Passive Sampling Demonstration/Validation for Vapor Intrusion Assessments
Oral Presentation
Prepared by T. McAlary, H. Groenevelt
Geosyntec Consultants, Inc., 130 Research Lane, Suite 2, Guelph, Ontario, N1G5G3, Canada
Contact Information: tmcalary@geosyntec.com; 519-515-0861
ABSTRACT
A five-year study was conducted to demonstrate and validate passive samplers for monitoring subsurface vapor intrusion to indoor air with funding by the U.S. Department of Defense and the Navy. The passive samplers tested included: 1) SKC Ultra II, 2) Radiello®, 3) Waterloo Membrane Sampler (WMS), 4) Automated Thermal Desorption (ATD) tubes, and 5) 3M OVM 3500. Accuracy and precision were measured relative to active sampling methods (U.S. EPA Methods TO-15 and TO-17). Laboratory testing was conducted under controlled conditions for 10 VOCs, including chlorinated compounds and petroleum hydrocarbons, at controlled temperatures, humidities, face velocities, concentrations and sample durations. The program also included field testing of indoor air, outdoor air, sub-slab vapor and deeper soil vapor at several DOD facilities with uptake rates ranging from about 0.05 to almost 100 mL/min and analysis by both thermal desorption and solvent extraction with durations ranging from 10 min to 12 days. Mathematical modeling was performed to provide theoretical insight into the potential behavior of passive samplers in the subsurface. The results showed passive samplers have precision comparable to active samples for a given set of conditions, ease of use was generally comparable or better, cost was comparable or better (improving with larger numbers of samples). Accuracy met the success criterion in most cases, and exceptions were attributable to one or more of five possible causes: a) poor retention of the analytes on the sampler; b) poor recovery of the analytes from the sorbent; c) starvation effects, d) uncertainty in uptake rate for the specific combination of sampler/compound/conditions, or e) blank contamination. These biases can be prevented in most cases through careful selection of the sampler, sorbent and exposure duration for specific target analytes. This research also demonstrated for the first time the reliable use of passive samplers for quantifying soil vapor concentrations.
Oral Presentation
Prepared by T. McAlary, H. Groenevelt
Geosyntec Consultants, Inc., 130 Research Lane, Suite 2, Guelph, Ontario, N1G5G3, Canada
Contact Information: tmcalary@geosyntec.com; 519-515-0861
ABSTRACT
A five-year study was conducted to demonstrate and validate passive samplers for monitoring subsurface vapor intrusion to indoor air with funding by the U.S. Department of Defense and the Navy. The passive samplers tested included: 1) SKC Ultra II, 2) Radiello®, 3) Waterloo Membrane Sampler (WMS), 4) Automated Thermal Desorption (ATD) tubes, and 5) 3M OVM 3500. Accuracy and precision were measured relative to active sampling methods (U.S. EPA Methods TO-15 and TO-17). Laboratory testing was conducted under controlled conditions for 10 VOCs, including chlorinated compounds and petroleum hydrocarbons, at controlled temperatures, humidities, face velocities, concentrations and sample durations. The program also included field testing of indoor air, outdoor air, sub-slab vapor and deeper soil vapor at several DOD facilities with uptake rates ranging from about 0.05 to almost 100 mL/min and analysis by both thermal desorption and solvent extraction with durations ranging from 10 min to 12 days. Mathematical modeling was performed to provide theoretical insight into the potential behavior of passive samplers in the subsurface. The results showed passive samplers have precision comparable to active samples for a given set of conditions, ease of use was generally comparable or better, cost was comparable or better (improving with larger numbers of samples). Accuracy met the success criterion in most cases, and exceptions were attributable to one or more of five possible causes: a) poor retention of the analytes on the sampler; b) poor recovery of the analytes from the sorbent; c) starvation effects, d) uncertainty in uptake rate for the specific combination of sampler/compound/conditions, or e) blank contamination. These biases can be prevented in most cases through careful selection of the sampler, sorbent and exposure duration for specific target analytes. This research also demonstrated for the first time the reliable use of passive samplers for quantifying soil vapor concentrations.
