Characterizing Spatio-Temporal Variability and Sources of Particle-Bound Metals through Fixed-Site and Mobile Monitoring in Two Communities in the South Coast Air Basin

PROVAT SAHA, Christopher Lim, Mohammad Sowlat, Steven Boddeker, Julia Montoya-Aguilera, Zihan Zhu, Sina Hasheminassab, Payam Pakbin, Andrea Polidori, Jason Low, South Coast Air Quality Management District

     Abstract Number: 456
     Working Group: Source Apportionment

Abstract
To improve understanding of the spatio-temporal variability and sources of particulate metals at the community scale, comprehensive measurements were conducted using a combination of fixed-site and mobile monitoring in two communities in the Los Angeles area—East Los Angeles, Boyle Heights, West Commerce (ELABHWC), and Southeast Los Angeles (SELA)—which are disproportionately impacted by localized air pollution sources. ELABHWC and SELA were designated by California Air Resources Board (CARB) to be part of Assembly Bill (AB) 617, a state-wide program established to reduce impact of air pollution in disproportionately impacted communities. Measurements included PM₁₀ particle-bound trace metals and elements at two fixed sites (one in each community) over a multi-year continuous monitoring period, along with year-long mobile monitoring surveys using a multi-metal mobile platform (MMMP) to capture hyper-local spatial variability. Source apportionment analysis using the Positive Matrix Factorization (PMF) technique was applied to both stationary and mobile datasets. A five-factor solution was found to be the most interpretable for both mobile and fixed-site data. Both monitoring approaches consistently identified the same general source groups—industry, road dust, and soil dust—as dominant contributors to particle-bound trace metals in these communities. Additionally, two distinct factors, one with high sulfur and another with high chlorine, were identified in both mobile and fixed sites datasets. The derived factors from mobile monitoring data show strong concentration gradients, especially for road dust and industrial factors, and spatial variability of these factors concentrations correlates with relevant source-activity related land use variables such as road density and the density of metal industries. This presentation will provide a comprehensive summary of the source apportionment results and show how information obtained in this study has prompted plans to perform full PM speciation at two near-road sites as part of South Coast AQMD’s Multiple Air Toxics Exposure Study (MATES VI).