ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1985.tb00928.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractFour questions relative to suction lysimeter performance have been raised by operators of land treatment systems. These questions deal with plugging of the porous segments of the lysimeters, soil suction operational ranges, adsorption onto and screening by the materials comprising the various lysimeter parts, and loss of volatile organics under negative pressures. This article first describes the physical operation of a lysimeter, the characteristics of the lysimeters tested (high‐ and low‐flow lysimeters with porous ceramic cups and lysimeters with porous PTFE (polytetrafluo‐roethylene) cups, and procedures followed in preparing them for testing. The results of experiments dealing with the first two questions plugging and operational ranges are then discussed. It was found that the intake rate of suction lysimeters placed in the vadose zone, in most types of soils, will initially drop off rapidly, but will stabilize after about 15 liters of moisture have been drawn through the porous cups. Packing a crystalline silica flour slurry around the cups of PTFE lysimeters negates most of the plugging associated with finer particles in soils. The effective operating range of ceramic lysimeters is between 0 and 60 centibars of suction independent of the use of silica flour. The operating range of PTFE lysimeters without silica flour is extremely narrow, but with the use of silica flour is extended to about 7 centibars of suction. The testing program indicates that all lysimeters should be checked for leaks using pressure techniques before field installation and that lysimeters have “dead” spaces, or reservoirs of from 34 to 80 mL of moisture that cannot be extracted from the cups, which must be taken into account when determining moisture collection rates. Information gathered in the test program is planned for inclusion in an EPA guidance document entitled “Unsaturated Zone Monitoring at Hazardous Waste Land Treat

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1985.tb00929.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1985.tb00930.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1985.tb00931.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1985.tb00932.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractIncreasingly, regulations by federal, state and local agencies are being developed that require the installation of vadose zone monitoring systems for hazardous chemical facilities in addition to, or in lieu of, conventional ground water monitoring wells. Compared to a ground water monitoring approach, vadose zone monitoring systems may permit earlier detection of chemical leakage and less costly cleanup of contamination. The effective use of vadose zone monitoring systems in detecting contamination depends on many factors. Without proper consideration of these factors, a vadose zone monitoring system may not give as high a level of reliability as a ground water monitoring system.Major factors to consider in installing a vadose zone monitoring system are: type of instrument to use, number of instruments, depth and location of instruments, and frequency of monitoring. Means to evaluate these factors in a comprehensive fashion have been lacking. Based on recent experience in installing and operating vadose zone monitoring systems, criteria and methods useful in resolving the preceding factors have been developed. Types of instruments can be classified as either direct (lysimeter, vapor probe) or indirect (tensiometer, conductivity probe). A combination of the two is needed for reliability. The depth, location and number of instruments depend on the geometry of the facility, the number and size of likely contaminant leakage points in engineered barriers, properties of the material being monitored, the effective radius of monitoring for each instrument, vadose zone properties, and types of remedial actions that are available. The freqency of monitoring largely depends on the rate of movement of the contaminant. Evaluating the preceding factors requires some level of modeling and preliminary field testing.

ISSN:1069-3629    

DOI:10.1111/j.1745-6592.1985.tb00933.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY