Mercury contamination in Marano Lagoon (Northern Adriatic sea,Italy): Source identification by analyses of Hg phases

Total Hg concentrations and Hg speciation were determined in bottom sediments of Marano lagoon to investigate the consequences of Hg phases on fish farms and shellfish cultivation areas. Mercury phases were separated into cinnabar (HgS) and non-cinnabar compounds, via a thermo-desorption technique, in surface and core sediments; both of which had been contaminated by industrial wastes and mining activity residues. The former are due to an industrial complex, which has been producing cellulose, chlor-alkali and textile artificial fibres since 1940. Processing and seepage wastewaters, which were historically discharged into the Aussa-Corno river system and therefore into the lagoon, have been significantly reduced since 1984 due to the construction of wastewater treatment facilities. The second source is the Isonzo River, which has been the largest contributor of Hg into the northern Adriatic Sea since the 16th century due to Hg mining at the Idrija mine (western Slovenia). Red cinnabar (HgS) derived from the mining area is mostly stable and insoluble under current environmental conditions. In contrast, organically bound Hg, such as Hg bound to humic acids, has the potential to be transformed into bioavailable Hg compounds (for example, methylmercury). The presence of the two Hg forms permitted each Hg source to be quantified. It also allowed the areas with the highest risk of Hg contamination from Hg-rich sediment to be identified; thus potentially avoiding the transfer of Hg from the sediment into the water column and eventually into living biota. The results show that Hg Enrichment Factors in bottom sediments exceed values of 10 and cinnabar dominates the central sector near the main tidal channel where tidal flux is more effective. Non-cinnabar compounds were found to be enriched in fine grained material and organic matter. In fact, up to 98% of total Hg at the Aussa-Corno river mouth and in the inner margin of the basin occurred in an organic form. This evidence, combined with the high contents of total Hg (4.1–6.6 μg g⁻¹ and EF > 10) measured in surface sediments, suggest that Hg in Marano lagoon is involved in biogeochemical transformations (e.g., methylation).     

New insights on late Quaternary palaeogeographic setting in the Northern Adriatic Sea (Italy)

Sedimentological, geochemical and micropalaeontological data from sediment cores in the northwestern Adriatic Sea were obtained to reconstruct the stratigraphic framework and palaeogeographic setting during the last post‐glacial sea‐level rise (14000–6000 yr BP). Four lithostratigraphic units were identified: (a) distal plain deposits (>14000 yr BP), submerged during the first phases of marine ingression; (b) coastal lagoon system; (c) barrier‐lagoon system, which is dated back to between 10019 ± 61 and 10228 ± 174 cal. yr BP from ¹⁴C dating on peat and shell remains; (d) marine prodelta deposits (<5500 yr BP). Geochemical data allow the identification of three distinct sediment sources: River Po, River Adige and Eastern Alpine rivers characterised by decreasing Ni/Mg ratios (50–70, 8–15 and 5–10, respectively) and Ba/Al ratios of 45–55, 55–65 and 35–45, respectively. The three sources display different relative abundances in time. During the Lateglacial, the Po is the main sediment source for the southern cores, whereas the Eastern Alps and the River Adige are the main sediment sources for the northern cores. This suggests a northern position of the Po River bed compared to previous studies. Coastal drowning led to a homogenization of the provenance signal within the sediments. Only after the marine transgression does a River Po signal appear in the northern cores. At the same time, in the southern cores the signal of Eastern Alpine rivers becomes stronger. Transgressive barrier‐lagoon and recent sediments do not display a predominant signal for provenance indicators. Copyright © 2008 John Wiley & Sons, Ltd.     

Numerical simulation of Holocene depositional wedge in the southern Po Plain-northern Adriatic Sea (Italy)

In the last 10 kyr BP, a coastal depositional wedge formed along the southern Po Plain margin. Shoreline regression accelerated abruptly in the Iron Age, and especially in the last 2 kyr, due to the increased woodland removal on the Apennines. The deposition of the Holocene sedimentary wedge is simulated here, along four coast-tranversal transects, using a finite-element two-dimension mathematical model. The model was constrained using the present topographic surface, the maximum flooding line of the Holocene transgression, architecture and texture of depositional wedge, the location of coastlines, aeolian dunes and ancient offshore delta-sand. The sediment volume required to calibrate the simulations along the sections ranges from about 165,000–870,000 m³ m⁻¹; the maximum tectonic subsidence varies from 0.1 to 0.7 mm yr⁻¹. The minimum sand amount required by the model to stop the accelerated erosion of the Cervia beach is about five times the one employed in recent (April 2002) recovery works.     

Temporal Variation in the Trophic Levels of Secondary Consumers in a Mediterranean Coastal Lagoon (Cabras Lagoon,Italy)

Trophic levels (TLs) of fish were estimated on three sampling dates (March, May, and August 2006) for different fish sizes in the Cabras Lagoon (Sardinia, Italy). A temporal TL variation for Atherina boyeri, Gobius niger, and Engraulis encrasicolus was observed. In March and May, the TL ranged from 3.3 to 3.4, characterizing these species as secondary consumers, while in August, this range moved to between 3.7 and 3.8, indicating a TL shift towards tertiary consumers. For Liza ramada, TL was consistently lower in small individuals (mean TL 2.5) than in larger individuals (mean TL 3.0). Increased TL of the fish species A. boyeri, G. niger, and E. encrasicolus in August was consistent with the seasonal changes in the macrobenthic assemblage in this system, with a dominance of primary consumers (benthic deposit feeders) in winter–spring and a dominance of secondary consumers (the nereidids Alitta succinea and Hediste diversicolor) in summer. These fish species took advantage of the high availability of nereidids leading to a rise in their TL values. Furthermore, the increase of TL with size of L. ramada, the most economically valuable fish species in the Cabras Lagoon, indicated an ontogenetic diet shift, the juveniles being omnivorous, while the adults being secondary consumers. We conclude that variability in the trophic levels of fish due to species traits, ontogenetic diet shifts, and variation in prey availability should be taken into account to further understand the food web structure of coastal lagoons.     

Heavy metals in sediments from different environments of a northern Adriatic Sea area,Italy

Sediments from different environments of an area directly affected by the discharge of the Po River and 13 other minor rivers have been studied. Three main sources of metals and several distribution mechanisms can be identified. Concentration profiles of metals in a core allow one to establish background levels of finegrained sediments for Cd, Hg, Pb, and Zn Seabed sediments do not appear to be very polluted, mainly because of desorption and dilution processes     

The Montecristo monzogranite (Northern Tyrrhenian Sea,Italy): a collisional pluton in an extensional setting

The Montecristo monzogranite (MM) is a near-circular peraluminous monzogranite pluton occupying the entire 10 km² of Montecristo Island. Outcrops of country rock are scarce, and are mainly roof pendants of metagabbros and calcsilicate hornfels of the Apenninic ophiolite sequence. Emplacement of the pluton (Rb–Sr age=7·1±0·2 Ma), following the early Miocene onset of continental collision, occurred during an extensional phase which migrated eastward via a combined process of subduction–delamination. The MM rocks are strongly porphyritic, the assemblage being composed of alkali-feldspar, quartz, plagioclase (all occurring as mega- or phenocrysts), biotite and minor cordierite. Accessory minerals include tourmaline, apatite, zircon, ilmenite, allanite, monazite, rutile and hellandite. Reconstructed crystallization histories for the mineral phases reveal a polybaric crystallization starting at about 5 kb. Textural variations of MM occur in sharp contact with each other; darker types often form globular masses containing fewer megacrysts and more abundant mafic microgranular enclaves. Geochemical, isotopic and petrographic data indicate that the MM magma was produced by anatectic melting of an intermediate to deep pelitic crustal source. On the basis of the geochemical and mineralogical characteristics of the enclaves, modification of their parent magma occurred by crystal fractionation coupled with mixing and mingling of components from the MM magma. The limited geochemical variation in MM is interpreted as due to crystal fractionation processes during the magma's ascent. Younger porphyritic dykes with more potassic and alkaline affinities cut the pluton; these dykes are concentrated in a major fracture zone and are associated with contemporaneous pseudotachylites. © 1997 John Wiley & Sons, Ltd.     

New insights on diapirism in the Adriatic Sea: the Tremiti salt structure (Apulia offshore,southeastern Italy)

The reinterpretation of public seismic profiles in the Adriatic offshore of Gargano (Apulia, southern Italy) allowed the detection of a kilometre‐scale salt‐anticline, the Tremiti diapir, within the larger Tremiti Structure. This anticline was generated by diapirism of Upper Triassic anhydrites within a thick Mesozoic to Quaternary sedimentary succession. Both internal stratal patterns and shapes of Plio‐Quaternary units, and the occurrence of an angular unconformity between early Tortonian and Pliocene rocks on the Tremiti Islands, suggest that halokinesis began during the late Miocene and is still active today. An ancient extensional SE‐dipping fault, cutting an older Mesozoic low‐amplitude anhydritic ridge, played an important role during salt mobilization, which was promoted by NW‐SE shortening. The diapir grew in the footwall of this fault, causing its upward propagation. In some places, the ancient fault served as a preferential channel for the upward migration of the anhydrites.     

Chernobyl fallout and radionuclide activity in bottom sediments at the River Adige estuary (northern Adriatic Sea, Italy)

The artificial radionuclides ¹³⁷Cs, ¹³⁴Cs and ¹⁰⁶Ru have been determined up to 16 cm deep in two sediment cores collected in March 1988 at the River Adige estuary in the northern Adriatic Sea. Interdependent relations between the properties of the sediment levels and the activity of radionuclides have been investigated using multivariate statistical analysis. The interactions between radiocontaminants and the particulate matter or water phase are discussed during their transfer processes from the river to the estuary and the marine environment. Diffusion phenomena within the sedimentary column have also been considered. The vertical distribution of the artificial radionuclides due to Chemobyl fallout in sediment cores from the River Adige mouth, compared to those from similar estuarine environments in the Adriatic Sea, point out a general rapid accumulation of river-borne solid material in coastal zones of the North Adriatic Sea.     

Jabuka island (Central Adriatic Sea) earthquakes of 2003

We present analyses of one of the strongest earthquake sequences ever recorded within the Adriatic microplate, which occurred near the Jabuka island in the very centre of the Adriatic Sea. The mainshock (29 March 2003, 17:42, M_L=5.5) was preceded by over 150 foreshocks, and followed by many aftershocks, over 4600 of which were recorded on the closest station HVAR (about 90 km to the east). As the epicentre was in the open sea and due to the absence of nearby stations, we were able to confidently locate only 597 events. Hypocentral locations were computed by a grid-search algorithm after seven iterations of refining hypocentres and adjusting station corrections. Epicentres lie in a well-defined area of about 300 km², just to the W and NW of the Jabuka island. The vertical cross-sections reveal that hypocentres dip to the NE, closely matching faults from the Jabuka-Andrija fault system, as identified on the available reflection profiles in the area. The fault-plane solution of the main shock based on the first-motion polarity readings agrees well with the CMT solutions and indicates faulting caused by a S–N directed tectonic pressure, on a reverse, dip-slip fault. This is in very good agreement with the seismotectonic framework of the area. These earthquakes are important as they identify the Jabuka-Andrija fault system as an active one, which can significantly influence seismic hazard on the islands in the central Adriatic archipelago and on the Croatian coast between Zadar and Split. Along with several other sequences which occurred in the last two decades, they force us to change our notion of Adria as nearly aseismic, compact and rigid block. In fact, it turns out that recent seismicity of the Central Adriatic Sea is comparable to the seismicity of several well known earthquake-prone areas in the circum-Adriatic region.     

Evolution of karst in Messinian gypsum (Monferrato,Northern Italy)

In the Tertiary Basin of Piedmont (Northern Italy) a 100-150 m thick Messinian sedimentary succession crops out, composed of pre-evaporitic clays, gypsum beds and post-evaporitic lacustrine-marine fine-grained sediments. In the Monferrato area the thickness of the evaporite sequence is highly variable (0-140 m) due to an important erosion surface formed at the end of the evaporite cycle and carved in the gypsum beds. Epigenic caves probably formed during this short intra-Messinian phase of emersion. Cave sediments contain benthonic and planctonic foraminiferal associations ranging in age from Burdigalian to Upper Pliocene. These sediments have probably been deposited in recent times, although it cannot be completely ruled out that they accumulated in caves developed in Upper Messinian times. The formation of the most important caves of this area probably started at the end of the Messinian under epigenic conditions. Possibly, those inherited caves enlarged slowly during the Quaternary in an intrastratal and confined hypogene karst system.     

Benthic Respiration and Inorganic Nutrient Fluxes in the Estuarine Region of Patos Lagoon (Brazil)

In situ benthic flux chamber experiments were performed during late austral spring and early summer of 1996 at eleven nearshore locations in the southern Patos Lagoon, Brazil. The Patos Lagoon is the largest lagoonal system in South America and is a very important nursery ground for local fin fish and shell fish fisheries. These are the first benthic flux measurements made in Patos Lagoon and they suggest that remineralizationwithin the sediments may dominate the recycling of organic matter and nutrients in thelagoon. Measured oxygen benthic fluxes (45–160 mmol m^-2 d^-1) are sufficientto remineralize reported mean water column carbon fixation while phosphate and fixednitrogen benthic fluxes (-0.4–2 and -1.1–4.2 mmol m^-2 d^-1, respectively)are sufficient to supply 100% and 25% of the required water column nutrient demand,respectively. Although of limited areal and temporal coverage, these initial studiesdemonstrate that sediments play a major role in the metabolism and nutrient cyclingwithin the Patos Lagoon Estuary and that future studies of lagoonal biogeochemistrymust consider exchange with the bottom.     

Eclogites in the Northern Dora-Maira Nappe (Western Alps,Italy)

Summary Eclogitised metabasics of early-Alpine age are described from the northern Dora-Maira nappe (internal Pennidic, western Italian Alps), a tectonic element which has become widely known for the coesite-bearing assemblages discovered in its southern part. The P-T conditions inferred in this paper for the eclogitic peak (P = 9–13 kbar, T = 500 ± 50 °C) are much lower than those proposed in the southern Dora-Maira by Chopin (1987) for the coesite-bearing unit. Consequently, only the latter underwent a peculiar early-Alpine evolution at extremely high-pressures and temperatures, while the northern Dora-Maira nappe was eclogitised at P-T conditions comparable to those of the other internal Pennidic units. The post-eclogitic path proposed here for the northern Dora-Maira occurred at isothermal conditions or at slightly increasing temperatures.

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Les éclogites dans la nappe Dora-Maira septentrionale (Alpes Occidentales, Italie)

Resumé Metabasites éclogitiques d'âge éoalpine sont décrites dans la nappe Dora-Maira septentrionale (Pennique interne, Alpes occidentales italiennes), une unité connue pour la découverte de parageneses à coesite dans le secteur meridional. Les conditions P-T de la recrystallization éclogitique proposées dans ce travail (P = 9–13 kbar, T = 500 ± 50 °C) sont plus basses que les conditions suggerées parChopin (1987) pour les roches de l'unité à coesite. D'autre part ces éstimations des pressions et témperatures sont comparables à celles des autres nappes Penniques internes. La trajectoire post-éclogitique proposée içi pour le Dora-Maira septentrional est caracterisée par une diminution de pression à témperatures plus ou moins constantes (ou légèrment croissantes).

     

Seasonal variations of phosphorus species in sediment from the middle Adriatic Sea

Phosphorus (P) species concentrations in 0–2 cm surface sediment layer were investigated monthly from November 2001 to December 2002 at the bay, channel and open sea stations in the middle Adriatic. Modified SEDEX method was used for inorganic phosphorus species determination [P in biogenic (P-FD), authigenic (P-AUT), detrital apatite (P-DET) and P adsorbed on to iron oxides and hydroxides (P–Fe)], and organic phosphorus (P-ORG). P-FD, P-AUT and P-DET concentration ranges (1.5–5.4, 0–2.7 and 0.4–3.4 μmol g⁻¹, respectively) were similar at all stations, and showed no obvious common trend of seasonal changes. P–Fe ranged from 1.9 to 11.9 μmol g⁻¹ with the highest values at bay station and higher seasonal oscillations than other inorganic P forms. P-ORG ranged from 0.3 to 18.7 μmol g⁻¹ with higher concentrations at stations of fine-sized sediments and showed increased concentrations in warm part of the year at all stations. Correlation between concentrations of P–Fe in the surface sediment layer and orthophosphate sediment-water interface concentration gradients at bay and channel stations indicated to P–Fe importance in the orthophosphate benthic flux. For the bay station, linkage between sediment P-ORG and chlorophyll a concentrations, primary production and microzooplankton abundance was established, indicating a 1 month delay of sediment response to production fluctuations in the water column.     

Sedimentation in a disequilibrium river-dominated estuary: the Raša River Estuary (Adriatic Sea, Croatia)

This paper examines sediment transport, sedimentation and properties of suspended matter and sediments in the Ra?a River estuary, a small, rock-bounded, microtidal, low-wave-energy karstic estuary in the north-eastern Adriatic. The Ra?a River is characterized by large variation in water flow and variable load of mineral particles. More than 90% of this load is brought into the estuary as fine-grained suspended matter, consisting of only 24–36% of carbonates, the rest being clays. Sedimentation occurs at the salt wedge, resulting in a prograding estuarine delta. Salt-induced flocculation is the predominant process of sediment deposition. The Ra?a estuary is infilling with sediment, and classifies as a disequilibrium estuary. We propose a modification of Cooper's (1993) classification scheme to include river-dominated, disequilibrium estuaries, with the Ra?a River as an example.     

Late-Quaternary paleoenvironmental evolution of Lesina lagoon (southern Italy) from subsurface data

Integrated sedimentological and micropaleontological (foraminifers and ostracods) analyses of two 55 m long borehole cores (S3 and S4) drilled in the subsurface of Lesina lagoon (Gargano promontory—Italy) has yielded a facies distribution characteristic of alluvial, coastal and shallow-marine sediments. Stratigraphic correlation between the two cores, based on strong similarity in facies distribution and AMS radiocarbon dates, indicates a Late Pleistocene to Holocene age of the sedimentary succession.Two main depositional sequences were deposited during the last 60-ky. These sequences display poor preservation of lowstand deposits and record two major transgressive pulses and subsequent sea-level highstands. The older sequence, unconformably overlying a pedogenized alluvial unit, consists of paralic and marine units (dated by AMS radiocarbon at about 45–50,000 years BP) that represent the landward migration of a barrier-lagoon system. These units are separated by a ravinement surface (RS1). Above these tansgressive deposits, highstand deposition is characterised by progradation of the coastal sediments.The younger sequence, overlying an unconformity of tectonic origin, is a 10 m-thick sedimentary body, consisting of fluvial channel sediments overlain by transgressive–regressive deposits of Holocene age. A ravinement surface (RS2), truncating the transgressive (lagoonal and back-barrier) deposits in core S4, indicates shoreface retreat and landward migration of the barrier/lagoon system. The overlying beach, lagoon and alluvial deposits are the result of mid-Holocene highstand sedimentation and coastal progradation.     

Benthic nutrient fluxes in the intertidal flat within the Changjiang （Yangtze River） Estuary

In an annual cycle from March 2005 to February 2006, benthic nutrient fluxes were measured monthly in the Dongtan intertidal flat within the Changjiang （Yangtze River） Estuary. Except for NH4^＋, there always showed high fluxes from overlying water into sediment for other four nutrients. Sediments in the high and middle marshes, covered with halophyte and consisting of macrofauna, demonstrated more capabilities of assimilating nutrients from overlying water than the low marsh. Sampling seasons and nutrient concentrations in the overlying water could both exert significant effects on these fluxes. Additionally, according to the model provided by previous study, denitrification rates, that utilizing NO3- transported from overlying water （Dw） in Dongtan sediments, were estimated to be from -16 to 193 μmol·h^-1·m^-2 with an average value of 63 μmol·h^-1·m^-2 （n=18）. These estimated values are still underestimates of the in-situ rates owing to the lack of consideration of DN, i.e., denitrification supported by the local NO3^- production via nitrification.     

Benthic foraminifera in a deep-sea high-energy environment: the Moira Mounds (Porcupine Seabight,SW of Ireland)

Cold-water coral ecosystems represent unique and exceptionally diverse environments in the deep-sea. They are well developed along the Irish margin, varying broadly in shape and size. The Moira Mounds, numerous small-sized mounds, are nestled in the Belgica Mound Province (Porcupine Seabight, North-East Atlantic). The investigation of living (Rose Bengal stained) and dead benthic foraminiferal assemblages from these mounds allowed to describe their distribution patterns and to evaluate their response to environmental variability. Quantitative data was statistically treated to define groups of species/genera associated to specific habitats. The Moira Mounds differ from their larger neighbours by the reduced spatial variability of benthic foraminiferal assemblages, living assemblages only distinguishing coral-rich and coral-barren areas. The ecological needs of corals are highlighted by the abundance of Alabaminella weddellensis and Nonionella iridea, phytodetritus-feeding species in coral supporting sediments. Living foraminifera in sediments from the Moira Mounds concentrate in the upper first centimetre. Infaunal species may be affected by bioturbation and/or reworking by the strong currents in the area. Dead foraminiferal assemblages from the Moira Mounds resemble those described for the sandwave facies in adjacent giant mounds, suggesting similar processes in facies deposition.