What are the parts of particulate matter, and how do they relate?

Primary PM2.5 estimates are speciated into the five PM species in the NEI: elemental (black) carbon (EC), organic carbon (OC), nitrate (NO3), sulfate (SO4), and the remainder of PM25-PRI (PMFINE). Diesel engine PM25-PRI and PM10 emissions are also labeled as DIESEL-PM25 and DIESEL-PM10 for mobile source diesel engines.  For all diesel engine sources, PM25-PRI = DIESEL-PM25 and PM10-PRI = DIESEL-PM10.  For PM2.5 species, PM25-PRI = EC + OC + SO4 + NO3 + PMFINE.

PM components such as filterable PM25-FIL and PM10-FIL and condensable PM (PM-CON) are different components of PM25-PRI and should not be confused with PM speciation.  For combustion-related sources, PM25-PRI = PM25-FIL + PM-CON and PM10-PRI = PM10-FIL + PM-CON. For non-combustion sources of PM, PM-CON is zero, and therefore primary PM will be equal to the filterable components (e.g., PM25-PRI = PM25-FIL). Note that there is no size differentiation when considering PM-CON, since nearly all PM-CON is under 2.5 microns in diameter.