PHYSICO-CHEMICAL ARTEFACTS IN ATMOSPHERIC PAH DENUDER SAMPLING

Two annular diffusion denuder-filter samplers were operated concurrently to assess sampling artefacts arising from possible breakthrough of gas-phase PAH, blow-off of particle-bound PAH and degradation due to atmospheric ozone. The results of a field investigation held at Montelibretti (Rome, Italy) indicate that such artefacts are minimized or avoided when 6 h air samples are collected at 6 L min−1 and an ozone scrubbing denuder is placed at the beginning of the sampling train. The partitioning of semi-volatile PAH followed closely that previously observed in downtown Rome but their absolute concentrations were up to an order of magnitude lower.