2. Sources where two or more stacks are present at the same location were combined into

a single source with emissions equal to the sum of the individual emissions, exit

velocity equal to the average of the individual exit velocities, and stack diameters

adjusted to give the appropriate total combined mass fluxes.

3. All information provided in English units were converted to metric units. Also, UTM

coordinates provided in zone 18 were assigned zone 17 equivalents by first converting

them to latitude-longitude and then converting back to UTM.

4. Small sources, with emissions of both SO and NO less than 5 g/s, were excluded. 2 x

The resulting set of 27 sources is shown in Table 3-1; their locations are displayed in Figure

3-3 (indicated by crosses). Several issues arose during the processing of these sources. These

issues, and our approach in resolving them, are described below:

1. Some emission totals were provided as both short-term and annual rates. In these

cases, the short-term rates were used, since the model was to be used primarily to

determine the highest short-term impacts. The resulting annual average impacts will

overestimate the true annual average impacts.

2. There were some differences between the emission totals reported by Maryland and

Virginia for several Maryland sources. In case of differences, the higher total was

used.

3. In two cases, emission offsets were reported as negative emissions. Negative

emissions cannot be input into MESOPUFF II. In one case, where the offset occurred

at the same location as actual emissions, the offset was subtracted from the total

emissions. In the other case, the offset was at a different location. This offset cannot

be modeled in a single model run.

4. MESOPUFF II allows emissions of primary sulfate. The sulfur emissions data

provided were in terms of SO and did not specify emission levels of primary sulfate. 2

For most fuel burning sources, primary sulfate emissions are roughly equal to 3

percent of SO emissions (Cass, 1980). Therefore, for purposes of this demonstration, 2

primary sulfate emissions of 3 percent (as sulfur) of the SO emissions were included 2

in the MESOPUFF II input file. Accounting for the difference in molecular weight

between sulfate (SO ) and SO , the SO emission rates were multiplied by 0.045 to 4 2 2

=

obtain the sulfate emission rates.

This set of 27 sources was presented to IWAQM as the set of sources to be modeled in the

demonstration application. However, attempts to model these 27 sources with MESOPUFF II

for the first month, January 1988, were unsuccessful. On an 386/25 MHz PC, 16 hours were

required to process the first 76 hours of the simulation. Hour 77 consumed 38 CPU minutes

alone. Although these CPU times would be reduced somewhat on the 486/50 MHz PC that

was planned for use in the demonstration application, it would clearly be impossible to

complete a full 60 months of MESOPUFF

 

 

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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