2. As noted above, it is assumed that the compounds of

concern are (NH ) SO and NH NO and primary fine 4 2 4 4 3

particulate. Therefore the mass concentrations of SO and =

4

NO must be corrected for the presence of NH . (The +

3 4

primary fine particulate is modeled as SO , as a surrogate =

4

in MESOPUFF-II; this should not be corrected for NH .) 4

+

a. Multiply the mass concentration of SO by 1.375 to =

4

obtain (NH ) SO 4 2 4

bext.s

0.003[part]f(RH)

where

bext.s

The extinction coefficient due to particle scattering (km 1)

0.003 a nominal dry scattering efficiency

[part] The concentration of (NH4)2SO4 or NH4NO3 in μg/m 3

or of primary particulate expressed as SO



4 (μg/m 3)

f(RH) The RH correction factor (see figure B1)

B-3

b. Multiply the mass concentration of NO by 1.29 to 

3

obtain NH NO 1. Obtain the hourly values of 4 3

relative humidity, appropriate

for each receptor and

corresponding to the hourly

concentrations calculated in step

1.

c. These can be obtained from the MESOPUFF-II

meteorological files.

d. If hourly relative humidity values are not available,

assume that the relative humidity is 95%.

e. Obtain the relative humidity correction factor

3. Calculate the extinction based on the following equation.

n1301 - n1302 - n1303 - n1304 - n1305 - n1306 - n1307 - n1308 - n1309 - n1310 - n1311 - n1312 - n1313 - n1314 - n1315 - n1316 - n1317 - n1318 - n1319 - n1320 - n1321 - n1322 - n1323 - n1324 - n1325 - n1326 - n1327 - n1328 - n1329 - n1330 - n1331 - n1332 - n1333 - n1334 - n1335 - n1336 - n1337 - n1338 - n1339 - n1340 - n1341 - n1342 - n1343 - n1344 - n1345 - n1346 - n13247 - n1348 - n1349 - n1350

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