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Chemical Analyses And Reactions In The Characterisation Of Atmospheric Particulates


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D. Shooter, H. Wang, H. Madhavaram, I. Senaratne & O. R. Khanal


Chemical analyses and reactions in the characterisation of atmospheric particulates D. Shooter, H. Wang, H. Madhavaram, I. Senaratne & O.R. Khanal School of Geography and Environmental Science The University of Auckland New Zealand Abstract Particulates collected in three New Zealand cities have been characterised using a variety of chemical analyses. Collection was using either a high volume sampler, or a low volume VAPS sampler which provided fine (<2.5 pm) and coarse (2.5 - 10.0 pm) particulates. Particulate concentrations were measured to indicate overall levels of particulate pollution in the cities. Ion chromatography of the water soluble components was used to determine the sea salt contribution, and the sources of non-sea salt ions associated with the particulates. Elemental analyses (PIXE and ICP-MS) have provided a more detailed source apportionment, with the Auckland brown hazes which appear in calm conditions seen to have a distinct elemental composition. Analysis of the volatile components of particulates has provided insight into the variety of compounds associated with particulates, with specific compounds being useful as indicators of local sources. Particulate PAH concentrations have also been measured and used for source determination. While analysis of chemical composition is useful, it is often assumed that the composition of the particulates does not vary temporally or spatially. However a number processes such as ozone reactions, photochemical reactions, surface deposition, surface evaporation and aging are all now recognised as processes that can operate during the lifetime of a particle and change its characteristics. Consequently in addition to the results of conventional chemical analyses we report on some addition properties of particulates. Laboratory studies in a photochemical cell of the decay of isoprene in the gas phase in the presence of urban particulates have shown that isoprene is lost when the cell is irradiated with simulated sunlight. Also electron paramagnetic resonance measurements