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Evaluation of an Automated Air Sampling System: LESS™
Poster Presentation
Prepared by K. Hunt
Signature Science, LLC, 8329 N. Mopac Expressway, Austin, Texas, 78759
Contact Information: KyleHunt@signaturescience.com; 512-583-2463
ABSTRACT
Manually collecting SUMMA® canisters or sorbent tubes during vapor intrusion (VI) monitoring typically employs a single device to collect single samples with limited duplicates or distributive pairs. Such labor and equipment intensive sampling provides limits spatial and temporal data while also limiting the capability to record flow rates and sample durations real-time. Signature Science developed LESS™, a fully programmable, constant flow air sampler with an integrated micro-controller and data acquisition system that can collect up to 28 discrete air samples including simultaneous duplicates using a common manifold. Flow rates range from 5-750 mL/min.
To validate this new collection system against traditional technologies, comparison thermal desorption tubes were collected using LESS™ and a manual air sampling pump in a controlled laboratory test against 109 compounds (nC2 – nC12). Individual, duplicate, or distributive volume pair samples were collected to determine recoveries, false-positives, and false-negatives at safe sampling volumes.
Fifty-four (54) of 109 targets were quantified by a third-party NELAC accredited laboratory using EPA’s Method TO-17. Remaining analytes were reported as TICs yielding total detections of 103 analytes: the exception being the most volatile hydrocarbons (acetylene, ethylene, ethane, and propane), 1-butanol, and methanol (spiking solvent). False-negatives were observed for 3 compounds at the 1 ppb-v concentration: 2-hexanone (31%), naphthalene (6%), and acetone (3%). Blank samples reported false-positives for acetone, hexachlorobutadiene, 1,2,3- and 1,2,4-trichlorobenzene, with levels at or near the analytical reporting limit.
At all test concentrations and collection volumes, LESS™ recovered the target analytes at similar precision and accuracy as the traditional manual pump. Recoveries for both were between 80% and 180% with correlations at or above 0.90.
In the spring of 2012, LESS™ was employed in a VI study at Hill AFB in Utah. The study was a long-term characterization of VI over diurnal sampling events across a year to estimate the changes in contamination levels over time. Typically, sampling methods for VI collect infrequent samples using SUMMA® canisters over a 24-hour time period. This approach produces limited sample data that may not accurately assess VI occurrence or the magnitude. Using a LESS™ manifold based sampler, continuous collection (at 4-hour intervals) over a five-week period showed the utility of dense sampling and the results demonstrated periods of vapors associated with VI in February and March, with less frequency episodes toward the end of sampling period.
For each collection event described above, this poster will present the data and summarize the findings.
(Related Session: Air Methods/Monitoring)
Poster Presentation
Prepared by K. Hunt
Signature Science, LLC, 8329 N. Mopac Expressway, Austin, Texas, 78759
Contact Information: KyleHunt@signaturescience.com; 512-583-2463
ABSTRACT
Manually collecting SUMMA® canisters or sorbent tubes during vapor intrusion (VI) monitoring typically employs a single device to collect single samples with limited duplicates or distributive pairs. Such labor and equipment intensive sampling provides limits spatial and temporal data while also limiting the capability to record flow rates and sample durations real-time. Signature Science developed LESS™, a fully programmable, constant flow air sampler with an integrated micro-controller and data acquisition system that can collect up to 28 discrete air samples including simultaneous duplicates using a common manifold. Flow rates range from 5-750 mL/min.
To validate this new collection system against traditional technologies, comparison thermal desorption tubes were collected using LESS™ and a manual air sampling pump in a controlled laboratory test against 109 compounds (nC2 – nC12). Individual, duplicate, or distributive volume pair samples were collected to determine recoveries, false-positives, and false-negatives at safe sampling volumes.
Fifty-four (54) of 109 targets were quantified by a third-party NELAC accredited laboratory using EPA’s Method TO-17. Remaining analytes were reported as TICs yielding total detections of 103 analytes: the exception being the most volatile hydrocarbons (acetylene, ethylene, ethane, and propane), 1-butanol, and methanol (spiking solvent). False-negatives were observed for 3 compounds at the 1 ppb-v concentration: 2-hexanone (31%), naphthalene (6%), and acetone (3%). Blank samples reported false-positives for acetone, hexachlorobutadiene, 1,2,3- and 1,2,4-trichlorobenzene, with levels at or near the analytical reporting limit.
At all test concentrations and collection volumes, LESS™ recovered the target analytes at similar precision and accuracy as the traditional manual pump. Recoveries for both were between 80% and 180% with correlations at or above 0.90.
In the spring of 2012, LESS™ was employed in a VI study at Hill AFB in Utah. The study was a long-term characterization of VI over diurnal sampling events across a year to estimate the changes in contamination levels over time. Typically, sampling methods for VI collect infrequent samples using SUMMA® canisters over a 24-hour time period. This approach produces limited sample data that may not accurately assess VI occurrence or the magnitude. Using a LESS™ manifold based sampler, continuous collection (at 4-hour intervals) over a five-week period showed the utility of dense sampling and the results demonstrated periods of vapors associated with VI in February and March, with less frequency episodes toward the end of sampling period.
For each collection event described above, this poster will present the data and summarize the findings.
(Related Session: Air Methods/Monitoring)