Gas/particle partition measurements of PAH at Hazelrigg, UK

During September and October, 1998, the new Integrated Organic Gas and Part icle Sampler (IOGAPS), was operated at Hazelrigg, UK, the field measurement station of the University of Lancaster. Gas/particle partition ratios Of t wenty-two 2-5 ring PAH were determined using both the IOGAPS (in which the gas phase is collected before the particle phase) and a low now sampler whi ch utilized the traditional filter-sorbent geometry. For compounds of inter mediate volatility, less partitioning to the gas phase was observed when th e denuder was used. The denuder (8- channel, 60 cm, 16.7 L min(-1) air samp ling rate) trapped small amounts of several non-volatile PAH. This result i s consistent with particle diffusion losses of 5 to 10% for particles less than 0.05 mum under the flow conditions in the denuder. The 60-cm denuder w as probably longer than necessary for the now rate used. During the samplin g, both glass fiber and Teflon-coated glass fiber filters were used. Withou t a denuder in front of a glass fiber filter, the fine particulate mass (PM 2.5) measurements showed a major positive bias that has been attributed to adsorption of gases by the filter. Tenon-coated glass fiber filters were n ot subject to this artifact problem, and equal masses were collected on fil ters from the denuded and non-denuded air flows.