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Vic Wing-Hang Tsang 《Marine pollution bulletin》2009,58(10):1462-156
A mild, low-temperature analytical approach based on sonication assisted extraction coupled with HPLC electrospray ionization triple quadrupole tandem mass spectrometry has been developed for the simultaneous qualitative and quantitative determination of the four Irgarol-related s-triazine species, namely Irgarol-1051, M1, M2 and M3, in coastal sediments and Green-lipped mussel samples. Mild extraction conditions were necessary for the preservation of the thermally unstable M2. The Multiple Reaction Monitoring (MRM) mode of detection by ESI-MS/MS enabled reliable qualitative identification and sensitive quantitative determination of those s-triazines. This determination method was applied to evaluate the degree of Irgarol-1051 contamination in the sediments and biota of the coastal environment of Hong Kong - one of the busiest maritime ports in the world. All the four s-triazine species were observed in all of the samples. This is the first time that the newly identified M2 and M3 are detected in coastal sediments and biota tissues. 相似文献
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Writing Analytic Element Programs in Python 总被引：1，自引：0，他引：1
The analytic element method is a mesh-free approach for modeling ground water flow at both the local and the regional scale. With the advent of the Python object-oriented programming language, it has become relatively easy to write analytic element programs. In this article, an introduction is given of the basic principles of the analytic element method and of the Python programming language. A simple, yet flexible, object-oriented design is presented for analytic element codes using multiple inheritance. New types of analytic elements may be added without the need for any changes in the existing part of the code. The presented code may be used to model flow to wells (with either a specified discharge or drawdown) and streams (with a specified head). The code may be extended by any hydrogeologist with a healthy appetite for writing computer code to solve more complicated ground water flow problems. 相似文献
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Ischadites lindstroemi Hinde 1884 is described from the Ordovician Daylesford Formation (lower part of the Bowan Park Group) of central western New South Wales. The species characterises a distinctive unit in the formation, occurring in bands throughout the unit. From a study of the associated lithofacies and their stratigraphic distribution in the limestones, an interpretation of the environment in which the species lived is presented. The species is considered to have inhabited a shallow‐water, lime‐mud environment, which was off‐shore and marginal to calcarenite shoals. 相似文献
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We present results of a design study performed for the Saylorville Wellfield in Iowa, which is owned and operated by the Des Moines Water Works. The purpose of this study was to estimate wellfield capacity and provide a preliminary design for two radial collector wells to be constructed in the outwash aquifer along the Des Moines River near Saylorville, Iowa. After a field investigation to characterize the aquifer, regional two-dimensional and local three-dimensional, steady-state groundwater flow modeling was performed to locate and design the wells. This modeling was the foundation for design recommendations based on the relative performance of 12 collector well designs with varying lateral numbers, elevations, screen lengths, and orientations. For each site, alternate designs were evaluated based on model estimates of the capacity, the percent of surface water captured, and the production per unit length of screen. Many of our results are consistent with current design practices based on experience and intuition, but our methods allow for a quantitative approach for comparing alternate designs. Although the results are site-specific, the framework for evaluating the hydraulic design of the Saylorville radial collector wells is broadly applicable and could be used at other riverbank filtration sites. In addition, many of the conclusions from this design study may apply at other sites where construction of radial collector wells is being considered. 相似文献
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Vic Duke 《GeoJournal》1999,49(1):17-24
The paper is concerned with decreasing state ownership in post-communist Eastern Europe and a concomitant decline in the proportion
employed in the state sector. Many individuals have shifted into private sector employment, self-employment or unemployment.
The literature on sectoral shifts in employment in Eastern Europe is summarised, and from this it is argued that there will
be a growing differentiation between private sector employees and state sector employees in economic, social and political
terms. Data is then analysed based on a survey in 1995 of around 1000 households in each of four cities – Budapest, Prague,
Warsaw and Krakow. Similar patterns emerged in the four cities. Consistent differences in working conditions and rewards are
already evident between the self-employed, private sector and state sector. These conflicting economic interests are reflected
in contrasting attitudes to the economy and polity amongst those employed in different sectors.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Multilayer analytic element modeling of radial collector wells 总被引：1，自引：0，他引：1
A new multilayer approach is presented for the modeling of ground water flow to radial collector wells. The approach allows for the inclusion of all aspects of the unique boundary condition along the lateral arms of a collector well, including skin effect and internal friction losses due to flow in the arms. The hydraulic conductivity may differ between horizontal layers within the aquifer, and vertical anisotropy can be taken into account. The approach is based on the multilayer analytic element method, such that regional flow and local three-dimensional detail may be simulated simultaneously and accurately within one regional model. Horizontal flow inside a layer is computed analytically, while vertical flow is approximated with a standard finite-difference scheme. Results obtained with the proposed approach compare well to results obtained with three-dimensional analytic element solutions for flow in unconfined aquifers. The presented approach may be applied to predict the yield of a collector well in a regional setting and to compute the origin and residence time, and thus the quality, of water pumped by the collector well. As an example, the addition of three lateral arms to a collector well that already has three laterals is investigated. The new arms are added at an elevation of 2 m above the existing laterals. The yield increase of the collector well is computed as a function of the lengths of the three new arms. 相似文献
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LABORATORY MEASUREMENTS OF THE EFFECTS OF VISCOSITY ON SHORT WATER WAVE SPECTRA AND IMPLICATION FOR RADAR REMOTE SENSING OF THE OCEAN SURFACE 总被引：1，自引：0，他引：1
Using an X-band radar and a mechanical short wave generator, we measured the dependenceof radar return power on the viscosity of water which was adjusted by changing the watertemperature. From the measurements we drew two inferences: (1) the spectral density of short waterwaves, F, depends strongly on the viscosity of waterF(v)=F_0~mwhere is normalized viscosity, and m=-1.72; and (2) the normalized radar cross section, σ_0(dB), dependsstrongly on the water temperature△σ_0 (dB)=O.217△TAnalyses indicate that these dependencies can be observed in the field only at low wind conditionsat which the Bragg scattering is a dominant mechanism for producing the radar return signals. Theresults of this study can be used to interpret the sharp variability in radar cross section across a watertemperature front and SAR images of oeeanic phenomena. 相似文献