The coagulation of dissolved^{239, 240}Pu in estuaries as determined from a mixing experiment     

Glen T. Shen  Edward R. Sholkovitz  Don R. Mann 《Earth and Planetary Science Letters》1983,64(3):437-444

A mixing experiment, using large volumes (100 l) of filtered (< 1 μm) freshwater and seawater end-members, was performed to simulate and investigate the chemical reactivity of^{239, 240}Pu during estuarine mixing. An organic-rich freshwater with a relatively high concentration (0.8 dpm/100 l) of dissolved^{239, 240}Pu was used as one end-member; Buzzards Bay seawater (dissolved^{239, 240}Pu= 0.04dpm/100l) was the other. The results demonstrate that dissolved^{239, 240}Pu in the freshwater undergoes extensive and rapid coagulation under simulated estuarine conditions. There is a strong correlation between the amount of coagulation of dissolved^{239, 240}Pu, humic acids (HA), and Fe. The extent of coagulation of all three constituents increases with increasing salinity and the net extent of their removal is 53%, 57%, and 100% for Pu, HA, and Fe respectively. As has been documented for Fe in freshwater, dissolved^{239, 240}Pu appears to be stabilized by naturally occurring humic substances to form negatively charged colloids which are then coagulated by seawater cations. The extrapolation of these experimental results to real estuaries will require additional research.  相似文献   

Increased susceptibility to No. 2 fuel oil coincident with initiation of particle feeding in developing mud snails,Ilyanassa obsoleta     

Jan A. Pechenik  Don C. Miller 《Estuaries and Coasts》1983,6(3):237-242

Encapsulated embryos and free-living larvae of Ilyanassa obsoleta were exposed to concentrations of No. 2 fuel oil (water-accommodated fraction, WAF) up to 1.0 ppm. Development of velum pigmentation and release of larvae from egg capsules were delayed in the presence of 1.0 ppm WAF, but exposure to the oil did not increase developmental mortality of encapsulated individuals. Individuals which were prematurely removed from egg capsules and exposed to oil directly suffered no mortality until yolk reserves were depleted and feeding on phytoplankton commenced. Feeding, free-living larvae suffer high mortality at 1.0 ppm WAF. The reduced susceptibility of encapsulated embryos to the oil stress may therefore reflect the importance of toxicant uptake by ingestion (as opposed to diffusion) rather than the degree of protection afforded by encapsulation.  相似文献   

Preliminary Evaluation of an Alternate Electrode Array for Use in Shallow-Subsurface Electrical Resistivity Studies     

Thomas J. Carringtona  Don A. Watson 《Ground water》1981,19(1):48-57

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Remote Sensing and Geophysical Investigations of Glacial Buried Valleys in Northeastern Kansas     

Jane E. Denne  Harold L. Yarger  P. Allen Macfarlane  Ralph W. Knapp  Marios A. Sophocleous  James R. Lucas  Don W. Steeples 《Ground water》1984,22(1):56-65

Aquifers found in glacial buried valleys are a major source of good-quality ground water in northeastern Kansas. The extent and character of many of these deposits are not precisely known, so a detailed study of the buried valleys was undertaken. Test drilling, Landsat imagery, shallow-earth temperature measurements, seismic refraction, surface electrical resistivity, and gravity data were used to evaluate two sites in Nemaha and Jefferson Counties. Tonal patterns on springtime Landsat imagery and winter/summer anomalies in shallow-earth temperatures were quick and inexpensive methods for locating some glacial buried aquifers and suggested areas for more intensive field studies. Reversed seismic refraction and resistivity surveys were generally reliable indicators of the presence or absence of glacial buried valleys, with most depth determinations being within 25% of test-drilling results. The effectiveness of expensive test-hole drilling was greatly increased by integrating remote sensing, shallow-earth temperature, seismic, and resistivity techniques in the two buried valley test areas. A gravity profile allowed precise definition of the extent of one of the channels after the other techniques had been used for general information.  相似文献   

Induced seismicity in mines in Canada—An overview   总被引：1，自引：0，他引：1  

Henry S. Hasegawa  Robert J. Wetmiller  Don J. Gendzwill 《Pure and Applied Geophysics》1989,129(3-4):423-453

Monitoring of mine-induced seismicity in Canada has improved with the expansion of regional seismograph networks into areas of active mining. However, the severity, and in some cases the frequency, of mine-induced tremors has increased as mining extends to greater depths and at accelerated rates of extraction. Because of the complex design and large areal extent of many mines (potash, coal and metalliferous), the most feasible and practical way to monitor these tremors at the present time is to deploy a network of seismometers in and on the surface above mines experiencing microearthquake activity. A few of these mines already have a network of seismometers deployed around them and plans are under way to deploy seismograph networks around other mines that have experienced some rather severe tremors in recent times. Six possible mechanisms for mine-induced tremors are described and the associatedP- andS-wave radiation patterns presented. A comparison of actual seismic radiation patterns with theoretical predictions is a quick way to diagnose the potential source mechanisms. In addition, recognizing the pattern of microearthquake activity preceding larger tremors can be used to mitigate the potential effects of severe tremors.  相似文献   

Obituary: James Brock Rowe, 1910–1995     

Don Biddle  Mal Barlow 《The Australian geographer》1995,26(2):200-201

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Aluminum-dependent trace element partitioning in clinopyroxene     

Don Francis  William Minarik 《Contributions to Mineralogy and Petrology》2008,156(4):439-451

As technical advances have dramatically increased our ability to analyze trace elements, the need for more reliable data on the compositional dependence of trace element partitioning between minerals and melt has become increasingly important. The late-Cretaceous Carmacks Group of south central Yukon comprises a succession of primitive high-Mg ankaramitic lavas characterized by shoshonitic chemical affinities and containing large complexly zoned clinopyroxene phenocrysts. The compositional zonation of the clinopyroxene phenocrysts is characterized by relatively Fe-rich (Mg^# = Mg/(Mg + Fe) = 0.85), but mottled, cores surrounded by mantles of cyclically-zoned clinopyroxene whose Mg^# varies repeatedly between 0.9 and 0.80. These cyclically zoned clinopyroxene mantles appear to record the repeated influx and mixing of batches of primitive with more evolved magma in a deep sub-crustal (∼1.2 GPa) magma chamber(s). Laser ablation ICP-MS was used to analyze the trace element variation in these zoned clinopyroxenes. The results indicate more than a threefold variation in the absolute concentrations of Th, Zr, rare earth elements (REE), and Y within individual clinopyroxene phenocrysts, with no apparent change in the degree of REE or high field strength element (HFSE) fractionation. The variation in absolute abundances of trace elements correlates closely with the major element composition of the clinopyroxene, with the most enriched clinopyroxene having the lowest Mg^# and highest Al contents. The problem is that the amount of crystal fractionation required to explain the major element variation (∼20%) in these clinopyroxene phenocrysts cannot explain the increase in the abundance of the incompatible trace elements, which would require more than 70% crystal fractionation, if constant partition coefficients are assumed. The anomalous increase in incompatible trace elements appears to reflect an increase in their partition coefficients with increasing Al^IV in the clinopyroxene; with an increase in Al₂O₃ from 1.5 to 4.0 wt.% during ∼20% crystal fractionation over a temperature decrease of ∼100°C being associated with more that a threefold increase in the partition coefficients of Th, Zr, REE, and Y. The magnitude of these increases may indicate that the substitution of these trace elements into clinopyroxene is better modeled in some natural systems by a local charge balance model, rather than the distributed charge model that better replicates the results of annealed experiments. These findings indicate that the effect of Al on the partition coefficients of incompatible trace elements in clinopyroxene may be under appreciated in natural magmatic systems and that the application of experimentally determined clinopyroxene partition coefficients to natural systems must be done with caution.  相似文献   

Arsenic contamination of groundwater and agricultural soil irrigated with the groundwater in Mekong Delta,Vietnam     

Yi Huang  Keisuke Miyauchi  Ginro Endo  Le Dinh Don  Nguyen Cong Manh  Chihiro Inoue 《Environmental Earth Sciences》2016,75(9):757

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Monitoring land surface and cover in urban and peri-urban environments using digital aerial photography     

Peter Caccetta  Simon Collings  Andrew Devereux  Kassell Hingee  Don McFarlane  Anthony Traylen 《International Journal of Digital Earth》2016,9(5):457-475

This paper describes the development of a system for decimetre-scale monitoring of land-surface and land-cover in urban and peri-urban environments. We describe our methodology that comprises the application of highly automated processing and analysis methods to digital aerial photography. The approach described in this paper addresses a monitoring need by providing the ability to generate change information at a spatial resolution suitable for urban, peri-urban and coastal areas, where an increasing percentage of the worlds’ population dwells. These areas are dynamic, with many environmental issues associated with planning, service provision, resource management and allocation, as well as monitoring regulatory compliance. We present a system based on standardised data and methods, which is able to track and communicate changes in features of interest in a way that has not been previously possible. We describe the methodology and then demonstrate its feasibility by applying it to geographic areas of planning and policy relevant size (the order of tens of thousands of square kilometres). We demonstrate the approach by applying it to the problem of urban forest assessment.  相似文献   

Net deficits and the case for aquacultural geography     

Jonathan R Barton  Don Stanifordt† 《Area》1998,30(2):145-155

Summary The crisis in capture fisheries has placed an increased onus on aquaculture to supply the world fish demand. The advancing role of culture relative to capture fisheries has precipitated environmental and socio-economic transformations. Geographers have paid scant attention to these developments. This paper provides a literature review and proffers a research agenda for aquacultural geography.  相似文献