Modeling of the Atmospheric Process of Cyanobacterial Toxins in Algal Aerosol

VICTORIA ZORBAS, Myoseon Jang, University of Florida

     Abstract Number: 304
     Working Group: Aerosol Chemistry

Abstract
Fresh water aerosol enriched in cyanobacterial toxins is produced by breaking waves and bursting bubbles in lakes and estuaries. In this study, the determination of the longevity of toxins in the ambient air is assessed by the development of the Harmful Algal Aerosol Reaction (HAAR) model, which is a kinetic model for predicting the atmospheric process of toxin via heterogeneous reactions of the cyanobacterial microcystins (MCs) with the atmospheric oxidants. Typically, the conjugated alkene of the β-amino acid (ADDA) in MCs reacts with atmospheric oxidants such as O3 and OH radicals. The process of cyanobacterial aerosol and toxins in both daytime and nighttime is observed in a large outdoor photochemical smog reactor (UF-APHOR). The rate constant of the nighttime ozonolysis of MC-LR in algal aerosol is semi empirically estimated by using chamber data at a given gaseous ozone concentration and Henry’s law constant based on a pseudo-first order reaction approach. The MC-LR concentrations are measured using a conventional enzyme-linked immunosorbent assay (ELISA) and compared to data from LC-MS-MS. The water content in cyanobacterial algal aerosol is measured by using a Fourier Transform Infrared Spectrometer and applied to the HAAR model to simulate impact of humidity on the MC-LR decay. The degradation of MC-LR during daytime is faster due to the involvement of the reaction of the conjugated double bond in ADDA with both atmospheric ozone and OH radicals. The daytime degradation of MC-LR in algal aerosol is performed during the photooxidation of 2-methyl-2-butene in the presence of NOx. The simulated degradation of MC-LR in cyanobacterial algal aerosol is compared to experimental data that are performed under varying conditions in the UF-APHOR chamber.