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Purpose As the result of historical mining at Idrija (Slovenia), mercury (Hg) contamination in the Gulf of Trieste (northern Adriatic Sea) is still an issue of environmental concern. The element has been conveyed into the coastal area by the Isonzo/Soča River inputs of freshwater and suspended particles for centuries. This research aims to investigate the occurrence of Hg bound to the settling sediment particles (SSP) in the coastal water and to assess the sedimentary Hg fluxes. Methods Settling sediment particles were collected at four sites located in the innermost sector of the Gulf, a shallow and sheltered embayment where the accumulation of fine sediments is promoted. Six sampling campaigns were performed under different environmental conditions in terms of discharge from the Isonzo River and 12 sediment traps were installed in the upper and bottom water column for SSP collection. Settling sediment particles (SSP) were collected approximately every 2 weeks and analysed for grain size and total Hg. Results Settling sediment particles (SSP) consisted predominantly of silt (77.7 ± 10.1%), showing a concentration of Hg ranging overall between 0.61 and 6.87 µg g−1. Regarding the daily SSP fluxes, the minimum (7.05 ± 3.26 g m−2 day−1) and the maximum (92.4 ± 69.0 g m−2 day−1) values were observed under conditions of low and high river discharge, respectively. The daily Hg fluxes displayed a notable variability, up to an order of magnitude, both in the surface water layer (3.07–94.6 µg m−2 day−1) and at the bottom (11.3–245 µg m−2 day−1), reaching the maximum values following periods of high river flow. Conclusions The Isonzo River inputs of suspended particulate matter continue to convey Hg into the Gulf of Trieste, especially following river flood events, which represent one of the most relevant natural factors affecting the variations of the Hg flux in the investigated area.

The Gulf of Trieste (Northern Adriatic Sea, Italy) is the coastal area of the Mediterranean Sea most highly contaminated by mercury (Hg) due to fluvial inputs from the Isonzo/Soča River system, draining over 500 years’ worth of cinnabar extraction activity from the Idrija mining district (Western Slovenia). The aim of this research is to investigate the concentration of Hg in hair samples taken from participants from the general population from the coast of the Friuli Venezia Giulia Region (FVG), as a marker of chronic exposure to Hg.Three hundred and one individuals - 119 males and 182 females - were recruited by convenience sampling in Trieste in September 2021. An amount of approximately 100 mg of hair was collected from the occipital scalp of each participant to measure the respective Hg concentrations (expressed as mg/kg). Moreover, participants completed a self-report questionnaire collecting extensive socio-demographic and life-style information. A multiple linear regression analysis was performed to investigate the relationships among Hg concentrations in hair and several factors potentially related to an increase in the Hg content of hair.A mean Hg concentration in hair of 1.63 mg/kg was found, slightly above the 1.0 mg/kg threshold recommended by the WHO, although still well below the no observed adverse effects level (NOAEL) of 10 mg/kg. Among respondents, 55.6% showed a Hg concentration in hair > 1 mg/kg, 22.9% > 2 mg/kg and 2 participants exhibited Hg levels >10 mg/kg. Factors associated with higher concentrations of Hg in hair were male sex, ingestion of > 4 servings of fish per month and preferred consumption of small/medium size fish or shell/crayfish/molluscs. Conversely, ingestion of frozen fish represents a protective factor.Though a risk alert for Hg exposure for coastal residents from FVG is deemed unnecessary at this time, it is recommended that pregnant women limit their ingestion of locally caught fish to < 4 servings/month.

The Gulf of Trieste (Northern Adriatic Sea, Italy) is the coastal area of the Mediterranean Sea most highly contaminated by mercury (Hg) due to fluvial inputs from the Isonzo/Soča River system, draining over 500 years’ worth of cinnabar extraction activity from the Idrija mining district (Western Slovenia). The aim of this research is to investigate the concentration of Hg in hair samples taken from the general population of the Friuli Venezia Giulia (FVG) Region coastal area, as a marker of chronic exposure to Hg. Three hundred and one individuals — 119 males and 182 females — were recruited by convenience sampling in Trieste in September 2021. An amount of approximately 100 mg of hair was collected from the occipital scalp of each participant to measure the respective Hg concentrations (expressed as mg/kg). Moreover, participants completed a self-report questionnaire collecting extensive socio-demographic and life-style information. A multiple linear regression analysis was employed to investigate factors associated with increased levels of Hg concentration in hair. A mean Hg concentration in hair of 1.63 mg/kg was found, slightly above the 1.0 mg/kg threshold recommended by the WHO for pregnant women and children, although still well below the no observed adverse effects level (NOAEL) of 10 mg/kg. Among respondents, 55.6% showed a Hg concentration in hair > 1 mg/kg, 22.9% > 2 mg/kg, and 2 participants exhibited Hg levels > 10 mg/kg. The adjusted mean hair Hg level increased in those subjects who reported a preference for shellfish/crayfish/mollusks (RC = 0.35; 95%CI: 0.16; 0.55), whereas it decreased in those who reported a preference for frozen fish (RC = -0.23; 95%CI: − 0.39; − 0.06). Though a risk alert for Hg exposure for coastal residents from FVG is deemed unnecessary at this time, it is recommended that pregnant women limit their ingestion of locally caught fish to < 4 servings/month.

The Cananéia-Iguape estuarine–lagoon complex (São Paulo state, Brazil) is a natural laboratory to study metal binding by humic substances (HS) in subtropical settings. This transitional environment is evolving into a freshwater environment due to water input from the Ribeira River, funneled through the Valo Grande Canal (Iguape). Past mining activities in the Ribeira River basin and maritime traffic are suspected to be potential sources of trace metals in the system. In this study, the trace metal contents of Free Humic Acids (FHA), Bound Humic Acids (BHA), and Fulvic Acids (FA) extracted from sedimentary organic matter were investigated. Moreover, the sources of HS were traced using their stable carbon isotope compositions and C/N ratios. The results suggested a mixed marine–terrestrial source of FHA, BHA, and FA. Copper and Cr were the most abundant trace metals bound to HS. On average, Cu showed concentrations of 176, 115, and 37.9 μg g−1 in FHA, BHA, and FA, respectively, whereas Cr showed average concentrations of 47.4, 86.3, and 43.9 μg g−1 in FHA, BHA, and FA, respectively. Marine FHA showed the highest binding capacity for trace metals, whereas terrestrial FA derived from the decay of mangrove organic matter showed the lowest binding capacity.

Health and safety of occupations entailing extensive skin contact with cinnabar-enriched sand in beaches of Friuli-Venezia Giulia (FVG) Region (North-eastern Italy) have been questioned for possible skin absorption of mercury (Hg). One hundred mg hair was collected from the occipital scalp of 50 male workers of Grado beach and 121 males from FVG general population. Factors associated with hair Hg content were investigated by multivariable logistic (considering Hg levels >1 vs ≤1 mg/kg) and log-transformed linear regression. The median hair concentration of Hg in male beach workers was 0.70 (IQR = 0.42; 1.34) mg/kg, lower than FVG general population's [1.29 (IQR = 0.87-2.06) mg/kg (p

Mercury (Hg) in aquatic environments accumulates in sediments in several chemical forms, both inorganic and organic, which are often determined through time-consuming selective and sequential extraction procedures. Thermal desorption technique (pyrolysis) coupled with continuous determination by atomic absorption spectrometry (AAS) may be an easy-to-use alternative technique for the rapid identification and quantification of Hg species in the solid matrix. This technique is based on the gradual heating of a sample that releases Hg at different temperature intervals depending on its chemical form. Thus, a single Hg species that desorbs at a specific temperature may be identified via a thermogram of the sample. In this work, several commercial pure Hg compounds, natural Hg mineral species (red cinnabar, α-HgS) and one compound synthesised in the lab (α-FeOOH–––Hg) were mixed with synthetic calcium carbonate (CaCO3), silica (SiO2) and natural matrices (silicate and carbonate marine sediments) which were then desorbed in order to determine the desorption peak temperatures corresponding to each Hg species. Moreover, possible interference caused by the matrix was also considered. The results obtained from 52 desorbed MIX samples displayed different desorption temperatures for the same Hg species depending on the matrix used. Indeed, Hg species mixed with synthetic SiO2 desorbed at a temperature lower than the same species mixed with synthetic CaCO3 with a difference of approximately 100 ◦C. The analytical approach was applied to selected coastal sediments from the Gulf of Trieste (Northern Adriatic Sea, Italy), contaminated by Hg from the five centuries of cinnabar (α-HgS) mining activity from Idrija (Slovenia), in order to identify the unknown Hg species. The results revealed the presence of two peaks with a distinct temperature of desorption (~250 and 350 ◦C). The highest temperature corresponds to the mostly refractory red cinnabar (α-HgS) compound, whereas the lowest temperature is related to other species (e.g. β-HgS) that may also include Hg associated with more mobile and potentially bio-accessible species (e.g. α-FeOOH–––Hg) if compared to α-HgS. This methodological approach is a rapid and cost-effective technique useful to preliminarily quantify more stable Hg species (mainly α-HgS), underlining the relevance in considering the chemical form of the element rather than merely the total concentration for simplifying the environmental management of Hg-contaminated sediments.

The long term vertical and horizontal mobility of mercury (Hg) in soils of agricultural areas of a historically contaminated Italian National Relevance Site (SIN Brescia-Caffaro) was investigated. The contamination resulted from the continuous discharge of Hg in irrigation waters by an industrial plant (Caffaro S.p.A), equipped with a mercury-cell chlor-alkali process. The contamination levels with depth ranged from about 20 mg/kg dry weight (d.w.) of soil in the top (plow) layer to less than 0.1 mg/kg d.w. at 1 m depth. The concentrations varied also spatially, up to one order of magnitude within the same field and showing a decreasing trend from the Hg source (i.e., irrigation ditches). The concentration profiles and gradients measured were explained considering Hg loading, soil properties, such as the texture, organic carbon content, pH and cation exchange capacity. A Selective Sequential Extraction (SSE) was also applied on soil samples from an ad hoc greenhouse experiment to investigate the role of different plant species in influencing Hg speciation in soils. Although most of the extracted Hg was included in scarcely mobile or immobile forms, some plant species (i.e., alfalfa) showed to importantly increase the soluble and exchangeable fractions with respect to the unplanted control soils, thus affecting mobility and potential bioavailability of Hg.

The sediments in the Gulf of Trieste (northern Adriatic Sea, Italy) are contaminated by mercury (Hg) due to historic mining which took place in Idrija (Slovenia). Despite many studies having been done regarding Hg, no information is available on the potential impact of dredging required along the main channel approaching the Port of Monfalcone. Sixteen surface sediment samples were collected along the channel to determine both total Hg concentration and chemical species using the thermo-desorption (TD) technique. Six samples were also chosen to apply a selective sequential extraction (SSE). The TD technique showed the maximum Hg release approximately at 260 and 335°C, corresponding to metacinnabar (β-HgS) and cinnabar (α-HgS), respectively. The SSE demonstrated that Hg was mainly associated with poorly soluble or insoluble compounds (98.7%). A resuspension event over a limited period of time can be considered of negligible impact to the water column due to the scarce Hg mobility from sediments.

Mercury (Hg) contamination in the Gulf of Trieste (northern Adriatic Sea) due to mining activity in Idrija (Slovenia) still represents an issue of environmental concern. The Isonzo/Soča River’s freshwater inputs have been identified as the main source of Hg into the Gulf, especially following periods of medium-high discharge. This research aims to evaluate the occurrence and distribution of dissolved (DHg) and particulate (PHg) Hg along the water column in the northernmost sector of the Gulf, a shallow and sheltered embayment suitable for the accumulation of fine sediments. Sediment and water samples were collected under unperturbed and perturbed environmental conditions induced by natural and anthropogenic factors. Mercury in the sediments (0.77–6.39 µg g−1) and its relationship to grain size were found to be consistent with previous research focused on the entire Gulf, testifying to the common origin of the sediment. Results showed a notable variability of DHg (&lt, LOD–149 ng L−1) and PHg (0.39–12.5 ng L−1) depending on the interaction between riverine and marine hydrological conditions. Mercury was found to be mainly partitioned in the suspended particles, especially following periods of high discharge, thus confirming the crucial role of the river inputs in regulating PHg distribution in the Gulf.

The accumulation of contaminants and their potential mobility represent two of the main environmental issues facing coastal environments. Sediments often act as “reservoirs” of contaminants, including potentially toxic trace elements, but they can also be considered a secondary source of contamination due to remobilisation processes at the sediment-water interface which may affect the quality of the coastal water and aquatic biota. This research aims to provide a geochemical characterisation of the estuarine system of the Timavo/Reka River, focusing on the occurrence of trace elements in different environmental matrices with the purpose of highlighting potential critical conditions in terms of environmental quality. The surface sediments were found to be enriched in several trace elements especially in the innermost sector of the area. There, sulphate-reductive conditions in the bottom saltwater testify to potential anoxia at the sediment-water interface, driving trace element accumulation in the residual fraction of the sediments. However, Fe and Mn redox behaviour appears to play a crucial role in the recycling of dissolved trace elements in the water column. With the lone exception of the saltwater in the innermost sector, trace elements were found to be mainly associated with suspended particles due to oxidation and precipitation processes, whereas a common lithogenic origin was identified for Cr, Ni, and Co, which are significantly correlated both in the surface sediments and in the suspended particles.

Estuaries are unique water systems and represent a vital link between land and sea. River transported contaminants, among which trace elements are of major concern, are subjected to a variety of physical, chemical and biogeochemical processes in the estuarine mixing zone. The Isonzo/Soča River is the main source of freshwater into the Gulf of Trieste (northern Adriatic Sea) and is known as the primary source of Hg due to long-term cinnabar (HgS) extraction from the Idrija mining district (Slovenia). Mercury distribution, cycling and speciation have been intensively studied at the Isonzo/Soča River mouth. Still, little information is currently available regarding other trace elements (As, Co, Cu, Cs, Cr, Fe, Ni, Mn, Pb and Zn). Indeed, this research aims to evaluate trace element occurrence and partitioning behaviour among suspended particulate matter (> 0.45 μm), colloidal material (0.45 μm – 10 kDa) and the truly dissolved fraction (< 10 kDa) at the mouth of the Isonzo/Soča River. Generally, trace elements are mainly associated with suspended particulate matter, which represents their main effective vehicle to coastal environments. In addition, dilution effects between riverine and marine particles are responsible for the decrease in particulate trace element concentrations along the water column. Mercury was notably present in winter in the freshwater, as expected under conditions of high river discharge. As opposed to other trace elements, particulate Mn was found to be high in the marine water, particularly in summer when high water temperatures could promote oxidation and precipitation processes. The Isonzo/Soča River mouth is characterised by a strong salinity gradient and geochemical processes appear to affect trace element partitioning behaviour. In this context, Fe, Mn and Cu were found to be mainly associated with the suspended particles and displayed the highest concentration in the colloidal material. Conversely, the truly dissolved fraction prevailed for As and Cs, which are often present in ionic dissolved forms in natural water systems.

The Marano and Grado Lagoon (northern Adriatic Sea, Italy) is contaminated mainly by mercury (Hg) of mining and industrial origin. This work aims to investigate the sedimentary records of Hg of a tidal flat–saltmarsh (TF–S) system and to understand the role played by tidal fluxes in terms of the transport, accumulation and release of Hg due to the periodic flow of the tide. The complex history of the sources of Hg in the area of the TF–S system has resulted in several fluctuations of Hg in sediments over time; due to its higher sedimentation rate (1.3 cm year−1) than the subtidal areas of the Grado lagoon, the outer area of the TF–S system is more active in terms of accumulation (from 56 to 81 mg m−2 year−1) than the inner area. Fluxes were estimated at the mouth of a principal tidal creek by combining discrete hourly tidal flow measurements with weighed measurements of dissolved (DHg) and particulate (PHg) mercury obtained via water sample collection. Mercury, mainly in particulate form, is drained by the tidal creek from the marsh during a tidal semi-cycle. The highest flux of PHg was recorded during ebb tide in July (1071 mg). The calculation of the quantitative flows of PHg and DHg highlighted a tendency for Hg to be exported from the TF–S to the lagoon channel during a tidal semi-cycle. However, the results obtained here for the Hg fluxes do not allow for the depiction of a constant positive or negative budget as that found in the literature for macro-scale budget calculations at lagoon tidal inlets. A possible explanation for there being no constant trend in the PHg and DHg budget is that our TF–S system is located in a lagoon area where previous findings reported accretion or a balance situation between erosion and sedimentation processes.

There is a growing concern about the mercury (Hg) vented from submarine hydrothermal fluids to the marine surrounding and exchange of dissolved gaseous mercury (DGM) between the sea surface and the atmosphere. A geochemical survey of thermal waters collected from submarine vents at Panarea Island (Aeolian Islands, southern Italy) was carried out in 2015 (15–17th June and 17–18th November), in order to investigate the concentration of Hg species in hydrothermal fluids and the vertical distribution in the overlying water column close to the submarine exhalative area. Specific sampling methods were employed by Scuba divers at five submarine vents located along the main regional tectonic lines. The analysis of the hydrothermal fluids indicates a site-to-site variation, with filtered total mercury (FTHg) concentrations ranging from 1072 to 4711 pM, as a consequence of the gas bubbles partial dissolution. These results are three orders of magnitude higher than the FTHg concentrations found in the overlying seawater column (ranging from 5.3 to 6.3 pM in the mid waters), where the efficient currents and vertical mixing result in more dilution, and potentially rapid transfer of the dissolved gaseous Hg to the atmosphere. Dissolved gaseous mercury (DGM) and gaseous elemental mercury (GEM) were simultaneously measured and combined in a gas-exchange model to calculate the sea-air Hg 0 evasional flux. Based on the data of DGM (range: 0.05–0.22 pM) and atmospheric GEM (range: 1.7 ± 0.35–6.4 ± 2.6 ng m − 3 ), we argue that the surface seawater off Panarea is mostly supersaturated in dissolved elemental gaseous mercury compared to the atmosphere, with a sea-air Hg 0 net flux ranging from 0.7 to 9.1 ng m − 2 h − 1 (average: ~ 4.5 ± 3.5 ng m − 2 h − 1 ). Since the empirical gas-exchange model does not include the contribution of Hg 0 released as gas bubbles rising from the vents toward sea-surface, the calculated Hg 0 evasional flux for this location is most likely larger.

Purpose Previous research conducted in the Marano and Grado lagoon (northern Adriatic Sea) has shown that this environment has been affected by trace metal contamination, especially by mercury (Hg), from both industrial (the chlor-alkali plant) and mining activities (Idrija mine, Slovenia). Sediment cores were collected from two different saltmarshes of this lagoon environment to evaluate the degree of the anthropogenic enrichments and the geochronology of Hg accumulation. Materials and methods Core subsampling was performed by cutting 1-cm thick slices at discrete intervals. Mercury determination was done differently from the other parameters in that the two long cores were subsampled at 1-cm intervals to obtain continuous concentration profiles. Samples were completely decomposed, using a mixture of mineral acids in a closed microwave system before being analysed for trace metal content using ICP-OES. Total Hg content in the solid phase was determined by DMA-80. Cs-137 was measured via gamma spectrometry. Pb-210 activity was measured via alpha-counting of its daughter, Po-210, assuming secular equilibrium between the two isotopes. Results and discussion In saltmarsh sediments, Fe, Co, Li, Sc and V show no enrichment at both sites thus suggesting that they are essentially lithogenic elements. Conversely, enrichments are minimal (EF = < 2) for As, Cd, Cr, Ni, Pb and Zn and moderate (EF = 2-5) for Cu and Mn and also for Pb and Zn but only in some levels of the sedimentary sequences. An exception is Hg, as expected due to the long-term input proceeding from the historical mining activity which has especially affected the eastern sector of the lagoon. Conclusions The core collected from the saltmarsh in the eastern lagoon (Grado) displays a better time resolution during the last century although the Hg background level has not been reached. Conversely, the core collected in the western sector (Marano) has recorded a longer and more complete history of Hg contamination, from the beginning of the peak of Hg extraction activity at the Idrija mine (1850). Both saltmarshes still receive Hg inputs and the sediment accumulation rates in the upper section appear to have increased over the last 10-20 years (from 0.30 to 0.45 cm year(-1) atMarano and from 0.30 to 0.74 cm year(-1) at Grado). Many of these morphological structures suffer erosive processes thus representing a potential source of contaminants associated with sediments, in particular Hg. Conservation and monitoring of saltmarshes should be taken into consideration also from this environmental point of view.

Dissolved gaseous mercury (DGM) production was examined in relation to ultraviolet radiation within a marine aquaculture site in the contaminated Marano and Grado Lagoon (Italy). The measured rates of DGM production relative to time elapsed (17.06 and 20.68 pg h−1, respectively) were substantially (6–20 times) higher than what has been observed in other marine Hg studies. We measured similar levels of DGM relative to dissolved total mercury (THgD) (0.84%–8.91%) at these sites in comparison to uncontaminated marine sites, however relative to other moderately-contaminated marine sites in Portugal the % DGM/THgD was high. These results suggest a substantial capacity for Hg volatilization from these highly contaminated lagoons to the atmosphere due to photoreduction mechanisms.

Butyltin compound (BTC) contamination was evaluated in two north Adriatic marinas, San Rocco (Italy) and Lucija (Slovenia). BTC sedimentary concentrations (121 ± 46 and 352 ± 30 ng Sn g-1 in San Rocco and Lucija, respectively) evidenced the past use of antifouling paints, confirmed by the reduced tributyltin content (~ 46%) with respect to the sum of BTC. Elemental and organic carbon isotopic (δ13C) analyses of bulk sediments and its lipid and humic substances were performed in order to evaluate their role in BTC partitioning and preservation. The δ13C of sedimentary bulk and refractory organic matter suggested that diagenetic processes could play a role in the preservation or release of pollutants. No contamination was found in water collected from the benthic chamber and thus, fluxes at the sediment-water interface were not assessed, except for MBT efflux at Lucija (28.9 ng Sn m-2 day-1). Nevertheless, BTC concentrations in porewaters (up to 75 ng Sn l-1) and rather low sediment-porewater partitioning coefficients (Kd) with respect to the data reported in the literature would suggest a potential risk of the reintroduction of BTC into the water column at both sites: at Lucija, sedimentary contamination is high despite the greater Log Kd, whilst at San Rocco, the low BTC concentration is associated with a reduced sediment affinity.

Estuarine sediments must be dredged to allow for navigation, and where these sediments are placed after dredging depends upon guidelines based only on the total concentration of contaminants. However, resuspension events could seriously affect the mobility and speciation of contaminants, including potentially toxic trace elements stored in sediments. The effects of resuspension on the cycling of mercury (Hg) and arsenic (As) between the sediment and water column was investigated in a mesocosm study. Four experiments were conducted in three estuaries in northern Spain based on samples collected from sites which have been impacted by decommissioned Hg and As mines and periodically subjected to dredging activities. Designed to mimic the resuspension of particles, each of the experiments revealed that the release of Hg and As species does not only depend on the total concentration in the sediments (16.3–50.9 mg kg−1, for As and 0.52–5.01 mg kg−1 for Hg). The contribution from porewaters and the subsequent reductive dissolution and/or desorption appear to be the main processes responsible for the abrupt increase in dissolved Hg and As species (maximum release of 427% and 125%, respectively). In some cases, As and Hg continued to remain at high concentrations in the water column even after the experiments were completed, thus testifying to their critical persistence in the dissolved form. Conversely, at the other sites, the restoration of pre-resuspension conditions was observed only a few hours after resuspension, mainly due to the role of Fe oxy-hydroxides which provides suitable surfaces for adsorption and/or co-precipitation involving dissolved Hg (maximum removal of −58%) and As (maximum removal of −25%) species. The results of this research could be helpful to take appropriate decisions regarding dredging especially at the Nalon estuary, where the release of dissolved As(V) and MeHg appeared to be favoured by sediment resuspension.

A crucial step towards developing a more complete understanding of mercury (Hg) biogeochemical cycling in coastal environments is the measurement of the fluxes of gaseous elemental mercury (GEM), at the water-air interface (W-A interface). A floating flux chamber coupled with a real-time atomic adsorption spectrometer (Lumex-RA 915M) was applied to measure GEM concentrations, and to estimate the diurnal evasion flux at the W-A interface during three seasonal campaigns at four selected sites: two in a lagoon-based fish farm, one in an open lagoon environment highly impacted by long-term activities from the Idrija mercury mine (Slovenia), and an uncontaminated area of the Gulf of Trieste, the Bay of Piran (Slovenia). In this study, the regional background concentration measured at the uncontaminated site of atmospheric GEM (from 1.60 ± 0.95 to 2.87 ± 1.52 ng m−3) was determined. GEM fluxes at the W-A interface were found to be significantly higher during the summer (from 51.2 ± 8.8 ng m−2 h−1 to 79.9 ± 11.4 ng m−2 h−1) and correlated to incident solar radiation and water temperature. This finding confirms the importance of these two parameters in the photoreduction and biotic reduction of Hg2+ to dissolved gaseous mercury (DGM), which is volatile and easily released to the atmosphere in the form of GEM. These new insights will be of help for future estimates of Hg mass balance in one of the most contaminated areas in the Adriatic Sea.

Sediments of the Nalón estuary (Cantabrian Sea, Spain) are important repositories of mercury as a direct consequence of the runoffs from the historical Hg mining activity developed in the Nalón river basin. Previous studies have shown that sediment acts as secondary source of Hg species to the overlying water column in natural conditions. However, evidence for the effects of resuspension on the dynamics of Hg species is still lacking. The effect of resuspension on the cycling of inorganic mercury (IHg) and methylmercury (MeHg) between the sediment and water column was investigated in a mesocosm study. Two experiments were conducted in July 2017 based on unaltered material collected from sites heavily impacted by Hg and periodically subjected to dredging activities. Designed to mimic the resuspension of particles, both experiments revealed that the release of Hg species from the solid to the dissolved phase became negligible quickly after the event. MeHg values did not change according to total dissolved mercury (THg), suggesting that the enhancement of methylation processes may occur during this processes. The results reported in this research may be useful for the local fishing activities and environmental management, as well as for planning dredging activities on the area in order to decrease potential impacts on the aquatic environment.

One of the main environmental issues affecting coastal marine environments is the accumulation of contaminants in sediments and their potential mobility. In situ benthic chamber experiments were conducted at two tourist ports (marinas) located in the Gulf of Trieste, one in Slovenia and one in Italy. The aim was to understand if and where recycling at the sediment-water interface (SWI) may affect metal(loid)s. Short sediment cores were also collected near the chamber to investigate the solid (sediments) and dissolved phases (porewaters). Both diffusive and benthic fluxes were estimated to elucidate the release of metal(loid)s at the SWI. Total element concentrations and their labile fractions were determined in sediments to quantify their potential mobility. The total element contents were found to be two orders of magnitude higher in the Italian marina than in the Slovenian one, especially for Hg (up to 1000 mg kg−1), whereas the labile fraction was scarce or null. The opposite occurred in the Slovenian marina. Metal(loid)s in porewaters showed a clear diagenetic sequence and a close dependence upon the suboxic/anoxic conditions of sediments. The results suggest that although the sediments of the Italian marina exhibit the highest total metal(loid) concentration, these elements are scarcely remobilisable. Conversely, in the Slovenian marina, sediments seem to be comparatively more prone to release metal(loid)s at the SWI.

Saltmarshes are important constituents of marine-coastal transitional environments that provide several services to the ecosystem. Due to anthropogenic activities, several contaminants are increasingly introduced into these environments where are disperse and can accumulate in the saltmarsh sediments. The Marano and Grado Lagoon (northern Adriatic Sea) is affected by Hg contamination, which mainly coming from historical regional mining activities (Idrija, western Slovenia) and, subordinately, from more recent industrial input due to a chlor-alkali plant. Several studies have also demonstrated the Hg contamination of saltmarsh sediments and halophyte vegetation that cover them. Moreover, saltmarshes not only trap contaminated sediments, but can act as a secondary source of contamination. This work aims at determining the potential role of the tidal flat-saltmarsh (TF-S) system as a sink or secondary source of Hg in this coastal lagoon in relation to the chemical-physical processes leading their remobilisation. The main objective was to understand the role played by periodic flow of tide in a TF-S pilot site in terms of transport, accumulation and release of Hg. Tidal flows and water chemistry were measured at the mouth of a principal tidal creek which collect the waters of a dense channel network draining a 5.5-ha tidal flat-saltmarsh system. Tidal fluxes were estimated by combining discrete hourly tidal flow measurements with weighted measurements of particulate (PHg) and dissolved (DHg) mercury obtained by water samples. The highest values of DHg and PHg were recorded during ebb tide and the quantitative fluxes estimated for all parameters highlighted a tendency for metal to be exported from the TF-S system due to the tidal flows in ebb tide conditions. The results obtained for the PHg fluxes, in particular, are in agreement with those observed on a macro-scale at one of the lagoon tidal inlets considering an annual mass-balance of PHg performed via several water column sampling campaigns. A simple estimation provides a negative sedimentary budget for the TF-S system, which loses PHg towards the main lagoon channel during a tidal semi-cycle thus confirming other evidence of serious morphological deterioration of this critical coastal environment.

The potential impact of decommissioned mining areas on the quality of water resources is an issue of major concern for local communities. Acid mine drainage resulting from hydrolysis and oxidation of metal sulphides associated with mineral veins or mining wastes is often responsible for leaching large amounts of potentially harmful elements (PHEs) in solution, which can be dispersed into the surrounding environment and affect the quality of the recipient water bodies. The aim of the present study was to investigate the geochemical properties of the mine drainage waters at the decommissioned Salafossa mine (North-Eastern Italian Alps), to highlight anomalous concentrations of PHEs outflowing from the currently flooded galleries and to elucidate their speciation. In spite of the Zn-Pb sulphides still present in the body ore, there is no evidence of acid drainage waters from the mine galleries as a result of the buffering effect produced by carbonate host rocks. Due to their high mobility, however, Zn and Tl are present in solution mostly in ionic form. Conversely, the less mobile Pb, is preferably partitioned in the solid phase. Additionally, the oxidising conditions of the drainage waters also allow the precipitation of some PHEs (As, Cd, Pb, Tl, Zn) in the form of Fe-Mn oxy-hydroxides and carbonates, which accumulate at the bottom of the mine galleries as fine “sediments” or concretions. Drainage waters inside the mine were found to be highly enriched in Zn (up to 16 mg L‐1), Fe (up to 5 mg L‐1) and Tl (up to 260 μg L‐1). Their concentrations, however, are partially diluted in the mine due to a mixing with less mineralised waters before being discharged into the Piave River, the major tributary downstream from the mining area. Although drainage waters are still characterised by high concentrations of Tl (about 30 μg L‐1) at their outflow, dilution in the Piave River seems to be the only natural process mitigating the impact of PHEs within the drainage basin.

Metabolism and carbon, oxygen, and nutrient fluxes (DIC, DOC, DO2, NO2−, NO3−, NH4+, PO43− and SiO44−) were studied during three surveys at two sites (VN1 and VN3) located at a fish farm at the Marano and Grado Lagoon (northern Adriatic Sea), using an in situ benthic chamber. Field experiments were conducted in July and October 2015 and March 2016 at a depth of approximately 2 m along the main channels of the fish farm. Water samples were collected by a scuba diver every 2 h in order to investigate daily fluxes of solutes across the sediment-water interface (SWI). Regarding the solid phase, Corg/Ntot and Corg/Porg molar ratios suggested an autochthonous marine origin of the organic matter and a minor preservation of P in the sediments, respectively; high values of sulphur (Stot) were also encountered (0.8–2%). The conditions at VN3 were mostly anoxic with high NH4+ levels (30–1027 μM) and the absence of NO3−. Substantial daily patterns of all solutes occurred especially in autumn and winter. On the contrary, fluxes at VN1 were less pronounced. Usually, inverse correlations appeared between dissolved O2 and DIC trends, but in our system this was observed only at VN3 in autumn and accomplished by a parallel increase in NH4+, PO43− and SiO44− during intense nutrient regeneration. These results are significantly different than those reported for open lagoon environments, where nutrient regeneration at the SWI and in surface sediments is the primary source of nutrients available for assimilation processes, especially during the warmer period of the year when the natural nutrient input by fresh water inflows is limited. Due to the importance of this site for aquaculture, biodiversity and ecosystem services, useful suggestions have been provided from this study in order to improve the quality of this unique aquatic system.

Among pollutants widespread in the environment, mercury (Hg) is well recognised for its toxicity, mobility and bioaccumulation potential. In coastal areas the presence of this element generates conflicts with important resources of profitable value such as fisheries and aquaculture. The Marano and Grado Lagoon (Adriatic Sea) experienced a double Hg impact. The first is due to the mining activity conducted at Idrija (western Slovenia) for approximately 500 years, whereas the second is the result of discharge of a chlor-alkali plant effluents. Fish farming is a historical activity covering 14% of the total lagoon area. Recently, one fish farm was long-term monitored in order to understand the role of the sediment-water interface in recycling Hg and to estimate benthic fluxes and Hg mobility in the water column. An important further step toward a better comprehension of the Hg biogeochemical cycling in the lagoon environment, is represented by the estimate of its evasional fluxes, as gaseous elemental mercury (GEM), at the water-air interface. A dynamic flux chamber coupled with a real-time atomic adsorption spectrometer (Lumex-RA 915+) has been used to measure GEM and to estimate the diurnal evasion flux at the water-air interface during three seasonal campaigns in four selected sites: two in a lagoon fish farm, one in the open lagoon environment highly impacted by Hg mining activities and the last one in an uncontaminated area of the Gulf of Trieste, the Bay of Piran (Slovenia). Accomplished to these measurements the regional background level of atmospheric GEM was determined together with the main chemico-physical parameters influencing Hg behaviour. This new insights will be of help for future estimates of Hg mass balance in one of the most contaminated areas in the Adriatic Sea.

The Marano and Grado Lagoon is well known for being contaminated by mercury (Hg) from the Idrija mine (Slovenia) and the decommissioned chlor-alkali plant of Torviscosa (Italy). Experimental activities were conducted in a local fish farm to understand Hg cycling at the sediment–water interface. Both diffusive and benthic fluxes were estimated in terms of chemical and physical features. Mercury concentration in sediments (up to 6.81 μg/g) showed a slight variability with depth, whereas the highest methylmercury (MeHg) values (up to 10 ng/g) were detected in the first centimetres. MeHg seems to be produced and stored in the 2–3 cm below the sediment–water interface, where sulphate reducing bacteria activity occurs and hypoxic–anoxic conditions become persistent for days. DMeHg in porewaters varied seasonally (from 0.1 and 17% of dissolved Hg (DHg)) with the highest concentrations in summer. DHg diffusive effluxes higher (up to 444 ng/m 2 /day) than those reported in the open lagoon (~ 95 ng/m 2 /day), whereas DMeHg showed influxes in the fish farm (up to − 156 ng/m 2 /day). The diurnal DHg and DMeHg benthic fluxes were found to be higher than the highest summer values previously reported for the natural lagoon environment. Bottom sediments, especially in anoxic conditions, seem to be a significant source of MeHg in the water column where it eventually accumulates. However, net fluxes considering the daily trend of DHg and DMeHg, indicated possible DMeHg degradation processes. Enhancing water dynamics in the fish farm could mitigate environmental conditions suitable for Hg methylation.

Mercury (Hg) distribution in saltmarsh sediments and in three selected halophytes (Limonium narbonense, Sarcocornia fruticosa and Atriplex portulacoides) of a wetland system (Marano and Grado Lagoon, Italy) following a contamination gradient in sediments was investigated. The Hg uptake was evaluated at the root system level by calculating the enrichment factor (EF) and in the aboveground tissues by means of the translocation factor (TF). The related methylmercury (MeHg) concentrations in the halophytes were also investigated with regard to the location of the sites and their degree of contamination. Hg concentration in halophytes seemed poorly correlated both with the total Hg in rhizo-sediments and with the specific plant considered, supporting the evidence that the chemico-physical parameters of sediments could significantly affect metal availability for plants. Hg concentrations in roots increased with depth and were 20-fold higher than content measured in related rhizo-sediments (high EF). A low content of Hg is translocated in aboveground tissues (very low TF values), thus highlighting a kind of avoidance strategy of these halophytes against Hg toxicity. MeHg values were comparable between the two sites and among species, but the translocation from below- to aboveground plant tissues was more active.

The mineral body exploited in Salafossa (Eastern Dolomites) was one of the largest lead/zinc-containing mineral deposits in Europe. Both metals were mainly present as sulphides ( sphalerite , ZnS and galena , PbS). Mining activity started around 1550, but it was only around 1960 that the richest veins of the minerals were discovered. The mine closed in 1985, and concentrations of several trace metals, such as thallium (Tl), iron (Fe), manganese (Mn), lead (Pb) and zinc (Zn), were detected in the soils and plant samples ( Biscutella laevigata L.) that were collected from eighteen sites selected outside the mine. B. laevigata is a pseudometallophyta species, and it often grows near mining areas where the soil's metal concentrations are significantly higher than those of soil with a natural geochemical background. The total metal concentrations in the plant tissue (roots and leaves of Biscutella laevigata ) and in the soil samples – both bulk-soil and the B. laevigata root system (rhizo-soil) – were determined through Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The metal extractability and leachability of the soil samples were estimated using soil extractions with DTPA (Diethylenetriaminepentaacetic acid). In addition, metal mobility caused by rainwater runoff was estimated by using a leaching test with a dilute solution of H 2 SO 4 and HNO 3 . The results showed that metals were present in a chemical form available for uptake by the plants' roots. In fact, high concentrations of the metals were also found in the plant tissue (roots and leaves) of B. laevigata , and these concentrations were higher than those whose soils present natural geochemical background levels in the corresponding rhizo-soil. Thus, B. laevigata has shown a marked ability to bioaccumulate trace metals, especially Tl and, to a lesser extent, Zn, Pb, Fe and Mn, and it can influence metal mobility in the rhizo-soil. To assess the uptake and translocation processes of the trace metals, resulting in their bioaccumulation, two different indices were calculated: the enrichment factor in roots (EFr), as the ratio between the metal concentration in belowground biomass and in the respective rhizo-soil, and the translocation factor (TF), as the ratio between the metal concentration in the leaves and the corresponding roots. For both indices, values > 1 denoted enrichment of the metal in the roots or its translocation to the upper tissues. The results showed that EFr and TF were considerably high only for Tl, reaching a maximum value of 60 for EFr and 11.6 for TF. Conversely, the other investigated metals did not show significant bioaccumulation (EFr 1 only at a few sites.

Purpose The Marano and Grado Lagoon (Italy) has been affected by trace metal(oid) contamination in the last century, especially mercury, from both industrial and long-termmining activities. The uptake and distribution of trace metal(oid)s in halophytes were determined in two selected salt marshes. To evaluate the potential activity of plants as phytoremediation, the bioconcentration and translocation factors (BCF and TF, respectively) were calculated. Materials and methods In both salt marshes, individuals of Sarcocornia fruticosa L. and Limonium vulgare L., two of the most abundant halophytes in this environment, were sampled. The aboveground biomass (stems and leaves) was collected and sealed in plastic bags. Once the stems were removed, the belowground biomass and the attached rhizosediment were sampled using a single gouge auger sampler. The sediment cores obtained were sectioned on field to a maximum depth of 15 cm. The roots were carefully separated from the rhizo-sediment in the laboratory. The sediment, roots, leaves, and stems were freeze-dried, finely ground, and homogenized. Samples were totally decomposed, using a mixture of mineral acids in a closed microwave system, and analyzed for trace metal(oid) content by ICP-AES. The total Hg content in the solid phase was determined by DMA-80. Results and discussion Metal(oid) concentrations in roots were usually up to one or two orders of agnitude higher than in stems and leaves. The exceptions are Cd and Ni, which levels were not detectable, and Cr in stems of both halophytes where the concentration reached up to four times more than in roots. Commonly, trace metal(oid) contents were higher in stems than in leaves, except for Zn. Considering all BCF data, a sequence of metal(oid)s preferentially transferred from sediment to belowground biomass of the two plants is Cd > Mn > As > Pb. This sequence does not coincide for the two salt marshes, except for Cd, probably due to the different source of metal(oid)s in sediments and/or some site-specific lithogenic properties.Metal(oid)s accumulated from rhizo-sediment were largely retained in roots as shown by TF values

One of the main environmental issues affecting the coastal marine environments is the accumulation of contaminants in sediments and their potential mobility. The sediment acts as a sink for many chemical species (metal(oid)s, PAHs, PCBs etc.). However, this situation can be only temporary since early diagenesis biogeochemical processes can recycle these contaminants which may subsequently accumulate along the aquatic trophic chain. In this work, in situ experiments were conducted at two tourist ports (marinas) located in the Gulf of Trieste (northern Adriatic Sea), one in Slovenia and one in Italy. The latter is well known to be a site contaminated by long-term shipbuilding activities. The main aim was to understand if and where recycling at the sediment-water interface (SWI) may affect trace metal(oid)s. A benthic chamber, successfully used in other works in the same Gulf 1,2, was employed. Water sampling was performed during a 8-hour period to measure trace metal(oid) concentrations with time. Short sediment cores were collected near the chamber to investigate the solid (sediments) and dissolved phases (porewaters). Both diffusive and benthic fluxes were estimated to elucidate the release of trace metal(oid)s at the SWI. Total trace element concentrations were determined following a complete mineralization of the sediment (aqua regia + HF), whereas a weak extraction with diluted HCl (0.5 M) was carried out to quantify their potential “bioavailable fraction”. Quantitative analyses were performed by ICP–OES on sediment mineralized solutions and by ICP–MS on porewater and benthic water samples. Total element contents in sediments, resulted up to two orders of magnitude higher in the Italian marina (0.4 %Pb, 0.15% As and Cu, 0.25% Zn) than in the Slovenian one, confirming the high contamination level of this site. Despite this heavy contamination, the “bioavailable fraction” of metal(oid)s extracted was scarce or null. Conversely, sediments from the Slovenian site showed high percentages of the extractable fraction from 4% (Cr) to 82% (Cu) of the total content. Trace metal vertical profiles in porewaters showed a clear diagenetic sequence. The suboxic/anoxic conditions of sediments allowed the dissolution of Fe and Mn oxy-hydroxides, thus enhancing the concentrations in porewaters of Fe, Mn and other associated trace metal(oid)s. However, the diagenetic sequence and the suboxic/anoxic transition were highly dependent on the characteristics of each site. Maximum concentrations of dissolved Fe, Mn, Pb and Zn were found in the first centimeters of one site of the Italian marina where sediments became quickly anoxic with depth. Conversely, in the Slovenian marina and in the second Italian site, the highest concentrations were recovered from the deepest porewater layers, especially for Fe (up to 2.5 and 7.7 mg L-1, respectively). Positive effluxes were observed for Mn, Pb, Zn and V in the Italian marina whereas for Cu and Ni were most notably in the Slovenian marina and for as at both sites. Hg fluxes were low in spite of its high concentrations (up to 1000 mg kg-1) in sediments of the Italian site. In general, benthic fluxes of metal(oid)s at the SWI can be partially explained by considering the dissolution of Fe/Mn oxy-hydroxides and metal speciation in bottom sediments. The results suggest that although the bottom sediments of the Italian marina exhibit the highest trace metal(oid) concentrations, they are scarcely remobilizable. On the contrary, in the Slovenian marina, sediments seem to be comparatively a significant source of trace elements (except for Fe, Pb and V) in the water column as consequence of diagenetic processes at the related interface.

The Orcia River basin lies north of the Mt. Amiata mining district and may receive potentially harmful/toxic elements such as mercury (Hg) and arsenic (As) therefrom. The Orcia River eventually flows to the Ombrone River, which in turn flows to the Tyrrhenian Sea. The analysis of stream sediments collected in the Orcia River and its main tributaries, as well as in the Ombrone River, indicates moderate concentrations of both Hg and As (median values, Hg 118 μg/kg and As 5.25 mg/kg), rarely exceeding Italian environmental quality standards. Exceptionally high values for both elements are observed only in close proximity to the former Pietrineri Hg mine (Hg 195 mg/kg and As 35 mg/kg). Travertine and unconsolidated deposits associated with thermal springs in the area generally exhibit low Hg concentrations (4–320 μg/kg), with a significant exception of 23 mg/kg at Bagni San Filippo. Arsenic concentration in the same deposits is more variable with a peak level of 358 mg/kg. Surface waters collected at the same sites as stream sediments show Hg and As concentrations below the Italian mandatory limits for drinking waters (1 μg/L for Hg and 10 μg/L for As). Likewise, in thermal springs, Hg concentrations are low, whereas As concentrations are relatively high (up to 23.4 μg/L), which is in agreement with previous studies. At present, the input of toxic elements from the mining district into the Orcia and Ombrone watersheds is lower than inputs documented in the Paglia and Tiber catchments south of Mt. Amiata and does not pose an immediate environmental threat. However, the possible remobilization of Hg-contaminated sediments during flash flood events cannot be dismissed.

The content of several heavy metals (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn) was determined in sediments and in plants (the halophytes Sarcocornia fruticosa and Limonium vulgare) from two selected saltmarshes located in the Marano and Grado Lagoon (Northern Adriatic Sea). This environment has been affected by severe Hg contamination from both industrial and long-term mining activities. In both saltmarshes, Hg content in sediments exceeded the estimated background value (0.13 µg g -1 ), showing the highest concentrations (13.7 µg g -1 ) in the eastern sector (Grado Lagoon), the most affected by cinnabar ore extraction. On the other hand, the saltmarsh, located in the Marano Lagoon, showed a higher degree of contamination for As, Cd and Pb, which can be related to industrial sources. The rhizo-sediments of both halophytes reflected the characteristics of the non-vegetated sediment, with higher organic carbon content and similar metal concentrations. Enrichment Factors (EF=(metal)root/(metal)rhizo-sediment) for each sediment layer were calculated for both halophytes, showing metal enrichments in the roots and the presence of preferential layers of metal accumulation. Hg showed accumulation (EF>1) in the roots below the 20 cm depth, with higher contents in S. Fruticosa. As and Cd were accumulated by both halophytes, more efficiently by S. Fruticosa, and the same species showed also accumulation of Pb and Zn. Translocation of metals from the roots to the aboveground biomass was investigated by measuring metal contents in shoots and leaves of the two species. With the exception of Cd and Hg, all metals were present in the aboveground biomass, most evidently for Cr in S. Fruticosa and Zn in L. Vulgare, although the presence of the latter in leaves could be due to plant physiology rather than translocation of the contaminant.