摘要:

AbstractA field study was conducted to assess purging requirements for dedicated sampling systems in conventional monitoring wells and for pumps encased in short screens and buried within a shallow sandy aquifer. Low‐flow purging methods were used, and wells were purged until water quality indicator parameters (dissolved oxygen, specific conductance, turbidity) and contaminant concentrations (chromate, trichloroethylene, dichloroethylene) reached equilibrium. Eight wells, varying in depth from 4.6 to 15.2 m below ground surface, were studied. The data show that purge volumes were independent of well depth or casing volumes. Contaminant concentrations equilibrated with less than 7.5 I. of purge volume in all wells. Initial contaminant concentration values were generally within 20 percent of final values. Water quality parameters equilibrated in less than 10 L in all wells and were conservative measures for indicating the presence of adjacent formation water. Water quality parameters equilibrated faster in dedicated sampling systems than in portable systems and initial turbidity levels were lowe

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1995.tb00509.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA soil‐gas survey was conducted at a gasoline service station and a former fire training facility to determine if surveying for hydrogen sulfide could be useful in locating nonaqueous phase hydrocarbon fuel in the subsurface. Relative; to total organic vapor, oxygen, and carbon dioxide distributions, detectable hydrogen sulfide concentrations were much more restricted to the suspected source vicinity at both sites. Appreciable levels of soil‐gas hydrogen sulfide. up to 600 Vppb. were observed in areas characterized by anaerobic or microaerophilic conditions having bulk oxygen levels below 4 percent. Based on the hydrogen sulfide distribution, nonaqueous phase hydrocarbon fuel was located at each site. These results suggest that soil‐gas surveying for hydrogen sulfide may help locale mobile or residual gasoline and other nonaqueous phase hydrocarbons in the subsu

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1995.tb00510.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractDiscrete‐depth ground water samplers are used during environmental screening investigations to collect ground water samples in lieu of installing and sampling monitoring wells. Two of the most commonly used samplers are the BAT Enviroprobe and the QED HydroPunch I, which rely on differing sample collection mechanics. Although these devices have been on the market for several years, it was unknown what, if any, effect the differences would have on analytical results for ground water samples containing low to moderate concentrations of chlorinated volatile organic compounds (VOCs). This study investigated whether the discrete‐depth ground water sampler used introduces statistically significant differences in analytical results. Our goal was to provide a technical basis for allowing the two devices to be used interchangeably during screening investigations.Because this study was based on field samples, it included several sources of potential variability. It was necessary to separate differences due to sampler type from variability due to sampling location, sample handling, and laboratory analytical error. To statistically evaluate these sources of variability, the experiment was arranged in a nested design. Sixteen ground water samples were collected from eight random locations within a 15‐foot by 15‐foot grid. The grid was located in an area where shallow ground water was believed to be uniformly affected by VOCs. The data were evaluated using analysis of variance.This study indicates that when sampling for short‐chain. chlorinated aliphatic compounds such as trichloroethylene, spatial variability from sampling location (over even a relatively small area) exceeds the differences between the Enviroprobe and HydroPuneh I. Therefore, the two sampling devices can be used interchangeably without reducing the internal consistency of the resulting data. However, when sampling for chlorinated aromatics, the choice of sampling device max introduce significant differences in the analytica

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1995.tb00511.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractWater samples from 240 private wells in rural Illinois were collected over one year and analyzed for 39 agricultural chemicals. Sampling was conducted to provide preliminary information to refine a plan for a statewide survey of the agricultural chemical contamination of rural private wells. Wells were sampled according to a stratified random sampling plan that included four classes of depth lo the uppermost aquifer material and two classes of well type. Depth lo uppermost aquifer material was defined as the depth from ground surface to a geologic material that, if saturated, could he used as an aquifer.Occurrence, defined as the presence of one or more target analytes in a well water sample above some specified concentration, was shown to be higher in large‐diameter bored or dug wells than in small‐diameter drilled wells. For small‐diameter wells, occurrence generally decreased as the depth to the uppermost aquifer material increased, In addition, depth to the uppermost aquifer material could be used to predict the occurrence of some individual agricultural chemicals, such as nitrate and atrazine, but could not be used to predict the occurrence of pielorarn or pesticides in small‐diameter wells.Of the 39 target analytes, 10 were detected at concentrations exceeding their respective minimum reporting levels. Nitrate and atrazine were the only compounds found at concentrations exceeding their respective maximum contaminant levels (MCLs) or U.S. EPA lifetime health advisory limits (HAI.s).A nonparametric statistical technique, contingency table analysis, identified factors associated with the occurrence of agricultural chemicals in three of the file study areas. Elevated specific conductance (>500 μmhos/cm) of the sampled water was strongly associated with the occurrence of agricultural chemicals. This association was common to all three study areas analyzed. Identification of the source of the specific conductance could help identify the dominant pathway for transport of agricultural chemicals to grou

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1995.tb00512.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1995.tb00514.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY