Long-term source apportionment of PM2.5 across the contiguous United States (2000-2019) using a multilinear engine model.

Identifying PM 2.5 sources is crucial for effective air quality management and public health. This research used the Multilinear Engine (ME-2) model to analyze PM 2.5 from 515 EPA Chemical Speciation Network (CSN) and Interagency Monitoring of Protected Visual Environments (IMPROVE) sites across the U.S. from 2000 to 2019. The U.S. was divided into nine regions for detailed analysis. A total of seven source types (tracers) were resolved across the country: (1) Soil/Dust (Si, Al, Ca and Fe); (2) Vehicle emissions (EC, OC, Cu and Zn); (3) Biomass/wood burning (K); (4) Heavy oil/coal combustion (Ni, V, Cl and As); (5) Secondary sulfate (SO 4 2-); (6) Secondary nitrate (NO 3 -) and (7) Sea salt (Mg, Na, Cl and SO 4 2-). Furthermore, we extracted and calculated secondary organic aerosols (SOA) based on the secondary sulfate and nitrate factors. Notably, significant reductions in secondary sulfate, nitrate, and heavy oil/coal combustion emissions reflect recent cuts in fossil-fueled power sector emissions. A decline in SOA suggests effective mitigation of their formation conditions or precursors. Despite these improvements, vehicle emissions and biomass burning show no significant decrease, highlighting the need for focused control on these persistent pollution sources for future air quality management. [Display omitted] • A 20-year study identifies key PM 2.5 pollution sources across the U.S. using an advanced Multilinear Engine (ME-2) model. • Substantial emission reductions achieved in the fossil fuel sector indicate the effectiveness of pollution control measures. • No significant decrease in vehicle emissions and biomass burning highlights the need for focused pollution management. • Future efforts aim to link emission sources with health outcomes, enhancing air quality management policies. [ABSTRACT FROM AUTHOR]