13 research outputs found
Detecting and characterizing sources of persistent organic pollutants (PAHs AND PCBs) in surface sediments of an industrialized area (Harbour of Trieste, Northern Adriatic)
No full textA sediment sampling based on a two-dimensional mapping was performed in the harbour of Trieste (northern Adriatic Sea), considering 28 sites exposed to pollutant inputs from harbour and industrial activities. Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were determined in surface sediments, because these very persistent pollutants seem to be responsible for the depletion of benthic populations observed in this area. The correlation matrix indicates that PAHs and PCBs are non-correlated, and probably have different sources. Both cluster analysis performed on the sampling sites and graphical drawing of the PAH sediment contents make it possible to locate along the shoreline a band of more polluted sediments, clustered around a site facing a steelmaking factory, to be considered as the main source point for PAHs. The evaluation of phenanthrene to anthracene (P/AN) and fuoranthene to pyrene (FL/PY) ratios permits the assessment of the pyrolytic, industrial origin of these PAHs, rejecting a second possible source of hydrocarbons (i.e., an oilpipeline terminal, situated near the steelmaking factory). Graphical drawing of the total PCB iso-concentrations reveals a different source-point for this other category of very persistent pollutants
Heavy metals in surface sediments near urban and industrial sewage discharges in the Gulf of Trieste
No full textRapid 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
A two-dimensional detector for pump-and-probe and time resolved experiments
No full textWe present a new bidimensional detector setup, based on cross delay line technology, specifically developed for time resolved experiments and particularly suited to work in conjunction with pump-and-probe systems. Thanks to the particular architecture of the acquisition electronics, the detector is able to correlate each event with the time it occurred in a way which preserves the picoseconds time resolution of pump-and-probe techniques and, more generally, can perform time resolved acquisition in the nanosecond or picoseconds scale. The acquisition setup count rate, up to more than 4 Mcounts/s in time resolved mode, exceeds the performances of the best two-dimensional detectors working in counting mode presently available on electron analysers. First experimental results, obtained both on bench tests and in UHV conditions, where the detector has been mounted on an electron analyser, confirm the validity of the approach and show the potentiality of time resolved acquisition applied to electron spectroscopy analysis
Risk analysis in alluvial soils contaminated by mercury from historical mining activities through metal speciation: a comparison between thermo-desorption and selective sequential extraction
No full textMercury (Hg) is recognised as a global pollutant occurring under various forms in the environment, each characterised by different mobility and bioavailability. Thus, determination of Hg speciation in environmental samples is essential for a proper evaluation of Hg pollution impact and potential associated health risk. Selective sequential extraction (SSE) techniques are usually used to assess Hg speciation in soils, but this approach is usually time-consuming and suffers of low reproducibility of results [Issaro et al., 2009]. An alternative option to SSE may be represented by thermo-desorption (TD), which allows a simple discrimination of Hg occurring as non-mobile red cinnabar (α-HgS) thanks to its specific release peak temperature. In this study, the application of TD for health risk assessment was tested in some sites within the Isonzo alluvial plain, impacted by past mining activity at upstream Idrija Hg mine [Acquavita et al., 2022]. Potential risk associated with Hg volatilisation, leaching and ingestion was modelled considering the average amount of non-cinnabar (non-α-Hgs) fraction determined on all available soil samples. Results were compared with those obtained through SSE approach [Bloom et al., 2003]. Due to contamination from mining, in all samples α-HgS was the predominant fraction. Overall, TD overestimated the risk associated with volatile and soluble fractions of Hg compared to SSE. Conversely, comparable and acceptable risk (hazard index <1) was obtained for ingestion pathway through both techniques. However, TD allows to analyse a higher number of samples than SSE in less time, resulting in an increased representativeness of real situation. Considering also the good reproducibility of the results, TD can thus represent a valuable tool for a first screening of potential health risk at Hg contaminated sites, possibly coupled with simple single-step extractions for the determination only of soluble Hg fraction
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
Nutrient distribution in locations of the Gulf of Trieste (northern Adriatic sea) suspected of pollution
No full textEffects of suspended mussel culture on the macrozoobenthos in the Gulf of Trieste (northern Adriatic sea, Italy)
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