Further developments in the use of semipermeable membrane devices as passive air samplers: application to PCBs

There are several incentives for developing passive air sampling techniques for persistent organic pollutants (POPs). This paper reports on studies to further calibrate and optimize semipermeable membrane devices (SPMDs) for use as "integrated" air samplers of gas-phase POPs. These samplers are deployed over weeks/months/years. Polychlorinated biphenyls (PCBs) were used as the test compounds in this study, with three specific objectives: (i) to determine whether ambient wind speed limits the rate of uptake during typical deployment conditions; (ii) to monitor uptake and SPMD-air equilibrium for a range of compounds; and (iii) to assess the application of performance reference compounds (PRCs) in air sampling, to "correct" for site-specific differences in uptake rates. When deployed in Stevensons screens under ambient conditions, wind speed did not significantly affect uptake rates. Rather, differences in summer/winter uptake rates reported previously, using the same deployment devices as here, are due to temperature affecting compound permeability through the membrane. Results from the use of PRCs indicate that SPMDs should be spiked prior to exposure with a range of compounds that are not present in the atmosphere, so that uptake rates can be estimated from depuration rates during a particular deployment. Short-term deployments (e.g. days; few weeks) would need to use compound(s) with a low octanol:air partition coefficient (K(OA)) (e.g. 13C12 labeled PCB-28); long-term deployments (of many months to years) would need to use intermediate K(OA) compounds (e.g. 13C12 PCB-101; 13C12 PCB-153).