Bioaerosol Analysis Using Photothermal Infrared Spectroscopy: Case Study with Aerosols from Cyanobacterial Harmful Algal Blooms

CARLIE POWOROZNEK, Jia Shi, Rebecca Parham, Katherine Kolozsvari, Yao Xiao, Nicole Olson, Johnna Birbeck, Stephen Jacquemin, Judy Westrick, Andrew Ault, University of Michigan

     Abstract Number: 747
     Working Group: Aerosol-Ecosystem Interactions

Abstract
Freshwater systems constantly release particles into the air, called lake spray aerosol (LSA), which impacts the environment and human health. These aerosol particles can contain biological material. Not only can these bioaerosol particles act as effective ice-nucleating particles (INPs) and cloud-condensing nuclei (CCN) but they can also contain biogenic toxins. Freshwater systems can undergo cyanobacteria harmful algal blooms (cHABs) where there is a dramatic increase in biological activity. The effects cHABs have on the water have been decently studied but the resulting increase in the amount of bioaerosol has not been researched thoroughly. To understand the impact cHABs have on the environment and the health of residents nearby it is important to know the composition of the aerosol. However, single particle analysis of bioaerosol presents many challenges. The resolution needs to be below a few micrometers, limiting traditional infrared spectroscopy, and biological particles tend to fluoresce under increased energy, limiting Raman spectroscopy. To combat this photothermal infrared (PTIR) spectroscopy methods were used. Atomic force microscopy (AFM) PTIR and optical photothermal infrared (OPTIR) were used to analyze the individual particles from laboratory-generated aerosol taken from water containing a cHAB. These methods use a probe, a cantilever and a beam of visual light respectively, and changes in the deflection or the scattered light are measured as an IR source is activated to determine when the particle is IR active. The AFM-PTIR was able to measure particles with a diameter from 0.18 to 0.32 µm while the OPTIR analyzed particles with a diameter of 1.8-3.2 µm. Results showed that the percentage of biological particles increased significantly at larger particle diameters. These results not only are helpful in analyzing the impact of bioaerosol from cHABs, but also provide evidence for OPTIR and AFM-PTIR being useful techniques for future bioaerosol analysis.