Pollution effects of the Tuy River on the central Venezuelan coast: Anthropogenic organic compounds and heavy metals in Tivela mactroidea     

Rudolf Jaffe  Ivan Leal  Jose Alvarado  Piero Gardinali  Jos Sericano 《Marine pollution bulletin》1995,30(12):820-825

Bivalve samples were collected at seven sampling stations located between the town of Machurucuto and the Bay of Higuerote, Venezuela, covering approximately 70 km of coastline. Samples were collected both east and west of the Tuy River mouth, which has a plume known to move in a north-westerly direction. Petroleum hydrocarbons, both aliphatic (n-alkanes and UCM) and polyaromatic (PAHs), were detected and quantified in the samples. These hydrocarbons were found to be primarily derived from fossil fuels. Halogenated organics consisted mostly of polychlorinated biphenyls (PCBs) and some chlorinated pesticides, primarily of the DDT group. Heavy metals such as Pb, Cu, Ni, Zn, Cr and Cd were analysed in the samples. The results clearly show the influence of the Tuy River plume on the water quality of the coastal zone, particularly that located west of the river mouth. One sampling station, located just east of the river mouth, also showed significant influence from the river plume.  相似文献   

The Republic of Slovenia —geographical constants of the new Central-European state     

Ivan Gams Dr. 《GeoJournal》1991,24(4):331-340

The territory of the youngest European state is crossed by strategically important passes, the lowest in the entire Alps, leading from the Danubian basin to the Mediterranean (Italy). Thus, the Slovenes had been under cultural, civilization and political domination of centers from these two parts of Europe all until 1918. Because the mountanous land forms, dissected also by valleys and basins, were prone to processes of diffucion rather than fusion, the Slovenians became a national and political subject of their own as late as 19th C. From 1918 to 1990 they were joined with Yugoslavia, a SE European state, and learnt to their cost all the differences between the cultures of W and Central Europe on the one hand, and SE and E Europe and the Near East on the other. Hence the plebiscite decision by the nation for an independent state.  相似文献   

Kinematic inversion for qP- and qS-waves in inhomogeneous hexagonally symmetric structures     

Ji&#;í Jech  Ivan P&#;en&#;ík 《Geophysical Journal International》1992,108(2):604-612

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Geography at Charles University,Prague, Czechoslovakia*     

Ivan Bi ík 《The Professional geographer》1992,44(4):469-472

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Thermochemistry of the new silica polymorph moganite     

Ivan Petrovic  Peter J. Heaney  Alexandra Navrotsky 《Physics and Chemistry of Minerals》1996,23(2):119-126

Samples of microcrystalline silica varieties containing variable amounts of the new silica polymorph moganite (up to R~82 wt.%) have been studied by a combination of high temperature solution calorimetry using lead borate (2 PbO · B₂O₃) solvent and transposed temperature drop calorimetry near 977 K, in order to investigate the thermochemical stability of this new silica mineral. The enthalpy of solution at 977 K and the heat content (H₉₇₇ — H₂₉₈) of “pure” moganite phase were estimated to be -7.16 ± 0.35 kJ/mol and 43.62 ± 0.50 kJ/mol, respectively. The standard molar enthalpy of formation is-907.3 ± 1.2 kJ/mol. Thus, calorimetry strongly supports results of previous X-ray and Raman spectroscopic studies that moganite is a distinct silica polymorph. Its thermochemical instability relative to quartz at 298 K of 3.4 ± 0.7 kJ/mol is marginally higher than those of cristobalite and tridymite. Structurally, this instability may be related to the presence of distorted 4-membered rings of SiO₄ tetrahedra, which are not found in the quartz structure. The metastability relative to quartz may also explain the apparent scarcity of moganite in altered rocks and in rocks that are older than 130 my.  相似文献   

Chemical and isotopic constraints on water/rock interactions at the Lost City hydrothermal field, 30°N Mid-Atlantic Ridge     

Dionysis I. Foustoukos  Ivan P. Savov  David R. Janecky 《Geochimica et cosmochimica acta》2008,72(22):5457-5474

Low temperature vent fluids (<91 °C) issuing from the ultramafic-hosted hydrothermal system at Lost City, 30°N Mid-Atlantic Ridge, are enriched in dissolved volatiles (H₂,CH₄) while attaining elevated pH values, indicative of the serpentization processes that govern water/rock interactions deep in the oceanic crust. Here, we present a series of theoretical models to evaluate the extent of hydrothermal alteration and assess the effect of cooling on the systematics of pH-controlled B aqueous species. Peridotite-seawater equilibria calculations indicate that the mineral assemblage composed of diopside, brucite and chrysotile likely dictates fluid pH at moderate temperature serpentinization processes (<300 °C), by imposing constraints on the aCa⁺⁺/a²H⁺ ratios and the activity of dissolved SiO₂. Based on Sr abundances and the ⁸⁷Sr/⁸⁶Sr isotope ratios of vent fluids reported from Lost City, estimated water/rock mass ratios (w/r = 2-4) are consistent with published models involving dissolved CO₂ and alkane concentrations. Combining the reported δ¹⁸O values of vent fluids (0.7‰) with such w/r mass ratios, allows us to bracket subseafloor reaction temperatures in the vicinity of 250 °C. These estimates are in agreement with previous theoretical studies supporting extensive conductive heat loss within the upflow zones. Experimental studies on peridotite-seawater alteration suggest that fluid pH increases during cooling which then rapidly enhances boron removal from solution and incorporation into secondary phases, providing an explanation for the highly depleted dissolved boron concentrations measured in the low temperature but alkaline Lost City vent fluids. Finally, to account for the depleted ¹¹B composition (δ¹¹B ∼25-30‰) of vent fluids relative to seawater, isotopic fractionation between tetrahedrally coordinated aqueous boron species with BO₃-bearing mineral sites (e.g. in calcite, brucite) is proposed.  相似文献   

“Grey swan” storm surges pose a greater coastal flood hazard than climate change     

Horsburgh  Kevin  Haigh  Ivan D.  Williams  Jane  De Dominicis  Michela  Wolf  Judith  Inayatillah  Addina  Byrne  David 《Ocean Dynamics》2021,71(6-7):715-730

Ocean Dynamics - In this paper, we show that over the next few decades, the natural variability of mid-latitude storm systems is likely to be a more important driver of coastal extreme sea levels...  相似文献   

Understanding a coastal flood event: the 10th March 2008 storm surge event in the Solent, UK     

Matthew P. Wadey  Robert J. Nicholls  Ivan Haigh 《Natural Hazards》2013,67(2):829-854

Extreme sea-level events (e.g. caused by storm surges) can cause coastal flooding, and considerable disruption and damage. To understand the impacts or hazards expected by different sea levels, waves and defence failures, it is useful to monitor and analyse coastal flood events, including generating numerical simulations of floodplain inundation. Ideally, any such modelling should be calibrated and validated using information recorded during real events, which can also add plausibility to synthetic flood event simulations. However, such data are rarely compiled for coastal floods. This paper demonstrates the capture of such a flood event dataset, and its integration with defence and floodplain modelling to reconstruct, archive and better understand the regional impacts of the event. The case-study event comprised a significant storm surge, high tide and waves in the English Channel on 10 March 2008, which resulted in flooding in at least 37 distinct areas across the Solent, UK (mainly due to overflow and outflanking of defences). The land area flooded may have exceeded 7 km², with the breaching of a shingle barrier at Selsey contributing to up to 90 % of this area. Whilst sea floods are common in the Solent, this is the first regional dataset on flood extent. The compilation of data for the validation of coastal inundation modelling is discussed, and the implications for the analysis of future coastal flooding threats to population, business and infrastructure in the region.  相似文献   

Rhodope and Vardar: the metamorphic and the olistostromic paired belts related to the Cretaceous subduction under Europe     

Ivan Zagorchev 《Geodinamica Acta》2013,26(1):55-59

In the Gondwanian Moesia Plate and Balkanid terranes, accreted to the Palaeo-Europe during the Palaeozoic, the Late Permian—Early Triassic unconformity and the Triassic system are known only from deep boreholes. In the Chiren, Veslets and Golyamo Peshtene regions (Northern Bulgaria), an Early Triassic igneous activity results from eleven drills.

Trachytes, outpoured from sub aerial to shallow sea submarine vents, and later basalt breccias emplaced in shallow water conditions, represent the bimodal volcanic products.

The transitional anorogenic features of the volcanism are consistent with the extensional regime evidenced by the progressively subsiding depositional environment. The extensional Triassic event corresponds to development of branches of a composite rift system, propagating from the Karakaya basin to separate the Moesia with Balkanids p.p. and the Istanbul block to the North, from the Serbian— Macedonian—Thracian microplate with Balkanid p.p. to the south.  相似文献   

The 2dF Galaxy Redshift Survey: the nature of the relative bias between galaxies of different spectral type     

Edward Conway  Steve Maddox  Vivienne Wild  John A. Peacock  Ed Hawkins  Peder Norberg  Darren S. Madgwick  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Bryn Jones  Ofer Lahav  Ian Lewis  Stuart Lumsden  Will Percival  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2005,356(2):456-474

We present an analysis of the relative bias between early- and late-type galaxies in the Two-degree Field Galaxy Redshift Survey (2dFGRS) – as defined by the η parameter of Madgwick et al., which quantifies the spectral type of galaxies in the survey. We calculate counts in cells for flux-limited samples of early- and late-type galaxies, using approximately cubical cells with sides ranging from 7 to  42 h ⁻¹ Mpc  . We measure the variance of the counts in cells using the method of Efstathiou et al., which we find requires a correction for a finite volume effect equivalent to the integral constraint bias of the autocorrelation function. Using a maximum-likelihood technique we fit lognormal models to the one-point density distribution, and develop methods of dealing with biases in the recovered variances resulting from this technique. We then examine the joint density distribution function,   f (δ_E, δ_L)  , and directly fit deterministic bias models to the joint counts in cells. We measure a linear relative bias of ≈1.3, which does not vary significantly with ℓ. A deterministic linear bias model is, however, a poor approximation to the data, especially on small scales  (ℓ≤ 28  h ⁻¹ Mpc)  where deterministic linear bias is excluded at high significance. A power-law bias model with index   b ₁≈ 0.75  is a significantly better fit to the data on all scales, although linear bias becomes consistent with the data for  ℓ≳ 40  h ⁻¹ Mpc  .  相似文献