ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01005.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTBrackish‐water contamination of the Patuxent aquifer has been a serious water‐quality problem in Baltimore, Maryland, since the early 1900's. The Patuxent aquifer presently contains a circular plume of brackish‐water contamination that is about 5 miles in diameter. This plume is centered on the Patapsco River estuary and is characterized by chloride concentrations that range up to 5,000 milligrams per liter. Borehole data demonstrate that the Arundel Clay Formation, which overlies the Patuxent and functions as a confining bed, has been breached by Pleistocene river channels in the Baltimore area. These erosional channels, which have been subsequently filled with relatively permeable sediments, provide conduits for brackish water to seep from the Patapsco River into the Patuxent aquifer when aquifer water levels arc lower than river water levels.A two‐dimensional areal solute‐transport model of the Patuxent aquifer was used to estimate the future movement of the brackish‐water plume based on alternative strategies of aquifer use. Model simulations suggest that the plume will not spread rapidly if present pumping patterns are continued. Furthermore, sharply curtailing pumpage in the Baltimore area will probably not reduce the size of the plume, although this strategy may slightly decrease the spreading rate. While the plume is presently remaining nearly stationary, new pumping centers southeast of Baltimore could cause brackish water to migrate in that direction, significantly increasing the size o

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01006.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTThe Environmental Protection Agency and the Tanner's Council of America jointly initiated a five‐year project in September 1980 to investigate the feasibility of using land treatment to dispose of chromium tanning sludges. These sludges contain high concentrations of Cr, in the range of 21,000 to 55,000 ppm on a dry weight basis. Chromium could migrate in soil waters at a land treatment site as either a soluble Cr (VI) species, HCrO4 or CrO42, or as Cr (III) or Cr (VI) in soluble complexes with organic or inorganic substances. Field measurements of Cr fluxes at an experimental test site near Santa Cruz, California indicate that Cr in tannery sludges exhibits a very low mobility. Less than 0.1% of the total Cr applied to a test plot was transported through the upper soil zone during a three‐month period. However, the sludge applications introduced high concentrations of nitrates and major cations. Estimates of contaminant fluxes based on measured concentrations in soil water collected with porous cup samplers contain large uncertainties. In addition to potential errors in moisture flux computations, chemical reactions in the cups can significantly alter the composition of soil‐water sa

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01007.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTA radial injection tracer experiment was conducted in Scarborough, Ontario, as part of a program to evaluate the feasibility of using a confined aquifer, underlying the Canada Centre building site for the storage of chilled and/or heated water for a seasonal thermal energy storage system. Water was injected into the aquifer for five hours before a salt solution was added as a tracer. This tracer was injected into the aquifer over a period of four hours at a rate of 22.7 1/s. Injection of the water into the aquifer continued for an additional 1 5 hours following injection of the salt solution. Samples were collected from a monitoring well located 6.54 meters from the injection well. A sampling device was installed prior to the injection experiment to permit the collection of water samples at different elevations within the screened portion of the monitoring well. The samples which were collected at five different elevations at various times, both during and following the salt injection, were analyzed for specific conductance and chloride concentration. The data suggest that the aquifer is inhomogeneous and that the ratio of the hydraulic conductivity to porosity increases from the lowest sampling port to the highest sampling port near the top of the aquifer. A linear relationship was obtained between the time of arrival of the tracer and the apparent resistivity of the formation. This linear relationship was used to calibrate the apparent resistivity log of the injection well to provide a continuous characterization of the vertical variation in the hydraulic conductivity/porosity ratio across the full thickness of the aquifer. Data analysis also suggests that the dispcrsivity parameter varies linearly with the time of arrival of the tracer. The combination of geophysical logs with tracer experiments may permit detailed characterization of the hydraulic properties of aquifers.

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01008.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTThis paper examines two eases of surface‐water/ ground‐water interrelationships, one in Beaufort County, North Carolina and one in Ramona, California. In each case the author has to make a differential diagnosis between alternate solutions rendered by hydrologic methods.In the first ease, the author proves that the pumping and subsequent wastage to the ocean of 65 mgd in order to operate the Texas Gulf Sulphur phosphate mine, in all likelihood poses no threat to the environment.In the second case, the author has attempted to obtain, by means of the theory of ground‐water flow, an estimate of the physiographic volume of the Santa Maria creek ground‐water basin in Ramona. He has submitted the outcome of his calculations to the test of compatibility with the results of an actual pumping test, and with pumping records made available by the Ramona Municipal Water District. The outcome shows a water storage capacity of the order of 4,600 AF for the entire basin.In order to correlate recharge of the basin directly with the precipitation on the basin, a hydrograph analysis has been done for the 20 largest runoff‐producing months of the streamflow records 1965–1982. From this study it follows that the average (annual) recharge to the basin is of the order of 1,340 AF/yr and that the physiographic volume, as derived previously, is amply adequate to absorb th

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01009.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTThe transient movement of contaminant under pumpage and recharge conditions in steady ground‐water flow in a vertical cross section of a confined aquifer is simulated using a finite‐element numerical model based on Galerkin technique. Various factors like time step, space increment, and boundary condition affecting the accuracy of the numerical solution are considered in validating results of the numerical model with results of an analytical solution. The solution with the application problem illustrates the effectiveness of subsequent operation of pumpage on the movement of contaminant downstream of the point of inject

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01010.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTTransient electromagnetic sounding methods (TEM) have several advantages over DC resistivity soundings. The principal advantage is that sounding depths several times the receiver‐transmitter spacing can be achieved, resulting in less cumbersome field work and more flexible sounding site selection. The TEM method was tested using a commercially available instrument (Geonics EM‐37) in the Gulf Springs region of west‐central Florida to locate the saltwater interface in the Floridan Aquifer. The Floridan is a thick (200 m), unconfined, karstic, carbonate aquifer within the study area. High annual rainfall and internal drainage create a deep and dynamic interface.Eighty transient soundings were completed in 18 field days. Seventy‐one soundings used a square 80 m × 80 m transmitter loop, and the other nine used a 160 m × 160 m coil. The interface was easily detected from a minimum depth of 60 m to its maximum depth of about 140 meters. Also, a high‐resistivity, low‐porosity zone was detected at depths ranging from 180–250 meters. The TEM data compare well with available chloride concentration data. The TEM interface corresponds to chloride values in excess of 200–400 mg/1. The sounding curves obtained suggest that with presently available instruments the TEM method is not well‐suited for shallow soundings (less

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01011.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTThe legal doctrines of reasonable use and correlative rights are the recognized standards for resolving legal conflicts between interfering agricultural ground‐water users in Arkansas. Assuring that an adequate saturated thickness exists for all interfering users throughout the ground‐water withdrawal season provides water users with a degree of protection from both a successful litigious charge of “unreasonable use” and a mandated curtailment of ground‐water withdrawal in a droughty season.The feasibility of maintaining a “target” saturated thickness and water‐table elevation by implementing a district‐wide sustained ground‐water withdrawal strategy has been previously demonstrated. Several models have been reported which create the spatially distributed sustained‐yield withdrawal strategies that will maintain those target levels. The development of satisfactory strategies requires knowledge of the minimum acceptable springtime saturated thickness for critical parts of the management district. This information can be gained through the iterative use of a dynamic ground‐water simulation model. In the iterative procedure, initial (springtime) saturated thickness is assumed. The change in saturated thickness resulting from withdrawals during the irrigation season is compared with an acceptability criterion. The assumed springtime saturated thickness is varied until the criterion is satisfied. The result is the minimum springtime saturated thickness needed for ground‐water users in a particular cell to achieve: (1) a measure of year‐round protection from successful litigation charging unreasonable use, and (2) some assurance that they will not need to curtail or limit ground‐water withdrawals during a droughty season.This procedure was applied to a 3‐mile by 3‐mile (5‐km by 5‐km) cell in the Arkansas Grand Prairie, an important rice‐ and soybean‐producing area. The results indicate that a minimum of 13 feet (4 m) of saturated thickness are desirable for the center of

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01012.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTMicrobial biomass, community structure and activity were determined in the subsurface horizons of four contrasting soil types common to Alabama. Biomass and community structure were determined by analyzing the fatty acids of the extractable phospholipids. Activity was estimated by measuring the rate of enzymatic hydrolysis of fluorescein diacetate (FDA). In all four soils, biomass and activity declined with increasing depth; however, the magnitude and pattern of this decline varied as a function of soil type. Biomass concentrations in the lower Ap horizon ranged from 8.2 to 18.0 nmoles phospholipid/g dry wt soil. In the deepest subsoil horizons, the range was 0.0085 to 0.059 nmoles phospholipid/g dry wt soil. The rate of FDA hydrolysis was highly correlated with biomass (r=0.90). Polyenoic fatty acids, which are present only in cukaryotic microorganisms, were found in all horizons; however, their relative abundance differed as a function of soil type. Stepwise regression analysis revealed that soil characteristics could explain 89 and 82% of the variation in biomass and activity, respectively. The results indicated that the vertical distribution of microorganisms in a soil profile differs greatly as a function of soil type. Hence, soil type may be an important determinant as to whether potential ground‐water pollutants are biodegraded as they pass through the unsaturated zone of a soil profil

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01013.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTMore than 100 steeply dipping or vertical Mesozoic fault zones, which cut across Paleozoic igneous and metamorphic rocks, have been reported in the Piedmont and Appalachians of the Carolinas. The present investigation deals with the hydrological problems encountered in exploring for ground water in the Pax Mountain Fault zone. This is the largest known Mesozoic fault in the Carolinas, having a length of more than 75 km and attaining a width of 1 km in places. Subsurface studies of seven wells, which were drilled along the axis of Pax Mountain, South Carolina, show that the composition of the fault rocks is much more complicated than was known heretofore. These rocks consist of angular particles of quartz and feldspar fault breccia enclosed in a kaolinitic clay gouge. They vary greatly in degrees of consolidation and permeability, and these variations were the cause of some serious ground‐water problems. Two wells were dry holes because the intergranular spaces of the breccia were clogged with clay and also because most of the joints were filled with secondary minerals. Three wells, which were drilled in more permeable, but poorly consolidated fault rocks, caved in at a depth of about 80 m just when they had encountered large volumes of water. Two of the seven wells produce potable water, but chemical analyses of the ground water showed that their turbidity values were 6.0 t.u. and 2.0 t.u., which exceed the limit of 1.0 recommended by the South Carolina Department of Health and Environmental Contro

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01014.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY