Tephra studies: NATO Advanced Study Institute Series. Edited by S. Self and R. S. J. Sparks. R. Reidel Publishing Co., Boston 1981, xiv + 481 pp     

Susan Shipley 《Quaternary Research》1983,19(3):407-408

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Natural background and pollution levels of some heavy metals in soils from the area of Dayton,Ohio   总被引：2，自引：0，他引：2  

Charles J. Ritter  Susan M. Rinefierd 《Environmental Geology》1983,5(2):73-78

In a reconnaissance study, trace amounts of Cd, Cu, Pb, and Zn were determined in “A-zone” soil from 22 locations in the Dayton, Ohio, area. Soil samples were collected at high-volume air monitoring sites in urban, suburban, and rural areas. Measurable amounts of the elements were found in all of the samples. Positive correlations occur between each metal and particulate matter, with correlation coefficients of aboutr=0.70, at the 99% confidence level. Natural background values for the elements were measured in soil from rural areas. Theoretical background values, which are very close to those measured, were calculated from the individual regression equations. Natural background levels do not exceed 1.00 ppm Cd, 15 ppm Cu, 25 ppm Pb, and 55 ppm Zn. The heavy metal contents of most soils in the area exceed background by factors of up to 3.0 for Cd, up to 4.5 for Cu, up to 11 for Pb, and up to 4.5 for Zn. Significant positive correlations among the metals suggest a common source (or sources) for at least some, if not most, of the heavy metals. For the most part, the highest metal values are found in soils near coal-burning plants. Fly ash from a local plant contains substantial amounts of the elements. The high lead values are largely due to vehicular exhaust. However, there is evidence that the metals can also come from the normal deterioration of vehicles. It appears that airborne pollution is an important source of heavy metals in Dayton area soils.  相似文献   

Labor Movement: How Migration Regulates Labor Markets by Harald Bauder     

Susan W. Hardwick 《The Professional geographer》2007,59(4):548-550

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Morphometric Controls and Basin Response in The Cascade Mountains   总被引：2，自引：0，他引：2  

Fes De Scally  Olav Slaymaker  & Ian Owens 《Geografiska Annaler: Series A, Physical Geography》2001,83(3):117-130

Morphometric variables associated with 36 debris torrent, 78 snow avalanche, 45 composite debris torrent and snow avalanche and 14 streamflow basins in the Cascade Mountains of southwestern British Columbia, Canada are examined. The results show significant statistical differences in top and bottom elevations, relief, channel length and gradient, basin area, fan gradient and area, and basin ruggedness between snow avalanche basins and the two basin types affected by debris torrents, reflecting the very different nature of these processes. Only top and bottom elevations and fan area differ significantly between debris torrent and debris torrent-snow avalanche basins, implying that the latter are probably debris torrent basins in origin. As many as six morphometric variables are significantly different between streamflow basins and the other basin types, allowing the former to be differentiated despite their small, steep character. Discriminant analysis indicates that bottom elevation and channel or path gradient are the best variables for classifying the four basin types by process. Generally strong correlations exist between basin area on the one hand and relief, channel length and channel gradient on the other in debris torrent, debris torrent-snow avalanche, and streamflow basins. Fan gradient and area are, however, weakly or modestly correlated with basin area or ruggedness. No such morphometric relations are present in snow avalanche basins. The results of this study also indicate that in debris torrent-prone basins the fan gradient and Melton's R have identifiable lower thresholds while basin area has an upper threshold, but use of these thresholds for identification of debris torrent hazard is complicated by overlapping thresholds for streamflow basins.  相似文献   

Strain localization as a key to reconciling experimentally derived flow-law data with dynamic models of continental collision     

Susan Ellis  Silke Wissing  Adrian Pfiffner 《International Journal of Earth Sciences》2001,90(1):168-180

Published strength profiles predict strength discontinuities within and/or at the base of continental crust during compression. We use finite element models to investigate the effect of strength discontinuities on continental collision dynamics. The style of deformation in model crust during continued subduction of underlying mantle lithosphere is controlled by: (1) experimental flow-law data; (2) the crustal geotherm; (3) strain localization by erosion; (4) strain-softening and other localization effects. In the absence of erosion and other factors causing strain localization, numerical models with typical geothermal gradients and frictional/ductile rheologies predict diffuse crustal deformation with whole-scale detachment of crust from mantle lithosphere. This prediction is at odds with earlier model studies that only considered frictional crustal rheologies and showed asymmetric, focused crustal deformation. Without localization, model deformation is not consistent with that observed in small collisional orogens such as the Swiss Alps. This suggests that strain localization by a combination of erosion and rheological effects such as strain softening must play a major role in focusing deformation, and that strength profiles derived under constant strain rates and uniform material properties cannot be used to infer crustal strength during collision dynamics.  相似文献   

Chemical assembly of Archean anorthosites from amphibolite- and granulite-facies terranes, SW Greenland     

Robert F. Dymek  Brent E. Owens 《Contributions to Mineralogy and Petrology》2001,141(5):513-528

We report whole-rock, major- and trace-element compositions (obtained by XRF and INA methods) for the amphibolite-facies Buksefjorden and granulite-facies Nordland anorthosites, SW Greenland. In a previous petrologic study on the same sample suite, we documented differences in texture, mineralogy, and mineral compositions between these two anorthosite bodies. Chemical analyses confirm differences in composition between the two bodies, but these differences cannot be explained by variations in metamorphic conditions, and point towards differences in the nature of their protoliths. Analyzed Nordland samples are anorthosites and leucogabbros with 88-98% normative plagioclase, whereas those from Buksefjorden include anorthosite, leucogabbro, and gabbro with ~55-95% normative plagioclase. Two or more compositional groupings can be recognized at each site, which correspond to differences in color and mineralogy of the hand samples. Samples from Buksefjorden are mainly quartz-normative, whereas those from Nordland are olivine (- nepheline) normative. Other differences include higher Ni/Co ratio and REE contents in the granulite-facies anorthosites from Nordland. REE pattern shapes are similar, however, being moderately fractionated at ~0.5-102 chondrites with positive Eu-anomalies. Calculated equilibrium melt patterns are similar for both anorthosites, being relatively flat at ~50-1502 chondrites, suggesting unfractionated (but evolved) parental magmas. Olivine must have been present in the protoliths of the Nordland rocks compared with Buksefjorden. Otherwise, the protoliths contained plagioclase with variable An-content (~An₆₂-An₉₂) and a mafic component with variable Fe/Mg (mg ~0.3-0.8). This mafic component was either hornblende or a combination of ortho- and clinopyroxene in fixed proportions, plus a small amount of magnetite. Mixing calculations demonstrate that some Buksefjorden anorthosites contain two varieties of plagioclase: a calcic type that may correspond to cumulus crystals, and a sodic-type that may correspond to a trapped-melt component. On plots of normative whole-rock An versus mg, compositions of the Buksefjorden and Nordland anorthosites form crude negative arrays that differ from the generally positive trends of mafic layered intrusions (Kiglapait, Skaergaard) and from the generally flats trends of plagioclase-rich cumulate rocks (St. Urbain and Stillwater anorthosites). This difference provides further evidence for the distinctive nature of Archean calcic-anorthosite complexes compared with other types of mafic intrusions. Moreover, this distribution of data points is consistent with the assembly of the protolith of the SW Greenland anorthosites mainly as mixtures of plagioclase and hornblende. Finally, the field for the Buksefjorden and Nordland anorthosites overlaps only slightly with that for the Fiskenaesset Complex, thus extending the known range of compositions for Archean anorthosites in West Greenland.  相似文献   

High-frequency climatic variability and crop yields     

Daniel S. Wilks  Susan J. Riha 《Climatic change》1996,32(3):231-235

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Impact of the Montreal protocol and its amendments on the rate of change of global radiative forcing     

Susan Solomon  John S. Daniel 《Climatic change》1996,32(1):7-17

Increases in chlorinated and brominated halocarbons are believed to be responsible for the depletion of stratospheric ozone observed over much of the globe in the past decade or so. Ozone depletion is in turn believed to lead to a negative radiative forcing, tending to cool the stratosphere and the surface. We show that the increasing atmospheric concentrations of ozone-depleting halocarbons and onset of related ozone depletion likely led to a negative forcing of the climate system in the 1980s that slowed significantly the rate of change of total anthropogenic radiative forcing due to the combined effect of all greenhouse gases over that decade. Within the next decade, emissions of these halocarbons are expected to rapidly decrease, with corresponding impacts on ozone and radiative forcing. As the emissions of ozone-depleting gases are reduced and eventually phased out, the rate of ozone depletion is expected to decrease and eventually reverse. All other things being equal, we show that the change from deepening ozone depletion in the 1980s to ozone increases in the future should lead to a pronounced increase in the decadal rate of change of anthropogenic greenhouse forcing of the next few decades, perhaps to levels unprecedented in this century.  相似文献   

Comparability of Large-Scale Studies of Agricultural Chemical Contamination of Rural Private Wells   总被引：1，自引：0，他引：1  

Chittaranjan Ray  Susan C. Schock 《Ground Water Monitoring & Remediation》1996,16(2):92-102

Detection of agricultural chemicals in ground water has prompted numerous studies. Federal, state, and regional studies were conducted in the last 10 years in order to assess the occurrence of agricultural chemicals in ground water. The results of the studies present the number or percentage of samples with agricultural chemicals above the drinking water standard or health advisory levels as well as samples with detections of one or more compounds. Data comparison from one state or region to another are frequently referred to by regulatory and agency personnel involved in water quality and agriculture issues. Unless the history of pesticide use, method of chemical analyses, detection limits, statistical design of the sampling plan, well type, well depth, geology of the formation material, and typical land use around the wellhead are known, such comparisons can be misleading. Reporting the limitations or presenting a disclaimer should be a key element for a study so that "apples and oranges" are not compared.  相似文献   

Reply to comments by G. Kosarev, N. Petersen and L. P. Vinnik on 'The use of velocity spectrum for stacking receiver functions and imaging upper mantle discontinuities     

H. Gurrola  J. B. Minster  T. Owens 《Geophysical Journal International》1996,124(2):642-646

We thank the editors of GJI for the opportunity to respond to the comment in this issue by Kosarev, Petersen & Vinnik 11996: hereafter referred to as KPV), which disputes the historical and technical accuracy of the paper by Gurrola, Minster & Owens (1994; henceforth referred to as GMO).  相似文献