Fluxes of settling sediment particles and associated mercury in a coastal environment contaminated by past mining (Gulf of Trieste, northern Adriatic Sea)

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 fuxes. 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 fuxes, 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

Modern sedimentary facies in a progradational barrier-spit system, Goro lagoon, Po delta, Italy

Barriers and spits connected to fluvial sedimentary sources represent environments which tend to evolve rapidly and experience sudden transformations, mainly driven by changes in sediment supply and path. As a consequence, the variability of facies is significant even within small sedimentary records. The 7 km long barrier-spit system facing the Goro Lagoon, and fed by the mouth of the Po di Goro, is a typical example of an accretionary coastal morphotype, suitable to describe adjacent nearshore depositional environments and their stratigraphic signatures, variability, and relationships. Thirteen short cores of sediment were sampled in order to represent the variable depositional subenvironments from the shoreface (prodelta-delta front) to the back barrier, crossing the active barrier-spit and the ancient spit arms and relative swales. The description of the modern sedimentary records, improved upon using core X-rays, has been coupled with information on the morphological changes which occurred during the period of maximum spit development (1955\u20132000), based on available aerial photos and a cartographic/topographic dataset. The results obtained allow for the description and interpretation of the depositional environments changing at the human-scale. Sediments of the upper shoreface are quite uniform, composed by evenly laminated sands; the transition between delta front and prodelta at a depth of 6m is marked by the alternation of sand and mud beds. These reflect the periodic changes in sediment supply by the river, as well as storm events. The most recent spit branch and the relative back barrier-swale environment are the results of the rapid progradation of the spit system, which implies phases of rapid longshore growth, hooked spit development, cannibalization, overwash, and breaching. Morphodynamic changes have resulted in an overlap of short sedimentary records where stratigraphic signatures are linked either to phases of sediment transport and selection by waves and tidal currents (cross-bedding, foreset, and planar laminated sands, shell imbrication, massive beds) or to phases of sedimentary stasis when biological activity is predominant (algal mat and bioturbation). Human signature is also well marked inside the stratigraphic record. Clam harvesting is carried out within the lagoon, causing the physical disturbance and winnowing of the superficial sediment, thus inducing the local formation of graded beds and shell rehash

Early cementation and accommodation space dictate the evolution of an overstepping barrier system during the Holocene

The morphology and stratigraphic features of a well-preserved drowned barrier system, located on the western coast of Sardinia (Mediterranean Sea), are presented here. The barriers were mapped using a multibeam echosounder. The Digital Terrain Model of the seabed revealed five sub-parallel barriers in a depth range of 18\u201337 m, with a distance of ~ 300 m between each single barrier. Direct inspection by scuba diving, revealed that the barriers consist of beachrocks, topped by seagrass meadows growing on a biogenic hardground. The inner-most barrier is limited landward by a steep cliff, 10 m high, bordering the back-barrier area. About 200 km of seismic lines were collected along the barrier system using a 0.4\u20131.0 kJ sparker source and a 3.5 kHz Chirp Subbottom profiler. The seismic data, calibrated with vibrocores, allowed us to recognize the subaerial topographic surface of the last glacial maximum as well as several seismic units interpreted as the Pliocene marine sediments, the pre-Holocene deposits and the Holocene barrier\u2013lagoon complex composed of shoreface, barrier, lagoonal/deltaic and beach deposits. Despite the relatively high seabed gradient (0.3\ub0\u20130.4\ub0) and the relatively low rate of sea-level rise (10\u201315 mm y 12 1), the barriers were well preserved due to the early diagenetic processes which led to a rapid cementation with the formation of beachrocks, and the subsequent overstepping with the rise of the sea level. The development of the overstepping barrier system is strictly related to the antecedent subaerial topography which is, in turn, related to the tectonic setting of the area. The Pliocene seismic unit was lowered by a direct fault at the entrance of the gulf forming a depression filled by sediments. The overstepping barrier system developed following the increase of the seabed gradient and was limited landward by the above-mentioned depression which increased the accommodation space. Following the sea-level rise and the barrier formation, this depression was filled by lagoonal sediments, washover fans and sediments coming from the rivers. The age model of barrier evolution, based on previous sea-level-rise curves during the Holocene, supported by radiocarbon data, highlighted that the whole system evolved over a time period of 1 ka; while the time elapsed from this formation to the drowning of single barriers was estimated to be in the order of magnitude of centuries. Scenarios of short-term evolution of modern barrier\u2013lagoon systems of the adjacent coastal sector, under conditions of accelerated sea-level rise, according to Church et al. (2013) (2013 IPCC report) and Rahmstorf (2007) projections, were elaborated. The study of this ancient analogue suggests that the processes of adaptation of coastal systems to the rising sea level would require times evaluable from centuries to millennia

Occurrence and speciation of arsenic and mercury in estuarine sediments affected by mining activities (Asturias, northern Spain)

Sediments contaminated by Hg and As from two historical mining areas have been deposited in the Nalon estuary (Asturias, northern Spain) since 1850. Total mercury (Hgtotal) concentrations in the sediments range from 0.20 \u3bcg.g 121 to 1.33 \u3bcg.g 121 , most of it in the form of sulphides. Concentrations of methylmercury (303.20\u2013865.40 pg.g 121) are up to two orders of magnitude lower than the concentration of Hgtotal. Total As concentration (Astotal) is enriched compared to the background level for the area. The relative abundance of As(V) on As(III) in the sediments ranges from 97.6% to 100%, whereas inorganic Hg accounts for more than 99% of the total Hg. The occurrence of the most toxic species, inorganic As(III) and organic methylmercury, seem to be related to redox conditions together with the amounts of sulphur which act as natural barriers which inhibit the biological and chemical speciation processes. Despite the high amounts of Hg and As present in the sediments, their transference to the water column appear to be limited thus converting sediments in an effective sink of both elements. Special attention should be paid to potential variations of the environmental conditions which might increase the element mobility and exchange between sediments and the water column

University of Trieste

Appare opportuno riproporre un itinerario ideale attraverso la vita universitaria triestina con un volume che ne descriva, in chiave aggiornata, le innovazioni, l’articolazione strutturale, le ricerche scientifiche e le principali offerte di studio. Conoscere la Trieste accademica, con un testo anche in versione inglese, è quindi un obiettivo che ci poniamo in un’ottica di ampia diffusione del nostro ruolo culturale in un territorio vasto, che travalica i consueti confini nazionali, per estendersi alle nazioni limitrofe, all’ampio bacino danubiano, all’Europa intera, alla dimensione più propriamente internazionale e globale. D’altra parte, è noto come l’Università di Trieste sappia attrarre, da decenni, una quota sempre rilevante di studenti stranieri, certamente in virtù della sua ottimale posizione geografica, ma non solo, perché giungono, nella nostra città, giovani e studiosi provenienti ormai da tutti continenti. La città mercantile, crocevia di traffici e commerci, si può ben dire riviva oggi nella sua università e nelle altre prestigiose istituzioni scientifiche del territorio, con l’ateneo strettamente connesse, rinverdendo così una tradizione che ha sempre visto Trieste qualificato polo di attrazione dei migliori talenti culturali. L’auspicio più vivo è quindi che il lettore possa cogliere, attraverso il percorso di questo volume, affidato al dispiegarsi di idonee immagini, dati e testi illustrativi, le peculiarità più caratterizzanti di un ateneo dalle solide tradizioni, che non a caso celebra quest’anno il suo 90° anno di storia, eppure proiettato con slancio, direi molto giovanile, verso traguardi futuri di forte innovazione e cambiamento

X-ray Computed Tomography as a Tool for Screening Sediment Cores: An Application to the Lagoons of the Po River Delta (Italy)

Lagoon sediments have heterogeneous structure and texture, contain shells and plants and are often highly bioturbated and disturbed by human activities. In such sediments, the selection of representative cores and the choice of a subsampling strategy are important but difficult. In this study, we examine the usefulness of X-ray computed tomography (CT) for inferring sediment features that will help in making optimal decisions prior to core opening (24 cores from seven lagoons). Various algorithms (intensity projections, slice thickness, axial and sagittal images, CT number profiles and volumetric region of interest) are tested to visualise low- and high-density volumes or objects and to quantify the relations between the average volumetric CT number and the bulk density of the sediment matrix. The CT number is related mainly to water content and indirectly to total nitrogen and <16-m grain-size fraction (model R2 = 0.94). The outliers are attributed to a weak correspondence between the fraction of sediment sampled for water content determination and the volume of sediment matrix used for CT number measurements in highly heterogeneous sediment slices. In conclusion, CT is a powerful tool for the initial screening of cores recovered from heterogeneous lagoon sediments. The adequate use of available algorithms may provide quantitative information on various sediment features, allowing the purposeful selection of cores and subsamples for further investigation

Geomorphological characterization of the coastal and marine area between "Primera and Segunda Angostura", Strait of Magellan (Chile).

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Inventory and conservation assessment for the management of coastal dunes, Veneto coasts, Italy

Management of coastal dunes on developed coasts could effectively take advantage of comprehensive and multi temporal georeferenced data collection, which offers the possibility to relate dune data with the natural and cultural characteristics of the beach and hinterland. The recent implementation of a coastal management geodatabase for the Veneto region provides the opportunity for improving knowledge on coastal dunes on developed littoral as well as a basis for appropriate future coastal planning in the study area. The geodatabase gathers data concerning different physical, evolutionary and human aspects of the coastal zone, with a special focus on coastal dunes. Established foredunes, human-altered dunes and relict dunes are irregularly distributed along 59 km, 38% of the entire coastal length. Their distribution and characteristics are the result of favourable natural conditions as well as long-lasting tourism exploitation (evaluated through an index of Land Use Pressure) and fragmentary and diversified uses of beaches (evaluated through an index of Tourism Pressure on the beach). At the same time, beach/dune nourishment intervention allowed the presence of artificial or sand fenced dunes along 17 km of coast. High dune elevation up to 8\u201310 m is promoted by the onshore exposition of the beach to dominant wind (from ENE), by stable-to-slowly negative sedimentary budget or by the re-activation of high relict foredunes in the case of shoreline retreat associated with strong negative budget. Present sedimentary budget (evaluated through the code ASPE \u2013 Accretion, Stable, Precarious, Erosive) is the tool used for dividing coasts in sedimentary compartments or cells. Past and present sedimentary budget and different human responses to erosive cases (hard and soft interventions) give the foredunes different means to form, grow, survive and evolve over time. The assessment of human impact and active management practices on the dunes allows a first evaluation of the management effectiveness, which shows strong shortcomings for 81% of the dunes. The great variability of beach usage, human impact and management practises on the different dune stretches highlight the lack of effective and systematic management actions being correctly scheduled and performed

X-ray Computed Tomography as a Tool for Screening Sediment Cores: An Application to the Lagoons of the Po River Delta (Italy)

Lagoon sediments have heterogeneous structure and texture, contain shells and plants and are often highly bioturbated and disturbed by human activities. In such sediments, the selection of representative cores and the choice of a subsampling strategy are important but difficult. In this study, we examine the usefulness of X-ray computed tomography (CT) for inferring sediment features that will help in making optimal decisions prior to core opening (24 cores from seven lagoons). Various algorithms (intensity projections, slice thickness, axial and sagittal images, CT number profiles and volumetric region of interest) are tested to visualise low- and high-density volumes or objects and to quantify the relations between the average volumetric CT number and the bulk density of the sediment matrix. The CT number is related mainly to water content and indirectly to total nitrogen and &lt;16-μm grain-size fraction (model R2 = 0.94). The outliers are attributed to a weak correspondence between the fraction of sediment sampled for water content determination and the volume of sediment matrix used for CT number measurements in highly heterogeneous sediment slices. In conclusion, CT is a powerful tool for the initial screening of cores recovered from heterogeneous lagoon sediments. The adequate use of available algorithms may provide quantitative information on various sediment features, allowing the purposeful selection of cores and subsamples for further investigation