A continuous, high resolution record of urban airborne particulates suitable for retrospective microscopical analysis

This paper describes the use of a portable particle impactor (the Burkard Spore Trap) for monitoring urban aerosols such that a continuous, permanent, high resolution record is obtained, periods of interest can be readily determined and retrospective analysis can be undertaken directly. Simultaneous use of two collection substrates allows that different analyses (e.g. light microscopy, chemical analyses, digital imaging) can be performed on almost identical samples over precisely defined time periods. Preliminary results are presented giving a few examples of the sort of studies possible using the approach. Comparison with the Enhanced Urban Networksʹ TEOM PM10 data, suggest that the TEOM (measuring by mass) responds to a relatively small number of large particles and not the smaller, more numerous, and from a human health perspective more important size fractions (i.e. < 2.5 μm). This is emphasised when studying trends in various size classes during a rain event where the larger fraction (and TEOM) shows decreases due to “washout” whereas finer fractions show little change in trends. Results also suggest that biological particulates (e.g. fungal spores) may form a significant fraction ( > 20%) of the urban aerosol especially following rain events. The versatility of the sampler, coupled with its portability and battery powering suggests great potential for the technique in applications to a wide variety of particulate studies.