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1.
Unbaited phreatic traps are a promising new method for sampling subterranean limnofauna. The aim of this study is to evaluate whether such trap systems are suitable to gather representative samples of the physico-chemical parameters and the invertebrate fauna of the aquifer. Fifteen traps, installed in five groundwater bores, and four traps located in the hyporheic zone, were sampled twice monthly over a 1 year period (June 2003–June 2004). Water samples were removed in three separated fractions (hose, trap and aquifer water), analysed for physico-chemical and faunal characteristics and compared with one another. The study was carried out in the Nakdong River floodplain, Korea. Physico-chemical characteristics of trap and aquifer were similar, but differed greatly from the hose samples. Abundances of fauna inside the traps were higher than in the aquifer, whereas there were no differences in taxonomic composition of the trap and aquifer samples. Biases of abundances suspected due to the use of traps were negligible in the groundwater, though it is recommended that comparisons between groundwater and hyporheic abundances ascertained by traps be handled cautiously.  相似文献   

2.
Hans Jürgen Hahn   《Limnologica》2005,35(4):248-261
(1) A new method of sampling stygofauna is presented, along with some data derived from applications in the field. Numerous bores were sampled for fauna, water and bacteria, down to a depth of 7.50 m. Two or 3 unbaited traps were fixed to a central pole within the bore. The traps consist of an inert plastic chamber with holes in the upper parts and gaskets near the bottom and near the lid of each trap. The content of the traps was emptied monthly using a pump.

(2) While the taxonomic composition of the trap samples seemed to be comparable to the surrounding groundwater, estimation of abundances in the traps might differ, with a potential over-estimation in the traps, in particular in sparsely populated aquifers. Detailed comparative studies on the performance of the method are, as yet, lacking.

(3) Trap data of invertebrate communities reflect hydraulic changes, and highest abundances and taxa richness were found near the water table. They decreased rapidly with depth, implying that small-scale stratified sampling is possible.

(4) The technique is cheap, reliable, simple and rapid to use, and allows simultaneous sampling of hydro-chemical, faunal and microbial samples. The method seems to be suitable for a wide range of sub-surface waters, where the water table is shallower than 8 m.

Keywords: Stygofauna; Groundwater; Phreatic traps; Sampling method; Hydrological exchange  相似文献   


3.
Hans Jürgen Hahn   《Limnologica》2006,36(2):119-137
Between June 2001 and December 2002, 18 hyporheic and groundwater bores were sampled for fauna and environmental data using phreatic traps. The bores were situated in three different natural geographic regions in Palatinate, Southwestern Germany.Faunal data correlated with the relative amount of detritus, bacterial abundances and the standard deviation of temperature, while very few and weak correlations were found with physical–chemical variables. Dissolved oxygen was assumed to be a limiting factor for most metazoans with a critical concentration at around 0.5–1 mg l−1.To quantify the strength of the hydrological exchange with surface water and its effects on fauna, a so-called GW-Fauna-Index was developed and calculated using the relative amount of detritus, standard deviation of temperature, and oxygen concentration. From all environmental data and on all spatial scales, this index best explained the total faunal abundance and taxonomic richness.To describe the availability of organic aliments in the groundwater, the terms of “alimonic” and “alimony” [from lat. alimonium=(food) supply] were proposed.Although stygofauna was different in the geographic regions investigated, the GW-Fauna-Index was independent from these regional particularities. Using the GW-Fauna-Index, three groups of groundwater habitats could be classified according to the alimonic conditions. From oligo-alimonic group I samples, fauna was mostly absent, while meso-alimonic group II samples were prevailingly populated by stygobites, and eu-alimonic group III samples by ubiquists and stygoxenes. Total abundances and taxonomic richness increased significantly from group I to group III. Group I samples were characterized by low index values, group II samples by intermediate and group III samples by high values.The GW-Fauna-Index provides promising perspectives for application, but needs some improvement. First of all, detritus should be analysed quantitatively and qualitatively, rather than semi-quantitatively. Also, a standard protocol for sampling has to be developed.  相似文献   

4.
Standard methodologies for sampling the physicochemical conditions of groundwater recommend purging a bore for three bore volumes to avoid sampling the stagnant water within a bore and instead gain samples representative of the aquifer. However, there are currently no methodological standards addressing the amount of purging required to gain representative biological samples to assess groundwater bacterial and viral abundances. The objective of this study was to examine how bacterial and viral abundances change during the purging of bore volumes. Six bores infiltrating into unconfined aquifers were pumped for five or six bore volumes each and bacteria and virus‐like particles (VLPs) were enumerated from each bore volume using flow cytometry. In examination of the individual bores trends in bacterial abundances were observed to increase, decrease, or remain constant with each purged bore volume. Furthermore, triplicates taken at each bore volume indicated substantial variations in VLP and bacterial abundances that are often larger than the differences between bore volumes. This indicates a high level of small scale heterogeneity in microbial community abundance in groundwater samples, and we suggest that this may be an intrinsic feature of bore biology. The heterogeneity observed may be driven by bottom up processes (variability in the distribution of organic and inorganic nutrients), top‐down processes (grazing and viral lysis), physical heterogeneities in the bore, or technical artifacts associated with the purging process. We suggest that a more detailed understanding of the ecology underpinning this variability is required to adequately describe the microbiological characteristics of groundwater ecosystems.  相似文献   

5.
Groundwater bores act as traps. Net samplers are regularly used for sampling this type of trap for fauna. To enable direct comparisons of faunal communities in groundwater bores and stream sediments, stream sediment tubes were built similar to groundwater bores and were sampled with net samplers for fauna. These stream sediment tubes consisted of a tube anchored in the stream sediment, also called interstitial space. To test the efficacy of this trap method in stream sediments, it was compared to another type of trap, Hahn's trap. Faunal communities sampled by a net in the stream sediment tubes did not differ hugely from fauna in Hahn's trap samples. Physical and chemical factors of sampled water in both the stream sediment tubes, the surrounding interstitial sediments and the second type of traps, Hahn's traps, showed that water in both the tubes and Hahn's traps was closely related to interstitial water. The net sampler is inexpensive and easy to handle. It is suggested that sampling stream tubes with nets may be an appropriate method for long‐term monitoring studies.  相似文献   

6.
The colloidal borescope consists of a set of lenses and miniature video cameras capable of observing natural particles in monitoring wells. Based on field observations of these particles, it appears possible to measure in situ groundwater velocity in a well bore. Field observations have shown that directional measurements using the colloidal borescope are generally in good agreement with expected flow directions. However, the magnitude of flow velocity is higher compared with values based on conventional test methods. High relative flow velocities, even after correction factors have been applied to compensate for well bore effects, are believed to be due to preferential flow zones in the surrounding aquifer. Low flow zones exhibit swirling multidirectional flow that does not allow for a linear velocity measurement. Consequently, groundwater flow velocities measured by the colloidal borescope in heterogeneous aquifers will be biased toward the maximum velocity values present in the aquifer. A series of laboratory experiments was conducted to assess the reliability of the instrument. Based on this work, a seepage velocity correction factor ( ) of 1–4 was found for quantifying groundwater seepage velocity in the adjacent aquifer from observations in a well bore. Laboratory measurements also indicate that preferential flow in the surrounding aquifer dominates flow in the well. Results of this work suggest the possibility of quantifying higher-flow velocities associated with preferential flow zones in the subsurface.  相似文献   

7.
In the sediments of a southwestern German headwater, pumping and two types of unbaited traps were compared with respect to their suitability for the sampling of interstitial meiofauna. The aim of the study was to discover whether the type-2 trap, having been developed for universal use, could be utilised in the hyporheic zone, as well as in groundwater. Trap samples demonstrate both greater abundance and taxonomic richness than those samples obtained by pumping, though very few differences could be detected between the two types of trap. The taxonomic composition, however, was found to be very similar for all three sampling methods. Other researchers also observed a high similarity of stygofaunal communities between pumped groundwater and the water of the bores, which act as traps. This would imply that not only do trap samples as well or better reflect community structure of the surrounding sediment than does pumping, but also that the type-2 trap is, indeed, suitable for the sampling of meiofauna in both the hyporheic zone and in groundwater.  相似文献   

8.
Groundwater management decisions are often founded upon estimates of aquifer hydraulic properties, recharge and the rate of groundwater usage. Too often hydraulic properties are unavailable, recharge estimates are very uncertain, and usage is unmetered or infrequently metered over only recent years or estimated using numerical groundwater models decoupled from the drivers of drawdown. This paper extends the HydroSight groundwater time-series package ( http://peterson-tim-j.github.io/HydroSight/ ) to allow the joint estimation of gross recharge, transmissivity, storativity, and daily usage at multiple production bores. A genetic evolutionary scheme was extended from estimating time-series model parameters to also estimating time series of usage that honor metered volumes at each production bore and produces (1) the best fit with the observed hydrograph and (2) plausible estimates of actual evapotranspiration and hence recharge. The reliability of the approach was rigorously tested. Repeated calibration of models for four bores produced estimates of transmissivity, storativity, and mean recharge that varied by a factor of 0.22-0.32, 0.13-0.2, and 0.03-0.48, respectively, when recharge boundary effects were low and the error in monthly, quarterly, and biannual metered usage was generally <10%. Application to the 30 observation bores within the Warrion groundwater management area (Australia), produced a coefficient of efficiency of ≥0.80 at 22 bores and ≥0.90 at 12 bores. The aquifer transmissivity and storativity were reasonably estimated, and were consistent with independent estimates, while mean gross recharge may be slightly overestimated. Overall, the approach allows greater insights from the available data and provides opportunity for the exploration of usage and climatic scenarios.  相似文献   

9.
Hydraulic properties of deeply weathered basement rocks and variably weathered sedimentary materials were measured by pumping and slug-test methods. Results from over 200 bores in 13 catchments, and eight pumping-test sites across the eastern and central wheatbelt of Western Australia were analysed. Measurements were made in each of the major lithological units, and emphasis placed on a ubiquitous basal saprolite aquifer. Comparisons were made between alternative drilling and analytical procedures to determine the most appropriate methods of investigation.

Aquifers with an average hydraulic conductivity of 0.55 m day−1 occur in variably weathered Cainozoic sediments and poorly weathered saprolite grits (0.57 m day−1). These aquifers are separated by an aquitard (0.065 m day−1) comprising the mottled and pallid zones of the deeply weathered profile. Locally higher values of hydraulic conductivity occur in the saprolite aquifer, although after prolonged periods of pumping the values decrease until they are similar to those obtained from the slug-test methods. Hydraulic conductivities measured in bores drilled with rotary auger rigs were approximately an order of magnitude lower than those measured in the same material with bores drilled by the rotary air-blast method.

Wheatbelt aquifers range from predominantly unconfined (Cainozoic sediments), to confined (saprolite grit aquifer). The poorly weathered saprolite grit aquifer has moderate to high transmissivities (4–50 m2 day−1) and is capable of producing from less than 5 to over 230 kl day−1 of ground water, which is often of a quality suitable for livestock. Yields are influenced by the variability in the permeability of isovolumetrically weathered materials from which the aquifer is derived.

The overlying aquitard has a low transmissivity (< 1 m2 day−1), especially when deeply weathered, indurated and silicified. The transmissivity of the variably weathered sedimentary materials ranges from less than 0.5 m2 day−1 to over 10 m2 day−1, depending on the texture of the materials and their position within the landscape. Higher transmissivity zones may occur as discrete layers of coarser textured materials. The salinity of the saprolite and sedimentary aquifers ranges from less than 2000 mgl−1 to greater than 250000 mgl−1 (total dissolved solids; TDS), depending on position within the landscape. Secondary soil salinization develops when groundwater discharge occurs from either saprolite or sedimentary aquifers.  相似文献   


10.
This study explores linkages between the microbial composition and hydrochemical variables of pristine groundwater to identify active redox conditions and processes. Two confined aquifers underlying the city of Qianjiang in the Jianghan Plain in China were selected for this study, having different recharge sources and strong hydrochemical gradients. Typical methods for establishing redox processes according to threshold concentration criteria for geochemical parameters suggest iron or sulphate reduction processes. High‐throughput 16S rRNA sequencing was used to obtain diversity and taxonomic information on microbial communities. Instead of revealing iron‐ and sulphate‐reducing bacteria, salt‐ and alkali‐tolerant bacteria, such as the phylum Firmicutes and the class Gammaproteobacteria, and in particular, the family Bacillaceae, were dominant in the downstream groundwater of the first aquifer that had high ion concentrations caused by the dissolution of calcite and dolomite; meanwhile, the heterotrophic microaerophilic families Comamonadaceae and Rhodocyclaceae prevailed in the upstream groundwater of the first aquifer. Sulphate‐reducing bacteria were extremely abundant in the upstream groundwater of the second aquifer, as the SO42? concentration was especially high. Methanogens and methanotrophs were predominant in the downstream groundwater of the second aquifer even though the concentration of SO42? was much higher than 0.5 mg L?1. The microbial communities, together with the geochemical parameters, indicated that the upstream region of the first aquifer was suboxic, that Fe(III) and Mn(IV) reductions were not the main redox processes in the downstream groundwater of the first aquifer with high Fe and Mn concentrations, and that the redox processes in the upstream and downstream regions of the second confined aquifer were SO42? reduction and methanogenesis, respectively. This study expands understanding of the linkages between microbial communities and hydrogeochemistry in pristine groundwaters and provides more evidence for identifying active redox conditions and processes.  相似文献   

11.
Geochemical evaluation of the sources and movement of saline groundwater in coastal aquifers can aid in the initial mapping of the subsurface when geological information is unavailable. Chloride concentrations of groundwater in a coastal aquifer near San Diego, California, range from about 57 to 39,400 mg/L. On the basis of relative proportions of major‐ions, the chemical composition is classified as Na‐Ca‐Cl‐SO4, Na‐Cl, or Na‐Ca‐Cl type water. δ2H and δ18O values range from ?47.7‰ to ?12.8‰ and from ?7.0‰ to ?1.2‰, respectively. The isotopically depleted groundwater occurs in the deeper part of the coastal aquifer, and the isotopically enriched groundwater occurs in zones of sea water intrusion. 87Sr/86Sr ratios range from about 0.7050 to 0.7090, and differ between shallower and deeper flow paths in the coastal aquifer. 3H and 14C analyses indicate that most of the groundwater was recharged many thousands of years ago. The analysis of multiple chemical and isotopic tracers indicates that the sources and movement of saline groundwater in the San Diego coastal aquifer are dominated by: (1) recharge of local precipitation in relatively shallow parts of the flow system; (2) regional flow of recharge of higher‐elevation precipitation along deep flow paths that freshen a previously saline aquifer; and (3) intrusion of sea water that entered the aquifer primarily during premodern times. Two northwest‐to‐southeast trending sections show the spatial distribution of the different geochemical groups and suggest the subsurface in the coastal aquifer can be separated into two predominant hydrostratigraphic layers.  相似文献   

12.
Shallow groundwater temperature response to climate change and urbanization   总被引：4，自引：0，他引：4  
Groundwater temperatures, especially in shallow (quaternary) aquifers respond to ground surface temperatures which in turn depend on climate and land use. Groundwater temperatures, therefore, are modified by climate change and urban development. In northern temperate climate regions seasonal temperature cycles penetrate the ground to depths on the order of 10–15 m. In this paper, we develop and apply analytic heat transfer relationships for 1-D unsteady effective diffusion of heat through an unsaturated zone into a flowing aquifer a short distance below the ground surface. We estimate how changes in land use (urban development) and climate change may affect shallow groundwater temperatures. We consider both long-term trends and seasonal cycles in surface temperature changes. Our analysis indicates that a fully urbanized downtown area at the latitude of Minneapolis/St. Paul is likely to have a groundwater temperature that is nearly 3 °C warmer than an undeveloped agricultural area at the same geographic location. Pavements are the main cause of this change. Data collected by the Minnesota Pollution Control Agency (MPCA) in the St. Cloud, MN area confirm that land use influences groundwater temperatures. Ground surface temperatures are also projected to rise in response to global warming. In the extreme case of a doubling of atmospheric carbon dioxide (2 × CO2 climate scenario), groundwater temperatures in the Minneapolis/St. Paul metropolitan area could therefore rise by up to 4 °C. Compounding a land use change from “undeveloped” to “fully urbanized” and a 2 × CO2 climate scenario, groundwater temperatures are projected to rise by about 5 °C at the latitude of Minneapolis/St. Paul.  相似文献   

13.
Surface water is a scarce resource in Namibia with about sixty percent of Namibia's population dependent on groundwater for drinking purposes. With increasing population, the country faces water challenges and thus groundwater resources need to be managed properly. One important aspect of Integrated Water Resources Management is the protection of water resources, including protection of groundwater from contamination and over-exploitation. This study explores vulnerability mapping as a basic tool for protecting groundwater resources from pollution. It estimates groundwater vulnerability to pollution in the upper Niipele sub-basin of the Cuvelai-Etosha in Northern Namibia using the DRASTIC index. The DRASTIC index uses GIS to estimate groundwater vulnerability by overlaying different spatially referenced hydrogeological parameters that affect groundwater contamination. The study assesses the discontinuous perched aquifer (KDP) and the Ohangwena multi-layered aquifer 1 (KOH-1). For perched aquifers, point data was regionalized by a hydrotope approach whereas for KOH-1 aquifer, inverse distance weighting was used. The hydrotope approach categorized different parts of the hydrogeological system with similar properties into five hydrotopes. The result suggests that the discontinuous perched aquifers are more vulnerable than Ohangwena multi-layered aquifer 1. This implies that vulnerability increases with decreasing depth to water table because contaminants have short travel time to reach the aquifer when they are introduced on land surface. The nitrate concentration ranges between 2 and 288 mg/l in perched aquifers while in Ohangwena multi-layered aquifer 1, it ranges between 1 and 133 mg/l. It was observed that perched aquifers have high nitrate concentrations than Ohangwena 1 aquifer, which correlates well with the vulnerability results.  相似文献   

14.
Major‐ion compositions of groundwater are employed in this study of the water–rock interactions and hydrogeochemical evolution within a carbonate aquifer system. The groundwater samples were collected from boreholes or underground tunnels in the Ordovician limestone of Yanzhou Coalfield where catastrophic groundwater inflows can be hazardous to mining and impact use of the groundwater as a water supply. The concentration of total dissolved solid (TDS) ranged from 961 to 3555 mg/l and indicates moderately to highly mineralized water. The main water‐type of the middle Ordovician limestone groundwater is Ca‐Mg‐SO4, with SO42‐ ranging from 537 to 2297 mg/l, and average values of Ca2+ and Mg2+ of 455.7 and 116.6 mg/l, respectively. The water samples were supersaturated with respect to calcite and dolomite and undersaturated or saturated with respect to gypsum. Along the general flow direction, deduced from increases of TDS and Cl‐, the main water–rock interactions that caused hydrogeochemical evolution of the groundwater within the aquifer were the dissolution of gypsum, the precipitation of calcite, the dissolution or precipitation of dolomite, and ion exchange. Ion exchange is the major cause for the lower mole concentration of Ca2+ than that of SO42‐. The groundwater level of Ordovician aquifer is much higher than that of C‐P coal‐bearing aquifers, so the potential flow direction is upward, and the pyrite in coal is not a possible source of sulfate; additional data on the stable sulfur and oxygen isotopic composition of the sulfate may be helpful to identify its origin. Although ion exchange probably accounts for the higher mole concentration of Na+ than that of Cl‐, the dissolution of aluminosilicate cannot be ruled out. The data evaluation methods and results of this study could be useful in other areas to understand flow paths in aquifers and to provide information needed to identify the origin of groundwater. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

15.
It was found in previous studies that groundwater levels may fluctuate as a temporal fractal. In this study numerical simulations of groundwater level fluctuations in an unconfined aquifer near a river were conducted to investigate the effects of aquifer heterogeneity and river stage variations on the fractal behavior of the water levels, h(t). Groundwater recharge was taken to be a white-noise process. The aquifer heterogeneity was simulated with a second-order stationary field of hydraulic conductivity (K) with an exponential variogram model. The results showed that groundwater levels fluctuate as a temporal fractal in both homogeneous and heterogeneous aquifers as long as K is less than 10 m/d. Most aquifers may indeed act as a fractal filter which takes a random non-fractal recharge inputs and produces a fractal responses of groundwater level fluctuations. A crossover in temporal scaling of h(t) may appear in more permeable aquifers. Fluctuations of the groundwater level in a homogeneous aquifer are dominated by the recharge process when the river stage is constant or by the river stage variations when the river stage varies in highly permeable aquifers. Heterogeneity plays an important role in the temporal scaling of h(t) in more permeable aquifers: the stronger the heterogeneity, the stronger the temporal scaling of h(t).  相似文献   

16.
Estimation of aquifer hydraulic properties is essential for predicting the response of an aquifer to extractions and hence estimating the availability of the groundwater resources. Aquifer tests are commonly used for the estimation of aquifer properties; however, they can be expensive and often only characterize the short‐term response of the aquifer. This paper presents a time series modelling approach to estimating aquifer hydraulic properties. It is applied to 42 bores monitoring an unconfined aquifer within an irrigation region of south‐eastern Australia, and the resulting probabilistic estimate of hydraulic properties are evaluated against pumping test estimates. It is demonstrated that the time series modelling can provide a reliable estimate of the hydraulic properties that are typical of a very long‐term pumping test. Furthermore, the application of the time series modelling to 42 bores provided novel insights into the aquifer heterogeneity. We encourage others to further test the approach and the source code is available from: http://www.mathworks.com/matlabcentral/fileexchange/48546‐peterson‐tim‐j‐groundwater‐statistics‐toolbox Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

17.
This paper summarises the results of the “Rhithron Ecology Group” meeting in Essen (March 2000), supplemented by a literature evaluation.An extended view of small mountain streams in Central Europe under “potentially natural conditions” is presented. We focus on the potential impact of natural transverse structures (debris dams and beaver dams) on stream morphology, hydrology, habitat composition and communities. Furthermore, impact of other stream morphological features, which are presently lacking in the Central European landscape, is described.We suggest that Central European mountain streams are characterised by a higher proportion of lentic zones under “potentially natural conditions”. Morphological degradation leads to a loss of lentic zones and to an increase of current velocities and corresponding changes in faunal composition, particularly higher abundance and proportion of rheophilic species and a decrease of species preferring lentic zones. This should be regarded in future stream assessment.  相似文献   

18.
Previous studies on tidal dynamics of coastal aquifers have focussed on the inland propagation of oceanic tides in the cross-shore direction, a configuration that is essentially one-dimensional. Aquifers at natural coasts can also be influenced by tidal waves in nearby estuaries, resulting in a more complex behaviour of head fluctuations in the aquifers. We present an analytical solution to the two-dimensional depth-averaged groundwater flow equation for a semi-infinite aquifer subject to oscillating head conditions at the boundaries. The solution describes the tidal dynamics of a coastal aquifer that is adjacent to a cross-shore estuary. Both the effects of oceanic and estuarine tides on the aquifer are included in the solution. The analytical prediction of the head fluctuations is verified by comparison with numerical solutions computed using a standard finite-difference method. An essential feature of the present analytical solution is the interaction between the cross- and along-shore tidal waves in the aquifer area near the estuary’s entry. As the distance from the estuary or coastline increases, the wave interaction is weakened and the aquifer response is reduced, respectively, to the one-dimensional solution for oceanic tides or the solution of Sun (Sun H. A two-dimensional analytical solution of groundwater response to tidal loading in an estuary, Water Resour Res 1997;33:1429–35) for two-dimensional non-interacting tidal waves.  相似文献   

19.
An analytic element approach is presented for the modeling of steady groundwater flow through multi-aquifer systems with piecewise constant aquifer and leaky layer properties. Different properties may be specified for domains bounded by closed polygons, referred to as polygonal inhomogeneities. The boundary of these inhomogeneities is modeled with two types of high-order line elements. First, a string of single-aquifer line-doublets is used; these elements cut through all aquifers and are valid both inside and outside the inhomogeneity. Second, two strings of multi-aquifer line-sinks are used, one string that is valid inside the inhomogeneity and one string that is valid outside; the comprehensive extraction of these line-sinks is zero at any point along the string. The proposed approach results in a comprehensive flow field of which the component normal to the boundary of the inhomogeneity is continuous across the boundary at any point. Within each individual aquifer, continuity of head and the component of flow normal to the boundary are met approximately across the boundary; the accuracy increases when the order of the line elements is increased and/or when shorter line elements are used. The proposed analytic element approach produces results that are virtually identical to the exact solution for a cylindrical inhomogeneity, and a high-resolution MODFLOW2000 model of two rectangular inhomogeneities with a shared boundary. The practical application of the approach is demonstrated through the solution of a problem with an irregularly shaped inhomogeneity with rivers crossing the inhomogeneity boundary.  相似文献   

20.
The bomb tritium (3H) distribution patterns in the aquifer beneath an abandoned landfill at the Canadian Forces Base (CFB) Borden, Ontario, and in a sandy aquifer at Whiteshell Nuclear Research Establishments (WNRE) Pinawa, Manitoba, all in Canada, were delineated in great detail. A sampling and monitoring network of multilevel samplers and bundle piezometers were used. The directions of groundwater flow were established, and the boundary between the tritiated and non-tritiated zones of the two aquifers were closely demarcated. Using a cumulative mass balance method, the3H input mass into the aquifers was compared with the3H mass in groundwater storage to estimate the percentages of annual groundwater recharge from 1953 to 1978. Two recharge calculations for theeffective recharge zone and thetotal recharge area of the aquifers as established from the flownet analysis, and the distributions of dissolved geochemical constitutents showed that theeffective recharge zone calculations gave higher values of 30.6 cm/yr for CFB Borden and 20.1 cm/yr for WNRE while thetotal recharge areas gave lower values of 19.1 and 10.1 cm/yr for the Borden and WNRE aquifers respectively. The two recharge values provide possible minimum and maximum recharge estimates for the two study areas.  相似文献   

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