Characterization of fluid inclusions from mineralized pegmatites of the Damara Belt,Namibia: insight into late-stage fluid evolution and implications for mineralization     

Ashworth  Luisa  Kinnaird  Judith Ann  Nex  Paul Andrew Martin  Erasmus  Rudolph Marthinus  Przybyłowicz  Wojciech Józef 《Mineralogy and Petrology》2018,112(6):753-765

Mineralogy and Petrology - Mineralized NYF and LCT pegmatites occur throughout the northeast-trending Neoproterozoic Damara Belt, Namibia. Mineralization in the pegmatites varies geographically,...  相似文献   

Observations of the evolution of the aerosol, cloud and boundary‐layer characteristics during the 1st ACE‐2 Lagrangian experiment     

Doug W. Johnson  Simon Osborne  Robert Wood  Karsten Suhre  Patricia K. Quinn  Tim Bates  M. O. Andreae  Kevin J. Noone  Paul Glantz  Brian Bandy  J. Rudolph  Colin O'Dowd 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):348-374

During the 1st Lagrangian experiment of the North Atlantic Regional Aerosol Characterisation Experiment (ACE‐2), a parcel of air was tagged by releasing a smart, constant level balloon into it from the Research Vessel Vodyanitskiy . The Meteorological Research Flight's C‐130 aircraft then followed this parcel over a period of 30 h characterising the marine boundary layer (MBL), the cloud and the physical and chemical aerosol evolution. The air mass had originated over the northern North Atlantic and thus was clean and had low aerosol concentrations. At the beginning of the experiment the MBL was over 1500 m deep and made up of a surface mixed layer (SML) underlying a layer containing cloud beneath a subsidence inversion. Subsidence in the free troposphere caused the depth of the MBL to almost halve during the experiment and, after 26 h, the MBL became well mixed throughout its whole depth. Salt particle mass in the MBL increased as the surface wind speed increased from 8 m s⁻¹ to 16 m s⁻¹ and the accumulation mode (0.1μm to 3.0 μm) aerosol concentrations quadrupled from 50 cm⁻³ to 200 cm⁻³. However, at the same time the total condensation nuclei (>3 nm) decreased from over 1000 cm⁻³ to 750 cm⁻³. The changes in the accumulation mode aerosol concentrations had a significant effect on the observed cloud microphysics. Observational evidence suggests that the important processes in controlling the Aitken mode concentration which, dominated the total CN concentration, included, scavenging of interstitial aerosol by cloud droplets, enhanced coagulation of Aitken mode aerosol and accumulation mode aerosol due to the increased sea salt aerosol surface area, and dilution of the MBL by free tropospheric air.  相似文献   

Stratigraphy and tectonics of a time-transgressive ophiolite obduction onto the eastern margin of the Pelagonian platform from Late Bathonian until Valanginian time,exemplified in northern Evvoia,Greece     

Rudolph Scherreiks  Guillermo Meléndez  Marcelle BouDagher-Fadel  Georgia Fermeli  Dan Bosence 《International Journal of Earth Sciences》2014,103(8):2191-2216

The obduction of an ophiolite sheet onto the eastern Pelagonian carbonate platform complex of the Hellenides began during the Late Bathonian and ended with the final emplacement of the ophiolite during Valanginian time. The early stages of obduction caused subaerial exposure of the platform, recorded by an unconformity of Callovian age, which is marked by laterites overlying folded and faulted, karstic substrates. The laterites have distinct ophiolitic geochemical signatures, indicating that emergent ophiolite had been undergoing lateritic weathering. This unconformity coincides with widespread western Tethyan, Callovian gaps, indicating that the obduction in the Hellenides was probably related to far-reaching plate tectonic processes. Resumed gravitational pull and rollback of the subducted, oceanic leading edge of the temporarily exposed ophiolite. Platform drowning continued into Tithonian–Valanginian time, documented initially by reefal carbonates and then by below-CCD, carbonate-free radiolarian cherts and shales. Subsequently, siliciclastic turbidites, which apparently originated from uplifted Variscan basement, were deposited together with and over the radiolarite as the ophiolite nappe sheet advanced. The nappe substrate underwent tectonic deformations of varying intensity, while polymictic mélange and syntectonic sedimentary debris accreted beneath the ophiolite and at the nappe front. The provenience of the ophiolite nappe complexes of northern Evvoia most probably has to be looked for in the Vardar ocean.  相似文献   

Quantifying groundwater discharge to a small perennial stream in southern Ontario, Canada   总被引：3，自引：0，他引：3  

Edwin E. Cey  David L. Rudolph  Gary W. Parkin  Ramon Aravena 《Journal of Hydrology》1998,210(1-4):21-37

A study of the interaction between groundwater and surface water was undertaken within a small agricultural watershed in southern Ontario, Canada. Groundwater contributions to streamflow were measured along a section of stream during baseflow conditions and during rainfall events. Four techniques were used to estimate the contribution of groundwater to the stream along a 450 m reach (three during baseflow and one during stormflow conditions). Under baseflow conditions, streamflow measurements using the velocity–area technique indicated that the net groundwater flux to the stream during the summer months was 10 ml s⁻¹ m⁻¹. Hydrometric measurements (i.e. hydraulic gradient and hydraulic conductivity) taken using mini-piezometers installed in the sediments beneath the stream resulted in net groundwater flux estimates that were four to five times lower. Seepage meters failed to provide any measurements of water flux into or out of the stream. Therefore, based on these results, the velocity–area technique gives the best estimate of groundwater discharge. Hydrograph separations were conducted using isotopic ratios and electrical conductivity on two large rainfall events with different antecedent moisture conditions in the catchment. Both events showed that pre-event water (generally considered groundwater) dominated streamflow and tile drain flow with 64%–80% of the total discharge contributed by pre-event water. High water table conditions within the catchment resulted in greater stream discharge and a greater contribution of event water in the streamflow than that observed under low water table conditions for similar intensity storm events. The results also showed that differences in riparian zone width, vegetation and surface saturation conditions between the upper and lower catchment can influence the relative magnitude of streamflow response from the two catchment areas.  相似文献   

Circulation and fertility of waters in Concepcion Bay     

Ahumada B. Ramón  Rudolph G. Anny  Martinez M. Victorino 《Estuarine, Coastal and Shelf Science》1983,16(1):95-105

The spatial and temporal distributions of oxygen, nutrients and pigments in the waters of Concepcion Bay, Chile (36°40′S, 73°01′W) are described for 1978–1979. Analysis of the seasonal fluctuations shows the upwelling of water poor in oxygen and rich in nutrients inside the bay during summer. The upwelled water fertilizes the bay and produces progressive eutrophication, causing mass mortalities, discoloured water and mineralization of organic matter.  相似文献   

Computational methods for fitting statistical distribution models of multi-site binding equilibria     

Rudolph S. Parrish  E. Michael Perdue 《Mathematical Geology》1989,21(2):199-219

Statistical distribution models of multi-site binding equilibria have potential applicability in the study of acid-base and metal complexation chemistry of humic substances in soils, sediments, and natural waters. A mathematical derivation is presented for the general continuous model for the case of proton binding; computational methods are described for fitting numerically the parameters in such models. Among models considered are those based on nontruncated, truncated, and bimodal (mixed) distributions. Specific emphasis is placed on Gaussian distribution models.  相似文献   

Measurements of tropospheric OH concentrations: A comparison of field data with model predictions     

D. Perner  U. Platt  M. Trainer  G. Hübler  J. Drummond  W. Junkermann  J. Rudolph  B. Schubert  A. Volz  D. H. Ehhalt  K. J. Rumpel  G. Helas 《Journal of Atmospheric Chemistry》1987,5(2):185-216

Using long path UV absorption spectroscopy we have measured OH concentrations close to the earth's surface. The OH values observed at two locations in Germany during 1980 through 1983 range from 0.7×10⁶ to 3.2×10⁶ cm^-3. Simultaneously we measured the concentrations of O₃, H₂O, NO, NO₂, CH₄, CO, and the light non methane hydrocarbons. We also determined the photolysis rates of O₃ and NO₂. This allows calculations of OH using a zero dimensional time depdendent model. The modelled OH concentrations significantly exceed the measured values for low NO _x concentrations. It is argued that additional, so far unidentified. HO _x loss reactions must be responsible for that discrepancy.  相似文献   

Numerical investigation of road salt impact on an urban wellfield   总被引：2，自引：0，他引：2  

Bester ML  Frind EO  Molson JW  Rudolph DL 《Ground water》2006,44(2):165-175

The impact of road salt on a wellfield in a complex glacial moraine aquifer system is studied by numerical simulation. The moraine underlies an extensive urban and industrial landscape, which draws its water supply from >20 wellfields, several of which are approaching or have exceeded the drinking water limit for chloride. The study investigates the mechanisms of road salt infiltration, storage, and transport in the subsurface and assesses the effectiveness of mitigation measures designed to reduce the impact. The three-dimensional transport model accounts for increases in salt loading, as well as growth of the urbanized area and road network over the past 50 years. The simulations, which focus on one impacted wellfield, show chloride plumes originating mainly at arterial roads and migrating through aquitard windows into the water supply aquifers. The results suggest that the aquifer system contains a large and heterogeneously distributed mass of chloride and that concentrations in the aquifer can be substantially higher than the concentrations in the well water. Future impact scenarios indicate that although the system responds rapidly to reductions in salt loading, the residual chloride mass may take decades to flush out, even if road salting were discontinued. The implications with respect to urban wellfields in typical snow-belt areas are discussed.  相似文献   

A technique for atmospheric measurements of stable carbon isotope ratios of isoprene,methacrolein, and methyl vinyl ketone     

R. Iannone  R. Koppmann  J. Rudolph 《Journal of Atmospheric Chemistry》2007,58(3):181-202

A technique was developed to measure stable carbon isotope ratios (¹³C/¹²C) of light volatile organic compounds (VOCs) such as isoprene, methacrolein (MACR) and methyl vinyl ketone (MVK) using gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS). An automated sampling and cryofocussing system allowed for the extraction of VOCs from air samples of up to 140 L of air collected over 3 h, and the subsequent ¹³C/¹²C analysis of the VOCs by GCC-IRMS. Chromatography using selective transfer between two columns was used to improve the separation for selected compounds, increasing peak resolution and attaining less noisy baselines. Still, some target compounds could not be completely separated from co-eluting peaks. To reduce the bias of isotope ratio determinations, which can result from incomplete peak resolution, a peak-fitting procedure has been developed. In cases of overlapping peaks or substantial baseline drift, this peak fitting allows more accurate determination of isotope ratios than conventional integration schemes. Comparisons between off-line IRMS measurements and a peak-evaluation procedure using a prepared VOC gas-phase standard show that isotope ratios derived from large (>1 ng of carbon per peak) and well-resolved peaks have a reproducibility of ±0.3‰. With smaller masses in the range of 0.1–1 ng of carbon, reproducibility decreased to ±(0.5–0.8)‰. For a 140 L sample of air, such small masses of carbon correspond to mixing ratios in the low pptV range. The developed measurement technique was applied to a small set of ambient air samples taken during hot, sunny periods from late May to early August, 2005, at Forschungszentrum Jülich, Germany, a semi-rural area. The range of δ¹³C values determined for isoprene, benzene, and toluene are consistent with those reported in the literature. GCC-IRMS results of δ¹³C for ambient samples of isoprene, MACR, and MVK, measured at mixing ratios of 15–280 pptV, are presented and discussed.  相似文献   

Emissions of Volatile Organic Compounds from Sunflower and Beech: Dependence on Temperature and Light Intensity   总被引：11，自引：0，他引：11  

G. Schuh  A. C. Heiden  Th. Hoffmann  J. Kahl  P. Rockel  J. Rudolph  J. Wildt 《Journal of Atmospheric Chemistry》1997,27(3):291-318

Emissions of volatile organic compounds (VOCs) from sunflower (Helianthus annuus L. cv. giganteus) were measured in a continuously stirred tank reactor. The compounds predominantly emitted from sunflower were: isoprene, the monoterpenes -pinene, -pinene, sabinene, 3-carene and limonene, an oxygenated terpene, not positively identified so far and the sesquiterpene -caryophyllene. Emission rates ranged from 0.8 x 10^–16 to 4.3 x 10 ^–15 mol cm^–2 s^–1 at a temperature of 25°C and at a light intensity of 820 µEm^–2 s^–1. A dependence of the emission rates on temperature as well as on light intensity was observed. The emission rates of -pinene, sabinene and thujene from beech (Fagus sylvatica L.) were also affected by temperature as well as by light intensity. Our results suggest that an emission algorithm for all compounds emitted from sunflower and beech has to consider temperature and light intensity simultaneously. The observations strongly indicate that the emissions of VOCs from sunflower and beech are in part closely coupled to the rate of biosynthesis and in part originate from diffusion out of pools. The emission rates can be described by an algorithm that combines the model given by Tingey and coworkers with the algorithm given by Guenther and coworkers after slight modification.  相似文献