Tracing mercury pathways in Augusta Bay (southern Italy) by total concentration and isotope determination

Bivalves as a Mercury Bioindicator: A National Isotopic Survey along the Coast of South Korea

Mercury (Hg) is a contaminant that poses health risks for human populations relying on seafood consumption. To mitigate its impact, identifying and monitoring Hg sources have become priorities, notably under the Minamata Convention. Bivalves are commonly used as sentinels in contaminant biomonitoring but can accumulate Hg from diverse environmental media. To investigate their Hg sources, bivalves (blue mussel, Mytilus edulis, and Pacific oyster, Crassostrea gigas) and their associated sediment were sampled along the coast of South Korea and analyzed for Hg concentration and isotopic values. Oysters displayed low Δ199Hg (0.19 ± 0.19‰) and δ202Hg (-0.35 ± 0.55‰), highlighting a sedimentary source, whereas mussels exhibited higher values (0.72 ± 0.87 and 0.09 ± 0.72‰, respectively) indicating bioaccumulation from the water column. Sulfur, carbon, and nitrogen stable isotopes suggested that such a difference was not due to feeding niches. However, Hg isotopic trajectory analysis showed that environmental conditions controlling the desorption and remobilization of sediment Hg, notably via tidal flows, were likely to drive the observed source(s). While sediment Hg is not systematically reflected in biota, bivalves, which typically display Hg pools accumulated by benthic or pelagic food webs, appear valuable for Minamata Convention biomonitoring, though their fluctuating Hg sources require careful interpretation.

Hair mercury isotopes, a noninvasive biomarker for dietary methylmercury exposure and biological uptake

Background. Fish and rice are the main dietary sources of methylmercury (MeHg); however, rice does not contain the same beneficial nutrients as fish, and these differences can impact the observed health effects of MeHg. Hence, it is important to validate a biomarker, which can distinguish among dietary MeHg sources. Methods. Mercury (Hg) stable isotopes were analyzed in hair samples from peripartum mothers in China (n = 265). Associations between mass dependent fractionation (MDF) (δ202Hg) and mass independent fractionation (MIF) (Δ199Hg) (dependent variables) and dietary MeHg intake (independent variable) were investigated using multivariable regression models. Results. In adjusted models, hair Δ199Hg was positively correlated with serum omega-3 fatty acids (a biomarker for fish consumption) and negatively correlated with maternal rice MeHg intake, indicating MIF recorded in hair can be used to distinguish MeHg intake predominantly from fish versus rice. Conversely, in adjusted models, hair δ202Hg was not correlated with measures of dietary measures of MeHg intake. Instead, hair δ202Hg was strongly, negatively correlated with hair Hg, which explained 27-29% of the variability in hair δ202Hg. Conclusions. Our results indicated that hair Δ199Hg can be used to distinguish MeHg intake from fish versus rice. Results also suggested that lighter isotopes were preferentially accumulated in hair, potentially reflecting Hg binding to thiols (i.e., cysteine); however, more research is needed to elucidate this hypothesis. Broader impacts include 1) validation of a non-invasive biomarker to distinguish MeHg intake from rice versus fish, and 2) the potential to use Hg isotopes to investigate Hg binding in tissues.

Mercury isotope evidence for the importance of recycled fluids in collisional ore systems

The sources of fluids and metals in porphyry systems of continental-collision settings are poorly constrained. Mercury isotopes display unique mass-independent fractionation (expressed as Δ199Hg) and may provide important constraints on metal and volatile sources given that Hg is a highly volatile metal. Here, we report Hg isotope data on ore-forming porphyries, barren magmatic rocks, and mantle-derived mafic magmas from southern Tibet. The fertile porphyries and coeval mafic magmas display mainly positive Δ199Hg values (up to +0.25 per mil), while Δ199Hg values in barren magmatic rocks and mafic magmas are largely negative (-0.54 to 0.00 per mil). The positive Δ199Hg values observed here are consistent with seawater and marine sediments, suggesting that the ultimate source of fluids involved in the genesis of post-subduction porphyry copper deposits was the mantle lithosphere metasomatized by previous oceanic plate subduction. Our Hg isotope data provide an alternative view to current metallogenetic models on collisional porphyry systems that focus on melting of the lower continental crust.

Mercury stable isotopes in seabirds in the Ebro Delta (NE Iberian Peninsula): Inter-specific and temporal differences

Mercury (Hg) is a global pollutant, which particularly affects aquatic ecosystems, both marine and freshwater. Top-predators depending on these environments, such as seabirds, are regarded as suitable bioindicators of Hg pollution. In the Ebro Delta (NE Iberian Peninsula), legacy Hg pollution from a chlor-alkali industry operating in Flix and located ca. 100 km upstream of the Ebro River mouth has been impacting the delta environment and the neighboring coastal area. Furthermore, levels of Hg in the biota of the Mediterranean Sea are known to be high compared to other marine areas. In this work we used a Hg stable isotopes approach in feathers to understand the processes leading to different Hg concentrations in three Laridae species breeding in sympatry in the area (Audouin's gull Ichthyaetus audouinii, black-headed gull Chroicocephalus ridibundus, common tern Sterna hirundo). These species have distinct trophic ecologies, exhibiting a differential use of marine resources and freshwater resources (i.e., rice paddies prey). Moreover, for Audouin's gull, in which in the Ebro Delta colony temporal differences in Hg levels were documented previously, we used Hg stable isotopes to understand the impact of anthropogenic activities on Hg levels in the colony over time. Hg stable isotopes differentiated the three Laridae species according to their trophic ecologies. Furthermore, for Audouin's gull we observed temporal variations in Hg isotopic signatures possibly owing to anthropogenic-derived pollution in the Ebro Delta. To the best of our knowledge this is the first time Hg stable isotopes have been reported in seabirds from the NW Mediterranean.

Regional assessment of the historical trends of mercury in sediment cores from Wider Caribbean coastal environments

Spatial and temporal variations of mercury (Hg) concentrations, enrichment, and potential ecological risks were studied in a suite of lead-210 (210Pb) dated sediment cores from 13 Wider Caribbean Region coastal environments. Broad variability of Hg concentrations (19-18761 ng g-1) was observed, encompassing even background levels (38-100 ng g-1). Most Hg concentration profiles exhibited a characteristic upward trend, reaching their peak values in the past two decades. Most of the sediment sections, showing from moderately to very severe Hg enrichment, were found in cores from Havana Bay and Sagua River Estuary (Cuba), Port-au-Prince Bay (Haiti), and Cartagena Bay (Colombia). These were also the most seriously contaminated sites, which can be considered regional Hg 'hotspots'. Both Havana Bay and Port-au-Prince Bay reportedly receive waste from large cities with populations exceeding 2 million inhabitants, and watersheds affected by high erosion rates. The records from the Sagua River Estuary and Cartagena Bay reflected historical Hg contamination associated with chloralkali plants, and these sites are of very high ecological risk. These results constitute a major contribution to the scarce regional data on contaminants in the Wider Caribbean Region and provide reference information to support the evaluation of the effectiveness of the Minamata Convention.

Tracking the multiple Hg sources in sediments in a typical river-lake basin by isotope compositions and mixing models

In this study, total mercury (THg) contents and Hg isotope compositions in sediments were investigated in the Lianxi River, Zijiang River and South Dongting Lake to identify and quantify multiple Hg sources and evaluate the Hg environmental processes. The THg contents, δ202Hg and Δ199Hg values in sediments were 48.22 ∼ 4284.32 µg/kg, - 1.33 ∼ 0.04‰ and - 0.25 ∼ 0.03‰, respectively. Relatively distinct Hg isotope characteristics of sediments were presented in the Lianxi River, Zijiang River and South Dongting Lake, indicating the dominant Hg sources considerably varied in these regions. Source apportionment based on MixSIAR proved that Hg in sediments mainly originated from industrial activities, and the ternary mixing model concluded non-ferrous metal smelting was the dominant industrial Hg contributor in the Lianxi River. Compared with the Lianxi River, the relative contribution of Hg in sediments from industrial activities significantly decreased, while the relative contributions of Hg from background releases significantly increased in the Zijiang River and South Dongting Lake. Nonetheless, the contribution of industrial Hg in this study area deserves more attention. These results are conducive to further manage Hg pollution.

Mercury isotope compositions in seawater and marine fish revealed the sources and processes of mercury in the food web within differing marine compartments

Anthropogenic activities and climate change have significantly increased mercury (Hg) levels in seawater. However, the processes and sources of Hg in differing marine compartments (e.g. estuary, marine continental shelf (MCS) or pelagic area) have not been well studied, which makes it difficult to understand Hg cycling in marine ecosystems. To address this issue, the total Hg (THg) concentration, methylmercury (MeHg) concentration and stable Hg isotopes were determined in seawater and fish samples collected from differing marine compartments of the South China Sea (SCS). The results showed that the estuarine seawater exhibited substantially higher THg and MeHg concentrations than those in the MCS and pelagic seawater. Significantly negative δ²⁰²Hg (-1.63‰ ± 0.42‰) in estuarine seawater compared with that in pelagic seawater (-0.58‰ ± 0.08‰) may suggest watershed input and domestic sewage discharge of Hg in the estuarine compartment. The Δ¹⁹⁹Hg value in estuarine fish (0.39‰ ± 0.35‰) was obviously lower than that in MCS (1.10‰ ± 0.54‰) and pelagic fish (1.15‰ ± 0.46‰), which showed that relatively little MeHg photodegradation occurred in the estuarine compartment. The Hg isotope binary mixing model based on Δ²⁰⁰Hg revealed that approximately 74% MeHg in pelagic fish is derived from atmospheric Hg(II) deposition, and over 60% MeHg in MCS fish is derived from sediments. MeHg sources for estuarine fish may be highly complex (e.g. sediment or riverine/atmospheric input) and further investigations are warranted to clarify the contribution of each source. Our study showed that Hg stable isotopes in seawater and marine fish can be used to identify the processes and sources of Hg in different marine compartments. This finding is of great relevance to the development of marine Hg food web models and the management of Hg in fish.

Mercury stable isotopes in the ocean: Analytical methods, cycling, and application as tracers

Mercury (Hg) has seven stable isotopes that can be utilized to trace the sources of Hg and evaluate the importance of transport and transformation processes in the cycling of Hg in the environment. The ocean is an integral part of the Earth and plays an important role in the global mercury cycle. However, there is a lack of a systematic review of Hg stable isotopes in marine environments. This review is divided into four sections: a) advances in Hg stable isotope analysis, b) the isotope ratios of Hg in various marine environmental matrices (seawater, sediment, and organisms), c) processes governing stable Hg isotope ratios in the ocean, and d) application of Hg stable isotopes to understand biotic uptake and migration. Mercury isotopes have provided much useful information on marine Hg cycling that cannot be given by Hg concentrations alone. This includes (i) sources of Hg in coastal or estuarine environments, (ii) transformation pathways and mechanisms of different forms of Hg in marine environments, (iii) trophic levels and feeding guilds of marine fish, and (iv) migration/habitat changes of marine fish. With the improvement of methods for seawater Hg isotope analysis (especially species-specific methods) and the measurement of Hg isotope fractionation during natural biogeochemical processes in the ocean, Hg stable isotopes will advance our understanding of the marine Hg cycle in the future, e.g., mercury exchange at the sea-atmosphere interface and seawater-sediment interface, contributions of different water masses to Hg in the ocean, fractionation mechanisms of Hg and MeHg transformation in seawater.

Morphological and functional alterations in hemocytes of Mytilus galloprovincialis exposed in high-impact anthropogenic sites

The work aimed to study the induction of morphological alterations in M. galloprovincialis in the field and its suitability to be integrated into a sensitive, simple, and cost-effective cell-based multimarker approach for the detection of the stress status induced by pollution in coastal marine environments in view of ecotoxicological biomonitoring and assessment application. Cellular morphometric alterations was paralleled by the analysis of standardized biomarkers such as lysosomal membrane destabilization, and genotoxocity biomarkers such as micronuclei and binuclated cells frequencies were investigated. The study was carried out by means of a transplanting experiment in the field, using caged organisms from an initial population exposed in the field in two multi-impacted coastal sites of the central Mediterranean area, Bagnoli in the eastern Tyrrhenian Sea and Augusta-Melilli-Priolo in the western Ionian Sea. Capo Miseno (NA) for the Tyrrhenian area and Brucoli (ME) for the Ionian area were chosen as control sites. Hemocyte enlargement and filopodial elongation increased frequencies were observed in organisms exposed to the impacted sites. These morphometric alterations showed strong agreement with the lysosomal membrane destabilization and biomarkers of genotoxicity, suggesting their usefulness in detecting the pollutant-induced stress syndrome related to genotoxic damage.

Trace mercury migration and human exposure in typical mercury-emission areas by compound-specific stable isotope analysis

Anthropogenic mercury (Hg) emissions have increased significantly since the Industrial Revolution, resulting in severe health impacts to humans. The consumptions of fish and rice were primary human methylmercury (MeHg) exposure pathways in Asia. However, the lifecycle from anthropogenic Hg emissions to human MeHg exposure is not fully understood. In this study, a recently developed approach, termed MeHg Compound-Specific Isotope Analysis (CSIA), was employed to track lifecycle of Hg in four typical Hg-emission areas. Distinct Δ¹⁹⁹Hg of MeHg and inorganic Hg (IHg) were observed among rice, fish and hair. The Δ¹⁹⁹Hg of MeHg averaged at 0.07 ± 0.15 ‰, 0.80 ± 0.55 ‰ and 0.43 ± 0.29 ‰ in rice, fish and hair, respectively, while those of IHg averaged at - 0.08 ± 0.24 ‰, 0.85 ± 0.43 ‰ and - 0.28 ± 0.68 ‰. In paddy ecosystem, Δ¹⁹⁹Hg of MeHg in rice showed slightly positive shifts (∼0.2 ‰) from those of IHg, and comparable Δ¹⁹⁹Hg of IHg between rice grain and raw/processed materials (coal, Hg ore, gold ore and sphalerite) were observed. Simultaneously, it was proved that IHg in fish muscle was partially derived from in vivo demethylation of MeHg. By a binary model, we estimated the relative contributions of rice consumption to human MeHg exposure to be 84 ± 14 %, 58 ± 26 %, 52 ± 20 % and 34 ± 15 % on average in Hg mining area, gold mining area, zinc smelting area and coal-fired power plant area, respectively, and positive shifts of δ²⁰²Hg_MeHg from fish/rice to human hair occurred during human metabolic processes. Therefore, the CSIA approach can be an effective tool for tracking Hg biogeochemical cycle and human exposure, from which new scientific knowledge can be generated to support Hg pollution control policies and to protect human health.

Internal Dynamics and Metabolism of Mercury in Biota: A Review of Insights from Mercury Stable Isotopes

Monitoring mercury (Hg) levels in biota is considered an important objective for the effectiveness evaluation of the Minamata Convention. While many studies have characterized Hg levels in organisms at multiple spatiotemporal scales, concentration analyses alone often cannot provide sufficient information on the Hg exposure sources and internal processes occurring within biota. Here, we review the decadal scientific progress of using Hg isotopes to understand internal processes that modify the speciation, transport, and fate of Hg within biota. Mercury stable isotopes have emerged as a powerful tool for assessing Hg sources and biogeochemical processes in natural environments. A better understanding of the tissue location and internal mechanisms leading to Hg isotope change is key to assessing its use for biomonitoring. We synthesize the current understanding and uncertainties of internal processes leading to Hg isotope fractionation in a variety of biota, in a sequence of better to less studied organisms (i.e., birds, marine mammals, humans, fish, plankton, and invertebrates). This review discusses the opportunities and challenges of using certain forms of biota for Hg source monitoring and the need to further elucidate the physiological mechanisms that control the accumulation, distribution, and toxicity of Hg in biota by coupling new techniques with Hg stable isotopes.

Geo-Environmental Characterisation of High Contaminated Coastal Sites: The Analysis of Past Experiences in Taranto (Southern Italy) as a Key for Defining Operational Guidelines

Despite its remarkable geomorphological, ecological, and touristic value, the coastal sector of the Apulia region (Southern Italy) hosts three of the main contaminated Italian sites (Sites of National Interest, or SINs), for which urgent environmental remediation and reclamation actions are required. These sites are affected by intense coastal modification and diffuse environmental pollution due to the strong industrialisation and urbanisation processes that have been taking place since the second half of the XIX century. The Apulian coastal SINs, established by the National Law 426/1998 and delimited by the Ministerial Decree of 10 January 2000, include large coastal sectors and marine areas, which have been deeply investigated by the National Institution for the Environmental Research and Protection (ISPRA) and the Regional Agency for the Prevention and Protection of the Environment (ARPA) with the aim of obtaining a deep environmental characterisation of the marine matrices (sediments, water, and biota). More recently, high-resolution and multidisciplinary investigations focused on the geo-environmental characterisation of the coastal basins in the SIN Taranto site have been funded by the “Special Commissioner for the urgent measures of reclamation, environmental improvements, and redevelopment of Taranto”. In this review, we propose an overview of the investigations carried out in the Apulian SINs for the environmental characterisation of the marine matrices, with special reference to the sea bottom and sediments. Based on the experience gained in the previous characterisation activities, further research is aimed at defying a specific protocol of analysis for supporting the identification of priority actions for an effective and efficient geo-morphodynamic and environmental characterisation of the contaminated coastal areas, with special reference to geomorphological, sedimentological, and geo-dynamic features for which innovative and high-resolution investigations are required.

Compound-Specific Stable Isotope Analysis Provides New Insights for Tracking Human Monomethylmercury Exposure Sources

Monomethylmercury (MMHg) exposure can induce adverse neurodevelopmental effects in humans and is a global environmental health concern. Human exposure to MMHg occurs predominately through the consumption of fishery foods and rice in Asia, but it is challenging to quantify these two exposure sources. Here, we innovatively utilized MMHg compound-specific stable isotope analyses (MMHg-CSIA) of the hair to quantify the human MMHg sources in coastal and inland areas, where fishery foods and rice are routinely consumed. Our data showed that the fishery foods and rice end members had distinct Δ¹⁹⁹Hg_MMHg values in both coastal and inland areas. The Δ¹⁹⁹Hg_MMHg values of the human hair were comparable to those of fishery foods but not those of rice. Positive shifts in the δ²⁰²Hg_MMHg values of the hair from diet were observed in the study areas. Additionally, significant differences in δ²⁰²Hg versus Δ¹⁹⁹Hg were detected between MMHg and inorganic Hg (IHg) in the human hair but not in fishery foods and rice. A binary mixing model was developed to estimate the human MMHg exposures from fishery foods and rice using Δ¹⁹⁹Hg_MMHg data. The model results suggested that human MMHg exposures were dominated (>80%) by fishery food consumption and were less affected by rice consumption in both the coastal and inland areas. This study demonstrated that the MMHg-CSIA method can provide unique information for tracking human MMHg exposure sources by excluding the deviations from dietary surveys, individual MMHg absorption/demethylation efficiencies, and the confounding effects of IHg.

Organochlorines and Polycyclic Aromatic Hydrocarbons as fingerprint of exposure pathways from marine sediments to biota

To elucidate the dynamics of a suite of organochlorine contaminants (PCBs, HCB), PAHs and Hg and verify the potential of these pollutants as reliable fingerprints of sources, an ensemble of marine sediments and organisms (finfish, shellfish species and Mytilus galloprovincialis) were analysed from the contaminated Augusta Bay (Southern Italy). The Hg and HCB concentration in the sediments exceeded the EQS of the Directive 2000/60/EU. Similarly, ∑PCB and selected PAHs were above the threshold limit set by regulation. The marine organisms showed Hg concentrations above CE 1881/2006. Contaminants in transplanted mussel evidenced an increased accumulation overtime and different distribution patterns between sampling sites. Analysis of the homolog composition of PCB congeners revealed comparable patterns between sediments and marine organisms and offered the opportunity to define a robust fingerprint for tracing contaminants transfer from the abiotic to the biotic compartments. These results were confirmed by the Fluoranthene/Pyrene, Hg and HCB distribution modes.

Use of mercury isotopes to quantify sources of human inorganic mercury exposure and metabolic processes in the human body

The pathways of human mercury (Hg) exposure are complex and accurate understanding of relative contributions from different pathways are crucial for risk assessment and risk control. In this study, we determined total Hg concentration and Hg isotopic composition of human urine, dietary components, and inhaled air in the Wanshan Hg mining area (MA), Guiyang urban area (UA), and Changshun background area (BA) to understand Hg exposure sources and metabolic processes in human body. At the three studied sites, total gaseous mercury (TGM) showed negative δ²⁰²Hg (-3.11‰ to + 1.12‰) and near-zero Δ¹⁹⁹Hg (-0.16‰ to + 0.13‰), which were isotopically distinguishable from Hg isotope values of urine (δ²⁰²Hg: -4.02‰ to - 0.84‰; Δ¹⁹⁹Hg: -0.14‰ to 0.64‰). We observed an offset of -1.01‰ to -1.6‰ in δ²⁰²Hg between TGM and urine samples, and an offset of -1.01‰ to 0.80‰ in δ²⁰²Hg between rice and urine samples, suggesting that lighter isotopes are more easily accumulated in the kidneys and excreted by urine. We proposed that the high positive Δ¹⁹⁹Hg in urine samples of UA was derived from fish consumption. The results of a binary mixing model based on Δ¹⁹⁹Hg were compared with those from a classic dietary model. The results from the MIF binary model showed that fish consumption accounted for 22% of urine Hg in the families at UA, whereas fish consumption contributed limited Hg to MA and BA. This study highlighted that Hg isotopes can be a useful tracer in understanding the sources and fates of Hg in human bodies.

Trace elements contamination assessment in marine sediments from different regions of the Caribbean Sea

Trace elements (TEs), rare earth elements (REEs), and methylmercury (MeHg) concentrations as well as mercury (Hg) and lead (Pb) isotope compositions in sediment samples collected from strategic locations along the Caribbean Sea were determined. The analyzed sediment samples were collected at different core depths from localities in Colombia, Cuba, Haiti, and the Dominican Republic. The evaluation of pollution assessment indices i.e. enrichment factors and geoaccumulation index revealed significant enrichment of several priority substances, such as Pb, Cd and Hg, in most of the sampling sites. Hg was found in extremely high concentrations (up to 22 ± 3 mg kg^-1) in bottom samples of Colombian core, which led the authors to further investigate this area with respect to the source for Hg contamination. The analysis of Hg isotope ratios in Colombian sediments and the Pb isotope ratios in all studied cores, helped in the identification of likely pollution sources and represents a critically important record of anthropogenic influence in the region. Finally, the REEs patterns determined in all samples, also provide a needed baseline for these contaminants in the Caribbean region.

Mercury isotope signatures in sediments and marine organisms as tracers of historical industrial pollution

Isotopic composition of mercury (Hg) in marine organisms and sediment cores was used to identify sources and reconstruct historical trends of contamination in the coastal-marine area of Rosignano Solvay (Italy), affected by Hg pollution from a chlor-alkali plant on the near land. Sediments show a wide range of Hg concentration and Hg isotope signatures. Particularly, coupled Hg concentration and δ²⁰²Hg values trace inputs from different sources. The two depth-profiles clearly indicate three distinct periods: "pre-industrial" (before 1941), "industrial" (between 1941 and 2007) and "post-industrial" (after 2007) ages. This is also corroborated by sediment chronology, using ²¹⁰Pb dating method, validated through ¹³⁷Cs. Marine organisms are characterized by Hg isotope signatures comparable to "post-industrial" surface sediments. Notably, specimens of Mullus spp. evidence isotope composition comparable to the "industrial" sediments, thus suggesting a still active role of those sediments as source of Hg for the benthic fish compartment. The small amount of MIF and the Δ¹⁹⁹Hg/Δ²⁰¹Hg ratio recorded in organisms are reasonably consistent with limited processes of MMHg demethylation in the water column.

Heavy Metals and PAHs in Meat, Milk, and Seafood From Augusta Area (Southern Italy): Contamination Levels, Dietary Intake, and Human Exposure Assessment

Heavy metals and PAHs were measured in animal foodstuffs from Augusta-Melilli-Priolo area in order to evaluate the potential human health risk associated to their consumption. All heavy metals were detected in seafood products while most of them were 1 for baby, children and teenagers, indicating a non-carcinogenic risk for these age categories by seafood ingestion. The CRAs overcame 1*10-5 for almost age categories (except "baby") and for elderly, by seafood and beef ingestions respectively. Moreover, the MOE for PAHs showed a certain cancer risk for "baby" related to cow milk ingestion.

Patterns of fish and whale consumption in relation to methylmercury in hair among residents of Western Canadian Arctic communities

BACKGROUND

Methylmercury contamination of the environment represents a substantial environmental health concern. Human exposure to methylmercury occurs primarily through consumption of fish and marine mammals. Heavily exposed subgroups include sport or subsistence fishers residing in Arctic communities. We aimed to estimate the association of fish/whale consumption patterns of Canadian Arctic subsistence fishers with the internal dose of methylmercury as measured in hair.

METHODS

This research was conducted within ongoing community projects led by the CANHelp Working Group in Aklavik and Fort McPherson, Northwest Territories and Old Crow, Yukon. We interviewed each participant using a fish-focused food-frequency questionnaire during September-November 2016 and collected hair samples concurrently. Methylmercury was measured in the full-length of each hair sample using gas chromatography inductively-coupled plasma-mass spectrometry. Multivariable linear regression estimated beta-coefficients and 95% confidence intervals (CIs) for the effect of fish/whale consumption on hair-methylmercury concentrations.

RESULTS

Among 101 participants who provided hair samples and diet data, the mean number of fish/whale species eaten was 3.5 (SD:1.9). The mean hair-methylmercury concentration was 0.60 μg/g (SD:0.47). Fish/whale consumption was positively associated with hair-methylmercury concentration, after adjusting for sex, hair length and use of permanent hair treatments. Hair-methylmercury concentrations among participants who consumed the most fish/whale in each season ranged from 0.30-0.50 μg/g higher than those who consumed < 1 meal/week.

CONCLUSIONS

In this population of Canadian Arctic subsistence fishers, hair-methylmercury concentration increased with fish/whale consumption, but the maximum concentrations were below Health Canada's 6.0 μg/g threshold for safe exposure.

Isotopic tracing of mercury sources in estuarine-inner shelf sediments of the East China Sea

Large river estuarine-inner shelf systems play an important role in the coastal biogeochemical cycling of heavy metals; however, the source-to-sink of mercury (Hg) in these environments remain poorly understood. In this study, the Hg isotopic composition of surface sediments in the Yangtze River Estuary (YRE) and inner shelf of the East China Sea (ECS) were examined to quantitatively track Hg sources in this region. We detected large spatial variation in δ²⁰²Hg (-1.88 to -0.29‰) and Δ¹⁹⁹Hg (-0.22 to 0.13‰) in sediments of the YRE-ECS inner shelf. The impact of sediment resuspension and transport from the YRE to the inner shelf of the ECS could have little effect on Hg isotopic composition, and the two regions shared similar Hg isotopic composition. An isotope-based triple mixing model further revealed major contributors to sediment Hg from industrial Hg discharge into water (51.8 ± 24.5%), soil Hg from surface runoff (29.2 ± 17.0%), and precipitation-derived atmospheric deposition Hg (19.1 ± 17.5%). The Hg isotopic compositions of the YRE sediments and other local river estuaries were similar to those of direct industrial Hg discharge, indicating that contaminated riverine discharge was the dominant Hg source for estuarine and adjacent shelf areas. Soil Hg delivered through surface runoff was the primary source of Hg to the coastal areas not near large river estuaries, whereas precipitation-derived atmospheric deposition had a greater influence on offshore sediment Hg content. Industrial Hg discharged to rivers had the highest mean depositional flux (35.0 ± 27.3 ng cm^-2 yr^-1) and mass inventory (25.6 t yr^-1), accounting for 77.4% of the total Hg variance. The findings of this study demonstrate that large rivers such as the Yangtze River can supply substantial amounts of industrial Hg to the estuary and adjacent shelf.

Carbonic anhydrase integrated into a multimarker approach for the detection of the stress status induced by pollution exposure in Mytilus galloprovincialis: A field case study

The work was addressed to study the sensitivity of the enzyme carbonic anhydrase (CA) to chemical pollution in the hepatopancreas of the bioindicator organism Mytilus galloprovincialis in the context of a multimarker approach in view of ecotoxicological biomonitoring and assessment application. The study was carried out by means of a transplanting experiment in the field, using caged organisms from an initial population exposed in the field in two areas of interest: Augusta-Melilli-Priolo, an heavy polluted industrial site (eastern Sicily, Italy), and Brucoli (eastern Sicily, Italy) an area not affected by any contamination and selected as a reference site. Mussels in Augusta presented a significant increase in the digestive gland CA activity and gene expression compared to the animals caged in the control site of Brucoli. The CA response in animals from the polluted site was paralleled by proliferation/increase in the size of lysosomes, as assessed by Lysosensor green charged cells, induction of metallothionein, up-regulation of hif-α (hypoxia-inducible factor), metabolic changes associated with protein metabolism, and changes in the condition factor. Biological responses data were integrated with information about sediment chemical analysis and metal residue concentration in animal soft tissues. In conclusion, obtained results highlighted the induction of CAs in the hepatopancreas of Mytilus galloprovincialis following to pollution exposure, and demonstrated its suitability to be integrated into a multimarker approach for the detection and characterization of the stress status induced by pollution exposure in this bioindicator organism.

Assessment of Hg contamination by a Chlor-Alkali Plant in riverine and coastal sites combining Hg speciation and isotopic signature (Sagua la Grande River, Cuba)

Chlor-alkali plants (CAP) are recognized as major sources of mercury (Hg) in the environment. In this work, Hg concentration, speciation and isotopic signature were determined in sediments and biota (fish and oyster) from Sagua La Grande River (SG River) and the adjacent coastal zone in the vicinity of a CAP (Cuba). High Hg concentrations in surface sediments (up to 5072 ng g^-1), mainly occurring as inorganic Hg, decrease with the distance from the CAP along the SG River and seaward. Meanwhile, Hg concentration and speciation in riverine catfish (Claria gariepinus) muscle (1093 ± 319 ng g^-1, ˜70% as MeHg) and coastal oysters (Crassostrea rizophorae) (596 ± 233 ng g^-1, ˜50% as MeHg) indicate a direct impact from CAP. Hg isotopic signature in sediments, following both mass dependent (MDF) and mass independent fractionation (MIF), exhibits a clear binary mixing between CAP pollution (+0.42‰, δ²⁰²Hg; -0.18‰, Δ²⁰¹Hg) and regional background end-member (˜ -0.49‰, δ²⁰²Hg; +0.01‰, Δ²⁰¹Hg). The combination of speciation and isotopic information in biota and sediments allows to trace Hg contamination pathways from contaminated sediments to the biota, establishing the importance of both methylation and demethylation extent in both river and coastal sites before Hg species bioaccumulation.

Liver melanomacrophage centres and CYP1A expression as response biomarkers to environmental pollution in European anchovy (Engraulis encrasicolus) from the western Mediterranean Sea

The goal of the present study was to verify the suitability of using melanomacrophage centres (MMCs) as response biomarkers of marine pollution in European anchovy, which are short-lived, migratory, small pelagic fish. This suitability was verified by analysing the MMC density and cytochrome P450 monooxygenase 1A (CYP1A) expression in livers of anchovies from four areas of southern Italy. Age 2 anchovies sampled from three areas exposed to pollutants of industrial/agricultural origin (Gulf of Gela, Mazara del Vallo and Gulf of Naples) showed liver areas occupied by MMCs and numbers of MMCs that were significantly higher than those in the anchovies from Pozzallo, which is a marine area not subjected to any source of pollution. Anti-CYP1A immunoreactivity was observed in the hepatocytes of all specimens sampled from the Gulf of Gela. These findings suggest the utility of liver MMCs as biomarkers of exposure to pollutants in this small pelagic fish.

Use of Mercury Isotopes to Quantify Mercury Exposure Sources in Inland Populations, China

Mercury (Hg) isotopic compositions in hair and dietary sources from Wanshan (WS) Hg mining area, Guiyang (GY) urban area, and Changshun (CS) rural area were determined to identify the major Hg exposure sources of local residents. Rice and vegetables displayed low δ²⁰²Hg and small negative to zero Δ¹⁹⁹Hg, and are isotopically distinguishable from fish which showed relatively higher δ²⁰²Hg and positive Δ¹⁹⁹Hg. Distinct isotopic signatures were also observed for human hair from the three areas. Shifts of 2 to 3‰ in δ²⁰²Hg between hair and dietary sources confirmed mass dependent fractionation of Hg isotopes occurs during metabolic processes. Near zero Δ¹⁹⁹Hg of hair from WS and CS suggested rice is the major exposure source. Positive Δ¹⁹⁹Hg of hair from GY was likely caused by consumption of fish. A binary mixing model based on Δ¹⁹⁹Hg showed that rice and fish consumption accounted for 59% and 41% of dietary Hg source for GY residents, respectively, whereas rice is the major source for WS and CS residents. The model output was validated by calculation of probable daily intake of Hg. Our study suggests that Hg isotopes can be a useful tracer for quantifying exposure sources and understanding metabolic processes of Hg in humans.

Marine pollution in the Libyan coastal area: Environmental and risk assessment

A comprehensive assessment of the potential adverse effects on environment and human health generated by the inputs of chemicals from the most important Libyan petrochemical plant is presented. Ecotoxicological risk associated with the presence of As, Hg, Ni, Zn and PAHs in marine sediments is low or moderate, with a probability of toxicity for ecosystem <9% and <20% for heavy metals and PAHs respectively. However, surface sediments result strongly enriched in Hg and As of anthropogenic origin. Investigation of metals in fish allowed to assess potential risks for human populations via fish intake. Target hazard quotients values indicate potential risk associated to toxic metals exposure by fish consumption and lifetime cancer risk (TR) values highlight a potential carcinogen risk associated to As intake. Noteworthy, the presented results provide an unprecedented environmental dataset in an area where the availability of field data is very scant, for a better understanding of anthropogenic impacts at Mediterranean scale.

Mercury Isotope Signatures of Methylmercury in Rice Samples from the Wanshan Mercury Mining Area, China: Environmental Implications

Rice consumption is the primary pathway of methylmercury (MeHg) exposure for residents in mercury-mining areas of Guizhou Province, China. In this study, compound-specific stable isotope analysis (CSIA) of MeHg was performed on rice samples collected in the Wanshan mercury mining area. An enrichment of 2.25‰ in total Hg (THg) δ²⁰²Hg was observed between rice and human hair, and THg Δ¹⁹⁹Hg in hair was 0.12‰ higher than the value in rice. Rice and human hair samples in this study show distinct Hg isotope signatures compared to those of fish and human hair of fish consumers collected in China and other areas. Distinct Hg isotope signatures were observed between IHg and MeHg in rice samples (in mean ± standard deviation: δ²⁰²Hg_IHg at -2.30‰ ± 0.49‰, Δ¹⁹⁹Hg_IHg at -0.08‰ ± 0.04‰, n = 7; δ²⁰²Hg_MeHg at -0.80‰ ± 0.25‰, Δ¹⁹⁹Hg_MeHg at 0.08‰ ± 0.04‰, n = 7). Using a binary mixing model, it is estimated that the atmospheric Hg contributed 31% ± 16% of IHg and 17% ± 11% of THg in the rice samples and the IHg in soil caused by past mining activities contributed to the remaining Hg. This study demonstrated that Hg stable isotopes are good tracers of human MeHg exposure to fish and rice consumption, and the isotope data can be used for identifying the sources of IHg and MeHg in rice.

Diet and habitat use influence Hg and Cd transfer to fish and consequent biomagnification in a highly contaminated area: Augusta Bay (Mediterranean Sea)

Total mercury (T-Hg) and cadmium (Cd) were measured in twenty species of fish to study their bioaccumulation patterns and trophodynamics in the Augusta Bay food web. Adult and juvenile fish were caught in 2012 in Priolo Bay, south of the Augusta harbour (Central Mediterranean Sea), which is known for the high trace element and polycyclic aromatic hydrocarbon contamination level. T-Hg concentration was found to significantly increase along δ¹⁵N and from pelagic to benthic sedentary fish, revealing a marked influence of trophic position and habitat use (sensu Harmelin 1987) on T-Hg accumulation within ichthyofauna. Cd showed the opposite pattern, in line with the higher trace element (TE) excretion rates of high trophic level fish and the lower level of Cd environmental contamination. Trophic pathways were first characterised in the Priolo Bay food web using carbon and nitrogen stable isotopes (δ¹³C, δ¹⁵N) and a single main trophic pathway characterised the Priolo Bay food web. Biomagnification was then assessed, including basal sources (surface sediment, macroalgae), zooplankton, benthic invertebrates and fish. T-Hg and Cd were found to biomagnify and biodilute respectively based on the significant linear regressions between log[T-Hg] and log[Cd] vs. δ¹⁵N of sources and consumers and the trophic magnification factors (TMFs) of 1.22 and 0.83 respectively. Interestingly, different Cd behaviour was found considering only the benthic pathway which leads to the predatory gastropod Hexaplex trunculus. The positive slope and the higher TMF indicated active biomagnification in this benthic food web due to the high bioaccumulation efficiency of this benthic predator. Our findings provide new evidences about the role of Priolo sediments as a sources of pollutants for the food web, representing a threat to fish and, by domino effect, to humans.

Assessment of mercury exposure in human populations: A status report from Augusta Bay (southern Italy)

Here we investigate mercury concentrations in the blood (HgB), urine (HgU) and human hair (HgH) of 224 individuals from a coastal area (Eastern Sicily, SE Italy) strongly affected by Hg contamination from one of the largest chlor-alkali plants in Europe. The factors affecting the distribution of Hg and the extent of the exposure of individuals have been explored with a multidisciplinary approach. Multiple regression analyses, together with evidence of high levels of HgB (exceeding the HBMI recommended levels in 50% of cases) and HgH (exceeding the EPA reference dose in 70% of cases), primarily suggest that the consumption of local fish is the main source of Hg for humans. no. significant exposure to inorganic mercury was identified. Toxicokinetic calculations produced a provisional tolerable weekly intake (PTWI) level that, in most cases, exceeds international recommendations, particularly for residents in the studied area.

DoE optimization of a mercury isotope ratio determination method for environmental studies

By using the experimental design (DoE) technique, we optimized an analytical method for the determination of mercury isotope ratios by means of cold-vapor multicollector ICP-MS (CV-MC-ICP-MS) to provide absolute Hg isotopic ratio measurements with a suitable internal precision. By running 32 experiments, the influence of mercury and thallium internal standard concentrations, total measuring time and sample flow rate was evaluated. Method was optimized varying Hg concentration between 2 and 20 ng g(-1). The model finds out some correlations within the parameters affect the measurements precision and predicts suitable sample measurement precisions for Hg concentrations from 5 ng g(-1) Hg upwards. The method was successfully applied to samples of Manila clams (Ruditapes philippinarum) coming from the Marano and Grado lagoon (NE Italy), a coastal environment affected by long term mercury contamination mainly due to mining activity. Results show different extents of both mass dependent fractionation (MDF) and mass independent fractionation (MIF) phenomena in clams according to their size and sampling sites in the lagoon. The method is fit for determinations on real samples, allowing for the use of Hg isotopic ratios to study mercury biogeochemical cycles in complex ecosystems.