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101.
Lionel F. Villarroel Jerry R. Miller Paul J. Lechler Dru Germanoski 《Environmental Geology》2006,51(2):283-299
An intense, but localized rainfall event in February 2003, led to the severe erosion and failure of a tailings disposal impoundment at the Abarόa Antimony Mine in southern Bolivia. The failure released approximately 5,500 m3 of contaminated tailings into the Rio Chilco-Rio Tupiza drainage system. The impacts of the event on sediment quality are examined and compared to contamination resulting from historic mining operations in the headwaters of the basin. Of primary concern are contaminated floodplain soils located along downstream reaches of the Rio Tupiza which were found to contain lead (Pb), zinc (Zn), and antimony (Sb) concentrations that locally exceed Canadian, German, and Dutch guidelines for agricultural use. Spatial patterns in sediment-borne trace metal concentrations, combined with Pb isotopic data, indicate that Pb, Zn, and Sb are derived from three tributary basins draining the Abarόa, Chilcobija, and Tatasi-Portugalete mining districts. Downstream of each tributary, geographical patterns in trace metal concentrations reflect local geomorphic changes throughout the drainage system. Trace metal concentrations within the Rio Chilco decrease rapidly downstream as a result of dilution by uncontaminated sediments and storage of metal enriched particles (e.g., sulfide minerals) in the channel bed as a result of ongoing aggradation. Storage in the floodplains is limited. These processes significantly reduced the dispersal and, thus, the relative environmental affects of tailings eroded from the Abarόa Mine during the 2003 flood. In contrast, storage of Pb, Zn, and Sb in floodplains along the Rio Tupiza is significant, the majority of which is derived from historic mining operations, particularly mining within the Tatasi-Portugalete district. 相似文献
102.
Institutional capacity is an important element for climate change adaptation (CCA) and the development of such capacity is a great challenge in a Least Developed Country like Cambodia where resources are limited. An important first step to increasing capacity is via an understanding of the level of existing capacity; future priorities can then be subsequently identified. This study aimed to assess the capacity of organizations to implement climate change activities in Cambodia in order to provide such a basis for building capacity. Four elements of capacity were investigated in this research: (1) financial resources, (2) cooperation and coordination of stakeholders, (3) availability and quality of information on vulnerability and adaptation to climate change, and (4) the level of understanding of climate change vulnerability and adaptation. The data were collected through semistructured interviews with a wide range of government and non-government informants across a number of sectors. Results of the study showed that informants perceived capacity for CCA to be very constrained, especially in terms of financial resources and cooperation, and addressing these factors was ranked as the highest climate change capacity priority. Institutional capacity constraints were considered to relate more generally to weak governance of CCA. In light of our research findings, the absence of local higher education institutions in CCA activities should be addressed. The support of such institutions would provide an important mechanism to progress both capacity development as well as partnerships and coordination between different types of organizations and relevant sectors.Policy relevanceCapacity for CCA within Cambodian health and water sectors was perceived to be very constrained across a range of interdependent factors. Increasing funding was ranked as the highest priority for building capacity for CCA; however, governance factors such as ‘improved cooperation’ were also ranked highly. Improving stakeholders' awareness of the availability of adaptation funds and resources, and their responsiveness to funding criteria, is an important implication of our research, as is improving the mobilization of local resources and the private sector. To address the issue of weak cooperation among stakeholders, improving the coordination function of the National Climate Change Committee (NCCC) regarding stakeholder engagement and capacity building is crucial. Ensuring that CCA activities are based on sound information and knowledge from across different disciplines and, importantly, include the perspectives of vulnerable people themselves, ultimately underpins and supports the realization of the above priorities. 相似文献
103.
Dwight E. Boegeman Gordon J. Miller William R. Normark 《Marine Geophysical Researches》1972,1(4):381-396
The Marine Physical Laboratory of the Scripps Institution of Oceanography has developed an acoustic relay transponder for precise relative positioning of near-bottom instruments and geologic sampling devices. Although specifically designed to position equipment lowered on standard wire ropes without a need to maintain direct electrical contact with the surface ship, the relay transponder may be used to track free vehicles, such as deep submersibles, from the surface. The relay transponder is positioned relative to an array of bottom-anchored acoustic transponders. It is interrogated acoustically from the surface ship; it then sequentially interrogates the bottom transponders which, in turn, reply to the ship. From the measurement of the total travel time (ship to relay transponder to bottom transponder to ship) and assuming, or knowing, the sound velocity of the water, we obtain a relayed range measurement. These relayed ranges, used in conjunction with ship to bottom-transponder ranges, allow us to calculate the position of the relay transponder. A recent application of this technique is described in which several gravity core samples from the crest of the Horizon Guyot were positioned with respect to the detailed bathymetry and the geology within the area. The estimated error in positioning the samples is less than 20 m inside a navigational net extending over 100 km2.Contribution of the Scripps Institution of Oceanography, new series. 相似文献
104.
Benjamin M. Rau Dale W. Johnson Bruce A. Roundy Richard F. Miller Todd G. Caldwell Annmarie Lucchesi 《Journal of Arid Environments》2011,75(9):827-835
Vegetation changes associated with climate shifts and anthropogenic disturbance can have major impacts on biogeochemical cycling and soils. Much of the Great Basin, U.S. is currently dominated by sagebrush (Artemisia tridentate (Rydb.) Boivin) ecosystems. Sagebrush ecosystems are increasingly influenced by pinyon (Pinus monophylla Torr. & Frém and Pinus edulis Engelm.) and juniper (Juniperus osteosperma Torr. and Juniperus occidentalis Hook.) expansion. Some scientists and policy makers believe that increasing woodland cover in the intermountain western U.S. offers the possibility of increased organic carbon (OC) storage on the landscape; however, little is currently known about the distribution of OC on these landscapes, or the role that nitrogen (N) plays in OC retention. We quantified the relationship between tree cover, belowground OC, and total below ground N in expansion woodlands at 13 sites in Utah, Oregon, Idaho, California, and Nevada, USA. One hundred and twenty nine soil cores were taken using a mechanically driven diamond tipped core drill to a depth of 90 cm. Soil, coarse fragments, and coarse roots were analyzed for OC and total N. Woodland expansion influenced the vertical distribution of root OC by increasing 15-30 cm root OC by 2.6 Mg ha−1 and root N by 0.04 Mg ha−1. Root OC and N increased through the entire profile by 3.8 and 0.06 Mg ha−1 respectively. Woodland expansion influenced the vertical distribution of soil OC by increasing surface soil (0-15 cm) OC by 2.2 Mg ha−1. Woodland expansion also caused a 1.3 Mg ha−1 decrease in coarse fragment associated OC from 75-90 cm. Our data suggests that woodland expansion into sagebrush ecosystems has limited potential to store additional belowground OC, and must be weighed against the risk of increased wildfire and exotic grass invasion. 相似文献
105.
SARAL/AltiKa has a Dual Frequency Microwave Radiometer (DFMR), and Jason-2 has an Advanced Microwave Radiometer (AMR). Both microwave radiometer sensors include a 23.8 GHz primary water sensing channel. The measurement consistencies between DFMR and AMR are important for establishing a consistent altimetry data set between SARAL/AltiKa and Jason-2 in order to accurately assess sea level rise in a long-term time series. This study investigates the measurement consistency in the 23.8 GHz channel between DFMR and AMR at the Simultaneous Nadir Overpasses (SNO's) between the two satellites and also at coldest ocean brightness temperature locations. Preliminary results show that while both instruments show no significant trends over the one year since the launch of SARAL, a consistent relative bias of 2.88 K (DFMR higher than AMR) with a standard deviation of 0.98 K is observed. The relative bias at the lowest brightness temperature from the SNO method (-3.82 K) is consistent with that calculated from coldest ocean method (-3.74 K). The relative bias exhibits strong latitude (and scene temperature) dependency, changing from -3.82 K at high latitudes to -0.92 K near the equator. There also exists an asymmetry between the northern and southern hemisphere. The relative bias increases toward the lower end of brightness temperature. 相似文献
106.
A thermal event reduces the number of previously registered fission tracks in a mineral dependent upon the track retention properties of the individual mineral. Apatite, sphene and zircon have retention properties over a wide range of temperatures (from 100° to 550°C); apatite data reveal information at lowest temperatures while sphene and zircon data are useful for higher temperatures.Thermal events within this temperature range of 100°C to about 550°C are suitable for study with this technique. The age of the event is determined from samples in which the fission tracks are completely erased, while minerals containing partially removed (erased) tracks provide information on the temperatures occurring during the thermal event.As a test case, the analysis of the temperatures developed by the meteorite impact which produced the Ries crater at 14.7 m.y. ago is presented. 相似文献
107.
Niranjan D. Chatterjee Klaus Miller Walter Olbricht 《Physics and Chemistry of Minerals》1994,21(1-2):50-62
Internally consistent thermodynamic data, including their uncertainties and correlations, are reported for 22 phases of the quaternary system CaO-Al2O3-SiO2-H2O. These data have been derived by simultaneous evaluation of the appropriate phase properties (PP) and reaction properties (RP) by the novel technique of Bayes estimation (BE). The thermodynamic model used and the theory of BE was expounded in Part I of this paper. Part II is the follow-up study illustrating an application of BE. The input for BE comprised, among others, the a priori values for standard enthalpy of formation of the i-th phase, Δf H i 0 , and its standard entropy, S i 0 , in addition to the reaction reversal constraints for 33 equilibria involving the relevant phases. A total of 269 RP restrictions have been processed, of which 107 turned out to be non-redundant. The refined values for Δf H i 0 and S i 0 obtained by BE, including their 2σ-uncertainties, appear in Table 4; the Appendix reproduces the corresponding correlation matrix. These data permit generation of computed phase diagrams with 2σ-uncertainty envelopes based on conventional error propagation; Fig. 3 depicts such a phase diagram for the system CaO-Al2O3-SiO2. It shows that the refined dataset is capable of yielding phase diagrams with uncertainty envelopes narrow enough to be geologically useful. The results in Table 4 demonstrate that the uncertainties of the prior values for Δf H i Emphasis>0 , given in Table 1, have decreased by up to an order of magnitude, while those for S i 0 improved by a factor of up to two. For comparison, Table 4 also lists the refined Δf H i 0 and S i 0 data obtained by mathematical programming (MAP), minimizing a quadratic objective function used earlier by Berman (1988). Examples of calculated phase diagrams are given to demonstrate the advantages of BE for deriving internally consistent thermodynamic data. Although P-T curves generated from both MAP and BE databases will pass through the reversal restrictions, BE datasets appear to be better suited for extrapolations beyond the P-T range explored experimentally and for predicting equilibria not constrained by reversals. 相似文献
108.
RudyWijnands † Jon M.Miller Michiel van derKlis 《Monthly notices of the Royal Astronomical Society》2002,331(1):60-70
We report on several pointed Rossi X-ray Timing Explorer observations of the enigmatic low-mass X-ray binary (LMXB) 4U 1957+11 at different X-ray luminosities. The luminosity of the source varied by more than a factor of 4 on time-scales of months to years. The spectrum of the source tends to become harder when its luminosity increases. Only very weak (1–2 per cent rms amplitude, 0.001–10 Hz , 2–60 keV) rapid X-ray variability was observed during the observations. A comparison of the spectral and temporal behaviour of 4U 1957+11 with other X-ray binary systems, in particular LMC X-3, indicates that 4U 1957+11 is likely to be a persistent LMXB harbouring a black hole and it is persistently in the black hole high state. If confirmed, it would be the only such system known. 相似文献
109.
The Port Mouton Shear Zone: intersection of a regional fault with a crystallizing granitoid pluton 总被引:2,自引:0,他引:2
D. Barrie Clarke Krista L. McCuish Ron H. Vernon Victor Maksaev Brent V. Miller 《Lithos》2002,61(3-4):141-159
The peraluminous tonalite–monzogranite Port Mouton Pluton is a petrological, geochemical, structural, and geochronological anomaly among the many Late Devonian granitoid intrusions of the Meguma Lithotectonic Zone of southern Nova Scotia. The most remarkable structural feature of this pluton is a 4-km-wide zone of strongly foliated (040/subvertical) monzogranites culminating in a narrow (10–30 m), straight, zone of compositionally banded rocks that extends for at least 3 km along strike. The banded monzogranites consist of alternating melanocratic and leucocratic compositions that are complementary to the overall composition of that part of the pluton, suggesting an origin by mineral–melt and mineral–mineral sorting. Biotite and feldspar are strongly foliated in the plane of the compositional bands. These compositional variations and foliations originated by a process of segregation flow during shearing of the main magma with a crystallinity of 55–75%. Subsequent minor brittle fracturing of feldspars, twinning of microcline, development of blocky sub-grains in quartz, and kinking of micas demonstrate overprinting by a high-temperature deformation straddling the monzogranite solidus. Small folds and late sigmoidal dykes indicate dextral movement on the shear zone. This Port Mouton Shear Zone (PMSZ) is approximately co-linear with the only outcrops of Late Devonian mafic intrusions in the area, two of which are syn-plutonic with well-developed mingling textures in the marginal tonalite of the Port Mouton Pluton. Also closely co-linear with the mafic intrusions are a granitoid dyke that extends well beyond the outer contact of the Port Mouton Pluton, a swarm of large aligned angular xenolithic slabs, a zone of thin wispy schlieren banding, a large Be-bearing pegmatite, and a breccia pipe with abundant garnetiferous metapelitic xenoliths. In various ways, the shear zone may control all of these features. The Port Mouton Shear Zone is parallel to many other NE-trending faults and shear zones in the northern Appalachians, probably related to the docking of the Meguma Zone along the Cobequid–Chedabucto Fault system. 相似文献
110.
Tim?M.?O’BrienEmail author Elizabeth?L.?Miller 《Contributions to Mineralogy and Petrology》2014,168(4):1071
Microtextural, U–Pb, trace element and Lu–Hf analyses of zircons from gneisses dredged from the Chukchi Borderland indicate a long-lived, Cambrian–Ordovician, granulite facies metamorphism. These results reveal a complete prograde, peak and cooling history of zircon growth during anatexis. Early increasing temperatures caused modification and Pb-loss of Precambrian zircons by recrystallization and dissolution/re-precipitation of existing grains. Small variations in initial 176Hf/177Hf results (0.282325–0.282042) and flat HREE patterns of these zircons indicate that they grew by dissolution/re-precipitation in the presence of garnet. Zircons subsequently crystallized from a partial melt during peak to post-peak metamorphism from 530 to 485 Ma. A broad range of initial 176Hf/177Hf ratios (0.282693–0.282050) and mineral inclusions within zircons suggest that this phase of growth incorporated Zr and Hf obtained from the breakdown of Zr-enriched phases. Microtextural evidence along with trace element and isotopic data suggests that final growth of metamorphic rims on zircon occurred during slow cooling and crystallization of residual partial melts during the early Ordovician (485–470 Ma). Younger, late Ordovician–Silurian (420–450 Ma) euhedral, oscillatory-zoned, trace element-enriched zircons crystallized within leucocratic veins that intrude the gneisses. Their age corresponds to granitoids dated from this same dredge. The intrusives and veins provide evidence that the Chukchi Borderland rifted from a position near Pearya and northwest Svalbard, which represent the northern continuation of the Caledonian orogen. Evidence for earlier Cambrian metamorphism has not been reported from this region. The age of granulite facies metamorphism reported here represents the earliest phase of deformation in the Arctic Caledonides. 相似文献