Fluorescence of Bioparticles: Microscopy, Spectroscopy, and On-line Detection

Christopher Pöhlker (1), J. ALEX HUFFMAN (1), Uli Pöschl (1)

(1) Max Planck Institute for Chemistry, Biogeochemistry Department

     Abstract Number: 868
     Last modified: August 10, 2010

Abstract
Primary biological aerosol particles (PBAP) such as pollen, fungal spores, bacteria, biogenic polymers, and small debris from larger organisms are known to influence atmospheric chemistry and physics, the biosphere and public health. Continuous measurements of the abundance, variability and diversity of PBAP have been difficult until recently, however. The ultraviolet aerodynamic particle sizer (UV-APS) is commercially available and enables detection of fluorescent biological aerosol particles (FBAP) as a lower-limit proxy for PBAP, with high time and size resolution and without perturbing the chemical or metabolic state of the particles. Moreover it can be easily applied to field sampling and can be operated continuously with much less time invested in data analysis than for standard off-line techniques. Uncertainties remain, however, in the fraction of PBAP that the UV-APS technique measures.
In order to better understand the relationship between PBAP and FBAP we utilize off-line bench-top techniques of fluorescence microscopy and fluorescence spectroscopy. Our intent is to compare FBAP characteristics (i.e. particle size, relative fluorescence intensity) using these methods to determine the ability of each to provide complementary information about FBAP. Not only does this investigation provide a secondary check for proper UV-APS interpretation, but may also help provide additional information about FBAP (e.g. density, shape, type).
Several pure types of pollen, fungal spores, bacteria, and potential interferents were investigated in the laboratory. As shown by the off-line techniques, strong differences exist in fluorescence intensity, depending on type, metabolic state and size of the particle. Pollen particles were usually the most fluorescent particles sampled, while fungal spores exhibited a varying level of fluorescent emission. Examples of non-biological material chosen for analysis did not show high levels of fluorescence. The information gained by this analysis will be very useful for interpretation of past and future ambient FBAP data.