Photodegradation and volatilization properties of polychlorinated buphenyls (PCBs)
2000
Gesmundo, M.G.S.
Photodegradation and volatilization are two important loss mechanisms for understanding fate and behavior of polychlorinated biphenyls (PCBs) in the environment. Results of photodegradation study of PCBs in decane solution exposed to UV radiation at 254 nm suggest that steric congestion and symmetry affect the photodegradability of PCBs. Steric hindrance among adjacent Cl atoms enhances the photodegradability of PCBs while symmetry renders the molecule less photolabile. Furthermore, the non-ortho chlorinated congeners were found to be more stable against photodegradation. On the other hand, volatilization of PCBs from soil was found to be homolog and temperature dependent. Less chlorinated PCBs, i.e., mono to tetra CBs were found to be more volatile while a positive relationship between volatilization loss and temperature was observed. Similarly with photodegradation, results also revealed an increase in PCB volatilization loss with increase in degree of orthochlorination of the biphenyl ring, while non-ortho congeners were found to be more stable against volatilization. The octanol-air partition coefficient (K sup OA) describes the volatilization potential of PCBs from soil. Data gathered on volatilization loss correlate well with atmospheric composition of PCBs in Japan
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