Citation:

Schumacher, B A. AND J. H. Zimmerman. COMPOSITE SAMPLING FOR SOIL VOC ANALYSIS. Presented at National Environmental Monitoring Conference, Washington, DC, July 19-22, 2004.

Impact/Purpose:

The overall objective of this task is to provide the Agency with improved state-of-the-science guidance, strategies, and techniques to more accurately and effectively collect environmental samples. Under this umbrella objective, research is being conducted to: (a) reduce/minimize the loss of VOCs during sample collection, handling, and preservation, (b) collect undisturbed surface sediments so that the effects of recent depositional events (e.g., flooding or dredging) can clearly be delineated as to their influence on the contamination concentrations present downstream (or where the sediments are deposited), and (c) to determine an effective method to effectively and efficiently separate asbestos in soils from the rest of the soil matrix while maintaining the integrity (i.e, no fiber size reduction) of the asbestos fibers.

Description:

Data published by numerous researchers over the last decade demonstrate that there is a high degree of spatial variability in the measurement of volatile organic compounds (VOCs) in soil at contaminated waste sites. This phenomenon is confounded by the use of a small sample aliquot (5 g) in the standard low-level, purge-and-trap sample extraction method (i.e., SW-846 Method 5035), which decreases the representativeness of the sample. In order to optimize sample representativeness, the number of samples collected at the site is generally increased; however, this greatly increases project costs. Compositing soil samples has been suggested as a cost-effective alternative means to obtain data which are representative of the overall conditions at a site. This study investigated this approach and it's impact on representativeness.

To explore the feasibility of composite sampling for soil VOC analysis, core samples were collected and cut into sections at 20, 30, 40, 50, 60, 70 and 80 cm below the ground surface. After each cut, approximately 5 g of soil was removed from the newly exposed surface (top end of the cut) using a truncated syringe and placed in a preweighed 40-mL septum-sealed vial containing 5 mL of methanol. A second 5 g sample was removed from each core at the 20, 40, 60, and 80 cm intervals and combined in a preweighed 40-mL septum-sealed vial containing 20 mL of methanol. Samples were analyzed following SW-846 methods 5035/8260.

Record Details: