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A laboratory-incubated redox oscillation experiment to investigate Hg fluxes from highly contaminated coastal marine sediments (Gulf of Trieste, Northern Adriatic Sea)
No full textMercury (Hg) mobility at the sediment-water interface was investigated during a laboratory incubation experiment conducted with highly contaminated sediments (13 μg g-1) of the Gulf of Trieste. Undisturbed sediment was collected in front of the Isonzo River mouth, which inflows Hg-rich suspended material originating from the Idrija (NW Slovenia) mining district. Since hypoxic and anoxic conditions at the bottom are frequently observed and can influence the Hg biogeochemical behaviour, a redox oscillation was simulated in the laboratory, at in situ temperature, using a dark flux chamber. Temporal variations of several parameters were monitored simultaneously: dissolved Hg and methylmercury (MeHg), O2, NH4+, NO3-+NO2-, PO43-, H2S, dissolved Mn2+, dissolved inorganic and organic carbon (DIC and DOC). Under anoxic conditions, both Hg (665 ng m2 day-1) and MeHg (550 ng m2 day-1) fluxed from sediments into the water column, whereas re-oxygenation caused concentrations of MeHg and Hg to rapidly drop, probably due to re-adsorption onto Fe/Mn-oxyhydroxides and enhanced demethylation processes. Hence, during anoxic events, sediments of the Gulf of Trieste may be considered as an important source of dissolved Hg species for the water column. On the contrary, re-oxygenation of the bottom compartment mitigates Hg and MeHg release from the sediment, thus acting as a natural “defence” from possible interaction between the metal and the aquatic organisms
Recent and historical accumulation of mercury in the sediments of Grado and Marano Lagoon (Northern Italy)
No full textOrganic Carbon and humic substances in sediments of Grado and Marano Lagoon
No full textMercury contamination in sediments is a major concern, especially, in bivalves farming area, due to the potential risk of bioaccumulation. A substantial fraction of the so-called refractory organic matter in sediments is constituted by humic substances (HS). HS are ecognized to play an important role in complexing heavy metals, mercury included, thus favoring their mobilization or accumulation in sediments. In the framework of the MIRACLE project (Mercury Interdisciplinary Research for Appropriate Clam farming in Lagoon Environment) sediment cores have been sampled in 15 stations located in Grado and Marano lagoon and in 4 stations in Aussa River, one of the main freshwater inputs in this environment. The aim of our study was the evaluation of the organic carbon content in sediments, the estimation of the contribution of humic substances to
total organic carbon and the elemental characterization of HS. Riverine sediments showed high organic carbon values (mean 2.46±1.47 %), increasing upstream from the river mouth and C/N
atomic ratios higher (8.7±2.14) than lagoon sediments. Organic carbon content was similar in surficial and sub-surficial lagoon sediments (mean values 1.28±0.53 and 1.28±0.62 respectively), but
higher C/N ratio have been observed in the deeper levels of the cores (7.1±1.5 with respect to 8.0±1.6 in the surficial layer). Humic substances extracted from sediments showed a high carbon
content (mean 50.5±1.5 %). Humic acids concentrations in sediments fall in the range 1.8-31 mg g-1. The contribution of humic carbon to total organic carbon was relevant (up to 39.5 %), pointing out
the important role of HS in the accumulation and transformation of organic material in the lagoon environment. Preliminary data showed no differences of the humic contribution to total organic carbon among upper and deeper levels of the cores
Historical flux of mercury associated with mining and industrial sources in the Marano and Grado Lagoon (northern Adriatic Sea)
No full textThe “MIRACLE” Project was established in order to assess the feasibility of clam farming and high levels of sediment mercury (Hg) contamination coexisting in the Marano and Grado Lagoon, Italy. This lagoon has been subjected to Hg input from both industrial waste (chlor-alkali plant) and long-term mining activity (Idrija mine, NW Slovenia). One of the subtasks of the “MIRACLE” Project was to determine the historical evolution of Hg accumulation in the lagoon’s bottom sediments. Thirteen 1-m deep sediment cores were collected from the subtidal and intertidal zones, plus one in a saltmarsh, all of which were then analyzed for total Hg content and several physicochemical parameters. Sedimentation rate assessments were performed by measuring short-lived radionuclides (excess 210Pb and 137Cs). For most of the analyzed cores, natural background levels of Hg were observed at depths of 50 e 100 cm. In the eastern area, Hg contamination was found to be at its maximum level at the core top (up to 12 mg g-1) as a consequence of the long-term mining activity. The vertical distribution of Hg was related to the influence of the single-point contamination sources, whereas the grain-size variability or organic matter content seemed not to affect it. In the western area, Hg content at the surface was found not to
exceed 7 mg g1 and contamination was recorded only in the first 20e30 cm. Geochronological measurements showed that the depositional flux of Hg was influenced by anthropogenic inputs after 1800, when mining activity was more intense. After 1950, Hg in the surface sediment, most remarkable in the central-western sector, seemed to also be affected by the discharge of the Aussa River, which delivers Hg from the chlor-alkali plant. In 1996, Hg mining at Idrija ceased, however the core profiles did
not show any subsequent decreasing trend in terms of Hg flux, which implies the system retaining some “memory” of contamination. Thus, in the short term, a decrease in Hg inputs into the nearby Gulf of Trieste and the lagoon seems unlikely. A preliminary rounded-down gross estimate of total Hg “trapped”
in the lagoon’s sediments amounted to 251 t. Such a quantity, along with the complexity of the lagoon ecosystem, suggests that an in toto reclamation of the sediments at the lagoon scale is unfeasible, both economically and environmentally
Historical accumulation of mercury from mining and industrial activities in the Marano & Grado Lagoon (northern Adriatic sea)
No full text7th International SedNet Conference on 6-9 April 2011, Venice, Italy, Book of Abstrac
Historical sedimentary trends of mercury and other trace elements from two saltmarshes of the Marano and Grado lagoon (northern Adriatic Sea)
No full textPurpose: 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 historical geochronology of Hg.
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. 137Cs was measured via gamma spectrometry. 210Pb activity was measured via alpha-counting of its daughter, 210Po, 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 height of Hg extraction activity at the Idrija mine (1850). Both salt marshes 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 y-1 at Marano and from 0.30 to 0.74 cm y-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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Potential bioaccumulation of trace metals in halophytes from saltmarshes of a northern Adriatic coastal lagoon
No full textPurpose 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 <1. Conclusions The general trend arising from BCF and TF reveals that root tissues accumulate significantly greater
amounts of metal(oid)s than the aerial part, thus indicating high plant bioavailability of the substrate metal(oid)s as well as their limited translocation to the aboveground biomass. Our results suggest that both saltmarshes investigated act as a sink, and only sporadically as a possible source, for several trace metal(oid)s which are not promptly available for the environment
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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