Estimates of future impacts of degrading streams in the deep loess soil region of western Iowa on private and public infrastructure costs     

Landon L. Morris  Marty J. McVey  Robert A. Lohnes  C.Phillip Baumel 《Engineering Geology》1996,43(4):255-264

In the beginning of the 20th century, many streams in western Iowa were channelized to reduce flooding and to open swamp land to cultivation. Channel straightening accomplished its goal. However, it resulted in greater streamflow velocities, causing stream channels to degrade. This degradation has resulted in significant loss of land and damage to transportation and communications infrastructure in western Iowa and in several states in the United States. Baumel et al. (1994; Impact of Degrading Western Iowa Streams on Private and Public Infrastructure Costs. Final Report Iowa DOT HR-352, Stream Stabilization in Western Iowa) estimated the historical cost of this degradation on land loss and damage to transportation and communications infrastructure in western Iowa. The purpose of this paper is to extend the Baumel et al. analysis to estimate future degradation costs on 141 streams in western Iowa. It also presents two types of degradation cost estimates. One is a time neutral cost that does not consider the dates on which the degradation costs are incurred. The second is a time value cost which considers the dates on which the costs are incurred and then discounts these costs back to 1992 dollars. The time value costs are the more accurate estimates of the cost of future degradation in 1992 dollars and should be used to evaluate stream stabilization project proposals.  相似文献   

Microphytobenthos contribution to nutrient-phytoplankton dynamics in a shallow coastal lagoon     

Ian T. Webster  Phillip W. Ford  Bruce Hodgson 《Estuaries and Coasts》2002,25(4):540-551

Nutrient fluxes and primary production were examined in Lake Illawarra (New South Wales, Australia), a shallow (Z_mean=1.9 m) coastal lagoon with a surface area of 35 km², by intensive measurement of dissolved nutrients and oxygen profiles over a 22-h period. Rates of primary production and nutrient uptake were calculated for the microphytobenthos, seagrass beds, macroalgae, and pelagic phytoplankton. Although gross nutrient release rates to the water column and sediment pore waters were potentially high, primary production by microphytobenthos rapidly sequesters the re-mineralized nutrients so that net releases, averaged over times longer than a day, were low. Production in the water column was closely coupled with the relatively low sediment net nutrient release rates and detrital decomposition in the water column. Dissolved inorganic nitrogen and silica concentrations in the water column are drawn down at the beginning of the day. The system did not appear to be light limited so photosynthesis occurs as fast as the nutrients become available to the phytoplankton and microphytobenthos. We conjecture that microphytobenthos are the dominant primary producers and, as has been shown previously, that the nutrient uptake occurs in phase with the various stages of the diatom growth.  相似文献   

贵州锦丰(烂泥沟)金矿床含砷黄铁矿和脉石英及其包裹体的稀土元素特征   总被引：3，自引：0，他引：3  

陈懋弘  吴六灵Phillip J.Uttley　Tony Norman郑建民  秦运忠 《岩石学报》2007,23(10):2423-2433

贵州锦丰(烂泥沟)金矿是滇黔桂“金三角“目前已探明的最大的卡林型金矿床.含砷黄铁矿是该矿床最主要的载金矿物,脉石英是最显著的热液蚀变作用产物.含砷黄铁矿、脉石英及其包裹体具有相同的稀土元素特征,表现为轻重稀土分馏明显(LREE/HREE:7.95～31.77,(La/Yb)N:8.97～40.49);轻稀土有一定的分异((La/Sm)n:3.20～5.29),曲线右倾程度大;重稀土分异不明显((Gd/Yb)n:1.41～3.35),曲线平坦;负铕异常明显(δEu 0.59～0.71);微弱的铈负异常(δCe 0.97～0.98).代表成矿流体特征的脉石英包裹体稀土配分型式及特征值与区域上不同时代的幔源基性-超基性岩差别较大,而与矿床围岩、矿石、含砷黄铁矿及其包裹体稀土配分型式及特征值十分相似,具上部地壳普通沉积岩的特点,反映成矿流体主要不是来源于地幔,而是以壳源为主.Eu负异常反映了偏酸性(富CO2)、还原性的成矿环境;微弱的Ce负异常表明成矿流体来源于以沉积水和热脱水为主的盆地流体.  相似文献   

Metrics for the comparative analysis of geospatial datasets with applications to high-resolution grid-based population data     

Aarthy Sabesan  Kathleen Abercrombie  Auroop R. Ganguly  Budhendra Bhaduri  Eddie A. Bright  Phillip R. Coleman 《GeoJournal》2007,69(1-2):81-91

Geospatial data sciences have emerged as critical requirements for high-priority application solutions in diverse areas, including, but not limited to, the mitigation of natural and man-made disasters. Three sets of metrics, adopted or customized from geo-statistics, applied meteorology and signal processing, are tested in terms of their ability to evaluate geospatial datasets, specifically two population databases commonly used for disaster preparedness and consequence management. The two high-resolution, grid-based population datasets are the following: The LandScan dataset available from the Geographic Information Science and Technology (GIST) group at the Oak Ridge National Laboratory (ORNL), and the Gridded Population of the World (GPW) dataset available from the Center for International Earth Science Information Network (CIESIN) group at Columbia University. Case studies evaluate population data across the globe, specifically, the metropolitan areas of Washington DC, USA, Los-Angeles, USA, and Houston, USA, and London, UK, as well as the country of Iran. The geospatial metrics confirm that the two population datasets have significant differences, especially in the context of their utility for disaster readiness and mitigation. While this paper primarily focuses on grid based population datasets and disaster management applications, the sets of metrics developed here can be generalized to other geospatial datasets and applications. Future research needs to develop metrics for geospatial and temporal risks and associated uncertainties in the context of disaster management. The U. S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.  相似文献   

贵州锦丰（烂泥沟）超大型金矿床构造解析及构造成矿作用   总被引：3，自引：4，他引：3       下载免费PDF全文

陈懋弘  毛景文  Phillip J. Uttley  Tony Norman  吴六灵  郑建民  秦运忠 《矿床地质》2007,26(4):380-396

在矿区大比例尺填图的基础上,运用构造解析的理论和方法,对贵州锦丰(烂泥沟)金矿的构造特征、构造演化和构造控矿作用进行了系统的阐述。矿区构造线主要分为近NS向、NW向和NE向3组,其中NW向构造线控制了矿区的构造格架。构造变形主要经历了同生期裂陷、造山期挤压、后碰撞造山侧向挤压和岩石圈伸展等4个阶段。盆地裂陷期间(D2-T2)形成的同生断层为后续的构造活动提供了最初的构造薄弱面,并成为主要的热液通道;造山期挤压期间(T3)形成了矿区最为明显的近NS向和NW向大型倒转褶皱和逆冲断层以及配套的NE向右旋走滑断层;后碰撞造山侧向挤压期间(J1)形成走向NE的叠加褶皱,并在F2-F3"X"型断裂系上形成近EW向的拉张区,矿质沿着拉张的空间沉淀就位;燕山期(J2-K)岩石圈伸展,形成小规模的近水平逆断层。上述4个主要构造变形阶段与右江盆地的裂陷-闭合-坍塌的发展演化历史相吻合,成矿发生在由挤压向拉张过渡的构造体制转换阶段。造山期逆冲作用形成的构造闭圈和后碰撞造山期间挤压向伸展转变的过程中形成的局部张性构造环境是矿质得以大量聚集、沉淀的主要构造控制因素。构造成矿作用是锦丰(烂泥沟)金矿单一矿体垂向延深1000m以上的主要制约因素。构造成矿的观点将为在滇黔桂"金三角"卡林型金矿带的深部找矿提供重要的理论依据。  相似文献   

The North Atlantic Oscillation and oceanic precipitation variability     

Annarita Mariotti  Phillip Arkin 《Climate Dynamics》2007,28(1):35-51

Global North Atlantic Oscillation (NAO) oceanic precipitation features in the latter half of the twentieth century are documented based on the intercomparison of multiple state-of-the-art precipitation datasets and the analysis of the NAO atmospheric circulation and SST anomalies. Most prominent precipitation anomalies occur over the ocean in the North Atlantic, where in winter a “quadrupole-like” pattern is found with centers in the western tropical Atlantic, sub-tropical Atlantic, high-latitude eastern Atlantic and over the Labrador Sea. The extent of the sub-tropical and high-latitude center and the amount of explained variance (over 50%) are quite remarkable. However, the tropical Atlantic center is probably the most intriguing feature of this pattern apparently linking the NAO with ITCZ variability. In summer, the pattern is “tripole-like” with centers in the eastern Mediterranean Sea, the North Sea/Baltic Sea and in the sub-polar Atlantic. In the eastern Indian Ocean, the correlation is positive in winter and negative in summer, with some link to ENSO variability. The sensitivity of these patterns to the choice of the NAO index is minor in winter while quite important in summer. Interannual NAO precipitation anomalies have driven similar fresh water variations in these “key” regions. In the sub-tropical and high-latitude Atlantic in winter precipitation anomalies have been roughly 15 and 10% of climatology per unit change of the NAO, respectively. Decadal changes of the NAO during the last 50 years have also influenced precipitation and fresh water flux at these time-scales, with values lower (higher) than usual in the high-latitude eastern North Atlantic (Labrador Sea) in the 1960s and the late 1970s, and an opposite situation since the early 1980s; in summer the North Sea/Baltic region has been drier than usual during the period 1965–1975 when the NAO was generally positive.  相似文献   

Assessing landscape attractiveness: a comparative test of two new methods     

Phillip S. Kane 《Applied geography (Sevenoaks, England)》1981,1(2):77-96

Techniques for assessing landscape attractiveness are becoming increasingly important in environmental planning. They are a manifestation of the growing need to monitor landscape deterioration, to help preserve natural beauty, to learn about our cultural perceptions, and to satisfy an ever-increasing body of environmental law.This report describes two such evaluation techniques developed by the author and used by the National Trust of South Australia to classify and record natural and rural landscapes. One method, a component checklist, relies on a detailed appraisal of individual landscape elements. The other method, using bipolar semantic differentials, measures ‘whole-landscape’ emotional responses. Although very different in design, and in how viewer preferences are ascertained, the two techniques provide vista scores that correlate very highly (S_r = 0.81 for n = 46).For either method, scenes whose scores are more than 6 points apart can be regarded as significantly different in aesthetic qualities. As with all present evaluation methods, there are still problems with both technique design and the transformation of vistapoint data to spatial (mappable) information. Nevertheless, both the checklist and the bipolar methods seem to be reliable and face-valid tools for measuring South Australian landscape preferences.  相似文献   

Plastic contamination in the decapod crustacean Nephrops norvegicus (Linnaeus, 1758)     

Murray F  Cowie PR 《Marine pollution bulletin》2011,62(6):1207-1217

The aim of this study was to determine the extent Nephrops consumes plastics in the Clyde Sea and if this intake occurs through their diet. Plastic contamination was found to be high in Nephrops, 83% of the animals sampled contained plastics (predominately filaments) in their stomachs. Tightly tangled balls of plastic strands were found in 62% of the animals studied but were least prevalent in animals which had recently moulted. No significant difference in plastic load was observed between males and females. Raman spectroscopy indicated that some of the microfilaments identified from gut contents could be sourced to fishing waste. Nephrops fed fish seeded with strands of polypropylene rope were found to ingest but not to excrete the strands. The fishery for Norway lobster, Nephrops norvegicus, is the most valuable in Scotland and the high prevalence of plastics in Nephrops may have implications for the health of the stock.  相似文献   

Accuracy, Precision, and Stability of a Vibrating-Wire Transducer Measurement System to Measure Hydraulic Head     

Phillip J. Zarriello 《Ground Water Monitoring & Remediation》1995,15(2):157-168

A vibrating-wire transducer measurement system was investigated to determine its accuracy, precision, and stability for use in a study of ground water movement in low-permeability material. Twenty transducers with a pressure range of 10 psi were tested for stability over 100 days. half under low pressure (0.256 psi) and half under approximately full-scale pressure (10 psi). Measurement precision and stability were far better than measurement accuracy. Random noise in the data indicates that the transducers were precise to within 0.02 psi. The transducer measurements were generally stable to within 0.05 psi. but most showed a blight decrease in pressure over time. Measurements by transducers under low pressure were within 0.038 psi of actual pressure, and those made by transducers under high pressure were within −0.20 psi. as indicated by the difference between the mean measurement of each transducer and the mean measurement of all transducers. These measurements were within the reported accuracy for transducers under low pressure, but differed by more than the reported accuracy for transducers under high pressure: this indicates that transducer accuracy is largely determined by the pressure coefficient used to convert transducer readings to pressure units. Pressure coefficient calibration of selected transducers by a water filled standpipe and a digital manometer indicate that hysteresis could be the most significant factor affecting the transducer accuracy Standpipe calibrations indicate a pressure coefficient difference of about 13 percent between increasing and decreasing pressure, but deadweight calibrations indicate a difference of only 1.5 percent. The observed measurement and equipment error could affect interpretation of water level measurements; thus, independent water level measurements and rigorous review of the data arc needed to evaluate the accuracy of transducer measurements.  相似文献   

Nondestructive spectroscopic and petrochemical investigations of Paleoarchean spherule layers from the ICDP drill core BARB5, Barberton Mountain Land,South Africa          下载免费PDF全文

Jörg Fritz  Roald Tagle  Luisa Ashworth  Ralf Thomas Schmitt  Axel Hofmann  Béatrice Luais  Phillip D. Harris  Desirée Hoehnel  Seda Özdemir  Tanja Mohr‐Westheide  Christian Koeberl 《Meteoritics & planetary science》2016,51(12):2441-2458

A Paleoarchean impact spherule‐bearing interval of the 763 m long International Continental Scientific Drilling Program (ICDP) drill core BARB5 from the lower Mapepe Formation of the Fig Tree Group, Barberton Mountain Land (South Africa) was investigated using nondestructive analytical techniques. The results of visual observation, infrared (IR) spectroscopic imaging, and micro‐X‐ray fluorescence (μXRF) of drill cores are presented. Petrographic and sedimentary features, as well as major and trace element compositions of lithologies from the micrometer to kilometer‐scale, assisted in the localization and characterization of eight spherule‐bearing intervals between 512.6 and 510.5 m depth. The spherule layers occur in a strongly deformed section between 517 and 503 m, and the rocks in the core above and below are clearly less disturbed. The μXRF element maps show that spherule layers have similar petrographic and geochemical characteristics but differences in (1) sorting of two types of spherules and (2) occurrence of primary minerals (Ni‐Cr spinel and zircon). We favor a single impact scenario followed by postimpact reworking, and subsequent alteration. The spherule layers are Al₂O₃‐rich and can be distinguished from the Al₂O₃‐poor marine sediments by distinct Al‐OH absorption features in the short wave infrared (SWIR) region of the electromagnetic spectrum. Infrared images can cover tens to hundreds of square meters of lithologies and, thus, may be used to search for Al‐OH‐rich spherule layers in Al₂O₃‐poor sediments, such as Eoarchean metasediments, where the textural characteristics of the spherule layers are obscured by metamorphism.  相似文献