1,721,113 research outputs found
Stable isotopic composition of three foraminifera species in ODP Hole 160-963D
No full textCarbon-rich layers exist at both sides of the Mediterranean Sea sedimentary record and are called sapropels and organic rich layers (ORLs), respectively in the eastern and western basins. They have different levels of organic carbon accumulation and seafloor oxygen deprivation. The most recent sapropel and ORL deposition have a different timing, 10.8-6.1 and 14.5-9.0 ka respectively. Here we investigate oxygen isotopic records of three foraminifera species that occupy different habitats within the Sicily Channel water column since ~ 12.0 ka, thus in the sill between the eastern and western Mediterranean basins. These data are ice volume-corrected, to get information on water masses density variability, and are accompanied by benthic foraminifera 13C measurements to establish Sicily Channel seafloor ventilation. Our results, and the comparison with other chronologically well-constrained Mediterranean records, highlight the connection of the two sub-basins due to monsoon activity. The end of the maximum Nile River flooding at ~ 9.2 ka, and eastern Mediterranean seafloor reventilation above 1800-1500 m depth at ~ 8.2 and 7.2 ka, left a clear signature in the intermediate water isotopic record of the Sicily Channel. Concurrently, the western Mediterranean deep water circulation experienced a significant recovery after a long period of slowdown. We argue that African monsoon weakening was transmitted into the western Mediterranean, through the intermediate layer of circulation, where promoted deep water formation and brought oxygen to the seafloor
Tethyan planktic foraminiferal record of the early Eocene hyperthermal events ETM2, H2 and I1 (Terche section, northeastern Italy)
No full textUV‐Solar Photocatalysis for the Simultaneous Removal of Arsenic and Mercury in Washing Solutions from Polluted Marine Sediments
Full text linkAn environmentally sustainable strategy has been developed for simultaneously removing arsenic and mercury from wastewater, potentially coming from washing of polluted marine sediments. Citric acid (CA), a biodegradable chelating agent, forms stable complexes with both metals, which can be extracted from contaminated sediments through ex situ sediment washing. A solar photocatalytic method has been developed to separate toxic metals from wastewater and degrade CA. Increasing the TiO2 photocatalyst load enhances arsenic adsorption under dark conditions. Total arsenic removal is achieved during photocatalytic decontamination using 1000 ppm of TiO2. Fe(III)–hydroxides formed in the presence of Fe(III) further adsorb arsenic. Nearly total arsenic removal is achieved even under seawater conditions and visible light irradiation only. The removal of arsenic in different oxidation states has been successfully demonstrated. The UV–vis/TiO2/CA photocatalytic system has also proven highly effective for mercury removal from wastewater. Although seawater conditions slightly slow the removal process, complete mercury removal is achieved even under visible light irradiation. Finally, a combined photocatalytic approach has been developed for the removal of both arsenic and mercury, achieving 100% removal within few minutes of light irradiation. The reaction mechanism has been depicted based on intermediates and reaction products detected during the photocatalytic process
Global and regional factors responsible for the drowning of the Central Apennine Chattian carbonate platforms
No full textThis work discusses and interprets the factors responsible for the Oligocene–Miocene drowning of the Central Apennine platform deposits, based on facies and stable-isotope analyses of two representative stratigraphic sections. TheMediterranean carbonate platforms were affected during the Oligocene–Miocene boundary by a carbonate production crisis that was induced by global factors and amplified by regional events, such as volcanic activity. The positive δ13C shift observed in the studied sections corresponds to vertical facies changes reflecting the evolution from middle carbonate ramp to outer ramp-hemipelagic depositional environments. This drowning event is recorded not only in the Apennine platforms, but
also in other Mediterranean platforms such as in southern Apulia, Sicily and Malta, and outside the Mediterranean Basin. The ~24–23.5Ma Mi-1 glacial maximum may have had a significant influence on this drowning event because it was associated with high rates of accumulation of continent-derived sediments. The increased continental weathering and runoff sustained high trophic conditions. These probably were a consequence of the Aquitanian–Burdigalian volcanic activity in the Central-WesternMediterranean, that may have led to an increase in nutrient content in seawater and an increase in atmospheric and marine CO2 concentration
Tracing mercury pathways in Augusta Bay (southern Italy) by total concentration and isotope determination
No full textThe mercury (Hg) pollution of sediments is the main carrier of Hg for the biota and,
subsequently, for the local fish consumers in Augusta Bay area (SE Sicily, Italy), a coastal marine
system affected by relevant sewage from an important chlor-alkali factory. This relationship was
revealed by the determination of Mass Dependent (MDF) and Mass Independent Fractionation (MIF) of
Hg isotopes in sediment, fish and human hair samples. Sediments showed MDF but no MIF, while fish
showed MIF, possibly due to photochemical reduction in the water column and depending on the
feeding habitat of the species. Benthic and demersal fish exhibited MDF similar to that of sediments in
which anthropogenic Hg was deposited, while pelagic organisms evidenced higher MDF and MIF due to
photoreduction. Human hair showed high values of δ202Hg (offset of +2.2‰ with respect to the
consumed fish) and Δ199Hg, both associated to fish consumption
The neglected history of oceanic anoxic event 1b: Insights, new data from the Poggio le Guaine section (Umbria-Marche Basin)
No full textMiddle Miocene stepwise climate evolution in the Mediterranean region through high-resolution stable isotopes and calcareous plankton records
No full textThe middle Miocene is marked by a changeover from a warm climatic period (Miocene Climatic Optimum, ~17-14.7 Ma), to a transitional phase (Middle Miocene Climatic Transition), culminating in a cold stage (Icehouse Mode, ~13.8 Ma). This period is associated with a positive excursion of δ13C (“Monterey Excursion”), showing a series of δ13C maxima (CM events) highlighted by cooling peaks in the δ18O values (Mi events). DSDP Site 372 obtained a high-resolution record of the middle Miocene of the western Mediterranean (Balearic Islands), and represents one of the best marine sedimentary records for the considered time interval. In this study, highresolution stable isotope and quantitative calcareous plankton records for the Langhian to the early Serravallian time interval are presented. The stable oxygen and carbon isotope records allowed us to recognize and chronologically frame the Mi and CM events falling between 15.82 and 13.04 Ma. Furthermore, by integrating the stable isotope data with those obtained by the quantitative analyses of the calcareous plankton content, the three-folded climatic and environmental evolution was outlined for the considered time interval in the Mediterranean region. During the first stage (Miocene Climatic Optimum = MCO; from 17 up to 14.55 Ma), an initial warm-surfacewater, oligotrophic, high salinity and restricted environment is followed by an open marine setting (starting from 15.18 Ma) within still warm-surface-water and oligotrophic conditions. The re-opening of the connections between the Mediterranean Sea and the Indian Ocean would have likely triggered this latter environmental change. From 14.55 to 13.75 Ma (second stage; Middle Miocene Climatic Transition; MMCT) an initial (up to 14.05 Ma) temperate-warm-surface-water and eutrophic environment occurred, followed by the onset of warm-surfacewater, oligotrophic and slightly restricted marine conditions. The third stage (Icehouse Mode = IHM; from 13.75 Ma onwards) points to the development of a cold-water, eutrophic, high salinity environment in an open-marine setting
Electrochemical remediation of synthetic and real marine sediments contaminated by PAHs, Hg and As under low electric field values
Full text linkTo date, remediation, protection, and restoration of contaminated sites is a global concern. The current technologies to restore sediments characterized by heterogeneous characteristics, several pollutants, fine grains, and low hydraulic permeability are poorly effective; hence their remediation is still challenging. A promising approach for the sediment's remediation could be the electrochemical route since it is a not-expensive, effective and noninvasive in situ technology. Electrochemical remediation (ER) is commonly studied under relatively high electric fields (E ≥ 1 V cm-1) and using costly processing fluids in a three compartments cell aiming to desorb and transport the contaminants into the processing fluids (secondary dangerous effluent). In this work, contaminated marine sediments were electrochemically treated focusing on the insertion of electrodes directly in the sediments and adopting, for the first time for real sediments, low E values (≤ 0.25 V cm-1) for 4-days period. It was observed that PAHs can be simultaneously transported and degraded in situ preventing the production of a secondary dangerous effluent and reducing the energy consumption. Firstly, clay marine sediments dragged from Capo Granitola Coast (Trapani, Italy) spiked with five PAHs congeners (5PAHs), Hg and As were used as a simplified model matrix and treated to simulate a real case study. A total PAHs removal efficiency of 57% was reached after 96 h of treatment under 0.05 V cm-1. Then, real polluted marine sediments from Augusta Bay (Syracuse) and Bagnoli-Coroglio Bay (Naples) in the southern Italy were treated as real contaminated sediments to be restored, to validate the proposed approach for real cases. A quite good removal efficiency of PAHs was reached after 96 h of electrochemical treatment coupled with a low energetic consumption due to the rather E values adopted. In addition, it was observed that this approach, under the adopted conditions, is unsuitable for the remediation of Hg and As
The response of mid-Cretaceous shallow water carbonate factories to the climatic/oceanographic events: Case study from central-southern Apennines (Italy)
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