Speaker – Brett Gantt from EPA (hosted by Nicholas Meskhidze)  |

Seminar Title – Air Quality Research at the EPA: Hemispheric to Urban Scales

Reception beforehand at 3:00 PM in 1132 Jordan Hall.

Abstract – As emissions from point sources such as power plants have been reduced over much of the United States, the focus of air quality research at the Environmental Protection Agency (EPA) has trended away from the regional scale and towards both the urban and international scales. Two such areas of research include the characterization of air quality 1) near major highways and 2) in the marine boundary layer. For Part 1, we analyzed ambient concentrations of particulate matter less than 2.5 micrometers in diameter (PM2.5) at a national network of sites in the vicinity of major highways. Using spatial interpolation to estimate the near-road PM2.5 increment on an hourly and daily basis, we found that the average daily increment is 1.1 μg m-3 with higher values on the weekdays than weekend and much higher values when the monitor is downwind of the highway. For Part 2, we implemented marine halogen chemistry in the Community Multiscale Air Quality (CMAQ) model to better simulate the ozone (O3) over the marine boundary layer.  This new chemistry in the model improved simulated O3 concentrations along the coast and over the open ocean, and had a substantial reduction (>5 ppb) on simulated O3 concentrations over the ocean and well inland in the continental US.