Professor Jesse Kroll of CEE and chemical engineering was awarded the Macelwane Medal by the American Geophysical Union at its annual meeting held Dec. 9-13 in San Francisco. Established in 1961, the Macelwane Medal is awarded annually to young scientists for significant contributions to the geophysical sciences. Kroll’s research focuses on experimental studies of the properties and chemical transformations of organic molecules in Earth’s atmosphere emitted by both anthropogenic activities and biogenic processes. This work is particularly important because atmospheric organic species form a large fraction of the airborne submicron particles responsible for most of the adverse human health effects attributed to poor air quality.