The Interactions of Airborne Particles with Surfaces

Airborne particles exist in a wide variety of shapes, sizes, and chemical compositions. Some are natural, some are emitted from human activities, and others are formed in the atmosphere from gases. The gases can also be natural or anthropogenic. Once airborne, particles can be carried hundreds or even thousands of kilometers by wind before interacting with surfaces and depositing. In this talk, we examine the many ways in which atmospheric particles interact with surfaces of all kinds – natural vegetation, agriculture crops, landscaping, bare soil, water, snowfields, and urban hardscape surfaces. Such understanding is important when predicting the ultimate fate of particulate matter, whether the particles are inhaled and reach the human respiratory system, or whether they deposit on surfaces and cause damage. In all cases of deposition from the atmosphere, particles carried in the mainstream of the airflow must somehow be delivered to the quasi-laminar boundary layer adjacent to the surface, and must then traverse the boundary layer to rest on the surface. Estimating deposition to buildings, roads, and other urban surfaces can be a challenge due to the changes in geometry of the surface over short distance scales. We discuss the special case of estimating particle deposition onto urban surfaces, include a large extensive green roof. Both modeling and measurement of particle interaction with surfaces is presented, and use of well-controlled experimental surfaces in wind tunnels as well as in the ambient atmosphere is discussed as a means of improving our understanding of the deposition process. A separate tutorial covering the airflow and rain impinging on a green roof in Syracuse, NY will be presented. The tutorial will explain the capabilities of a new website showing real-time data and archived data from the green roof.

Cliff Davidson received his BS in Electrical Engineering from Carnegie Mellon University, and his MS and PhD degrees in Environmental Engineering Science from California Institute of Technology. Following his PhD, he joined the Carnegie Mellon faculty in the Department of Civil and Environmental Engineering and the Department of Engineering and Public Policy. Davidson has written and edited a number of books, has over 200 refereed publications, and was President of the American Association for Aerosol Research during 1999-2000.

He is the Founding Director of the Center for Sustainable Engineering, a partnership among several universities led by Syracuse University. In his capacity as Director, he has organized many workshops to help faculty members add content in sustainability and sustainable development into engineering courses. Davidson retired in 2023 as the Thomas and Colleen Wilmot Professor of Engineering at Syracuse University in Syracuse, NY, stepping down as Director of Environmental Engineering. However, he continues working with an active research group as Professor Emeritus.