ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00381.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00382.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00383.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00384.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractEighteen sites in South Carolina under investigation by the Superfund program were sampled to determine ambient ground water quality. Samples from 11 of 15 monitoring wells sampled with a bailer contained either caprolactam or Santowhite® (a registered trademark of the Monsanto Co.) or both organic compounds. A maximum of 540 μg/L of caprolactam and 780 μg/L of Santowhite was observed in the samples from the monitoring wells. None of the samples collected using dedicated submersible pumps at 28 other wells contained either compound.Caprolactam is used in the manufacturing of nylon cord, and Santowhite is used as an antioxidant in latex gloves. Therefore, it was suspected that the nylon cord used to raise and lower the bailer and the latex gloves that were worn during sampling may have contributed the caprolactam and Santowhite to the sample.An experiment using pH‐adjusted distilled water and private well water revealed that the nylon cord and the latex gloves may contribute contaminants to ground water samples. Research is needed into the potential for caprolactam and Santowhite to interfere with laboratory analyses in addition to the potential for absorption of contaminants by nylon cord. Until additional information is available, alternative materials or sampling techniques should be considered to minimize the potential impact of nylon cord and latex gloves on the quality of bailed sam

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00385.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA large‐scale retrospective ground water monitoring study'for metolachlor, 2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐ N‐(2‐methoxy‐l‐methylethyl) acetamide, was conducted. The study consisted of the collection and analysis of ground water samples from 240 existing wells (203 domestic farm wells and 37 monitoring wells) in selected areas of four states: the Dougherty Plains, Georgia; McLean County, Illinois; Floyd and Mitchell counties, Iowa; and the Central Sands area of Wisconsin. These locations were selected on the basis of high metolachlor use and hydrogeological vulnerability.The wells selected were all screened in the uppermost aquifer, were relatively shallow, and were located close to fields where metolachlor has historically been used. Pesticide handling and storage practices on the farms where the wells were located were documented, and wells were selected to avoid obvious point sources. The wells selected for monitoring included drinking water, irrigation and monitoring wells. Monitoring was at quarterly intervals for a one‐year period.Metolachlor was detected in 89 of 920 samples (9.7 percent) from 39 of 240 wells (16.3 percent) with a screening level (quantitation level) of 0.1 ppb. Ten out of 240 wells sampled (4.2 percent) showed detections in all sampling rounds.Of the samples analyzed, 5.1 percent had detections in the range between 0.1 and 0.5 ppb. Thus, non‐detections plus detections below 0.5 ppb accounted for 95.4 percent of all samples, and detections below 0.5 ppb represented more than half of all the detections found in the study (47 out of 89 detections). In the 31 samples where metolachlor was detected above 1.0 ppb, every detection could be related to a known or suspected point source.Based on the frequency and magnitude of metolachlor detections in this study, there appears to be no significant measurable field leaching of metolachlor to ground water under conditions of high product use and high ground water vulnerability. Instead, measurable detections of metolachlor, particularly those exceeding 1.0 ppb, appear to be as

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00386.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractLighter‐than‐water Non‐Aqueous Phase Liquids (LNAPLs), such as jet fuels or gasolines, are common contaminants of soils and ground water. However, the total volume and distribution of an LNAPL is difficult to accurately determine during a site investigation. LNAPL that is entrapped in the saturated zone due to fluctuating water table conditions is particularly difficult to quantify. Yet, the amount of entrapped product in the saturated zone is theoretically higher, per volume of soil, than the residual product in the unsaturated zone, and small amounts of LNAPL in the saturated zone can contaminate large volumes of ground water.The only method currently available to quantify the amount of LNAPL is direct soil‐core sampling combined with laboratory analysis of the fluid extracted from the soil cores. However, direct sampling of saturated ground water systems with conventional samplers presents a number of problems. In this study, a new sampler was developed that can be used to retrieve undisturbed soil and pore fluid samples from below the water table in cohesionless soils. The sampler uses carbon dioxide to cool the bottom of a saturated soil sample in situ to near freezing. Results of a field study where a prototype sampler was tested demonstrate the usefulness of a cryogenic sampler and show that the amount of LNAPL entrapped below the water table can be a significant part of the total LNAPL in t

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00387.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractBorehole‐geophysical logs can be used to estimate geohydrologic properties based on in situ measurement of rock and water properties. Estimates of properties of both formation and water, such as coefficient of diffusion, formation factor, cementation exponent, hydraulic conductivity, irreducible water content and specific yield can be assessed from borehole‐geophysical data and selected algorithms and graphs.Water properties, such as resistivity, sodium chloride concentration, viscosity and density, can also be estimated using data from borehole‐geophysical logs. Water resistivity using the spontaneous‐potential method can be estimated if an empirical correction for fresh water is applied.Estimates of formation properties, such as porosity and permeability, can also be made using borehole‐geophys

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00388.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA ground water monitoring study was conducted for the triazine herbicide simazine at 11 sites in the United States. The study used carefully selected, small‐scale sites (average size: about 33 acres) with documented product use and sensitive hydrogeological settings. The sites selected were Tulare County, California (two sites); Fresno County, California; Sussex County, Delaware; Hardee and Palm Beach counties, Florida; Winnebago County, Illinois; Jackson County, Indiana; Van Buren and Berrien counties, Michigan; and Jefferson County, West Virginia. These sites satisfied the following criteria: a history of simazine use, including the year prior to the start of the study; permeable soil and vadose zone; shallow depth to water; no restrictive soil layers above the water table; and gentle slopes not exceeding 2 percent. A variety of crop types, climates, and irrigation practices were included. Monitoring well clusters (shallow and deep) were installed at each site except in California and West Virginia, where only shallow wells were installed. Simazine was monitored at these sites at quarterly intervals for a two‐year period during 1986–1988.The results of the study showed that out of 153 samples analyzed, 45 samples showed simazine detections. A substantial majority of the detections (32 out of 45) occurred in Tulare, Fresno, and Jefferson counties. The detections in these areas were attributed to mechanisms other than leaching, such as drainage wells, karst areas, surface water recharge, or point source problems. An additional 11 detections in Van Buren County were apparently due to an unknown upgradient source. Only one detection (in Palm Beach County, Florida) near the screening level of 0.1 ppb was attributed to possible leaching. The results of this investigation support the hypothesis that simazine does not leach significantly under field use condi

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00389.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractGeologic site characterization is an important issue that must be addressed if details of contaminant transport in the subsurface are to be understood and predicted. Ideally, the formation heterogeneities at a site must be characterized at several scales. This paper deals with the smallest practical scale: core samples with cross‐sectional dimensions of a few inches. Historically, there has been great difficulty in obtaining relatively undisturbed cores of Unconsolidated coarse sand and gravel. In this study, 23 wells were installed at a field site in the Kansas River alluvium with hollow‐stem auger techniques. Six of these wells were cored through about 30 feet of coarse sand and gravel at depths of 40 to 70 feet using various techniques. A modified Waterloo sampler was employed with good success, using drilling mud in the auger flights to control heave and help hold in the sample. However, the use of heavy drilling mud has disadvantages (for example, the potential to contaminate the aquifer and cores) and recovery without sample loss is difficult because the procedure is sensitive to vibration and other mechanical forces. Without the use of drilling mud, the modified Waterloo sampler design was unsatisfactory because of relatively low recovery. In order to address this limitation, new sampler designs were developed and field tested. The most promising design does not require drilling mud, achieves a high recovery, and is not as sensitive to vibration and mechanical forces during recovery. The new design incorporates an inflatable bladder, located in the drive shoe, which closes off the end of the sampler. The deflated rubber bladder lies behind a plastic sample liner as the core begins to enter the sampler. Near the end of the 5‐foot sample drive, a piston extension triggers a release mechanism and allows a 4‐inch retraction of the plastic liner, resulting in the bladder being in direct contact with the sediment. The bladder is then inflated from the surface with nitrogen gas, closing off the bottom of the sampler and allowing recovery with minimal opportunity for sediments to fall out. Using this sampler, we have been able to consistently achieve about 86 percent out of a possible 90 percent recovery (drive shoe loss is 0.5 feet out of 5 feet due to bladder length and placement). The remaining 4 percent loss is due to compaction, premature piston movement, or wall friction preventing material movement into the sampler. These cores have been evaluated in the laboratory for determination of hydraulic conductivity, porosity, density, and particle‐size

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00390.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY