Equilibration times, compound selectivity, and stability of diffusion samplers for collection of ground-water VOC concentrations

Determination of VOCs in groundwater at an industrial contamination site using a homemade low-density polyethylene passive diffusion sampler

“…However, a previous study (Vroblesky and Campbell, 2001) showed that equilibration time for PDB sampling under cold conditions has no significant difference compared to warm conditions, and the differences in equilibration time due to temperature effects seem to be small for many VOCs after 7 days and for most tested compounds by 14 days. In this study, we use a sampling time of at least 14 days without further studying the effect of temperature.…”

“…Conventional sampling procedures like power-requiring purge-and-sample methods suffer from an unwanted distortion of the contaminant concentration owing to a change in the hydraulic flow field, and mass loss and therefore lower contaminant concentrations in the water samples due to the volatilization of analytes during the sampling processes (Martin et al, 2003;Mcleish et al, 2007). Therefore, passive diffusion bag (PDB) samplers prepared by filling deionized water in heat-sealed, lowdensity polyethylene (LDPE) lay-flat tubes were developed for sampling VOCs in groundwater (Vroblesky and Hyde, 1997;Vroblesky and Campbell, 2001). By deploying PDB in ground water, the VOCs of interest diffuse across the LDPE membrane according to the local concentration * Corresponding author: E-mail: jfliu@rcees.ac.cn gradient until the VOC concentration in the water phase of the sampler is equilibrated with the concentration outside the sampler.…”

Use of Passive-Diffusion Bag Samplers to Profile Low-Level Trichloroethene Concentrations in Ground-Water Extraction Wells

“…As the aqueous environment becomes colder, PDB samplers require a longer time to equilibrate. Vroblesky and Campbell (2001) showed through laboratory experimentation that after a 7-day period the concentration of TCE in water from a PDB sampler was within 10 percent of the ambient TCE concentration of the test solution at 8uC. Ambient ground-water temperatures ranged from 5.6uC to 9.3uC (Table 1) at the site, indicating the 7-day equilibration time was probably the absolute minimum that should have been allowed at these temperatures.…”

Demonstration/Validation of the Snap Sampler Passive Ground Water Sampling Device

“…Both of these analytes are highly soluble in water. Vroblesky and Campbell (2001) found that the PDB sampler (with a PE membrane) should not be used for several highly soluble analytes, specifically acetone, MTBE, and methyl isobutyl ketone.…”