MPFCS

Mixed Precursor and Future Climate in SE-US

1 June 2025 - 30 June 2025

Lead Scientist: Christian Mark Salvador

Observatory: AMF

The mechanistic representations of Secondary Organic Aerosol (SOA) formation under ambient conditions are typically extrapolated from laboratory-scale oxidation experiments performed with individual volatile organic compounds (VOCs) that are assumed not to interact with each other when presented as mixtures. However, recent empirical evidence shows that multiple coexisting VOC precursors generate unexplored molecular-scale interactions that influence the SOA physiochemical properties (e.g., mass, yield, and water uptake). There is a need to quantify the impacts of multiple precursors on aerosol formation beyond the measurements performed at lab scales. This work proposes the comprehensive investigation of the variability of mixed biogenic and anthropogenic VOCs under real-world ambient conditions and their transformation to aerosols and clouds. The project will utilize Oak Ridge National Laboratory’s high-resolution mass spectrometric capabilities and long-term field measurements at the Bankhead National Forest using ARM’s mobile instrument facility. In particular, the Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (6000X2, Ionicon) will be deployed in the guest cabin of the ARM Mobile Facility from June 1 to June 30, 2025, to uncover the temporal distribution of mixture VOCs. This work will also utilize ARM observation data such as real-time aerosol chemical speciation with a time-of-flight aerosol chemical speciation monitor, particle size distributions using the ultra-high sensitivity aerosol spectrometer (particle diameter dp=0.06 µm to 1 µm), and scanning mobility particle sizer for fine and ultrafine particles. Data generated from the ARM gas sensors for ozone (O3) and sulfur dioxide (SO2) will be beneficial in assessing the degree of oxidation and the effects of anthropogenic activities on aerosol formation. Aerosols forming cloud condensation nuclei (CCN) will be assessed using ARM’s CCN-200, which counts the CCN in different size ranges. From a fundamental perspective, this work will initiate the discussion on an unexplored climate–aerosol feedback loop that considers the varying levels of VOCs of the future and how aerosols and clouds will be altered from our current model representations.