Dusty cities, smoky skies, and old paint: air quality, climate, health, and cultural impacts of chemistry at atmospheric interfaces

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Atmospheric particulate matter (PM) influences Earth's climate, contributes to air quality reductions, and provides a surface for chemical reactions; these reactions, in turn, can influence the abundance of pollutant gases (e.g. O3 and NO2) and the fate of PM-associated species. Here, we propose research in four linked themes, each of which explores a different aspect of chemistry at atmospheric interfaces: 1-Photochemistry of dust and non--exhaust PM: implications for pollutant fate, PM composition, and urban air quality As vehicle emission regulations tighten, the contribution of non-exhaust sources (e.g. road dust, brake/tire wear) to urban PM loadings will increase. We propose to study a) reactive oxidant production by road dust, and the implications of this production for the fate of urban contaminants; b) the influence of dust--catalyzed organic transformations on PM composition and properties; and c) the impact of road dust/non--exhaust PM chemistry on the gas-phase composition of the urban atmosphere. 2-Climate, air quality, and health impacts of boreal wildfires Boreal wildfires are increasing in both frequency and intensity. We propose to a) quantify the conversion of NO2 to nitrous acid (HONO), an important atmospheric oxidant precursor, by boreal wildfire PM; b) apply size-exclusion chromatography coupled with UV-Vis detection to investigate the light--absorbing (i.e. climate--relevant) properties of this PM as a function of combustion conditions; and c) assess the lifetime and fate of toxic contaminants at the surface of wildfire ash. 3-New high--throughput instrumentation for study of PM-pollutant interactions In Themes 1 and 2, we quantify gas-surface interactions using flow tube instrumentation, which enables the detailed study of individual pollutant-substrate pairs. However, this approach is too time-consuming to permit exploratory (i.e. non-targeted) study of large PM sample sets. Motivated by medicinal and materials chemistry approaches to drug discovery and catalyst screening, we propose to a) develop and validate a new high--throughput modular photoreactor for study of pollutant gas-PM interactions; and b) apply this reactor to uncover predictive relationships between PM composition/properties and reactivity. 4-Exploring air quality challenges in museum environments Cultural heritage objects are displayed and stored in microclimate-like environments (e.g. frames and storage crates) and are thus susceptible to damage by emissions from enclosure materials (e.g. formaldehyde, acetic/formic acid). We propose to apply strategies developed in Themes 1-3 to a) quantify potential biases associated with formic acid sampling in museum environments; b) obtain kinetic data for gas-surface pairs relevant to museum storage environments; and c) implement these data in simple microclimate enclosure models, which will enable us to better interpret/apply pollutant measurements obtained in museum air quality campaigns.