A comparison of real-world outdoor aging of Bacillus thuringiensis bioaerosols using Goldberg rotating drums and synthetic spider webs in Conroe, Texas

There are two predominant methods for understanding and studying bioaerosol aging: capture on microfibers, and Goldberg rotating drums. There are advantages and disadvantages to each approach depending on the experimental needs, cost, and timeline, but they have rarely been compared in parallel to determine the similarity of results. Experiments that use Goldberg drums have the advantage of studying aerosol particles in suspension, but due time resolution of aging processes is limited by chamber volume, sample volumes, and aerosol loss mechanisms. For microfiber experiments, particles are adhered to the fiber, and so only simulate natural aerosols, but there are significant advantages since particles are not lost during aging and the time resolution is not limited by sampling. In this study, we compared outdoor UV-transmitting Goldberg rotating drums with polymethyl methacrylate (PMMA) synthetic spider web material in a complex real-world environment during a summer near Houston, Texas. Bacillus thuringiensis al hakam spores were aerosolized into UV-transmitting, gas-permeable chambers that allowed relevant exposure to real-world atmospheric conditions while isolating particles of interest. Aging was compared for up to 4 h in both sunlight exposed and protected environments to compare and quantify relative degradation rates. The two disparate methodologies yielded similar results, with no statistical difference found in three out of four combinations of carbon-filtered air vs. ambient air, and protection from sunlight vs. exposure to sunlight, but this could vary for other particle sizes or organisms.