134

EMISSION·CONTROL DEVICES FOR CONVENTIONAL INTERNAL COMBUSTION ENGINE DESIGNS AND THEIR IMPLICATIONS FOR OXIDANT CONTROL STRATEGIES

by

Robert F. Sawyer Professor, Department of Mechanical Engineering University of California Berkeley, California

Most of my comments today will be based upon the National Academy of

Sciences study which has just recently been completed. There are at least

two other people here who have been closely associated with that study,

Professor Newhall, University of Wisconsin, recently of Chevron Research,

who will be the second speaker, and Dr. Benson of Stanford Research Insti­

tute, who was one of the committee members on that study.

There has been some confusion about the National Academy of Sciences

study, since there have been several recently in the automotive emissions

area. The one which appeared in September, 1974, by the Costs/Benefit

Panel received a great deal of publicity, some of it somewhat negative.

I would encourage you to read all four volumes of that report. It does

contain a lot of good information. It did deal with a very fuzzy subject,

that of benefits vs. costs of air pollution control and, therefore, was

not as precise as some would like. The report which has recently been 1 J 1,1 completed (the volumes were released last week) is called the Report by

the Committee on Motor Vehicle Emissions. Because the interest is high,

I'll take a moment to tell you how to get a copy. Request the Report by

the Committee on Motor Vehicle Emissions by writing to the National

Academy of Sciences, specifically the Commission on Sociotechnical Systems,

National Research Council, 2101 Constitution Avenue, Washington, DC 20418. 135

Some of you may have received copies already; those who contributed to the study should have received copies by this time.

One thing that has become apparent during the first day of this meeting and was even reflected by the previous speaker, is that there remain a lot of unknowns, a lot of questions that seem to me should have been answered in the last ten years. In spite of the uncertainties about the cause/effect relationships between emission sources and photochemical smog, the decision, fortunately, has been made to go ahead and control the smog anyway. The general conclusion has been that air pollution is reduced by reducing the emission of air pollutants and an aggressive automobile emission control program has been initiated, although it has been delayed several times, and the results have not come as rapidly as one would have hoped. With the 1975 automobiles, there is indeed a sub­ stantial reduction in hydrocarbon and CO emissions; this impact should now begin to be felt over the next 10 years as these vehicles replace those already on the road.

The costs of these emissions controls are large, somewhere between one and five billion dollars per year. The costs are large, especially in comparison with the investment that has been made in fundamental research to understand the nature of the air pollution problem. I would like to discuss several points: First, I would like to say a few words on the background of the automotive engine emissions controls; then I would like to give my assessment of the 1975 California vehicle and its emission control system--just what its strong points and problems are; and, finally,

I will try to identify what the critical problem areas are now in automotive emissions controls.

I believe it is important to remind you that the automobile engine was developed over the last 50 years with goals in mind which had nothing to do 136. with air pollution. As a consequence, we have an automobile engine which is a low-cost production item, has a high power-to-weight ratio, has turned out to be a reliable, relatively low maintenance, very durable device, and in some cases even the fuel economy is not so bad. Then, aft.er the fact, it was decided that this engine r,hould be made to be low emitting. Therefore, it is not too surprising that the approach of the automobile industry has been to modify thi:; engine, in which they have a great deal of confidence and know how to build inexpensively, as little as possible. The control approaches therefore have been minor modifications to the engine and have now focused upon processing the exhaust. This, to my thinking, as an engineer, is not a good approach. But, objectively, if one judges simply on the basis of whether emissions are controlled or not, has worked out quite well. I do not think we can be too critical of the add-on catalyst technology if i.t works. The evidence now suggests that it is going to work, that it is probably cost effective, and that the auto­ mobile industry probably deserves more credit than they are receiving for the job they've done in developing the oxidation catalyst for the auto­ mobile engine. What I'm saying is, the add-on approach is not necessarily all that bad.

Again, to give some general perspective on how one might approach automotive emission controls and how we arrived where we are, I'd like to discuss Figure 1, which points out several approaches to controlling emissions from the automobile engine. These are:

1) preparation of the air fuel mixture, which has received only minor attention by the auto industry; I I I, 2) modification of the engine itself, the combustion process, which is not very evident in the 1975 automobiles, but will be the subject of

Dr. Newhall's presentation, and 137

3) the general field of exhaust treatment, where most of the effort

has been placed by the U. S. auto industry.

I would like to emphasize that the first area, the whole matter of

mixture control, that is, either improving the present carburetor or

replacing it with a better mixture control system, is perhaps the single

technological area which has been most overlooked by the automobile

industry. The engine requires a well meteTed fuel-to-air mixture over a

wide variety of operating conditions, that is, good cycle-to-cycle and

cylinder-to-cylinder control. The present systems simply do not do that.

It is also evident that the mixture control system must operate with varying

ambient conditions of pressure and temperature. The present systems do not

do that adequately. There are promising developments in improvement of

mixture control systems, both c.arbureted and fuel injection, which do not

appear to be under really aggressive devel,Jpment by the automobile industry.

One should question why this is not occurring.

I will skip the area of combustion modification because that really

comes under the new generation of engines. The combustion modification is

an important approach, and will be discussed by the next speaker.

The area of exhaust system treatment, the third area, is the one about

which you've seen the most. We early saw the use of air injection and then

improved air injection with thermal reactors. Now we're seeing oxidation

catalysts on essentially 100% of the U. S. cars sold in California. There

are yet other possibilities for exhaust treatment: for the control of

oxides of nitrogen based upon reduction catalysts, or what is known as

threeway catalysts, another variation of the reduction catalyst, and

possibly also the use of particulate traps as a way of keeping lead in

gasoline if that proves a desirable thing to do (which does not appear to

be the case). 138

What about the 1975 California car? Most of you probably have enough

interest in this vehicle that you've tried to figure out just what it does.

But in case some of you have not been able to straighten its operation out,

let me tell you, as best I understand, what the 1975 California car is.

The cars from Detroit are 100% cataly~t eq11ipped. There may be an excep­ ,[ l. '1 tion sneaking through here and there, but :it looks like it is 100%. These

are equipped with oxidation catalysts in a variety of configurations and

sizes, the major difference being the pellet system which is used by

General Motors versus the monolith system which has been used by Ford and

Chrysler. The pellet system appears to be better than the monolithic ~ l 'l system, but it is not so obvious that there are huge differences between the

aoc>now. The catalysts come in a variety of sizes; they are connected to

the engine in different ways; sometimes there are two catalysts, sometimes

a single catalyst (the single catalyst being on the 4 and 6-cylinder

engines). Some of the 8-cylinder engines have two catalysts, some of them

have one catalyst. All California cars have all of the exhaust going

through catalysts. This is not true of some of the Federal cars in which

some of the exhaust goes through catalysts and some does not.

Ninety percent of the California cars probably will have air pumps.

Practically all the cars from Detroit have electronic ignition systems

which produce more energetic sparks and more reliable ignition. The

exhaust gas recirculation (EGR) systems appear to have been improved

somewhat over 1974 but not as much as one would have hoped. There were

some early designs of EGR systems which were fully proportional, sophisti­

cated systems. These do not appear to have come into final certification

so that there still is room for further improvement of the EGR system.

The emissions levels in certification of these vehicles are extremely low 139

(Table I). Just how the automc1bile industry selects the emission levels at which they tune their vehicles has been of great interest. The hydrocarbon and CO levels in certification (with deterioration factors applied--so this is the effective emissions of the certification vehicles at the end of 50,000 miles) are approximately one-half the California standards. The oxides of nitrogen emissions are approximately two-thirds of the California standards. This "safety factor" is put in by the automo­ bile industry to allow for differences between the certification vehicles and the production vehicles to ensure that they did not get into a situation of recall of production vehicles which would be very expensive.

There appears to have been a great deal of sophistication developed by the automobile industry in being able to tune their vehicles to specific emission levels. General Motors appears to have done better tuning than the other manufacturers. This leads to the rather interesting result that a significant number of the 1975 California vehicles meet the 1977 emission standards (Table II); that is, approximately 10% of the U. S. cars certified for California already meet the 1977 emission standards. This does not mean to say that the industry could immediately put all of their production into such vehicles and meet the 1977 emission standards, because of a concern about the "safety factor" for the certification versus produc­ tion vehicles. Thirty-four percent of the foreign vehicles certified for

1975 in California meet the 1977 emission standards. The 1977 emission standards are 0.41 g/rn hydrocarbon~ 3.4 g/m carbon monoxid~ and 2.0 g/m oxides of nitrogen. This does confirm that the oxidation catalysts are a more than adequate technology for meeting the 1977 emission standards and only minor refinements and adjustments to those systems are required to go ahead with the 1977 emission standards. There are some other arguments against this optimistic viewpoint, and I'll deal with those later. 140

There is a great uniformity in the deBigns which the U. S. manufactur­ ers have selected for the 1975 California vehicles. For those of you who do not live in California, about 80% of thl~ vehicles in the rest of the country will be catalyst equipped. General Motors is going with 100% catalysts, apparently to realize the fuel economy benefit of their system which more than pays for the cost of the catalyst system. We have the very interesting situation that the more stringent 1975 emission standards have not only reduced the emissions of the 1975 vheicles with respect to the

1973-1974 vehicles, but have also reduced the cost of operating the car and have improved fuel economy. The idea that emissions control and fuel economy and economical operation are always one at odds with the other, is simply not true. Compared to the previous year's vehicles, the more stringent emissions standards of 1975 have brought improvements to fuel economy because they forced the introduction of more advanced technology.

The fuel savings which have been realized produce a net decrease in opera­ tional costs over the lifetime of the car. This is not to say that pollution control doesn't cost something. If you were to compare the 1975 vehicle with a completely uncontrolled vehicle, tht~re would indeed be an incremental cost associated with the 1975 vehicle.

The foreign manufacturers have demonstrated a greater variety of approaches in meeting the 1975 California standards, but again they are producing mostly catalyst equipped vehicles. There is a widespread use of fuel injection by the foreign manufacturers, especially the Europeans, apparently because this is the easiest app·roach for them and they realize that only a fraction of their production comes to the United States.

Volkswagen, for example, apparently has gone to 100% fuel injection on its air cooled engines to be sold in California. Mazda will continue to sell 141 rotary engine vehicles and thereby be the only rotary engine vehicle manufacturer and marketer in the United States. General Motors> elimination of the.rotary engine, stated for reasons of emissions, is probably more influenced by problems with fm"l economy, although the two are a bit difficult to separate. Mazda i.s meeting the 1975 emissions standards and, in fact, can meet the 1977 emission standards. It has not solved its fuel economy difficulties on the 1975 cars; they will do better in 1976. All evidence points to a fuel economy penalty for the rotary engine. Nonethe­ less, we do have this option available because of the Japanese. Also, the foreign manufacturers are providing us with a small number of diesel engine cars. These are of great interest because of definite fuel economy advantages. The diesel engine vehicles also meet the 1977 emissions standards right now. Also in J.975, we'll 3ee the CVCC engine marketed by

Honda.

The costs of the 1975 vehicles over tae lifetime of the vehicle are definitely lower than the costs of the 197,~ vehicles. The National Academy of Sciences estimate averaged over all vehicles is that in comparison to the 1970 vehicles, the lifetime cost of emission control system, including maintenance and fuel economy costs, is aboJt $250 per vehicle, greater in

1975 than 1970. Since the 1974 vehicles w2.re about $500 more expensive, there has been a net saving in going from 1974 to 1975. I think the conclusion we should draw for 1975 is that the auto industry has done a pretty good job in meeting these standards. This is something which they said they couldn't do a few years ago, something which they said that if they could do, it would be much more expewdve than it has turned out to be.

The same technology can be applied to 1977 models with no technological difficulty and only slight refinements of the systems. The fuel economy 142 penalties as estimated by the National Academy of Sciences are small, 3% or less, in going to the 1977 standards. This estimate does assume further advancements by the auto industry to improve fuel economy--primarily improved exhaust gas recirculation systems. It is unfortunate that this issue of fuel economy has become so mixed up with the air pollution question, because the two are only slightly related. If one is really concerned about fuel economy, and there isn't too much evidence that the auto industry or the American public really is too concerned right now, there is only one way to have a drastic effect on fuel economy and that is to decrease the vehicle weight. Until that is done, with gains on the order of 50% or more, to worry about 3 or 5% differences in fuel economy related to emission control systems, is simply to focus upon the wrong issue.

Now, what are the problem areas? What remains to be done? The problems certainly aren't over with the introduction of the 1975 vehicles.

Problem Area Number One: Field performance. What is going to happen to these vehicles when they get into actual service? Past experience with the 1971 through 1973 vehicles has been rather poor, in that EPA and

California surveillance data show that these vehicles are not meeting the standards. Many of them did not meet the standards when they were new.

The situation in general is getting worse, at least for CO and hydrocarbons, that is, with time the emission levels of CO and hydrocarbons for the 1971 I through 1973 vehicles is degrading. There is no in-service experience of this sort with the 1975 vehicles yet. The certification data look quite I promising, but the test procedures, especially for durability, are not the same as what occurs in actual use. It is generally stated that the i 1 actual use situation for the catalysts will be more severe than the EPA test procedure. A larger number of cold starts are involved in actual use than in the EPA test procedure and thermal cycling will probably have an 143 adverse effect on the lifetime of the cata]_yst. This is not so obvious.

It is also likely that the higher temperature duty cycle in actual use will improve the performance of the catalyst in that it will help to regenerate the catalyst through the removal of contaminants, as long as one does not get into an overheat situation. The National Academy of Sciences' estimate was that the number of catalyst failures tn the first 50,000 miles would be on the order of about 7%. That's a very difficult number to estimate in the absence of any real data. A 7% failure still leaves a net gain in emissions control, even if nothing is done about this failure. This points to the problem of what happens after 50,000 miles. The EPA certification procedure and control program only addresses the first 50,000 miles. The second 50,000 miles or slightly less for the average car, is the responsi­ bility of the states. Unfortunately, then~. seems to be very little progress in the area of mandatory inspection and ma-Lntenance--very little thought being given to whether the replacement oft.he catalyst at 50,000 miles, if it has failed, is going to be required, and how that is going to be brought about. The area of field performance remains a major problem area, one which obviously needs to be monitored, as the California Air

Resources Board has been doing in the past, but probably even more carefully because the unknowns are higher with the ca.talyst systems.

Problem Area Number Two: Evaporative hydrocarbons from automobiles.

It was identified at least 18 months ago that the evaporative emission control systems are not working, that the evaporative emissions are on the order of 10 times greater than generally thought. In the Los Angeles area, cars which are supposed to be under good evaporative emissions controls are emitting approximately 1.9 grams per mile of hydrocarbons through evaporation. This apparently has to do with the test procedure used. 144

The EPA is pursuing this. The California Air Resources Boa.rd does have some

consideration going on for this, but it appears that the level of activity

in resolving this problem is simply not adequate. If we are to go ahead

to 0.4 of a gram per mile exhaust emissions standards for hydrocarbons,

then it just doesn't make sense to let 1.9 grams per mile equivalent escape

through evaporative sources.

Problem Area Number Three: What about the secondary effects of the

catalyst control systems? Specifically, this is the sulfate emissions

problem, and I really do not know the answer to that. Our appraisal is

that it is not going to be an immediate problem, so we can find out what

the problem is in time to solve it. The way to solve it now, since the

automobile industry is committed to catalysts and it is unreasonable

to expect that they will reverse that technology in any short period of

time, is take the sulfur out of the gasoline. The cost of removing sulfur

from gasoline is apparently less than one cent per gallon. Therefore, if

it becomes necessary to be concerned with sulfate emissions, the way to

meet the problem is to take the sulfur out of gasoline. Obviously, sulfate

emissions need to be monitored very carefully to see what happens. The

final appraisal is certainly not now available. Another secondary effect

of the catalysts is the introduction of significant quantities of platinum

into an environment where it hasn't existed before. Not only through

exhaust emissions, which appear to be small, but also through the disposal

problem of the catalytic reactors. Since the quantity of platinum involved

is quite small, the argument is sometimes used that platinum does not

represent much of a problem. The fact that the amount of platinum in the

catalyst is so small may also mean that its not economical to recover it.

,,, This is probably unfortunate because then the disposal of these catalysts l .Jj 145 becomes important. I will not speak to the medical issues because I am not qualified. The evidence is that th€~ platinum will be emitted in a form which does not enter into biological cycles--but this is no assurance that it couldn't later be transformed in such a form. What is obviously needed is a very careful monitoring program which, hopefully, was started before the catalysts were put into service. If it wasn't, then it should be started today.

Problem Area Number Four. NO control. The big problem with NO X X control is that nobody seems to know or to be willing to establish what the emission control level should be. It is essential that this be tied down rapidly and that it be fixed for a reiatively long period of time, because the NO level is going to have a VE~ry important effeet upon the X development of advanced engine technology. The 2.0 g/m level has been attained in California with some loss of fuel economy through the use of

EGR and it is not unreasonable, in our estimation, to go to 1.5 grams per mile with very little loss in fuel economy. To go to 0.4 gram per mile with present technology requires the use of one of two catalytic systems, either the reduction catalyst in tandem with the oxidation catalyst or what is known as the three-way catalyst. Both of these systems require techno­ logical gains. The state of development appears to be roughly that of the oxidation catalyst two years ago. The auto industry will probably say that it is not quite that advanced, but that if it were required to go to

0.4 gram per mile in 1978 that it could be done. With the catalyst systems, the fuel economy penalties would not be great, in fact, the improvement to the engine which would be required to make the system work would again probably even allow a slight improvement in fuel economy. What the 0.4 gram per mile NO catalyst system would appear to do, however, is to X 146 eliminate the possibility of the introduction of stratified charge engines, both the CVCC and the direction injection system, and also diesel engines.

It is in the context of the advantages of these advanced engines to meet emission standards with improved fuel economy that one should be very cautious about the 0.4 gram/mile oxides of nitrogen standards for automo­ biles. My own personal opinion is that the number should not be that stringent, that a number of 1 or 1.5 g/m is appropriate. Such a level would require advancements but would not incur great penalties.

Other items which I view as problem areas are less technically involved and therefore require fewer comments.

• Nonregulated pollutants--again, thls is a matter of keeping track

of particulates, aldehydes ., hydrocarbon composition, to make

certain that important pollutants :ire not being overlooked, or

that emission control systems are not increasing the output of

some of these pollutants.

• Fuel economy. The pressures of fuel economy are going to be used

as arguments against going ahead wlth emissions control. Mostly,

these two can be resolved simultaneously. We should simply ask

the automobile industry to work harder at this.

• Final problem area: New fuels. Again, it does not appear that

the introduction of new fuels will come about as an emissions

control approach, but that they may be introduced because of the

changing fuel availability patterns and the energy crisis. These

fuels should be watched carefully for their impact upon emissions.

This does ·appear to be an area in which a great deal of study is

going on at the present time. It is one problem area, perhaps, in

which the amount of wprk being done is adequate to the problem

which is involved. 147

In sunnnary, then, the appraisal of the 1975 systems is that they are a big advancement; they will be a lot better than most of us thought, and

that we should give the automobile industry credit for the job they've done in coming up with their emissions control systems.

With that boost for the auto industry, which I'm very unaccustomed

to, I'll entertain your questions. ~_;~a-\ -,.J..~ ..... -~r.:..-. _, --=~-- -___ja--~ .,_,_1~~ ...~-:...~----= ... -~-~ ~.

AIR

,---- 1-4 FUEL 1 I I ENGINE I I I I ______. EXHAUST SYSTEMI • EXHAUST I I + MIXTURE CONTROL COMBUSTION MODIFICATION EXHAUST TREATMENT Fuel/Air Metering Ignition Air Jnjection' Fuel/Air Mixing Chamber Geometry' Thermal Reactor Fuel Vaporization Spark Timing Oxidation Catalyst Mixture Distribution Staged Combustion Reduction Catalyst Fuel Characteristics Ex tern al· Combustion Three Way Catalyst Exhaust Gas Redrculation Particulate Trap

FIGURE 1. Approaches to the Control of Engine Emissions.

~ .i::,. 00

U- ~..a....1 ------=-~ ~~~ 149

TABLE I

Average Emissions of 1975 Certification Vehicles (As Corrected Using the 50,000-Mile Deterioration Factor)

Emissions in g/mi Fraction of Standard HC CO NO HC CO NO Federal 1975 X X

AMC 0.65 6.7 2.5 0.43 0.45 0.80

Chrysler 0.74 7.7 2.5 0.49 0.51 0.82

Ford 0.81 9.2 2.4 0.54 0.61 0.78

GM 0.83 8.0 2.3 0.55 0.53 0.74

Weighted Average* 0.80 8.2 2.4 0.53 0.55 0.76

California 1975

AMC 0.42 4.9 1.7 0.47 0.54 0.87

Chrysler 0.48 6.1 1.6 0.53 0.67 0.82

Ford 0.52 5.6 1.3 0.58 0.62 0.67

GM 0.65 5.5 1.6 0. 72 0.61 0.82

Weighted Average* 0.58 5.6 1.6 0.64 0.62 0.78

:k"Weighted average assumes the following market shares: AMC, 3%; Chrysler, 16%; Ford, 27%; and GM, 54%. 150

TABLE II

Total Number of Vehicles Certified for California 1975 Standard and the Number (and percentage) of .These Able to Meet Certain More Stringent Standar.ds

Calif. 1975 Federal 1977 Hypothesized Hypo thesized

'~ 0.9/9.0/2.0 0.4/J.4/2.0 0.4/9.0/2.0 0.9/3.4/2.0 i Manufacturer no. (%) no. (%) no. (%) no. (%)

AMC 16 (100) 1 ( 6) ti ( 38) 3 (19)

{ Chrysler 21 (100) 2 ( 9) ( 33) 0 ( O)

Ford 26 (100) 4 (15) '-'· ( 15) 5 (19) l GM 46 (100) 1 ( 2) '-1 ( 9) 5 (11) Foreign 62 (100) 21 (34) 3H (61) 28 (45)

1J f' 151

- 'l CURRENT STATUS OF ALTERNATIVE AUTOM)BII.E ENGINE TECHNOLCX;Y

by Henry K. Newhall Project Leader, Fuels Division Chevron Research Canpany Ri.cbm:md, California I\ iH1'· 1.0 1ntroduction and General Background I

1.1 General The term "stratified ct1arge eng:lne" has been used for many years in connection with a variety of unconventional engine combustion systems. Common to nearly all such systems is the combustion of fuel-air mixtures havlng a significant

gradation or stratification in fuel- concentration within the engine combustion chamber. Henee the term nstratifled charge." Historically the objective of stratified charge engine designs has been to permit spark ignition engine operation with average or overall fuel-air ratios lean beyond the ignition limits of conventional combustion systems. The advantages of this type of operation will be enumerated shortly. Attempts at achieving this objective date back to the first or second decade of this century. 1

More recently, the stratified charge engine has been recognized as a potential means for control of vehicle pollutant emissions with minimum loss of fuel economy. As a consequence, the various stratified charge concepts have been the focus of renewed interest. 152

1.2 Advantages and Disadvantages of Lean Mixture Operation

Fuel-lean combustion as achieved in a number of the stratified charge engine designs receiving current attention has both advantages and disadvantages wnen considered from the com­ bined standpoints of emissions· control, vehicle performance, and fuel economy.

Advantages of lean mixture operation include the following:

Excess oxygen contained in lean mixture combustion gases helps to promote complete oxidation of hydro­ carbons (HG) and carbon monoxide (CO) both in the engine cylinder and in the exhaust system.

Lean mixture combustion results in reduced peak engine cycle temperatures and can, therefore, yield lowered nitrogen oxide (NOx) emissions.

Thermodynamic properties of lean mixture combustion products are favorable from the standpoint of engine cycle thermal efficiency (reduced extent cf dissocia­ tion and higher effective specific heats ratio).

Lean mixture operation caG reduce or eliminate the need for air throttling as a means of engine load control. The consequent reduction in pumping losses can result in significantly improved part load fuel economy. 153

Disadvantages of lean mixture operation include the following:

Relatively low combusti.on gas temperatures during the engine cycle expansion and exhaust processes are inherent i~ lean mixture operation. As a conse­ quence, hydrocarbon oxidation reactions are retarded; and unburned hydrocarbon exhaust emissions can be excessive.

Engine modifications ai.med at raising exhaust tempera­ i tures for improved HC emissions control (retarded ·~ ignition timing, lowered compression ratlo, protrtacted \ 1 combustion) necessarily impair engine fuel economy. 'I

1j • ,, If lean mixture operation is to be maintained over ~ the entire engine load range, maximum power output t ;l and, hence, vehicle performance are significantly impaired.

Lean mixture exhaust gases are not amenable to treat­ ment by existing reducing catalysts for NOx emissions control.

Lean mixture combustion if not carefully controlled can result in formation of undesirable odorant materials that appear ln si.gnificant concentrations

in the engine exhaust. Diesel exhaust odor is typical of this problem and is. thought to derive from lean mix­ ture regions of the combustion chamber. 154

Measures required for control of NOx emissions

to low levels (as example EGR) can accentuate

the above HC and odorant emissions problems.

Successful development·or the several stratified charge engine designs now receiving serious attention will depend

very much on the balance that can be achieved among the

foregoing favorable and unfavorable features of lean com­ bustion. This balance will, of course, depend ultimately on

the standards or goals that are set for emissions control,

fuel economy, vehicle performance, and cost. Of particular

importance are the relationships between three factors -

UBHC emissions, NOx emissions, and fuel economy.

1.3 Stratified Charge Engine Concepts

Charge stratification permitting lean mixture operation has

been achieved in a number of ways using differing concepts

and design configurations.

Irrespective of the means used for achieving charge stratifi­

cation, two distinct types of combustion process can be iden­

tified. One approach involves ignition of a small and

localized quantity of flammable mixture whi.ch in turn serves

to ignite a much larger quantity of adjoining or sur~rounding

fuel-lean mixture - too lean for ignition under normal cir­

cumstances. Requisite m1.xture stratification has been achieved 155 in several different ways rangiDg from use of fuel injection dj.rectly into "open" combustion chambers to use of dual combustion chambers divided physically into rich and lean mixture regions. Under most operating conditions, the overall or average fuel-air ratio is fuel-lean; and the advantages enumerated above for lean operation can be realized.

A second approach involves timed staging of the combustion process. An initial rich mj_xture stage in which major com­ bustion reactions are completed is followed by rapid mixing of rich mixture combustion products with an excess of air. Mixing and the resultant temperature reduction can, in principle, occur so rapidly that minimum opportunity for NO formation exists; and, as a consequence, NOx emissions are low. Sufficient excess air is made available to encourage complete oxidation of hydrocarbons a.nd CO in the engine cylinder and exhaust system. The staged combustion concept has been specifically exploited 1.n so-called divided-chamber or large volume prechamber engine designs. But lt will be seen that staging is also inherent to some degree in other types of stratified charge engines.

The foregoing would indicate that stratified charge engines can be categorized either as "lean burn" engines or "staged combustion" engines. In reality, the division between con­ cepts is not so clear cut. Many engines encompass features of both concepts. 156

1.4 Scope of This Report During the past several years, a large number of engine designs falling into the broad category of stratified charge engines have been proposed. Many of these have been evaluated by com­

petent organizations and have been found lacking in one or a

number of important areas. A much smaller number of stratified charge engine designs have shown promise for improved emissions control and fuel economy with acceptable performance, dura­ bility, and production feasibility. These are currently

receiving intensive research and/or development efforts by major organizations - both domestic and foreign.

The purpose of this report i.s not to enumerate and describe the many variations of stratified charge engine design that have been proposed in recent years. Rather, it is intended to focus on those engines that are receiving serious development efforts

and for which a reasonably Ja.rge and sound body of experimental data has evolved. It is hoped that this approach will lead to a reliable appraisal of the potential for stratified charge engine systems.

2.0 Open-Chamber Stratified Charge Engines 2.1 General From the standpoint of mechanical design, stratified charge engines can be conveniently divided into two types: open-chamber and dual-chamber. The open-chamber stratjfied charge engine

has a long history of research lnterest. Those crigines 157

reaching the most advanced stages of development are probably the Ford-programmed c~mbustion process (PROC0) 2 , 3 and Texaco's controlled combustion process (TCCS). 4 , 5 Both engines employ a combination of inlet aar swirl and direct timed combustion chamber fuel injection to achieve a local fuel-rich ignitable mixture near the point of ignition. _For both engines the over­ all mixture ratio under most operating conditions is fuel lean.

Aside from these general design features that a.re common to the two engiries, details of their respective engine_cycle pro­ cesses are quite different; and these differences reflect strongly in comparisons of engine performance and emissions characteristics.

2.2 The Ford PROCO Engin~ 2.2.1 Description The Ford PROCO engine is an outgrowth of a stratified charge development program initiated by Ford in the late 1950's. The development objective at that time was an engine having diesel­

like fuel economy but with performance, noise levels, and driveability comparable to those of conventional engines. In the 1960's, objectives were broadened to include exhaust emissions control.

A recent developmental version of the PROCO engine is shown in

Figure 2-1. Fuel is injected directly into the combustion chamber during the compression stroke resulting in vaporjzation and :formation of a r:i.ch mixture cloud or kernel in the immediate 158

vicinity of the spark plug(s). A flame initiated in this rich mixture region propagates outwardly to the increasingly fuel­ lean regions of the chamber. At the same time, high air swirl velocities resulting from special orientation of the air inlet system help to promote rapid mixing of fuel-rich combustion products with excess air contained in the lean region. Air swirl is augmented by the "squ1sh" action of the piston as it approaches the combustion chamber roof at the end of the com­ pression stroke. The effect of rapid mixing can be viewed as promoting a second stage of cori1bustion in which rlch mixture zone products mix with air contained in lean regions. Charge stratification permits operation with very lean fuel-air mix­ tures with attendent fuel economy and emissj_ons advantages. In addition, charge stratification and direct fuel injection per­ mit use of high compression ratios with gasolines of moderate octane quality - again giving a substantial fuel economy advantage.

Present engine operation includes enrichment under maximum

power demand conditions to mixture ratios richer than stoichiometric. Performance, therefore, closely matches that of conventionally powered vehicles.

Nearly all PROCO development plans at the present time include

use of oxidizing catalysts for HC emissions control. For a given HC emissions standard, oxidizing catalyts permit use of leaner air-fuel ratios (lower exhaust temperatures) 159 together with fuel injection and ignition timing character­ istics optimized for improved fuel economy.

2.2.2 Emissions and Fuel Economy Figure 2-2 is a plot of PROCO vehicle fuel economy versus NOx emissions based or1 the Federal CVS-CH test procedure. Also included are corresponding HC and CO emissions levels. Only the most recent test data have been plotted since these are most representative of current program directions and also reflect most accurately current emphasis on improved vehicle

fuel economy. 6 , 7 For comparison purposes, average fuel

economies for 1974 production vehicles weighing 4500 pounds and 5000 pounds have been plotted.~ (The CVS-C values reported in Reference 8 have been adjusted by 5% to obtain estimated CVS-CH values.)

Data points to the left, on Figure 2-2, at the o.4 g/mile NOx level, represent efforts to achieve statutory 1977 emissions levels. 6 While the NOx target of o.4 g/mile was met, the requisite use of exhaust gas recirculation (EGR) resulted in HC emissions above the statutory level.

A redefined NOx target of 2 g/n1ile has resulted in the recent data points appearing in the upper right hand region of Figure 2-2. 7 The HC and CO emissions values listed are

1 without exhaust oxidation catalysts. Assuming catalyst l ·l conversion efficiencies of 50-60% at the end of 50,000 miles of operation, HC and CO levels will approach but not meet 160 statutory levels. It is cl.ear that excellent fuel economies have been obtained at the indlcated levels of emissions control - some 40% to 45% improved re1at1ve to 1974 produc- tj_on vehicle averages for the same weight class.

The cross-hatched horizontal band appearing across the upper part of Figure 2-2 represents the reductions in NOx emissions achieveble with use of EGR if HC emissions are unrestricted. The statutory 0.4 g/mile level can apparently be achieved with this engine with little or no loss of fuel economy but with significant increases in HC emissions. The HC increase is ascribed to the quenching effect of EGR in lean-·mixture regions of the combustion chamber.

2.2.3 Fuel Requirements

Current PROCO engines operated v1ith 11: 1 compression ratio yield a significant fuel economy advantage over conventional production engines at current compression ratios. According to Ford engineers, the PROCO engine at this compression ratio j_s satisfied by typical fu1J.-boi1ing commercial gaso­ lines of 91 RON rating. Conventional engines are limited to compression ratios of about 8:1 and possibly less for operation on similar fuels.

Results of preliminary experiments indicate that the PROCO engine may be less sensitive to fuel volatility than conven­ tional engines - m1 important ff1.ctor in flextb1l:lty from the standpoint of the fuel supplier. 161

2.2.4 Present Status Present development objectives are two-fold:

Develop calibrations for alternate emissions target levels carefully defining the fuel.econofuy pbten­ tial associated with each level of emissions control.

Convert engine and auxiliary systems to designs feasible for high volume production,

2.3 The Texaco TCCS Stratified Charge Engine 2.3.1 General Description Like the Ford PROCO engine, Texaco's TCCS system involves_ coordinated air swirl and direct combustion chamber fuel injection to achieve charge stratification. Inlet port­ induced cylinder air swirl rates typically approach ten times the rotational engine speed. A sectional view of the TCCS combustion chamber is shown in Figure 2-3.

Unlike the PROCO engine, fuel injection in the TCCS engine begins very late in the compression stroke - just before th~ desired time of ignition. As shown in Figure 2-4, the first portion of fuel injected is immediately swept by the swirling air into the spark plug region where ignition occurs and a flame front is established. The continuing stream of injected fuel mixes with swirling air and is swept into the flame region. In many respects, the Texaco process resembles the 162

spray burning typical of dj_esel combustion ~r1.th the dif­ ference that ignition is achieved by energy from an elec- tric spark rather than by high compression temperatures. The Texaco engine, like the diesel engine, does not have a significant fuel octane requirement. Further, use of positive

I spark ignition obviates fuel cetane requirements character- istic of diesel engines. The resultant flexibility of the TCCS engine regarding fuel requirements is a si~1ificant attribute.

In contrast to the TCCS system, Ford's PROCO system employs relatively early injection, vaporization, and mixing of fuel with air. The combustion process more closely resembles the premixed flame propagation typical of conventional gasoline engines. The PROCO engine, therefore, has a definite fuel octane requirement and cannot be considered a multifuel system.

The TCCS engine operates with h:i__gh compression ratios and with little or no inlet air throttling except at idle con­ ditions. As a consequence, fuel economy is excellent--both at full load and under part load operating conditions.

2.3.2 Exhaust Emissions and Fuel Economv Low exhaust temperatures characteristlc of the TCCS system have necessitated use of exhaust oxidation catalysts for control of HC emissions to low lf~Vels.. A11 recent development 16.3

programs have, therefore, included use of exhaust oxidation catalysts; and most of the data reported here r~present tests

with catalysts installed or with engines tuned for use with catalysts.

Figures 2-5 and 2-6 present fuel economy data at several exhaust emissions levels for two vehicles--a U.S. Army M-151 vehicle with naturally aspirated 4-cylinder TCCS conversion and a Plymouth Cricket with turbocharged 4-cylinder TCCS

engine. 9 , 10 1urbocharging has been used to advantage to increase maximum power output. Also plotted in these figures I are average fuel economies for 1974 production vehicles of similar weight. 8 I . When optimized for maximum fuel economy, the rrccs vehicles

can meet NOx levels of about 2 g/mile. It should be noted that these are :relatively lightueight vehicles and that

increasing vehicle weight to the 4000-5000 pound level could result in significantly increased NOx emissions. Figur~s 2-5 and 2-6 both show that engine modifications for reduced NOx levels including retarded combustion timing, EGR, and increased exhaust back pressure result in substantial fuel economy penalties.

For the naturally aspirated engine, reducing NOx emissions

:from the 2 g/mile level to O. l~ g/mile i.ncurred a fuel economy penalty of 20%. Reducing NOx from the tllrbocharged 164

engine from 1.5 g/mile to 0.4 g/mile gave a 25% fuel economy penalty. Fuel economies for both engines appear to decrease uniformly as NOx emissions are lowered.

For the current TCCS systems, most of the fuel economy penalty associated with emissions control can be ascribed to control of NOx emissions; although several of the measures used for NOx control (retarded cornbusticn timing and increased exhaust back pressure) also help to reduce HG emissions. HC and CO emissions ari effectively controlled with oxidation catalysts resulting in relatively minor reductions in engine efficiency.

2.3.3 TCCS Fuel Reauirements The TCCS engine is unique among current stratified charge systems in its multifuel capability. Successful operation with a nuraber of fuels ranging from gasoline to No. 2 diesel

Table 2-I

Emissions and Fuel Economy of Turbocharged TCCS Engine-Powered Vehicle 1

Emissions g/Mi.le 2 Fuel Economy, Fuel HC co NOx mng2

Gasoline 0.33 1.04 0.61 19.7

JP-4 0.26 1.09 0.50 20.2

100-600 0.14 0.72 0.59 21.3

No. 2 Diesel 0.27 J • l ~ 0.60 23.0 - 1M-151 vehicle, 8 degrees coffibustion retard, 16% light load EGR, tw0 catalysts (Ref. 10).

2 CVS-CH, 2750 pounds :tnert1.a welght. 165

has been demonstrated. Table ~-I lists emissions levels and fuel economies obtained with a turbocharged TCCS-powered M-151 vehicle when operated on each of four different fuels. 10 These fuels encompass wide ranges in gravity, volatj.lity, octane number, and cetane leve1 as ·shown in Table 2-II.

Table 2-II Fuel Specifications for TCCS Emissions Tests (Reference 10)

No. 2 Gasolj_ne 100-600 JP-4 Diesel Gravity, 0 API ;8.8 48.6 54.1 36.9 Sulfur, % - 0.12 0.020 0.065 Distillation~ OF l IBP 86 110 136 390 10% 124 170 230 435 50% 233 358 314 508 90% 342 544 459 562 EP 388 615 505 594 TEL, g/Gal. 0.024 0.002 -· - Research Octane 91.2 57 - - Cetane No. - 35.6 - lta. 9

Generally, the emissions levels were little affected by the wide variations in fuel properties. Vehicle fuel economy varied in proportion to fuel energy content.

As stated above, the TCCS engine is unique in its multifuel capability. The results of Tables 2-I and 2-II demon­

strate that the engine has neither 8ign:1.ficant fuel octane nor cetane requirements and further that it can tolerate 166 wide variations j_n fuel volati1tty. :.rhe flexibility offered by this type of system could be of major importance in future years.

2.3.4 Durability, Performance, Production Readiness

Emissions control system durability has been demonstrated by

mileage accumulation tests. Ignltion system service is more

severe than for conventional engines due to heterogeneity of the fuel-air mixture and also to the high compression ratios involved. The ignition system has been the subject of intensive development, and significant progress in system reliability has been made.

A preproduction prototype engine employing the TCCS process is now being developed by the Hercules Division of White Motors Corporation, under contract to the U.S. Army Tank Automotive Command. Southwest Research Inr)titute will conduct reliability tests on the White-developed enGines when installed in Military veh:l.cles.

3.0 Small Volume Prechambcr Eng1nes (3-Valve Prechamber Engines, Jet Ignition Engines, Torch Ignition Engines) 3.1 General A number of designs achieve charge stratification through division of the combustion region into two adjacent chambers. The emissions reduction potenti&l for two types of dual­

chamber engines has been demonst.rated. F:1 rst ~ j n B. desJ.gn

trad1t1.on~JJy caJ.Jl?d the nrreeb?.rnber eng:ine," a. 2m211 a.uxil1ary 167

or ignition chamber equipped w1th a spark plug communicates with the much larger main combustion chamber located in the space above the piston (Figure 3-1). The prechamber, which I typically contains 5-15% of the total combustion volume, jl is supplied with a small quantity of fuel-rich ignitable !I i fuel-air mixture while a large quantity of very lean and ,j normally unignitable mixture is applied to the main chamber I above the piston. Expansion of high temperature flame products from the prechamber leads to ignition and burning of the lean maj_n chamber fuel-a:_r charge. Ignition· and combustion in the lean main chamber region are promoted both by the high temperatures of prechamber gases and by.the mixing that accompanies the jet-like motion of prechamber products into the main chamber.

Operation with lean overall mixtures tends to limit peak com­ bustion temperatures, thus minimizing the formation of nitric oxide. Further, lean mixture combustion products contain sufficient oxygen for complete oxidation of HC and CO in the engine cylinder and exhaust system.

It should be reemphasized here that a iraditional problem with lean mixture engines has been low exhaust temperatures which tend to quench HC oxidation reactions leading to excessive emissions.

Control of HC emissions to low levels requires a retarded or slowly developing combustion process. The consequent exten­ sion of heat release j nto 1ate por.t:tt)ns of the eng:tne cycle 168 tends to raise exhaust gas temperatures, thus promoting complete oxidation of hydrocarbons and carbon monoxide.

3.2 Historical Background and Current Status 3.2.1 Early Developm9nt Objectives and Engine Def.; igns

The prechamber stratified .charge engine has existed in various forms for many years. Early work by Ricardo 1 indicated that the engine could perform very efficiently within a limited range of care.fully controlled operating conditions. Both fuel-injected and carbureted prechambcr engines have been built. A fuel-injected design :Lnittally conceived by Brodersen11 was the subject of extensive study at the

University of Rochester for nearly a decade. 12 , 13 Unfor­ tunately, the University of Rochester work was undertaken prior to widespread recognition of the automobile emissions problem; and, as a consequence, emission:; characteristics of the Brodersen engine were not determined. Another prechamber engine receiving attention in the early 1960's is that con­ ceived by R. M. Heintz 14 • The objectives of this design were reduced HC emissions, incr0ased fuel economy, and more flexible fuel requirements.

Experiments with a prechamber engine design called ''the torch ign:i.tion eng:.i.nen were reported :..n the U.S.S.R. by Nilov15 and later by Kerimov and Mekhtier. 16 This designation refers to the torchlike jet of hot comhust1on gases issuing 169

from the precombustion chamber upon j_gnj_ tion. In a recent publication, 17 Varshaoski et al. have presented emissions data obtained with a torch ignition engine. These data show significant pollutant reductions relative to conventional engines; however, their interpretation in terms of require­ ments based on the Federal emissions test procedure is not clear.

3. 2. 2 Current DeveloJ)ments

A carbureted ·three-valve prechamber engine, the Honda CVCC system, has received considerable recent attention as a l potential low emissions power plant. 18 This system is illustrated in Figure 3-2. Honda's current design employs a conventional engine block and piston assembly. Only_ the cylinder head and fuel inlet system differ from current automotive practice. Each cylinder is equipped with a small

precombustion chamber communicating by means of a.n orifice with the main combustion chambe!' situated above the piston. lj ij_ A small inlet valve is located :i.n each precharnber. Larger inlet and exhaust valves typical of conventlonal automotive practice are located in the main combustion chamber. Proper proportioning of fuel-air mixture between prechamber and

main chamber is achieved by a combination of throttle con­ trol and appropriate inlet valve timing. A relatively slow and uniform burning process gjvjng rise to elevated combus­ tion temperatures late in the expansion stroke and during

the exhaust procez,s is achi.eved. H:1 gh tewperaturr--s in thin part of the engine cycle ar-e necessary to promote complete 170 oxidation of HC and CO. It s:i:1ould be no~ed that these elevated exhaust temperatures are necessarily obtained at the expense of a fuel economy penalty.

To reduce HC and CO emissions to required levels, it has been necessary for Honda to employ specially designed inlet and exhaust systems. Supply of extremely rich fuel-air mixtures to the precombustion chambers requires extensive inlet manifold heating to provide adequate fuel vaporization. This is accom­ plished with a heat exchange system between inlet and exhaust streams.

To promote maximum oxidation of HC and CO in the lean mixture CVCC engine exhaust gases, it has been necessary to conserve as much exhaust heat as possible and also to incr'ease exhaust manifold residence time. This has been done by using a rela­ tively large exhaust manifold fitted with an internal heat shield or liner to minimize heat losses. In additj_on, the exhaust ports are equipped with thin metallic liners to minimize loss of heat from exhaust gases to the cylinder

head casting.

Engines similar in concept to the Honda CVCC system are under

development by other companies including Ttyota and Nissan in Japan and General Motors and Fo~d in the United States.

Honda presently markets a CVCC-powered vehicle tn t.Tapan and plans U.S. introduction in 1975. Othe~ manufactur~rs

includlnr; General Motors and For>d 1.n thr:: U. S, havf:~ stated 171

that CVCC-type engines could be manufactured for use in limited numbers of vehicles by as early as 1977 or 1978.

3.3 Emissions and Fuel Economy with CVCC-Type Engines 3.3.1 Recent Emissions Test Results Results of emissions tests with the Honda engine have been very promising. The emissions levels shown in Table 3-I are typical and demonstate that the Honda engine can meet statutory 1975-1976 HC and CO stindards and can approach the statutory 1976 NOx standard. 19 Of particular importance, durability of this system appears excellent as evidenced by the high mileage emissions levels reported in Table 3-I. Any deterioration of l emissions after 50,000 miles of engine operation was slight and apparently insignificant. I Table 3-I Honda Compound Vortex-Controlled Combustion-Powered Vehicle 1 Emissions

Fuel Economy, Emissions, 2 mpg g/Mile 1975 1972 HC co NOv FTP FTP Low Mileage Car3 No. 3652 0.18 2.12 0.89 22.1 21.0 50,000-Mile Car'+ No. 2034 0.24 1.75 0.65 21.3 19.8 1976 Standards o.41 3.4 2.0 - - 1977 Standards o.41 3.4 0.4 - -

1Honda Civic vehicles. 2 1975 CVS C-H procedure with 2000-lb inertia weight. 3Average of five tests. a.Average of four tests. 172

Recently, the EPA has tested a larger vehicle conve~ted to the Honda system. 20 This vehicle, a 1973 Chevrolet Impala with a 350-CID V-8 engine, was equipped with cylinder heads and induction system built .by Honda. The vehicle met the present

1976 interim Federal emissions standards though NOx levels were substantially higher than for the much lighter weight Honda Civic vehicles.

Results of' development tests conducted by General Motors are shown in Table 3-II. 21 These tests involved a 5000-pound Chevrolet Impala with stratified charge engine conversion. HC and CO emissions were below 1977 statutory limits, while NOx emissions ranged from 1.5 to 2 g/mile. Average CVS-CH fuel ec9nomy was 11.2 miles per gallon.

Table 3-II Emissions and Fuel Economy for Chevrolet Impala Str·atified Charge Engine Conversion (Ref. 21)

Exhaust Emlssions, Fuel g/Mile 1 Economy, Test HC co NOx mpg

1 0.20 2.5 1.7 10.8 2 0.26 2.9 1.5 11.7 3 0.20 3.1 1.9 11.4 4 0.29 3.2 1. 6 10.9 5 0 .. 18 2.8 1.9 11.1 Average 0.23 2.9 1.7 11.2

1cvs-CH, 5000-lb inertia weight. 173

3.3.2 HC Control Has a Significant Impact on Fuel Economy In Figure 3-3, fuel economy data for several levels of hydro­ carbon emissions from QVCC-type stratified charge engines

are plotted. 22 , 23 ~ 24 At the 1 g/mile HC level, stratified charge engine fuel economy appears better than the average fuel economy for 1973-74 production vehicles of equivalent weight. Reduction of HC emissions below the 1-gram level necessitates lowered compression ratios and/or retarded ignition timing with a consequent loss of efficiency·. For I the light-weight (2000-pound) vehicles the O.~ g/mile IIC emissions standard can be met with a fuel economy of 25 mpg, a level approximately equal to the average of 1973 produc­ tion vehicles in this weight class. 8 For heavier cars, the HC emissions versus fuel economy trade-off appears less favorable. A fuel economy penalty of 10% relative to 1974 production vehicles in the 2750-pound weight class is required to meet the statutory 0.4 g/mile HC level.

3.3.3 Effect of NOx Emissions Control on Fuel Economy Data showing the effect of NOx emissions control appear in Figure 3-~ 22 These data are based on modifications of a Honda CVCC-powered Civic vehicle (2000-pound test weight) to meet increasingly stringent NOx standards ranging from 1.2 g/mile to as low as 0.3 g/mile. For all tests, HC and CO emissions are within the statutory 1977 standards.

NOx control as shown in Figure 3-4 has been effected by use

of exhaust gas recirculation 1.n comb1nation w1th retarded 174

ignj_tion timing. It is clear that control of rmx emissions to levels below l to 1. 5 g/mile results in stgnificant fuel economy penalties. The penalty increases uniformly as NOx

emissions are reduced ~nd appears to be 25% or more as the 0.4 g/mile NOx level is approached.

It should be emphasized that the data of Fisure 3-4 apply

specifically to a 2000-pound vehicle. With increased vehicle weight, NOx emissions control becomes more difficult and the fuel economy penalty more severe. The effect of vehicle weight on NOx emissions is apparent when comparing the data of Table 3-I for 2000-pound vehicles with that of Table 3-II

for a 5000-pound vehicle. While HC and CO emissio~s for the two vehicles are roughly comparable, there is over a factor of two difference in average NOx emissions.

3.4 Fuel Requirements To meet present and future U.S. emissions control standards, compression ratio and maximum ignltion advance are li.mited by HC emissions control rather than by the octane quality of existing gasolines. CVCC engines tuned to meet 1975 California

emissions standards appear to be easily satisfied with presently available 91 RON commercial unleaded gasolines.

CVCC engines are lead tolerant and have completed emissions certification test programs using leaded gasolines. However, with the low octane requirement of the CVCC engine as noted above, the economic benefits of lead antlknock compoundt; ar-€· not realized. 175

It is possible that fuel volatLLity chara.cteristlcs may be of importance in relation to vaporization within the high temperature fuel-rich regions of the prechamber cup, inlet port, and prechamber iQlet manifold. However, experimental data on this question ao· not appear to be available at present.

~.O Divided-Chamber Staged Combustion Engines (Large-Volume Prechamber Engines, Fuel-Injected Blind Prechamber Engines) ! 4.1 General Dual-chamber engines of a type often called ''divided-chamber" or "large-volume prechamber" engines employ a two-stage com­ bustion process. Here initial r~ich mixture combustion and

heat release (first stage of combustion) are followed by rapid dilution of combustion products with relatively low temperature air (second stage of combustion). The object of this engine design is to effect the transitjon from overall rich combustion products to overall lean products with sufficient speed that time is not available for formation of significant quantities of NO. During the second low temperature lean stage of combustion, oxidation of HC and CO goes to completion.

An experimental divided-chamber engine design that has been

built and tested is represented schematically in Figure ~-1. 25 , 26

A dividing orifice (3) separates the primary combustion chamber (1) from the secondary combustion chamber (2), which includes the cylinder volume above the piston top. A fuel injector (4) supplies fuel to the primary chamber only. 176

Injection timing is arranged such that fuel continuously mixes with air entering the primary chamber during the compression stroke. At the end of compression, as .the piston nears its top center position, the primary chamber contains an ignitable fuel-air mixture while the secondary chamber adjacent to the piston top contains only air. Following ignition of the primary chamber mixture by a spark plug (6) located near the dividing orifice, high temperature rich mixture combustion products expand rapidly into and mix with the relatively cool air contained in the secondary chamber. The resulting dilution of combustion products with attendant temperature reduction rapidly suppresses formation of NO. At the same time, the presence of excess air in the secondary chamber tends to promote complete oxidation of HC and CO.

4.2 Exhaust Emissions and Fuel Economy

Results of limited research conducted both by university and industrial laboratories indicat~ that NOx reductions of as much as 80-95% relative to conventional engines are possible with the divided-chamber staged combustion process. Typical experimentally determined NOx emissions levels are presented in Figure 4-2. 27 Here NOx emissions for two different divided-chamber configurations 8re compared with typical emissions levels for conventional uncontrolled automobile engines. The volume ratio, 8, appearing as a parameter in Figure 4-2, represents the fraction of total combustion volume contained in the primary chamber. For a values approaching 177

1I i J_ 0.5 or lower, NOx emissions reach extremely low levels. How­ ever, maximum power output capability for a given engine size decreases with decreasing 6 values. Optimum primary chamber volume must ultima.tely_represent a compromise between low

emissions levels and desired maximum power output.

HC and particularly CO emissions from the divided-chamber engine are substantially lower than eonventional engine levels. However, further detailed work with combustion chamber geometries and fuel injection systems will be neces­ sary to fully evaluate the potential for reduction of these i emissions. Recent tests by Ford Motor Company show that the large volume prechamber engine may be capable of better HC emissions con­ trol and fuel economy than their PROCO engine. This is shown

by the laboratory engine test comparison of Table 4-I 19

Table 4-I Single-Cylinder Low Emissions _____En____g__~ne. __··11 _e_s_'-'_s~ _____

NO-X- Em:1.ssions, Fuel Reduction g/1 hp-Hr Economy, Engine Method NOv - HC co Lb/1 hp-Hr PROCO EGR 1.0 3.0 13.0 0.377 Divided None 1.0 0.4 2.5 0.378 Chamber

PROCO EGR 0.5 ~.o l 1i • 0 0.383

Divided None 75 3.3 0.377 Chamber o. J_o. 178

Fuel injection spray characteristics are critical to control of HC emissions from this type of engine, and Ford's success in this regard is probably due in part to use of the already highly developed PROCO-gasoline injection system. Figure 4-3 is a cutaway view of Ford's adaptation of a 400-CID V-8 engine to the divided-chamber system. 2 e

Volkswagen (VW) has recently published results of a program aimed at development of a large volume precharnber engine. 29 In the Volkswagen adaptation, the primary chamber which com­ prises about 30% of the total clearance volume is fueled by a direct, timed injection system; and auxiliary fuel for high power output conditions is supplied to the cylinder region by a carburetor.

Table 4-II presents emissions data for both air-cooled and water-cooled versions of VW' s dtvi.ded-·chamber engi.ne. 3 0 Emissions levels, while quite low, do not meet the ultimate 1978 statutory U.S. standards. 179

Table 4-II Volkswagen J.a.rge Volume _!Jrechamber Er!.[: Lne Emissions

Exhaust Emissions, _ _g;/Mile 1 .,___E_n_gi_n_e__t--H_C_,,__c_o_,._N_O_x__,,__E_n.....g__i_n_e_S_p_e_c_i_f_i_c_.a_.t·_1_·o_n_s__ 1.6-Liter 2.0 5.0 0.9 8.4:1 compression ratio, Air-Cooled prechamber volume 28% of total clearance volume, conventional exhaust mani­ fold, direct prechamber fuel injection 2.0-Liter 1,0 4.0 1.0 9:1 compression ratio, Water-Cooled prechamber volume 28% of total clearance volume, simple exhaust manifold reactor, direct prechamber fuel injection

1cvs c-H.

Toyota also has experimented w:l.th ___a large volume precha.mber engine using direct prechamber fuel injection and has reported emissions levels comparable to those of Table 4-II. 31

4.3 Problem Areas

,. A number of major problems inherent in the large volume prechamber engine remain to be 3olved.

I~ These problems include the following: I

Fuel injection spray characteristics are critically important to achieving acceptable HC emissions. The feasibility of producing a.satisfactory injec­ tion system ha.snot been estab1:i.shed. 180

Combustion noise due to high turbulence levels and, hence, high rates of heat release and pres[-;ure rise in the prechamber can be excessive. It has been shown that the-noise level can be modified through careful chamber design and combustion event timing.

If the engine is operated with prechamber fuel injection as the sole fuel source, maximum engine power output is limited. This might be overcome

by a~xiliary carburetion of the air inlet for maximum

power demand or possibly by turbocharging. Either

approach adds to system complexity.

The eng:i.ne is char·aeter1zed by low exhaust temperatures typical of most lean mixture engines.

References

1. Ricardo, H. R., "Recent Research Work on the Internal Combustion Engine, 11 SAE Journal, Vol. 10, p. 305-336 (1922).

2. Bishop, I. N., and Simko, A., Society of Automotive Engineers, Paper 680041 (1968).

3. Simko, A., Choma, M. A., and Repco, L. L., Society of Automotive Engineers, Paper 720052 (1972).

4. Mitchell, E., Cobb, J.M., and Frost, R. A., Society of Automotive Engineers, Paper 680042 (1968).

5. Mitchell, E., Alperstein, M., and Cobb, J.M., Society of Automotive Engineers, Paper 720051 (1972).

6. "1975-77 Emission Control Program Status Report" submitted to EPA by Ford Motor Company, Novembe.r 26, 1973. 181

'if

7. "consultant Report on Emissions Control of Engine Systems," National Academy of Sciences Committee on Motor Vehicle Emissions, Washington, D.C., September 1974.

8. Austin, T. C., and Hellman, K. H., Society of Automotive Engineers, Paper 730790 (1973).

9. See Ref. 7.

10. Alperstein, M., Schafer, G. H., and Villforth, F. J. Iiil, SAE Paper 740563 (1974).

11. U.S. Patent No. 2,615,437 and No. 2,690,741, "Method of Operating Internal Combustion Engines," Neil O. Broderson, Rochester, New York.

12. Conta, L~ D., and Pandeli, American Society of Mechanical Engineers, Paper 59-SA-25 (1959).

13. Canta, L. D., and Pandeli, American Society of Mechanical Engineers, Paper 60-WA-314 (1960).

14. U.S. Patent No. 2,884,913, 0 Internal Combustion Engine," R. M. i Heintz. i 15. Nilov, N. A., Automobilnaya Promyshlennost No. 8 (1958).

16. Kerimov, N. A., and Metehtiev, R. I., Automobilnoya Promyshlennost l No. 1, p.8-11 (1967).

17. Varshaoski, I. L., Konev, B. F., and Klatskin, V. B., Automobilnaya Promyshlennost No. 4 (1970).

18. "An Evaluation of Three Honda Compound Vortex Controlled Combustion (CVCC) Powered Vehicles," Report B-11 issued by Test and Evaluation Branch, Environmental Protection Agency, December 1972.

19. "Automotive Spark Ignition Engine Emission Control Systems to Meet Requirements of the 1970 Clean Air Amendments," report of the Emissions Control Systems Panel to the Committee on Motor Vehicle Emissions, National Academy of Sciences, May 1973.

20. "An Evaluation of a 300-CID Compound Vortex Controlled Combustion (CVCC) Powered Chevrolet Impala." Report 74-13 DWP issued by Test and Evaluation Branch, Environmental Protection Agency, October 1973.

21. See Ref. 7.

22. See Ref. 7.

23. See Ref. 7.

24. See Ref. 7. 182

25. Newhall, H. K., and El-Messiri, I. A., Combustion and Flame, 14, p. 155-158 (1970).

26. Newhall, H. K., and El-Messiri, I. A., Society of Automotive Engineers Transaction Ford 78, Paper 700491 (1970).

27. El-Messiri, I. A., and Newhall, H. K., Proc. Intersociety Energy Conversion Engineering Conference, p. 63 (1971).

28. See Ref. 7.

29. Decker, G., and Brandstetter, W., MTZ; Motortechnische Zeitschrift, Vol. 34, No. 10, p. 317-322 (1973).

30. See Ref. 7.

31. See Ref. 7. 183

F'ig. 2-1 FORD PROCO ENGINE

l Ford Proco Engine Fuel Economy and Emissions

_ 15, /:._ f--1 00 +' I ~ x X >( X '';_' ' x ,, A 7- ~, X x~ ■ ~c - l.4}catalyst Feed u / NOx vs ruel Econ. with 1/ C0-7.1 CJ) , , x x Ynn H(' RP c:. tr ir-t irm 14 v<>Z/ _G I A HC t.xcess,ve- . / C0-12.7 c., Approx. W / EG R/ 13 ~ C~~r. ■ 351 CID, 5000 Lb Inertia Weight

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AIRBORNE SURVEYS IN URBAN AIR BASINS: IMPLICATIONS FOR MODEL DEVELOPMENT

by

Donald L. Blumenthal Manager of Program Development Meteorology Research, Inc. Altadena, California 91001

·I would like to make several points today. First, ozone·is basically a regional, long-range problem. There is a lot of long range ozone trans­ port and this transport is a normal occurrence. The second point is that ozone is stable in the absence of scavengers; Junge mentions in his book that the residence time of ozone in the troposphere is on the order of a month. Third, vertical variations in concentration and ventilation rate are i very important in modeling atmospheres such as Los Angeles. Layers aloft are ventilated down to the surface on occasion, and surface pollutants are ventilated up mountain slopes, as Jim Edinger has pointe.d out before, and often ventilated out of the basin in upper winds. Fourth, the day to day carry over of pollutants from one day to the next is a very important consid­ eration in the Los Angeles Basin. Finally, there is a definite background level of ozone. The geophysical literature says it's about O. 02 to O. 03 ppm ( in various parts of the world. We've seen data varying from 0.03 to 0.05 ppm.

The difference may be due to calibration differences. In any case, numbers like 0.05 are pretty substantial background levels for ozone.

I am going to illustrate the points listed above with some data from

Los Angeles Basin. The data were collecte.d during a two-year study funded by the Air Resources Board; some of the. analyses were funded by EPA. The study examined the three dimensional di.stribution of pollutants in the Los

Angeles Basin, using airborne sampling systems. Coinvestigators on the project were Dr. Ted Smith and Warren White of Meteorology Research, Inc. (MRI). 197

The first slide shows one of the aircraft we used. It's a Cessna 205 wh.:ich had sampling inlets on the side of the aircraft. Figure 2 shows the

instrument system on the inside of the aircraft. We were measuring nitrogen

oxides, ozone, scattering coefficient with a nephelometer, condensation nuclei,

carbon monoxide, and meteorological parameters such as temperature, humidity,

turbulance. Altitude and position were also measured.

Figure 4 shows that the typical sampling pattern was a series of spirals

from the top of the mixing layer over an airport virtually to ground level;

then we would climb up to the next point on the route and spiral down again.

We had three routes (A, B, C, Figure 3) that we would fly. We had two air­

craft and we would fly two of these three routes three times a day. any

given day that we could. The day I will be talking about, September 25~ 1973,

we flew what was called the Riverside route, (C), and the Los Angeles route

(A). The 25th of July, 1973, you might remember, was the day before the

federal office buildings were closed in the area here because of smog.

Figure 5 shows the surface streamlines at 0300 Pacific Standard Time,

about 4 o'clock in the morning daylight time on July 25. This streamline

analysis points out the morning stagnation conditions which are a very normal

occurrence in the Los Angeles Basin. You start out with very light winds,

quite variable, maybe a slight off shore flow early in the morning. On this

particular day this kind of situation extended well into midday. The sea

breeze did not really pick up until up around noon. When you have this kind

of a situation and a low radiation inversion at night, you have a

long period of accumulation of pollutants all over the Basin., espt~cialJy

in the prime source area, the southwest portion of the Basin. 198

Figure 6 shows the streamline pattern at 1600--4:00 cc.lock in the

afternoon, same day; sea breezes develop and with them a transport pattern

that carries pollutants up to the northeast and out toward the eastern por-

tion of the Basin. This is a very regular pattern which we see day after :l '· day. On July 25, 1973, it was a little bit exaggerated. The sea breeze was

held off for awhile, started a bit late, and so there was a very long period

of accumulation in the southwest area and then transport across the Basin. I Figure 7 is an average streaml.ine pattern at 1600 PacHic Daylight Time on low inversion days for August 1970. It is included to show that the pattern

shown before is very typical. Flow starts in the western portion of the

Basin, and goes right across to the eastern portion. This is using surface

data. There is a very high average wind velocity in Ontario, about 13 m i.le.s

per hour, and 23 mph in Rive.rside. This is the average for the whole month

of August, at 1600 PDT on low inversion days. There is a considerable amount

of transport across the Basin, starting relatively slowly in the morning and

accelerating in the afternoon.

Figure 8 shows a verticle cross section of the scattering coefficient.

The darker areas indicate higher levels of particulates. Scattering coeffic­

ient is inversely proportional to visibility. In the crosshatched area,

visibility is less than about 3 miles. In plotting altitude. versus distance

inland from the coast you have Santa Monica (SMO) on the coast, El Monte (EMT)

Pomona (BRA), Rialto (RIA), Redlands (RED). The lower broken line. is surface

ground level. The heavy dashed line is the base of the. subsidence inversion

that occurred on the two days during this episode. The middle line is the

base of the marine inversion. There is a large area over in the western

portion of the Basin where emissions accumulate for much of the day. At 199

midday, the sea breeze has just started ventilating the Santa Monica area.

The layer between the inversions is a layer aloft which is fairly well separ­ ated from the surface layer. Ozone concentrations, for instance, in the layer aloft were on the order of 0.4, 0.5 ppm, using the ARB calibration method. Down in the surface layer they were quite a bit lower in the morn­

ing due to scavenging.

Figure 9 shows that by afternoon, the sea breeze starts and you get kind of a clean air front. Sea breeze starts ventilating the whole Basin,

the stuff that was over in the west is transported eastward, and at approxi­ mately Brackett (BRA) at 1700 PDT there is a clean air front. The high con­ centrations that were over Los Angeles earlier are now centered near Upland

(CAB). The numbers shown over CAB are data taken from a vertical profile spiral over Upland at about 1600. That turns out to be the time when there was the worst ozone concentration of the day in the Basin and it did occur at Upland. It could well be a result of the very polluted mass from the western Basin being transported over the Upland area. The layer aloft has been a bit undercut by the sea breeze and some of the polluted mass has been around possibly as long as the night before. There has been very little

transport in the area aloft; ozone. concentrations are still very high.

Figure 10 shows a trajectory analysis of the air arriving at Upland at

1600 since that was the worst time of the day at Upland. We developed a

trajectory envelope using surface wind data and winds aloft, so the air arriving at Upland at 1600 started out somewhere back within this envelope,

for example at 11:30 PDT. We did not go earlier than 11:30 because the winds were pretty much light and variable before that. The air that arrives at

Upland at 1600 has been over the western portion of the Basin for much of 200

the morning and q~ite a bit of the evening before. Thus, there is

a very long period of accumulation and then a transport, a pulsing effect where you have pollutants moved across the Basin.

Figure 11 is an isopleth map of surface ozone concentrations. Again, all

data are corrected to agree with the ARB calibration method. Again you can

see that for the hours between 1600 and 1700, using surface data, the Upland

area has the highest surface ozone concentrations, about 0.63 ppm. The western

area has been well ventilated by the sea breezes, and it is cleaned out.

The transport is actually pre.tty much perpendicular to the isopleth line

just about like that. Figure 12 is a vertical profile taken over Upland, Cable Airport,at I roughly the time of maximum ozone concentration,, 1636 PDT. We are plotting

pollutant concentration on the x-axi.s ve.rsus altitude in meters (since it was

done for an EPA report). Surface leveJ at Upland is a little over 400 meters;

the "Z" .line is ozone. Ozone concentration within the surface mixing layer

is pegged on the instrument at somewhat above 0.5 ppm. Above the surface

mixing layer it drops off considerably and eventually get down to background.

The "T" line is temperature, and you ean see the subsidence inversion

on this day is ve.ry nicely documented here, and provides a very strong trap

in that area. The "B'' line is the scattering coefficient, inversely propor­

tional to visibility. Within the surface mixing layer, visibility is on the

order of 3 miles or less, while up above the surface mixing layer, just a few

hundred feet difference, visibilities get up to 60 or 80 mi.les. The "X" is

condensation nuclei, the measure of the very fine particles below about 0.10

micron. It i.s a measure of quite fresh emissions. If you have a high conden­

sation nuclei count, there are very fresh combustion emissions. If you have 201

an aged air mass, the condensation nuclei coagulate and the. count decreases

considerably. You can see .that there are still some fresh emissions within

this surface layer as well. But up above the surface mixing layer all the

pollutant indicators decrease considerably.

Figure 13 is the same type of vertical profile taken over El Monte, which is on the western side of the sea breeze front. The sea breeze front has passed El Monte at this time, almost 1700 PDT, and again there are

distinct differences between the mass below the mixing layer within the sea

breeze front, (below 400 meters), the marine inversion (400 to 800 meters) and

the subsidence inversion. The subsidence inversion occurs at about 800 meters

and there is an old layer of very polluted stuff a.loft. The surface concen­

trations are lower because of the ventilation by the sea breeze. Condensa­

tion nuclei count ("X" line) within the surface layer is quite high. There

are still fresh emissions in the El Monte area. The 11 Z" line is ozone,

about 0.2 ppm within the surface layer (200 m), but it is 0.5 ppm up above

the surface mixing layer. The scattering coefficient ("B" line) is very

similar; it is lower at the surface and increases to a visibility equivalent

of less than 3 miles above the surface mixing layer. The condensation nuclei

count is high in the lower portion of this (e.g. at 600 m) hut decreases con­

siderably above. This portion of the upper layer (600 m) has been around

at least all morning, and condensation nuclei have been scattered from the

area. The portion of the upper layer below 600 m has probably just recently

been undercut by the sea breeze, and there are still some condensation nuclei

left in it.

Figure 14 illustrates a different method of looking at the flushing

problems in the Basin. We have tried to develop an objective criteria based

on ground level ozone to show the cleansing of the basin, using the time of 202

arrival of clean air. We determine the time when the ozone concentrations drop by a factor of two at any given point. The 1600 line means that between

1500 and 1700 the ozone concentration at that point dropped a factor of two.

This sort of isopleth chart of when the clean air arrives agrees quite well with the trajectory analyses, although the numbers are. a little bit behind the trajectory analyses for the polluted air. Figure 14 again shows the transport process that takes place across the Basin, which is ventilated from west to east. At 1900, some of the fresh ocean air fi.nally gets out to

Redlands.

In Figure 15, in order to put this whole flux problem into some perspec­ tive, we looked at the numbers., the actual amount of ozone flux across the basin. We calculated the mean trajectory from Torrance towards Redlands, using the surface and upper air data. We looked at the flux from the western basin to the eastern basin, basically from Los Angeles and Orange Counties to

Riverside and San Bernardino Counties. This is a calculation made at 1700 PDT.

We used the winds aloft from Chino as well as the vertical profiles taken at

Pomona and Corona. Averaging the ozone concentration throughout the mixing layer and multiplying by an average wind speed, we arrive at a number of 185 metric tons per hour being transported directly from one side of the Basin

to the other. If you look at this in terms of actual concentration in the eastern Basin, and assume that the flow was constant for about an hour, it

is eno_ugh to fill up the box shown in Figure. 15 to 0.25 ppm ozone, which e.xceeds the air quality standard by a factor of three (usi.ng the ARB calibra­

tion me.thod). Thus, there is a very significant transport of ozone or ozone precursors from one portion of the Basi.n to the other side of the Basin. One

thing to mention, though, is that the concentration would not be kept up on a 203

steady state basis because the transport is a result of the pulsing effect

I Illentioned earlier. There is a lot of accumulati6n in the western Basin, and these accumulated pollutants are then transported across the Basin. This kind of transport did take place in a couple hours, because we also have measurements from 1500 PDT which give us similar flux numbers.

Figure 16 is a trajectory envelope similar to Figure 10 calculated for

Upland at 1600, for the air arriving at Redlands about 6:00 o'clock in the afternoon. I wanted to include this trajectory envelope to show that the problem is not really simple. You cannot say that the air at Redlands came from Long Beach, per se. The air at Redlands, if you look at the whole envelope of possible trajectories, using upper air data as well as surface data, could have come from anywhere between Downtown Los Angeles and over the Pacific Ocean south of Long Beach.

Another thing to recognize is that the wind actually changes direction slightly as you go up and down through the mixing layer and the mixing layer is exactly what it implies. There i.s mixing within the mixing layer, so if you begin with a parcel of air near the surface, this parcel may move to the top of the mixing layer and go one direction for awhile; it then may go back down to the bottom of the mixing layer, and move in another direction for awhile. The ratio of the length scales indicata3mixing layer depths of 1500 or 2000 ft., and distances on the order of 70 miles. This makes it very difficult for tetroons to follow an air trajectory, because they do not go up and down. They stay at one altitude and in one wind regime, and yet the wind regimes are different at different altitudes, and the air is continually mixed up and down through this layer. You can often see this on time lapse photographs. 204

The question is where does the pollutant mass go after Redlands. Figure

17 is a repeat of Jim Pitts' slide from yesterday, and it is data for the same day that we did our analysis. It shows the ozone peaks, starting at

Pomona and Riverside, and on July 25, 1973 eventually getting out to Palm

Springs, so there is quite a bit of long-range transport. The ozone is stable at 8: 00 or 9: 00 o'clock at night. The.re. still are ozone concen­ trations of 0.2 ppm; it hasn't dissipated even at the surface. O.zone does dilute as the mass moves. Other calculations we did were integrations through the mixing layer of various pollutants, such as ozone and CO, along with trajectories that we measured. Th~se integrations show just what the ground data show in Fi.gure 17. The concentrations increase through the western portion of the Basin, and then show a decrease through the eastern portion of the Basin. CO tends to decrease faster than the ozone, indicating a continued production of ozone further east.

Figure 18 is a streamline chart on a larger area map for the 16th of

August, 197.3. It shows the t'ypical streamline patterns that occur for ventilation from the Basin. By mid-afternoon there is flow out through the major passes, to the north, and towards Palm Springs (PSP). On this particu­ lar day we had data from Arrowhead showing that the air mass from the Basin does indeed get up there.

Figure 19 shows a vertical profile over Arrowhead early in the morning,

16 August, 1973, at a time when there. was a north wind. Ozone level was about 0.05 ppm, the scattering coefficient was quite low, on the order of probably 60 miles visibility or so. Figure 20 is a vertical profile again over Arrowhead late that afternoon when the winds had switched. There is a flow from the Los Ange.les Basin i.nto the Arrowhead area; thus, one sees a 205

vertical profile that shows a distinct increase near the surface in both the ozone and the scattering coefficient, and in the condensation nuclei. Ahove that you have fairly clean air. The top of the polluted level is just about the top of the mixing level over the Basin.

I want to leave the transport now, and discuss the complicated vertical structure that can occur. If you want to try to model something, try this one for instance. Figure 21 is a vertical profile over Brackett Airport,

Pomona, about 8:30 in the morning on 26 July, 1973, which is the day after the episode shown earlier. A bit of interpretation shows how complicated this can be. If one looks at the. temperature profile, it would be very difficult to pick out a mixing layer; there's a little inversion here, another inversion there, several more up here. After looking at hundreds of these profiles, though, you can start interpreting them. What is happening is that there is a surface mixing layer at about 500 m. In this layer, there is a high condensation nuclei ("X" line) count due to morning traffic. The San

Bernardino freeway is quite close to Brackett, there is a relatively high nitrogen oxide count about 0.2 ppm and the b-scat is fairly high. Ozone ("Z") within the surface layer, however, at this time. is quite low. The layer be­ tween 500 m and 700 rn turns out to be the Fontana complex plume. Note the very high b-scat level, it is below 3 miles visibility; the plume is very visible, especially at this time of the morning when it is fairly stab]e.

There is a high nitrogen oxide level, (800 m) a high condensation nuclei level, and again a deficit of ozone. Above this layer (800 m) you have stuff that has been left all night, very low condensation nuclei indicating a very aged air mass, ozone concentrations about 0.16 ppm, b-scat of about 0.4. It has been around all night and not yet had a chance to mix down within the 206

surface layer. In fact, one good way of determining the surface mixing layer

early in the morning and at night is to look for the ozone deficit. Another

thing to mention is that wind reversals occurred for each of these three

layers. The winds were fairly light and westerly at the surface, slightly

easterly in the 500 m 700 m layer and weste.rly above 800 m. There is a

complicated situation early in the morning, but the main problem is that by

the middle of the day there is good surface heati.ng, and the pollutants have

all been entrained and mixed down to the ground; so in order to mode.I what

happens on the second or third day of an episode, you must be able to look

at both old pollutants as well as fresh emissions. And you need to account r for ozone that is actually transported down to the surface from laye.rs aloft. l The next slide is a photograph (not included), which is another e xampl.e

of some layers aloft. This is due. to upslope flow as explained by Jim Edinger

in his publications. The mountains are heated during the day, in turn heating

the air and making it buoyant; there is upslope flow to a point where the

heating cannot overcome the subsidence inversion, and the stuff comes right

out from the mountains and spreads out over the Basin. The pollutants can

stay up there if the winds aloft are very light and on the subsequent day

will he re-entrained to the surface. On the other hand, if there are winds

aloft different from those in the surface mixing layer or the wind velocity

aloft is high, there can be a very substantial ventilation process for the

Basin. Pollutants can be ventilated up the slope and blown away in the upper

winds. In the case of the entire July 25th episode, winds aloft were quite

light and these upper layers remained.

Figure 22 is a vertical profile of one of those upslope flow conditions,

in the same location shown in the photograph, but on a different day. Again 207

there is a relatively high surface concentration of about 0.3 ppm of ozone

("Z" line), a layer of clean air between 900 to 1100 m, and then high concen­ trations of ozone again above 1100 m. It has gone up the slopes of the mountains and then come back out. Concentrations in the 1100 to 1300 m area are just slightly lower than they were at 600 to 800 m area. Notice, however, that the condensation nuclei count ("X" line) is quite a bit lower, mainly because the stuff is much more aged above the 1000 m level than it is down below 900 m.

Figure 23 shows the stability of ozone, the fact that it can stay around all night long. This is a vertical profile taken over Riverside about 2200

PDT, 10:00 o'clock at night. Above the surface mixing layer (600 m) there are ozone concentrations of about 0. 15 ppm ("Z'' line). Within the surface mixing layer (below 500 m), ozone is completely scavenged, decreasing to zero. The nitrogen oxides within this surface layer are being contained, and are around 0.1 ppm from fresh emissions that occurred during the evening.

Condensation nuclei near the surface are very high. The temperature profile is very stable. You have a surface based radiation inversion, which is a little strange looking for a radiation inversion~ nevertheless it is quite stable. There is a definite restriction of the mixing--a very difficult time getting air from below 500 m to above 500 m. The ozone that exists in the 700 m range is in air where the reactions have virtually gone to comple­ tion ,and is very stable. All the profiles on this night changed very little; the ozone peak stays there. High concentrations stay around.

Figure 24 is a cross section across the.urban p.lume of the City of St.

Louis. I wanted to show that this occurrence is not limited to Los Angeles.

We have seen ozone formation and transport in other urban plumes. These data 208

were taken during a project sponsored by EPA in conjunction with R. Husar of

Washington University and William Wilson of EPA. The dark line on this is

the ozone concentration across the urban plume, perpendicular to plume. The

dashed line is the scattering coefficient. The power plant plume is parallel

to the urban plume. The data on the left were taken 35 kilometers down wind

about 11:00 o'clock in the morning. The ozone concentration increases slightly

to 0.05 ppm in the urban plume; there is a defici.t of o in the power plant plume. 3 In the same urban plume, same conditions, 1500 CDT, two hours later, further

downwind, there has been substantial increase in the ozone in the urban plume

itself. The b-scat is very similar to what it was before but the ozone is l now increased quite substantially, except in the power plant plume where there is a strong deficit of ozone due to scavenging by nitrogen oxides. So

the formation and transport of ozone and ozone precursors in urban plumes is

a regular occurrence that happens in more places than Los Angeles and, as Bob

Neligan showed this morning, it can happen over quite a bit longer distances

than we are showing here.

To summarize the conclusions as they affect model development, first,

once ozone is formed, in the absence of scavengers ozone is a very stable

compound. It remains for long periods of time. It can he transported for

very long distances. Ozone is a regional problem which cannot be controlled

on a local basis. To have effective ozone control ·one must have a regional

control strategy and probably regional type air pollution districts.

A second conclusion is that the vertical distribution of pollutants can

be highly complex and models have to include more than just a simple well­

mixed surface layer. 209

A third conclusion is that layers aloft can persist over night and can be re-entrained within the surface mixing layer on subsequent days; models should be able to account for old pollution as well as fresh emissions. Also pollutant accumulation and transport can have distinct diurnal patterns that are strongly dependent on the meteorology. Models should be time dependent and should start at the beginning of the accumulation period. In other words, models ought to be able to run for 24 or 48 hours if they have to. In this case, in Los Angeles, there is often an accumulation of pollutants which starts in one portion of the Basin at midnight and continues through the next morn­ ing even before it starts to be transported.

As far as re.commendations go, in many areas a lot of ambient data has been collected, and in some cases the data are actually ahead of some of the models, so I think a research program is needed in developing models that will account for this vertical structure and the day to day carry over, and the models need to be extended to cover longer distances. In addition, more smog chamber work is going to be needed in looking at the effects of carry over and mixing old pollutants with fresh emissions. How people go about this, I leave to the modelers and the smog chamber people. They know more about that than I do. 210

I __ \

~ ·E=-· INVERTER AUDIO TAPE RECORDER ----r------CO MONIT0R 03 MONITOR OBSERVER SEAT N°" MON ITOR lNEPHELOMETFR F.LfC.TRONICS j

DIGITAL DATA LOGGER CONDENSATION NUCLEI KJNITOR VOR / DME CONVERTER - NEPHELOMETER TUBE JUNCTION ·eox ASSORTED POWER SUPPLIES

AIRBORNE INSTRUMENT PACKAGE: ( I TEMPERATURE TURBULENCE · HUMIDITY ALTITUDE -----NEPHELOMETER BLOWER BOX

Figure 2. Instrumentation Layout for Cessna 205 211

•u••"••

Figure 3. Airborne Sampling Routes in the Los Angeles Basin

Figure 4. Vertieal Profile Flight Path .;...~-~ r~,.:;;;i,,, ~~1 ,-.::-; ~ ~ ~'2-1~ ..L..J-----~ r'~~ ~~ t::~~--'l

ec 8v

0 M RIA ~ ~ ALM l Afo

-o

M 0 ~IV

~ <>

M SCALE II f\i M I j_ ES N~J 0 ' ' 3 4 5 .,, =.-JS E.J--J~ _·.. ~.·-. - =:- =::: IN J,--1 I N

Figure 5. SURFACE STREAMLINE ANALYSIS - 0300 PST 25 July 1973

~~~ ~~-- ;c;;p;1/FJ=D -.....~~ ~ 1?' ~~. 8c 8v

~25

PACIFIC OCEAN

♦ \ ! Tt. 0

. :p H 95 10 I I"-- m, -·· u 4H.,,.__8 ·t_ i6 J4 k /4 W!~D SPED l«tl SNA N?J ~1 SCALE m IC.t,t84•m/h, R; " v1s1a1L1n (mil 6 ~ . CONTOURS REPRESENT D -- 10ml: 16km (~(/) • ~ \) ~ - !000 ft, 3C5"" Figure 6. S_:cJRFACE WIND STREAMLINES - l 600 PDT, JULY 2 S, I 8 7 3 ,t:;~~- .l - ~---"":i, ~-=-.,::;;___.-----.:c..,---i p.c---,_t..,__A .--~ ---llil ~~ r----=----.::--;1 ~-~"~--c!

•••• • • ~ ., • I -1.. ' •• ,-. -_- L • •-.'\.J .• .. \ ~•-•-::ii,--!--,--~ .... : •· ..r:,,_ -~- ~ •I ;_. ~\.,_,; - •'" • • ! ,•• ■ -~-~ ·••• ~ .. ~ ;--· -~- .••· ~v \.') ~ - . ,. -.,._,,_r\l v ··' - 1- ~ -- · ·· , -. 1 91 '½ - ~- .....<,\\( · K i - ' · •, - ·. - •· ~~-:~;.,.,:.l,J) o'•,·~ ~-f'-' ,!!'_,"J._~-..;:-:-:S·~·-:}:.~----~~~--:-/::::,>_:·fY-_:·-~:'.;· --:.,.·.-~-~--'.--:f;::{;.J_·-:, ::·:·•.·:: 'u-- •.· ~ ~ -·, .. L~\.. r -- •• ~•••.• •• l_'• • :.••• "EW , ••••-;.-:. . ~ \_...... ,_.•, ,,.,.f f .\.. - ·• ,-..,. J ,,. " '· .,.f/ . . • ' . S.., . . ' • I ~ - ' ,._ •• •':- _ ,; , ••-• .~ ~ • • , • ' '" , • I • • • • , , • , ; • > . .-. • ·•iJ ,-.!• I • • ._1 \ • \"J C"""--,... ~\'-· ._ .• •\•' •• • _,__ __ ,~ ~ l ,.,,._, · q ,'• 1, -· ·'/'~/'""~·, · ·•_,:' J,, ~'.....:> \ - J .., •-.•••• ,) . _. ,..,:-··•· :'.J ~···'.:. -•·• f· . 7· ...... ::,_···: . ..:' .:, •·:(,.,·. ! . Ii~ ··~:._--~· 1:·;.:.._;'"_,·;··· '\·- ,,...>_ . -:~ -~--:\ ! ."'I.;·•·••._: - '- ()_,.\'I;:,, . (,w:.--.,._ ••__(i- .. , .•O·•\ ;•..., ·• -.•-,\'.,_jlJ ,' ·' • '<',.,. ,'1(· 't.. "> • -: ;~\ r• I .. •. ,: '·, ·- ...... •,4 ,1:-• l.,;~r ""'v-·~- · · · .,•_ - ,·· :.~...Jtj (.·~\ ... ~·i · · · ,....!. · · ~- ..: ~ -t·~ .I -' · ·_- ~.: ., -.:, .-~ ·_ ,_- ' ., . • \ - ...... _. ~'\) ...,i\ "• •• •-.. : ; ·_ • :·• _._ (', • 1,1• • ~,&.· ,~ l ., • •.Q • - ' " ,-1 • JY1 •• ~ or..., •••••, ••.-•,• , .;._;~ ~ ....., "' '- • •-•••, .. ·,i· : \· 9'1 .• t • - - "'tfaw:.,, l'"''"J;--r- : • ., •, ,._ • ·- - ', l f\. ...~~·--~ ...... LOS .ANGELES BASIN - LOW LEVEL ..... -;:::__ j ·' l,-> ,.. • , '··t -//.~··:.J\.:·_•,::. , , • , ,J - ;~'i'I •• -. ,;\ __ ., ·- ,.. • • • ..._ ••_., . . .. ' \J;· ·;L~{_1. · · . . . : .••· (: C'' ·: INVERSION MEAN WIND FLOW . _. .J l· -. .f.' •••~ - f 1,••• ",;;,_ ./ \ ~..)- ""• .../ ·-. ._--;-,_,:::;-: '7'.f.:-~•':""~ REGIME _F_?~ AUG_UST_~! ~600 P~.:"'--- .... , .l .. -....__,,.L,,,..-~• --nc·•~~-j--•·~•·_-..• ,;_f,Ji•· I.:"···-•·- •• ~ ••••·::··~·'• ,._,.,__ ~0).) •J\_ ,,,:_:· 0 . °' •• °" '--=\:•,t;'. ''.t.1¥s··• • • ( ....I '·, • ,.·· • • · \ · • ~ • .· '. , l..••:1 /\ : • t_.c •,• -·---l • •• :_,. <..\ ~·~- ;::..~• ""b ---) '••-• ) '•'l,' ·•, ·1· ) . •T' '.'. --f .• I •r. ,', ~,••...• •••( - ..-•--. \ ; (: -o:-:-:--::..:,,.-_..i ..•-~\-l.'I:: - ,.i' l. l J ! "l'~--:? c ....: . ...,·· {.... :·· , ----✓ _,.--1 --- ..... ~•-• •i_ ALT El.,·,._ .•••.•. _-,.,.., ~~· • ·' ••. ._ .•. ·• •~ {.{ /~'• , ·, • ,-·! '.,.•-.-u,a_,.,-- .•• •. ; . --. . . 01.---"\:.: ·_ .:-·:.'· h·· __1 ~--.? ~:. fi.~~- ."'....,...___ - ____ ,._...... -····~ ) -~"'-J.:... . • . .•• •. . .. • 0 .,u,c,-... - l ~-:. ~ IT ,.;~~ll .. : ~ • ;;;..-· {.,,-····•,,.CCA···.-· · ••••• ) :.'i"-... .5 ~-==-- ,.,__ __ - ••• _.::... •~ , •• .,_ • •' :! l T[h4 '--":---..- -. 0. i/'17- o~-< -(i-:._\~ 11t~•-o· ~- -- ., 13 0/l~

,•,: J,,••~• \~•••, ;• • x- • -=:a.J'lll8' • • ·• I r •:~---.•~~• · 1.-....~·.-;· ..~ ..,. _ ··.·-· ., ·~---=-~~ 1. 0 ~~~vr.•· ~ ..~ ,'(}J~:-::.· :_-_.:,~) ) .. ~ . • ·, ... :.,~_ - ... ~-l.-.cL l .·.. .. _. POMA_ ·. . =::~~~-?,---ti~ "'j'··· . - 34• vi/~-d.::::ff , ·• . [j

:ii J 0'~\ Vfli \A:· •Hud, ....,.,_...,_=b,.t.:_ ;{ //,. • CI·,., ~--.... ~- ·,,.)· PACIFIC OCEAN I ·:. .---- . ·;::::· ~ ::__ ...... ·,.__ "\'"" ~: .....' .- _ / 23~1 ': .·• 8 . 4 1 .· · ., ~ : ' ·· > ~~- l :" ~..., u. ::· 1~ ,i .···. • .- .. n - •- .... _\'c" I - ~------. 118 11 "30' ,, :~ n r -t :;;~~>2,..:\5) c·•· # ~--<-: '\ ; ,:'\ ... ~~-\ / 1\.. ,-~'?...... __,,( .. "i - ,t ~ ._. ', \ ·. 0 (_,J i>

11• •11' ELEVATION .:~}~ -'\~:;,[?' ~i~>---.->:····--~l_ ~~ IN FEET ••. (...:_-... ·, ••• ,/. "-·' ·• '·; ~~ ··, \:, •,,t••.... _/f f··-· v ... ,: I \ )ty<~: -~••1.••.:.r•• ~-< ;-~ ( }: I~! 600~ A',0 Cv(A (1829 m AND OVER) '°''\ . )_ , rJ,.::_.._,~,/'"7 ,,· ; , ~--'·,,.. ·.. , L==:1 .,_J ••• - • ..... , . -·::::~.-- r,.> ~ \ ·.(":Z·- .·•· ·. Z~C,)-t;GOO (762 · 1829 m) 9-,N4 __J. ',. (r '. ,.:' -::,,..- lf . '\_ •.• ,>:-~~~ ~ \ L:.-•·•W •••3 STA r I0'-4 l'!ODEL _., w :: ,,.._..../ _ ,I (1 '•·'( ; ,. ·"1 · { ,; '-----~~~- ·.... 100.:i -2soo (305~762m) --.. -...,~1,.._;.:':-, "i , ~~--- .. ,;• ~'~ II Ow -' v~rvt: 1 )~ .-· )') .: ~--... , 0 Mo.;r nu:q1ENr Wl•~O JIAt:CTIO-. ,.> J, (..-,'._;''"•· ..:·.~\ l •', • tr \ ,... I-· -· •~ • • - 3 > .:. ).. '••-._• 2,0-,0.:0 (61 • 305 ml l""• C---> . f I " ,. . -',, •• )t'.. ••.. .-( I • J( Jloa x.x E- -••00 - -- ·1 0-200 (0·61m) Wl)7 AVB:t~g£ ) •,·-.:,ii,NL~}/,\ ·nt/·,.._,,,,. 1: i;,JJ<(;, ..:_1J"-' \ ~ VAq IA9 IL ITY 0 ~ 10 15 lt'S lHPtl. {~.-;-:;_: • • ,I . •••• :1 ~). J)J/: ~ ,; \ ' .• / Is ,,•· ••.•.•• ~ ::3 V IS A VAqlABLE OIR~CTIO-. 0 8 16 2-4 km SCALE (SPEEDS SHOWN IN mph, 10 mph• 16 h1/llr) -- ·. '}kt::\r~~:\~ \\ .;,/<~ \.'), -·-,

Figure 7. LOS ANGELES BASIN MEAN WIND FLOW FOR DAYS WITH LOW LEVEL INVERSIONS DURING AUGUST I 970 AT 1600 PDT -~~~~-======~·~-~======~·-..-"""'.....='"'-"==-===>=.....---==""'"'""'"'...... ,...... ______.._,....._,__""""'"""=== ~,--=,-J~==-- -=-ee----=------N f--' V,

--- SUBSIDENCE INVERSION ----MARINE INVERSION ••-•-••GROUND LEVEL /x WINOS .ALOFT (km/ht)

WESTERN ·eASIN EASTERN BASIN

LAX WINOS EMT '#IHOS CNO WIHOS I I ,s...... _ 0.4 1.3 1500.- 0.5 : 0.2 0.8 I 0.6 0.6 9, 1.-- ·, 11- 0.4 ; 0.4 ~''4 0.6 i ~ I '4-- /' 2 1000 0.5 \ n,1. 1.0 ~11 -_..E l....ll ' ".. , --1. lJ --=i-+ '"C ------~----" c ..-- . 9 _____::::..:::: - ~ ...... I < I 6. 4 _,...r 31 500 I 6 5 ~~ /~_...• ...:..---·-. 6.4 . / / ...... /~l,,i'-. - - ·-·------' •.,c. 10

SMO EMT BRA CAB RIA RED (13:47 PDT) (12:46 PDT) (14:59 PDT) (13:35 PDT} (13:49 PDT) (14:06:PDT)

Figure 8. VERTICAL CROSS-SECTION OF bscat FOR lvflDDAY, JULY 25, 1973

(lT n1't s are 10-4 m -1) . p.....:;::,i.~ o&----::...:,, JC..;.._-_...1.;- ~1 ,-=-"-~ ~--~ f~-U.~ ,-,~--.....:;-., ;;.JilliiiM~ ~ /~~.. ~~~ ,--~

- - • SUBSIDENCE INVERSION ----MARINE INVERSION

-•-•-• GROUND LEVEL WES TERN BASIN EASTERN BASIN /x WINOS ALOFT (km/hr.)

t . t I CNO WINOS LA WllltOS £MT WINOS 0.5 I 0.7 /20 1.0 1.0 1500 o,;J.11 I /29 1.1 /15 I 0.7 0.6 I 0.8 __..,a . 0.8 __...,,~ I : 0.9 -!! 0.9 0.7 1.0 1000., '-- 0.8 -E -- ~-2.9 ~---·· "O "::, ...,_; < I ~8 500 I _____ .Y- I .,I 7.;

11 .. ------~ ----- 6 4 ------. ------<- -~· N ...... SMO LA EMT BRA CAB RIA RED O'\ (17:36 PDT) (16:55 PDT) (17:07 PDT) (16:3', PDT) (18:23PDT) {18:05 PDT)

Figure 9. VERTICAL CROSS-SECTION OF b FOR AFTERl\OO:N OF JULY 25, 1973 scat (unitsT"'." • are 1o- 4 m - l . )

_..._,~~---ii!.i~~- ~- ~...::...,...... :;;~,_;_____, ~~- --~~J---=-~ - ,c ~ - -~... N ~ -..J

dh Mes ec 8v

& R~b

PACIFiC OCEAN

0 0 5 10 15 11'11 8 CONTOURS REPRESENT SNA E 4 I ! - !000 ft, 305 m 0 8 :6 2 ~ •"' SCALE c8s

Figure 10. TRAJECTORY ENVELOPE FOR AIR ARRI\1?\G AT CABLE AIRPORT (CPLA:\D) 1600 PDT, JULY 25, 1973 ,._,- ~ ------,1 H~~~ '-~~--~ q ___:::;;---__,_--::i- ,_:::_r-=-1--===12---1 ,..~ ?___.;;,..r..:...... ,~.:.... _==--::-..._ - ~- f~~ ~..,-- - -5±-a""t -~·~

ll~~r,1 ,ri,.' ,...... ,

ec 40 8v

0 HQ_

7 0 CAP {LAAR) O <:: VER

I -1 4 & 0 RLA WHq.R PACIFIC OCEAN ~ d LAH 0 COMA. Fa_ 3 L~ f:

! ~I♦ . ~~ 0 I Hl LA APCD VALUES 5 10 15 mi ADJUSTED TO AGREE 0 :S ~ WITH ARB CALIBRATION ~ E-j I I CON'TOURS REPRESENT NZJ ~ . 0 a SCALE !6 24 km - 1000 ft, 305m COS v~,J\ ______J 10 ro !.( i>f t-..:i ~ c.o Figure 11. SURFACE OZONE CONCENTRATIONS (pphm), I 600- I 700 PDT, JULY 25, 1973

-:-:,----=:::--~,-__.-~--~~~=------=--~ ~~~~~C-~ ~-~ N 1--' 1600------\D

14001------

1200 I Ground Elevation 1000 · 445 m ] l.&J § ,~~ 7 ) SURFACE. i ~ 800 6 MIXED LAYER ~

[ J OZONE CONCENTRATIONS ~ 600 \ ~E E ~ .. ~ I GREATER THAN ( . 50 pohm

400 I C H :;?'-E 'T Z' GROUND LEVEL

200 I P.UUloCETER UNIT Sn•BOL

0 0 NO,c ppm N 0.1 0.2 0.3 0.4 0.5 03 z co p;,m C 0 5 10 15 20 25 30 35 40 --~45~~ 50

I I I I I I I I I I TEI.IPERATURE oc -5 b 5 10 15 20 25 30 35 40 45 T ...I-- 0 10 20 30 40 50 60 70 60 90 100 RELATIVE HUlillOITY % H b1eot IO·"m-1 8 3 0 I 2 3 4 ~ 6 7 8 9 10 CN cm· 1 IO" X !URB.JLENC-C: cm2.13ue-' E

Figure 12. VERTICAL PROFILE OVER CABLE (CAB) J CLY 2 5 , l C)7 3 , l 63 6 PDT -..1...-=-1-~--t j --='~c.-o--;---'i-• 1-~~~ F------I ,ai~IH"J (~-:::It i<~~..;..... -~-1

1600 ______:______

1400 I •; •,

1200 ::

1000 -.5 L&J 0 ~ I- 800 ~ c( sooLl C r 11 :s. Ground Elevation C t~E H I~ cc ~ 1 l 90 m 4001 •c .. C - . H C C UNDrnCUTT!NG sv c- H ~I C II SEA BREEZE 200 C C \ / C [ -PARAM.ETER ---UNIT SYMBOL

0 0 NOx ppm N 0.1 0.2 0.3 0.4 0.5 03 z co ppm C 0 5 10 15 20 25 30 35 40 45 50

-- ·- -~20~----25 TEMPERATURE oc . -5 0 5 10 15 30 35 40 45 T

0 JO 20 30 40 50 60 70 80 90 100 RELATIVE HU..,IOITY % H b,cot 10-'4m- 1 8 3 0 I 2 3 4 5 6 7 8 9 10 CN crrr , 10 ◄ X TURBULENC'E cmZ-13 sec-1 E N N 0

Figure 13! VER TIC.AL PROFILE AT EL MONTE (EMT) JULY 25, 1971, 1656 PDT, SHOWING UNDERCUTTING BY THE SEA BREEZE

_-:;----=-G--~--- ~. ..._..,~ ~--- - .:.:.:. 1$' 1?' ~· I ~ 11¥ N~ ! N I :::·~_.,< ;:;;~···•······••:"'' I-' I t

- ~ \ ' ...... 0 . --p o··.. •· i.-. L:O. ·.. Joo.. 1 LACA '···. ,; '-.- ,·. :.·· -.:··., ' ~ _;·· .... \i\ ,r.=.v2v 0 ·.. ·•'.: MWS .. r ... T .....•.. • : ,,.. ·. K~Ji.;~ L4, ( ,..:::__;--,..1..A •••• . :, ..,·, -.- /'"?_,.·~·)//.?( /'0'"" - ) 0 I ,•• : i __ •• •J 17 t...-J~ N7 a S.I \; ~r' ,'1 rtd ~lt 'A-~ v- . · - cXa 0 19 ~ ~ ~~ RIA ~s~o -- _)~ J0J>J AS 0 J~ ___ , ~ ,,.Q, EMT 61.i 15 l'"1\JI.,. J,---."6~-11 ~o'?rr 0 WEST 15 0 0 5s Pc¼A r(A 0 CAP SMC 'CL..ARR)~R ~ c1i ) 19:00 1-­ R~A ! .., w'FJ{fo,~J''\_';),., CLO ;1 PDT II <::;I~~~/ (\,\..._'-.. L.~X L2X 0 RLA Clf1ito{;.._ff- 'J ) ' I<,.J~. ' ' ! PACIFIC OCEAN 0 ~ HILL~ R[V 0 CC'.tw\A '\,; \ ~BL ~J •.., ~ 0 14 U; \ (' \ '--\ \ I L~8 I 16 "~ 18=00 POT l 4 ~ \\_,"~r.1 .... _,., .. _? f!'.j i ~ ~~\~ \ -11,J -2Wl - . ., ~ ---:-- 11=oo··por,, l,~i ..... ··-. o 5 10 ,5 '.Tl! I '!_q'; CONTOURS REPRESENT SNAo ·NZJo\~1 ~1 /' ·--··· .,·· t==i--__F-3 9 I I "o. i ._.-,. I 0 8 16 24 km 1000 ft, 305 m · : / ./} ~: I - 14 7 /) I ~CALE --- 2500 ft, o2m V lr,1 ,·, i 0 5 ._,., ... i l ! 16:QQ I i ______.L 'o pol(· v( . ,

Figure 14. APPROXIMATE TIME (PDT) OF ARRIVAL OF SEA BREEZE, Jl-LY 25, 1973 (O':>_iective criterion based on ground level ozone concentrations.) ~....:::::.:::::. ,-___;;~==...~ ,~~ - ~ ~ ,=-~ f7r=~1 ..,_:,j~-~ ,--c..:,_~

u-·'"' ;- ...... · ',·····,;\ I ~- ... .,/ .... ··:.... ~ ..~::::1 WESTERN BASIN EASTERN BASIN . r /Joa_'····'_{ NOxEMISSION RATE NOx EMISSION RATE ~-. \ ..:.. 95 METRIC TONS/hr 10 METRIC TONS/ hr ... ,... . . -----•.._ ~ ~·.!~ \ I \-\OUR

.. \ . 1 ) .r.i. r ••; o···,. '.-,... /'·'~-----· l'2 \(.fTI I O ~AGA -.._ ~S _,.__ ,.._ ,.:··· !-, t:10; \ Joa...... ) ,__ ,. 8v -.:a._ , .. ;'--... :-•- ~v ~a'i'.- . A\..o·\.-·;~--T ...... ,..... ,:-, :') · .....r;.. ~ ·•·-: -::,···, ../ '; , :.f\. ·(,,,... ::\; ~-:.. ---.~~...., .. ·' ,.:4•.-.·..-. l A . ~ _. .; " \ (.- :/.. /.:: .• __:_., \ ./ AVERAGE CONCEN7RC.Ti')N iN it~ ~~~ ·-· :--:; \' ~-~ \ BOX (IF STEADY STATE) ~~~ 0 0 AZU~ : ' \ IS 25 pphm ~1 r, f'--Ji /7., ~Sv PAS ou \ )V c~~~ 1t:~C,S A~JF"P \_~o 03 FLUX THROUGH tUA ~(~- ~ t i ;'-."~ Li"\._) ! . "f:.~ \ \ ~ \~JI_~ - .,&_ Ji..M O SHADED BOUNOA~·~-#~ 1000 _.,....29 \_ ! \ \~~-.s-/'-' EMT 185 :t 6.0 METRI~ • ,. -.i:32 ~ ~ TONS/hr 0 (m) I 1 l ~ -~~ .O~ !

~. 0 -.__r,.J(.// ('.r'- J 550m PACIFIC OCEAN \ LAX _ C;,?;-·J'• _/ o M R, No _ r l HAR O HJ C LAH ~IV \ _ o c&.tA REDLANDS 18:QO POT I • ~ I /~- ... r'~ I RB\ MEAN TRAJECT~~~y 8 OUNOARY ~,:' ~·<°\;\ ~ ~ BETWEEN /;, ·: :_._ .: \ , iI ! WES ~ERN ANO"-",.., \'; ·.,; \/·: .-. . . """'\ ~ i 0 I > I '< '., •.· .•. \ ( ; ! T'OA L~S EASTERN "~ i ·\·, '· :.- .-. \,. ~ I A S . ~! .. '-...:\ ·- I ¼ ~ ~~ t 0 - BASIN ~,-~ ~l t AN ~ rt1 ~~ \.-:)\.~:~--·~-•.• .J ,:~\--. . ~,1':_\--t------l ,,, .-is-eo\ ::-..._:,: ---~ ·1- ' ._. --~ \---::..,-- '---"""' -- ( '•··:> '1 - '·<.- .. t,, __ }5 mi 1 <>· 0 5 10 0 Q ~ 1 r.·.'. .••••·; "'~:9. j=i r-i C: CONTOURS REPRESENT SNA NZJ ~/} .... ·· .-..,.. ·-. 8 ltl 2~ !un 0 - 1000 ft, 3::::>5 m ! N Alr~ :••.•w' .---··-. .••• :•·... ·.. ,:·(1,' ····.•• SCALE 'v ? N --·· 2500 ft 762 m 1 cos r\v~ ~--...~- .:-·.. .: ,..,~-- . N ~ 0 -.: I ! -~ Figure 15. ESTIMATED OZONE FLUX FROM \VESTER~ TO EASTER:-J BASIN, JULY 25, 1973 I 700 PDT ~· ~' ~Qa' 11f'' llf..J.D.' \\f.l( ~I I

:.l L.fb. 0 ~s ec CPK v2v 0 ALT 8v Ld~_.----'1 .:2-~) - ~ ~; I /l;~w.-,,.~,\~ p~,- £)_ A~U 1 0 I ·/ p tl- Cf.U oj I ) 1 \ \"~.,I "i • ·• : ~·,~'-..:/:L,\.i. ~ J 1.)-.. 0 0 ... . " F8f" 17:30 ) I I \, ~- HO- ENT 'r•-~ 'i .) 0 Di ~ l 0 I /"") ~,~coc. (WljT "-._,-~;(/ I CA ~<, <-rw--- .. ·{LARRv O 15:30 "" -~,t::: VE~ s~e ~ _; . . I

A. c~o RAL PACIFIC OCEAN ;J 0 ~~ ~'-_'i~cB C r.:-iR 13:30 ~~\~ . ol ~IV \ 12:30 1,~\ RE}\ (Di ' \/;:, PO\ Ftl ~- I '- ;; ) ' 0 \---~\,/ L8s ~'Z,>-,., \__ i ♦ ( T~ \ 0 \\._,·:_ ~~, ~ . }, I AN .j t. b; ~~-~ ~ !;i' \;\ I ~ I L// i '-._,,"> j i ! o 5 ,c !5 'Tl' \· \ \ 0 0 ~-,:; p__i=r 2=f I_ I 1 \ SNA NZJ .:,1 .1 8 ,,: 2 4 km ' / './) SCALE I 00 .J_(1 CONTOURS REPRESENT cos /! 'f 1 ! ! ' 0 I --- !/; I - ;.:'.)'),'.) !, 3:5,...

Figure 16. TRAJECTORY E~VELOPE FOR A.IR ARRI\!'1>JG OVER REDL_.\):"DS AT 1800 PDT, JULY 23, l =i"73 224

JULY 25, 1973

§.0.40 0 a. ~ L.A. DOWNTOWN ~ 0.20 0 X 0 z ~ LJ... 0 ~ z 5 0.40 ~ POMONA 330 ~ 0 en ~ 0.20 w z _J w w 0 (9 z O----u-~~-,__~_-~~~------L-~-0--0-0~-----, z ~ 0.40 -C~------~\~~~ a::: LL ~ \ (I) Rate ~ IO mph___.,.\ w ~ \ _J ~ \ ~ et: ~ \ <( 3 0.40 PALM SPRINGS \ ~ 105 j 0.20 ~ 0'------..____--'---.....L:...--...___---'------L---~--~ 12 4 8 12 4 8 12 l~-..:s:...----a.m. ,.,.._ p.m.----....1 HOUR OF DAY, PST

Figure 17. Diurnal variation July 25, 1973, of oxidant concentrations at air monitoring stations at Los Angeles Downtown, Pomona, Riverside, and Palm Springs, California. Values are corrected data: Los Angeles Downtown and Pomona x 1.1 and Riverside and Palm Springs X 0.8. 'CON"."O.; S " t, 1" " :f:'RESE"IS7, %~:.. ;}.~-- N N .~"'' V1

~~ vO 0 0 ciff·,dK, ~ v~~o ~ 91 ( ~s . V7 ..... ~, • /~r ~ • "'\ ~ \1:--~~----Sooo\tl ~ ~ ~'? .lj ' :::?.i1" 'd t, CJ ,, ½ ~. ·L,~Js _-/'-. ~ \{&fr..s,,,·f;,.<;-' ~ au. ~-') ..;.;.~ \ . " ' ...... ,_\>>\ ·~ ~rro ,-,t·,.'-.F' . 'Q ~ ~-tv\, I_/~ ,,.,--- ONT p(_ ◄ s ~S ~~~- [ (\\\ ' . 0 c-_ --~ ~~~___.d'_.). <:'- ..,.\\~...:::/ I -!:i- C - \-.. ~----1.-1 , •~~POMA .. ~V BN""\,;""" )\; ·-::~ f / -- s . - ~ 2 ~.VA,..,/ :.,-·-.,. ~p AAL , ~~ ;:~~ ·01/ ,, r r .... ~: · · '0--, ,... aV : 1 0 LAX . J,-i/-?

- . -~- - ·O, ./ _,a '-'?' \Tl --0-. . ov I..\ lHOIO J I • , , ,J --,., ~ "6" ~ -_._ '2, ~ (\__ : _- ·8--- , •~.-:a,'".••! ._,~ ~~ ~-c'.>.~-~ ~ • • · e • ,., .,, fl,~,/ '--• l ~,·:0 ~ 0 ,.:, . . . I !1,A_ H'ZJ ·o~J (~ ~ . S ,TAA - ~ - -: - .. --0..... () ...._"'-..j J:, ·'O ;=,c,,==c-..c==cc~~~ l ~'~ "' ~ ~ •'- ~---.~ ~ !. •• -~ al1 ~ • . . __ ~--···

♦ Skyforest ,._ Strawberry Mt. Lookout

Figure 18. STR.E...\~[Ll);ES FOR 1600 PDT on 8/ 16/73 ,,_J.....-_ -1 ,~ -=1 ~~, ~~~~l r=--~d.- ---1 f""~ ,~E.1 ~L:,,1-~

3100 ,------

2900r------

T

e w 0 ....~ 5 Cl Ground Elevation 1560 m

170 I I I UNIT Sn•BOL z PARAMETER \T NOx N ppm 0.1 0.2 0.3 0.4 0.5 03 z

-- co ppm C 0 5 10 15 20 25 30 35 40 45 50

TEMPERATURE oc T -5 - -0~ 5 10 15 20 25 30 35 40 45

0 10 20 30 40 50 60 70 80 90 100 RELATIVE HUMIDITY % H b,cot 10-4m-1 8 3 0 I 2 3 4 5 6 7 8 9 ,o CN cm- , to• X 213 1 TUR8ULENC~ cm sec- E N N O'I

Figure 19. VER TICAL PROFILE OVER ARROWHEAD u-\R.R_l A CGCST I 6, 1973, 9:39 PDT 3100.------

N N 2900r------i

2700i------

2500 e uJ 0 2300 ....::> ~ ct 2100

1900i------+------

~le 1iation 1360 m) 17001 ~ ? \ PARA1,jETER UNIT SYMBOL

T N 1500 ,o -- NOx ppm 0.1 0,2 0.3 0.4 05 03 z co ppm C 0 5 10 15 20 25 30 35 40 45 50

TEW?ERAT'JRE oc T -5 · --~o--- 5 10 15 20 25 30 35 40 45

H 0 10 20 30 40 50 60 70 80 90 IOO RELATIVE HUWIOIT Y % b,cat 10-~-1 8 CN cm- 3 , 10'4 X 0 I 2 3 4 5 6 7 8 9 10 213 1 tURBlii..ENC'E cm sec- E

Figure 20. VERTICAL PROFILE OVER ARROWHEA. D \.-\RR; AUGlJST 16, 1,. "'I,)--- -, 16:--1:S PDT ~-4 1-~:::i w-.-~;;..i,'_f l"-=--•C- ---

1600 • t c- N 8, ff T • C[ " 8. H 1 !. • H z.. H T ~ C f N 1 H T • C rn ' 1 C NE •-...... ~z' H i400 . ' " • • tf T' • • "N ~r ...... _P H -y EC N "z,.--·__ 'e . H T i' . 8 z H T C E HD " H POLLUTANTS REMAINING FROM • ...... Z"" T •t C • , H T PREVIOUS DAY 1200 Et HO L ,... II -·-- I . • Ct H 9 -, H T ...... _,_,_ H •(; E N 1 a tC N i--.._ -1 H ' . • C N Z. \ HP T £IC C H 'z...... _ 1111 1 1000 • C H Z, l! _H_ _J )( cc H -z e:· k -.§ C N H T • ~ ' )( iz IA.I - . 8 H T 0 t XC " 'z 7,--., T ::> • £ "N t H_8' t- Y.C£ N 1 800 I-"- H ' ><• l - ' !:i (Jet "N '-r,~B !- ' t C X N % H T .. [ BUOYANT POINT SOURCE PLUME C H H 1 C JZ X H T -• SUPERIMPOSED ON POLLUTANTS 600 -..~ ~z--E ,c " ., REMAINING FROM PREVIOUS Ot\Y " Cl JC t " H H f' ✓ ,c· t HT -fl'• ,_ C- { X t fl " -e- REMNANT OF NOCTURNAL RADIATION INVERSION C 'f N K I: T '" H (I---- C Z [ T H x'-8 _Z"c r -H -K 400 " ... SURFACE MIXING LAYER ,z C " I.I' H K .8 C N " T £ H M 8 ,._ -t l I ff ' H E N -9 200 Ground Elevation 305 rn ... PARAMETER UNIT SYMBOL _, I -, I I I N 0.0 NOx ppm 0.1 0.2 0.3 0.4 0.5 03 z co ppm C 0 5 IO 15 20 25 30 35 40 45 50 ·1 L TEMPERATURE oc T -5 0 5 IO 15 20 25 30 35 40 45

0 10 20 30 40 50 60 70 80 90 100 RELATIVE HUPAIDIT y % H bscot ,o-4m- 1 B 3 4 0 2 4 10 CN cm- x 10 X 3 5 6 7 8 9 213 1 TURBULENC~ cm sec- E N N co Figure 21. VERTICAL PROFILE OVER BRACKETT (BRA) JULY 26, 1973, 0825 PDT SHOWING BUOYANT PLUME AND UNDERCUTTING BY RADIATION INVERSION N N 1600 \0

• C ...... ___ M C C

1400~,~~ t C [ · H LAYER CAUSED BY C C H C [ H UPSLOPE FLOW 1200 l

1000 ] w 0 ::, ... --= ~ -~~ SURFACE MIXING LAYER 800~ 6er: C C 600t-i C C t C I ~00

Ground Elevation 436 m 2001------

PAIU.WETU UNIT SYWBOL

NOx ppm N 0 0 0.1 0.2 0.3 0.4 0.5 03 z co ppm C 0 5 10 15 20 25 30 35 40 45 50

I I I I I I I I TEWPERAT1JftE T -'o b 5 10 15 20 25 30 35 40 45' °C

0 10 20 30 40 50 60 70 80 90 100 ~EI.ATIVE HUWIOITY % H b1tt1 10-"m-' 8 3 0 2 3 4 5 6 7 8 9 10 CN enr 110" X Tu R!!UL Er.ct cm2'3sec-' E

Figt1re 22. VERTICAl PROFILE AT RIALTO (RIA) JlJL Y 19, 1973, 1738 PDT, SHOWI='JG LAYER CAUSED BY UPSLOPE FLOW ~~-7 ~: ~-.. :1 ~~-~ i ~~-. ~t ~i...... r, ~~ ~ =~·-1

1600------

1-1 ,. M t: H T H t H . t M T H l H H 'l 1200 I t '. 1 If/' J- H T H t 11 T • H. t_. M t H 1 1000 M l ] H , w If H )' g I C ,

PAllA!lETER ~ 5Y"l80L N NOx ppm 0 0 0.1 0.2 0.3. 0.4 0.5 03 z co ppm C 0 5 10 io 20 25 30 35 40 45 50

TEMPERATU~E oc T -5 0 5 lO 15 20 25~--- 30 ---35~~-40 45

0 iO 20 30 40 50 60 70 80 90 100 RELATIVE HUMIDITY % H ba,;ct 10--

Figure 23. VERTICAL PROFILE OVER RIVERSIDE (RAL) N JULY 26, 1973, 2239 PDT I.,.) 0

·==-=-= N w 1--' i' i' ~ -.s~ CJ"' ~ ,l -o• o• -o• o• 5,. 0.2~ o.~ bscat ---- bscat Oa - o, 4l o.2J. 0.2

( Power Plant Plume .. / Power Plant Plume I- 3 0.1 ..- 0.1 e • I 1 .. .,~ e ! l ~ I - 11 s , 111\ t 0 [ ,, • '1,. I' 0 ill~t .E: I' ' .P: )( " fl I•\ - ,: )( I - • I ii \ 0• I 0 - I I ~ I .I1:r. ~\I l l·· u -..., 2 o. 1 I ,' \ u 0.1 : \ A• ' r-.,., I \ I I 'i \ l ,"I 1: A • I \ 'I I I I ' .! I H1t I I Ir t 4 I , ,,, I I / 11 I I l I:v,r.....,,.,,, V ....., /\ I I I I I \ I . I ' J'V'''-f " 'Jl' I I ,I r q\ '•",' \ ll o. 01 I I 0.0S,.~,J!1 I • ,.t: I\ • I I ti ··1' " ·v··..~.. I I ,•J\.\~ ·/ ~ vi \ I J I I ""'""" ~ Urban Plume ...... y Urban Plume ol o.od o.o I ' 0 10 20 30 40 50 0 10 20 30 40 so kilometers kilometers

Traverse at 750 m msl 35 km Downwind (SW) of Traverse at 750 m msl 46 km Downwind (SVV) of Arch - St.. Louis, Mo. 1117 - 1137 CDT Arch - St. Louis, Mo. 153 0 - J 549 CDT

Figure 24. 232 . RELATIVE CONTRIBUTIONS OF STATIONARY AND.MOilILE SOURCES TO OXIDANT FORMATION IN LOS ANGELES COUN1Y: IMPLICATIONS FOR CONTROL STRATEGIES

by Robert G. Lunche, Air Pollution Control Officer Los Angeles County Air Pollution Control District Los Angeles, California Introduction

The type of air pollution problem characteristic of the west coast of the

United States, and particularly of Southern California, has come to be known

as photochemical smog because it is the result of sunlight-energized atmospheric

reations involving oxides of nitrogen and reactive hydrocarbons. Its manifesta- \ tions- -eye irritation, reduced visibility, damage to vegetation, and accumula-

tion of abnormally high concentrations of ozone, or oxidant, - -are by now, well

known. In fact, the occurrence of high levels of oxidant, which consists almost

entirely of ozone, has bec.ome the primary indicator for the presence and relative

severity of photochemical smog.

During the 25 years since photochemical smog in Los Angeles County was

first identified, an extensive program has been underway for control of the respon­

sible contaminant emissions. Initially, during the 1950' s these programs concen­

trated on controlling emissions of hydrocarbons from the stationary sources of this l contaminant. In the early 60' s, programs for the control of hydrocarbon emissions

from motor vehicles in California were begun. An exhaust emission control pro­

gram for hydrocarbons and carbon monoxide from new vehicles was begun in 1966.

C011.trol of oxides of nitrogen emissions from motor vehicles began in 1971.

As a result of the overall control program, by 1974, emissions of reactive

hydrocarbons from stationary sources have been reduced 70fo from uncontrolled

levels, and about the same percentage from mobile sources. Oxides of nitrcgen emissions 233 from statjonary sources have been reduced about 53% while emissions from mo­ bile sources are still about 7% above uncontrolled levels, due to the increase in NOx from 1966-1970 models. Additional controls already planned for the future will, by 1980, achieve reductions of re.active hydrocarbons from stationary sources of about 87% from uncontrolled levels and from mobile sources, about 93%. By

1980, emissions of oxides of nitrogen from stationary sources will have been re­ duced 53%, and from mobile sources 63% from uncontrolled levels. The past, present, and projected emissions of these contaminants are shown in Figure 1.

A I though compliance with the air quality standards has not yet been achieved-­ and is not likely before 1980- -the results of these programs have been reflected rather predictably in changes in certain of the manifestations of photochemical smog. For example, eye irritation is less frequent and less severe, and in some areas js rarely felt at all any more and damage to vegetation has been markedly reduced.

Ozone (or oxidant) concentrations have been decreasing in Southern California coastal areas since _1964; in areas 10-15 miles from the coast, since 1966; and in inland areas 40-60 miles from the coast, since 1970 or 1971, as shown on Figures

2 arrl 3.- All of these positive effects have occurred despite the continuing growth of the area, indicating that the· control programs are gradually achieving their purpos a return to clean air.

This improvement is al~o refutation of the so-called "Big Box" -concept which assumes that the total daily emissions in a given area are somehow uniformly dis­ tributed throughout that area--regardless of its size or of known facts about the meteorology of the area or the spatial and temporal distribution of its emissions- - 234

and of control strategies based on that concept. And, since the improvement in

air quality refutes the control strategies based on reductions in tot.al emissions,

it thus confirms the value of more recent control strategies which emphasize con­

trol of motor vehicle emissions and use of a source-effect area concept.

Following is a brief listing of the evidence we intend to present as supporting

our views on just what control strategy is appropriate: • Examination of relative contributions of HC and NOx from stationary and mobile sources demonstrates that motor vehicles are the overwhelming f source of both contaminants~

I • Observation of air monitoring data shows that the effects of photochem -

ical smog are not uniformly distributed t_hroughout the county.

• Study of the meteorology of L.A. County shows consistent paths of trans -

port for various air parcels, and consistent relationships between the

areas most seriously affected by photochemical smog and high oxidant

concentrations and certain other areas.

• The upwind areas are found to be source areas--the downwind areas-­

effect areas. I • Central L. A. is found to be the predominant source area for the effect area in which the highest oxidant levels in the SCAB consistently occur.

• The predominant source of emissions in this source area is found to

be motor vehicles.

Central L.A. has the highest traffic density . '\ • I'\ ij • Both pr~mary and secondary contaminant concentrations reflect the effects of the new motor vehicle control program in a predictable fashion. 11 I • A strategy based upon these findings is gradually being verified by atmos­ pheric oxidant data~ 235

The Evidence that Motor Vehicle Emissions Are the Principal Source of Oxidant

As seen from Figure 1, at the present time, the total daily emissions of I-IC and_ NOx from all sources in Los Angeles ·county are primarily due to the motor vehicle. The problem now is to find the spatial and temporal representation of emissions which, when examined in the light of the known meteorology and geogra - phy of the Los Angeles region, best describes the source of emissions responsible for the highest observed oxidant readings.

In the "rollback" models used by EPA and others the basin is treated as a

"big box" with uniformly distributed emissions, and peak oxidant is considered to be proportional to total basinwide hydrocarbon emissions.

The fact is that the ·emitted contaminants from which the smog is formed, and the effects which characterize that smog, are not evenly distributed throughout the Los Angeles Basin; in other words, the basin area under the inversion is not one large box filled to all corners with homogeneously distributed air contaminants and photochemical smog.

Refutation of "Big Box" Myth

Examination of atmospheric contaminant concentrations refutes the "big box" concept. It is found, for example, that concentrations of dj.rectly emitted contam- inants measured at a particular sampling site reflect the emissions within a rather limited area around that site. For this reason, contaminant concentration levels vary from one location to another and each has a characteristic daily pattern which reflects the daily pattern of emissions in that area. · 236

The "big box" concept is further refuted by the fact that peak concentrations

of carbon monoxide and oxides of nitrogen in areas of high traffic density were

fairly static prior to 1966. Thus, they did not reflect the 45-50 per cent growth

in motor vehicle registrations and gasoline consumption which occurred in Los

Angeles County between 1955 and 1965 and which caused comparable increases in

total daily emissions of such vehicle-related contaminants. This demonstrates

that growth was outward, rather than upward, so that a larger area of the County

J began to be affected by photochemical smog, but no area experienced smog of greater severity than that originally affected by smog formed from the vehicular

emissions which accumulated each weekday in central Los Angeles and were trans- 'I 1 ported later that day to the San Gabriel Valley.

'1 ! Meteorological Evidence

To verify the geographical dependence of emissions and resulting atmospheric

concentrations, let us examine the meteorology of these large areas of Southern

California. Both the County and the Basin have many meteorological sub-regions

in which the patterns of wind speed and direction may be similar, but within

which the patterns of air transport are parallel with those of adjacent sub-regions

and the respective air parcels do not ever meet or join.

The characteristic patterns of inversion height, and wind speed and direction

in these sub-regions, and their patterns of vehicular emissions, together have

created a network of source areas- -those in which the reactant contaminants accu-

1T \i ~ mulate in the morning and begin to react--and related receptor areas--those to which

~ the products, and associated effects, of the photochemical reactions of the contam­ ).' inants originally emitted in the source areas, are carried by the late morning and 237 · afternoon winds ( sea breeze).

Wind-flow patterns show that characteristic patterns of transport for related

source area-effect area combinations are separate and parallel, not mixing or joining. Each source area has its own "reactor pipeline" to its own effect area or areas.

To illustrate this source area-effect area relationship, the typical flow of polluted air from downtown Los Angeles to Pasadena was selected as a "worst case" situation for in-depth examination. Figure 4 shows that the air in downtown

Los Angeles on the morning of smoggy days moves directly from the central area to Pasadena.

Vehicular traffic is the predominant emission source in both downtown Los

Angeles and Pasadena. Thus, the air in each locality should contain CO. Also, since oxidant would form in the air parcel moving from Los Angeles to Pasadena, oxidant levels would be expected to be higher in Pasadena than in downtown Los

Angeles.

Figure 5 shows these relationships for the period 1960-1972. The atmos­ pheric CO level is similar for the two areas, while oxidant levels were higher in

Pasadena than in Los Angeles throughout this time period. This demonstrates that a significant amount of oxidant formed in the air as it moved to Pasadena containing both the unreactive CO and the photochemical reactants for producing oxidant. Both CO and oxidant show a marked downward trend in each locality since

1965, which emphasizes the effect of vehicle exhaust controls and the correlation between the localities. 238

On a day which is favorable to the formation and accumulation of photo­

chemical smog, a contaminated air parcel normally originates during the

6-9 a. m. period on a weekday from an area of dense traffic, centered just

south and west of Downtown Los Angeles. It is oxidant generated within that air

parcel which usually affects Central Los Angeles and the West San Gabriel

·K Valley area around Pasadena. IJ l J The traffic are.a in which this smog had its origin is about the most dense

in Los Angeles County, and has been so for the past 25-30 years. No area

. has a higher "effective density" th&n-this. Using carbon monoxide, which

is almost entirely attributable to motor vehicles, as an indicator of such emis-

1 sions, it is found that the concentrations of emitted vehicular contaminants

·r measured in Central Los Angeles during the past 15 years confirms both this lack i of change in "effective density" and the absence of any area of any greater "effective

density" when local differences in inversion are acknowledged.

This area, the "Central Source Area" is depicted in Figure 4. The size

and shape of the Central Source Area was ch~sen to be large enough to reduce to

an insignificant level any diffusion or transport into this area from any externally l generated reactants. This conclusion is based in part on the trajectory studies previously referenced, as well as an analysis of the diffusion and transport para­

meters for the area. 239

The Central Source Area has been identified as that geographical region which contributes essentially all of the primary contaminant emissions giving

rise to the highatmospheric oxidant levels in the West San Gabriel Valley.

The proportion of emissions in the CSA due to motor vehicles and that due to

stationary sources is shown in Table 1. For the County as a whole about 80 per cent of _(6-9) AM reactive hydrocarbons are due to motor vehicle emissions and this

figure rises to 90 per cent for the CSA. The same conclusion a pp lies to NOx

emissions. The Central Source Area contains the greatest density of vehicle traffic

in the County and thus the greatest density of source emissions. Thus it appears

that the source area with the highest density of emissions during the critical"(6-9)

AM period is responsible for the highest afternoon oxidant levels observed in Los

Ai1geles County and in the South Coast Air Basin. These highest oxidant levels are consistently observed to occur in the San Gabriel Valley. This is true whether

the LAAPCD or the ARB oxidant calibration procedure is used.

Further, the atmospheric concentrations of the primary pollutants can be

identified as originating primarily from the motor vehicle and they reflect the

effects of the motor vehicle emission control program. A vehtcular source area

can be identified by its atmospheric levels of CO and NOx. Figure 6 compares

measured atmospheric levels with calculated atmospheric levels for CO, NOx and the CO/NOx ratio in the downtown area. TABLE 1 240 REACTIVE HYDROCARBON EMISSIONS

(6-9) AM 1970

LOS ANGELES COUN1Y · CENTRAL SOURCE AREA · SOURCE TONS PER CENT TONS PER CENT

Mobile* 126.0 81. 3 13.5 91. 2

Stationary 29.0 18.7 1. 3 8.8

Total 1s~.o 100.0 14.8 100.0

*By 7 -Mode, Gallonage 241

The calculated values shown in Figure 6 were derived from a baseline

survey of 1100 vehicles and continued surveillance tests, both using the Cali­ fornia 7-Mode test cycle. The baseline survey showed that motor vehicles with­ out exhaust control systems had average exhaust emissions concentrations of 3. 4 per cent CO and 1000 parts per million of NOx. Baseline emissions data apply

to 1965 and earlier model vehicleg, and surveillance data to 1966 and later models.·

Since it can be concluded from calculations and observations that the dilu­ tion of auto exhaust emissions in the atmosphere on a smoggy day in Los Angeles is approximately 1000 to 1, the calculated values for CO and NOx prior to 1965 are

34 ppm CO and 1 ppm NOxo After 1965, the changing effect of controlled vehicles in the total vehicle population is reflected in the calculated values.

CO and NOx values measured in the atmosphere are also shown in Figure

6 and confirm the values calculated entirely as diluted vehicular emissions. NOx concentrations measured in the atmosphere tend to be consistently a little lower than the calculated values, probably because photochemical reactions remove some

NOx from the system.

The data for CO and NOx, calculated and measured, show that emissions in downtown Los Angeles originate almost exclusively from motor vehicles and that atmospheric concentrations there reflect the average emissions from a representa­ tive vehicle population.

The ARB has recently published a report entitled "A Trend Study of Two

Indicator Hydrocarbons in the South Coast Air Basin". Acetylene was used as a 242 specific indi.cator of automobile exhaust emissions and it was found to have de-

clined in concentration in the Los Angeles atmosphere at an annual rate of 12. 5

per cent since 1970. To quote from this report, "The California implementation

plan requires an annual average reduction in these emissions (reactive organic

compounds) of 166 tons per day, or 11. 1% of the 1970 tonnage per year. The per cent

reductions in the_ acetylene levels at Los Angeles and Azusa are greater than re­

quired by the implementation plan. Since acetylene is almost entirely associated

J with auto exhaust, this demonstrates that the motor vehicle emission control program is achieving its purpose."

To summarize at this point it has been deomonstrated that high oxidant values

are due to motor vehicular emissions of NOx and HC because:

NOx and HC are the principal reactants in the oxidant formation process

and they originate primarily from motor vehicle emissions; and

The highest oxidant values are recorded in_ effect areas that receive air

from source areas where motor vehicles are clearly identified as the

dominant source of NOx and HC. 243

Future Control Strategy

The APCD strategy for achieving and maintaining the oxidant" air quality standard is based upon the fact that high oxidant values are due to motor ve- hicle emissions of hydrocarlxms arrl nitrogen oxides. This strategy is as follows:

1. Both Hydrocarbon and Nitrogen Oxides Emissions Must Be Considered To A chieve the Federal Oxidant Standard

There is wide agreement that NOx and HC are the principal reactants in the oxidant formation process, and that vehicular emissions are a major source of NOx, HC and CO.

2. Effective Regulation of Atmospheric Concentrations of Both HC and NOx, and of the Ratio Between Them, is necessary for Attainment of the Federal Air Quality Standard for Oxidant

Bas·ed on the abundance·of available experimental evidence, it is our firm position that the most rational approach to solving the photochemical oxidant smog problem in the South Coast Air Basin (SCAB) is to control the quantities of emissions from motor vehicles of both smog precursors--Hc· and NOx--their resulting atmos­ pheric concentrations, and the ratios between both contaminants which will result from these controls.

We arc also convinced that the oxidant and nitrogen dioxide air quality stan­ dards can and will be met, not by 1975 or 1977, but by the early 1980' s if the emis­ sion control program as originally outlined by Ca~ifornia, or a slight modification of it proposed by the District, is followed and enforced. This should also provide for continued compliance with these air quality standards, at least through 1990. 244

It will also allow time for a reappraisal in about 1978 of the whole situation relative

to the ultimate emission standards required, and the best approach to their imple­

mentation.

Calculation of the degree of control necessary to attain the air quality

~ standards for oxidant and nitrogen dioxide involves indirect, complex methods '1 aimed at determ_ining the degree of control of the primary contaminants directly

emitted by automobiles.

The following evidence supports our proposed solution to the problem in

terms of both the atmospheric concentrations of the oxidant precursors, NOx

and HC; the ratio between them, as reflected in their exhaust emission standards;

and the resulting atmospheric concentrations of oxidant which comply with the air

quality standards.

Chamber Results and Projections to the Atmosphere

The importance of environmental chamber.work cannot be minimized; the j need for, and direction of, the whole emission control program was based initially ' :j on the results of chamber experiments. In order to understand the importance to air quality of achieving both the correct low quantities of emissions and the right

ratio, we can present several graphic portrayals of analyses of experimental lab­

oratory work, together with their relationship to past, present and future air quality,

in terms of both morning primary reactant concentrations, during the morning

traffic peak, and the equivalent emissions which would produce them. 245

Figure 7 shows maximum ozone levels that were obtained by irradiating

varying amounts of auto exhaust hydrocarbons and oxides of nitrogen in an environ­

mental chamber. The corresponding ozone levels, then, can be found for any com­

bination of BC and NOx concentrations. Thus, high ozone is produced with high

"emissions" of both hydrocarbons and oxides of nitrogen and low oxidant is formed with

low emissions. However, either low NOx or low HC "emissions11 can also produce

low oxidant--graphic and clear evidence of the importance of the NOx/HC ratio in

ozone formation. Furthermore, each and every possible combination of values for

NOx and HC has, then, a corresponding characteristic maximum chamber ozone

concentration.

Using this graph, we can estimate what ozone levels would result if certain

atmospheric mixtures of NOx and HC could be injected into the chamber and

irradiated. Such estimates were made for 1960 and 1965, using atmospheric data. rl The points labeles "1960" and "65" show the location of the highest levels of both

HC and NOx found in the air in those years, in Downtown Los Angeles (OOLA) area

during the 6-9 AM traffic peak.

It has been demonstrated, by use of CO and NOx data and CO/NOx ratios,

hnw well the characteristics of vehicle emissions are reflected in the atmosphere.

We know what emissions from the "average vehicle" were then, in 1960-1965, both

for HC and NOx, so that we can mathematically relate emissions to atmospheric

concentrations for those years; and so for future years also, knowing or calculating only what the characteristic emissions will be from the average vehicle. 246

The NOx concentrations stayed about the same from 1960 through 1965 because average vehicle emissions of that contaminant did not change during that time!

Mobile source emissions can be shown to have contributed essentially all of this ob­ served result. However, blow by controls did reduce emissions of HC, and the concentrations dropped accordingly. In 1965, the last year before exhaust controls, the point "65" indicates where we were then, in terms of maximum ozone formation to be expected in a chamber with the highest HC and NO concentrations found in the X air that year. Levels of ozone actually measured in the atmosphere, however, are higher than those shown on the graph for high NOx and I-IC concentrations, for those years up to the present.

The strategy to meet the oxidant standard is obvious--get atmospheric NOx and HC concentrations out of the area on the chart that produces high ozone levels, and put them in tie areas with the lowest levels. This can only be done by implement­

ing appropriate emission standards.

As can be seen, that did not happen between 1965 and 1970 because manufac­

turers used controls on new cars in California which, while causing a decrease in

BC, (and CO) allowed a large increase in NOx emissions. Thus, the "path" line of

the atmosphere on the chart goes up from 65 and diagonally to the left, passing

through an area of higher ozone "levels". The atmospheric concentrations of oxidant predictably increased during the years 1967 and 1968. By 1970 they dropped to lower

levels - -back to about the same as in 1965- -exactly as predicted by the model! The app1:4oximate location of the point for 1970 (70) was both predicted, on the basis of 247

the "mathematical model", and confirmed by atm-ospheric measurements of

[)owntown Los Angeles, morning, summertime, NOx and calculated HC values.

Again, it should be pointed out that those points show the highest possible concentrations of NOx and HC. Years with less restrictive weather conditions

(for accumulating high primary contaminant levels) would cause lower measured

maximum NOx and HC levels, but the calculations would still yield the points

shown. Thus, we are taking the most pessimistic view.

Future Projections

In 197 3 we were at about the point labeled '73, and ozone levels were begin­

ning to drop as expected. · It should be emphasized that ozone values plotted on

thi$ graph are for the chamber only- -not the atmosphere. The future path, the points '7 4 and on to '90, represents our estimate of future atmospheric levels of

NO and BC expected if the exhaust emission standards are just met. While that X - is optimistic, it is all we really can do since performance of future vehicle models

is unknown. We will achieve maximum ozone levels at or below the standard by

about 1980-1985. This will only be true, however, if cars in compliance with the

California interim standards for HC and NOx continue to be added to the vehicle

population at the normal rate. These standards provide the optimum ratio of NO X to HC necessary to provide the nitric oxide (NO) needed for the reaction that re-

moves from the air both oxidant formed photochemically and oxidant which occurs as natural background which alone may cause the standard to be exceeded. This

ratio is about 11/2 or 2 parts NOx to 1 part HC. 248

The optimum NOx/HC ratio is a key element i.n the APCD strategy, but will

require a finite time for its attainment. Replacement of older cars by newer ones

equipped to meet the most stringent standards is the only reasonable mechanism

which can change it. VMT reduction proposed as a prime strategy by EPA, cannot

change this crl(ical ratio which is a basic characteristic of the "population" at any

given time.

Validation of the District's Control Strategy

Figure 8 compares: (1) future "chamber" oxidant levels, based upon the

future maximum concentrations of HC and NOx we expect each year with the

,, California control program; (2) calculated "atmospheric" concentrations, using ~ I our chamber-to-atma,sphere empirical translation; and (3) actual measured atmos- f l 1 pheric oxidant maxima. This clearly sets forth the relationship among these three factors.

The chamber concentrations (lower curve) ·are the lowest values shown.

The actual atmospheric data (points connected by heavy dotted and solid lines)

vary considerably from year to year partly because of the vagaries of the weather.

In all cases, the atmospheric oxidant values are higher than the chamber values

because of the addition of vehicle emissions as the air parcel travels from source

to receptor areas. The calculated atmospheric data (thin dashed and solid curves)

are shown to be the highest, generally exceeding or equalling the actual measured

data and, of course, always exceeding the chamber data. Thus, the model paints

the most pessimistic picture possible. It can be seen that by about 19801... 1985 atmos -

pheric levels should be at or below the Federal air quality standard of 0. 08 ppm oxidant. 249

3. Motor Vehicle Exhaust Control is the Only Requirement for Achieving the Oxidant Standard by 1980:

We can show that the existing motor vehicle control program has resulted in a significant reduction of oxidant concentrations in the air.

The foregoing material.explained the relationship between vehicula~ emis- sions in source areas and the high oxidant levels measured in effect areas. This relationship is exemplified by the downward trend of oxidant levels in the atmos­ phere and by the similar year-by-year trends of NO and HC emissions from the X average motor vehicle. A projection of these vehicle emissions factors shows that the associated maximum oxidant level in the atmosphere will meet the oxidant standard by about 1980-1985.

Figure 9 compares, by year, the number of days that the oxidant air quality standard was exceeded in three separate areas with the average NO and HC emissions X per vehicle mile. To comply with the air quality regulations the number of days that this standard is exceeded must be reduced to one per year.

The lines plotted on Figure 9 show that a definite relationship exists between the emissions from the average motor vehicle and the number of days each year that the oxidant concentration in the air exceeds the "clean air" standard.

The oxidant trendlines for downtown Los Angeles, Pasadena arrl Azusa are all downward and the slopes are about the same. This similarity is logical because the process that results in the suppression of oxidant accumulation simply has been displaced from one area to another. This was a unique, one time situation because of the increase in NOx between 1966 and 1971. After 1971 all areas are down. Thus, 250

the same conclusion is reached: that the oxidant.standard will be met in the 1980's

'I whether air quality data or vehicle emissions trends are projected. ·~ Ul- This outlook is based on the APCD' s belief that future growth in both the Los Angeles area and SCAB will not create any locality with a traffic density greater l than any traffic density in the area to date. For the past 25 years, the area around downtown Los Angeles has been the area of maximum traffic density, and therefore

the emissions source area responsible for the maximum effect area measurements.

It is assumed that the traffic density in any future source area will be no

greater than the traffic density in downtown Los Angeles. Thus, since the

vehicular emissions control program will achieve and maintain the air quality

standards in areas affected by vehicular emissions. from downtown Los Angeles, it

will also achieve and maintain them for any area of SCAB.

. Summary , Conclusions and Recommendations

In conclusion, we have shown that a source and effect area analysis of emis­

sions and resulting oxidant is a more reasonable and accurate representation of

the Los Angeles area for air quality analysis than gross integration metho9s such

as the big box technique. It has been shown that motor vehicles are the major, and

almost sole, contributor to the primary HC and NOx emissions in the downtown source

area, which results in the high oxidant levels in the San Gabriel Valley, in fact the

highest in SCAB. An air quality model and vehicle emissions control strategy has

been suggested to meet the oxidant standard by mid-1980' s. 251

We have shown that:

• Only by adjusting the ratio of NOx/HC in the motor vehicle emissions to

permit accumulation of sufficient atmospheric NO to sea venge the normal

atmospheric background oxidant can the standard be attained.

• The APCD strategy which provides for implementation of the present

California interim emissions standards for NOx, HC and CO for new

motor vehicles in California, beginning with the 1975 model vehicles, will

result in compliance with the CO, N02 and oxidant air quality standards by the mid 1980' s, and will maintain this compliance until 1990; and

possibly longer.

• The effectiveness of the present California motor vehicle control program

is easily demonstrable, using air quality data from several areas in Los

Angeles County, 1960-1973.

• To assure achievement and maintenance of the air quality goals as now pre­

dicted, there must be periodic assessments of the effectiveness of the

motor .vehicle control program, followed by corrective actions, if necessary.

What has been accomplished thus far is significant, but much more remains to be done so that the best possible representation of emissions and resulting air quality may be available for use in this air basin. A much better emission inventory defining the spatial and temporal distribution of both mobile and stationary sources is needed. Better statbnary source information is needed to evaluate the local effects of these emissions. Further detailed studies are needed to establish the 252 true relationship between emissions data from vehicle test cycles and the actual operation of vehicles; neither the 7-mode nor the CVS procedure provides a true representation of actual vehicle operation. Further tracer studies to assess the transport and dilution of mobile and stationary source emissions from selected source areas are also needed. . 253

FIGURE I

HYDROCARBONS

1111

STATIONARY SOURCES MOTOR VEHICLES

IUD ■

a: ' - CC I w >- - 1111 -.. ■

1UO

IUD

2, 2l' IS 12 I 4 0 8 12 II 20 74 HUNDREDS OF TONS/DAY HYDROCARBON EMISSIONS FROM MOTOO VEHICLES AND STATIONARY SOURCES IN LOS ANGELES COUNTY

OXIDES OF NITROGEN

I 990 STATIONARY MOTOR VEHICLES SOURCES

IDJO 0■11111111111111111110111•1111111 IIIIIIHIIIIIIIIIHIUII

1180

.llill.L 11!11 Its rd """ l1uu~111111u1111111 IUO ■

2 I O 1 'J 3 HUND REDS OF TONS/DAY OXIDES OF NITROGEN EMISSIONS FROM MOTOR VEHICLES ANO STATIONARY SOURCES IN LOS ANGELES COUNTY i.lll~ ,-~--~ ;i~-=i ,...... _J..~l ,-~~--Z! ~,-:...,-~! •..._;~,L"- I ~~~ '""""~

I.CS ~A@\~1' M

ssmuwmm> •i 70 I s1.,""1 3!:R:l.\!U)U:0 6 70

69• --,__

6S-66* ox

e CORO¥t...... _ 64 ~ IDB RIVERS~ ' '-..., 64 ORAJfD •L., t t 10 miles j I •·same Avg. Cone. Both Years Pigare 2

N YEAR OP HIGHEST OXlDANI' CONCENTRATIONS V, ,+=' Highest Average of Daily -Maiimum One-Hour Concentrations

During July, August & September, 1963-1972

· Source: Air Resources Board ------.------i------tDS &'IJ!t§ N V1 V, -200/o -1~% \ I ldmmprwJ ' -161 ..., .-1AS&Xll·• ..;-.::::z:.----~------...: •

·-i___

\ IIVERSIDI

~ -,.., 70 \ .O.&Y!!! -1 U 70 •L., t t 10 ad.lea } I

Figure 3 CHANGE OP OXIDANT CONCENTRATIONS Percent Change from the Highest Three-Year Average to the 1970-72 Average

Of Daily Maximum One-Hour Con~entrationa for Jul.Y, August & September Source: Air Resources Board 256

FIGURE 4 TYPICAL FLOW OF POLLUTED Am PARCEIS CIUGINATING AT DIFFERENT LOCATIONS IN THE LOS AR:;E~S BASIN - STARTIOO 0900 PST.

OAT

~ , HAW .. ''

(CA l I

TRAJECTORY SUWMAT,IOl4

----- SMOG ~AVS I ·············•NON•SlfOG DAYS I STARTING Tl~: cgxpsy 257

F.iGURE 5 ATMOSPHERIC CONCENTRATIONS* OF CARBON MONOXIDE AND OXIDANT IN

DOWlfl'C"1N LOS AIDELES (SOURCE AREA) AND PASADENA (EFFECT AREA) 1 1960-1972.

LO CARBON MONOXIDE

30 ·········,•• ••• Downtown Los Angeles

20 Pasadena

10

o.._.____.____.______._____._____

OXIDANT

.)

.2 Down~ Los Angeles

.1

o.__.____.___..______.___...... ___ 1960 1962 196L 1966 1968 1970 1972 YEAR 258

FIGURE 6 COMPARISON 01"' CALCULATED AND MEASURED ATMOSPHERIC CONCENTRATIONS OF CARBON MONOXIDE AN1) OXIDES OF NITROOEN IN DCMNTOWN IDS A?IJELES 196o-1972

CARBON MONOXIDE

·········································· ~ ~ ············ _.,,-- ---...... _~ ·········· ~----··-•,w..,-...... _ -..,...--•••

10

o.__...___.___..____.___1111111___...__.....

2.5 OXIDES, OF NITROGEN

2.0 1.5 •····•············., ~ ••••• •••• ...... '1-i 1.0 ··············································· ' o.S --- o.______.___..____.___..____.___...

50 RATIO CO/NOx 40 .....0 +:» C'd p:: 30 ····································••••• ·····-­••••• ...... ~ 20 ••••••• 0 ••• u •·················· 10

0 ,,j 1972 ilI 196o 1964 1968 1970 I'.. YE.AR

Measured~D-owntown Los Angeles (90th percentile of· daily] instantaneous maxima) ...... Calculated - Aver~ge vehicle emissi,ons - Present control program 259

FIGURE 7 EFFECT OF CALIFORNIA 1 s AUTO EXHAUST CONTROL ffiOORA. M ON MAXIMUM CHAMBER OZONE CONCENTRATION.

2.5

CHAMBER OZONE MAXIMUM - PPM .50

i.5 7 .35 t •• flJ ~on ~ ~ Q), bO 1.0 0 .30 Jo. +> onz r 76 •" 11 l' . .20 o.5 .10

o.______111111111111______111111111111______..______

0 0.5 1.0 1.5 . 2.0. 2.5

Hydrocarbons, m-2 (LB-15) - PPM (as Hexane)· .~,a:==-~ ,- ..... ;..;.._...~l y--"'==='--' ;~~--, r--=--~1 ,~. ~-- ~ r---'"~~ ... --

Figure 8 Calculated :t.1ax1mum Levels, Instantaneous and Hourly Average, of' Atmospheric Oxidant Compared to Measured Los Angeles County Maxima-with Projections to 1990 ,.o (California Standards) ,~, / '-/Cal.cul.ated Inst. ?!ax, ~ o.8 /f.. \/ Calculate Max. Hr. Avg. 03 ~ ,,_,,,,.,,,, ! •• "\ I _,,,, ,_.,,,. ,-, i • \ • • • ~ 0 \ •• ' - 0 l \ : •• ?.Ieasured Inst. L!ax. o3 H a.0 8 \ • •: " • ,._ 0 , ;?, o,6 ,. ____., .. V .. ···~"\~ ..!ea~ured ~:. Hr, Avr;, o3 c~. I ~ 0z ~,,~, 0 0 8 r---... \\ ~ o.+ A ~' ~ '\ H N.B.: r.~ima for 197 4 a·s of 12/10/74 -.._ . \ o><- ... Chamber Ozone F ~._ , '\. --- ,._~ '

' -'1L_ ' ' ' 0,2 ""',~, '\. Federal Prima.rfo Air ~uality Standard ~6-- - \UaximumT--~- our-~-- Avera:~e'lr.~ppm------~ ~ ------N ·o I I I I I I I I I I 1 I I I I I I I O'\ 1960 '6i 64 '66 ~i ·-,o '72 '74 ;76 79 ·so ·92 '84 •g, 's9 '9o 0 TBAR (end) 261 FIGURE '; -.OMPARISON OF ATMOSPHERIC OXIDANT TRENDS WITH AVERAGE NCJx AND HC EMISSIONS (Grams per Mile from Average Vehicle)

JOO Number of days state oxidant standara wds equalled or exceeded

--- Azusa __ Pasadena ______Downtown Los Angeles.

20

. 15 u ___ Hydroc_arbons •·····••· Oxides of Nitrogen 1975 and later-assume ·california ARB standards

o.._ _.______._____.._____._____.._____!11!111____. 1965 1970 1975· 198o· 198.S 1990