Determining the Coagulation Sink Rate for Sub-10 nm Atmospheric Particles

The research team in this proposal will combine laboratory experiments and theoretical modeling in order to address uncertainties and oversimplifications in our understanding of coagulation sink rates of cloud condensation nuclei and their impacts on aerosols, their atmospheric survival, and aerosol scavenging and coagulation. As coagulation sink rates cannot be directly measured, they are currently approximated via the “hard-sphere” model, which has known uncertainties and limitations. This work aims to fill this knowledge gap. Success in this project will positively impact multiple fields of scientific research, including fields outside of the atmospheric sciences. The proposed educational and outreach plans are strong as K-12, undergraduate, and graduate students will gain valuable knowledge and experience during this project. Specifically, this proposed work will investigate coagulation sink events by comparing coagulation rates between sub-10 and 50-100 nanometer cloud condensation nuclei. There are three primary objectives in this proposed work. First, an investigation of Van der Walls-enhanced coagulation sink rates of newly formed particles. Second, an exploration of image potential-enhanced coagulation sink rates. Finally, an evaluation of the impact of chemical composition on coagulation sink rates. Research tasks in this project include: (1) the first experimental validation of coagulation rate models that incorporate Van der Walls potentials for sub-10 nanometer and 50-100 nanometer cloud condensation nuclei; (2) an innovative investigation of image potential effects on coagulation rates; (3) an update to our understanding of coagulation sink rates for chemically heterogenous particle coagulation; and (4) an improved coagulation model. Results from this proposed work will be incorporated into curricula which includes hands-on laboratory experience for both undergraduate and graduate students. Additionally, a curriculum for summer camp programs reaching K-12 students will be developed. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.