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ASSESSING ANTHROPOGENIC IMPACT ON SECONDARY POLLUTANT FORMATION IN THE SOUTH EASTERN US VIA AIRBORNE FORMALDEHYDE MEASUREMENTS
Impact/Purpose:
The primary objective of the proposed work is to improve our mechanistic understanding of the anthropogenic influence on processes transforming primary emissions into secondary pollutants, especially ozone and secondary organic aerosol (SOA), and to constrain the temporal and spatial scales of this anthropogenic impact in the SE-US. Specifically, airborne measurements of formaldehyde, in conjunction with a full suite of chemical and meteorological observations, will be used to evaluate the impact of anthropogenic volatile organic carbon (VOC) and nitrogen oxide (NOx) emissions on ozone and SOA production efficiency at the urban-rural interface. Analysis will focus on quantifying the degree of fragmentation versus functionalization, and the related extent of chain terminating reactions during the photochemical lifecycle of biogenic and anthropogenic VOCs. These factors determine the relative ozone productions rates and mass of reactive carbon in the gas and condensed phases. We will evaluate how synergistic and competitive mechanisms interact to influence SOA loadings and optical properties. Formaldehyde measurements will also enable improved isoprene emission models that can then be used as a reference for isoprene inferred from formaldehyde via satellite retrievals, which are critical to regional models of air quality.
Description:
This project will provide a critical, publically available formaldehyde dataset during the SOAS campaign. The major expected result will be an improved understanding of the influence of anthropogenic VOC and NOx emissions on secondary pollutant concentrations and properties in a rural setting. Findings will be framed in the context of the competitive processes of fragmentation versus functionalization during gas-phase photochemical VOC oxidation, allowing results to be generalized across a range of mechanistic scales. Furthermore, it is anticipated that acquired data will be applied to reduce uncertainties in isoprene emission models. Together, these results will improve mechanisms of ozone and SOA production in air quality models. Overall, the project will provide better tools for evaluating strategies to mitigate the anthropogenic influence on air quality, climate, and human health.