoint land-based emissions may be comparable in size to point sources in some regions and highlights the benefits of further top-down studies in other areas.

Why productive lakes are larger mercury sedimentary sinks than oligotrophic brown water lakes

AbstractMercury accumulation in lake sediments is a widespread environmental problem due to the biomagnification of Hg in the aquatic food chain. Soil Hg concentrations, catchment vegetation, erosion, and lake productivity are major factors controlling the accumulation of Hg in lakes. However, their influence on the Hg mass balance in lakes with different catchment characteristics and trophic state is poorly understood. In this multilake study, we decipher the effects of catchment vegetation (coniferous vs. deciduous forest), soil Hg content, and trophic state on Hg sedimentation at six lakes in Germany. We investigated Hg concentrations in leaves, soils, and the lake's water phase. Soils under coniferous stands show slightly higher Hg concentrations than under deciduous forest. Hg concentrations in the water phase were higher in the oligotrophic brown water lakes (8.1 ± 5.6 ng L−1 vs. 3.0 ± 1.9 ng L−1). Lower Hg concentrations in sediment trap material indicate dilution by algae organic matter in the mesotrophic lakes (0.12–0.17 μg g−1 vs. 0.57–0.89 μg g−1). However, Hg accumulation rates in sediment traps were up to 14‐fold higher in the mesotrophic lakes (113–443 μg m−2 yr−1) than in the brown water lakes (32–144 μg m−2 yr−1), which could not be explained by higher Hg fluxes to the productive lakes. Hg mass balance calculation reveals that water phase Hg scavenging by algae is the major reason for the intense Hg export to the sediments of productive lakes which makes them significantly larger sedimentary sinks than oligotrophic brown water lakes.