Atmospheric Microplastic Quantification with Automated Microspectroscopic Techniques
REBECCA PARHAM, Abby Ayala, Lauren Meagher, Madeline Clough, Eduardo Ochoa, Jia Shi, Scarlet Aguilar-Martinez, Ambuj Tewari, Paul Zimmerman, Allison Steiner, Anne McNeil, Andrew Ault, University of Michigan
Abstract Number: 108
Working Group: Chemicals of Emerging Concern in Aerosol: Sources, Transformations, and Impacts
Abstract
Microplastics (MPs), or pieces of plastic between 1-5000 μm in length, have been studied since the early 2000s and are considered globally ubiquitous; however, the atmospheric deposition of MPs has only been reported within the past decade. Research has since recorded MP fallout in both urban and remote locations across the globe, with deposition rates ranging from 0 to 1000s of MPs/m2/day. Microspectroscopy techniques, notably infrared (IR) techniques, are the primary methods of identifying environmental MPs since they can obtain the physical properties of particles, such as their size and shape, in addition to their molecular composition. These techniques, however, cannot detect particulate matter less than 2.5 μm in diameter (PM2.5), posing a significant limitation to the quantification of MPs in smaller size ranges. Herein, this study will utilize computer-controlled optical photothermal infrared spectroscopy coupled with Raman spectroscopy (CC-OPTIR+Raman) for the identification and quantification of atmospheric MPs. Not only can O-PTIR surpass the spatial limitations of traditional IR techniques and resolve particles down to 1 μm, but it can also be paired with a Raman spectrometer for simultaneous IR and Raman analysis. Moreover, the mIRage O-PTIR+Raman, the instrument used for this study, recently acquired the means to automate the detection and analysis of particles within a field of view. The analytical capabilities of CC-OPTIR+Raman for MPs was determined by analyzing a mix of laboratory-generated and ambient samples of increasing complexity. Acquisition of both PTIR and Raman spectra improved the overall identification capabilities of the method, demonstrating how the technique can be used to gain a better understanding of the general population’s exposure to atmospheric MPs and their potential consequences to human health. Future work will apply CC-OPTIR+Raman to assess atmospheric MP concentrations in field samples collected in the Midwest region of the United States.