Trace element distributions in surficial sediments of the northern Tyrrhenian Sea: Contribution to heavy-metal pollution assessment

The trace element distributions in surficial sediment of Tyrrhenian Sea have been investigated as a part of a series of studies on the environmental quality of the area off the Tuscany coast (west-central Italy). This research has focused on the presence of possible contaminated zones; it also provides data for the identification and future monitoring and control of pollution sources. The study of numerous surface sediments and core samples has made it possible to distinguish between heavy-metal enrichments related to natural sources and other anomalies caused by anthropogenic contamination. Over much of the basin, the surface Pb, Cu, Zn, and As contents appear considerably enriched relative to those below 15 cm; among these metals, Pb shows the highest and most widespread enrichment. Only in the case of some coarse-grained sediments close to the mouth of Cecina River it is possible to relate anomalously high Zn contents to natural sources. In all other sampling stations, the enrichments of Pb, Cu, Zn, and As are ascribed to man's influence. The sediment distributions of Co, Cr, and Ni do not seem to be related to anthropogenic activities; rather they mirror influx of materials derived from sources of ophiolitic rock. The distribution of barium shows only two significant positive anomalies, and both are related to natural causes. Concentrations of vanadium are high in a zone close to an important smelting plant; these are thought to be of anthropogenic origin.     

A Parametric Approach for Dealing with Compositional Rounded Zeros

In this work, a parametric approach for replacing data below the detection limit, also known as rounded zeros, in compositional data sets is proposed. Compositional rounded zeros correspond to small proportions of some whole that cannot be reliably detected by the analytical instruments under given operating conditions. This kind of zeros appear frequently in the data collection process in geosciences. They must be treated in an adequate way before some multivariate analysis can be applied. Our procedure results from a modification of the Expectation-Maximization (EM) algorithm and is based on the additive log-ratio transformation. Its coherence with the nature of compositional data and with basic operations in the simplex sample space is checked. Using real data sets, we find that this approach improves other parametric and non-parametric techniques for compositional rounded zeros.     

Carbonate-hosted siliceous crust type mineralization of Carnic Alps (Italy-Austria)

A carbonate-hosted stratabound siliceous crust type (SCT) mineralization (base metal sulphides, barite, fluorite) occurs over large areas of Carnic Alps and Karawanken in the Eastern Alps. It concerns a pervasively silicified lithological unit, up to some tens of metres thick, which caps the unconformity landscapes developed on epicontinental Devonian–Dinantian carbonates. The SCT mineralization is directly overlaid by different transgressive siliciclastic sediments, which range from Lower Carboniferous to Lower Permian. The presence of fragments of the SCT mineralization in the transgressive siliciclastic sediment bounds its whole lithological evolution within a short stratigraphic interval of Lower Carboniferous age. Selected features of the regional and lithostratigraphic setting are discussed. The chemical characterisation is based on the statistical evaluation of compositional data of 581 selected samples. Three significant groups of elements have been distinguished: (1) the hydrological and metasomatically active elements (Si, Ba, F), which show a strong negative correlation amongst themselves and characterise the silica-saturated aqueous solutions; (2) the terrigenous elements (Al₂O₃, K₂O, Fe_tot, TiO₂, B, Be, Ce, La, Nb, V, Y, Zr), which suggest a continental margin environment for silica deposition; (3) the sulphide metals (Cu, Pb, Zn, Ni, Sb, As, Hg, Cd), which define the metalliferous signature of the SCT mineralization.Some consistent, but still debatable genetic aspects of the SCT mineralization are as follow: (1) silica may be supplied by illitization of clay-rich basinal sediments during their diagenesis. δ¹⁸O of microcrystalline quartz ranges from +18.5‰ and +24.6‰ and is very similar to δ¹⁸O of authigenic quartz deriving from diagenetic processes of illitization of clay-rich basinal sequences. (2) The diagenetic evolution of these sediments may trigger off the movement of silica-rich marine pore waters. δ³⁴S of barite ranges from +15.5‰ to +19.3‰ with an average of +17.7‰ and are in good agreement with δ³⁴S of sulphate in ocean waters of Upper Devonian–Lower Carboniferous age. (3) A convective hydrological system, connected with sinsedimentary transtensive tectonics, active in the Carnic Alps since the Frasnian, may be the transport mechanism of aqueous solutions. (4) A weak drop in pH in the dominant carbonate environment represents the conditions for silica precipitation.SCT mineralization, showing persistent, independent and distinct characters, occurs over large areas also in other sites of the Alpine belt and outside Italy and Austria. Therefore, it points to important markers for some sedimentary sequences as well as to a worldwide significant cyclic metallogenic event. It represents a new ore deposit-type within the carbonate-hosted mineralization.     

NO2 total column evolution during the 1989 spring at Antarctica Peninsula

Ground-based visible differential absorption spectrometry during twilight has been used for NO₂ total column observations at the Antarctica Peninsula, Marambio Base (64S, 56W), during the austral spring of 1989 (9 September to 25 November).Results show moderate NO₂ vertical column levels of 1.5 to 2.5×10¹⁵ molec cm^-2 in the morning and 2 to 3×10¹⁵ molec cm^-2 in the evening until middle October, highly modulated by planetary wave activity. From that date until the end of the period, a steady increase occurs which is associated with the rising of lower stratosphere temperature as the vortex weakens, reaching values of 5×10¹⁵ molec cm^-2 in late November, with small a.m.-p.m. differences. NO₂ is found to be positively correlated to both total ozone and 50 hPa temperature during the entire spring. However, when analyzing the departures from linear trends, a highly negative correlation has been observed from day 301 onwards.     

Comparing performance indicators to characterize the water supply to the demands of the Guadiana River basin (Spain)

ABSTRACT

Water indicators and indices are useful tools to assess river basin performance, that is, to measure whether the basin operates satisfactorily under a wide range of possible future demands and hydrological conditions. Spanish regulations assess the performance of water demands by using reliability indicators (RIs), established by law in 2008. This article raises the possibility of updating RIs by comparing them with sustainability indicators (SIs). SIs are widely used for the assessment of river basin performance and several policy scenarios. We applied a water allocation model to the Guadiana River basin in Spain to compare indicators under three scenarios. The study was framed within the science of socio-hydrology, combining the physical environment of a water system with its influence on social aspects. SIs gave better results than RIs when comparing future scenarios. We also propose the introduction of a vulnerability indicator into Spanish regulations.     

Evolution of the Mesozoic Granites in the Xiong''ershan-Waifangshan Region,Western Henan Province,China,and Its Tectonic Implications

Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong'ershan-Waifangshan region in western Henan Province: high-Ba-SrⅠ-type granite emplaced in the early stage (～160 Ma),Ⅰ-type granite in the middle stage (～130 Ma) and anorogenic A-type granite in the late stage (～115 Ma). Geochemical characteristics of the high-Ba-SrⅠ-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New 40Ar/39Ar plateau ages of the early-stage Wuzhangshan granite (156.0±1.1 Ma, amphibole) and middle-stage Heyu granite (131.8±0.7 Ma, biotite) are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A-type granite, Taishanmiao pluton, was emplaced at～115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between～160 Ma and～115 Ma. The genesis of the early- and middle-stageⅠ-type granites could be linked to delamination of subducted lithosphere of the Qiniing orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qiniing -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial 87Sr/86Sr ratios, which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratons.     

Sequence stratigraphy of Holocene incised-valley fills and coastal evolution in the Gulf of Cádiz (southern Spain)

This first sedimentary interpretation of two incised-valley fills in the Gulf of Cádiz (southern Spain), which accumulated during the last fourth-order eustatic cycle in response to fluvial incision, changes of sea level, and correlative deposition, relates the filling of the estuarine basins and their barriers with four regional progradation phases, H₁ to H₄. The cases studied are the wave-dominated Guadalete, and the mixed, tide and wave-dominated Odiel-Tinto estuaries. The sequence boundary is a type-1 surface produced during the lowstand of the Last Glacial period ca. 18 000 ¹⁴C yr BP. No fluvial lowstand deposits were found in the area. Due to rapid transgression the valley fills consist of transgressive and highstand sediments. The maximum landward advance of the estuarine barriers occurred ca. 6500–6000 ¹⁴C yr BP during the maximum of the Flandrian transgression, but there is no evidence of sea level rising appreciably above the present. A large part of the estuaries was filled during H₁ (ca. 6500–4400 ¹⁴C yr BP) but ravinement by shifting tidal inlets destroyed most of the coeval barriers. During the H₂ phase (ca. 4200–2550 ¹⁴C yr BP) sedimentation was favoured by arid conditions and concentrated in the axial estuarine zones and the barriers. Between H₂ and H₃ prevailing winds changed from W to WSW, increasing spit growth to the east and south-east. Progradation of bay-head deltas and flood-plains during H₃ (ca. 2300–800 ¹⁴C yr BP) and H₄ (500 yr ago to the present) further reduced the accommodation space in the largely-filled valleys, and sediment by-passed the estuaries and accumulated in the estuarine barriers as fast-growing spits. Arid conditions and increasing human activity have caused rapid coastal modifications.