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Step 1: Actual worst-day average nitrate, sulfate,chloride, and PM10 ambient air <br /> measurements are used to partially speciate the PM1o. Missing data are filled in by <br /> appropriate gap-filling. In this case,the highest PM10 day in 2007 was used. <br /> Step 2: The unspeciated balance of PM10 (after subtracting the ammonium sulfate, <br /> ammonium nitrate,and ammonium chloride from the total PM1o) is split between direct- <br /> combustion-related PM10 (fuel combustion and mobile sources) and other direct PM10 <br /> sources. The contribution from direct-combustion can be based on Chemical Mass <br /> Balance (CMB) modeling performed for a District's PM10 Attainment Demonstration Plan, <br /> if available. <br /> Step 3: The regions direct-combustion emissions are obtained from the regional emission <br /> inventory. In this case, the winter inventory for planning year 2007 was used. <br /> Step 4: The peak daily average PM10 concentration due to direct-combustion sources and <br /> the peak daily average sulfate concentration for calendar year 2007 are adjusted <br /> (downward) to account for the contribution due to pollution transport. Because the goal <br /> is to determine what effect local sources have on regional PM10 concentrations,the impact <br /> from outside sources must be excluded. In this case,the region is assumed to be upwind <br /> of the other districts. No adjustments were made for transport of SO2 or PM10 for this <br /> analysis. <br /> Step 5: The direct PM10 impact (in units of pg/m3 per ton/day) from local combustion <br /> sources is calculated by dividing the adjusted direct-combustion-related PM10 <br /> concentration by the direct-combustion regional PM10 emissions. The secondary impact <br /> from SO2 emissions is calculated by dividing the adjusted sulfate concentration by all <br /> regional SO2 emissions. <br /> Step 6: The SO2 to PM10 ratio is determined by dividing the SO2 impact by the direct PM10 <br /> impact. <br />