Field Calibration and PAS-SIM Model Evaluation of the XAD-Based Passive Air Sampler for Semi-Volatile Organic Compounds

The use of passive air samplers (PAS)for semi-volatile organiccompounds (SVOCs) continues to expand. To advance quantitative understandingof uptake kinetics, we calibrated the XAD-PAS, using a styrene-divinylbenzenesorbent, through a year-long side-by-side deployment with an activesampler. Twelve XAD-PASs, deployed in June 2020, were retrieved at4-week intervals, while gas phase SVOCs were quantified in 48 consecutiveweek-long active samples taken from June 2020 to May 2021. Consistentwith XAD's high uptake capacity, even relatively volatile SVOCs,such as hexachlorobutadiene, displayed linear uptake throughout theentire deployment. Sampling rates (SRs) range between 0.1 and 0.6m(3) day(-1) for 26 SVOCs, including brominatedflame retardants, organophosphate esters, and halogenated methoxylatedbenzenes. SRs are compared with experimental SRs reported previously.The ability of the existing mechanistic uptake model PAS-SIM to reproducethe observed uptake and SRs was evaluated. Agreement between simulatedand measured uptake curves was reasonable but varied with compoundvolatility and the assumed stagnant air layer boundary thickness.Even though PAS-SIM succeeds in predicting the SR range for the studiedSVOCs, it fails to capture the volatility dependence of the SR byunderestimating the length of the linear uptake period and by failingto consider the kinetics of sorption. Ayear-long calibration study confirms that the linear uptakeperiod of a passive air sampler using XAD-resin sorbent is longerthan estimated with a simulation model and much longer than thoseof samplers using polyurethane or polyethylene as sorbents.

Automated summary

The use of passive air samplers (PAS) for semi-volatile organic compounds (SVOCs) has been expanding. A year-long calibration study confirmed that the linear uptake period of a passive air sampler using XAD-resin sorbent is longer than estimated with a simulation model and much longer than those of samplers using polyurethane or polyethylene as sorbents. The sampling rates (SRs) for 26 SVOCs were determined, ranging from 0.1 to 0.6 m(3) day(-1) for SVOCs such as brominated flame retardants, organophosphate esters, and halogenated methoxylated benzenes.