Environmental Science and Engineering Seminar

Plumes from sulfur dioxide (SO2) point sources have been shown to be significant contributors to new particle formation (NPF), particle growth, and the formation of climate-relevant particles; however, SO2 emissions in the United States (US) have decreased by ~10× since the early 2000s when prior studies were done. In this talk, I will show results from two recent field campaigns as well as modeling that demonstrate that plumes of SO2 point sources are still significant sources of particles through NPF. First, I will show airborne observations of plume-scale NPF in industrial SO2 point sources over Gary, IN during the AEROMMA field campaign, which followed the particles as they grew to climactically relevant sizes. We estimate that the particle formation rate in the Gary, IN industrial plumes is similar to the primary emission rate from particles from vehicles in nearby Chicago, IL. Second, I will show stationary surface observations of frequent, but interrupted, NPF in Houston, TX during the TRACER field campaign. We show through modelling and airmass trajectories that the NPF appeared interrupted at the stationary sites because the NPF was not happening homogeneously throughout the region. Rather, it was occurring in plumes of urban sources and, in particular, the plume of the W.A. Parrish power plant. These case studies demonstrate the continued importance of SO2 point sources to NPF in the US.