Date

April 2000

Document Type

Dissertation

Degree Name

Ph.D.

Department

Dept. of Environmental Science and Engineering

Institution

Oregon Graduate Institute of Science & Technology

Abstract

Atmospheric transport has been considered to be the dominant process responsible for the movement of polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polycyclic aromatic hydrocarbons (PAHs) from combustion sources to remote receptors such as lake sediments, soils, and grasses. PCDD/Fs and PAHs are considered semi-volatile organic compounds (SOCs) and are distributed between the gas (G) and particle (P) -phases in the atmosphere. A G/P partition coefficient (Kp) is defined as the ratio of the concentration of compound associated with the P-phase (cp) to the concentration of the compound in the gas phase (cg). The cg and cp of a given SOC are obtained from field measurements. Sampling artifacts can bias these values and preclude a mechanistic level understanding of the G/P partitioning process. Controlled field experiments (CFEs) represent a new approach, which minimizes sampling artifacts. Results are presented from field trials of CFEs conducted in Beaverton, OR Denver, CO and Hills, IA. The adsorptive affinity of two types of filters for gaseous PCDD/Fs and PAHs was compared and a model developed to predict the magnitude of the influence of gas adsorption artifacts on measurements of cg, cp and Kp. The vapor pressures of 13 PCDD/Fs and 6 PAHs were measured and several vapor pressure prediction techniques were evaluated using the new vapor pressure data. Parameters are given for calculating the [sub-cooled liquid vapor pressure of a compound (torr)] value of each of the 210 PCDD/F congeners as function of temperature. Kp values were normalized by the weight fraction of P-phase organic carbon (ƒ[subscript oc],) and organic matter phase (ƒ[subscript om]). There was less variation in the K[subscript p,oc] and K[subscript p,om] values of compounds with similar [sub-cooled liquid vapor pressure of a compound (torr)] values among locations than for Kp values. Among the three field locations and three studies from the literature, the Kp values of PAHs with similar[sub-cooled liquid vapor pressure of a compound (torr)] values varied by over 2.5 orders of magnitude; the K[subscript p,om] and K[subscript p,oc], values varied by one order of magnitude. Variation in the K[subscript p,om] values of a given compound among locations may be due to error in the conversion factor relating to f[subscript oc] to f[subscript om] and/or differences in the chemical composition of particulate organic matter phases among locations and/or sources of particles.

Identifier

doi:10.6083/M4HM56DF

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