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Turbulent Dispersion of Biological Particles in the Atmosphere

Speaker: Marcelo Chamecki, Penn State University
Series: CEE Departmental Seminars
Location: Bowen Hall Auditorium
Date/Time: Tuesday, April 12, 2011, 4:30 p.m. - 5:30 p.m.

Abstract:

Dispersion of biological particles such as pollens and pathogenic spores play an important role in fields such as ecology and agronomy. The recent development of genetically modified crops and questions about cross-pollination and subsequent contamination of natural plant populations enhanced the importance of understanding wind dispersion of airborne pollen. Pathogenic spores that cause plant diseases in field crops are a major threat to food production and reliable models to predict the spread of these diseases are critical for efficacious management and U.S. food security. In both applications, a critical question to be addressed is how far from the source field pollen grains/spores will be transported before they deposit on the ground/vegetation.

In this talk I will use a simplified model scenario consisting of an area source emitting small particles into the turbulent atmospheric boundary layer to study dispersion of pollens and spores. I will present new theoretical results derived by assuming that the particle plume above the source field behaves as a particle concentration boundary layer. In particular, boundary-layer scaling and the assumption of self-preservation lead to a similarity solution to the advection-diffusion-deposition equation and to predictions of the deposition flux downwind from the source. The assumptions required and the results obtained from the theoretical model are validated using two data sets: (i) a suite of high-resolution numerical experiments based on the large-eddy simulation technique, and (ii) experimental measurements of spore concentration above a wheat field naturally infected with leaf rust. Applications of the new theoretical model to studies of pollen flow and spread of plant diseases will also be discussed.