Evaluating the Trends in Sources of Ambient Particle-Bound Metals in the Environmental Justice Community of Paramount, CA, during Pre- and Post-COVID-19 Lockdown Periods

MOHAMMAD SOWLAT, Sina Hasheminassab, Bill Grant, Payam Pakbin, Jason Low, Andrea Polidori, South Coast Air Quality Management District

     Abstract Number: 126
     Working Group: Source Apportionment

Abstract
In this study, we evaluated the long-term trends in composition and sources of particulate metals in the environmental justice (EJ) community of Paramount, California. In this community, several known sources of particulate metals are in close proximity to sensitive receptors, increasing the level of exposure to these pollutants, many of which are known toxic air contaminants (TACs). The literature suggests that there are disproportionate changes in air quality due to COVID-19 lockdowns in EJ and non-EJ communities; therefore, in this work we paid particular attention to the trends pre- and post-COVID-19 lockdown. We used a Xact 625 ambient metal monitor to measure the concentrations of metals in total suspended particulates (TSP) between May 2017 and December 2020. We used the USEPA’s Positive Matrix Factorization (PMF) model to apportion the sources of ambient particulate metals. The PMF analysis identified 5 factors that were associated with 3 major sources: traffic, industry, and soil dust. Traffic and soil dust contributions exhibited significant reductions after the stay-at-home order; this is believed to have been caused by decreased human activities. However, as the lockdown measures were lifted, the contributions of these sources gradually reverted to pre-lockdown levels. On the other hand, contributions of industrial factors dropped significantly during the stay-at-home order (due to the combined effect of reduced demand, production, and revenues during the pandemic) and remained low throughout the rest of 2020. We note that the contribution of industrial-related sources declined even before the COVID-19 lockdown, likely due to the impact of imposed tariffs and reduced demand for steel and aluminum parts, and partly to the regulatory actions by the South Coast Air Quality Management District in this community. Altogether, these actions and events have led to substantial reductions in the levels of particulate metals emitted from industrial sources in the EJ community of Paramount, with reductions as high as 80% depending on the specific metal and the pertinent source.