Magnetic resonance sounding applied to aquifer characterization   总被引：3，自引：0，他引：3  

Legchenko A  Baltassat JM  Bobachev A  Martin C  Robain H  Vouillamoz JM 《Ground water》2004,42(3):363-373

Magnetic resonance sounding (MRS) is distinguished from other geophysical tools used for ground water investigation by the fact that it measures a magnetic resonance signal generated directly from subsurface water molecules. An alternating current pulse energizes a wire loop on the ground surface and the MRS signal is generated; subsurface water is indicated, with a high degree of reliability, by nonzero amplitude readings. Measurements with varied pulse magnitudes then reveal the depth and thickness of water saturated layers. The hydraulic conductivity of aquifers can also be estimated using boreholes for calibration. MRS can be used for both predicting the yield of water supply wells and for interpolation between boreholes, thereby reducing the number of holes required for hydrogeological modeling. An example of the practical application of MRS combined with two-dimensional electrical imaging, in the Kerbernez and Kerien catchments area of France, demonstrates the efficiency of the technique.  相似文献   

Analytical and numerical models to explain steady rates of spring flow   总被引：1，自引：0，他引：1  

Swanson SK  Bahr JM 《Ground water》2004,42(5):747-759

Flow from some springs in former glacial lakebeds of the Upper Midwest is extremely steady throughout the year and does not increase significantly after precipitation events or seasonal recharge. Analytical and simplified numerical models of spring systems were used to determine whether preferential ground water flow through high-permeability features in shallow sandstone aquifers could produce typical values of spring discharge and the unusually steady rates of spring flow. The analytical model is based on a one-dimensional solution for periodic ground water flow. Solutions to this model suggest that it is unlikely that a periodic forcing due to seasonal variations in areal recharge would propagate to springs in a setting where high-permeability features exist. The analytical model shows that the effective length of the aquifer, or the length of flowpaths to a spring, and the total transmissivity of the aquifer have the greatest potential to impact the nature of spring flow in this setting. The numerical models show that high-permeability features can influence the magnitude of spring flow and the results demonstrate that the lengths of ground water flowpaths increase when high-permeability features are explicitly modeled, thus decreasing the likelihood for temporal variations in spring flow.  相似文献   

Changes in zooxanthellae density,morphology, and mitotic index in hermatypic corals and anemones exposed to cyanide   总被引：5，自引：0，他引：5  

Cervino JM  Hayes RL  Honovich M  Goreau TJ  Jones S  Rubec PJ 《Marine pollution bulletin》2003,46(5):573-586

Sodium cyanide (NaCN) is widely used for the capture of reef fish throughout Southeast Asia and causes extensive fish mortality, but the effect of NaCN on reef corals remains debated. To document the impact of cyanide exposure on corals, the species Acropora millepora, Goniopora sp., Favites abdita, Trachyphyllia geoffrio, Plerogyra sp., Heliofungia actinformis, Euphyllia divisa, and Scarophyton sp., and the sea anemone Aiptasia pallida were exposed to varying concentrations of cyanide for varying time periods. Corals were exposed to 50, 100, 300, and 600 mg/l of cyanide ion (CN(-)) for 1-2 min (in seawater, the CN(-) forms hydrocyanic acid). These concentrations are much lower than those reportedly used by fish collectors. Exposed corals and anemones immediately retracted their tentacles and mesenterial filaments, and discharged copious amounts of mucus containing zooxanthellae. Gel electrophoreses techniques found changes in protein expression in both zooxanthellae and host tissue. Corals and anemones exposed to cyanide showed an immediate increase in mitotic cell division of their zooxenthellae, and a decrease in zooxanthellae density. In contrast, zooxanthellae cell division and density remained constant in controls. Histopathological changes included gastrodermal disruption, mesogleal degradation, and increased mucus in coral tissues. Zooxanthellae showed pigment loss, swelling, and deformation. Mortality occurred at all exposure levels. Exposed specimens experienced an increase in the ratio of gram-negative to gram-positive bacteria on the coral surface. The results demonstrate that exposure cyanide causes mortality to corals and anemones, even when applied at lower levels than that used by fish collectors. Even brief exposure to cyanide caused slow-acting and long-term damage to corals and their zooxanthellae.  相似文献   

Assessment of the aesthetic quality of a selection of beaches in the Firth of Forth,Scotland     

Somerville SE  Miller KL  Mair JM 《Marine pollution bulletin》2003,46(9):1184-1190

The aesthetic quality of fourteen beaches in the Firth of Forth, Scotland was surveyed between May and July 2002 using a protocol designed by the UK's National Aquatic Litter Group (NALG). Local authority beach cleaning regimes influence the amount of litter found on beaches. Frequent and thorough beach cleaning is necessary to maintain high aesthetic standards. Bathing and amenity beaches achieved higher aesthetic quality than non-bathing and non-amenity beaches. The aesthetic quality of rural and urban beaches was very similar. The NALG protocol appears more complicated to use than other beach litter surveys. However, the classification system generates results that are easily interpreted by the general public. Furthermore, the NALG protocol could be combined with coastal zone management plans as a useful environmental performance indicator.  相似文献   

Determination of organohalogenated contaminants in liver of harbour porpoises (Phocoena phocoena) stranded on the Belgian North Sea coast     

Covaci A  Van de Vijver K  DeCoen W  Das K  Bouquegneau JM  Blust R  Schepens P 《Marine pollution bulletin》2002,44(10):1157-1165

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Influence of the Aznalcóllar mining spill on the vertical distribution of heavy metals in sediments from the Guadalquivir estuary (SW Spain)   总被引：2，自引：0，他引：2  

Riba I  DelValls TA  Forja JM  Gómez-Parra A 《Marine pollution bulletin》2002,44(1):39-47

The Natural Park of Do?ana and the Guadalquivir estuary were impacted by the release of 6 million cubic meters of acid waste after the mine-tailing spill in Aznalcóllar (Andalusia, SW, Spain). Here is presented the monitoring of the accidental spill on vertical distribution of heavy metals in the estuarine sediments. The total concentration of six metals (Fe, Mn, Zn, Cd, Pb, Cu), their chemical speciation and the organic carbon concentration were analyzed in sediment vertical profiles. The results obtained determine background levels similar to previously reported in the area. The analysis catalogues the impact of the accident on the estuary as acute and mainly associated with high concentrations of Zn and Cd. The recent enrichment in Zn and Cd and their geochemical association with the more mobile fractions of the sediment determine an environmental risk associated with the acute impact and detected in some of the areas of the estuary.  相似文献   

西澳大利亚州工业矿物资源及开发利用     

Feth.  JM 华建伟 《江苏地矿信息》1997,22(5):1-5

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碳酸盐岩沉积环境的地震解释     

方丹.  JM  王慧 《国土资源信息化》1989,(14):6-9

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Acquisition and processing of data for isotope-ratio-monitoring mass spectrometry     

Ricci MP  Merritt DA  Freeman KH  Hayes JM 《Organic Geochemistry》1994,21(6-7):561-571

Methods are described for continuous monitoring of signals required for precise analyses of 13C, 18O, and 15N in gas streams containing varying quantities of CO2 and N2. The quantitative resolution (i.e. maximum performance in the absence of random errors) of these methods is adequate for determination of isotope ratios with an uncertainty of one part in 10(5); the precision actually obtained is often better than one part in 10(4). This report describes data-processing operations including definition of beginning and ending points of chromatographic peaks and quantitation of background levels, allowance for effects of chromatographic separation of isotopically substituted species, integration of signals related to specific masses, correction for effects of mass discrimination, recognition of drifts in mass spectrometer performance, and calculation of isotopic delta values. Characteristics of a system allowing off-line revision of parameters used in data reduction are described and an algorithm for identification of background levels in complex chromatograms is outlined. Effects of imperfect chromatographic resolution are demonstrated and discussed and an approach to deconvolution of signals from coeluting substances described.  相似文献   

小型大地网的粗差检测     

Brown  JM 蓝荣钦 《武测译文》1993,(3):13-15

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