Source Apportionment of Fine Particulate Matter near Houston: Implications for Emission Sources and Back Trajectory Analysis

Abstract:

Measurements of fine particulate matter (PM_2.5) between December 2015 and December 2017 were conducted at a suburban site northeast of the Houston metropolitan area, TX. Chemical speciation of 233 filters were analyzed to investigate which factors affect the samples of PM_2.5. The components of total samples of measurements were identified and they showed 38.1% inorganic ions, 38.1% inorganic ions, 28.9% elements, 29.1% organic carbon, and 3.7% elemental carbon and other organic materials. Two years of measurements were then analyzed using Positive Matrix Factorization (PMF) receptor model. Eight factors were identified, including three main sources related to regional aerosols, biomass burning, and gasoline combustion which contributed more than 70% of total mass. The other factors include industry, crustal material, incineration, marine dust, and fireworks. Temporal analysis revealed receptor modeling captured and classified the impact of firework as one of individual sources of PM_2.5 over Houston. Back trajectory analysis of the species of PM_2.5 showed they were originated from the Gulf of Mexico, the Southeast, two areas of midwestern clusters, the Pacific Northwest, and the Southwest. Further analysis of measurements showed marine and crustal sources were associated with the onshore flow from Gulf of Mexico during the summer time. Also four clusters covering 38% of the trajectories were influenced by origins of biomass burning. The examination of organic carbon and elemental carbon indicated that Houston’s carbonaceous aerosols are highly influenced by secondary processes. The quantified contributions of these sources would help policymakers of metropolitan areas with real-world applicable knowledge for developing more efficient control systems and effective decisions to cope with harmful effects of ambient atmospheric pollutants to public life.