11 research outputs found
Rapid thermoscanning technique for direct analysis of mercury species in contaminated sediments: From pure compounds to real sample application
No full textMercury (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 effects of resuspension on the fate of Hg in contaminated sediments (Marano and Grado Lagoon, Italy): Short-term simulation experiments
No full textSediments of the Marano and Grado Lagoon (Adriatic Sea, Italy) represent one of the world’s most major repositories of mercury (Hg). Its presence is a direct consequence of the historical mining activity in nearby Idrjia (Slovenia), as well as significant discharges from a chlor-alkali plant into the AussaeCorno river system, which connects to the lagoon. 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 work reported in this paper formed part of the multidisciplinary “MIRACLE” project, aimed at identifying areas at low risk of Hg bioaccumulation in commercial Manila Clams, an important part of the local economy in this region. The effect of resuspension on the cycling of inorganic mercury (IHg), reactive mercury (RHg) and methylmercury (MeHg) between the sediment and water columnwas investigated in a mesocosm study. Two experiments were conducted in October 2009 and September 2010 based on 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 mercury (THg), suggesting that the enhancement of methylation processes may occur. The findings reported in this paper may be useful for the local management of dredging and fishing activities, although mass balance calculations showed that the total flux of Hg species are trivial compared to lagoon-wide processes
Does anoxia affect mercury cycling at the sediment-water interface in the Gulf of Trieste (northern Adriatic Sea)? Incubation experiments using benthic flux chambers
No full textCoastal areas in the northernmost part of the Adriatic Sea (Gulf of Trieste and the adjacent Grado Lagoon) are characterized by high levels of mercury (Hg), both in sediments and in the water column, mainly originating from the suspended material inflowing through the Isonzo/Soča River system, draining the Idrija (NW Slovenia) mining district, into the Gulf of Trieste. Hypoxic and anoxic conditions at the sediment-water interface (SWI) are frequently observed in the Gulf of Trieste and in the lagoon, due to strong late summer water stratification and high organic matter input. Hg mobility at the SWI was investigated at three sampling points located in the Gulf of Trieste (AA1, CZ) and in the Grado Lagoon (BAR). Experiments were conducted under laboratory conditions at in situ temperature, using a dark flux chamber simulating an oxic-anoxic transition. Temporal variations of dissolved Hg and methylmercury (MeHg) as well as O2, NH4+, NO3-+ NO2-, PO43-, H2S, dissolved Fe and Mn, dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) were monitored simultaneously.
Benthic Hg fluxes were higher under anoxic conditions than in the oxic phase of the experiment. MeHg release was less noticeable (low or absent) in the oxic phase, probably due to similar methylation and demethylation rates, but high in the anoxic phase of the experiment. The MeHg flux was linked to sulphate reduction and dissolution of Fe (and Mn) oxyhydroxides, and formation of sulphides. Reoxygenation was studied at sampling point CZ, where concentrations of MeHg and Hg dropped rapidly probably due to re-adsorption onto Fe (Mn) oxyhydroxides and enhanced demethylation. Sediments, especially during anoxic events, should be, hence, considered as a primary source of MeHg for the water column in the northern Adriatic coastal areas
Mercury Levels in Sediment, Water and Selected Organisms Collected in a Coastal Contaminated Environment: The Marano and Grado Lagoon (Northern Adriatic Sea, Italy)
No full textMercury (Hg) is a global pollutant capable of bioaccumulates/biomagnifies along the trophic chain and posing concerns for organisms and humans. The historical mining in Idrija (NW Slovenia) and the more recent activity of a chlor-alkali plant (CAP) sited in Torviscosa (NE Italy) causes diffuse Hg contamination in the Marano and Grado Lagoon (MGL, northern Adriatic Sea, Italy). Despite the importance of fishing and aquaculture for local inhabitants, knowledge of the Hg content of MGL fish is still scarce and fragmentary. This paper reports the results obtained from the collection of sediments, water, and biota during the implementation of the WFD/2000/60/CE. The solid phase is characterised by high Hg concentrations (up to 7.4 mg kg−1) with a net positive gradient moving eastward, but chemical speciation suggests the prevalence of cinnabar (not mobile) species. The scarce mobility of Hg is attested to by the low concentrations found in surface waters. Hg in fish often exceeds the limit set for commercialization (0.5 mg kg−1 ww), especially in the Grado basin, but its content is variable depending on the size and habits of species. Although there was a significant linear relationship between THg content in sediment and tissues of Chelon auratus, the values of the biota sediment accumulation factor (BSAF), which were always less than one, suggest that the Hg bioavailable for transfer from sediment to biota is low. Additionally, the Target Hazard Quotient (THQ) calculated on C. auratus’s daily consumption showed that adverse effects on human health are out of the question at least for the Marano basin
Gaseous mercury evasion from bare and grass-covered contaminated soils at the Isonzo River alluvial plain (North Eastern Italy)
No full textEmissions of gaseous elemental mercury (Hg0) from soil surface represent a relevant component of the global biogeochemical cycle of this element. Terrestrial environments characterised by a high mercury (Hg) content in the substrate due to natural enrichments and/or anthropogenic activities may be an important source of Hg0 for the atmosphere [Eckley et al., 2016]. The alluvial plain of the Isonzo River (NE Italy) suffered a significant contamination due to the historical extraction of the cinnabar ore from the upstream Idrija mine (Slovenia). The magnitude and extension of Hg contamination of soils in this area have been recently described in detail [Acquavita et al., 2021], although an assessment of Hg0 releases from the soil is still lacking. In this work, Hg0 evasion fluxes at the soil-air interface were measured by means of a non-steady state flux chamber coupled with a real-time Hg0 analyzer (Lumex RA-915M) at 6 sites within the Italian sector of the Isonzo plain in summer. At each site, distinct sets of measurements were performed at regular time intervals during the diurnal period, both on bare and grass-covered soils, together with monitoring of soil and air temperature and incoming UV radiation. Moreover, soil samples were analyzed for organic matter content and total Hg concentration. Gaseous Hg fluxes (range=48.2÷944.6 ng m-2 h-1) were comparable with values reported for other sites impacted by mining activity worldwide [Agnan et al., 2016] and generally resulted 1.5- to 3-times higher for bare than grass-covered soils at each site, confirming the role of vegetation cover in influencing Hg release to the atmosphere. Overall, the amount of Hg0 fluxes at different sites seems to be related to total Hg content of soils (range=1.98÷28.93 mg kg-1), although the correlation was significant only for bare soils. Finally, Hg0 fluxes were found to track the incoming UV radiation during sampling, likely due to Hg photo-reduction on surface and soil heating.
Acquavita A., Brandolin D., Cattaruzza C., Felluga A., Maddaleni P., Meloni C., Pasquon M., Predonzani S., Poli L., Skert N., Zanello A., (2021). Mercury distribution and speciation in historically contaminated soils of the Isonzo River Plain (NE Italy). Journal of Soils and Sediments, doi: 10.1007/s11368-021-03038-2.
Agnan Y., Le Dantec T., Moore C.W., Edwards G.C., Obrist D., (2016). New constraints on terrestrial surface-atmosphere fluxes of gaseous elemental mercury using a global database. Environmental Science & Technology, 50, 507-524, doi: 10.1021/acs.est.5b04013.
Eckley S.C., Tate M.T., Lin C.J., Gustin M., Dent S., Eagles-Smith C., Lutz M.A., Wickland K.P., Wang B., Gray J.E., Edwards G.C., Krabbenhoft D.P., Smith D.B., (2016). Surface-air mercury fluxes across Western North America: A synthesis of spatial trends and controlling variables. Science of the Total Environment, 568, 651-665, doi: 10.1016/j.scitotenv.2016.02.121
Does anoxia affect mercury cycling at the sediment-water interface in the Gulf of Trieste (northern Adriatic Sea)? Incubation experiments using benthic flux chambers
No full textCoastal areas in the northernmost part of the northern Adriatic Sea (Gulf of Trieste and adjacent Grado lagoon) are characterized by high levels of mercury (Hg) in sediments and water column mainly originating from the suspended material inflowing through the Isonzo - Soča river, originating from the Idrija (NW Slovenia) mining district, into the Gulf of Trieste. The Hg pollution is a result of 500-year mining activity reflected in a wide public health concern. Hzpoxic and anoxic conditions at the sediment-water interface are frequently observed in the Gulf of Trieste and in the lagoon due to stronglate summer density stratification and high organic matter input. Hg mobility at the sediment-water interface was investigated at three sampling points located in the Gulf of Trieste (AA1, CZ) and Grado Lagoon (BAR). Experiments were conducted under laboratory conditions at in situ temperature using a dark flux chamber simulating an oxic-anoxic transition.Temporal variations of dissolved Hg and MeHg as well as O2, NH4+, NO3-, PO43-, H2S, Fe2+, dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) concentrations were monitored simultaneously. Fluxes of solutes across the sediment-water interface were calculated from linear regressions of the variation of solute concentrations, measured in oxic and anoxic conditions with incubation time. Our results show low benthic Hg effluxes and even influxes in oxic conditions and effluxes in the anoxic phase of the experiment. MeHg release was less noticeable (low or absent) in the oxic phase, probably due to similar methaylation and demethylation rates, but high in the anoxic phase of the experiment. In this context, the MeHg flux was linked to sulphate reduction and dissolution of Fe (and Mn), oxyhydroxides, and formation of sulphides and carbonates. The impact of DOM on Hg and MeHg oxic and anoxic fluxes was of minor importance, suggesting that the majority of dissolved Hg and MeHg are not linked to DOM. In the reoxigenation phase, studied at sampling point CZ by opening the chamber after a period of two weeks, the concentrations of MeHg and Hg dropped rapidly probably due to re-adsorption onto Fe (Mn) hydroxides and enhanced demethylation. Sediments, especially during anoxic events, should be, hence, considered as a primary source of MeHg for the water column in the northern Adriatic coastal areas
C.: Recent contamination of mercury in an estuarine environment (Marano lagoon
No full texta b s t r a c t The Marano Lagoon, in the northern Adriatic Sea (Italy), has been affected by mercury (Hg) contamination from industrial and mining activities. It has been estimated that 186,000 kg of Hg were deliberately discharged into the main drainage system (Aussa-Corno River) by a chlor-alkali plant (CAP) from 1940s to 1984. The lagoon has also experienced a secondary long-term Hg input, originated from mining activity in Idrija (Slovenia), due to the supply of fluvial suspended particles carried by the Isonzo River in the Gulf of Trieste. Since local fishing activities are extensively conducted, there is great concern on the risk posed by potentially harmful effects of Hg to the trophic chain. Present inputs of this metal, both in dissolved (52.4-4.1 ng L À1 ) and particulate (130.8-3.4 ng L À1 ) phases, were preliminary investigated in the water column. Although direct discharge of Hg from the CAP no longer exists, the metal is still released from the source area into freshwaters, and its distribution and abundance is controlled by the salt-wedge circulation system, which is tide-influenced. Remobilization from bottom sediments can also be a secondary source of Hg into the aquatic environment. A speciation technique, used to investigate the main binding sites and phase associations of Hg in sediments (5.69-0.82 mg g À1 ), evidenced the presence of mobile (1.8-11%) and potentially available species for methylation processes. The results are particularly important if related to resuspension effects caused by natural events and anthropogenic activities. Preliminary considerations on Hg behaviour in this estuarine environment are reported
Status and achievements at FERMI@Elettra: the first double cascade seeded EUV-SXR FEL facility open to users
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