Decreases in Epoxide-Driven Secondary Organic Aerosol Production under Highly Acidic Conditions: The Importance of Acid-Base Equilibria.

Isoprene has the highest atmospheric emissions of any nonmethane hydrocarbon, and isoprene epoxydiols (IEPOX) are well-established oxidation products and the primary contributors forming isoprene-derived secondary organic aerosol (SOA). Highly acidic particles (pH 0-3) widespread across the lower troposphere enable acid-driven multiphase chemistry of IEPOX, such as epoxide ring-opening reactions forming methyltetrol sulfates through nucleophilic attack of sulfate (SO). Herein, we systematically demonstrate an unexpected decrease in SOA formation from IEPOX on highly acidic particles (pH < 1).

Aerosolized Cyanobacterial Harmful Algal Bloom Toxins: Microcystin Congeners Quantified in the Atmosphere.

Cyanobacterial harmful algal blooms (cHABs) have the potential to adversely affect public health through the production of toxins such as microcystins, which consist of numerous molecularly distinct congeners. Microcystins have been observed in the atmosphere after emission from freshwater lakes, but little is known about the health effects of inhaling microcystins and the factors contributing to microcystin aerosolization. This study quantified total microcystin concentrations in water and aerosol samples collected around Grand Lake St.

Initial pH Governs Secondary Organic Aerosol Phase State and Morphology after Uptake of Isoprene Epoxydiols (IEPOX).

Aerosol acidity increases secondary organic aerosol (SOA) formed from the reactive uptake of isoprene-derived epoxydiols (IEPOX) by enhancing condensed-phase reactions within sulfate-containing submicron particles, leading to low-volatility organic products. However, the link between the initial aerosol acidity and the resulting physicochemical properties of IEPOX-derived SOA remains uncertain. Herein, we show distinct differences in the morphology, phase state, and chemical composition of individual organic-inorganic mixed particles after IEPOX uptake to ammonium sulfate particles with different initial atmospherically relevant acidities (pH = 1, 3, and 5).