Methodology for the Annual PM2.5 NAAQS

The suggested steps outlined below assume that the attainment test has been performed using the

photochemical modeling and that the annual DV has been computed as discussed in Section 5.1.

(1) Identify local primary PM2.5 sources that are thought to be are contributing to the monitor

and causing non-attainment of the annual NAAQS.

(2) By quarter, identify at the monitor, primary versus secondary components of


(3) Identify the percentage of total primary PM2.5 at the monitor due to the local sources

identified in (1). Convert the percentage to an estimated concentration in ug/m3

(4) Model with a dispersion model the current and future concentrations of these

local sources using actual emissions.

-Place receptors at and near the monitor location(s)58.

-The receptor spacing should be fine enough to get an accurate picture of the

concentration at the monitor.

-Model the base year and future annual average

-For both base and future year use the same 1 year of met data – the

same year as used for the photochemical modeling (if available, use more than 1 year of

met data).

(5) From the modeling in (4), calculate quarterly RRFs59 for total

primary PM2.5 modeled for the selected sources (using concentration values

at receptors at monitors).

(6) Multiply the primary PM2.5 identified in (3) by the RRFs from (5).

(7) Subtract the result in (6) from the primary PM2.5 identified in (3)

(8) For each quarter, subtract the amount in (7) from the future year quarterly DV provided by

the photochemical modeling.

(9) Average the four quarters to get an annual average DV.


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