Fig. 2: Contiguous U.S. county-level average predicted concentration of PM2.5 and its major components (bars) for 2016 (nā=ā2708 counties).
From: Secondary organic aerosol association with cardiorespiratory disease mortality in the United States

Major components include organic aerosol (OA), a calcium-iron-silicon-aluminum rich aerosol (dust), sulfate (SO4), ammonium and nitrate (NH4NO3), an elemental carbon and potassium rich aerosol (soot), and a chloride-sodium-magnesium rich aerosol (sea spray). Inset in red are the subcomponents of OA: SOA from anthropogenic VOCs (SOAAVOC), SOA from biogenic VOCs (SOABVOC), and primary organic aerosol (POA). Error bars represent ±1 IQR variation in the pollutant from the county-level average. Points represent population-weighted concentrations.