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1.
The speciation of Nd(III), Sm(III), and Er(III) in sulfate-bearing solutions has been determined spectrophotometrically at temperatures from 25 to 250 °C and a pressure of 100 bars. The data obtained earlier on the speciation of Nd in sulfate-bearing solutions (Migdisov et al., 2006) have been re-evaluated and corrected using a more appropriate activity model and are compared with the corresponding data for Sm(III) and Er(III) and new data for Nd(III). Based on this comparison, the dominant species in the solution are interpreted to be and , with the latter complex increasing in importance at higher temperature. Equilibrium constants were calculated for the following reactions:
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3.
Recent drilling and sampling of hydrothermal fluids from Long Valley permit an accurate characterization of chemical concentrations and equilibrium conditions in the hydrothermal reservoir. Hydrothermal fluids are thermodynamically saturated with secondary quartz, calcite, and pyrite but are in disequilibrium with respect to aqueous sulfide-sulfate speciation. Hydrothermal fluids are enriched in 18O by approximately 1‰ relative to recharge waters. 18O and Cl concentrations in well cuttings and core from high-temperature zones of the reservoir are extensively depleted relative to fresh rhyolitic tuff compositions. Approximately 80% of the Li and 50% of the B are retained in the altered reservoir rock. Cl mass balance and open-system 18O fractionation models produce similar water-rock ratios of between 1.0 and 2.5 kg kg−1. These water-rock ratios coupled with estimates of reservoir porosity and density produce a minimum fluid residence time of 1.3 ka. The low fluid Cl concentrations in Long Valley correlate with corresponding low rock concentrations. Mass balance calculations indicate that leaching of these reservoir rocks accounts for Cl losses during hydrothermal activity over the last 40 ka. 相似文献
4.
Art R. T. Jonkers 《Geophysical Journal International》2007,169(2):646-658
The technique of bootstrapped discrete scale invariance allows multiple time-series of different observables to be normalized in terms of observed and predicted characteristic timescales. A case study is presented using the SINT2000 time-series of virtual axial dipole moment, which spans the past 2 Myr. It is shown that this sequence not only bears a clear signature of a preferred timescale of about 55.6 Ka, but additionally predicts similar features (of shorter and longer duration) that are actually observed on the timescales of historical secular variation and dipole reversals, respectively. In turn, the latter two empirical sources both predict the characteristic timescale found in the dipole intensity sequence. These communal scaling characteristics suggest that a single underlying process could be driving dynamo fluctuations across all three observed timescales, from years to millions of years. 相似文献
5.
A. T. DeGaetano 《Theoretical and Applied Climatology》1998,60(1-4):151-162
Summary Observational biases in hourly surface wind speed and direction measurements from 41 northeastern U.S. stations are evaluated.
Based on this analysis, a number of consistent wind observation biases are detected which should be considered when using
these data in modeling and other climatological applications. These biases include a preference to report wind speed as a
multiple of either 2 or 5 kt and a similar bias for reporting even, in terms of tens of degrees, wind directions. Temporal
and station-dependent trends in estimating winds less than the starting speed of the anemometer are also evident. Given these
biases, potential inaccuracies in analyses using wind data are illustrated.
In addition, analyses are conducted to identify biases related to archival and summarization practices. In particular, the
comparability of wind climatologies based on varying record lengths is determined. These assessments suggest that at least
nine years of data are required to obtain representative wind frequency tabulations. The potential consequences of using too
small of a record length are also illustrated. To achieve this minimum record length, climatologies can be constructed using
either hourly or 3-hourly observations.
Received February 26, 1996 Revised April 21, 1997 相似文献
6.
Art F White 《Geochimica et cosmochimica acta》1977,41(5):613-625
The coprecipitation of Na and K was experimentally investigated in aragonite. The distribution functions were determined at pH 6.8 and 8.8 over aqueous Na and K concentrations of between 5 × 10?4and 2.0 M and temperatures of between 25 and 75°C.The mole fractions of Na and K in aragonite are related to the aqueous ratios of Na and Ca by a function of the form where C0 and C1 are constants at a given temperature. This equation was derived by a statistical model assuming a heterogeneous energy distribution for the sites of incorporation. The independence of the coprecipitation process from aqueous anion activities suggests that carbonate is the only anionic species in the solid solution. 相似文献
7.
Art. A. Migdisov A.E. Williams-Jones T. Wagner 《Geochimica et cosmochimica acta》2009,73(23):7087-7109
The solubility of REE(III) fluoride solids was determined in fluoride- and chloride-bearing solutions at 150, 200 and 250 °C and saturated water vapor pressure. These experimental data, together with experimental data from previously published studies, were used to evaluate formation constants for chloride- and fluoride-bearing aqueous species of the entire REE(III) group at temperatures up to 300 °C. The data show that the stability of these species differs significantly from that predicted theoretically. For example, contrary to the theoretical predictions, LREEF2+ species are more stable than HREEF2+ species at elevated temperature. The behavior of the chloride-bearing species is similar. Parameters for the Helgeson–Kirkham–Flowers (HKF) equation of state were determined for REEF2+, REECl2+ and REECl2+ complexes using these experimental data and permit calculation of formation constants of these species at conditions not investigated experimentally. These data now permit the mobility of all REE in fluoride- and chloride-bearing hydrothermal systems to be reliably evaluated at intermediate temperatures and pressures. 相似文献
8.
A Temporal Comparison of Drought Impacts and Responses in the New York City Metropolitan Area 总被引：1，自引：0，他引：1
Arthur T. DeGaetano 《Climatic change》1999,42(3):539-560
Climate impact analyses seldom examine temporal changes in the impacts and responses associated with climate anomalies. Newspaper reports, quantitative agricultural and water resource data and a survey of drought sensitive segments of society are used to compare the impacts and responses of a 1995 drought in the New York City metropolitan area to those experienced during five previous droughts. Impacts related to surface water supplies dominated each of the drought periods studied. Over time, however, changes in water consumption habits and available reservoir capacity lead to an increase in impact severity for similar meteorological conditions. To account for these non-climatic influences on water storage, a method to adjust for trends in available reservoir storage and water use is developed and implemented. Once adjusted, a fairly strong (R2 = 70.9%) exponential relationship exists between the minimum reservoir level and Palmer Drought Severity Index experienced during each drought period. Unadjusted levels exhibit a considerably weaker (R2 = 49.0%) relationship. Changes in water consumption and reservoir capacity also influenced the enactment of voluntary and ultimately mandatory water conservation measures. These restrictions were responsible for business and industrial impacts that varied through time as technology evolved and societal attitudes changed. Minor time-dependent changes were also evident in agricultural and wildfire impacts. 相似文献
9.
The speeds of historical cool-season extratropical cyclones along the U.S. east coast, hereafter East Coast Winter Storms
(ECWS), occurring during the period from 1951 to 2006 were computed. Average storm speed was 13.8 ms−1 with stronger storms generally moving faster than weaker storms and faster storms forming during the midwinter months (December–March).
There was no clear trend in ECWS speed during the time period, although considerable season-to-season variability was present.
The monthly and seasonal variations in storm speed could not be attributed to the El Ni?o-Southern Oscillation or North Atlantic
Oscillation (NAO) alone. However, the speed of ECWS was considerably slower when both El Ni?o and the negative phase of NAO
occurred simultaneously. Characteristic patterns in the upper levels of the atmosphere, specifically 300 hPa zonal winds and
500 hPa geopotential heights, were present during periods when ECWS speeds were among the slowest (and separately fastest).
For slow storm speed, these patterns also prevailed during months in which El Ni?o and negative NAO phase occurred. These
patterns were also present during months with extended runs of high oceanic storm surge. This provides a qualitative link
between the atmospheric conditions associated with slow storms and potentially high coastal storm surge impacts. Among the
prime consequences of ECWS speed are extended periods of high storm surge, mainly due to slow-moving storms. The sustained
high tidal levels often lead to substantial damage caused by coastal flooding, overwash, and beach erosion. 相似文献
10.
A. Goineau C. Fontanier F.J. Jorissen B. Lansard R. Buscail A. Mouret P. Kerhervé S. Zaragosi E. Ernoult C. Artéro P. Anschutz E. Metzger C. Rabouille 《Journal of Sea Research》2011,65(1):58-75
In this paper, we investigate the ecology of live (rose Bengal stained) benthic foraminifera collected at 20 stations ranging from 15 to 100 m depth in the Rhône prodelta (Gulf of Lions, NW Mediterranean). These sites were sampled in September 2006, five months after the Rhône River annual flood. Statistical analyses based on foraminiferal communities (> 150 μm) divide our study area into six main biofacies directly related to environmental conditions. Miliolid species are abundant in the relict prodeltaic lobe which is characterised by sand with low organic matter content. Close to the river mouth, the limited oxygen penetration in the sediment combined with important hydro-sedimentary processes constitute stressful conditions for foraminiferal faunas dominated by opportunistic species (e.g. Leptohalysis scottii). With increasing distance from the river mouth, foraminiferal faunas (e.g. Nonionella turgida, Eggerella scabra) adapted to thrive in sediments enriched in Rhône-derived organic matter under more stable hydro-sedimentary conditions appear. In the distal part of the Rhône River influence, benthic species (e.g. Valvulineria bradyana, Textularia agglutinans) living in fine sediment enriched in both continental and marine organic compounds emerge. At the deepest stations located in the south-eastern part of our study area, benthic foraminiferal faunas (e.g. Bulimina aculeata, Melonis barleeanus, Bigenerina nodosaria) are highly diverse, underlining stable environmental conditions characterised by marine-derived organic matter supplies and relatively deep oxygen penetration depth in the sediment. We also compare foraminiferal faunas sampled in September 2006 with communities sampled in June 2005, one month after the Rhône River annual flood (Mojtahid et al., 2009). This comparison suggests that opportunistic species (e.g. B. aculeata, Cassidulina carinata, V. bradyana) have responded to organic matter inputs related to marine primary production in June 2005. 相似文献