Radiocarbon Analysis Source Apportionment of Fossil and Modern Atmospheric Carbon from DISCOVER-AQ Houston

Abstract:

DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Resolved Observations Relevant to Air Quality) is a sampling campaign aimed to monitor regional atmospheric pollutants within a collection of cities across the United States. In September 2013, ground-based air samplers were placed selectively to represent the city of Houston: Moody Tower (downtown; urban) and Manvel Croix (southern; suburb), Conroe (far north; suburb) and La Porte (east; urban industrial), with the goal of understanding particulate matter sources and composition and exposure in urban communities. Radiocarbon analysis was conducted on TSP (total suspended particulate matter) and PM_2.5 (particulate matter less than 2.5 µm in aerodynamic diameter) from ground-based samplers. Radiocarbon is used to determine the contributions of contemporary and fossil sources to carbonaceous aerosol in Houston. Contemporary sources of atmospheric carbon in TSP and PM_2.5 include primary biogenic emissions, biomass combustion and SOA produced in the atmosphere from biogenic- and biomass combustion-derived volatile organic carbon. Fossil sources of atmospheric carbon in PM_2.5 and TSP include all types of primary fossil fuel combustion and SOA produced in the atmosphere from fossil-derived volatile organic carbon. Results from the last week of the campaign, September 21-28^th, displayed a PM_2.5 contemporary carbon fraction of 48-78% for Moody Tower, 59-86% for Manvel Croix, 66-89% for Conroe. Ambient TSP had contemporary carbon fractions of 51-65% for Moody Tower and 51-83% for La Porte.