The potential role of mechanistic models for interpreting passive air sampling data for semi-volatile organic chemicals.

ARMITAGE, JAMES; SILVA BARNI, MARÍA FLORENCIA; WANIA, FRANK

Orlando

Congreso; 7th SETAC World Congress SETAC North America 37th Annual Meeting; 2016

Passive air sampling is now well-established in the contaminant monitoring community and there are a variety of passive air sampler (PAS) designs described in the literature. Although PAS can differ with respect to sampler material (e.g., polyurethane foam, XAD resin, activated carbon felt, polyethylene, polydimethylsiloxane) and housing (e.g., none, ´flying saucer´, cylindrical), the uptake and depuration kinetics are typically assumed to conform to the same theoretical model (Whitman Two-Film Theory). However, as the old aphorism goes, "All models are wrong but some are useful". Potential errors inherent to any modeling approach relate not only to the validity of the assumptions made (e.g., air-side resistance dominates exchange) but also the reliability of required input parameters (e.g., sampler air partition coefficients and their temperature-dependence). The main objective of this presentation is to examine the underlying assumptions adopted in the PAS community with respect to uptake and depuration kinetics of semi-volatile organic chemicals (SVOCs) using the modeling tool developed within our research group (PAS-SIM). Insights from previous model evaluations using concurrent passive XAD-2 and active air sampling data are highlighted along with simulations of depuration compounds under different environmental conditions (e.g., temperature profiles and windspeeds). These model applications are used to discuss the advantages and disadvantages of applying mathematical tools to convert the mass of chemical accumulated on a PAS during deployment to air concentrations and also to identify key data gaps and research needs in this area.