Comments on the Final Report for the OTAQ AQA Workgroup

Recommend additional analysis on model predicted background

EPA and other documents state that the background concentratins of ozone are 30 to 40 ppb. However, review of data for National Parks reveals concentrations of 70 + ppb and UAM IV model runs for Houston indicate 68 ppb as the predicted ozone level when all anthropogenic emissions are removed.

Suggest a model run with "0" anthropogenic emissions to determine predicted " background" levels of ozone for both the 1 hr and 8 hr standards.

Submitted by John Dege on 5/19/97 RecID: JohnDege11

Vol 2 misstates the daily background maximums

The correct Spatial and Temporal Pattern of ozone in OTAG is
illustrated by the following data; Vol 2 misstates the daily
maximums as 30-40 ppb when they are really 65 to 75 ppb:
from AS&L Associates Internet Web Site

(Data courtesy of National Park Service)

Top 8-Hr Daily Maximums
Top 10 8-hour daily maximum values for sites experiencing low maximum hourly
average concentrations with data capture greater than or equal to 75%. All
concentrations are in ppm units

Location Site/AIRS ID

Year 1 2 3 4 5 6 7 8 9 10

Redwood CA NP 060150002

1988 0.061 0.058 0.053 0.052 0.048 0.047 0.046 0.046 0.045 0.045
1989 0.044 0.043 0.043 0.043 0.042 0.042 0.042 0.042 0.041 0.041
1990 0.051 0.047 0.047 0.046 0.044 0.043 0.043 0.043 0.043 0.042
1991 0.048 0.046 0.046 0.045 0.045 0.044 0.044 0.043 0.043 0.043
1992 0.060 0.053 0.045 0.045 0.045 0.044 0.044 0.043 0.043 0.043
1993 0.049 0.046 0.043 0.043 0.043 0.042 0.042 0.042 0.041 0.041
1994 0.048 0.048 0.046 0.045 0.044 0.044 0.043 0.043 0.043 0.042

Olympic,WA NP 530090012
1989 0.054 0.052 0.047 0.044 0.044 0.044 0.042 0.042 0.038 0.038
1990 0.055 0.048 0.046 0.046 0.043 0.040 0.040 0.038 0.038 0.038
1991 0.050 0.048 0.045 0.043 0.042 0.041 0.041 0.041 0.041 0.041
1993 0.055 0.052 0.044 0.042 0.040 0.039 0.038 0.038 0.037 0.036
1994 0.046 0.042 0.042 0.042 0.041 0.041 0.040 0.040 0.040 0.040
1995 0.064 0.063 0.050 0.049 0.045 0.045 0.044 0.044 0.044 0.044
1990 0.047 0.047 0.046 0.046 0.043 0.042 0.042 0.041 0.041 0.041
Glacier NP,MT 300298001
1989 0.062 0.061 0.060 0.058 0.057 0.056 0.056 0.056 0.056 0.056
1990 0.058 0.057 0.055 0.054 0.053 0.053 0.052 0.052 0.052 0.052
1991 0.060 0.057 0.057 0.057 0.056 0.055 0.055 0.054 0.054 0.053
1992 0.062 0.056 0.055 0.054 0.054 0.054 0.053 0.053 0.053 0.052
1995 0.061 0.055 0.052 0.052 0.052 0.052 0.051 0.050 0.050 0.049
1996 0.060 0.059 0.058 0.058 0.057 0.057 0.057 0.056 0.056 0.056

Yellowstone NP,WY 560391010
1988 0.069 0.068 0.068 0.067 0.066 0.066 0.066 0.065 0.064 0.061
1989 0.067 0.066 0.065 0.063 0.063 0.062 0.062 0.062 0.061 0.061
1990 0.058 0.056 0.054 0.054 0.054 0.052 0.050 0.050 0.050 0.049
1991 0.059 0.059 0.058 0.057 0.056 0.056 0.056 0.056 0.055 0.055
1992 0.067 0.065 0.064 0.064 0.064 0.062 0.062 0.060 0.059 0.058
1993 0.057 0.055 0.055 0.054 0.054 0.053 0.053 0.053 0.053 0.053
1994 0.067 0.063 0.063 0.062 0.062 0.061 0.061 0.059 0.059 0.059
1995 0.065 0.062 0.061 0.060 0.060 0.059 0.059 0.059 0.059 0.058
Denali NP,Alaska 022900003
1988 0.055 0.054 0.054 0.053 0.053 0.052 0.052 0.052 0.052 0.052
1990 0.049 0.048 0.048 0.048 0.048 0.047 0.046 0.046 0.046 0.046
1991 0.054 0.054 0.050 0.050 0.046 0.046 0.046 0.046 0.045 0.044
1992 0.053 0.052 0.052 0.051 0.050 0.050 0.049 0.049 0.049 0.049
1993 0.053 0.053 0.051 0.048 0.048 0.047 0.047 0.046 0.046 0.046
1994 0.052 0.051 0.049 0.049 0.049 0.048 0.048 0.048 0.048 0.048
1995 0.058 0.056 0.056 0.054 0.051 0.050 0.049 0.046 0.046 0.046
1996 0.058 0.054 0.054 0.053 0.053 0.053 0.052 0.052 0.052 0.051

Badlands NP,SD 460711001
1988 0.068 0.064 0.063 0.062 0.061 0.060 0.060 0.060 0.060 0.059
1989 0.069 0.066 0.064 0.063 0.060 0.059 0.057 0.057 0.057 0.056
1990 0.060 0.059 0.055 0.055 0.054 0.052 0.052 0.051 0.051 0.050
1991 0.058 0.058 0.056 0.056 0.056 0.055 0.055 0.054 0.054 0.054

Theod. Roos.NP,ND 380530002
1984 0.064 0.062 0.062 0.062 0.059 0.058 0.057 0.057 0.057 0.057
1985 0.058 0.055 0.055 0.054 0.054 0.054 0.053 0.053 0.053 0.052
1986 0.058 0.058 0.056 0.056 0.054 0.054 0.054 0.053 0.053 0.052
1989 0.072 0.069 0.066 0.065 0.065 0.064 0.064 0.063 0.063 0.063

Submitted by John Dege on 5/19/97 RecID: JohnDege10

Comments on Vol 1. - Pattern of Ozone on Edges of Region

In looking at some of the maps, shouldn't we flag the SW corner of the region as an additonal area that may have some ozone levels higher than what we are calling background due to precursors and ozone blowing in from Mexican sources just across the border. I realize that these sources cannot be controlled by the US due to their location. We flag a similar situation with the US - Canada border in the Windsor-Toronto corridor, maybe we should do something similar here. Any other thoughts on this concept?

Submitted by David Long on 5/16/97 RecID: DavidLong1

comments on the AQA results summary and Vol I ES

comments from Feldman on volume I ES and the results summary

1. "Trends" have been specifically identified in the tasks yet all trends information has been
omitted. Trends indicate dramatic improvement in 1-hr peak ozone in at least some regions of
the OTAG domain.

2. "highest values in large urban areas" should be "downwind".

3. In the paragraph re distance and direction of transport, the end of the sentence should read
"not clear to what extent this actually represents transport of ozone and/or precursors or is a
meteorological correlation."

4.In that same par please add something to the effect of " Met correlations have been shown to
have a greater geographic extent than ozone concentrations." This is from ST Rao's work.

5. I'm not sure what makes the OTAG domain a well-defined aq control region besides knowing
the name of the states involved. It may actually represent several aq control regions, i.e. south
vs. north.

6. Most of the excess ozone in the OTAG region is attributed to anthropogenic emissions. the
role of biogenics as a VOC precursor was presented and discussed in several efforts. Even if
the OTAG inventory overstates the emissions of biogenics, they still contribute considerably to
the precursors.

7. the sentence containing "...the center of the OTAG domain tends to impact on downwind
areas..." should be deleted. Would we expect them to impact upwind areas?

8.In the last sentence of the ES, drop the clause "such as that being undertaken through the
OTAG process". There is no evidence that the OTAG process has or will develop and commit to
continuous and measurable progress.

Submitted by Howard Feldman on 5/9/97 RecID: HowardFeldman

Re: comments on the AQA results summary and Vol I ES

1. Ozone trends. Yes, long-term ozone trends should be included

5. OTAG-well defined control domain?. If substantial man-made ozone would enter through domain boundaries (e.g. OTC), it would not be fully controllable. Perhaps �well defined� should be replaced by �controllable with measures within OTAG�. Suggestions anyone?

6. Is the excess ozone anthropo- and biogenic?. �Excess� is meant here as excess above biogenic where biogenic and tropospheric background is taken to mean the same. In the absence of man-made ozone, biogenic O3 over OTAG should be 30-40 ppb as over other biogenic-dominated background sites elsewhere. Incidentally, based on conversations with Ralph Morris, the UAM-V with BIES II, appears to generate well over 30-40 ppb avg. biogenic ozone over OTAG (when running with biogenic emissions only.) Eric Edgerton�s analysis suggests that the overproduction may be due to too much isoprene (in the emissions or slow kinetics?)

7. Downwind impact of the OTAG center. Yes it appears to be redundant.

Submitted by Rudolf Husar on 5/14/97 RecID: RudolfHusar

Vol. 1 draft: Model reliability Misstated.

Do air quality data support the use of UAM-V model use to evaluate control options?

YES, but general directiion only. UAM V model runs in Houston do not predict ground measurements within EPA specifications of +- 15%. UAM IV is barely able to predict ground level measurements within +- 15% for all monitoring stations on the Houston modeling regime.

In general, visual comparison of tile maps of measured ozone during modeled episodes with model-predicted ozone values shows that the simulations may capture the large-scale features of each episode, suggesting that UAM-V is adequate to evaluate future control options in some areas. The models underpredict at some locations and overpredict at others. . Further, aircraft measurements taken at selected locations for a few simulation days indicate that ozone levels above the surface layer of the atmosphere also are not accuratelly predicted by the model. Comparison of model predictions to ozone precursor data, while limited by the availability of measurements, shows generally poor agreement, especially for isoprene (from biogenic VOC emissions).One possible explanation is that isoprene reacts so quickly to from ozone in urban areas that it cannot be detected. Isoprene emissions cease during the night and increase dramatically during the day to peak emissions between 1200 and 1500 hrs. When sunlight intensity is at a maximum. This is consistent with observations in clean areas where ambient ozone is directly proportional to biogenic NO emissions.
Models can only be used for general directions for precursor controls, but cannot be presumed to more than +- 30 %(+- 30 ppb) accurate.
Ref: TX Houston Model runs by TNRCC

Submitted by John Dege on 5/8/97 RecID: JohnDege9

Re: Vol. 1 draft: Model reliability Misstated.

The model overprediction of isoprene apears to be substantial. Several 'stakeholder' presenters stressed that point and backed with analysis. Aren't the other model shorcomings expressed in the ES?

Submitted by Rudolf Husar on 5/15/97 RecID: RudolfHusar1

Re: Re: Vol. 1 draft: Model reliability Misstated.

yes. Model shortcomings are stated; was thinking of the methods used to determine biogenic emissions; bag studies were used to determine emissions(measured accumulated isoprene in bags) but the reports said researchers could not detect the isoprene in the ambient air. Agree that more research is needed. In the EPA Trends 95 report it states that the isoprene emissions predicted by BEIS2 model should be considered as possibly in error by 2 x.

Submitted by John Dege on 5/20/97 RecID: JohnDege12

Draft Vol. 1 Changes to

Do air quality data suggest high-leverage means for controlling ozone?

In urban areas where ozone is VOC limited, the primary control strategy should be on VOCs and specifically on those VOCs with hgh reactivity( that is, create more ozone than others). NOx reductions can actually increase ozone levels and increase the population exposure).
Based on spatial pattern, temporal pattern, and transport considerations, some general control approaches appear to have higher leverage. Geographically, the region located in the center of the OTAG domain tends to impact on downwind areas regardless of which direction the wind blows. In addition, trajectory residence-time analyses implicate the central portion of the OTAG domain as being involved in transport-related ozone events more than any other portion of the domain, so controls implemented in this area may be effective at reducing transport more often than controls anywhere else. Further, given the density of NOx-rich point sources in this portion of the domain and the observation that ozone formation appears to be NOx-limited in non-urban areas, it follows that NOx controls may be more effective in this regard. It should be noted that this suggestion is consistent with all regional modeling results to date.

Ref:
:Carter Reactivity :ftp://cert.ucr.edu/pub/carter/dmsrct.txt
:TX Houston UAM IV study

Submitted by John Dege on 5/8/97 RecID: JohnDege8

Re: Draft Vol. 1 Changes to

"NOx reductions can actually increase ozone levels and increase the population exposure".I presume you refer to the famous disbenefit thing popularized by M. Koerber & Co? Yes, O3 �disbenefit� does in fact occur in mid-cities every night and during the winter months as well as in mid-summer. In Manhattan, the Sunday noon O3 increase to 70 ppb from 50 ppb on Friday is well documented. However, all these are conditions of an �ozone hole� (in time or space) when the ambient ozone levels are depressed due to NOx emissions. An NOX reduction under those circumstances reduces the depth of the �ozone hole� but it does not cause extra peaks to occur. So, the excess exposures (above, say 60-80 ppb) is minimal. This is why I think that the disbenefit card is overplayed. Of course, the model difference maps/movies of red-hot disbenefits do not show that these occur at low O3 levels.

Submitted by Rudolf Husar on 5/15/97 RecID: RudolfHusar2

Re: Re: Draft Vol. 1 Changes to

Texas has dne extensive evaluation of the NOx reduction disbenefit and highlights the difficulty in reducing ozone levels below the standard without increasing exposure to many more people; the following data is output based on UAM IV modeling(UAM V could not meet EPA specifications so UAM IV (which does) must be used:
% emission reduction VOC NOx VOC+Nox
0 13 13 13
5 12 17 15
10 10 20 15.5
15 9 27 15.7
20 8 36 16
25 7 40 20
30 6 43 22
35 5.5 47 22
40 5 52 22
45 4 57 20
50 2.5 60 17
55 2 57 13
60 1.5 50 9
65 1.2 45 5
70 1 39 2
75 0.5 34 1
80 0 28 0
85 0 21 0
90 0 15 0
95 0 7.5 0
100 0 0 0

Submitted by John Dege on 5/22/97 RecID: JohnDege13

Re: Re: Draft Vol. 1 Changes to

I disagree with the allegation that the "red hot" disbenefit maps are from in the middle of the night. The work done by LADCo for the Chicago nonattainment area shows a clear disbenefit based on the afternoon peak ozone levels, not the night time levels. While I cannot state that every case claiming disbenefits used the same basis since I have not reviewed them, the cases I have seen where modeling was used did show dramatic increases in the afternoon peak concentrations, not changes in the nighttime levels.

Submitted by David Long on 5/16/97 RecID: DavidLong

Re: Re: Re: Draft Vol. 1 Changes to

Sorry for my confusing statement. I meant that 'disbenefit' can (and from the data does) occur whenever NOx scavenging substantially reduces ambient O3: at night, OR in the winter OR on weedays OR in the near-source core of the urban plume. The daytime urban plume disbenefits are indeed the most pronounced. The 'red hot' comment was intended to suggest looking at the red disbenefit areas near the urban centers in both absolute and relative concentration units.

Submitted by Rudolf Husar on 5/16/97 RecID: RudolfHusar8

Draft Vol.1 Revised to include factual references

Is there evidence that precursor emission changes cause ozone concentration changes?

There is empirical evidence that anthropogenic emission changes do cause changes in ambient ozone concentrations. The weekly cycle of emissions differs from the diurnal and seasonal cycles in that it is exclusively due to man's activities. Hence, a weekly ozone cycle must be exclusively due to anthropogenic emission changes. There is indeed a weekly ozone cycle; ozone data show that throughout the OTAG domain, on Sundays, the 1-hour 120 ppb exceedances are reduced by factor of 3 compared to Friday exceedances. This reduction is most pronounced in urban areas, while in the central portion of the OTAG domain, the weekly ozone cycle is virtually nonexistent. Hence, any control scenario that simulates the weekday-weekend emission changes would be effective in reducing the 1-hour 120 ppb exceedances. It should be noted that the 8-hour 80 ppb exceedances show less weekly fluctuations, indicating that such a control scenario would be less effective in reducing nonattainment with respect to the new standard.
(Because this is close to biogenic levels and temperatures are not dependent on the calendar).

Studies by SAI, Inc. Of Philadelphia have shown a clear association in downward trends of ozone compared to reductions in VOCs from mobile sources.

Ref: Ozone AQCD Ch 3.2.3 :Parrish et al. (1993) have investigated the partitioning between the individual nitrogen-containing species at several rural sites in the eastern United States, and Trainer et al. (1993) and Olszyna et al. (1994) have shown that, in rural areas in the eastern United States, there is a good correlation between the O3 levels and NOy. Trainer et al. (1993) further showed that O3 levels correlate even better with NOz than with NOy, as may be expected because NOz quantifies the amount of initially emitted NO that has been processed photochemically, forming O3 in the process.

Submitted by John Dege on 5/8/97 RecID: JohnDege7

Re: Draft Vol.1 Revised to include factual references

The Executive Summary to the Policy Group does not contain references to any specific reports. It is (collective) 'expert opinion' by the AQA Workgroup.

Submitted by Rudolf Husar on 5/15/97 RecID: RudolfHusar3

Re: Re: Draft Vol.1 Revised to include factual references

yes, I included my references for information purposes for the comment.

Submitted by John Dege on 5/22/97 RecID: JohnDege14

Draft Vol. 1 Need revision to section on ozone and climatical data

The following better reflects the affects of climate on ozone levels:

Comparison of episodes with climatological data?

Generally, HIGH TEMPERATURE, vegetation cover and concetnration of a large number of mobile sources or other sources of VOCs are the key variables in ozone formation. Episodic stratospheric incursions can increase ozone levels substantially.
Studies of New York, Baltimore, Philadelphia and Boston clearly show that the number of exceedances of the ozone standard are associated with hot weather.

Ref: National Research Council, "Rethinking the Ozone Problem in Urban and Regional Air Pollution", 1992, pp 62-63

The number of hot days in NY City has increased substantially after 1940 compared to before 1940 with the maximum number of days above 90 F of 15 increasing to 25 and average from 8 to 11..

Ref: Penn State data as shown in 1996 NY Times

Submitted by John Dege on 5/8/97 RecID: JohnDege6

Re: Draft Vol. 1 Need revision to section on ozone and climatical data

High temperature appears to be more of a coincidental then causal factor for high ozone. In the Northeast, the origin of both hot and high O3 airmasses appears to be similar, so they correlate. In the south-center of OTAG (TN and South) the T-O3 relationship is virtually nonexistent. Stratospheric O3 may contribute 6-20% of O3 in the spring in Canada. My guess is that over OTAG in the Summer the stratospheric O3 is < 2% of the measured O3.

Submitted by Rudolf Husar on 5/15/97 RecID: RudolfHusar4

Re: Re: Draft Vol. 1 Need revision to section on ozone and climatical data

Would like to see data for TN and south that you are referring to.

Submitted by John Dege on 5/22/97 RecID: JohnDege17

Re: Re: Draft Vol. 1 Need revision to section on ozone and climatical data

Would like to see the data for Atlanta.

Submitted by John Dege on 5/22/97 RecID: JohnDege16

Re: Draft Vol. 1 Need revision to section on ozone and climatical data

data from NY have shown that ozone concentrations have decreased in the last 15 years despite increases in hot (>90F) days. the ratio between exceedances and hot days has changed from 1.5 in the early 1980's to 0.5 in the most recent years.

Submitted by Howard Feldman on 5/9/97 RecID: HowardFeldman1

Re: Re: Draft Vol. 1 Need revision to section on ozone and climatical data

yes, with reductions in VOCs from lower vapor pressure gasoline and lower tailpipe emissions, the benefits have been lower numbers of exceedances. High temperatures are generally a prerequisite--not a guaranteee- of very high ozone levels. Most cities are in a VOC limited chemistry region for ozone concentrations. The biogenic emissions are very large in the summer months with isoprene emissions dependent on sunlight intensity (cloud cover decreases- isoprene emissions are "0" in the middle of the night; altthough monoterps and other VOCs are emitted in low quantitites compared to isoprene) and temperature(BEIS2 model predicts 2X increase for every 20 F rise in temperature) and vegetation type. The mixing layer elevation changes dramatically during the day which helps with dilution- Texas models for Houston show a 200 meter overnight level increases to 2000 meters peak during 11:00 AM to 3:00 PM period(mirrors sunlight intensity)-can send data if you like.
Isoprene produces 8 times more ozone than auto exhaust and is much more reactive tiime wise. Can furnich BEIS2 estimates for any county in US if you want to review. On a reactivity basis, isoprene is much more significant thn auto exhaust even if emission estimates are 2X too high.
Remember though, in rural areas where ozone concentrations are NOx limited, sufficient VOC exists for the reactions and excess VOC is almost irrelevant. This is the dilemma facing downwind areas where the transported NOx contributes to higher ozone levels.

Submitted by John Dege on 5/22/97 RecID: JohnDege15

Draft Vol. 1 suggestions:

The following changes are recommended:
What is the lifetime of ozone and precursors over the OTAG region?

Ozone in ambient air is created and destroyed in a series of interacting chemical reactions of varying speeds driven by sunlight in the presence of nitrogen ozides and hydrocarbon gases.. Measurements in National Parks show a direct immediate correlation with ambient air temperature.
Ozone concentrations rise during the day and drop during the night as temperature rises and falls.. As NOx is depleted by formation of nitrates, etc. the ozone concentrations should decline. NOx lifetimes have been estimated to be 6 to 48 hrs. Different VOC chemicals dissociate at varying reaction rates and speeds. Natural VOCs from plants and manmade chemicals have a lifetime of 1 hr to several months.

Ref: EPA Ozone AQCD

Submitted by John Dege on 5/8/97 RecID: JohnDege5

Re: Draft Vol. 1 suggestions:

Yes, O3 is in photostationary state equilibrium near the sources, but once O3 is fully formed and the NOx precursor is gone, O3 is removed by dry deposition (dominant over low emission rural areas at night) or due to chemical scavenging by fresh NOx. The O3 diurnal cycle is due to these removal mechanisms and not due to a temperature -dependent shift in chemical equilibrium as implied in your comment.

Submitted by Rudolf Husar on 5/15/97 RecID: RudolfHusar5

Draft Vol. 1

Suggested revisions:
What are the ranges of ozone transport implied from various studies?

The areas impacted by ozone from large urban areas in the OTAG domain were deduced from multiple types of analysis, resulting in downwind distances ranging from less than 150 miles to over 500 miles. The direct influence of specific urban areas can be easily traced for specific episodes some 30-200 miles into their surrounding rural background. The extent depends on the size of the urban area, wind speed, etc. For Nashville, the distance is about 30 miles. For Baltimore/Philadelphia, the distance is 100 to 200 miles. Beyond that, the urban influence tends to merge indistinguishably into the regional ozone pattern.
For tall utility stacks that emit into the night time thermal layer, the distance is dependent on wind speed and reactivity; aircraft measurements have shown a lifetime of about 15 hours. Thus, if the nighttime thermal windspeed is 40 mph, the maximum distance would be 600 miles before completely disappearing. Since the thermal layer exists for only about 14 hours, tall stacks will not contribute to ozone levels at the surface beyond 600 miles and the residual amount less than that will be indistinguishable from local biogenic sources.

Submitted by John Dege on 5/8/97 RecID: JohnDege4

Re: Draft Vol. 1

Your suggestion that on the average, the Nashville urban plum does not extend ( or is indistinguishable from background) beyond 30 miles can not be reconciled with the observations on the on the grounds that at night the chemistry is dormant but transport is not. For example, the Nashville plume emitted during the 4-6 PM rush hour �wakes up� and starts its ozone formation after a good nights travel of 100-200 miles. Furthermore, in the 1970s we have routinely traced with aircraft the St. Louis urban ozone plume out to 100 miles from the city, during the afternoon good mixing conditions. The other cities you mentioned are roughly within the 150-500 mile range.
The reasoning is similar for the tall stacks. Nighttime NOx emission in such plumes does not even start reacting and producing O3 until the morning - 600 KM away. Average O3 lifetime of 15 hours? Starting from the emission of precursors or after O3 has been formed (which at night may be 12h after emission). I concur with the second interpretation of lifetime.

Submitted by Rudolf Husar on 5/15/97 RecID: RudolfHusar6

Draft Vol. 1 Incomplete on

I believe the revisions that follow more accurately reflect the state of knowledge on transport:

Ozone transport; beneficial or harmful?

In general, the atmosphere can acts as a dispersing agent for air pollutants. Dispersion can cause both beneficial pollutant reduction near a source and harmful pollutant increases downwind of a source. Dispersion takes place through winds (horizontal transport) and vertical mixing (winds and thermals) in the lower atmosphere. Horizontal transport depends on location as well as on elevation above ground, and on time of day. The horizontal transport for elevated emission sources (>100m ??) may be substantially higher than the transport of low-level sources, due to higher wind speeds aloft, especially at night.
The most wide spread regional episodes were found to be associated with slow moving high pressure weather systems that produced high temperatures, light winds, limited vertical mixing, and mostly clear skies.(Ref: EPA AQCD) Measurements by aircraft and model runs have demonstrated that elevated point sources have little or no affect on urban areas and their precursor emissions disappear within 200 miles. It is believed by some that longer transport can occur at night in high speed winds at high elevations but no evidence exists. It is impossible to distinguish local ozone from any that may have resulted form transport of precursors.

THUS, ozone levels which exceed the current standard in urban areas and downwind
of urban areas are caused by a combination of high biogenic emissions and a high concentration of low level manmade sources (mostly trucks and cars) in urban areas.

Ref: TVA aircraft measurements.

Submitted by John Dege on 5/8/97 RecID: JohnDege3

Re: Draft Vol. 1 Incomplete on

The comment that �elevated point sources have little or no affect on urban areas� seems inconsistent with routine plume mapping studies that show ozone formation in daytime power plant plumes 100 miles and beyond. Nighttime plumes have longer impact distances. I can not see any mechanisms for such PP plumes to steer away from the cities along their path. The companion comment that �their precursor emissions disappear within 200 miles� may be pretty close but that still leaves the formaed O3 to travel along for another few hudered miles after the precursor (NOx) is gone. So, discounting point sources as contributors to the ozone pool is not well supported by evidence - but if there is evidence, I would like to know about.

Submitted by Rudolf Husar on 5/15/97 RecID: RudolfHusar7

Draft Vol. 1 Summary Ozone Variance for time & space Improvements

How much does ozone vary in time and space?

Ozone exhibits strong day-to-day variation that can be quantified by examining low ozone and high ozone days across the domain. The urban impact is virtually undetectable during low-ozone days (i.e., the lowest 10th percentile of ozone concentrations). In rural areas temperature is the cause of higher ozone. During the high-ozone days (the 90th percentile) in and near urban areas, the urban influence is very pronounced but confined to about 20 to 60 miles from major metropolitan areas. It is therefore implied that urban areas are causing the highest 1-hour daily maximum ozone concentrations
Generally, zone increases proportionally with increasing temperature during the day and decreases proportionally as temperature decreases. In rural areas where NOx is the predominat precursor affecting ozone levels, air temperature inreases causes increased NO emissions from bacteria in the soil. In urban areas VOCs are the predominat cause of very high ozone levels. Isoprene from vegetation peaks substantially during midday driven by sunlight intensity (a 20 degree F riisin temperature results in a doubling of isoprene and isoprene makes (eight times as much oozone as mobile source emissions on a weight basis).
The added emissions from area sources, automobiles, etc. further increase the ozone levels.
Stratospheric intrusions can increase these levels by 0 to 40 ppb and have been detected between 25 and 40 ppb on 4 of 56 days at White Face Mt. and estimated at 5 to 10 ppb at surface locations.

Ref: :
:Altshuller & LeFohn, Journal of the Air & Waste Management, Vol. 46 February 1996.
: Data from National Park Service for Badlands N.P. S.D. and others;

: EPA BEIS2 biogenic model.
Badlands, N.P. data courtesy of National Park Service

Submitted by John Dege on 5/8/97 RecID: JohnDege2

Drfat Vol 1 Summary does no accurately reflect pattern of ozone

Submitted by John Dege on 5/8/97 RecID: JohnDege1

Re: Drfat Vol 1 Summary does no accurately reflect pattern of ozone

The summertime O3 concentrations you list seem to high when compared with the most recent trend analyses. In the report "Spatial Pattern of Daily Maximum Ozone over the OTAG Region" (http://capita.wustl.edu/OTAG/Reports/otagspat/otagspat.htm) it was shown that during June - August from 1991 - 1995, the average daily maximum ozone values were < 45 ppb in the four corners of the OTAG domain (Maine, Florida, Southern Texas, Minnesota). Also, the daily maximum O3 concentrations exceed 70 ppb less than 10% of the time in these regions.

Submitted by Bret Schichtel on 5/16/97 RecID: BretSchichtel

Vol. 1 Draft

I have read and listened to various experts describe their work/interpretation of their individual ozone issues but have been unable to get a clear total picture, so I have researched and (based on preponderance of information) have arrived at the following summary:

What is the pattern of ozone precursor emissions in the OTAG domain (east of Rocky Mountains)
Biogenic emissions of VOC (trees, grass, crops) and NOx (bacteria in soil) are the primary precursors of ozone absent human influence. In the natural background NOx (NO species) from bacterial in soil is a primary precursor of ozone levels at ground level. Emissions from bacteria are dependent on vegetation cover, soil conditions and temperature. VOC emissions are seasonal and dependent on temperature and sunlight intensity with significantly higher emissions at midday. National Parks in the West which have limited manmade emissions have ozone readings of 0.07 ppm and higher and are typically between 60 and 70 ppb. One explanation for higher ozone levels in other parts of the country is the higher levels of emissions of NO from bacteria in the soil. Using EPA's BEIS2 model estimates for the Midwest, the midAtlantic states) and Gulf Coast suggests ozone levels of 0.12+ ppm for St. Louis, 0.075 ppm for Chicago, 0.08 ppm Philadelphia and 0.05 ppm for Houston. These numbers may be low as the EPA ozone model (UAMIV) for Houston predicts 0.068 ppm as the ozone level with no manmade emission vs. 0.05 based on EPA's biogenic model NO emissions. TX has updated the vegetation data for Houston.
Areas with extensive periods of high temperatures(e.g. Houston, Atlanta) will have a difficult time achieving the current standard of 0.12 ppm for one hour as there is little room for manmade contributions to natural ozone levels.

Ref:
:National Research Council, "Rethinking the ozone Problem in Urban and Regional Air Pollution", 1992, pp 277 and Isopleths for NOx, VOC, ozone
: EPA AQCD Chapter 1, page 2
: 10 highest values, LeFohn (http://ourworld.compuserve.com/homepages/ASL_ASSOCIATES/)

Manmade emissions of volatile organic compounds (VOC) and nitrogen oxides (NOx) within the OTAG domain from area and point sources contribute to the formation of excess ozone on top of the biogenic background.The major source of manmade NOx in the entire OTAG domain are are generally tall stacks of electric utilities located mostly in rural areas. The primary sources of manmade NOx and VOC in urban metropolitan areas are low level emissions such as on road and off road mobile sources.. Area sources of NOx and VOC include manufacturing facilities, gasoline stations, print shops, painting operations ( at homes, repair shops, roads, bridges) and consumer products such as perfumes, insecticides, etc. Temporally, area sources tend to have both a diurnal and seasonal cycle, while point sources are typically more invariant with time.

Submitted by John Dege on 5/8/97 RecID: JohnDege

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