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101.
The standard thermodynamic properties at 25°C, 1 bar (ΔG
fo, ΔH
fo, S
o, C
Po, V
o, ω) and the coefficients of the revised Helgeson–Kirkham–Flowers equations of state were evaluated for several aqueous complexes
formed by dissolved metals and either arsenate or arsenite ions. The guidelines of Shock and Helgeson (Geochim Cosmochim Acta
52:2009–2036, 1988) and Sverjensky et al. (Geochim Cosmochim Acta 61:1359–1412, 1997) were followed and corroborated with alternative approaches, whenever possible. The SUPCRT92 computer code was used to generate
the log K of the destruction reactions of these metal–arsenate and metal–arsenite aqueous complexes at pressures and temperatures required
by the EQ3/6 software package, version 7.2b. Apart from the AlAsO4o and FeAsO4o complexes, our log K at 25°C, 1 bar are in fair agreement with those of Whiting (MS Thesis, Colorado School of Mines, Golden, CO, 1992). Moreover, the equilibrium constants evaluated in this study are in good to fair agreement with those determined experimentally
for the Ca–dihydroarsenate and Ca–hydroarsenate complexes at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) and for Fe(III)–hydroarsenate complex at 25°C (Raposo et al., J Sol Chem 35:79–94, 2006), whereas the disagreement with the log K measured for the Ca–arsenate complex at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) might be due to uncertainties in this measured value. The implications of aqueous complexing between dissolved metals and
arsenate/arsenite ions were investigated for seawater, high-temperature geothermal liquids and acid mine drainage and aqueous
solutions deriving from mixing of acid mine waters and surface waters.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
102.
Luigi Tosi Pietro Teatini Laura Carbognin Jane Frankenfield 《Environmental Geology》2007,52(5):889-898
The paper deals with the implementation of a levelling and Global Positioning System (GPS) network to control land subsidence
in the coastal area north of the Venice Lagoon. About 480 km of levelling lines with 527 benchmarks, 45 of which suited for
Differential GPS measurements, were established in 2004. A complete survey of the net was carried out in 2004 soon after its
establishment. The 2004 records have been compared with previous scattered data obtained by the use of levelling surveys,
DGPS and SAR interferometry. The results show a trend in land settlement that increases from the lagoon margin to the north
and jeopardize the Venice coastland. Groundwater withdrawals for domestic, agricultural, and health spas uses, peat oxidation
of reclaimed marshlands for farming, natural consolidation of the Holocene deposits, and tectonics of the pre-Quaternary basement
are the causes of land subsidence in the study area. Since most of the area lies below the mean sea level and on account of
the expected sea level rise due to global change, a detailed monitoring of land displacements in the near future will be of
paramount importance to plan necessary works for coastland protection. 相似文献
103.
Luigi Folco Massimo D'Orazio Alessandro Burroni 《Meteoritics & planetary science》2006,41(8):1183-1198
Abstract— The Frontier Mountain (FRO) 93001 meteorite is a 4.86 g fragment of an unshocked, medium‐ to coarse‐grained rock from the acapulcoite‐lodranite (AL) parent body. It consists of anhedral orthoenstatite (Fs13.3 ± 0.4Wo3.1 ± 0.2), augite (Fs6.1 ± 0.7Wo42.3 ± 0.9; Cr2O3 = 1.54 ± 0.03), and oligoclase (Ab80.5 ± 3.3Or3.1 ± 0.6) up to >1 cm in size enclosing polycrystalline aggregates of fine‐grained olivine (average grain size: 460 ± 210 μm) showing granoblastic textures, often associated with Fe,Ni metal, troilite, chromite (cr# = 0.91 ± 0.03; fe# = 0.62 ± 0.04), schreibersite, and phosphates. Such aggregates appear to have been corroded by a melt. They are interpreted as lodranitic xenoliths. After the igneous (the term “igneous” is used here strictly to describe rocks or minerals that solidified from molten material) lithology intruding an acapulcoite host in Lewis Cliff (LEW) 86220, FRO 93001 is the second‐known silicate‐rich melt from the AL parent asteroid. Despite some similarities, the silicate igneous component of FRO 93001 (i.e., the pyroxene‐plagioclase mineral assemblage) differs in being coarser‐grained and containing abundant enstatite. Melting‐crystallization modeling suggests that FRO 93001 formed through high‐degree partial melting (≥35 wt%; namely, ≥15 wt% silicate melting and ?20 wt% metal melting) of an acapulcoitic source rock, or its chondritic precursor, at temperatures ≥1200 °C, under reducing conditions. The resulting magnesium‐rich silicate melt then underwent equilibrium crystallization; prior to complete crystallization at ?1040 °C, it incorporated lodranitic xenoliths. FRO 93001 is the highest‐temperature melt from the AL parent‐body so far available in laboratory. The fact that FRO 93001 could form by partial melting and crystallization under equilibrium conditions, coupled with the lack of quench‐textures and evidence for shock deformation in the xenoliths, suggests that FRO 93001 is a magmatic rock produced by endogenic heating rather than impact melting. 相似文献
104.
Luigi Burlini 《Surveys in Geophysics》1994,15(5):593-617
A model for the calculation of a representative complete elastic tensor of a geologic body is presented here, in order to fill the gap between the small scale sample and the complex structural and lithological association of a geologic body, which may be of the same large scale as the wavelength used on the seismic survey. The major problems arising during the modelling are discussed, namely the representativity of a suite of hand samples and the evaluation of the volume fraction of the different lithologies comprising a formation. An application example is presented of a metapelitic sequence spanning the tectonic boundary of the Ivrea-Verbano zone with the Serie dei Laghi in Valle Cannobina (N. Italy). It is shown that the effective formation anisotropy is drastically reduced relative to that of hand samples when the structure is averaged over a large area, except for the sheared and mylonitic sub-areas comprising the tectonic contact zone (the Cossato-Mergozzo-Brissago- and Pogallo lines). In these subareas the effective anisotropy is slightly reduced (a few points of a percent) from the hand sample scale to that of the geologic formation. Moreover, because the polarization of the fastest shear wave and the plane of maximum shear wave splitting of the most common crustal rock types coincide with the foliation, there is an opportunity to infer the structure of deep rock formations from teleseismic shear waves. 相似文献
105.
106.
107.
Adriana Giangrande Margherita Licciano Roberto Schirosi Luigi Musco Loredana Stabili 《Marine Ecology》2014,35(1):36-45
In the marine environment, sessile invertebrates have developed an impressive array of mechanisms to avoid predation, bacterial exploitation, and epibiotic overgrowth. In the present study we investigated several defensive strategies adopted by six sabellids: the hard bottom species Sabella spallanzanii (Gmelin, 1791), Branchiomma luctuosum Grube, 1869, Branchiomma bairdi (McIntosh, 1885), and Sabellastarte spectabilis (Grube, 1878), and the soft bottom species Myxicola infundibulum (Renier, 1804), and Megalomma lanigera (Grube, 1846), which have different morphological characteristics and geographical distribution. We examined and compared some defensive features such as branchial crown toughness, tube structure and strength, amount of released mucus, and antibacterial lysozyme‐activity in the mucus. The investigated species utilize a combination of defence and deterrence strategies that seems to be related to the colonized habitat. Tube strength was, higher in the hard bottom species compared with the soft bottom ones, where the tubes are generally buried and protected within the sediment. Branchial crown appeared stronger and resistant in hard bottom species, except for S. spallanzanii, which is the species showing the strongest tube. Sabella spallanzanii, M. infundibulum and S. spectabilis secreted high amount of mucus with high lysozyme‐like activity. By contrast, B. luctuosum, B. bairdi, and M. lanigera produced low amounts of mucus exerting lower antibacterial activity. 相似文献
108.
Daniela Mele Roberto Sulpizio Pierfrancesco Dellino Luigi La Volpe 《Bulletin of Volcanology》2011,73(3):257-278
New volcanological studies allow reconstruction of the eruption dynamics of the Pomici di Mercato eruption (ca 8,900 cal.
yr B.P.) of Somma-Vesuvius. Three main Eruptive Phases are distinguished based on two distinct erosion surfaces that interrupt
stratigraphic continuity of the deposits, indicating that time breaks occurred during the eruption. Absence of reworked volcaniclastic
deposits on top of the erosion surfaces suggests that quiescent periods between eruptive phases were short perhaps lasting
only days to weeks. Each of the Eruptive Phases was characterised by deposition of alternating fall and pyroclastic density
current (PDC) deposits. The fallout deposits blanketed a wide area toward the east, while the more restricted PDC deposits
inundated the volcano slopes. Eruptive dynamics were driven by brittle magmatic fragmentation of a phonolitic magma, which,
because of its mechanical fragility, produced a significant amount of fine ash. External water did not significantly contribute
either to fragmentation dynamics or to mechanical energy release during the eruption. Column heights were between 18 and 22 km,
corresponding to mass discharge rates between 1.4 and 6 × 107 kg s−1. The estimated on land volume of fall deposits ranges from a minimum of 2.3 km3 to a maximum of 7.4 km3. Calculation of physical parameters of the dilute pyroclastic density currents indicates speeds of a few tens of m s−1 and densities of a few kg m−3 (average of the lowermost 10 m of the currents), resulting in dynamic pressures lower than 3 kPa. These data suggest that
the potential impact of pyroclastic density currents of the Pomici di Mercato eruption was smaller than those of other Plinian
and sub-Plinian eruptions of Somma-Vesuvius, especially those of 1631 AD and 472 AD (4–14 kPa), which represent reference
values for the Vesuvian emergency plan. The pulsating and long-lasting behaviour of the Pomici di Mercato eruption is unique
in the history of large explosive eruptions of Somma-Vesuvius. We suggest an eruptive scheme in which discrete magma batches
rose from the magma chamber through a network of fractures. The injection and rise of the different magma batches was controlled
by the interplay between magma chamber overpressure and local stress. The intermittent discharge of magma during a large explosive
eruption is unusual for Somma-Vesuvius, as well as for other volcanoes worldwide, and yields new insights for improving our
knowledge of the dynamics of explosive eruptions. 相似文献
109.
New geochemical data on cosmic spherules (187 major element, 76 trace element, and 10 oxygen isotope compositions) and 273 analyses from the literature were used to assess the chemical diversity observed among glass cosmic spherules with chondritic composition. Three chemical groups of glass spherules are identified: normal chondritic spherules, CAT-like spherules (where CAT refers to Ca-Al-Ti-rich spherules), and high Ca-Al spherules. The transition from normal to high Ca-Al spherules occurs through a progressive enrichment in refractory major elements (on average from 2.3 wt.% to 7.0 wt.% for CaO, 2.8 wt.% to 7.2 wt.% for Al2O3, and 0.14 wt.% to 0.31 wt.% for TiO2) and refractory trace elements (from 6.2 μg/g to 19.3 μg/g for Zr and 1.6CI-4.3CI for Rare Earth Elements-REEs) relative to moderately refractory elements (Mg, Si) and volatile elements (Rb, Na, Zn, Pb). Based on a comparison with experimental works from the literature, these chemical groups are thought to record progressive heating and evaporation during atmospheric entry. The evaporative mass losses evaluated for the high Ca-Al group (80-90%) supersede those of the CAT spherules which up to now have been considered as the most heated class of stony cosmic spherules. However, glass cosmic spherules still retain isotopic and elemental evidence of their source and precursor mineralogy. Four out of the 10 normal and high Ca-Al spherules analysed for oxygen isotopes are related to ordinary chondrites (δ18O = 13.2-17.3‰ and δ17O = 7.6-9.2‰). They are systematically enriched in Ni and Co (Ni = 24-500 μg/g) with respect to spherules related to carbonaceous chondrites (Ni < 1.2 μg/g, δ18O = 13.1-28.0‰ and δ17O = 5.1-14.0‰). REE abundances in cosmic spherules, which are not fractionated according to parent body or atmospheric entry heating, can then be used to unravel the precursor mineralogy. Spherules with flat REE pattern close to unity when normalized to CI are the most abundant in our dataset (54%) and likely derive from homogeneous, fine-grained chondritic precursors. Other REE patterns fall into no more than five categories, a surprising reproducibility in view of the mineralogical heterogeneity of chondritic lithologies at the micrometeorite scale. 相似文献
110.
Giancarlo Benettin Luigi Galgani Antonio Giorgilli 《Celestial Mechanics and Dynamical Astronomy》1985,37(1):1-25
In the present paper we give a proof of Nekhoroshev's theorem, which is concerned with an exponential estimate for the stability times in nearly integrable Hamiltonian systems. At variance with the already published proof, which refers to the case of an unperturbed Hamiltonian having the generic property of steepness, we consider here the particular case of a convex unperturbed Hamiltonian. The corresponding simplification in the proof might be convenient for an introduction to the subject. 相似文献