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Organochlorine concentrations were measured in white-sided dolphins, pilot whales, and their prey from the Gulf of Maine and used to identify species, tissue, and gender differences, and trophic transfer trends, in bioaccumulation. Polychlorinated biphenyl concentrations ([PCB]) in dolphin blubber (13 +/- 7.1 micrograms/g fresh wt.) were twice those in pilot whales, but pesticide concentrations (20 +/- 13 micrograms/g fresh) were similar between species. 4,4'-DDE, trans-non-achlor, Cl6(153) and Cl6(138) concentrations were highest. Skin tissues had more recalcitrant organochlorines than the internal organs. Male dolphins bioaccumulated higher concentrations of nonmetabolizable PCBs and hexachlorocyclohexane (HCH) isomers, whereas pilot whales had no gender-related differences in bioaccumulation. Pilot whales, mackerel, and herring had proportionately higher concentrations of DDTs, whereas [PCB] were higher in dolphins and squid. Although these odontocetes feed at the same trophic level and store a similar suite of contaminants, dolphins bioaccumulated higher and potentially hazardous 4,4'-DDE and PCB concentrations from food in their more geographically restricted range. 相似文献
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We present results of laboratory experiments to study the behavior of liquids moving in unsaturated wide-aperture fractures. A 5-mm-thick glass plate cut with a 1.7-mm aperture was used as a fractured rock analog to study behavior of film and capillary droplet flow modes. Flow rates ranged between 0.6 and 6.0 ml/min. Variability in the ambient barometric pressure, resulting from weather conditions, seemed to play a role in the natural selection of flow mode. For droplet mode, constant input conditions resulted in highly variable transport properties within the fracture. The advancing meniscus exhibited a dynamic contact angle that was a function of the droplet speed and much larger than the static contact angle. Flow rate was reduced due to the larger contact angle. Analytical expressions for droplet velocity and flow capacity are presented as a function of the dynamic rather than the static contact angle. 相似文献
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Because of frequent discrepancies between the available experimental data and the measured composition of alkali chloride aqueous solutions coexisting with two alkali feldspars in high temperatures-low pressures natural systems, a systematic investigation of the system KAlSi3O8-NaAlSi3O8-KCl-NaCl-H2O has been undertaken.Experiments have been carried out at temperatures from 300 °C to 660 °C, pressures from 0.2 to 2 kbar and total chloride concentrations ranging from 0.05 to 14 moles/kg H2O.No effect of pressure on the feldspars solvus could be detected. Smoothing the experimental data on the basis of the regular assymetric solid solution model yields a critical temperature of 661°C and a critical composition of Or0.36Ab0.64.The equilibrium constant C = m
KCl/m
NaCl does not depend on total chloride molality, as long as the aqueous solution is homogeneous. But, in the miscibility gap (liquid+vapour) of the fluid, C is always lower in the vapour than in the liquid. The higher the temperature and the lower the pressure, the more striking this effect. For instance, at 500 ° C C
vaqour/C
liquid = 1 above 1 kb, 0.9 at 600 bars, 0.8 at 500 bars, 0.7 at 400–450 bars.The effect of pressure can be neglected in homogeneous fluids and in the liquid phase of unmixed fluids, but it is very important in the vapour phase (dilute solutions at low pressure).The selected values of C
max are (±0.01) 300 ° C0.083; 400 ° C0.139; 500 ° C0.200; 600 ° C0.264; 650 ° C0.298Such a behaviour of the fluid at low pressures explains the abnormally low values of m
KCl/m
NaCl measured in many natural hydrothermal systems. A new mechanism of alkali metasomatism (especially potassic alterations) is also proposed, taking into account the unmixing of alkali chloride aqueous solutions. This model seems particularly interesting in late magmatic hydrothermal processes, such as those occuring in porphyry type deposits. 相似文献
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Subsurface video footage can be used as a successful identification tool for various marine organisms; however, processing of such information has proven challenging. This study tests the use of automated software to assist with photo-identification of the great white shark Carcharodon carcharias in the region of Gansbaai, on the south coast of South Africa. A subsurface photo catalogue was created from underwater video footage. Single individuals were identified by using pigmentation patterns. From this catalogue, two images of the head for each individual were inserted into automated contour-recognition software (Interactive Individual Identification System Beta Contour 3.0). One image was used to search the database, the other served as a reference image. Identification was made by means of a contour, assigned using the software to the irregular border of grey and white on the shark's head. In total, 90 different contours were processed. The output provided ranks, where the first match would be a direct identification of the individual. The method proved to be accurate, in particular for high-quality images where 88.24% and 94.12%, respectively, were identified by two independent analysts as first match, and with all individuals identified within the top 10 matches. The inclusion of metadata improved accuracy and precision, allowing identification of even low-quality images. 相似文献
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Erick R. Burns Maria I. Dragila John S. Selker Ronald B. Guenther Jean-Yves Parlange Noam Weisbrod 《Advances in water resources》2007
The Buckingham–Darcy Law is used to describe fluid flow in unsaturated porous media at low Reynolds number. In order to provide a priori corrections to this law, a process thermodynamic approach is utilized to ascertain the functional dependence. Using this knowledge, corrections to the hydraulic conductivity coefficient are proposed and compared with available data. The proposed corrections substantially predict the observed behavior of flow of high concentration (saturated) sodium chloride solutions in porous media. During the derivation, physical principles consistent with the thermodynamics of the system were utilized. A review of these principles and their results provides an alternative form of the generalized Gibbs–Duhem Relation for continuous processes, indicating that the identical equivalence to zero is unlikely to occur for dissipative processes. Further, the postulated Gibbs and Gibbs–Duhem Relations indicate that special differential operators need to be used for continuous processes rather than the usual use of a generic differential. 相似文献
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Daniel Kurtzman Lior Netzer Noam Weisbrod Ellen R. Graber Daniel Ronen 《Ground water》2011,49(2):275-279
Electrical conductivity (EC) logs were obtained by both open‐borehole logging and passive multilevel sampling (MLS) in an observation borehole penetrating the Coastal Aquifer in Tel Aviv, Israel. Homogeneous vertical velocities for a 70‐m thick subaquifer were approximated from each profile using a steady‐state advection‐diffusion model. The open‐borehole log led to an overestimation of the steady‐state upward advective flux of deep brines (vertical velocity of 0.95 cm/yr as compared to 0.07 cm/yr for the MLS profile). The combination of depth‐dependent data and the suggested simple modeling approach comprises a method for assessing the vertical location of salinity sources and the nature of salt transport from them (i.e., advective vs. diffusive). However, in this case, the easily obtained open‐borehole logs should not be used for collecting depth‐dependent data. 相似文献
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Segmented line-source multi-tracer injection is suggested as an effective method for assessing groundwater velocities and flow directions in subsurfaces characterized by high water flux. Modifying the common techniques of injecting a tracer into a well became necessary after point-source natural and forced gradient tracer tests ended with no reliable information on the local groundwater flow. The tracer's line-source increases the likelihood of success of the test and could provide additional information regarding the lateral heterogeneity of the aquifer. In a field experiment conducted in the northwestern part on the Dead Sea coast, tracers were injected into an 8-m-long line injection system perpendicular to the assumed flow direction. The injection system was divided into four separate segments with four different tracers. An array of five boreholes located within a 10 × 10 m area downstream was used for monitoring the tracers' transport. Two dye tracers (uranine and Na naphthionate) were injected in a long pulse of several hours into two of the injection pipe segments. Two other tracers (Rhenium oxide and Gd-DTPA) were instantaneously injected into the other two segments. The tracers were detected 0.7 to 2.3 h after injection in four of the five observation wells, located 2.3 to 10 m away from the injection system. The groundwater velocity was determined to be ～80 to 170 m/d, based on the recoveries of the tracers. The groundwater flow direction was derived based on the arrival of the tracers and was found to be quite consistent with the apparent direction of the hydraulic gradient. 相似文献
10.
A review of colloid transport in fractured rocks 总被引：3，自引：0，他引：3
WEISBROD Noam 《山地科学学报》2012,9(6):770-787
Recent recognition of colloid and colloidassociated transport of strongly sorbing contaminants in fractured rocks highlights the importance of exploring the transport behavior of colloids under conditions prevailing in the field.The rapid transport of colloids through fractured rocks-as affected by the hydraulic properties of the flow system,the properties of fracture surface and the geochemical conditionshas not been sufficiently elucidated,and predictions of colloid transport through fractures have encountered difficulties,particularly at the field scale.This article reviews the current understanding of the mechanisms and modeling of colloid transport and retention in fractured rocks.Commonly used experimental techniques and approaches for conducting colloid transport experiments at different scales,ranging from the laboratory to the field scale,are summarized and commented upon.The importance of various interactions(e.g.,dissolution,colloid deposition,generation,mobilization and deposition of filling materials within fractures) between the flowing solution and the fracture walls(in many cases,with skin or coating on the host rock at the liquid-solid interface) has been stressed.Colloid transport through fractures of high heterogeneity has not yet been well understood and modeled at the field scale.Here,we summarize the current knowledge and understanding accumulated in the last two decades in regard to colloid and colloidassociated transport through fractures.Future research needs are also discussed. 相似文献