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Groundwater samples from 288 domestic wells in Barry County, Michigan, were analyzed for 33 inorganic chemical parameters. Variations in chemical composition were investigated by considering the possible effects of human impact, aquifer type (bedrock vs glacial drift), chemical evolution along groundwater flow paths, and glacial landform type (moraine vs outwash). Approximately 25 percent of the glacial drift wells were classified as degraded by human impact and were excluded from further analysis of chemical variation. Two-sample tests comparing individual concentrations from drift and bedrock aquifers suggest that groundwater in the Marshall Sandstone aquifer is derived from local recharge through the glacial drift. This conclusion is supported by generalized groundwater flow patterns recognized for the two aquifers.Concentrations in both aquifers were examined in relation to generalized flow paths derived from water level data and also by classification of wells as recharge, transition, and discharge. No spatial concentration trends in major ions were detected, although iron concentrations do appear to increase from recharge to discharge areas. Declining redox potential along groundwater flow paths may explain this trend.The possible influence of glacial landform type was investigated by comparing concentrations of wells in moraines with those in outwash deposits. Wells in moraines have significantly higher concentrations of most parameters, perhaps due to higher content of finer, more chemically reactive sediment grains. 相似文献
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Rennie B. Kaunda Ronald B. Chase Alan E. Kehew Karlis Kaugars James P. Selegean 《Environmental Earth Sciences》2010,60(7):1545-1558
A back propagation artificial neural network approach is applied to three common challenges in engineering geology: (1) characterization
of subsurface geometry/position of the slip (or failure surface) of active landslides, (2) assessment of slope displacements
based on ground water elevation and climate, and (3) assessment of groundwater elevations based on climate data. Series of
neural network models are trained, validated, and applied to a landslide study along Lake Michigan and cases from the literature.
The subsurface characterization results are also compared to a limit equilibrium circular failure surface search with specific
adopted boundary conditions. It is determined that the neural network models predict slip surfaces better than the limit equilibrium
slip surface search using the most conservative criteria. Displacements and groundwater elevations are also predicted fairly
well, in real time. The models’ ability to predict displacements and groundwater elevations provides a foundational framework
for building future warning systems with additional inputs. 相似文献
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AQUIPRO, a PC-based method, was used to assess aquifer vulnerability using digital water well logs. The AQUIPRO model is a parameter/factor weighting system for rating the pollution potential of an aquifer. This method uses the well depth, as well as the clay and partial clay thickness in a well, to generate pollution potential scores. In this model, aquifer protection increases as the AQUIPRO vulnerability scores increase and ground water pollution potential decreases. Computerized water well records of 2435 domestic wells with partial chemistry data were used to determine the ground water pollution potential of Kalamazoo County, Michigan. Theoretically, low AQUIPRO pollution potential scores should have more frequent occurrences of ground water contamination events than areas with high AQUIPRO scores with similar land-use, well construction, and well densities. The relative AQUIPRO scores were compared with the frequency of occurrences of nitrate-N in ground water wells. The average nitrate-N concentrations within each relative AQUIPRO vulnerability scores category were also compared. The results indicate that domestic wells containing 5 mg/L or more nitrate-N showed a positive correlation between the frequency of occurrences of nitrate-N and relative decrease of AQUIPRO (r2 = 0.99) vulnerability scores. In other words, as the ground water pollution potential increases, the occurrence frequency of nitrate-N also increases. Furthermore, the results show that as the relative AQUIPRO (r2 = 0.96) vulnerability scores decrease, the mean nitrate-N concentrations also increase. 相似文献
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Concentration trends of monitor wells utilized in monitored natural attenuation at petroleum underground storage tank sites
can be used to predict achievement of regulatory standards if the data approximate a first-order decline trend. However, declining
concentration trends often display seasonal and other fluctuations that complicate trend interpretation. Seasonal correlations
between concentration and water-level elevation, including in-phase and inverse relationships, constitute one of the most
common types of variation. The in-phase fluctuations are most common for monitor wells located in or near the source area
of the release. This relationship may be the result of increased contact with the smear zone in the source area during periods
of high water table. Conversely, inverse trends of water-level elevation and concentration are most common in downgradient
wells beyond the limit of the source area. In a year long study of short-term fluctuations in BTEX and other parameters in
a downgradient monitor well, the data suggest that the winter/spring recharge event significantly controls the concentration
trends of BTEX as well as inorganic compounds in the well. Recharge and associated water table rise began in late fall and
were soon followed by a slug of inorganic ions strongly influenced by road salt application. This slug of recharge diluted
the concentrations of petroleum compounds and alkalinity (bicarbonate). Electron acceptors including oxygen, nitrate, and
sulfate, which is a component of road salt, are also contributed to the water table during recharge. Oxygen and nitrate were
not detected in the monitor well samples and were most likely consumed quickly in biodegradation reactions at the top of the
contaminant plume. Sulfate peaked during winter/spring recharge and then slowly declined during the summer and fall, along
with redox potential. Alkalinity (bicarbonate) increased during this period, which may represent the coupled oxidation of
organic carbon to CO2 with sulfate as the electron acceptor. BTEX concentrations peaked in the fall probably due to the lack of diluting recharge.
The slow changes in concentration over the summer and fall months, interpreted to be caused by biodegradation, contrast with
the rapid changes associated with dilution during the recharge event. 相似文献
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Alan E. Kehew Stephanie K. Ewald John M. Esch Andrew L. Kozlowski 《Boreas: An International Journal of Quaternary Research》2013,42(2):442-462
Tunnel valleys are common throughout the terrain of the Saginaw Lobe of the Laurentide Ice Sheet in southern Michigan. The set of valleys described in this paper is regularly spaced in a radial pattern behind the Kalamazoo Moraine, an ice‐marginal position formed during retreat from the Last Glacial Maximum. These valleys are divided into proximal and distal groups lying north and south, respectively, of a major river valley that cross‐cuts the tunnel valleys at right angles. Based on a series of rotasonic borings and core analysis, the proximal valleys are shallow, contain minimal sediment fill, and overlie fine‐grained diamicton and glaciolacustrine sediment, whereas the distal valleys are deeply incised into the substrate and are partially filled with coarse sediment. The distal valleys terminate within a broad zone of high‐relief, hummocky topography representing stagnation and collapse behind the Kalamazoo ice margin. The proximal valleys occur within a more subdued landscape located farther from the ice margin. Although some elements of existing genetic models are consistent with these valleys, none appears to be completely compatible with their stratigraphy and morphology. Initial incision of the valleys could have involved short‐lived moderate‐ to high‐discharge flows, followed by deposition during or after the events. The deep incision and thick, coarse sediment in distal valleys in the stagnant marginal zone probably involved supraglacial meltwater draining to the bed as the margin downwasted. Fining‐upward eskers inset into the valleys were formed by flows of declining energy in small late‐stage conduits. 相似文献
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Nathaniel A. Barnes Alan E. Kehew R. V. Krishnamurthy Carla M. Koretsky 《Environmental Earth Sciences》2011,62(5):1027-1038
High iron concentrations create water quality problems for municipal use in glacial drift aquifer units. The chemical evolution
of oxic groundwater in shallow aquifer units to anoxic groundwater in deeper aquifer units, in which soluble Fe(II) is stable,
is attributed to coupled reduction of Fe(III) on aquifer solids with oxidation of organic carbon. The objective of this study
was to characterize the distribution of organic carbon in aquifer and aquitard sediments to determine the availability of
potential electron donors to drive these reactions. To do this, four complete rotasonic cores in a glacial aquifer/aquitard
system were sampled at close intervals for analyses of grain-size distribution and organic carbon content. The results indicate
significantly higher organic carbon concentrations in diamicton (till) units that function as aquitards, relative to coarse-grained
aquifer units. In addition, readily reducible iron content in the diamicton units and lower aquifer unit materials is sufficient
to produce far more dissolved iron than is present in the aquifer. Groundwater evolves to the level of iron reduction as a
terminal electron-accepting process as it moves downward through aquitard units along flow paths from upland recharge areas
to downgradient discharge areas. Deeper aquifer units are therefore unlikely to contain groundwater with low iron concentration. 相似文献
10.
Abdou Abouelmagd Mohamed Sultan Neil C. Sturchio Farouk Soliman Mohamed Rashed Mohamed Ahmed Alan E. Kehew Adam Milewski Kyle Chouinard 《Quaternary Research》2014
Sixteen groundwater samples collected from production wells tapping Lower Cretaceous Nubian Sandstone and fractured basement aquifers in Sinai were analyzed for their stable isotopic compositions, dissolved noble gas concentrations (recharge temperatures), tritium activities, and 14C abundances. Results define two groups of samples: Group I has older ages, lower recharge temperatures, and depleted isotopic compositions (adjusted 14C model age: 24,000–31,000 yr BP; δ18O: − 9.59‰ to − 6.53‰; δ2H: − 72.9‰ to − 42.9‰; < 1 TU; and recharge T: 17.5–22.0°C) compared to Group II (adjusted 14C model age: 700–4700 yr BP; δ18O: − 5.89‰ to − 4.84‰; δ2H: − 34.5‰ to − 24.1‰; < 1 to 2.78 TU; and recharge T: 20.6–26.2°C). Group II samples have isotopic compositions similar to those of average modern rainfall, with larger d-excess values than Group I waters, and locally measurable tritium activity (up to 2.8 TU). These observations are consistent with (1) the Nubian Aquifer being largely recharged prior to and/or during the Last Glacial Maximum (represented by Group I), possibly through the intensification of paleowesterlies; and (2) continued sporadic recharge during the relatively dry and warmer interglacial period (represented by Group II) under conditions similar to those of the present. 相似文献