Environmental Engineering Reference
In-Depth Information
1-h max: Sensitivity at time of maximal hourly ozone for each cell and day.
8-h max: Sensitivity averaged over 8-h interval with maximal ozone. This metric
was evaluated for cells exceeding 75 or 85 ppb ozone thresholds (corresponding to
new and old US ozone standards), or for all cells (no threshold).
24-h: Sensitivity averaged over entire day.
3. Results
The sensitivity of ozone to emissions from various source regions and categories
was evaluated on a variety of temporal metrics on a ppt/ton-per-day basis to
enable comparison between sources of different sizes (Table 1) . Within each of
the no-threshold temporal metrics, the per-ton impacts of all of the regional NO x
sources are similar. NO x from the power plant has a slightly smaller per-ton
impact, likely reflecting that the altitude and intensity of its plume inhibits ground-
level ozone formation. The densely vegetated southeastern U.S. experiences high
biogenic VOC emissions, so sensitivities to anthropogenic VOCs are minimal.
Table 1. Sensitivity of ground-level ozone to emissions (ppt/tpd), averaged over the episode for
all cells exceeding the ozone threshold. The population-weighted metric (ppm-persons/tpd)
integrates over population of each cell
Emissions
(t/day
(tpd))
8-h
(O 3
85 ppb)
8-h
(O 3 75
ppb)
1-h
(all)
8-h
(all)
24-h
(all)
Average # of gridcells
9,310
9,310
83
520
9,310
Sensitivity of ozone (ppt/tpd) to
Atlanta all NOx a
346
2.10
1.91
8.57
5.35
1.08
Atlanta mobile NOx
206
2.16
1.98
8.59
5.48
1.14
Atlanta point NOx a
10
2.15
1.89
8.26
5.23
1.08
Macon all NOx a
52
1.84
1.79
1.38
2.43
1.23
Plant Scherer NOx
46
1.56
1.37
1.26
2.46
0.94
Atlanta all VOC a
467
−0.08 −0.08
−0.01
−0.14
−0.05
Population-weighted impact (ppm-persons/tpd)
Atlanta all NOx a
346
159
138
34
61
33
Atlanta mobile NOx
206
163
145
35
62
41
Atlanta point NOx a
10
143
124
29
55
46
Macon all NOx a
52
84
74
3
14
55
Plant Scherer NOx
46
99
70
3
16
52
Atlanta all VOC a
467
−1
−1
1
1
−1
a Excluding power plant and biogenic emissions
 
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