Changes in the Fluorescence of Biological Particles Exposed to Environmental Conditions in the National Capitol Region

Abstract

A variety of methods have been used to study atmospheric bioaerosols. A common technique employed for the detection and measurement of bioaerosols is the measurement of the autofluorescence of biological particles when excited by ultraviolet light. We examined the changes in the fluorescence spectra of bioaerosols when exposed to ambient outdoor conditions for periods of several hours. The bioaerosols in this study were contained in a Captive Aerosol Growth and Evolution (CAGE) chamber that employed two rotating drums constructed with an exterior FEP Teflon film to allow sunlight to penetrate and an inner ePTFE membrane to allow ambient trace gasses to permeate the drums. The bioaerosols were periodically measured with a TSI UV-APS (excited at 355 nm) and a single-particle fluorescence spectrometer (excited at 351 and 263 nm). The data indicate changes in both fluorescence spectral profile and intensity from Bacillus thuringiensis var. kurstaki spores and MS2 bacteriophage particles during the experiments. The changes observed in these particles appear to be due to a combination of the environmental conditions rather than attributable to any single factor. The results of this study indicate that bioaerosols are significantly altered by atmospheric aging processes and that these changes may affect measurements by ultra-violet light induced fluorescence (UV-LIF) or other spectroscopic techniques.