Particulate Nitro/Oxy-PAH size distribution and PAH degradation during sampling in two sites around Paris (France)
Abstract
Benzo[a]pyrene (B[a]P) which is used as a tracer for PAH family is very toxic and reactive. It may be degradated by different oxidants in the atmosphere or during its sampling on filters. PAH on-filter degradation was studied during two field campaigns (traffic site and photooxidation site). A MnO2 denuder was used to protect the sampling filter from potential ozone exposure in order to evaluate PAH degradation during sampling. B[a]P was the only PAH really influenced by the presence of the denuder. PCAs were developed to understand which factors may rule such degradation. It appears that no factor may explain alone this degradation, it depends on several parameters such as [O3], particles age, [B[a]P] etc. Finally, size distributions of different PAH degradation products were measured thanks to a twelve stage cascade impactor, in order to provide information on their origin/source: primary (direct emission) or secondary (formed in the atmosphere or on the sampling filter).