VAPOR-PRESSURES AND PREDICTED PARTICLE GAS DISTRIBUTIONS OF POLYCHLORINATED BIPHENYL CONGENERS AS FUNCTIONS OF TEMPERATURE AND ORTHO-CHLORINE SUBSTITUTION

Parameters are given for calculating saturation liquid-phase vapor pre ssures (p(L)o, Pa) of 180 polychlorinated biphenyl (PCB) congeners as functions of temperature and ortho-chlorine substitution. These are sl opes (m(L)) and intercepts (b(L)) of the equation log p(L)o = m(L)/T b(L). Values of m(L) and b(L) were obtained from gas chromatographic retention data for 32 PCB congeners. These slopes varied regularly wit h homolog (number of total chlorines) and also with the number of orth o-chlorines. From this information, m(L) and b(L) values were estimate d for 148 other PCBs whose vapor pressures had been reported at only a fixed temperature. Vapor pressure data were applied to predicting the adsorption of PCBs to aerosols at 10 and 25-degrees-C, using the Jung e-Pankow equation. Particulate percentages increased with homolog numb er, from 2-5% for trichlorobiphenyls to >90% for octachlorobiphenyls a t 10-degrees-C. Within each homolog, PCBs with fewer ortho-chlorines ( and consequently lower p(L)o had increased particulate percentages. Th ese results suggest that the more highly toxic mono- and non-ortho-PCB s are associated to a greater degree with particles in ambient air, an d consequently more likely to be removed by precipitation and dry depo sition.