CHEE Seminar: Ali Hossein Mardi
Monday, April 18, 2022 – 3:00 p.m.
Ali Hossein Mardi, Ph.D.
Postdoctoral Scholar
AIRFLows Lab Virginia Polytechnic Institute and State University
“Sources and Impacts of Aerosols in the Atmosphere: Case Studies of Dust and Biomass Burning Pollution”
Harshbarger Bldg., Room 206
Zoom Link
Social Hour: Harshbarger 118B, 2:30 to 2:50 p.m.
ABSTRACT
Atmospheric aerosols are defined as the suspension of small solid or liquid particles in the atmosphere. Ranging in size from a few nanometers up to tens of microns, aerosols come from a wide range of sources and impact many aspects of climate and everyday human life, either directly or indirectly. Biomass burning emissions and airborne aeolian dust are two major components of atmospheric aerosols. Numerous researches have been done to characterize the spatial and temporal patterns observed in the emission and travel of these aerosols worldwide. In the first part of the present study, biomass burning emissions are studied via different sets of analyses. At first, microphysical and chemical characteristics of biomass burning plumes from two major wildfire incidents near the coast of California are studied via a set of airborne probes. From a macrophysical perspective, a statistic review of the smoke plume is provided for parameters such as plume thickness, number of layers, and relative positioning of smoke layer and the residing stratocumulus cloud deck in that region. By simulating the heating rate impact from the biomass burning plume, an enhancement in vertical heating rates is observed. Results show this enhancement is stronger when a stratocumulus cloud layer resides beneath the biomass burning layer. In a separate project, biomass burning impact on cloud microphysical properties is studied through analysis of the connection between cloud droplet number concentration and effective radius with aerosol number concentration above and below the cloud. Our results demonstrate that cloud microphysical characteristics are most sensitive to aerosol properties at the cloud base, rather than cloud top, where the majority of biomass burning aerosols reside. Laboratory composition analysis of cloud water samples collected from biomass burning impacted clouds reveal an impact from crustal species, carried away by biomass burning plumes. This impact is most evident in clouds impacted by plumes of smoke close to the source of the fire. In the following section, we discuss the latest results from an ongoing project, analyzing the plumes of aeolian dust aerosols as a means for across Atlantic transport of microorganisms from North African dust emissions. These plumes reach the downwind regions as far as the U.S. southeast, Caribbean, and Amazon region. First, we explain our methodology for detecting dust emissions and forward trajectory analysis done to track each individual emission event from its source to our regions of interest. Then we explain the spatial and temporal variations observed in the source of emissions and the major transport path during each season. Additionally, we discuss the meteorological conditions experienced by aerosols along their trajectories and their potential impact on the concentration and longevity of microorganisms onboard the dust aerosols.
BIOSKETCH
Ali joined the AIRFLows Lab at Virginia Polytechnic Institute and State University (Vtech) in 2021, under the supervision of Dr. Foroutan, as a postdoctoral scholar. He has a Ph.D. in environmental engineering from the University of Arizona and an M.S. in civil-environmental engineering from the Sharif University of Technology in Iran. His research interest is to study the formation, transport, and fate of aerosols in the atmosphere. Currently, he participates in an interdisciplinary study of Aeolian dust aerosols sourced from northern Africa and their ability to act as a medium for the transportation of microorganisms across the Atlantic.