Isolating and Quantifying Contribution of Biomass Burning (Regional), Inter-continental Dust (Global), and Locally Transported Particulate Matter (PM) to Ambient PM10 and PM2.5 Concentrations of an Urban Atmosphere: A Year-round Study at Houston, TX, USA

Abstract:

Understanding the global, regional (biomass burning), and local transport of PM to the atmosphere is critical to understand processes (both natural and anthropogenic) that determine the air quality of a region. Detailed elemental analysis of ambient PM₁₀ and PM_2.5 helped us to distinguish and quantify the contribution of biomass burning (regional transport), inter-continental Saharan dust (global transport), and other local sources to ambient PM₁₀ and PM_2.5, using the Chemical Mass Balance (CMB) model. 12—22 days integrated samples taken from 31 Jul 2014 to 10 Aug 2015 helped us even understand the temporal pattern of the transported dust/smoke at Houston, TX, USA. Crustal elements (Al, Ca, Si, Ti) and light-Lanthanides (La, Ce, Sm, Nd) were used to separate crustal PM whereas K was used to isolate biomass burning. The anthropogenic local PM was isolated by analyzing tracers for each source type- Traffic (PGEs, Sb, Cd, Pb, As, Cu); Refineries (La, Ce, Sm), Oil combustion (V). Biomass burning from Mexican agricultural burning dominated in Spring (late March-April) while Saharan dust was observed to be a dominant source during summer months (May – Aug). Satellite images NAAPS aerosol models and HYSPLIT back trajectories helped us in identifying regional inter-continental dust and regional smoke transport. Local PM consistently contributed to the PM mass fraction throughout the year PM. While regionally transported biomass burning PM were contributed primarily to fine size (average PM_2.5/PM₁₀ = 0.82) global transported desert dust dominated to coarse size PM (PM_2.5/PM₁₀ = 0.43). Regional transport of biomass burning contributes to 4% (annual average 0.84 µg/m³) of PM­₁₀ and 7.2% (annual average 0.7 µg/m³) of PM_2.5 while the inter-continental crustal dust transport annually contributes to 15% (annual average 2.91 µg/m³) of PM­₁₀ and 13% (annual average 1.26 µg/m³) of PM_2.5.