Gas/solid partitioning of semivolatile organic compounds (SOCs) to air filters. 1. Partitioning of polychlorinated dibenzodioxins, polychlorinated dibenzofurans and polycyclic aromatic hydrocarbons to teflon membrane filters

Gas/particle distributions of semi-volatile organic compounds (SOCs) in the atmosphere are often measured using filter/sorbent samplers. Unfortunately, the adsorption of gaseous SOCs onto a filter can cause positive biases in the measured particle-phase concentrations, and negative biases in the measured gas-phase concentrations. In order to permit estimation of the magnitudes of these errors when Teflon membrane filters (TMFs) are used, surface-area-normalized gas/Teflon partition coefficient (Kp,s) values were measured for a range of polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polycyclic aromatic hydrocarbons (PAHs). Sorption isotherms were linear over three orders of magnitude. A 10° change in temperature (T) caused the Kp,s values to decrease by factors of 2.4–3.4. Changes in relative humidity (RH) between 21 and 52% did not affect the measured Kp,s values. The dependence of the partitioning on the sub-cooled liquid vapor pressures of the subject compounds was investigated. Within each of the three individual compound classes, plots of logKp,s vs. log pLo were linear with slopes of approximately −1. The pooled data for the three compound classes yielded a single logKp,s vs. log pLo plot for 25°C that was correlated nearly as well (r2=0.96) as the plots for the individual compound classes (r2≈0.95). Since backup TMFs used in filter/sorbent sampling in urban areas yielded the same Kp,s values as did clean TMFs, assessment of the magnitude of the gas adsorption artifact for TMFs can be carried out using Kp,s values obtained with clean and/or ambient backup TMFs.