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101.
Aidan Foley Gerd Cachandt Janine Franklin Fergus Willmore Tim Atkinson 《Hydrogeology Journal》2012,20(3):483-498
The Corallian limestone of northern England (UK) is widely exploited for water supplies and exhibits the karstic phenomena of sinking rivers, conduit development and groundwater velocities of several kilometres per day. To test a number of model-derived source protection zones and elucidate contaminant transport mechanisms in the aquifer, three tracer tests were conducted from a set of swallow-holes draining the River Derwent toward public water supply wells in the eastern part of the aquifer. Tracers used included: Enterobacter cloacae (bacteriophage), Photine C (optical brightener), sodium fluorescein (fluorescent dye) and sulphur hexafluoride (dissolved gas), the varying properties of which make them suitable analogues for different types of potential contaminant. Observed tracer transport times and arrival patterns indicate that tracer transport occurs through karstic channels embedded in a network of primary fissures which exert control over tracer concentrations once initial tracer plumes have passed. A dipole flow system is observed between the swallow-holes and the closest abstraction well, whilst previously modelled source protection zones do not accurately reflect either groundwater velocity or those areas of the aquifer supplying the wells. These findings imply that managing such aquifers for potential contamination should rely upon empirical tracer evidence for source-protection zone modelling. 相似文献
102.
Community variations in social vulnerability to Cascadia-related tsunamis in the U.S. Pacific Northwest 总被引:2,自引:2,他引:0
Tsunamis generated by Cascadia subduction zone earthquakes pose significant threats to coastal communities in the U.S. Pacific
Northwest. Impacts of future tsunamis to individuals and communities will likely vary due to pre-event socioeconomic and demographic
differences. In order to assess social vulnerability to Cascadia tsunamis, we adjust a social vulnerability index based on
principal component analysis first developed by Cutter et al. (2003) to operate at the census-block level of geography and focus on community-level comparisons along the Oregon coast. The number
of residents from blocks in tsunami-prone areas considered to have higher social vulnerability varies considerably among 26
Oregon cities and most are concentrated in four cities and two unincorporated areas. Variations in the number of residents
from census blocks considered to have higher social vulnerability in each city do not strongly correlate with the number of
residents or city assets in tsunami-prone areas. Methods presented here will help emergency managers to identify community
sub-groups that are more susceptible to loss and to develop risk-reduction strategies that are tailored to local conditions. 相似文献
103.
Focal mechanism parameters of some significant earthquakes from southern Turkey have been estimated using either the body waveforms or the first motions of P-waves. It is observed that fault plane solutions derived from first motions may not be well constrained and may often be in error because of poor signal-to-noise ratios at some stations, poorly distributed recording stations in azimuth, lack of recognition of the reversed polarities at some stations, and positions of stations in terms of the crustal velocity structure, focal depth and, hence, take-off angles in the source area. The use of the inversion method introduces a considerable improvement in the focal parameters estimated in previous studies that have been used to construct seismotectonic models in the study area. The focal depths inferred from the inversion of body waveforms for the earthquakes occurring in southwestern Turkey are compatible with those reported by the ISC bulletins and other previous studies while the focal depths of earthquakes from the Antalya Bay are found to be less than those given by different agencies. Waveform inversion of earthquakes that have occurred in and around the Antalya Bay implies a low velocity layer showing azimuthal dependence. Hence, depth of rupture and lateral extent of velocity structure are of importance in the investigation of earthquake faulting process in this area. The source time duration of shallow earthquakes is generally longer than that for the deep focus earthquakes from the Antalya Bay and the Rhodes area. The events with relatively short and simple time functions may be interpreted as low stress drop events relative to the crustal ones. 相似文献
104.
Erin Jing Male William L. Pickles Eli A. Silver Gary D. Hoffmann Jennifer Lewicki Martha Apple Kevin Repasky Elizabeth A. Burton 《Environmental Earth Sciences》2010,60(2):251-261
Hyperspectral plant signatures can be used as a short-term, as well as long-term (100-year timescale) monitoring technique
to verify that CO2 sequestration fields have not been compromised. An influx of CO2 gas into the soil can stress vegetation, which causes changes in the visible to near-infrared reflectance spectral signature
of the vegetation. For 29 days, beginning on July 9, 2008, pure carbon dioxide gas was released through a 100-m long horizontal
injection well, at a flow rate of 300 kg day−1. Spectral signatures were recorded almost daily from an unmown patch of plants over the injection with a “FieldSpec Pro”
spectrometer by Analytical Spectral Devices, Inc. Measurements were taken both inside and outside of the CO2 leak zone to normalize observations for other environmental factors affecting the plants. Four to five days after the injection
began, stress was observed in the spectral signatures of plants within 1 m of the well. After approximately 10 days, moderate
to high amounts of stress were measured out to 2.5 m from the well. This spatial distribution corresponded to areas of high
CO2 flux from the injection. Airborne hyperspectral imagery, acquired by Resonon, Inc. of Bozeman, MT using their hyperspectral
camera, also showed the same pattern of plant stress. Spectral signatures of the plants were also compared to the CO2 concentrations in the soil, which indicated that the lower limit of soil CO2 needed to stress vegetation is between 4 and 8% by volume. 相似文献
105.
106.
J.-K. Lee † A.J. Walsh‡ M.G. Burton M.C.B. Ashley 《Monthly notices of the Royal Astronomical Society》2001,324(4):1102-1108
We report the discovery of H2 line emission associated with 6.67-GHz methanol maser emission in massive star-forming regions. In our UNSWIRF/AAT observations, H2 1–0 S(1) line emission was found associated with an ultracompact H ii region IRAS 14567–5846 and isolated methanol maser sites in G318.95–0.20 , IRAS 15278–5620 and IRAS 16076–5134 . Owing to the lack of radio continuum in the latter three sources, we argue that their H2 emission is shock excited, while it is UV-fluorescently excited in IRAS 14567–5846 . Within the positional uncertainties of 3 arcsec, the maser sites correspond to the location of infrared sources. We suggest that 6.67-GHz methanol maser emission is associated with hot molecular cores, and propose an evolutionary sequence of events for the process of massive star formation. 相似文献
107.
Aaron S. Burton Hannah McLain Daniel P. Glavin Jamie E. Elsila Jemma Davidson Kelly E. Miller Alexander V. Andronikov Dante Lauretta Jason P. Dworkin 《Meteoritics & planetary science》2015,50(3):470-482
Exogenous delivery of amino acids and other organic molecules to planetary surfaces may have played an important role in the origins of life on Earth and other solar system bodies. Previous studies have revealed the presence of indigenous amino acids in a wide range of carbon‐rich meteorites, with the abundances and structural distributions differing significantly depending on parent body mineralogy and alteration conditions. Here we report on the amino acid abundances of seven type 3–6 CK chondrites and two Rumuruti (R) chondrites. Amino acid measurements were made on hot water extracts from these meteorites by ultrahigh‐performance liquid chromatography with fluorescence detection and time‐of‐flight mass spectrometry. Of the nine meteorites analyzed, four were depleted in amino acids, and one had experienced significant amino acid contamination by terrestrial biology. The remaining four, comprised of two R and two CK chondrites, contained low levels of amino acids that were predominantly the straight chain, amino‐terminal (n‐ω‐amino) acids β‐alanine, and γ‐amino‐n‐butyric acid. This amino acid distribution is similar to what we reported previously for thermally altered ureilites and CV and CO chondrites, and these n‐ω‐amino acids appear to be indigenous to the meteorites and not the result of terrestrial contamination. The amino acids may have been formed by Fischer–Tropsch‐type reactions, although this hypothesis needs further testing. 相似文献
108.
T. Hill M. A. Thompson M. G. Burton A. J. Walsh V. Minier M. R. Cunningham D. Pierce-Price 《Monthly notices of the Royal Astronomical Society》2006,368(3):1223-1268
We report the results of a submillimetre continuum emission survey targeted towards 78 star formation regions, 72 of which are devoid of methanol maser and UC H ii regions, identified in the Swedish ESO Submillimetre Telescope (SEST)/SEST IMaging Bolometer Array (SIMBA) millimetre continuum survey of Hill et al. At least 45 per cent of the latter sources, dubbed 'mm-only', detected in this survey are also devoid of the mid-infrared MSX emission. The 450- and 850-μm continuum emission was mapped using the Submillimetre Common User Bolometer Array (SCUBA) instrument on the James Clerk Maxwell Telescope (JCMT). Emission is detected towards 97 per cent of the 78 sources targeted as well as towards 28 other SIMBA sources lying in the SCUBA fields.
In total, we have identified 212 cores in this submillimetre survey, including 106 previously known from the SIMBA survey. Of the remaining 106 sources, 53 result from resolving a SIMBA source into multiple submillimetre components, whilst the other 53 sources are submillimetre cores, not seen in the SIMBA. Additionally, we have identified two further mm-only sources in the SIMBA images. Of the total 405 sources identified in the SIMBA survey, 255 are only seen at millimetre wavelengths.
We concatenate the results from four (sub)millimetre continuum surveys of massive star formation, together with the Galactic plane map of Pierce-Price et al. in order to determine the dust grain emissivity index β for each of the sources in the SIMBA source list. We examine the value of β with respect to temperature, as well as for the source classes identified in the SIMBA survey, for variation of this index. Our results indicate that β is typically 2, which is consistent with previous determinations in the literature, but for a considerably larger sample than previous work. 相似文献
In total, we have identified 212 cores in this submillimetre survey, including 106 previously known from the SIMBA survey. Of the remaining 106 sources, 53 result from resolving a SIMBA source into multiple submillimetre components, whilst the other 53 sources are submillimetre cores, not seen in the SIMBA. Additionally, we have identified two further mm-only sources in the SIMBA images. Of the total 405 sources identified in the SIMBA survey, 255 are only seen at millimetre wavelengths.
We concatenate the results from four (sub)millimetre continuum surveys of massive star formation, together with the Galactic plane map of Pierce-Price et al. in order to determine the dust grain emissivity index β for each of the sources in the SIMBA source list. We examine the value of β with respect to temperature, as well as for the source classes identified in the SIMBA survey, for variation of this index. Our results indicate that β is typically 2, which is consistent with previous determinations in the literature, but for a considerably larger sample than previous work. 相似文献
109.
S. L. Breen S. P. Ellingsen M. Johnston-Hollitt S. Wotherspoon I. Bains M. G. Burton M. Cunningham N. Lo C. E. Senkbeil T. Wong 《Monthly notices of the Royal Astronomical Society》2007,377(2):491-506
We report the results of a blind search for 22-GHz water masers in two regions, covering approximately half a square degree, within the giant molecular cloud associated with RCW 106. The complete search of the two regions was carried out with the 26-m Mount Pleasant radio telescope and resulted in the detection of nine water masers, five of which are new detections. Australia Telescope Compact Array (ATCA) observations of these detections have allowed us to obtain positions with arcsecond accuracy, allowing meaningful comparison with infrared and molecular data for the region. We find that for the regions surveyed there are more water masers than either 6.7-GHz methanol, or main-line OH masers. The water masers are concentrated towards the central axis of the star formation region, in contrast to the 6.7-GHz methanol masers which tend to be located near the periphery. The colours of the GLIMPSE point sources associated with the water masers are similar to those of 6.7-GHz methanol masers, but slightly less red. We have made a statistical investigation of the properties of the 13 CO and 1.2-mm dust clumps with and without associated water masers. We find that the water masers are associated with the more massive, denser and brighter 13 CO and 1.2-mm dust clumps. We present statistical models that are able to predict those 13 CO and 1.2-mm dust clumps that are likely to have associated water masers, with a low misclassification rate. 相似文献
110.