AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Chemical Imaging of Atmospheric Particles Sampled over Agricultural Fields in Indiana
JAY TOMLIN, Kevin Jankowshi, Swarup China, Brian Stirm, Robert Kaeser, Paul Shepson, Alexander Laskin, Purdue University
Abstract Number: 440 Working Group: Remote and Regional Atmospheric Aerosol
Abstract The midwestern United States is a geographical region with large-scale agricultural fields. Crops in this region include corn, soybeans, and wheat among others, which all co-exist with a myriad of biological microorganisms (e.g. bacteria, yeasts, spores of actinomycetes and fungi, etc.). The harvesting of these crops aerosolizes biological particles and injects them into the atmosphere, contributing to the overall diversity of atmospheric particles in the area. A notable trait of airborne fungal spores is their ability to disintegrate into smaller particles upon hydration/dehydration cycles. This phenomenon is believed to have relevance to certain episodes of particle emissions reported over vegetated areas. Upon crop harvest, the aerosol mixing states and composition pertinent to these agricultural regions are disproportionally influenced by large amounts of fine plant fragments, soil dust, and biological spores released into the atmosphere. Resulted fine particles then travel long distances, depending on their size and the meteorological conditions. Recognizing the agricultural cycles in these regions, we can derive a predictive understanding of particle emissions in the local area. In this work, we collected ambient particles on board a research aircraft and sampled across agriculture fields and forests in the rural regions of Indiana. Collected samples were then analyzed using computer-controlled scanning electron microscope coupled with elemental microanalysis to describe particle-type population on statistically significant number of analyzed particles and Scanning Transmission X-ray Microscopy to provide quantitative metrics on particle internal heterogeneity. In addition, we used HYSPLIT dispersion modelling to provide insight into the complex transport and depositions of particles released from crop harvesting. Evaluating yet underrepresented sources for particle formation, such as biological particles and their fragments will contribute to improved inventories of atmospheric aerosols, essential to issues of climate, weather, and air quality.