Assessing anthropogenic impact on secondary pollutant formation in the South Eastern US via airborne formaldehyde measurementsEPA Grant Number: R835406
Title: Assessing anthropogenic impact on secondary pollutant formation in the South Eastern US via airborne formaldehyde measurements
Investigators: Keutsch, Frank N
Institution: University of Wisconsin Madison
EPA Project Officer: Chung, Serena
Project Period: April 1, 2013 through March 31, 2015 (Extended to March 31, 2016)
Project Amount: $194,183
RFA: Anthropogenic Influences on Organic Aerosol Formation and Regional Climate Implications (2012) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Global Climate Change , Climate Change , Air
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.
Formaldehyde measurements will be obtained on the NOAA P3 during the Southern Oxidant and Aerosol Study (SOAS) as part of the simultaneous NOAA Southeast Nexus (SENEX) campaign. We will deploy a custom-built instrument utilizing fiber-laser induced fluorescence for measurement of formaldehyde, a technique developed by the Keutsch research group at UWMadison that has unparalleled sensitivity and provides high-time resolution data. The data will be used in conjunction with the large suite of other measurements on the NOAA P3 in a comprehensive analysis that makes use of ratios of oxidation products and primary emissions to dissect the complex gas-phase photochemistry under varying anthropogenic influence. Measurements, especially those of oxidation product ratios, will be analyzed using 0-D and 1-D chemical box models to evaluate and improve our understanding of current gas-phase mechanisms. Observations will also be used to quantify the temporal and spatial scale of anthropogenic influence at this site and to provide constraints on regional emissions of isoprene, which will lead to improved regional chemical transport models.
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.