Atmospheric transport and deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are toxic compounds which are dispersed through the environment by atmospheric transport and deposition. It has been previously shown that there is a varying mixture of these compounds produced by combustion (the source of these compounds). Therefore, the goal of the project was to study PCDD/F in ambient air and rain samples (the transport media linking source to sink) in an effort to enhance the understanding of the physical/chemical parameters controlling the transformation which take place during atmospheric transport and deposition. Analytical methods included high-volume air sampling, wet-only rain sampling, column chromatographic cleanup, and an electron capture, negative ionization form of gas chromatographic mass spectrometry. Air and rain samples were divided into vaporphase and particle-bound or dissolved and particle-bound fractions, respectively. The results showed that total PCDD/F concentrations in Bloomington, Indiana, has a geometric standard deviation range from 1.4 to 4.4 pg/cu m in air and from 63 to 220 pg/L in rainwater. The vapor-to-particle ratio for individual congeners ranged from 0.01 to 30. The ratio is controlled by the individual congener's vapor pressure and the ambient air temperature. Estimates of washout and the Henry's law constants were obtained using average ambient airmore » and rain data.« less