Estimation of Volatile Organic Compound Concentrations in the Vadose Zone
Estimation of Volatile Organic Compound Concentrations in the Vadose Zone

Author: RK. Sextro

Publisher:

Published: 1996

Total Pages: 16

ISBN-13:

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Obtaining defensible and conservative estimates of the nature, extent and concentration of volatile organic compounds (VOCs) in the vadose zone is extremely important when formulating the conceptual model of the site, when performing risk assessments, for estimating contaminant mass, for assessing remedial alternatives, for selecting target areas for cleanup, and/or for making no further action/investigation decisions. Studies have shown that soil gas analytical results provide both a more complete indication of the VOCs present and a higher estimate of their respective concentrations in the vadose zone than the analysis of soil samples alone. For the past several years deep downhole (to 30+ meters) soil gas sampling and analysis has been performed by various consultants during remedial investigations (RIs) and remedial actions (RAs) of the vadose zone at McClellan Air Force Base. A number of these soil gas results have been confirmed by the concurrent collection and analysis (for VOCs) of soil samples (preserved by either refrigeration to 4 degrees centigrade or refrigeration combined with methanol preservation). The use of this VOC sampling and analysis strategy has resulted in the optimization of VOC sampling and analysis procedures, in a better understanding of the relationship between the concentration of VOCs in soil gas and in the soil, and in a more accurate and comprehensive conceptual model for VOC contamination in the vadose zone. The paper will present the methodologies used by the various consultants for sample collection, preservation, and in the analysis of soil gas and soil samples, present the results of a focused QC study on soil gas sampling and analysis, and discuss the correlation between the soil gas and soil matrix analytical results. The current and future strategies for the sampling, analysis, and estimation of VOCs in the vadose zone during RIs and RAs will also be presented.

Soil Samplers
Soil Samplers

Author:

Publisher:

Published: 2009

Total Pages:

ISBN-13:

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Soil sampling techniques for volatile organic analysis must be designed to minimize loss of volatile organic compounds (VOCs) from the soil that is being sampled. Preventing VOC loss from soil cores that are collected from the subsurface and brought to the surface for subsampling is often difficult. Subsurface bulk sample retrieval systems are designed to obtain intact cylindrical cores of soil ranging anywhere from one to four inches in diameter, and one to several feet in length. The current technique that is used to subsample these soil cores for VOC analysis is to expose a horizontal section of the soil core to the atmosphere; screen the exposed soil using a photoionization detector (PID) or other appropriate device to locate contamination in the soil core; and use a hand-operated coring tool to collect samples from the exposed soil for analysis. Because the soil core can be exposed to the atmosphere for a considerable length of time during screening and sample collection, the current sub-sampling technique provides opportunity for VOCs to be lost from the soil. This report describes three alternative techniques from the current technique for screening and collecting soil samples from subsurface soil cores for VOC analysis and field testing that has been done to evaluate the techniques. Based on the results of the field testing, ASTM D4547, Standard Guide for Sampling Waste and Soils for Volatile Organic Compounds, was revised to include information about the new techniques.

Validation of a New Soil VOC Sampler
Validation of a New Soil VOC Sampler

Author: John F. Schabron

Publisher:

Published: 2003

Total Pages:

ISBN-13:

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Soil sampling and storage practices for volatile organic analysis must be designed to minimize loss of volatile organic compounds (VOCs) from samples. The En Core{reg_sign} sampler is designed to collect and store soil samples in a manner that minimizes loss of contaminants due to volatilization and/or biodegradation. An American Society for Testing and Materials (ASTM) standard practice, D 6418, Standard Practice for Using the Disposable En Core Sampler for Sampling and Storing Soil for Volatile Organic Analysis, describes use of the En Core sampler to collect and store a soil sample of approximately 5 grams or 25 grams for volatile organic analysis. To support the ASTM practice, a study was performed to estimate the precision of the performance of the 5-gram and 25-gram En Core samplers to store soil samples spiked with low concentrations of VOCs. This report discusses revision of ASTM Practice D 6418 to include information on the precision of the En Core devices and to reference an ASTM research report on the precision study. This report also discusses revision of the ASTM practice to list storage at -12 {+-} 2 C for up to 14 days and at 4 {+-} 2 C for up to 48 hours followed by storage at -12 {+-} 2C for up to 5 days as acceptable conditions for samples stored in the En Core devices. Data supporting use of these storage conditions are given in an appendix to the practice and are presented in the research report referenced for the precision study. Prior to this revision, storage in the device was specified at 4 {+-} 2 C for up to 48 hours. The En Core sampler is designed to collect soil samples for VOC analysis at the soil surface. To date, a sampling tool for collecting and storing subsurface soil samples for VOC analysis does not exist. Development of a subsurface VOC sampling/storage device was initiated in 1999. This device, which is called the Accu Core sampler, is designed so that a soil sample can be collected below the surface using a penetrometer and transported to the laboratory for analysis in the same container. During the past year, prototype devices have been tested for their performance in storing soil samples containing low concentrations of VOCs. The Accu Core sampler testing is also described in this report.

Validation of a New Soil VOC Sampler
Validation of a New Soil VOC Sampler

Author:

Publisher:

Published: 2002

Total Pages:

ISBN-13:

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Soil sampling and storage practices for volatile organic analysis must be designed to minimize loss of volatile organic compounds (VOCs) from samples. The En Core{reg_sign} sampler is designed to collect and store soil samples in a manner that minimizes loss of contaminants due to volatilization and/or biodegradation. An American Society for Testing and Materials (ASTM) standard practice, D 6418, Standard Practice for Using the Disposable En Core Sampler for Sampling and Storing Soil for Volatile Organic Analysis, describes use of the En Core sampler to collect and store a soil sample of approximately 5 grams or 25 grams for volatile organic analysis. To support the ASTM practice, four studies have been performed to evaluate the performance of the En Core sampler for storage of soil samples spiked with VOCs. The first study was conducted to evaluate the performance of the device to store soil samples spiked with VOCs at high-level concentrations of approximately 2,500 [mu]g/Kg under various conditions. This analyte concentration in the soil was selected to limit the influence of the analytical method on the data. A second study was conducted to answer questions on the performance of the En Core sampler for storage of soil samples containing low-level (

Analysis of Volatile Organic Compounds (VOCs) in Soil Via Passive Sampling
Analysis of Volatile Organic Compounds (VOCs) in Soil Via Passive Sampling

Author:

Publisher:

Published: 2015

Total Pages: 58

ISBN-13:

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Passive sampling has been used as a qualitative and semi-quantitative method in detecting volatile organic compound (VOCs) concentrations in soil vapors or water. Passive sampling for soil vapor takes an absorptive material and places it underground for a period of time to allow the VOCs to diffuse into the absorptive materials. In this report, I use low density polyethylene (PE) as the absorptive material and determine two key parameters for passive sampling: the PE-water partition coefficient (Kpew) and diffusion coefficient in PE (Dpe). These two parameters help passive sampling to transition from a qualitative method to a quantitative method. The report describes the steps used to carry out the experiments, gives the results for several specific VOCs, and makes an attempt to draw more general conclusions on how to estimate these two parameters according to some other well-known properties.