Spatial distribution of persistent components of particulate matter near a hazardous waste thermal treatment facility

Open burn/open detonation (OB/OD) of hazardous waste poses serious environmental and public health risks. This community-engaged research study presents the first year-long, spatially resolved assessment of ambient air pollutant composition in Colfax, Louisiana - home to the last commercially operated OB/OD facility in the United States and situated in a rural and historically overburdened community. Until its permit changes took effect in December 2023, the facility processed military waste, fireworks, propellants, Superfund site soils, and other hazardous materials through OB/OD. These operations have long raised concerns among residents about air quality and associated health risks. To characterize pollutant distributions, we deployed two types of passive samplers and low-cost PurpleAir sensors to monitor PM_2.5, environmentally persistent free radicals (EPFRs), and heavy metals at ten sites across four seasonal quarters from March 2022 through March 2023. Distinct PM_2.5 hotspots were observed near the facility, particularly during March to June and December to March. EPFRs exhibited the strongest spatial correlation with PM_2.5 from June to September. During September to December, elevated EPFR levels coincided with high concentrations of Cr and Ni. Al and Fe were the most abundant metals detected, with sites 6.3 and 6.7 km from the facility consistently showing elevated levels of Al, Ba, Fe, Mg, Mn, and EPFRs. Strong correlations were consistently observed among Al, Ba, Mg, and Mn throughout the year. These findings provide critical insight into the spatial and temporal behavior of airborne pollutants near OB/OD operations and highlight the effectiveness of passive sampling in complex, resource-limited field conditions.