Recent decadal trend analysis of organic aerosol mass concentrations, calculated as 1.8 times total organic carbon (TOC) mass concentrations, shows decreasing trends in the southeast US and across the contiguous US (CONUS) that can be related to decreases in anthropogenic emissions. We investigate decadal trends in specific organic carbon (OC) volatility fractions OC1, OC2, OC3, and OC4 as defined and reported at 202 locations in the Interagency Monitoring of PROtected Visual Environments (IMPROVE) monitoring network from 2005-2016. We account for spatial differences in organic mass (OM) using regionally-specific OM:OC ratios and analyze 23 chemical climatology regions defined by IMPROVE across the CONUS independently. We find that TOC mass concentrations decrease in all regions, and trends are driven by specific OC fractions that vary spatially. Across the CONUS, the mass concentrations of the most volatile fractions OC1 and OC2 are the most reduced. There are substantial changes to the fractional contributions of the constituent OC fractions to TOC across this time period.

Decadal trends in organic carbon volatility fractions across the United States

2019 Fall National Meeting

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