Transcript Slide 1
Air Toxics LTD Laboratory Services Since 1989 Field Evaluation of Diffusive Samplers for Indoor Air VOC Measurements AIHce 2011 Heidi Hayes, Technical Director Robert Mitzel, Vice-President Business Development 1201 Outline • • • • • • Introduction Study Objectives Sampler Selection Field Sampling Results Conclusions Conventional Air Sampling Summa Canisters • Possible equipment failure • Requires experienced field sampler • Short duration (~24 hours) • Expensive to ship Pumped Sorbent Tubes • Requires experienced field sampler • Short duration (~8 hours) • Sorbent type and sample volume selection is critical Passive Sampling Practical Advantages • Reliable deployment with little training required • Unobtrusive • Inexpensive to ship Technical Advantages • Capable of generating trace level RLs • Long-term time-integrated measurements More representative indoor air concentrations and increased sensitivity are advantageous to health risk assessments. Passive Sampling Concepts Measured in lab Analytical Result X (µg) 1000 mL 1L X 1000 L m3 Concentration (µg/m3) Uptake Rate (mL/min) Available in literature Dependent on Sampler Geometry X Sampling duration (min) Recorded in the field Project Objectives • Sample integration of 1 to 7 days • Measurement of a wide VOC suite – Petroleum and chlorinated compounds • Reporting limits comparable to TO-15 SIM (~0.1 µg/m3) • Measured concentrations correlate with TO-15 Passive Samplers Sampler Geometries Analytical Sensitivity Tube Membrane Badge Radial WMS®Charcoal SKC 575 3M OVM Radiello®130 Sorbent Solvent Thermal Desorption ATD Lowest WMS®TD SKC ULTRA Radiello®145 Sampling Rate Highest Passive Samplers Sampler Geometries Tube Membrane Badge Radial Sorbent Solvent Thermal Desorption Radiello®130 SKC ULTRA Radiello®145 Field Sampling – Case 1 • Indoor air samples collected • Duration 3, 4, and/or 7 days • Concurrent deployment – Radiello 130 – Charcoal – Radiello 145 – TD Sorbent – ULTRA III – TD sorbent Results Concentration (µg/m3) Compound Trichloroethene Tetrachloroethene Sample Indoor 1 Indoor 2 Indoor 3 Indoor 4 Indoor 4 ULTRA III 0.46 0.86 1.0 7.4 2.9 RadielloCharcoal RadielloTD 0.33 0.84 0.70 9.4 3.0 0.29 0.42 0.54 6.8 3.7 %RSD 25% 35% 31% 17% 14% Good comparability was observed when detections on each sampler were sufficiently above their respective reporting limits. Results •ULTRA III = 5-20 times greater sensitivity than the RAD-Charcoal. •ULTRA III had validated sampling rates for chlorinated breakdown products whereas RAD-TD required estimated rates. •Diffusive adsorption on the RAD-TD sorbent did not behave as predicted for these light VOCs (chloroform, 1,1-DCE) resulting in low bias. Stronger TD sorbent is required for these VOCs. Results • One indoor air location was severely impacted with chlorinated solvents (100 to 10,000 µg/m3) • Sampling duration was 3 days. • Both Radiello-TD and ULTRA III exceeded capacity & TD-GC/MS. • Radiello-Charcoal had a higher capacity, and solvent extraction allowed for easy dilutions. Field Sampling – Case 2 • Indoor air samples collected – 13 sites – Concurrent TO-15 cans & ULTRA III – Chlorinated solvents,petroleum products – 1 to 3 day duration Results Strong correlation between ULTRA III and TO-15 concentrations across 3 orders of magnitude and at concentrations <0.1 µg/m3 Conclusions • Each passive sampler evaluated provided quantitative VOC indoor air measurements for TCE and PCE over a period of up to 7 days. • The larger surface area of charcoal provided an advantage over TD-sorbents when sampling high concentrations over multiple days. Conclusions • ULTRA III-TD and Radiello-TD provide greater sensitivity than the RadielloCharcoal over the 1-7 day period. • ULTRA III-TD provides a wider range of VOCs than Radiello-TD. • ULTRA III has a built-in blank correction allowing for improved accuracy at trace levels.