Step 3. Using model results, derive component-specific relative response factors (RRF) at
each monitor for each quarter.
For each quarter, apply an air quality model to estimate current and future concentrations for
each of the components of PM2.5. Take the ratio of future to current predictions for each
component on the modeled days with PM2.5 > 65 ug/3 or the high end of the distribution of
modeled days. The result is a component-specific relative response factor (RRF). (e.g., given
model predicted base year nitrate of 20.0 ug/m3 and future year concentration of 15.0 ug/m3, then
RRF for nitrate is 0.750).
The relative response factor for component j at a site i is given by the following expression:
(RRF)ij = ([Cj, projected]/[Cj, current])i
where Cj, current is the mean concentration (for the high modeled days for each quarter)
predicted at or near the monitoring site with emissions characteristic of the period used to
calculate the baseline design value for 24-hour PM2.5.
Cj, projected is the future year mean concentration (for the high modeled days for each
quarter) predicted at or near the monitoring site with emissions characteristic of the
future year period.
Step 4. Apply the component specific RRFs to observed air quality to obtain projected
quarterly species estimates.
For each quarter, multiply the quarterly component concentration (step 2) times the componentspecific
RRF obtained in step 3. This leads to an estimated future quarterly concentration for
each component. (e.g., 21.00 ug/m3 nitrate x 0.750 = future nitrate of 15.75 ug/m3).
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castellano: DISPER CUSTIC DESCAR RADIA italiano:
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castellano: DIS CUS DES RAD english: DIS CUS DES RAD
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