ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00348.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.tb00349.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.tb00350.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.tb00351.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.tb00352.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.tb00353.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.tb00354.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractContinuous high‐frequency marine seismic profiling was used to define the extent of geologic units in the offshore areas of J‐Field, Aberdeen Proving Ground, Maryland, during March and April of 1988. J‐Field is an area that was used by the U.S. Army for disposal of chemical warfare agents, munitions, and organic solvents from the 1950s through the 1970s. A major concern at this site is the subsurface migration of hazardous wastes into offshore areas and eventually into the Chesapeake Bay. A 150‐foot (45.7 meter) deep paleochannel containing Pleistocene age fluvial and estuarine sediments was identified from boreholes constructed onshore. The paleochannel sediments consist of three lithic units. From bottom to top these units consist of gravel and sand, massive silty and sandy clay, and interbedded sand and clay. The seismic profiles were used to identify the extent of these units and map them in offshore areas. An accurate knowledge of the distribution of the geologic units in onshore and offshore areas is important to the investigation because the coarse‐grained paleochannel sediments may provide a preferential flow path for contaminated ground water and the fine‐grained sediments may impede the movement of contaminants into deep

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00355.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractGrout continuity and the location of the bentonite seal and sand pack in PVC‐cased monitoring wells can be evaluated with cased‐hole geophysical density logs. This method relies upon density contrasts among various completion conditions and annular materials. Notably, the lack of annular material behind pipe (i.e., void space) creates a low‐density zone that is readily detected by borehole density measurements.Acoustic cement bond logging has typically been applied to the evaluation of cement in the annular space of completed oil and gas production wells, and in some cases to ground water monitoring wells. These logs, however, can only be obtained in the fluid‐filled portion of the borehole, and their interpretation is severely hindered by the presence of the micro‐annulus between casing and cement. The influence of the micro‐annulus on cement bond logs can be mitigated in steel‐cased wells by pressurizing the wellbore during acquisition of the log, but this procedure is not feasible in PVC‐cased monitoring wells. The micro‐annulus does not affect cased‐hole density logs or their interpretation.Empirical measurements made in the laboratory with density probes provide information on their depths of investigation and response to specific completion conditions. These empirical data, and general knowledge of the density of annular completion materials (sand, bentonite, cement), are used to support interpretations of cased‐hole density logs acquired in the field. Three field examples demonstrate the applicability of geophysical density logs to the evaluation of PVC‐cased moni

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00356.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractNon‐point source pollution of ground water systems has become a national concern in recent years. Researchers and regulatory agencies are investigating the source and processes of the contamination. Agricultural best management practices (BMPs) traditionally developed to reduce non‐point source pollution of surface water resources are being investigated for their impact on ground water quality. This study used the CREAMS model to simulate the long‐term effects of seven different BMPs on nitrate nitrogen (NO3‐N) loadings to a shallow, unconfined ground water system. Two representative watersheds, 5.8 and 8.9 hectares (14.3 and 22 acres) in area, in the Coastal Plain physiographic region of Maryland were selected for study. Soils in these watersheds belong to the Matapeake silt loam series and have moderate infiltration capacity. Results from this study indicated that BMPs used in conjunction with winter cover (barley) reduced NO3‐N leaching to the ground water system. It was also found that turfgrass reduced surface losses of water and nitrogen, but increased leaching losses of water and NO3‐N significantly. All of the BMPs simulated in this study resulted in leachate NO3‐N concentrations exceeding 10 ppm, the U.S. EPA health standard for public drinking water, indicating a need for alternate practices for reducing nit

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1991.tb00357.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY