Pollen Effects on Health and Cloud Formation

BRIANNA HENDRICKSON, Sarah Brooks, Yingxiao Zhang, Allison Steiner, Texas A&M University

     Abstract Number: 120
     Working Group: Bioaerosols

Abstract
Under humid atmospheric conditions, pollen grains released by plants can rupture creating pollen grain fragments referred to as subpollen particles (SPPs). Pollen grains and SPPs can be dispersed in the atmosphere and significantly contribute to the aerosol population by acting as ice nucleating particles (INPs) influencing cloud formation and precipitation. To understand the impacts of pollen and SPPs on health and climate, the meteorological conditions required for pollen grain emissions and pollen grain rupture need to be characterized. It is also critical to quantify the SPPs created from a single pollen grain. In this study SPP emission factors were determined for live oak, Quercus virginiana, ryegrass, Lolium perenne, and giant ragweed, Ambrosia trifida. Each species was evaluated using wind-driven SPP release experiments by exposing samples to constant relative humidity while cycling fans used to simulate winds. The SPP emission factors were 2.5x10¹⁶±1.4x10¹⁶ to 1.2x10¹⁹±6.5x10¹⁸ SPPs per acre for live oak, 2.7x10¹⁷±8.9x10¹⁶ SPPs per acre for ryegrass, and 5.4x10¹⁸±4.6x10¹⁸ SPPs per acre for ragweed. Additionally, SPPs and pollen grains for all three species were tested for their ability to act as INPs in immersion mode freezing and pollen grains were also evaluated as INPs in contact mode freezing. Freezing temperatures will be reported for SPPs in immersion mode freezing, pollen grains in contact mode freezing, and pollen grains in immersion mode freezing. INP emission factors will also be determined for all three species. These laboratory results will be incorporated into a regional modeling framework to explore the potential for SPPs and pollen grains to influence health and cloud formation.