AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Indoor/Outdoor Relationships and Anthropogenic Elemental Signatures in Airborne PM2.5 at a High School: Impacts of Petroleum Refining Emissions on Lanthanoid Enrichment
SHANKAR CHELLAM, Ayse Bozlaker, Jordan Peccia, Texas A&M University
Abstract Number: 15 Working Group: Indoor Aerosols
Abstract Airborne fine particulate matter, particularly metal-enrichment, is an important concern in schools located in industrialized regions. In many such cases, anthropogenic metal emissions to the ambient outdoor atmosphere can transport indoors and negatively impact children's health. In this work, outdoor emissions of primary fine particles and their contributions to indoor air quality deterioration were examined by collecting PM2.5 paired indoor and outdoor PM2.5 from a mechanically ventilated high school in the ultra-industrialized ship channel region of Houston, TX over a two-month span. Samples were comprehensively analyzed for a total of 47 elements including lanthanoids (rare earth elements), transition metals and representative elements using inductively coupled plasma-mass spectrometry. To our knowledge, this is the first work to comprehensively measure the concentrations of all 14 lanthanoids in PM2.5 inside a United States school and relate it to outdoor anthropogenic contamination. This approach allowed us to capture indoor signatures of outdoor episodic emissions arising from non-routine operations of petroleum refinery fluidized-bed catalytic cracking units. Average indoor-to-outdoor (I/O) abundance ratios for the majority of elements were close to unity providing evidence that indoor metal-bearing PM2.5 had predominantly outdoor origins. Only Co had an I/O abundance ratio > 1 but its indoor sources could not be explicitly identified. La and 17 other elements (Na, K, V, Ni, Co, Cu, Zn, Ga, As, Se, Mo, Cd, Sn, Sb, Ba, W, and Pb), including air toxics were enriched relative to the local soil both in indoor and outdoor PM2.5 demonstrating their anthropogenic origins. Several lines of evidence including receptor modeling (chemical mass balancing), lanthanoid ratios, and La-Ce-Sm ternary diagrams pointed to petroleum refineries as being largely responsible for enhanced La and total lanthanoid concentrations in the majority of paired indoor and outdoor PM2.5.