11.1.2 Annual PM2.5 NAAQS

1. Is the nonattainment problem primarily a local one, or are regional factors important?

(Surface measurements suggest that only design values in or immediately downwind

of the city violate the NAAQS. However, other nearby design values come close to the

concentration specified in the NAAQS)

2. What is the relative importance of measured primary and secondary components of PM2.5

measured at sites violating the NAAQS?


(Secondary components (i.e., SO4, NO3, OC) constitute about 80% of the measured

mass of PM2.5 . There are higher concentrations of primary PM2.5 in the core urban area

compared to the suburbs and more rural areas.)

3. What are the most prevalent components of measured PM2.5?

(The most important components in ranked order are mass associated with SO4, OC

and other primary particulate matter).

4. Does the measured mix of PM components appear to roughly agree with mix of emission

categories surrounding the monitoring sites?

(No. Relative importance of measured other primary PM2.5 (OPP) appears less than

what might be inferred from the inventory).

5. Do there appear to be any areas with large gradients of primary PM2.5 in monitored or

unmonitored areas?

(Cannot really tell for sources of primary PM2.5 material until we resolve the

preceding inventory/monitoring discrepancy. There are no other obvious major sources of

primary particulate matter).

6. Is there any indication of what precursor might be limiting formation of secondary

particulate matter?

(No indicator species analyses have been performed. Past analyses performed for

ozone-related SIP revisions suggest that ozone in this area may be limited by availability of


7. Do monitored violations occur at locations subject to mesoscale


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