Analytical Chemistry Seminar: Noah Fierer and Hyungu Kang
Analytical & Environmental Chemistry Division and Atmospheric Chemistry Program Seminar
Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program
Diversity of bioaerosols in indoor and outdoor air across the U.S.
by Noah Fierer - Associate Professor, Ecology and Evolutionary Biology and Fellow of CIRES, University of Colorado Boulder
Every time we breathe we are inhaling thousands of bacterial cells, fungal cells, and pollen grains. Although most of these microbes are innocuous, it is well-established that some airborne bacteria, fungi, and pollen can have important effects on human health. However, we have a limited understanding of how these bioaerosols vary across different geographic regions or the factors that structure their biogeographical patterns. We conducted a citizen science project that involved collecting dust samples from inside and outside ~1,500 households located across the U.S. to understand the continental-scale distributions of bacteria and fungi in indoor and outdoor air. We used high-throughput DNA sequencing to assess the diversity and sources of these bioaerosols, yielding our first insight into the continental-scale distributions of bioaerosols and how they are influenced by climate, land-use, home occupants, and home design.
Size-Dependent Molecular-Level Characterization of Secondary Organic Aerosol from NO3 Initiated Δ-carene Oxidation using Nanospray Desorption Electrospray Ionization High-Resolution Mass Spectrometry
by Hyungu Kang - Department of Chemistry and Biochemistry
We have collected size-separated Δ-carene oxidation aerosol samples using a Micro-orifice Uniform Deposit Impactor (MOUDI) by injecting Δ-carene into a dark flow-through chamber under low RH conditions (< 30%) with O3 and NO2 so the dominant reaction pathway would be with NO3 to form highly oxidized products.
The samples were analysed with a Nanospray Desorption Electrospray Ionization (nano-DESI) high-resolution mass spectrometer in both the positive and negative modes to reveal that the faster growing, and thus larger diameter, branch had a higher oxygen-to-carbon (O:C) ratio when compared with the lower branch, suggesting that the faster growing branch is more oxidized. Furthermore, the most intense peaks from the two branches were compositionally different, but a significant proportion of the formulas identified had N:C ratios of ~0.1, which suggests that organic nitrates are a large component of the aerosol products.