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71.
Nathan E. Bramall Richard Quinn Andrew Mattioda Kathryn Bryson Julie D. Chittenden Amanda Cook Cindy Taylor Giovanni Minelli Pascale Ehrenfreund Antonio J. Ricco David Squires Orlando Santos Charles Friedericks David Landis Nykola C. Jones Farid Salama Louis J. Allamandola Søren V. Hoffmann 《Planetary and Space Science》2012,60(1):121-130
The Space Environment Viability of Organics (SEVO) experiment is one of two scientific payloads aboard the triple-cube satellite Organism/ORganic Exposure to Orbital Stresses (O/OREOS). O/OREOS is the first technology demonstration mission of the NASA Astrobiology Small Payloads Program. The 1-kg, 1000-cm3 SEVO cube is investigating the chemical evolution of organic materials in interstellar space and planetary environments by exposing organic molecules under controlled conditions directly to the low-Earth orbit (LEO) particle and electromagnetic radiation environment. O/OREOS was launched on November 19, 2010 into a 650-km, 72°-inclination orbit and has a nominal operational lifetime of six months. Four classes of organic compounds, namely an amino acid, a quinone, a polycyclic aromatic hydrocarbon (PAH), and a metallo-porphyrin are being studied. Initial reaction conditions were established by hermetically sealing the thin-film organic samples in self-contained micro-environments. Chemical changes in the samples caused by direct exposure to LEO radiation and by interactions with the irradiated microenvironments are monitored in situ by ultraviolet/visible/near-infrared (UV/VIS/NIR) absorption spectroscopy using a novel compact fixed-grating CCD spectrometer with the Sun as its light source. The goals of the O/OREOS mission include: (1) demonstrating key small satellite technologies that can enable future low-cost astrobiology experiments, (2) deploying a miniature UV/VIS/NIR spectrometer suitable for in-situ astrobiology and other scientific investigations, (3) testing the capability to establish a variety of experimental reaction conditions to enable the study of astrobiological processes on small satellites, and (4) measuring the chemical evolution of organic molecules in LEO under conditions that can be extrapolated to interstellar and planetary environments. In this paper, the science and technology development of the SEVO instrument payload and its measurements are described. 相似文献
72.
Carolina Calvi Cristina Dapeña Daniel E. Martinez Orlando M. Quiroz Londoño 《Environmental Earth Sciences》2018,77(6):248
The Ballenera Creek has 160 km2 being a small catchment in the Pampa Plain in Argentina. This area has been deeply modified by human action through agricultural activities. From 2013 to 2017, electrical conductivity, stable isotopes of water and nitrate concentration monitoring program were conducted. The sampling included weekly and bimonthly samples in two sites along the stream, several groundwater wells and monthly precipitation. Chemical and isotopic tracers are used to discriminate the streamflow components and to evaluate their incidence in the nitrate concentration. The easiest conceptual model for gaining streams contemplates two main elements: direct runoff and groundwater (baseflow and pre-event water). The direct runoff has the lowest electrical conductivity and 18Ow variable content. The baseflow component is characterized by the highest electrical conductivity and isotope composition quite constant. Finally, pre-event water has an intermediate electrical conductivity and isotopic content close to the rainfall-weighted average composition. The nitrate concentration obtained was in general related to the different stream stages and was a useful indicator to evaluate the fertilization in agricultural zones. 相似文献
73.
Adriane Machado Farid Chemale Jr. Rommulo V. Conceio Koji Kawaskita Diego Morata Orlando Oteíza William R. Van Schmus 《Lithos》2005,82(3-4):435-453
Isotope data and trace elements concentrations are presented for volcanic and plutonic rocks from the Livingston, Greenwich, Robert, King George and Ardley islands (South Shetland arc, Antarctica). These islands were formed during subduction of the Phoenix Plate under the Antarctica Plate from Cretaceous to Tertiary. Isotopically (87Sr/86Sr)o ratios vary from 0.7033 to 0.7046 and (143Nd/144Nd)o ratios from 0.5127 to 0.5129. εNd values vary from +2.71 to +7.30 that indicate asthenospheric mantle source for the analysed samples. 208Pb/204Pb ratios vary from 38.12 to 38.70, 207Pb/204Pb ratios are between 15.49 and 15.68, and 206Pb/204Pb from 18.28 to 18.81. The South Shetland rocks are thought to be derived from a depleted MORB mantle source (DMM) modified by mixtures of two enriched mantle components such as slab-derived melts and/or fluids and small fractions of oceanic sediment (EM I and EM II). The isotopic compositions of the subduction component can be explained by mixing between at least 4 wt.% of sediment and 96 wt.% of melts and/or fluids derived from altered MORB. 相似文献
74.
Hydrogeochemistry and isotope techniques to determine water interactions in groundwater-dependent shallow lakes,Wet Pampa Plain,Argentina 总被引:1,自引:0,他引:1
Asunción Romanelli Orlando Mauricio Quiroz Londoño Daniel Emilio Martínez Héctor Enrique Massone Alicia Haydée Escalante 《Environmental Earth Sciences》2014,71(4):1953-1966
This paper gives an account of the implementation of hydrochemical and isotopic techniques to identify and explain the processes that govern solute exchange in two groundwater-dependent shallow lakes in the Southeastern Pampa Plain of Argentina. Water samples (lakes, streams, spring water and groundwater) for hydrochemical and stable isotopic determination were collected and the main physical–chemical parameters were measured. The combination of stable isotope data with hydrogeochemical techniques was used for the identification of sources and preferential recharge areas to these aquatic ecosystems which allowed the explanation of the lake water origin. The hydrochemical processes which explain Los Padres Lake water chemistry are evaporation from groundwater, CO2 input, calcite dissolution, Na+ release by Ca2+ and Mg2+ exchange, and sulfate reduction. The model that best aligns with La Brava Lake hydrochemical constraints includes: mixing, CO2 and calcite dissolution, cationic exchange with Na+ release and Mg2+ adsorption, and to a lesser extent, Ca/Na exchange. This model suggests that the fractured aquifer contribution to this water body is greater than 50 %. An isotopic-specific fingerprint for each lake was identified, finding a higher evaporation rate for La Brava Lake compared to Los Padres Lake. Isotopic data demonstrate the importance of these shallow lakes as recharge areas to the regional aquifer, becoming areas of high groundwater vulnerability. The Tandilia Range System, considered in many hydrogeological studies as the impermeable bedrock of the Pampean aquifer, acts as a fissured aquifer in this area, contributing to low salinity waters and with a fingerprint similar to groundwater isotopic composition. 相似文献
75.
Arnold H. Bouma Monty A. Hampton Robert C. Orlando 《Marine Georesources & Geotechnology》2013,31(1-4):291-308
Abstract Lower Cook Inlet in Alaska has high‐ tidal currents that average 3–4 knots and normally reach a peak of 6–8 knots. The bottom has an average depth of about 60–70 m in the central part of the inlet that deepens toward the south. Several types of bedforms, such as sand waves, dunes, ripples, sand ribbons, and lag deposits form a microtopography on the otherwise smooth seafloor. Each bedform type covers a small field, normally a few hundred to a few thousand meters wide, and usually several kilometers long parallel to the tidal flow. High‐resolution seismic systems, side‐scan sonar and bottom television were used to study these bedforms. Large sand waves with wavelengths over 300 m and wave heights up to 10 m were observed. Fields of ebb‐oriented or flood‐oriented asymmetric bedforms commonly grade into more symmetric shapes. Several orders of smaller sand waves and dunes cover the flanks of the very large bedforms. The crest directions of both size groups are normally parallel, but deviations of up to 90° have been observed; local deviations may occur where smaller forms approach the crests of the larger sand waves. Bottom television observations demonstrated active bedload transport in a northerly direction on crests and midflanks of southward asymmetric large sand waves, but not in their troughs. Movement of bedload occurs in the form of small ripples. Although the asymmetry of the large bedforms suggests that migration has taken place in the ebb or flood directions, the very low surface angles (2.5°‐8°) of these bedforms do not indicate regular movements. The large bedforms are probably relict features, or they migrate only under severe conditions, whereas active sand transport by ripples and smaller sand waves and dunes moves bedload back and forth with the tides. An understanding of such movements is essential for determining design criteria for offshore installations and in benthic‐faunal studies. 相似文献
76.
Measurements of the Henry's Law Coefficients of 2-Methyl-3-buten-2-ol, Methacrolein, and Methylvinyl Ketone 总被引:1,自引:0,他引:1
Laura T. Iraci Bradly M. Baker Geoffrey S. Tyndall John J. Orlando 《Journal of Atmospheric Chemistry》1999,33(3):321-330
Using an equilibrium headspace technique, Henry's law coefficients were measured for methacrolein (H = 6.5 ± 0.7 M atm-1) and methylvinyl ketone (41 ± 7.0 M atm-1) in water at 25 °C. In addition, 2-methyl-3-buten-2-ol was studied at 30 °C in water and in an aqueous ionic solution representative of plant tissue. Similar values were found in deionized water (65 ± 3.5 M atm-1) and in a 0.05 mol kg-1 Ca2+, K+, NO3-, SO42- solution (62 ± 0.8 M atm-1). These Henry's Law coefficients are too small to allow for significant partitioning of methacrolein, methylvinyl ketone or methylbutenol into cloud water under equilibrium conditions. 相似文献