摘要:

ABSTRACTGround waters from the Cretaceous Chalk of east‐central England display hydrochemical zonation comprising four water types. These are, in the general direction of ground‐water flow; Type I – calcium bicarbonate (CaHCO3) waters undersaturated with respect to calcite, Type II – CaHCO3waters saturated with respect to calcite, Type III – waters showing sulfate (SO4) reduction and softening by ion exchange, and Type IV – saline waters. At first appearance these water types may be interpreted as related members in the classically recognized, long‐term sequence of natural chemical evolution of subsurface waters. This simple model, however, cannot be reconciled fully with all aspects of the hydrochemistry. For example, there is no satisfactory process that could explain an apparent depletion of chloride when moving from Type I to Type II waters, and transitional boundaries are absent between water Types II and III, and Types III and IV. Furthermore, the model lacks credibility in an area where recent geological events have radically disturbed the regional ground‐water flow regime. An alternative hydrochemical zonation model is proposed in which each water type evolves independently of adjacent water types as a function of its own unique aquifer flow history. This multistage model is supported by tritium and radiocarbon evidence and can be related to probable changes in the regional flow regime during the pas

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb02773.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTA natural gradient tracer test was conducted in an unconfined sandy aquifer at Borden, Ontario. N‐butyric acid, phenol, p‐chlorophenol, and dimethyl phthalate (DMP) were used as organic tracers at concentrations ranging from 70 to 100 ppm and chloride was used as a nonreactive tracer at a concentration of 243 ppm. Approximately 2,100 1 were injected below the water table and were monitored with a three‐dimensional network of bundle‐type, multilevel piezometers over a period of 60 days and once again after 204 days.The plume gradually split into two zones due to local heterogeneity. The centers of mass for the organic compounds migrated at essentially the same rate as chloride, but attenuated at different rates. Butyric acid and phenol attenuated the most rapidly. Chlorophenol attenuated only slightly faster than chloride and DMP attenuated at roughly the same rate as chloride. Sorption does not appear to be important in the system studied. Dispersion and biodegradation probably produced the observed attenuation of o

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb02774.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTGround‐water pollution by organic compounds has become a major environmental concern. Because the transport and fate of the organic pollutants may be influenced by microorganisms present in subsurface material, reliable measurements of the number of organisms in subsurface samples and their metabolic activity are needed. A special drilling rig and aseptic procedures have been developed by the Robert S. Kerr Environmental Research Laboratory of the United States Environmental Protection Agency to yield uncontaminated subsurface samples. The number of bacteria in subsurface samples has been determined by microscopic counting after acridine orange staining; the proportion of cells capable of respiration was determined by INT reduction. An independent measure of metabolic activity was obtained by measuring ATP extracted from the samples. A procedure and extradant for the extraction of ATP from subsurface material have been developed. The extractant contains reagents to reduce the loss of the extracted ATP. Subsurface samples from Oklahoma and Texas contain 106‐107cells per g of subsurface material (depths of 2–9 m). Both methods show that usually between 1 and 10% of the cells were metabolically active. Thus, significant numbers of metabolically active bacteria exist in subsurface material with the potential to modify pollu

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb02775.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTNitrate‐nitrogen (NO3‐N) concentrations and total (TC) and fecal coliform (FC) densities were determined in ground water from 268 household and stock wells in an 1100 mi2area of southeast Nebraska. Seventy‐one percent of the samples had NO3‐N concentrations above 10 mg/1 and/or TC densities ≥ 1/100 ml. Most of the NO3‐N contamination is from the dissolution of manure in barnyards and corrals. The average δ15N value was + 11.9%0for the 115 samples with NO3‐N levels in excess of 8.5 mg/1.Only 10% of the wells met Nebraska's criteria for private well construction. NO3‐N levels exceeded 10 mg/1 in 4% of these wells while 30% contained one or more TC/100 ml. The highest incidence of NO3‐N and coliform contamination occurred in dug or augered wells with open‐jointed casing. The rates were 47% and 80%, respectively.Low levels of atrazine were detected only in the poorly constructed wells. One wel

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb02776.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThe carbonate ions are present in the ground water of the Nile Delta region in very small amounts (0–96 ppm). These ions decrease or may be absent in the northern parts of the Delta. The bicarbonate contents range between 0 and 738 ppm, depending on the amount of CO2in water and following nearly the same trend as that of the carbonates. The pH values range between 5.5 and 8.5, where the increase of salinity content in the northern and western parts leads to its reduction, and the reverse happens towards the southern and eastern directions where the salinity decrease

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb02777.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTDeposits of low permeability are hydrologic barriers between reclaimed land and juxtaposed aquifers and should limit the impact of mining on ground‐water quality. Clay‐stone and mudstone in argillaceous facies of the Calvert Bluff Formation (lower Eocene, Wilcox Group) function as confining beds in the East Texas Basin. In the subsurface and at the outcrop, water in argillaceous deposits is brackish to saline. Samples of vadose water from the outcrop of confining beds at the Big Brown lignite mine in Freestone County, Texas, have a chloride concentration of up to 3,500 mg/l and total dissolved solids of up to 8,000 mg/l. Ground‐water composition evolved from Eocene sea water by seven‐ to nine‐fold dilution with rain water. Ion exchange, pyrite oxidation, and calcite dissolution further modified water composition. The amount of recharge through the vadose zone where confining layers crop out is probably negligible over an extremely long time. Meteoric flushing in reclaimed land at the surface mine is many times greater than that in unmined mudstone deposits, and the chemical composition of vadose water in reclaimed land is changed by further dilution and water‐roc

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb02778.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThis paper numerically demonstrates and quantifies the importance of capillary‐fringe and variable specific yield phenomena in ground‐water recharge estimations. A one‐dimensional numerical experiment consisting of a soil either with a capillary fringe or without it was set up using a finite‐element code. A prescribed infiltrating flux was superimposed on top of the soil column, and the resulting unsaturated‐saturated water flow was observed. By assuming a single value for specific yield, recharge is usually overestimated. For two cases considered in this study, the errors involved in ground‐water recharge estimations by using such an assumption ranged from 88 to 330 times the simulated recharge, when variable specific yield is considered. This study also clearly demonstrates the effect of a constant specific yield value on the behavior of the water table rise, the total amount of which as well as the rate of such rise are underestimated under that assumption. In addition, under that assumption, the timing of the water table rise is out of phase with the timing of rech

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb02779.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTGround‐water samples from two heavily fertilized sites in Suffolk County, New York, were collected through the 1978 growing season and analyzed for nitrate‐N concentrations and nitrogen‐isotope ratios. Six wells were at a potato farm; six were on a golf course. The purpose of this study was to determine whether the15N/14N ratios (δ15N values) of fertilizer are increased during transit from land surface to ground water to an extent which would preclude use of this ratio to distinguish agricultural from animal sources of nitrate in ground water.Ground water at both sites contained a greater proportion of15N than the fertilizers being applied. At the potato farm, the average δ15N value of the fertilizers was 0.2%0; the average δ15N value of the ground‐water nitrate was 6.2 %0. At the golf course, the average δ15N value of the fertilizers was ‐5.9%0, and that of ground‐water nitrate was 6.5%0. The higher δ15N values of ground‐water nitrate are probably caused by isotopic fractionation during the volatile loss of ammonia from nitrogen applied in reduced forms (NH+4and organic‐N).The δ15N values of most ground‐water samples from both areas were less than 10%0, the upper limit of the range characteristic of agricultural sources of nitrate; these sources include both fertilizer nitrate and nitrate derived from increased mineralization of soil nitrogen through cultivation. Previous studies have shown that the S15N values of nitrate derived from human or animal waste generally exceed 10%0. The nitrogen‐isotope ratios of fertilizer‐derived nitrate were not altered to an extent that would make them indistinguishable from animal‐waste‐d

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb02780.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTGround‐water quality, determined by 10 samplings of 14 wells within a 7.4 km2watershed during 1973–1982, was related to land use and geology. The wells represent forest and cropland use associated with three geologic zones. Nitrates, chloride and phosphate concentrations were much higher in ground waters underlying cropland. The mean concentrations ranged from five to seven times those observed in ground water underlying forests. The contamination pattern is consistent with that computed from a nutrient balance, based on known fertilizer and manure use on local croplands. Downgradient from the primary agricultural area, a geologic zone exists through which ground water from agricultural sources must pass to reach the stream. In this zone, the nitrate, chloride, and phosphate concentrations are greatly decreased due to mixing and dilution. The chemical nature of these ground waters reflects more the geochemistry of local geologic deposits than the impact of cropland use.A ground‐water flow system was hypothesized, based on known geologic, hydrologie, and geometric properties. The flow system is supported by the chemical

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb02781.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.LGWRES is a simplistic program, for the HP‐41C series of programmable calculators, to determine the lifetime of ground‐water reserves in years; total use over the lifetime of the reserves; precentage of domestic and agricultural uses; additional years of possible agricultural use realized by dedicating the domestic use to agriculture; and percentages of total use, domestic use, and agricultural use that could be sustained by annual replenishment to the ground‐water reserves, within the “safe yield

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1985.tb02782.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY