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Spray Aerosol Emissions from Harmful Cyanobacterial Blooms in the Chowan River, NC
HALEY E. PLAAS, Karsten Baumann, Ryan Paerl, Kimberly Popendorf, Colleen Karl, Jill Paxson, Naomi Chang, Joel Sanchez, Huang Hwa, Malcolm A. Barnard, Daniela Maizel, Hans W. Paerl, University of North Carolina at Chapel Hill
Abstract Number: 338
Working Group: Health-Related Aerosols
Abstract
In addition to obvious negative effects on water quality, recent findings suggest that harmful cyanobacterial blooms (CHABs) impact air quality via primary spray aerosol emissions carrying cyanobacterial cells and cyanotoxins. The objective of our study was to quantify CHAB toxins and examine CHAB DNA sequence diversity in the airshed of the Chowan River, a eutrophic estuary in coastal North Carolina facing recurrent CHABs. Our field campaign (Summers 2020—2021) was the first to evaluate inhalation as a potential exposure pathway to cyanotoxins in NC. From June—October 2020, several two-week integrated, daytime (diel (24h) cycle) PM2.5 samples were collected using medium-volume samplers. Offline analytical methods were applied to examine DNA and toxins in water and aerosol samples. Physicochemical water parameters, ambient PM2.5 mass concentration, and meteorological conditions were also recorded down to 1 minute resolution. In 2020, CHAB genera dominated algal biomass, but maximum toxin concentrations and toxin-encoding genes (mcyA) in water samples were low (<<1 µg/L), yielding aerosol concentrations below the limits of quantification. However, two cyanotoxin congeners demonstrated to be enriched in aerosol, MC-LA (microcystin leucine-alanine) and MC-LR (leucine-arginine), were quantified in water samples. Airborne CHAB populations are still being evaluated based on DNA sequencing. Summer 2021, we refined our aerosol collection approaches to better characterize the physicochemical properties of airborne CHAB toxins. Due to the ecological properties of cyanobacteria, and their toxins primarily detected intracellularly, we hypothesized that toxins are aerosolized within intact cells and concentrated in the coarse mode. Using high-volume samplers, we simultaneously collected PM2.5 and PM10, and performed the same offline toxin analyses. We also used a Biospot 300-P Bioaerosol Sampler to evaluate the viability of CHAB cells in aerosol. Biospot aliquots were cultured as mixed assemblages for later DNA-based identification.