Mercury fractionation in marine macrofauna using thermodesorption technique: Method and its application

Mercury, methylmercury, and its fractions at the base of the trophic pyramid of the maritime Antarctic ecosystem of Admiralty Bay

Mercury (Hg) pollution in polar regions is a critical environmental concern, exacerbated by glacier melting due to climate change. This study investigated the impact of glacial meltwater on total mercury (THg), methylmercury (MeHg), and various Hg fractions levels in seawater, suspended particulate matter, and microplankton in Admiralty Bay, Antarctica. Stable isotope analyses of carbon and nitrogen complement Hg measurements, providing insights into food web dynamics and pollutant transfer. The average THg concentration in water samples from creeks, which may represent runoff from melting glaciers and snow, was 2.5 times higher than in sea water from Admiralty Bay. The proportion of methylmercury in total mercury varied depending on the environmental component: in water, it was 1.1 %; in SPM, 0.7 %; and in microplankton, 2.4 %. Increased microplankton biomass, which provides a larger surface area, enhanced the proportion of adsorbed HgF1, in microplankton, indicating that mercury adsorbs onto available planktonic surfaces. This research enhances our understanding of Hg cycling in Antarctic ecosystems and underscores the implications of climate change for Hg contamination, with potential effects on marine food webs and human health.

Impact of sediment resuspension on near-bottom mercury dynamics: Insights from a Baltic Sea experiment

Marine sediments are major sources of legacy pollution, capable of releasing toxic mercury (Hg) into the water column when disturbed. This study evaluated Hg remobilization from surface sediments during resuspension events by examining sediment properties, Hg concentrations, and speciation. Research was conducted in the southern Baltic Sea, representing diverse environmental conditions and human impacts. The findings showed that sediment resuspension was the primary driver of Hg remobilization, with diffusion flux playing a minimal role. Both dissolved and particulate Hg were released almost immediately after resuspension, with elevated concentrations persisting long enough to be transported beyond the disturbed area. The diffusion of dissolved Hg was enhanced by labile Hg fractions in the sediment, with reducing conditions and high organic matter content further promoting this process. Particulate Hg remobilization was influenced by sediment characteristics, particularly bulk density, which affected resuspension susceptibility and dispersion of suspended matter. The total Hg concentration and labile organic-bound Hg fractions also significantly influenced particulate Hg release. These results highlight the importance of sediment properties in managing Hg-contaminated sites and have implications for environmental protection and marine operations planning.

Comparison of the Performance of ICP-MS, CV-ICP-OES, and TDA AAS in Determining Mercury in Marine Sediment Samples

Mercury (Hg) determination in marine sediment is an analytical challenge due to the toxicity of this element even at low concentrations (up to 130 μg kg-1 in marine sediments) and complex matrices. Therefore, it is necessary to use analytical techniques that have high sensitivity, selectivity, and low limits of quantification (LoQ). In this study, two methods that require sample treatment and one method with direct sampling were studied. The techniques studied were inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry with cold vapor generation (CV-ICP-OES), and atomic absorption spectrometry with thermodecomposition and amalgamation (TDA AAS) for Hg determination in marine sediment samples. Since ICP-MS has more studies in the literature, optimization with design of experiments was developed for CV-ICP-OES and TDA AAS. Although it was found to have low levels of instrumental LoQ for all three techniques, differences were found once the method LoQ was calculated. The calculation for method LoQ considers all analytical procedures executed, including sample treatment, which provides a 100-fold dilution for ICP-MS and CV-ICP-OES. The method LoQ obtained were 1.9, 165, and 0.35 μg kg-1 for ICP-MS, CV-ICP-OES, and TDA AAS, respectively. Comparing marine sediment sample analyses, Hg concentrations had no statistical difference when determined by ICP-MS and TDA AAS. It was not possible to determine Hg in marine sediment samples by CV-ICP-OES due to the high method LoQ obtained (165 μg kg-1). Although ICP-MS has the advantage of being a multielemental technique, it is high-value equipment and needs a large volume of argon, which has a high cost in the market, and it requires sample treatment. On the other hand, TDA AAS-based spectrometer DMA-80 performs direct sampling, avoiding the pretreatment stage, and has a relatively lower cost, both in terms of initial investment and maintenance, while maintaining the high sensitivity, accuracy, and precision required for Hg determination on marine sediment samples.

Impact of biometric parameters and seasonal condition on mercury (Hg) distribution in Harris mud crab (Rhithropanopeus harrisii) body

Mercury is a potent neurotoxin. The toxicity of Hg depends on the form in which it occurs, which consequently determines its bioavailability to the organism. The processes of distribution and elimination of Hg in organisms from lower trophic levels are still poorly understood. Therefore, in the present study, great point was paid separately to the soft tissues and hard tissues, which may play an important role in the detoxification of the crab's body from neurotoxicant. The study was conducted on the non-native species: Harris mud crab, collected in 2020. Concentrations of total mercury and its forms were carried out using a Direct Mercury Analyzer, DMA-80 (Milestone, Italy). Sex did not determine the Hg concentration of its forms in R. harrisii. Organism size influenced on crab body processes: biodilution of Hg during growth in summer and bioaccumulation of Hg before stagnation in autumn. The distribution of Hg in the crab's soft tissues and walking legs was related to the trophic origin of the mercury, while halide-bound mercury and semilabile forms and HgS were redistributed into the crab's carapace. This protects the soft tissue of crabs against the toxic effect of Hg. Consequently, a smaller load of Hg in the crabs can be introduced to the circulation or biomagnified in the food web in the region where R. harrisii is an important link of the trophic chain.

Seasonality of mercury and its fractions in microplastics biofilms -comparison to natural biofilms, suspended particulate matter and bottom sediment

Biofilms can enhance the sorption of heavy metals onto microplastic (MP) surfaces. However, most research in this field relies on laboratory experiments and neglects metal fractions and seasonal variations. Further studies of the metal/biofilm interaction in the aquatic environment are essential for assessing the ecological threat that MPs pose. The present study used in situ experiments in an environment conducive to biofouling (Vistula Lagoon, Baltic Sea). The objective was to investigate the sorption of mercury and its fractions (thermodesorption technique) in MP (polypropylene-PP, polystyrene-PS, polylactide-PLA) biofilms and natural matrices across three seasons. After one month of incubation, the Hg concentrations in MP and natural substratum (gravel grains-G) biofilms were similar (MP: 145 ± 45 ng/g d.w.; G: 132 ± 23 ng/g d.w.) and approximately twofold those of suspended particulate matter (SPM) (63 ± 27 ng/g d.w.). Hg concentrations in biofilms and sediments were similar, but labile fractions dominated in biofilms and stable fractions in sediments. Seasonal Hg concentrations in MP biofilms decreased over summer>winter>spring, with significant variation for mineral and loosely bound Hg fractions. Multiple regression analysis revealed that hydrochemical conditions and sediment resuspension played a crucial role in the observed variability. The influence of polymer type and morphology (pellets, fibres, aged MP) on Hg sorption in biofilms was visible only in high summer temperatures. In this season, PP fibres and aged PP pellets encouraged biofilm growth and the accumulation of labile Hg fractions. Additionally, high concentrations of mineral (stable and semi-labile) Hg fractions were found in expanded PS biofilms. These findings suggest that organisms that ingest MPs or feed on the biofilms are exposed to the adverse effects of Hg and the presence of MPs in aquatic ecosystems may facilitate the transfer of mercury within the food chain.

Mercury fingerprint: A comparative evaluation of lability in North Sea drill cuttings

Quantifying impacts on marine ecosystems remains pivotal in estimating risks associated with offshore industry practices. Cuttings piles, formed during drilling operations, are commonly abandoned in situ, and left to attenuate on the seabed. In the present work, the presence and lability of mercury in samples obtained from drill cuttings piles of two decommissioned North Sea oil platforms (bp Miller and bp North West Hutton) and the surrounding sediment were investigated. Maximum concentrations of total mercury were measured at 0.23 and 0.37 μg/g dry weight (dw) for bp Miller and bp North West Hutton, respectively. Background concentrations of 3.6 and 8.3 ng/g dw were measured at reference sites at 3200 metre distance. Thermofractionation and DGT-analysis of the samples to assess the effective environmental impact of the measured mercury suggests that although total mercury concentrations are increased in the proximity of the cuttings pile, the effective environmental impact may be limited.

Mercury dynamics at the base of the pelagic food web of the Gulf of Gdańsk, southern Baltic Sea

Planktonic organisms, which have direct contact with water, serve as the entry point for mercury (Hg), into the marine food web, impacting its levels in higher organisms, including fish, mammals, and humans who consume seafood. This study provides insights into the distribution and behavior of Hg within the Baltic Sea, specifically the Gulf of Gdańsk, focusing on pelagic primary producers and consumers. Phytoplankton Hg levels were primarily influenced by its concentrations in water, while Hg concentrations in zooplankton resulted from dietary exposure through suspended particulate matter and phytoplankton consumption. Hg uptake by planktonic organisms, particularly phytoplankton, was highly efficient, with Hg concentrations four orders of magnitude higher than those in the surrounding water. However, unlike biomagnification of Hg between SPM and zooplankton, biomagnification between zooplankton and phytoplankton was not apparent, likely due to the low trophic position and small size of primary consumers, high Hg elimination rates, and limited absorption.

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.

The non-selective Antarctic filter feeder Salpa thompsoni as a bioindicator of mercury origin

Hg is considered as the most toxic metal in the environment. Sources of Hg in the environment include burning fossil fuels, burning waste, and forest fires. The long residence time of the gaseous form in the atmosphere allows mercury to be transported over long distances. The pelagic tunicate Salpa thompsoni is an important component of the Antarctic environment. Over the past few decades an expansion of this species to the higher latitudes has been noted, mainly due to the ongoing climate change. The study material consisted of samples of S. thompsoni individuals, collected in the waters surrounding Elephant Island (Western Antarctic). Total mercury and five of its fractions were determined. Whole organisms were analyzed as well as internal organs: stomachs, muscle strips, and tunics. Obtained results showed that the highest concentrations of mercury in salps were observed in stomachs. With the Hg fraction results, it can be concluded that the main route of exposure of S. thompsoni to Hg is presumably absorption from the food-filtered organic and non-organic particles. Moreover, the process of transformation of simple soluble forms into organic forms of Hg in stomachs and intestines and its distribution to other tissues was observed.

Mercury concentrations in Antarctic zooplankton with a focus on the krill species, Euphausia superba

The Antarctic is the most isolated region in the world; nevertheless, it has not avoided the negative impact of human activity, including the inflow of toxic mercury (Hg). Hg deposited in the Antarctic marine environment can be bioavailable and accumulate in the food web, reaching elevated concentrations in high-trophic-level biota, especially if methylated. Zooplankton, together with phytoplankton, are critical for the transport of pollutants, including Hg to higher trophic levels. For the Southern Ocean ecosystem, one of the key zooplankton components is the Antarctic krill Euphausia superba, the smaller euphausiid Thysanoessa macrura, and the amphipod Themisto gaudichaudii - a crucial food source for most predatory fish, birds, and mammals. The main goal of this study was to determine the Hg burden, as well as the distribution of different Hg forms, in these dominant Antarctic planktonic crustaceans. The results showed that the highest concentrations of Hg were found in T. gaudichaudii, a typically predatory taxon. Most of the Hg in the tested crustaceans was labile and potentially bioavailable for planktivorous organisms, with the most dangerous methylmercury (MeHg) accounting for an average of 16 % of the total mercury. Elevated Hg concentrations were observed close to the land, which is influenced by the proximity to penguin and pinniped colonies. In areas near the shore, volcanic activity might be a possible cause of the increase in mercury sulfide (HgS) content. The total Hg concentration increased with the trophic position and ontogenetic stage of predation, specific to adult organisms. In contrast, the proportion of MeHg decreased with age, indicating more efficient demethylation or elimination. The Hg magnification kinetics in the study area were relatively high, which may be related to climate-change induced alterations of the Antarctic ecosystem: additional food sources and reshaped trophic structure.

Factors determining bioaccumulation of neurotoxicant Hg in the zebra mussels (Dreissena polymorpha): Influence of biometric parameters, sex and storage of shell

One of benthic organisms exposed to contact with mercury in the southern Baltic is alien species of clam: Dreissena polymorpha. As this organism is increasingly dynamic in various regions of the world including the southern Baltic region, it is reasonable to ask whether it tolerates elevated concentrations of xenobiotics? Does it effectively eliminate Hg? The study determined the effects of biometric parameters and water temperature on the rate of accumulation and efficiency of eliminating Hg from body. Investigations focused on the shell which represents poorly-recognized role in the process of Hg distribution in clams. The results showed that especially during warm season, clams effectively reduced the levels of Hg in their body by the biodilution of Hg and reproduction. Important factor influencing detoxification was Hg transfer from the soft tissue to the shell. This protects the soft tissue against the toxic effect of Hg.

Mobility and bioavailability of mercury in sediments of the southern Baltic sea in relation to the chemical fractions of iron: Spatial and temporal patterns

Marine sediments play a significant role as reservoirs for mercury (Hg), a bioaccumulative toxic pollutant that poses risks to human and ecosystem health. Iron (Fe) has been recognized as an influential factor in the complexation and bioavailability of Hg in sediments. However, limited studies have investigated the interactions between the chemical fractions of these elements in natural settings. This study aims to examine the fractions of Hg and Fe in sediments of the Baltic Sea, a region historically impacted by Hg pollution. The Hg fractions were determined using the thermodesorption technique, while sequential extraction was employed to identify the Fe fractions. The findings confirm the crucial role of Fe in the formation, as well as the horizontal and vertical distribution of labile and stable Hg in marine sediments. Factors such as the contribution of organic matter, the presence of reactive Fe, and Fe associated with sheet silicates emerged as significant drivers that positively influenced the content of the most labile Hg fractions, potentially affecting the mobility and bioavailability of Hg in the marine environment.

Is the inhalation influence on the level of mercury and PAHs in the lungs of the baltic grey seal (Halichoerus grypusgrypus)?

For many decades, mercury (Hg) has been recognized as one of the most dangerous environmental pollutants that negatively affects the ecosystem, including human health. Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic, toxic and potentially carcinogenic compounds. The process of respiration in addition to dietary intake is a significant source of these compounds to the human or marine mammalian body. Therefore, the aim of this study was to determine the sources of PAHs and labile forms of mercury in the lungs of dead seals found in the southern Baltic Sea. Of the PAHs: pyrene, fluoranthene and chrysene showed the highest concentrations. Considering the content of individual Hg fractions, the highest percentage was characterized by Hg _{labile 1b} (related to organic matter). In a few specimens, deviations from the trend described above were observed: a higher proportion of Hg _{labile 1a} (mainly halide-bound forms of mercury than the mean value which may indicate their origin from aerosols). Hg concentrations increased with seal age due to bioaccumulation and biomagnification of Hg from food; therefore, adsorption of atmospheric mercury on alveoli is probably of decreasing importance with seal age. Ratios obtained: FLA/PYR <1; B(a)A/CHR <1; FLA/(PYR + FLA) < 0.4 indicate a petrogenic source. In contrast, high correlations of B(a)A, FLA and PYR and CHR with Hg suggest a common source of PAHs and mercury - from food. Conversely, the presence of pyrogenic (combustion-derived) benzo(a)pyrene in the lungs of these mammals could indicate a respiratory route of entry. Mercury and PAHs in the lungs of the seals studied were mainly of trophic origin, but the results presented here make the hypothesis of an airborne influx of Hg and PAHs into the lungs from marine mammals plausible. This is of particular importance in juveniles (pups), who, at the initial stage of life, spend time on land and do not obtain food on their own.

Different pathways of accumulation and elimination of neurotoxicant Hg and its forms in the clam Atlantic rangia (Rangia cuneata)

Mercury (Hg) is one of the most hazardous environmental pollutants, negatively affecting the ecosystem. The pathways of Hg elimination are well recognized in organisms from higher trophic levels compared to invertebrates such as clams. The aim of this study was to identify pathways of Hg accumulation in an alien species clams: Rangia cuneata, which represented an unrecognized source of Hg into the trophic chain of the southern Baltic Sea. An important aspect of this study was to determine Hg detoxification processes based on physiological state and biometric parameters of the atlatntic rangia. Special consideration was given to the role of shell in this process and the form of Hg in which it occurred. The study was also considered in terms of geographical changes in the Hg concentration in clams and the factors involved. Sex did not determine the concentration of Hg and its fraction in clams soft tissue and shell. Clams detoxified xenobiotic effectively in summer when their metabolism was accelerated. As a result, clams grew faster in warmer water than they accumulated Hg. In addition, this process was intensified by their reproduction. The mass of accumulated mercury was higher in the shell mass than in the body mass in summer. Transfer of Hg from the body to the shell depended on the forms Hg, mostly HgS. Geographical changes in the mercury concentration in clams was related to the form of Hg in the sediment. In areas where were more fines sediment fraction and organic matter accumulated in the sediment, mercury was present in a less bioavailable form, which caused that clams had lower Hg concentrations in their body. With assumption that in the future, due to its increasingly frequent occurrence, atlatntic rangia will become more common component of fish diet, a smaller load of toxic mercury will be introduced to the marine trophic chain.

Mercury fractionation - Problems in method application

Mercury (Hg) is a global pollutant with a negative effect on human and ecosystem health. Mercury is toxic in all forms. The toxicity, however, varies depending on the form of mercury, determining its physical and chemical properties. Therefore, knowledge on the chemical speciation of mercury is key for the understanding of its transport and transformations in the environment. Analysis of mercury speciation, however, is time-consuming and involves high risk of contamination. The mercury thermodesorption method offers many new possibilities. The main advantages of this method are identifying which groups of compounds are being transformed in the atmosphere, sediment and soil, suspended matter and plankton, and in organisms from different trophic levels. A great advantage of the method is also its application in mercury analyzers, where it is possible to control the heating and cooling temperatures of. The standardisation of fractionation nomenclature for all matrices (both biotic and abiotic) will be helpful in application of this mercury fractionation method too. It has also disadvantages, mostly in the technical preparation of the analyzer. The analyzer must be prepared for fractionation: setting the ventilator and adjusting the PID parameters so that the pre-set heating (t1) and combustion (t2) times reach the set value in the method program. Also, any modification of the heater forces a re-optimisation of the method with mercury standards, as certified reference materials for Hg fractionation in environmental matrices are not available. The HgF2 fraction cannot be used as the methylmercury concentration, which is undoubtedly the biggest drawback of this method.

Mercury in the Polish part of the Baltic Sea: A response to decreased atmospheric deposition and changing environment

Our review of the literature showed that since the beginning of the socio-economic transformation in Poland in the 1990s, the downward trend in Hg emissions and its deposition in the southern Baltic Sea was followed by a simultaneous decrease in Hg levels in water and marine plants and animals. Hg concentrations in the biota lowered to values that pose no or low risk to wildlife and seafood consumers. However, in the first decade of the current century, a divergence between these two trends became apparent and Hg concentrations in fish, herring and cod, began to rise. Therefore, increasing emission-independent anthropogenic pressures, which affect Hg uptake and trophodynamics, remobilization of land-based and marine legacy Hg deposits, as well as the structure of the food web, can undermine the chances of reducing both the Hg pool in the marine environment and human Hg exposure from fish.

Effects of beach wrack on the fate of mercury at the land-sea interface - A preliminary study

Since the 1970s, the amount of aquatic plants and algae debris, called beach wrack (BW), has increased along the shores of industrialised regions. The strong ability of primary producers to accumulate pollutants can potentially result in their deposition on the beach along with the BW. Despite that, the fate and impact of such pollutants on sandy beach ecosystems have not been investigated so far. This study examines the fate of neurotoxic mercury and its labile and stable fractions in BW on sandy beaches of the Puck Bay (Baltic Sea). In addition to BW, beach sediments and wrack-associated macrofauna were also analysed. Rough estimations showed that Puck Bay beaches (58.8 km) may be a temporary storage of 0.2-0.5 kg of mercury, deposited on them along with the BW annually. A large proportion of Hg (89 ± 16%) in a BW was labile and potentially bioavailable. The contribution of Hg fractions in the BW was conditioned by the degree of its decomposition (molar C:N:P ratio). With the progressive degradation of BW, a decrease in the contribution of Hg adsorbed on its surface with a simultaneous increase in the proportion of adsorbed (intracellular), mercury was observed. BW accumulation decreased oxygen content and redox potential and increased methylmercury content in underlying sediments, indicating methylation. Hg concentrations in the studied fauna were up to 4 times higher than in the BW. The highest values occurred in a predatory sand bear spider and the lowest in a herbivorous sand hopper. Regardless of trophic position, most of Hg (92-95%) occurred as an absorbed fraction, which indicates about a 30% increase in relation to its share of BW. These findings suggest the significant role of BW as a mercury carrier in a land-sea interface and increased exposure of beach communities to the adverse effects of mercury in coastal ecosystems.

Mercury concentration and speciation in benthic organisms from Isfjorden, Svalbard

Polar regions are an important part of the global mercury cycle and interesting study sites due to different possible mercury sources. The full understanding of mercury transformations in the Arctic is difficult because this region is the systems in transition -where the effects of the global climate change are the most prominent. Benthic organisms can be valuable bioindicators of heavy metal contamination. In July 2018, selected benthic organisms: macroalgae, brittle stars, sea urchins, gastropods, and starfish were collected in Isfjorden, Spitsbergen. Two of the sampling stations were located inside the fjord system and one at the entrance to the fjord. The results showed that the starfish were the most contaminated with mercury. Total mercury concentrations in these organisms were at least 10 times higher than in other organisms. However, they effectively deal with mercury by transporting it to hard tissue. The dominant form of mercury was the labile form.

Variation in the Content of Different Forms of Mercury in River Catchments of the Southern Baltic Sea – Case Study

Mercury (Hg) is recognised as a global environmental pollutant. Despite numerous studies being conducted around the world, the transformation of mercury in natural environments is still not fully understood. In addition, increasing droughts and heavy rains are currently observed to contribute to changes in the circulation of Hg. The purpose of this study was to recognise the influence of extreme meteorological and hydrological conditions on the inflow of various forms of mercury to the coastal zone of the Bay of Puck. The studies were carried out at estuarial stations of four rivers belonging to the southern Baltic Sea catchment: Reda, Zagorska Struga, Gizdepka and Płutnica. The results showed that meteorological and hydrological parameters affect mercury speciation in river catchments, which translates into inflow of labile mercury to the southern Baltic Sea.

Distribution and bioavailability of mercury in the surface sediments of the Baltic Sea

The study aimed to determine the level of mercury (Hg) and its labile and stable forms in the surface sediments of the Baltic Sea. The work considers the impact of current and historical sources of Hg on sediment pollution, together with the influence of different environmental parameters, including water inflows from the North Sea. Surface sediments (top 5 cm) were collected in 2016-2017 at 91 stations located in different areas of the Baltic Sea, including Belt Sea, Arkona Basin, Bornholm Basin, Gdańsk Basin, West Gotland Basin, East Gotland Basin, and the Bothnian Sea. Besides, the particulate matter suspended in the surface and near-bottom water was also collected. The analysis of total Hg concentration and individual Hg forms in collected samples was carried out using a 5-step thermodesorption method. This method allows for the identification of three labile and thus biologically available, fractions of Hg, which are mercury halides, organic Hg, mercury oxide and sulphate. Two stable fractions, mercury sulphide and residual Hg, were also determined. The highest Hg concentrations, reaching 341 ng g-1, were measured in the highly industrialised Kiel Bay, which was additionally a munition dumping site during and after World War II. High Hg level, ranging from 228 to 255 ng g-1, was also recorded in the surface sediments of the Arkona Basin, which was a result of the cumulative effect of several factors, such as deposition of Hg-rich riverine matter, favourable hydrodynamic conditions and military activities in the past. The relatively elevated Hg concentrations, varying from 60 to 264 ng g-1, were found in the Gdańsk Basin, a region under strong anthropopressure and dominated by soft sediments. The sum of labile Hg in sediments was high and averaged 67% (with the domination of organic Hg compounds), which means that a large part of Hg can be released to the water column. It was found that the water inflows from the North Sea intensify the remobilisation of Hg and its transformation into bioavailable labile forms. As a consequence, the load of Hg introduced into the trophic chain can increase. Despite the significant reduction of Hg emission into the Baltic in the last decades, surface sediments can be an important secondary Hg source in the marine ecosystem. This is especially dangerous in the case of the western Baltic Sea.

Fur and faeces - Routes of mercury elimination in the Baltic grey seal (Halichoerus grypus grypus)

This study focused on evaluating the elimination of Hg by Baltic grey seals (Halichoerus grypus grypus) via faeces and pelage. In addition, we investigated the potential for ecosystem contamination via these routes. Faeces and fur were collected in 2014-2017 from captive adult grey seals and their pups. The concentrations of total mercury (THg) and methylmercury (MeHg) were measured in the samples. The amount of mercury eliminated in a labile form (the sum of the bioavailable Hg(II) and methylmercury) was also determined. An adult seal removed about 46% of mercury supplied with food via the faeces, of which only 17% was MeHg. Considering that mercury is mainly supplied to the body as MeHg, it can be assumed that mercury excreted along with faeces has undergone transformation inside the animal body. Despite the much higher THg and MeHg concentrations measured in fur, the incorporation of mercury into newly formed fur is a less effective method of Hg elimination removing just 4% of mercury entering the body via the alimentary route. The presence of mercury in lanugo is evidence of maternal transfer. First droppings of the pups were characterised by the highest content of MeHg and a low THg concentration. Then, despite the limited supply of mercury with food, and the rapid growth of the pup, the concentration of THg increased, suggesting that mercury started to be transformed into less toxic forms. It was estimated that faeces and fur expelled by seals could deliver about 800 g of mercury to the Baltic Sea. For both faeces and fur, most of the mercury (>95% for excrements and >85% for fur) was expelled in a labile form that can be quickly recycled.

Meteorological phenomenon as a key factor controlling variability of labile particulate mercury in rivers and its inflow into coastal zone of the sea

Mercury (Hg) is recognized as a global pollutant, which can be transported to the sea by suspended particulate matter (SPM) via rivers constituting the main source of mercury in the southern Baltic sea. The aim of the present study was to characterize the mercury fractions in suspended particulate matter, as well as the transformations of Hg during its riverine transportation into the sea. The thermo-desorption method was used to determine the labile and stable mercury fractions in SPM of rivers (Reda, Zagórska Struga, Gizdepka, Płutnica) within the Baltic Sea basin. In this paper six "periods" were designated (heating, non-heating, drought, rains, downpour/flood and thaws), during which the river suspended particulate matter was enriched with various fractions of mercury. Meteorological and hydrological phenomena such as downpours and thaws intensified surface runoff, causing an increase in the share of Hg_abs and Hg_ads1 mercury fractions in suspended particulate matter. Whereas, droughts contributed to the formation of HgS in a large river and to an inflow of adsorbed Hg in smaller rivers decrease of air temperature leads to increase of fossil fuel combustion and then increases the share of adsorbed Hg (mainly bound with halides) in riverine particulate matter. In the non-heating season, the main fraction was the mercury absorbed inside organic matter.

Interference-free, green microanalytical method for total mercury and methylmercury determination in biological and environmental samples using small-sized electrothermal vaporization capacitively coupled plasma microtorch optical emission spectrometry

An analytical method for the quantification of total Hg and CH₃Hg⁺ in biological tissues (fish, mushroom) and water sediment was developed based on small-sized electrothermal vaporization capacitively coupled plasma microtorch optical emission spectrometry using a low-resolution microspectrometer as detector. Sample preparation was carried out according to the procedure recommended by JRC Technical Report of European Commission for the determination of CH₃Hg⁺ in seafood and adapted by us for lower consumption of reagents. Amounts of 0.1 - 0.5 g sample were subjected to extraction in 5 ml of 47% HBr then CH₃Hg⁺ was extracted in 2 × 1 ml toluene and back-extracted in 2 ml aqueous solution of 1% l-cysteine. Total Hg/CH₃Hg⁺ were quantified in 10 μl of acidic extract/l-cysteine solution after electrothermal vaporization and measurement of 253.652 nm Hg signal in the episodic emission spectra. Under the optimal working conditions of system (70 °C sample drying, 1300 °C sample vaporization, 10 W plasma power and 150 ml min^-1 Ar flow) the limits of detection were 7.0 μg kg^-1 total Hg and 3.5 μg kg^-1 CH₃Hg⁺. Comparison of slopes in external calibration and standard addition procedure revealed the lack of non-spectral interferences of multimineral matrix, so that the calibration against Hg²⁺ standards was adopted. Pooled recovery of total mercury/methylmercury was 101 ± 7%/100 ± 7%, while precision assessed from measurements of real samples was in the range 1.6-9.6%/2.7-12.8%. The proposed method validated according to Eurachem Guide 2014 is selective and complies with demands in European legislation (Decisions 657/2002; 333/2007; 836/2011) and Association of Official Analytical Chemists Guide in terms of performances for food control. The method displays a high degree of greenness by circumventing cold vapor generation, use of small amounts of reagents and full-miniaturized instrumentation resulting in low analytical costs without reducing results quality. Besides, the method is simple and rapid, since it uses external calibration curves prepared from Hg²⁺standard solutions both for total Hg and CH₃Hg⁺ determination.

Mercury forms in the benthic food web of a temperate coastal lagoon (southern Baltic Sea)

The study was conducted in the coastal zone of the southern Baltic. The research material consisted of macrozoobenthos and elements of its diet. The samples were analysed for Hg and its labile and stable forms, using the thermodesorption method. The results showed that the level of total Hg in zoobenthos was associated with dietary preferences and the share of bioavailable Hg in its food. The Hg fractionation in the macrofauna was conditioned by biological features (morphological structure) and environmental parameters (oxygenation, pH) which shape the mobility and assimilation of Hg. The absorption of the most toxic organic Hg in macrofauna was more effective in aerobic conditions, at low primary production and with the limited inflow of organic matter. The trophic transfer of Hg was favoured by the limited biomass of primary producers, and consequently of zoobenthos. An important factor influencing the biomagnification was also the share of labile Hg in macrozoobenthos.

Forms of mercury in the Baltic mussel (Mytilus trossulus): Human and ecosystem health risk assessment

Mercury (Hg) is one of the most dangerous environmental pollutants. A significant source of this toxic element to the human body is the consumption of seafood - including the increasingly popular mussels. Mussels also play an important role in the marine ecosystem, providing a food base for fish and birds. The study aimed to determine the level of total Hg and its labile and stable forms in the Baltic mussel (Mytilus trossulus), as well as to indicate the factors that shape them. The research was conducted in the Puck Bay (Polish part of the southern Baltic Sea) in 2012-2013. The study material consisted of M. trossulus mussels, the components of their diet (suspended matter and phytoplankton), and surface sediments. Concentrations of total Hg (Hg_TOT) and the individual Hg forms were established using the thermodesorption method on a DMA-80 analyser (Milestone). The obtained results showed that the level of Hg concentration in M. trossulus from the Puck Bay was shaped by the individual features of specimens, related to the growth and reproductive cycle of mussels, as well as the quality of food consumed by them. The total share of labile Hg forms in M. trossulus was high, exceeding 90% of Hg_TOT, and the predominant form was the most dangerous organic Hg. This means that almost all of the Hg accumulated in mussels can be transferred to higher trophic levels. The obtained results showed that Baltic mussels were characterised by levels of Hg_TOT and organic Hg deemed to be safe for humans. A positive relationship was noted between the Hg_TOT concentration in a mussel's tissues and the length of its shell. Smaller sized organisms demonstrated not only by lower Hg concentrations, but also by better condition and, consequently, higher nutritional value.

The role of benthic macrofauna in the trophic transfer of mercury in a low-diversity temperate coastal ecosystem (Puck Lagoon, southern Baltic Sea)

Mercury (Hg) is a global pollutant that affects human and ecosystem health. Hg is a serious threat especially for the marine environment, in which it undergoes bioaccumulation and biomagnification, reaching elevated concentrations in fish and other seafood. The research aimed at investigating the trophodynamics of Hg in the basal links of the marine food chain: benthic macrofauna and its main food sources (i.e. suspended and sediment organic matter, micro- and macrophytobenthos). The results showed that both the amount and the origin of organic matter affected the Hg level in particular trophic groups of macrozoobenthos. The intensive inflow of terrestrial material influenced the enrichment of suspended particles and microphytobenthos in Hg, leading to increased Hg concentrations in filter-feeding macrofauna. The input of Hg-rich marine matter transported from the deeper parts of the Gulf of Gdańsk along with the near-bottom currents caused higher Hg levels in deposit feeders. The biomagnification factor (BMF) of Hg through benthic food web was dependent on environmental conditions occurring in the studied areas, in particular, factors favouring the growth and fecundity of macrofauna. Consequently, as a result of biodilution, the trophic transfer of Hg was less effective in a more productive region, despite the elevated Hg concentrations in dietary components of the macrofauna and in the surrounding environment.

Seasonal variation in accumulation of mercury in the benthic macrofauna in a temperate coastal zone (Gulf of Gdańsk)

The main source of toxic mercury (Hg) in the human body is the consumption of fish and seafood. Therefore, it is particularly important to indicate the processes that condition Hg accumulation in marine organisms, especially those in the basal links of the food chain, which are rather poorly investigated compared to top predators. The aim of the study was to determine the seasonal variability of Hg concentrations in macrozoobenthic organisms and the factors that condition it. The research was conducted in 2012-2013 in a temperate coastal zone (Gulf of Gdańsk). The obtained results showed that both Hg concentrations within one trophic level, and their seasonal variation, may differ significantly if the organisms have different feeding habits. The research also indicated that the seasonal variability of Hg level in macrozoobenthos depended on a number of both biotic factors (primary production volume, biomass and rate of fauna metabolism) and abiotic factors (salinity and ionic composition of water, Eh). The variability of Hg concentrations in macrozoobenthos during the study period was different at the research stations, which were subjected to different land influence (e.g. surface run-off, coastal erosion), and consequently differed in the quantity and quality of organic matter. The increased load of suspended particulate matter (SPM) was also an important factor influencing the increase in Hg concentration in macrozoobenthos, regardless of their trophic status. This indicates that SPM is an important source of food for zoobenthos, even in species that prefer a different feeding strategies. The obtained results also showed the role of climate changes observed in the temperate zone - in particular, the warming of the winter season - in shaping the Hg level in macrozoobenthos. The accumulation of Hg in the bottom fauna occurred most intensively in spring immediately after a long period of icing - Hg concentrations were then much higher than those measured after a mild winter, during which the ice cover persisted for a short time. The warming of the winter season and the extension of the vegetation season contributed to an increase in macrozoobenthic biomass, and consequently to the biodilution of Hg, which could have had a negative effect on the Hg load introduced into the trophic chain.

Coastal erosion-a "new" land-based source of labile mercury to the marine environment

Mercury (Hg) can be introduced into the marine environment in many different ways. In the case of the Baltic Sea, rivers and atmospheric deposition are the predominant ones. However, in the face of ongoing climate change, a new potential source, coastal erosion, is starting to become more important and is currently considered to be the third largest source of Hg in the Gdansk Basin region. It is especially significant along sections of coastline where, due to the higher frequency of extreme natural phenomena such as storms, heavy rains, and floods, increased erosion processes have already been noted. Cliffs, which account for about 20% of the Polish coastline, are particularly vulnerable. The aim of the study was to estimate the annual load of labile Hg entering the Gdansk Basin as a result of coastal erosion. Samples of down-core sediments (0-65 cm) were collected in the years 2016-2017 from selected cliffs situated in the Gulf of Gdansk area. The thermodesorption method was used to distinguish between labile and stable fractions of Hg. Considering the mean total Hg concentrations in the collected sediments (9.7 ng g^-1) and the mean share of labile (64%), bioavailable mercury, it was estimated that the load of labile Hg originating from coastal erosion entering the Gdansk Basin is 10.0 kg per year. The load can increase by up to 50% in the case of episodic abrasion events during heavy storms and rains.