Response of douglas fir (Pseudotsuga menziesii) to uraniferous groundwater in a small glaciated drainage, Northeastern Washington State     

Robert A. Zielinski  R. Randall Schumann 《Journal of Geochemical Exploration》1987,27(3)

Douglas fir trees and associated soils were sampled from the slopes of a small ( 4 km²) drainage basin in northeastern Washington to investigate the biogeochemical response to locally uraniferous groundwater. Uranium is preferentially incorporated in needles and twigs compared to larger branches or the trunk. The U concentration in needle ash ranges from 0.2 to 5.8 μg g⁻¹ (ppm) and shows no correlation with the U concentration in associated soils. Rather, the distribution of anomalously uraniferous douglas fir (>1.0μg g⁻¹ U in needle ash) appears to be controlled by observed or readily inferred pathways of near-surface groundwater movement in the drainage. These pathways include: (1) general downslope movement of subsurface runoff; (2) increased flux of near-surface groundwater near the toe of an alluvial fan; and (3) emergence of uraniferous (100–150 ng ml⁻¹ [ppb] groundwater in the vicinity of a slope spring. The data also indicate the presence of near-surface uraniferous groundwater along a structurally controlled zone that parallels the north-south strike of the valley, and that includes the slope spring. The results suggest that biogeochemical sampling may be used to supplement more direct, but more limited, measurements of groundwater quality and flow regime in areas of near-surface contaminated groundwater.  相似文献   

Statistical modeling of historic shore erosion rates on the Chesapeake Bay in Maryland     

Randall K. Spoeri  Christopher F. Zabawa  Bruce Coulombe 《Environmental Geology》1985,7(3):171-187

Few strong relationships exist along the Chesapeake Bay shoreline between the historic erosion rate and the distribution of any of several coastal parameters which were defined and tested using traditional regression and discriminant analysis procedures To develop a simple predictive equation for shore erosion that could be used by coastal managers, the entire Chesapeake Bay shoreline was partitioned into naturally occurring reaches 2–5 km in length, and the historic erosion rate on each reach was modelled as a function of five variables (a) shoreline type, (b) “100-year” storm surge height, (c) mean tide range, (d) wave climate, and (e) potential littoral drift rate The statistical analysis yielded a multiple correlation coefficient (r ²) of 30 8%, discriminant analysis showed only the first two variables listed above are useful predictors (i e, statistically significant) of historic erosion rates A 95-mile portion of the same bay shoreline in Queen Anne’s and Talbot counties was then partitioned into shorter reach lengths (1/2–2km) and more variables were included The multiple correlation coefficient (r ²) improved slightly to 32 9%, but only shoreline type and potential littoral drift rate were found to be useful predictors of historic erosion rates Curiously, the ability to model statistically the historic shore erosion rate is best on those reaches already substantially protected by structures For Queen Anne’s and Talbot counties, the multiple regression coefficient improved to 61 5% when only reaches 1/2–2km in length protected by structures were considered.  相似文献   

A gender analysis of quality of life in Saskatoon, Saskatchewan     

Heather Dunning  Bonnie Janzen  Allison Williams  Sylvia Abonyi  Bonnie Jeffery  J. E. Randall  Bill Holden  Ronald Labonte  Nazeem Muhajarine  Gerry Klein  Tracey Carr 《GeoJournal》2006,65(4):393-407

While many community initiatives have attempted to assess the nature and determinants of their citizens’ quality of life (QOL), these initiatives have produced little about whether the key determinants of life quality differ by gender. Using both quantitative and qualitative data from a recent QOL research project in Saskatoon, Saskatchewan, Canada, this study explores whether factors that predict poor QOL are similar for women and men. The study also examines whether the nature of these gender differences varies across low, medium and high socio-economic status locales. Results showed that men and women were very similar in: (1) their QOL ratings, (2) reports of deterioration in neighborhood QOL, and (3) rating particular aspects of their neighborhood. Few gender differences were also found when analyzing data referring to place characteristics and social cohesion. Multivariate analysis revealed further similarities: (1) being divorced/widowed was a significant predictor of poor QOL, and (2) a negative view of community security issues was associated with deterioration in perceived neighborhood quality of life. For women, however, other variables were important predictors of QOL: being middle aged, being single, and having a poor opinion of the overall quality of their neighborhood. Qualitative analysis revealed that while men and women shared concern about general areas such as safety and neighborhood supports, their perceptions of the details around these issues differed. The multi-method results suggest that urban policy actions should include a gendered discussion of common QOL issues.  相似文献   

U–Pb dating of plutonic rocks involved in the nappe tectonic in southern Cameroon: consequence for the Pan-African orogenic evolution of the central African fold belt     

Sadrack Felix Toteu  Rose Yongue Fouateu  Joseph Penaye  Jacqueline Tchakounte  Aubin Ciriaque Seme Mouangue  William Randall Van Schmus  Etienne Deloule  Henrik Stendal 《Journal of African Earth Sciences》2006,44(4-5):479

TIMS-ID and SIMS U–Pb dating on zircons from metaplutonic rocks involved in the Pan-African nappe of southern Cameroon allow definition of three groups of subduction-related intrusions: group-I intrusions represented by the Masins metagabbro in the Lomie region yielded 666 ± 26 Ma; group-II intrusions represented by the Mamb metasyenogabbro and the Yaoundé pyriclasite yielded ca. 620 Ma and are broadly coeval with the deposition of the Yaoundé metasediments; group-III intrusions represented by the Elon augen metagranite and the Ngaa Mbappe metamonzodiorite yielded ca. 600 Ma. The onset of the nappe tectonics occurred under high-grade conditions in the range 616 to 610 Ma and continued around 600 Ma with the emplacement of the shallowest nappes. Finally, the construction of southern Cameroon proceeded by a multi-stage evolution characterized by a long-lived development of magmatic arcs associated with rapid opening and closure of sedimentary marginal basins in relation to a northward subduction.  相似文献   

Path-specific Velocity Structure of Western China from Surface-wave Dispersion     

Brett S. Ketter  Aaron A. Velasco  Charles J. Ammon  George E. Randall 《Pure and Applied Geophysics》2006,163(7):1235-1255

We develop one-dimensional (1-D) path-specific velocity models in western China using new Rayleigh and Love wave group and phase velocity dispersion measurements for 20 events in the region. The earthquakes were grouped into three geographic clusters from which we compute the average phase and group velocity dispersion. We invert the average dispersion curves simultaneously for 1-D shear-velocity models appropriate for the three central Asian paths, using three previous shear-velocity models as initial models. The models are validated by forward modeling waveforms of recent events. The crustal thickness beneath western China in the vicinity of the Lop Nor test site is 50–60 km and our velocity models are consistent with major geologic features (e.g., basins and mountain ranges) and previous structural models for this region.  相似文献   

Desert varnish: an environmental recorder for Mars     

Randall S Perry  Mark A Sephton 《Astronomy& Geophysics》2006,47(4):4.34-4.35

Randall S Perry and Mark A Sephton discuss a target material for Mars Sample Return: rocks coated with desert varnish, a mineral layer that records past surface climates on Earth, and probably on Mars too.  相似文献   

Regression models for estimating coseismic landslide displacement   总被引：6，自引：0，他引：6  

Randall W. Jibson   《Engineering Geology》2007,91(2-4):209-218

Newmark's sliding-block model is widely used to estimate coseismic slope performance. Early efforts to develop simple regression models to estimate Newmark displacement were based on analysis of the small number of strong-motion records then available. The current availability of a much larger set of strong-motion records dictates that these regression equations be updated. Regression equations were generated using data derived from a collection of 2270 strong-motion records from 30 worldwide earthquakes. The regression equations predict Newmark displacement in terms of (1) critical acceleration ratio, (2) critical acceleration ratio and earthquake magnitude, (3) Arias intensity and critical acceleration, and (4) Arias intensity and critical acceleration ratio. These equations are well constrained and fit the data well (71% < R² < 88%), but they have standard deviations of about 0.5 log units, such that the range defined by the mean ± one standard deviation spans about an order of magnitude. These regression models, therefore, are not recommended for use in site-specific design, but rather for regional-scale seismic landslide hazard mapping or for rapid preliminary screening of sites.  相似文献   

Factors triggering landslide occurrence on the Zemun loess plateau,Belgrade area,Serbia     

Tin Lukić  Dajana Bjelajac  Kathryn E. Fitzsimmons  Slobodan B. Marković  Biljana Basarin  Dragan Mlađan  Tanja Micić  Randall J. Schaetzl  Milivoj B. Gavrilov  Miško Milanović  György Sipos  Gábor Mezősi  Nevenka Knežević-Lukić  Miroljub Milinčić  Aleš Létal  Ivan Samardžić 《Environmental Earth Sciences》2018,77(13):519

Among the numerous factors that trigger landslide events, the anthropogenic impact caused by inadequate planning and faulty land use in urban areas is increasing. The Zemun settlement on the northern outskirts of Belgrade has experienced a number of landslides in the last three decades, endangering buildings and roads, and claiming human lives, particularly in the case of the 2010/2011 landslides. Selected meteorological parameters were used to calculate rainfall erosivity indices such as Precipitation Concentration Index and Modified Fournier Index over the period 1991–2015. Drought indices, Lang aridity index and Palfai Drought Index were calculated as well. Mann–Kendall trend test was applied to identify potential rising and/or declining trends both in meteorological parameters and calculated indices. Trend analysis of the annual and seasonal scales yielded a statistically significant trend in the spring time series. Stable arid and pronounced drought conditions were recorded. The modified Fournier index based on monthly mean values yields moderate aggressiveness, with several extreme values indicating very high erosivity classes, especially for 2010/2011. The geological substrate is predominantly loess and hence highly susceptible to erosion and slope failure when climatological conditions are suitable. Accelerated urbanization at the end of the last century reduced vegetation cover, intensified pressure on the vertical loess slope, and lacked suitable rain drainage systems so that surface-water runoff was directed into the porous loess, thereby endangering slope stability. We proposed a geomorphic model to describe the nature of the erosional processes on the loess cliffs of the Zemun loess plateau. Results from this study have implications for mitigation strategies.  相似文献   

Phenotypic Variation Among Invasive <Emphasis Type="Italic">Phragmites australis</Emphasis> Populations Does Not Influence Salinity Tolerance     

Forest R. Schenck  Torrance C. Hanley  R. Edward Beighley  A. Randall Hughes 《Estuaries and Coasts》2018,41(3):896-907

Phenotypic variation within species can have community- and ecosystem-level effects. Such variation may be particularly important in ecosystem engineers, including many invasive species, because of the strong influence of these species on their surrounding communities and environment. We combined field surveys and glasshouse experiments to investigate phenotypic variation within the invasive common reed, Phragmites australis, among four estuarine source sites along the east coast of North America. Field surveys revealed variation in P. australis height and stem density among source sites. In a glasshouse environment, percent germination of P. australis seeds also varied across source sites. To test the degree to which phenotypic variation in P. australis reflected genetic or environmental differences, we conducted a glasshouse common garden experiment assessing the performance of P. australis seedlings from the four source sites across a salinity gradient. Populations maintained differences in morphology and growth in a common glasshouse environment, indicating a genetic component to the observed phenotypic variation. Despite this variation, experimentally increased porewater salinity consistently reduced P. australis stem density, height, and biomass. Differences in these morphological metrics are important because they are correlated with the impacts of invasive P. australis on the ecological communities it invades. Our results indicate that both colonization and spread of invasive P. australis will be dependent on the environmental and genetic context. Additional research on intraspecific variation in invasive species, particularly ecosystem engineers, will improve assessments of invasion impacts and guide management decisions in estuarine ecosystems.  相似文献   

Transport and fate of nitrate within soil units of glacial origin     

Suzanna L. Moore  Eric W. Peterson 《Environmental Geology》2007,52(8):1527-1537

Questions concerning the influence of soil type and crop cover on the fate and transport of nitrate (NO₃⁻) were examined. During a growing season, soils derived from glacial material underlying either corn or soybeans were sampled for levels of NO₃⁻ within the pore water. Measured levels of NO₃⁻ ranged from below detection limit to 14.9 g NO₃⁻ per kilogram of soil (g/kg). In fields with the same crop cover, the silty-clayey soil exhibited a greater decrease in NO₃⁻ levels with depth than the sandier soil. Crop uptake of NO₃⁻ occurs within the root zone; however, the type of crop cover did not have a direct impact on the fate or transport during the growing season. The soils underlying soybeans had an increase in NO₃⁻ levels following harvest, suggesting that the decomposition of the soybean roots contributed to the net gain of NO₃⁻ in the shallow soil. For all of the soil types, conditions below 100 cm are conducive for microbial denitrification, with both a high water saturation level (>60%) and moderate organic carbon content (1–2%). At depths below 100 cm, temporal differences in NO₃⁻ levels of over a magnitude, up to a 95% reduction, were recorded in the soil units as the growing season progressed. Physical properties that control the transport of NO₃⁻ or denitrification have a larger influence on NO₃⁻ levels than crop type.

Eric W. PetersonEmail:

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