Simulating and Explaining Passive Air Sampling Rates for Semivolatile Compounds on Polyurethane Foam Passive Samplers

Passive air samplers (PAS) including polyurethane foam (PUF) are widely deployed as an inexpensive and practical way to sample semivolatile pollutants. However, concentration estimates from PAS rely on constant empirical mass transfer rates, which add unquantified uncertainties to concentrations. Here we present a method for modeling hourly sampling rates for semivolatile compounds from hourly meteorology using first-principle chemistry, physics, and fluid dynamics, calibrated from depuration experiments. This approach quantifies and explains observed effects of meteorology on variability in compound-specific sampling rates and analyte concentrations, simulates nonlinear PUF uptake, and recovers synthetic hourly concentrations at a reference temperature. Sampling rates are evaluated for polychlorinated biphenyl congeners at a network of Harner model samplers in Chicago, IL, during 2008, finding simulated average sampling rates within analytical uncertainty of those determined from loss of depuration compounds and confirming quasilinear uptake. Results indicate hourly, daily, and interannual variability in sampling rates, sensitivity to temporal resolution in meteorology, and predictable volatility-based relationships between congeners. We quantify the importance of each simulated process to sampling rates and mass transfer and assess uncertainty contributed by advection, molecular diffusion, volatilization, and flow regime within the PAS, finding that PAS chamber temperature contributes the greatest variability to total process uncertainty (7.3%)

Variations of Flame Retardant, Polycyclic Aromatic Hydrocarbon, and Pesticide Concentrations in Chicago’s Atmosphere Measured using Passive Sampling

Atmospheric concentrations of flame retardants, polycyclic aromatic hydrocarbons, and pesticides were measured using passive air samplers equipped with polyurethane foam disks to find spatial information in and around Chicago, Illinois. Samplers were deployed around the greater Chicago area for intervals of 6 weeks from 2012 to 2013 (inclusive). Volumes were calculated using passive sampling theory and were based on meteorology and the compounds’ octanol–air partition coefficients. Geometric mean concentrations of total polybrominated diphenyl ethers ranged from 11 to 150 pg/m³, and tributyl phosphate, <i>tris</i>(2-chloroethyl)­phosphate, <i>tris</i>(1-chloro-2-propyl)­phosphate, and triphenyl phosphate concentrations were in the ranges of 54–290, 32–340, 130–580, and 170–580 pg/m³, respectively. The summed concentrations of 16 PAHs ranged from 8700 to 52 000 pg/m³ over the sampling area, and DDT, chlordane, and endosulfan concentrations were in the ranges of 2.7–9.9, 8.2–66, and 16–85 pg/m³, respectively. Sampling sites were split into two groups depending on their distances from the Illinois Institute of Technology campus in Chicago. With a few exceptions, the concentrations of most compound groups in the city’s center were the same or slightly higher than those measured >45 km away. The data also showed that the concentrations measured with a passive atmospheric sampling system are in good agreement with those measured with an active, high-volume, sampling system. Given that the sampling times are different (passive, 43 days; active, 1 day), and that both of these measured concentrations cover about 5 orders of magnitude, the agreement between these passive and active sampling methods is excellent