1998 Progress Report: A Study of the Gas/Particle Partitioning of Chlorinated Dibenzodioxins (CDDs) and Chlorinated Dibenzofurans (CDFs) to Ambient and Model Aerosol MaterialsEPA Grant Number: R825376
Title: A Study of the Gas/Particle Partitioning of Chlorinated Dibenzodioxins (CDDs) and Chlorinated Dibenzofurans (CDFs) to Ambient and Model Aerosol Materials
Investigators: Pankow, James F.
Institution: Oregon Graduate Institute of Science & Technology
EPA Project Officer: Shapiro, Paul
Project Period: October 1, 1996 through September 30, 1999
Project Period Covered by this Report: October 1, 1997 through September 30, 1998
Project Amount: $466,448
RFA: Exploratory Research - Air Engineering (1996) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Land and Waste Management , Air , Engineering and Environmental Chemistry
Objective:Construct Linear Free Energy Relationships to predict the gas/particle partitioning behavior of the polychlorinated dibenzodioxins and dibenzofurans to ambient aerosols.
A two stage air sampler has been constructed and tested and is working successfully. During the testing of the apparatus much data concerning the gas/particle partitioning behavior of PAHs and PCDD/Fs has been obtained using this sampler in controlled field experiments (CFEs) conducted in Portland, Oregon.
Side by side sampling of the same ambient aerosol material was performed using conventional high volume air sampling and the CFE method. Conventional sampling was conducted throughout the night with changes of only 2 _C and 10% in the relative humidity. The plot of log Kp vs. log pL_ using data from the conventional experiments had a slope shallower than the value of -1. This observation cannot be due to a sampling artifact caused by T or RH variations. The plot of log Kp vs. log pL_ using data from the CFEs have slopes nearer to -1 and the values of Kp determined from both methods become more similar for the low vapor pressure compounds. This data suggests that for PAHs, slopes shallower than -1 may be due to the rate limited desorption of the PAHs from within combustion derived aerosols and the value of _om may be constant throughout the compound class.
From a modeling perspective it would be quite useful if Kp values
for SOCs could be predicted using a linear free energy relationship and only a
few easily measurable or previously available input parameters. To compensate
for differences in the organic matter content of UPM, values of Kp
can be normalized to easily measurable values of fom yielding
For a given class of compounds, in order for values of Kp,om to be constant for partitioning to UPM from different locations, the term _om MWom must remain constant. Should this be the case, values of Kp could be predicted at any urban site using the slope and intercept values of a plot of log Kp vs log pL_determined at one urban location, the value of aerosol fom at the location of interest, and the pL_for the compound and temperature of interest. Kp,om values of the PAHs measured using CFEs are compared to data published from other studies where sampling artifacts were also minimized. This data suggest that in the absence of sampling artifacts, values of the term _om MWom may be similar for the PAHs among all UPM and that Kp values may be conveniently predicted at other locations. Furthermore, there is hope that an analogous relationship may be true for the PCDD/Fs.