47In the CAIR analysis, the DON was assumed to stay constant through time due to the
uncertainty in the ammonium measurements. The water calculation is sensitive to the ammonium (and
therefore the DON value) concentrations. Keeping the DON constant allows for the future year
ammonium and water values to be solely a function of the change in sulfate and nitrate concentrations.
Otherwise, the water concentration can go up when the sulfate and nitrate concentrations go down. This
may occur if sulfate becomes more neutralized in the future. It is a somewhat illogical outcome (although
scientifically possible) and is highly dependent on an uncertain measurement (ammonium). Therefore,
use of a constant DON creates a more stable set of calculations. If the measured and modeled ammonium
concentrations are believed to be accurate and respond in a reasonable way to emissions controls, then it
would be more scientifically credible to use the model predicted change in ammonium. Otherwise, it is a
reasonable assumption to keep the DON constant over time.
AmmoniumFuture= 0.336 * 6.69 + 0.29 * 0.93 = 2.52 ug/m3
The NH4future, SO4future, and NO3future concentrations can then be input into an equilibrium
model (AIM or another alternative model) or through a polynomial equation to predict future
year particle bound water concentration.
(9) The future species concentrations at each FRM site are then summed over the seven species
plus blank mass to estimate the future quarterly average PM2.5 concentration.
In the example above, the total PM2.5Future=
6.69 + 0.93 + 4.53 + 0.75 + 0.66 + 2.52 + 1.73 + 0.5 = 18.31 ug/m3
(assuming that the future year water concentration is equal to 1.73 ug/m3)
(10) The same calculations are completed for the other 3 quarters to get a future year PM2.5
concentration for each quarter. The 4 quarters are then averaged to get a final future year annual
average PM2.5 concentration for each FRM site.
(11) The future year annual average concentration is compared to 15.0 ug/m348.
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castellano: DISPER CUSTIC DESCAR RADIA italiano:
deutsch: DIS CUS DES RAD
castellano: DIS CUS DES RAD english: DIS CUS DES RAD
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