ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1993.tb00435.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1993.tb00436.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1993.tb00437.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1993.tb00438.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1993.tb00439.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1993.tb00440.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractGround water samples for a hydrochemical investigation were collected from 92 observation wells completed in a shallow, unconfined aquifer in southeastern North Dakota. The samples showed predominantly an increase in HCO3‐ (positive bias) and both a pH decrease (positive bias) and a pH increase (negative bias) from field to lab. Positive pH bias generally was associated with ground water characterized by dissolved‐solids concentrations less than 400 mg/L. Negative pH bias generally was associated with ground water characterized by dissolvedsolids concentrations greater than 400 mg/L.Observed HCO3‐ bias from field to lab slightly distorted ion balance distribution. Excess anions greater than 2 percent generally corresponded to increased HCO3‐ from field to lab.Observed HCO3‐ and pH bias significantly distorted the distribution of calcite saturation indices. Samples with dissolved‐solids concentrations less than 400 mg/L that generally showed a positive pH bias had a mean change in calcite saturation index of ‐0.214 (toward undersaturation). Samples with dissolved‐solids concentrations greater than 400 mg/L that generally showed a negative pH bias had a mean change in calcite saturation of +0.132 (toward over saturation).Calcite saturation indices were much more sensitive to observed pH bias than to observed HCO3‐ bias. Linear regression analysis indicates % percent of the variability in calcite saturation index change from field to lab is attributed to change in pH from field to lab. Field pH should be used to compute calcite

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1993.tb00441.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPumping test data for surficial aquifers are commonly analyzed under the assumption that the base of the aquifer corresponds to the bottom of the test wells (i.e., the aquifer is truncated). This practice can lead to inaccurate hydraulic conductivity estimates, resulting from the use of low saturated thickness values with transmissivity estimates, and not accounting for the effects of partially penetrating wells. Theoretical time‐drawdown data were generated at an observation well in a hypothetical unconfined aquifer for various values of saturated thickness and were analyzed by standard curve‐matching techniques. The base of the aquifer was assumed to be the bottom of the pumping and observation wells. The overestimation of horizontal hydraulic conductivity was found to be directly proportional to the error in assumed saturated thickness, and to the (actual) ratio of vertical to horizontal hydraulic conductivity (Kv/Kh). Inaccurately high estimates of hydraulic conductivity obtained by aquifer truncation can lead to overestimates of ground water velocity and contaminant plume spreading, narrow capture zone configuration estimates, and overestimates of available ground water resour

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1993.tb00442.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWhen the purpose of aquifer testing is to yield data for modeling aqueous mass transport, pumping tests and gradient measurement can only partially satisfy characterization requirements. Effective porosity, ground water flow velocity, and the vertical distribution of hydraulic conductivity within the aquifer are left as unknowns. Single well tracer methods, when added to the testing program, can be used to estimate these parameters. A drift, and pumpback test yields porosity and velocity, and point‐dilution testing yields depth‐discrete hydraulic information, A single emplacement of tracer into a test well is sufficient to conduct both tests. The tracer tests are facilitated by a simple method for injecting and evenly distributing the tracer solution into a wellbore, and by new ion‐selective electrode instrumentation, specifically designed for submersible service, for monitoring the concentration of tracers such as br

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1993.tb00443.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractLincoln's municipal wellfield consists of 44 wells located adjacent to the Platte River near Ashland, Nebraska. The herbicide atrazine was monitored in the river and two transects of monitoring, wells. The amount of atrazine transported down the Platte River in 1989, 1990, and 1991 was shown to increase each year. Induced recharge from the Platte River results in movement of atrazine from the river into the aquifer. A 21‐day lag time was determined for the movement of atrazine from the river to a transect of monitoring wells 10 feet West of the bank. The role that colloids play on the transport of atrazine was determined to be insignificant. A small percentage of atrazine found in the river was determined to come from rain water. The infiltration of agrichemical‐contaminated river water was shown to significantly reduce the quality of raw water and finished water being produced by the adjacent aqui

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1993.tb00444.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY