Chemically-informative monitoring of atmospheric aerosols
The atmosphere is a complex chemical reactor in which harmful substances can be introduced through direct emissions or photochemical reactions of emitted precursors. These substances collectively comprise the world's "largest single environmental health risk" according to the World Health Organization (WHO), with aerosols - also referred to as particulate matter - less than 2.5 micrometers in diameter (PM2.5) eliciting particular concern. The ambient mass concentration of PM2.5 is regulated out of concerns for their impact on cardiovascular and respiratory health of the human population, but it is estimated that 84% of the world's population is exposed to conditions that exceed recommended atmospheric concentration limits set forth by the WHO.
Effective monitoring strategies for PM2.5 are necessary to characterize local air quality and understand impacts that emissions and regulations have on their concentrations, but the multitude of sources and resulting chemical complexity of this substance preclude simple approaches. Chemical characterization is, however, a vital tool for understanding how PM2.5 source contributions change over time and location, and providing a means to evaluate our capability to simulate emission, transport, and photochemistry of these particles in numerical air quality models. In this talk, I briefly review the current state-of-the-art for PM2.5 chemical speciation monitoring, and introduce a low-cost, chemically-informative technique based on Fourier transform infrared (FTIR) spectroscopy that can augment current practices. While FTIR has enjoyed a long history for measurement of atmospheric gas composition, interpretation of PM2.5 spectra poses significant challenges that we overcome through judicious selection of calibration samples and mathematical algorithms. I describe our technical efforts to make FTIR useful toward PM2.5 monitoring, together with a means for improving our chemical simulations of atmospheric organic aerosol formation that can be evaluated using FTIR measurements. Finally, I describe novel results from the application of FTIR to monitoring network measurements and other field campaigns that potentially simplifies our understanding of the complex organic fraction in atmospheric particulate matter.
Satoshi Takahama is assistant professor and head of the Atmospheric Particle Research Laboratory (APRL) at the École Polytechnique Fédérale de Lausanne (EPFL) since 2012, where his group has studied topics related to atmospheric composition and processes through numerical simulation, statistical modeling, and hardware development. He received his BS in civil engineering from the University of Texas at Austin and PhD in chemical engineering from Carnegie Mellon University, and spent six years at the Scripps Institution of Oceanography as a postdoc and scientist prior to his appointment at EPFL.