charlotte-rock hill-gastonia msa summertime ozone formation photos from 2001 mecklenburg country...
TRANSCRIPT
Charlotte-Rock Hill-Gastonia MSA Summertime Ozone Formation
Photos from 2001 Mecklenburg Country State of the Environment Report
2
Arizona’s Valley of the Sun “Brown Cloud”
• Observed since early 1990’s; contains C Particles and NO2
(brown) gas
• From burning fossil fuels: cars, construction equipment, power plants, lawn mowers, leaf blowers contribute to this brown cloud
• Weather also a key factor
Phoenix photo from http://phoenix.about.com/library/weekly/uc051601a.htm, accessed Mar 2004
3Image take from http://www.al.noaa.gov/WWWHD/Pubdocs/TropoRural.html, accessed Mar 2004
4
Presence of NO2 (brown gas) results in inevitable formation of ozone
NO2 (brown) + sunlite NO• + O•
O• + O2 O3 (Ozone)
•Control measures to effectively address ground-level ozone must focus on minimizing NO2 formation
5
Ozone precursorsNitrogen Oxides
•Dry Air is 78% Nitrogen (N2), 21% Oxygen (O2)
•Heating air to high temperatures forms NO• (motor vehicles, fossil-fuel power plants, lightning)
• NO• is an ozone precursor and also reacts directly with ozone to destroy it
Volatile Organic Compounds (VOC’s)•VOC’s continuously emitted by fuel spills, motor vehicles, trees, air fresheners, paints, and countless other sources
•OH• hydroxyl radical is the atmosphere’s “natural detergent” that cleans VOC’s from the air by initiating the process that converts them into carbon dioxide and water
6
Volatile Organic Compound (VOC) RemovalAir’s natural VOC cleanser produced from ozone and
water
•Ozone (O3) + UV-B -> O2+ *O•
*O• + H2O 2OH•
•OH• works by transforming stable VOC molecules (R-H) into reactive radicals (R•)
OH• + R-H R• + H2O
•Reactive organic radicals immediately combine with oxygen to form peroxide radicals
R• + O2 (R-O-O•)
7
Formation of Nitrogen Dioxide
NO• + R-O-O• NO2• + RO•
Formation of NO2 (and O3) driven primarily by:
•Concentration of VOC’s (near emission sources)
•Concentration of NO• (rural & downwind areas)
•Concentrations of both NO• and VOC’s
***Summertime ozone pollution results from an overload in our air of NO•, VOC’s, or both
8
NO and VOC Effects on Ozone Production
NO•
Sensitive
Region
VOC
Sensitive
Region
Both NO• + VOC Sensitive
Both NO• + VOC Sensitive
Figure from : http://www-personal.engin.umich.edu/~sillman/ozone.htm, accessed Mar 2004
9
’95-’99 AM NMOC/NOy Ratios for the Plaza Monitoring Site
0
5
10
15
20
1994 1995 1996 1997 1998 1999 2000
NM
OC
/NO
y
NOx Limited
VOC Limited
From Perry, JL and Owens, PM, “Weekday/Weekend Variability and Long-Term Trends in Traffic, CO,
NOy, and Ozone for the Charlotte Metropolitan Area during the 1990's, AWMA, June 2001
10
I-77 Traffic Volume vs. Time of Day
0
1000
2000
3000
4000
5000
Time of Day (Hour)
Ho
url
y V
olu
me
Sun Mon Tues Wed
Thu Fri Sat
From Perry and Owens, AWMA, 2001
11
5
10
15
20
25
30
35
40
1 3 5 7 9 11 13 15 17 19 21 23
Time of Day
Avg
Ho
url
y N
O y
Co
nce
ntr
atio
n (
pp
b)
Sunday Monday Tuesday Wednesday
Thursday Friday Saturday
May-Sep ‘95-‘98 Plaza Average Hourly NOy
From Perry and Owens, AWMA, 2001
12
1990-1998 May-Sep Diurnal Charlotte Ozone Averages
By Day of Week (weekend days-lines, weekdays-markers County Line
0
0. 01
0. 02
0. 03
0. 04
0. 05
0. 06
0. 07
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2122 23
Arrowwood
0
0. 01
0. 02
0. 03
0. 04
0. 05
0. 06
0. 07
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2122 23
Plaza
0
0. 01
0. 02
0. 03
0. 04
0. 05
0. 06
0. 07
1 2 3 4 5 6 7 8 9 10 11 12 13 1415 16 17 18 19 2021 22 23
From Perry and Owens, AWMA, 2001
13Obtained from John White, NC DAQ
14From: http://www.epa.gov/airnow/showmaps.html?/airnow/2000/20000601/8p-ncsc.gif, accessed Mar 2004
15From: http://www.epa.gov/airnow/showmaps.html?/airnow/2000/20000601/8p-ncsc.gif, accessed Mar 2004