title: Quantitative passive soil vapor sampling for VOCs--Part 4: Flow-through cell.
abstract: This paper presents a controlled experiment comparing several quantitative passive samplers for monitoring concentrations of volatile organic compound (VOC) vapors in soil gas using a flow-through cell. This application is simpler than conventional active sampling using adsorptive tubes because the flow rate does not need to be precisely measured and controlled, which is advantageous because the permeability of subsurface materials affects the flow rate and the permeability of geologic materials is highly variable. Using passive samplers in a flow-through cell, the flow rate may not need to be known exactly, as long as it is sufficient to purge the cell in a reasonable time and minimize any negative bias attributable to the starvation effect. An experiment was performed in a 500 mL flow-through cell using a two-factor, one-half fraction fractional factorial test design with flow rates of 80, 670 and 930 mL min(-1) and sample durations of 10, 15 and 20 minutes for each of five different passive samplers (passive Automatic Thermal Desorption Tube, Radiello®, SKC Ultra, Waterloo Membrane Sampler™ and 3M™ OVM 3500). A Summa canister was collected coincident with each passive sampler and analyzed by EPA Method TO-15 to provide a baseline for comparison of the passive sampler concentrations. The passive sampler concentrations were within a factor of 2 of the Summa canister concentrations in 32 of 35 cases. Passive samples collected at the low flow rate and short duration showed low concentrations, which is likely attributable to insufficient purging of the cell after sampler placement.
authors.affiliation: Geosyntec Consultants, Inc., 130 Research Lane, #2, Guelph, Ontario N1G 5G3, Canada. tmcalary@geosyntec.com.
authors.forename: Todd
authors.initials: T
authors.lastname: McAlary
authors.forename: Hester
authors.initials: H
authors.lastname: Groenevelt
authors.forename: Suresh
authors.initials: S
authors.lastname: Seethapathy
authors.forename: Paolo
authors.initials: P
authors.lastname: Sacco
authors.forename: Derrick
authors.initials: D
authors.lastname: Crump
authors.forename: Michael
authors.initials: M
authors.lastname: Tuday
authors.forename: Brian
authors.initials: B
authors.lastname: Schumacher
authors.forename: Heidi
authors.initials: H
authors.lastname: Hayes
authors.forename: Paul
authors.initials: P
authors.lastname: Johnson
authors.forename: Louise
authors.initials: L
authors.lastname: Parker
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Górecki
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D012987:Soil / Q000737:chemistry*; D055549:Volatile Organic Compounds / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D012987:Soil; D055549:Volatile Organic Compounds