-------
3.3 SUMMARY OF EMISSIONS DATA
As previously discussed, emissions data, because of the shorter history of their
collection on a systematic basis, are less abundant than air quality data. Further,
unlike air quality data, emissions data are largely inferential (i.e., derived from
emission factors) and partly the result of direct physical measurement.
3.3.1 National Summary
Table 3-10 presents a summary of nationwide emission estimates. The top half
shows the nationwide emission totals resulting from the summation of individual AQCR
totals as found in the State Implementation Plans. AQCR totals were obtained by means
of a comprehensive emission inventorying technique. This technique involves estima-
ting a majority of the emissions on a point-by-point basis, where such parameters as
fuel rates, process rates, control equipment, and efficiencies are known. In the case
of area sources, for example, motor vehicle emissions, vehicle miles of travel, aver-
age vehicle speeds, and vehicle population and age distribution are all considered in
determining the total emissions for that source category.
The SIP emissions data presented should be viewed with some caution. First, be-
cause several Regions do not contain a complete set of data for all pollutants,
Table 3-10. COMPARISON OF SIP EMISSIONS
AND 1970 NATIONWIDE ESTIMATES
(106 tons/yr)
Source category
SIP emissions3
Transportation
Fuel combustion in
stationary sources
Industrial processes
Solid waste disposal
Miscellaneous
Total
1970 nationwide estimates'3'0
Transportation
Fuel combustion in
stationary sources
Industrial processes
Solid waste disposal
Miscellaneous
Total
SOX
0.8
28.9
7.8
0.1
0.2
37.8
1.0
26.4
6.4
0.1
0.2
34.1
PM
1.1
9.9
10.3
11.1
1.1
23.5
0.8
6.7
13.3
1.4
4.0
26.2
CO
100.9
1.5
10.3
3.4
2.3
118.4
111.0
0.8
11.4
7.2
18.3
249.0
HC
18.0
1.0
4.3
1.2
1.5
26.0
19.5
0.6
5.5
2.0
7.3
34.9
NOX
11.6
9.2
0.6
0.3
0.2
21.9
11.7
10.0
0.2
0.4
0.5
22.8
In-
Source: State Implementation Plans.
Source: GAP Reference Book of Nationwide Emissions, 1970.
ternal Document, ATD, NSIS, Durham, N.C.
GNot adjusted for 1975 motor vehicle testing procedure or changes
in estimating procedures as discussed in trends section.
3-44
-------
nationwide totals derived from these data will not be complete. Second, the emissions
for all Regions are not necessarily for the same year. Most of the existing data are
referenced to the calender year 1970. Third, it is not known whether all States used
the same emission factors or estimating techniques in deriving their emission totals.
For example, the ratio of CO from transportation to regional population varies to a
much higher degree than one would expect because of differences in traffic flow and
vehicle miles of travel.
Finally, these SIP emissions were calculated on the basis of the 1972 automotive
testing procedure. Presently, emissions are calculated using the 1975 testing proce-
dure. This change in testing procedure causes a corresponding change in nationwide
emission rates that is not reflected in Table 3-10. For purposes of comparison,
nationwide emissions for 1970 are shown based on the 1972 procedure. Tables pre-
sented subsequently in this report and in the Emissions Trends section show the
emissions based on the 1975 procedure and, thus, are the most up-to-date EPA estimates.
The bottom half of Table 3-10 presents 1970 nationwide emissions. These numbers
were derived from nationwide totals of fuel consumption, process weights, and overall
average industry control efficiencies. For motor vehicles, nationwide averages of
vehicle population and age distribution, average route speeds, and emission factors
were used to derive nationwide totals. Comparisons made between the results of these
two techniques should be viewed with these differences of procedure in mind.
3.3.2 AQCR Summary
Appendix H is a summary of detailed emission inventory data as submitted by the
States in their implementation plans. A separate entry is shown for each of the five
major air pollutants (SC>2, PM, CO, HC, and NOX) with breakdowns for the five most im-
portant source categories.
These emission values are the numbers used by the States in control strategy cal-
culations. They are representative of 1970 for most of the States, but some data are
reported for 1966, 1968, and 1969. These emissions estimates, together with current
air quality data, were used in rollback models to determine the percentage reduction
in emissions necessary to attain NAAQS.
Three different summaries are presented. One shows the emission totals for the
entire AQCR for interstates only, the second is a summary of AQCR portions within
States, and the third shows statewide totals. (All three summaries, in addition, con-
tain the emission densities by pollutant in both tons per square kilometer and tons
per person.)
No attempt has been made to compare Regions according to pollutant density in
order to develop an emissions priority classification system. The primary reason
is that the emission estimates were derived and calculated from a variety of sources.
Since estimating techniques and, perhaps, emission factors varied from state to
state, any comparisons made between States or between Regions would be of limited
value. Also, factors such as meteorology, topography, and source location must be
considered.
3-45
-------
-------
4. AIR QUALITY AND EMISSIONS TRENDS
Information derived from air quality monitoring programs serves two fundamental
purposes. First, the data they yield provide a quantitative assessment of air qual-
ity on a nationwide basis. This information is essential in order to identify prob-
lems requiring particular attention and remedial control action. It has already been
explained in this report how air quality information is used to identify the relative
severity of regional air contamination by specific pollutants through the Priority
Classification system. Second, air quality data, reflecting successive measurements
of the same pollutant over extended periods, provide an indication of the way in
which particular concentration parameters vary with time. These variations are usu-
ally quite complex because of the variety of factors that affect them (Appendix D).
Assuming, however, that through appropriate analytical procedures, meaningful trends
can be identified and described, the value of sequential pollutant measurements on an
areal basis can be quite useful. This is because such trends could provide a. clear
picture of the rate at which SIP control measures are effective in achieving NAAQS.
A considerable amount of effort has been expended in the development and applica-
tion of statistical techniques for the determination of basic trend information from
diffuse and complex data sets. Analytical procedures developed for this purpose have
been established to the point that trend analyses can now be applied.
This chapter is largely devoted to the analyses of air quality data available at
this time with the view of presenting such long- and short-term trends for specific
pollutants as the current data can justify. The Office of Air and Water Programs, on
the basis of detailed studies, is oriented to the view that the difficulties in gen-
erating useful and indicative trend analyses at this time are caused less by the in-
herent complexities of the problem than they are by areas of incompleteness and un-
certainties of information reliability that pervade the available data base. As dis-
cussed earlier, however, it is expected that, as the monitoring activities under the
SIP's become fully operational, both the quality and quantity of the data base will
progressively improve and that this improvement will be reflected in a higher level
of reliability of future trend analyses than is possible at this time.
In addition to trends in air quality, this chapter also presents a summary
account of emissions trends on a nationwide basis by source category. As previously
discussed, similar information on an AQCR basis is not available. Because of the
causal relationship between emissions and air quality, it would be very desirable to
have emissions information for each AQCR for a time period corresponding to that for
which air quality data exist. Emissions information of this kind would provide in-
sight into the relationship between air quality trends and the enforcement of emis-
sions control measures.
4.1 NATIONWIDE EMISSIONS TRENDS
Emissions trends discussed are based on data for five major air pollutants (S02,
PM, CO, HC, and NOX) over the period 1940 to 1970.* Levels of emissions were estima-
ted by means of various indicators such as national totals of fuel consumption, re-
fuse burning rates, vehicle miles of travel, industrial production rates, and control
*A much more detailed discussion, including tables and methodology, is presented in
Nationwide Air Pollutant Emission Trri.ds, 1940-1970, AP-115.
4-1
-------
efficiencies. Average emission factors, which relate these indicators to emission
rates for specific source categories, were used in deriving the estimates. It is
believed that these estimates provide fairly reliable representations of nationwide
emission totals.
The accuracy of the estimates for different pollutants varies. For CO, NOX, and
SC>2, the estimates should be reasonably good because detailed studies have been com-
pleted and overall source control efficiencies are known. For particulate matter and
hydrocarbons, information on the extent and degree of control exercised in some source
categories is not yet complete; therefore, estimates of PM and HC emission levels are
not as accurate.
Yearly fluctuations in emission levels for some source categories are difficult
to detect. For example, changes in the sulfur content of fuels can vary significant-
ly from one year to the next. In the absence of continual and systematic updating of
information, only estimates of such changes can be made. Over a longer time-frame
of 5 to 20 years, however, not only are mere fluctuations easier to detect, but their
impact is more readily apparent than is true on a year-to-year basis.
Estimated nationwide totals of emission levels over a 30-year time span are pre-
sented in Table 4-1. The yearly emission rate is categorized according to controll-
able and miscellaneous (uncontrollable) emissions.
These estimates reflect the latest EPA data on emission factors and source acti-
vity rates as well as the use of the 1975 testing procedure method of estimating
motor vehicle emissions. The 1975 testing procedure is thought to be more repre-
sentative of actual driving conditions that the old 1972 procedure. Miscellaneous
sources include forest fires, structural fires, and other pollutant origins over
which man has no real effective control. It is important to note that not all
natural sources of pollution are included because of the lack of information on
totals or emission factors. Figures 4-1, 4-2, and 4-3 depict the change in emission
rate with time. Pollutants related to the quantity of fuels burned, i.e., CO, HC,
and NOx, increase almost logarithmically. Data for CO and HC suggest the beginning
of the anticipated downward trend in 1968 that was coincidental with the advent of
motor vehicle controls. Pollutants more related to the quality of fuels, i.e., S02
and PM, show a more erratic behavior with time.
Over the 30-year interval, total CO emissions increased at a compound rate of
1.5 percent per year. The emissions from automotive sources, however, have increased
at an annual rate of nearly 4.0 percent. The difference in growth rates between auto-
motive CO and total CO is accounted for by a proportionally greater reduction in
emissions from stationary fuel combustion and miscellaneous sources than from automo-
tive sources.
Hydrocarbon emissions increased about 1.7 percent annually from 1940 to 1970.
Automotive sources alone represent a rate increase of nearly 3.3 percent. The control
of hydrocarbons from the crankcase (or blowby) reduced average per-vehicle emissions
by one-third in the early 1960's. This resulted in an HC emission growth rate from
vehicles lower than the CO growth rate.
For the period 1940 to 1970, the growth rates of NOX emissions from motor vehi-
cles and stationary fuel combustion sources were very similar, being 4.8 percent and
3.7 percent, respectively. Over the period 1940 to 1960, however, the average road
vehicle emission growth rate was 4.9 percent, and the stationary fuel combustion
source growth rate was only 2.0 percent. During the period I960 to 1970, these trends
were reversed, and the road vehicle emission growth rate was 4.6 percent as opposed
to a 7.3 percent increase for stationary fuel combustion sources. Over the last 10
years, NOX emissions from steam-electric power plants increased at a rate of 7.4 per-
cent.
4-2
-------
Table 4-1. ESTIMATED TOTAL
NATIONWIDE EMISSION LEVELS, 1940-1970
(106 tons/yr)
1940 Controllable
Misc. (uncontrollable)3
Total
1950 Controllable
Misc. (uncontrollable)
Total
1960 Controllable
Misc. (uncontrollable)
Total
1968 Controllable
Misc. (uncontrollable)
Total
1969 Controllable
Misc. (uncontrollable)
Total
1970 Controllable
Misc. (uncontrollable)
Total
S02
22.2
0.6
22.8
24.3
0.6
24.9
22.6
0.6
23.2
30.5
0.6
31.1
31.9
0.2
32.1
33.3
0.1
33.4
PM
19.2
25.7
44.9
20.8
12.4
33.2
21.0
8.9
29.9
22.5
5.9
28.4
22.8
12.2
35.0
22.3
3.2
25.5
CO
42.5
30. q
72.5
62.3
20.6
82.9
79.3
19.3
98.6
93.4
18.0
111.4
97.6
17.5
115.1
96.0
4.7
100.7
HC
10.1
D.5
16.6
15.6
6.2
21.8
18.8
7.0
25.8
22.1
7.6
29.7
21.9
6. '•'..
28.7
22.5
4.?
27.3
•iox
5.5
1.0
6.5
8.2
0.6
8.8
10.9
0.5
11.4
19.1
0.4
19.5
20.6
0.5
21.1
22.0
0.1
22.1
Uncontrollable sources include forest fires, structural fires, coal
refuse banks, some agricultural burning, and some solvent
evaporation.
Figure 4-2 presents the SC>2 emissions from 1940 to 1970. The total emissions
increased very slightly from 1940 to 1960, but then increased rapidly at a rate of
2.6 percent per year from 1960 to ..970. Emissions from steam-electric utilities
increased logarithmically over the 30-year interval at a rate of around 6.6 percent
per year, nearly five times the rate for S02 overall. Emissions from industrial pro-
cesses have also increased over the same time period, but at a rather low rate (1.9
percent). All other source categories show a decrease in emissions with time.
Particulate emissions from controllable sources (Figure 4-3) have shown almost
no change with time (20 million tons in 1940 versus almost 22 million in 1970). This
is attributed, in part, to changing fuel patterns and increased effectiveness of con-
trols on power plants and industrial process sources. Process-loss emissions have
increased very slowly, however, over the 30-year interval, whereas overall stationary
fuel emissions have declined at a fairly constant rate of 1.1 percent. The rates of
change for the various pollutant emission levels by source category are presented in
Table 4-2.
4-3
-------
1940
1950
1970
YEAR
1940
Figure 4-1. Nationwide emissions for HC,
GO, and NOX (1940-1970).
1960
1970
YEAR
Figure 4-2. Nationwide SOo emissions
(1940-1970).
4.2 NATIONWIDE AIR QUALITY TRENDS
Air quality trends are assessed by the measurement of changes in specific pollu-
tant concentrations on a pollutant-by-pollutant basis. At this time, it is not feas-
ible to evaluate air quality on the basis of a single number or index that would com-
bine the contributions of all pollutant concentrations. The techniques employed con-
sist essentially of partitioning the historical data records into discrete time inter-
vals. Valid data for these intervals are then successively compared to determine the
magnitudes and directions of changes in pollutant level concentrations. The lengths
of the intervals for which the comparisons are made are determined, in large part, by
whether short- or long-term trends are being studied. In general, short-term trends
may exhibit considerable variability because of transient effects such as those of
meteorological origin. Fluctuations of this kind tend to be averaged out over long
time intervals, however.
This chapter presents analyses of air quality trends based on NASN and CAMP
data on both a regional and site basis.
4.2.1 NASN Trends
This section examines national and geographic trends in total suspended particu-
lates and sulfur dioxide by analyzing data collected through the National Air Sur-
veillance Networks. As previously discussed, the NASN is a Federally funded air qual-
ity monitoring network operated with the assistance and cooperation of State and lo-
cal agencies. The NASN program was begun in the mid-1950's with 17 urban stations,
and grew to approximately 150 TSP-sampling stations located throughout the United
States by the mid-1960's. The number of stations that comprise the NASN has fluctu-
ated from year to year and reached its zenith in 1971-72 when over 260 TSP and 200
S02 stations were maintained. Presently, there are some 258 TSP and 202 SC>2 sampling
stations located in the 50 states and Puerto Rico.
When the NASN was established, resource limitations dictated placement of only
one station in each major urban area. Stations were located primarily in the down-
town or center-city areas and, hence, do not necessarily reflect the "worst" air qual-
ity to be found through heavily industrialized portions of many cities. For this
4-4
-------
1950 1960
YEAR
Figure 4-3. Nationwide paniculate matter
emissions (1940-1970).
Table 4-2. RATES OF CHANGE FOR NATIONWIDE EMISSIONS
(percent)
Pollutant category
CO - Total
CO - Road vehicles
HC - Total
HC - Road vehicles
NOX- Total
NOX- Road vehicles
NOX- Fuel combustion
NOX- Steam- electric utilities
SOX- Total
SOX- Fuel combustion
SOX- Steam-electric utilities
SOX- Industrial process
PM - Total
PM - Industrial process
PM - Fuel combustion
PM - Steam-electric utilities
Population - U.S. total
1940-1970
1.1
4.0
1.7
3.3
4.2
4.8
3.7
7.1
" •}
1.5
6.6
1.9
-1.9
1.4
-1.1
2.1
1.45
1940-1960
1.5
4.3
? ?
t.t
4.3
2.9
;.9
2.0
6.9
0.6
0.2
6.5
1.3
-2.0
1.5
-1.1
4.1
1.53
1960-1970
0.2
3.4
0.6
1.0
6.8
4.6
7.3
7.4
2.6
4.2
6.7
3.0
-1.6
1.1
-1.1
-1.8
1.27
reason, there may be differences between the air quality measurements summarized in
this section and those obtained by State monitoring systems used in developing State
Implementation Plans.
4-5
-------
The trends discussed are based on both annual means and maximum 24-hour values.
Urban, nonurban, and geographic trends are examined over a 12-year period for TSP and
over an 8-year period for S02- For this analysis, the period 1960 through 1971 has
been divided into three intervals consisting of the years 1960 through 1963, 1964
through 1967, and 1968 through 1971. The analysis, while focusing primarily on air
quality concentration levels and trends over the extended 12-year period, is also
designed to present limited evaluation of trends during the most recent interval,
1968 through 1971. This is accomplished by utilizing both statistical tests and
graphical presentations. Long- and short-term trends in annual means are assessed
by statistical tests based on comparisons among annual geometric means for various
years. A tabulation of individual NASN stations showing yearly annual averages and
trend summaries is presented in Appendix F. Graphical presentations, utilizing com-
posite averages of annual geometric means, annual arithmetic means, and 24-hour
maximum concentrations appear later in this chapter.* In forming the composite aver-
age, missing values were derived by interpolation in order to form a complete set of
values at a given site for the entire time period considered.
4.2.1.1 Total suspended particulates
4.2.1.1,1 Urban trends - A summary of urban trends is presented in Table 4-3. For
the 12-year period, the averages of the annual geometric mean TSP values for 1960
through 1963 are compared with those for 1968 through 1971; for the 8-year period,
the equivalent comparison is made between 1964 through 1967 and 1968 through 1971;
for the 4-year period, a similar comparison is made among recent short-term changes
since 1968. All comparisons are made for the same set of ranges of particulate levels.
Significant upward and downward trends are indicated as well as a "no change" cate-
gory. The trends are grouped according to the air quality in the base period - that
is, the air quality of the earliest interval. The last line (Total) indicates the
total number of stations showing trends in each of the time periods. From the table,
it can be seen that of the 116 stations in the 12-year period, 66 exhibited downward
trends, 8 displayed significant upward trends, and 42 indicated no change. This long-
term decline in total suspended particulate matter is essentially reiterated in the
8-year period. Of the 119 stations, 53 display a downward trend, whereas only 3 de-
monstrate a significant upward trend. The most recent short-term picture is some-
what different in that no significant net trend is discernible.
Table 4-3. SUMMARY OF TRENDS IN ANNUAL MEAN SUSPENDED PARTICULATE MATTER
CONCENTRATIONS AT URBAN NASN STATIONS, 1960-1971
Annual TSP
concentrations
in base
period,
Jjg/m3
150 < 250
90 < 150
60 < 90
< 60
Total
Number of stations
Long-term: 12 years
60-63 avg. to 68-71 avg.
Up
2
6
8
No
change
4
13
20
5
42
Down
8
44
13
1
66
Total
12
59
39
6
116
Last 8 years
64-67 avg. to 68-71 avg.
UP
2
1
3
No
change
1
26
29
7
63
Down
4
32
17
53
Total
5
60
47
7
119
Short-term: 4 years
1968 to present
Up
3
9
9
21
No
change
2
48
72
13
136
Down
2
12
.. 5
20
Total
6
63
86
22
177
*It should be noted that for 24-hour measurements, the maximum concentration is equi-
valent to the 99th percentile for a sample size of 26.
4-6
-------
Individual short-term trends must be evaluated in the context of long-term trends.
For example, only two stations with long-term upward trends also show significant upward
trends in the last four years. Seven stations, which appear to demonstrate statisti-
cally significant increases in the last four years, in fact, show minor reversals of
much larger significant downward trends over the whole 12-year- period. In a more de-
tailed analysis of the short-term trends, it was found that there was an apparent asso-
ciation between sites that showed an upward trend and those that also experienced de-
creased rainfall. This is discussed more fully in Section 4.2.1.1.4, Geographic Trends
for TSP.
Table 4-3 also indicates that downward trends are associated with higher concen-
trations during the base period (>90 yg/m3), whereas the upward trends are associa-
ted with lower concentration levels (<90 pg/m3). This is also true for the change in
the maximum 24-hour TSP concentration as shown in Table 4-4. It should be noted that
statistical tests were not employed for determining trends in maximum daily TSP
measurements. Accordingly, Table 4-4 displays the direction of changes UP and DOWN,
and change magnitudes are presented as percentages. This table shows that within the
downward changes, the larger percentage decreases are associated with the higher con-
centrations for the base period and, for the positive changes, the larger percentage
increases are associated with the lower concentrations for the base period. There-
fore, both the trends in the annual geometric means and the changes in the maximum
24-hour TSP concentrations demonstrate that locations with the worst problems have
shown the most improvement while the cleaner areas have shown a tendancy to degrada-
tion. It should be noted that the recent time interval (1968 to present) contains
a larger proportion of positive changes than do the prior periods, but these are
still largely at smaller concentration levels.
Table 4-4.
SUMMARY OF CHANGE IN THE MAXIMUM DAILY SUSPENDED PARTICIPATE MATTER
CONCENTRATIONS AT URBAN NASN STATIONS, 1960-1971
Number of stations
TSP
concentrations
period, vg/nr
> 250
50 < 250
90 < 150
60 < 90
Total
60-63 avg. to 68-71 avg.
Total
Down
54
39
7
0
100
Up
4
7
4
1
16
Percent change
<-25
44
24
4
72
+25
12
20
7
1
40
>25
2
2
4
64-67 avg. to 68-71 avg.
Total
Down
47
41
11
99
Up
4
10
5
1
20
Percent change
<-25
37
30
5
72
±25
14
14
10
38
>25
7
1
1
9
1968 to present
Total
Down
45
41
10
2
98
Up
15
37
22
4
78
Percent change
<-25
31
12
2
45
±25
21
54
20
3
98
>25
8
12
10
3
33
In summary, both the majority of the annual means and of the maximum 24-hour
values declined over the 12-year period. Most of the decline appears to have occurred
prior to 1968. Figures 4-4 and 4-5 display this trend. In Figure 4-4, the composite
mean is 110 vig/m^ for 1960 and 85 yg/m3 for 1971. In Figure 4-5, both the composite
averages of the maximum values and the 90th percentiles of the annual maximum values
are plotted. Note that the plots of both the 90th percentiles and the composite aver-
ages smooth out the extreme fluctuations of the annual and maximum values. The com-
posite average of the maximum values is 270 yg/m^ for 1960 and 200 ug/m^ for 1971.
The plot of the 90th percentile also exhibits a downward trend. Note that the range
in annnal values appears to be decreasing as well.
4.2.1.1.2 Comparison to standards - Table 4-5 presents, year by year, the percentage
of NASN stations whose measurements exceed the primary and secondary annual mean stan-
4-7
-------
200
150
1=
UJ
o
o:
I-
UJ
S
UJ
t 100
50
10
»
•
^^
•
•- -•
•
•
*• .
»
•— •,
^— —
i
**
JRA
JRA
i
•— - •
»
-^
f
•
NGE OF I
NGEOF
«
i
jd
1
SE
> •
Tec
18
JRBAN G
40NURB/I
1
i
OMPOSI1
5 URBAN
*^
•RINIARY
J_
•
EOMETRIC MEANS
NGEOM
i
i
E AVER
LOCATI
•*^^
STAND;
1 '
CONDARY STAND
.
•
•
)MPOSITf
NONURB
•
t
ETRIC ME
i
i
kGE
ONS
^
RDx>
ARD^
• .
ANS
•MMMM
'
•
"^
: AVERAGE ^"^^
AN LOCATIONS
i
•
•
_^
r
1
•
•^
S"
^
i^-««_
•
1
._
•
r
I960 1961 1%2 1963 1964 1%5 1966 1967 1968 1969 1970 1971
YEAR
Figure 4-4. Composite annual means of total suspended paniculate at urban and nonurban
NASN stations.
dards and the primary and secondary 24-hour maximum standards. Although the popula-
tion of stations changes from year to year, the percent of stations exceeding each of
the standards did decrease over the 12-year period.* There is no bias attributable
to the change in station population. A subset of 95 stations, which had at least one
*This population of stations is a subset of the total number of stations that were
compared in Table 3-8.
-------
1000
800
600
ce
o.
o
UJ
o
200
I RANGE OF URBAN ANNUAL
MAXIMUM VALUES
COMPOSITE AVG
OF MAXIMUM
VALUES
i
1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
YEAR
Figure 4-5. Composite average and 90th percentiles of annual maximum daily suspended par-
ticulate matter concentrations at 95 urban NASN stations.
data point in each of the three 4-year intervals, showed essentially the same decrease
in the percent of stations exceeding each of the standards over the 12-year period.
From the early sixties to the early seventies, the percentage of stations exceeding
the primary annual standard decreased from approximately 80 to approximately 60 per-
cent; those exceeding secondary annual standards decreased from approximately 90 to
approximately 80 percent; and those exceeding the primary and secondary 24-hour max-
imum standards decreased from approximately 40 to approximately 20 percent, and 90
to 70 percent, respectively.
4.2.1.1.3 Nonurban trends - Trends at nonurban stations were also examined in a sim-
Over the 12-year period (I960 through
The downward trends
ilar manner and are summarized in Table 4-6.
1971), the majority of stations showed no significant change.
that appear in the analysis of the last 8 years have been effectively cancelled by
the upward trends in the last 4 years. This effect can also be seen in Figure 4-4
as the dip in the nonurban composite average for 1968 and 1969. It is interesting to
note that 9 of the 10 significant upward trends in the 1968 through 1971 period
occurred in areas with decreased rainfall during that time period. Only Cape Hatter-
as showed a significant increase associated with increased rainfall. This is dis-
cussed in greater detail in the following section.
4.2.1.1.4 Geographic trends - Station locations were categorized according to the
four geographic regions defined by the Bureau of the Census: North Central, North-
east, South, and West. These regions are outlined in Figure 4-6.
4-9
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Table 4-6. TRENDS IN ANNUAL MEAN SUSPENDED PARTICULATE MATTER
CONCENTRATIONS AT NONURBAN NASN STATIONS, 1960-1971
Type of trend
Up
No change
Down
Low (< 10 ug/m3)
No. of stations
Number of stations
12 years
1960-1971
2
11
5
--
18
Last 8 years
1964-1971
1
9
11
--
21
Last 4 years
1968-1971
10
17
0
2
29
Composite TSP annual averages (Figure 4-7) for the Northeast and North Central
United States have been consistently greater than those for the South and the West.
The composite averages for each group showed a decrease in TSP over the entire 12-
year period (1960 through 1971).
Although the Northeast had the highest concentration during the early sixties,
its level is now comparable with that of the North Central region. The West, whose
TSP concentration was initially higher than that of the South, improved greatly to-
ward the mid-sixties. Because of a minor trend reversal in the early seventies, how-
ever, its TSP level is now comparable to that of the South.
The statistically significant trends indicated in Table 4-7 show that a major-
ity of sites in each region have demonstrated improvement in air quality over the
long-term periods. Some minor differences do exist among the regional trends. The
West, although showing the greatest overall improvement since the early sixties, has
shown an increase in the number of stations undergoing degradation during the most
recent 4 years. In fact, upward trends seem to be most prevalent west of the Missis-
sippi, as shown in Figure 4-8. Some upward trends also occurred in the New England
States. The geographical pattern of these upward trends, which occurred within a
relatively short-term period (4 years), suggested possible meteorological influences.
Of the various meteorological parameters examined, rainfall showed the greatest evi-
dence of a possible association with TSP trends. To test this, average annual rain-
fall data were extracted from the Local Climatological Data summaries for about 70
National Weather Service stations distributed across the country. Averages for the
first 2 years (1968 and 1969) were compared with those for the second 2 years (1970
and 1971), and the net rainfall changes were noted. It was found that, for stations
showing a significant upward trend in TSP west of the Mississippi, 8 of 13 urban sta-
tions and all 6 nonurban stations were located in areas in which rainfall tended to
decrease during the 4-year period. In the New England States, all three urban sta-
tions (which showed increasing concentrations) and the sole nonurban station were al-
so in areas where average rainfall showed a decreasing tendency. In addition, two
other nonurban sites east of the Mississippi showed upward trends in areas of de-
creased rainfall. A corresponding association could not be found between areas of
decreasing TSP trends and increasing rainfall.
The above discussion may suggest that the decrease in rainfall in certain areas
toward the latter part of the period may have caused significant upward trends in
TSP at some stations. Certainly, decreased moisture from rainfall may increase parti-
culate matter entrained into the atmosphere from the surface and may decrease the
chances for rainfall removal of airborne particulates (See discussion in Appendix D).
The extent that precipitation changes may have contributed to TSP trends cannot be
quantified at present, however. Therefore, the apparent association found between
upward TSP trend and decreased rainfall, although notable, should not be taken as the
sole reason or even the primary explanation for the observed trends. Other forces
4-11
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100
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LU
O
75
50
25
NORTHEAST
NORTH CENTRAL
WEST
SOUTH
1960
1965
YEAR
1971
Figure 4-7 Regional comparisons of com-
posite anrjal mean suspended particulate
matter concentrations at urban NASN stations.
Table 4-7. REGIONAL SUMMARY OF TRENDS IN ANNUAL MEAN SUSPENDED PARTICULATE
MATTER CONCENTRATIONS AT URBAN NASN STATIONS, 1960-1971
Regions
North Central
Northeast
South
West
Puerto Rico
Total
Long-term (12 years) ,
1960-1971
Up
3
2
3
0
0
8
No
change
12
11
14
5
0
42
Down
24
14
11
17
0
66
Total
39
27
28
22
0
116
Last 8 years,
1964-1971
Up
1
1
0
1
0
3
No
change
24
9
14
16
0
63
Down
16
13
16
8
0
53
Total
41
23
30
25
0
119
Short-term (4 years),
1968-1971
UP
4
5
3
7
2
21
No
change
41
32
38
22
3
136
Down
6
4
8
2
0
20
Total
51
41
49
31
5
177
that were also at work in determining the trends include changes in emission regula-
tions, technology, fuel use, and weather factors such as winds, temperature, humid-
ity, etc.
The composite averages of the maximum values for each of the regions were plot-
ted for the years 1960 through 1971 (Figure 4-9). The trends in composite average
maximum values follow the trends displayed in Figure 4-7 for composite annual avera-
ges. Over the 12-year period, these trends declined in each of the regions.
4.2.1.2 Sulfur dioxide
4.2.1.2.1 Urban trends - The analysis of S02 trends covers the 8-year period, 1964
through 1971, because valid data prior to 1964 are too sparse to support generaliza-
tions about the national situation. Only 32 NASN stations had sufficient S02 data
over the 8-year period to permit trend assessment. The graph of composite annual
arithmetic mean concentrations of sulfur dioxide at 32 urban NASN stations, Figure
4-10, shows a marked decline over the 1964 through 1971 period. The composite average
of the maximum values and the range of the annual maximum values are presented in Fig-
ure 4-11. These trends demonstrate a marked decline over the 8-year period. This
4-13
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YEAR
Figure 4-9.
Regional comparisons of
com-
posite average annual maximum daily sus-
pended paniculate matter concentrations a
urLan NASN stations.
0
t
—
—
[RANGE OF ARITHMETIC MEANS
—
^
PRIMARY>.
— i — i — ^ — i- — i— 5-
AMBIENT AIR | |
STANDARDS SECONDARY^
—--—
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AVERAGED
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1964 1967 1971
YEAR
Figure 4-10. Composite annual means of sul-
fur dioxide at 32 NASN stations.
QUU
600
400
200
n
—
Tl
i
RANC
DA
,EOF
ILYV
MAXin
i\LUES
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COMPOSITE AVERAGE
MAXIMUM VALUE
L + + + .
1964
• j —
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1967 1971
YEAR
Figure 4-11. Composite average of annual
maximum daily sulfur dioxide concentrations
at 32 urban NASN stations.
4-15
-------
decline is attributable, in some measure, to the institution of regulations in various
sections of the country requiring reduced sulfur content in coal and fuel oils.
The arithmetic annual means are shown both in Figure 4-10 and also later with
respect to standards. Because the distribution of air quality measurements is gen-
erally considered to be more nearly log-normal than symmetrical, geometric means have
also been used in the statistical analysis of SC>2 trends in an attempt to improve the
sensitivity of the tests. The choice of mean should not affect overall trend patterns.
Table 4-8 shows a net downward trend over the 8-year period. More recent trends
in SC>2 are evidenced by examining data from a total of 95 stations that had sufficient
data during the last 4-year interval to be meaningful. Of the 95 stations, nearly
half (42) show downward trends, and another third (33) have annual means so low (less
than 10 yg/m3) that detection of trends is both statistically difficult and unrealistic.
Thus, the rate of improvement in S02 air quality has been dramatic enough to be read-
ily detectable even over the past few years.
Table 4-8. SUMMARY OF TRENDS IN ANNUAL MEAN SULFUR DIOXIDE
CONCENTRATIONS AT URBAN NASN STATIONS, 1964-1971
Type of trend
Up
No change
Down
Low (< 10 yg/m3)
Total No. of stations
Number of stations
8 years
1964-1971
1
12
19
--
32
Last 4 years
1968-1971
3
17
42
33
95
The change in the maximum 24-hour S02 values for urban NASN stations is shown
in Table 4-9. The changes are overwhelmingly downward, 31 down and 1 up. In the
most recent 4-year period, 62 are down and 31 are up. The analysis of the maximum
24-hour S02 values supports the earlier finding of a marked decline in S02 levels at
urban stations.
Table 4-9. SUMMARY OF CHANGE IN MAXIMUM S02 DAILY CONCENTRATIONS AT URBAN
NASN STATIONS, 1964-1971
S02
concentration
in base
period,
ug/m3
> 300
180 <_ 300
90 <_ 180
30 <_ 90
<_ 30
Total
Number of stations
1964-1967 avg. to 1968-1971 avg.
Total
Dqwn
6
6
10
9
31
Up
1
1
Percent change
<-25
6
6
9
4
25
± 25
1
6
7
> 25
1968 to present
Total3
Down
7
12
21
12
10
62
Up
3
7
14
7
31
Percent change
<-25
9
19
10
4
43
± 25
7
5
5
9
6
31
> 25
1
4
7
7
19
Two stations showed no change.
4-16
-------
4.2.1.2.2 Comparison to standards - Table 4-10 presents, year by year, the percen-
tage of NASN stations exceeding the primary and secondary annual mean standards and
the primary and secondary 24-hour maximum standards. Although the population of
stations changed from year to year, the percent of stations exceeding each of the
standards decreased dramatically over the 8-year period. In 1964, for 18 stations,
33 percent exceeded the primary annual mean standard, 44 percent exceeded the secon-
dary annual mean standard, 11 percent exceeded the primary 24-hour maximum standard,
and 28 percent exceeded the secondary 24-hour maximum standard. By 1971, only 0 to
2 percent exceeded any one of the standards. This reemphasizes the sharp decline in
SC>2 levels over the 8-year period.
4.2.1.2.3 Nonurban trends - Data for sulfur dioxide at nonurban stations are too
sparse to justify a formal analysis, but it can be noted that annual mean S02 concen-
trations at the Kent County, Delaware, station have declined from 21 jag/m^ in 1969 to
5 jug/m^ in 1971, whereas the Acadia National Park, Maine, station has held essentially
constant in the 7 to 9 jag/m^ range over the same 3 years .
4.2.1.2.4 Geographic trends - The four regions, North Central, Northeast, South, and
West, as defined earlier, were examined for trends in SC>2. Composite annual averages
for each of the regions are displayed in Figure 4-12. It can be seen that each of
the regions exhibits a downward trend in S02 over the 12-year period. The Northeast,
with the highest composite average in 1964 of 88 ;jg/m3, showed the most dramatic de-
crease with a composite average of 41 ,ug/m3 in 1971. Similarly, the North Central
region has declined from 49 jag/m^ to 24 ug/m3, the South from 34 ug/m^ to 14 ;ug/m3,
and the West from 25 ug/m3 to 14 ug/m^ during the same time period.
The composite average of the maximum values for each of the regions was plotted
for the years 1964 through 1971 in Figure 4-13. The trends in composite average max-
imum values generally follow the trends shown in Figure 4-12 for composite annual
averages. With the exception of a minor reversal in 1969 for the West, the trends in
each of the regions are on the decline.
The statistically significant trends indicated in Table 4-11 show that each of
the regions has demonstrated improvements in SC>2 over the 8- and 4-year periods.
Only 1 site in the North Central region exhibited a significant upward trend in the
8-year period out of a total of 32 in all the regions. Of tht 95 stations in the 4-
year period, only 3 exhibited a significant upward trend. Two of these are located
in the Northeast, and one is in the South. The trends in each of the regions follow
the national trend of a marked decline in S02 at urban stations.
4.2.1.3 Interpretation of results - The result of the NASN S02 analysis has shown
a very pronounced downward long-term trend over the 8-year period, with the composite
average dropping over 50 percent. A review of nationwide emissions data over the
same time interval, however, shows an increase in 803 emissions from approximately
27 million tons in 1964 to over 33 million tons in 1971 (an increase of over 20 per-
cent) . Thus, an apparent inconsistency exists between rising nationwide S02 emis-
sions on the one hand and decreasing ambient concentrations on the other.
The following considerations may be helpful in explaining this apparent incon-
sistency. First, emissions are determined for the nation as a whole, whereas air
quality data are generally collected for specific sites in center-city locations.
Thus, the impact of changes in and about the sampling sites would have dramatic re-
sults on local air quality measurements but insignificant impact on nationwide emis-
sions. Second, because of several factors, S02 emission rates in most urban areas
are declining. The use of coal in residential and small commercial sources is prac-
tically non-existent. Cleaner fuels such as natural gas and distillate fuel oils
have replaced coal to a large extent. The impact on total nationwide emissions as a
result of this fuel replacement is relatively small, but the effect on local air
quality is pronounced. Third, large point sources such as power plants are not able
to locate near or in center-city areas. Strict local regulations and fuel avail-
4-17
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t 40
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NORTHEAST
NORTH CENTRAL
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WEST
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YEAR
Figure 4-12. Regional comparisons of com-
posite annual arithmetic mean sulfur dioxide
concentrations at urban NASN stations.
300
NORTHEAST
NORTH CENTRAL
SOUTH
WEST
1
>-
j
o
100
50
1964
1967
YEAR
1971
Figure 4-13. Regional comparisons of com-
posite average annual maximum daily sulfur
dioxide concentrations at urban NASN stations.
Table 4-11. REGIONAL SUMMARY OF TRENDS IN ANNUAL ARITHMETIC MEAN
SULFUR DIOXIDE CONCENTRATIONS AT URBAN NASN STATIONS, 1964-1971
Regions
North Central
Northeast
South
West
Total stations
Number of stations
8 years, 1964-1971
Up
1
1
No
change
4
1
3
3
11
Down
7
8
4
1
20
Low
Total
12
9
7
4
32
Last 4 years, 1968-1971
Up
2
1
3
No
change
6
7
3
1
17
Down
17
14
7
4
42
Low
4
3
16
10
33
Total
27
26
27
15
95
ability are determining factors. Increased fuel transportation costs favor the gen-
eration of electricity near the fuel source - e.g., mine-mouth operations in Penn-
sylvania. Finally, emissions generated at ground level, such as from area sources,
have a much larger impact on local ambient air quality than the same emissions from
an elevated point source.
4-19
-------
Although particulate matter concentrations, like S02, have shown a decrease
since the early 1960's, the percent reduction has not been as dramatic. A conflict
also arises with TSP because, again, nationwide emissions have shown a slight increase
(about 10 percent) since 1960. The reasons for this apparent conflict are the same.
The use of cleaner fuels for home heating and for office buildings would have signif-
icant impact on center city monitors, but a small impact on total nationwide emis-
sions. The increasing controls used on stationary sources such as power plants and
industries, coupled with relocation, would also contribute to the decreasing air con-
centrations .
The percentage of improvement for TSP concentrations has not been as great as
for SC>2, partly because of the presence of background or noncontrollable "emissions."
Background concentrations of S02 are essentially zero for urban areas, whereas wind-
blown dust and pollen result in particulate concentrations for which emission control
plans will have no impact. For this reason, particulate emission reductions are not
as effective in terms of percentage of air quality improvement as are similar reduc-
tions in SC>2 emissions.
4.2.2 CAMP Trends
The air quality data from the Continuous Air Monitoring Program present an oppor-
tunity for examining temporal changes in concentrations of various gaseous pollutants.
This section analyzes both inter-station and inter-pollutant trends for NOX, CO, and
oxidants.
CAMP, the Federal government's major effort in providing continuous concurrent
data for various gaseous air pollutants, was initiated in 1962 and is now administered
by the Quality Assurance and Environmental Monitoring Laboratory of the Environmental
Protection Agency. This laboratory provides necessary technical support and serves
as the central group for data handling, reduction, and analysis. It is also the en-
tity for reporting the operation. The stations are operated cooperatively with city
air pollution control agencies that provide the station sites and, sometimes, the
station operators. CAMP provides information on short-term (5-minute) concentrations
of gaseous pollutants. This sampling frequency makes it possible to monitor rapid
changes in source strength, meteorology, and accompanying atmospheric reactions, thus
facilitating study of these variables.
The pollutants monitored at each CAMP station are identified in Table 4-12 to-
gether with the measurement techniques utilized. Identical methods for pollutant con-
centration measurements and calibration procedures are in use at all stations.
Table 4-12. POLLUTANTS MEASURED AND CURRENT
MONITORING METHODS USED AT CAMP STATIONS
Pollutant
Carbon monoxide
Nitric oxide
Nitrogen dioxide
Sulfur dioxide
Total hydrocarbons
Methane
Sampling method
Nondispersive infrared
Saltzman colorimetric
Saltzman colorimetric
Parasosaniline colorimetric
Flame ionization detection
Flame ionization detection
Total oxidants j Neutral buffered potassium iodide
CAMP stations are located in Chicago, Cincinnati, Denver, Philadelphia, St. Louis
and Washington, D.C. New Orleans, Los Angeles, and San Francisco were previously in-
cluded in the CAMP network. The stations in Chicago, Cincinnati, Philadelphia, and
4-20
-------
Washington, D.C. have been a part of the program since its inception. The Washington,
B.C. station was moved to a new location in 1969, temporarily interrupting the data
record process. The CAMP station locations were chosen, to the degree practicable,
for similarity from city to city. The stations in every case are located in the down-
town, central-business district, removed from the direct influence of any nearby large
point source. Other station characteristics (e.g., height of sampling probe) are
standardized to facilitate inter-city comparisons. It is emphasized, however, that
since a CAMP station constitutes only one sampling site per city, its data do not
necessarily represent air quality levels prevailing beyond the immediate vicinity of
the station.
Because the samples collected at CAMP stations represent, in a number of urban
areas, the only data available for air quality trend analysis for gaseous pollutants,
the development of national trends is not possible. In addition, data continuity is
often lacking. This is particularly true of the total-oxidant data. Many data dis-
continuities result from changes of site location or procedural methods.
The relocation of the Washington, D.C. station in 1969 makes a discussion of
trends impossible there since there is no way of estimating the impact of this move
on the recorded air quality levels. In 1968, the S02 analysis method at all stations
was changed from the conductometric method to the colorimetric pararosaniline method
(West-Gaeke). Because of this change, trends in S02 will not be considered. Sub-
sequent to the S02 method change, the original CO instruments (mono-beam-NDIR) were
replaced with dual-beam-NDIR detectors. These and other important changes and their
possible effects are listed in Table 4-13.
Table 4-13. MONITORING METHOD AND PROCEDURAL CHANGES AT CAMP STATIONS
Year of
change
Type of change
Possible effects
1968
1969
1969
1970
1970
1971
Change in S02 instrumentation
Change in data retrieval system
Installed blower on intake
manifold to increase airflow
Change in CO instrumentation.
Change from helium to N2 for
CO zero gas
Installation of integrating
chambers for CO
Change from N2 to air for CO
calibration gases
Data discontinuity
Two quarters of data lost
for some pollutants
Reduces sample time, possibly
affecting NOX and Ox
Eliminate H20 vapor
interference
Smooths out concentration
plots
Eliminate C02 interference
Even though limitations and problems have been experienced, the CAMP data still
represent the only long-term continuous data base for use in determining trends in
faseous pollutants for major American cities. Clearly, caution must be exercised be-
ore any definite conclusions are reached in the analysis of these data.
4.2.2.1 Trend analysis by pollutant - Trend analysis for CAMP data presented below
is for carbon monoxide, nitric oxide, nitrogen dioxide, total oxides of nitrogen
(NO and N02), and total oxidants. For purposes of comparison, the data are grouped
into two time intervals: 1962 through 1966 and 1967 through 1971. The data analyzed
for these two time intervals reflect: (1) the amount of information available for the
year and, (2) more importantly, the distribution of the data within the -ear, For
4-21
-------
example, the data for total oxidants were used in the analysis only when the third
quarter (July, August, and September) for the year was sufficiently represented. Be-
cause CO follows a generally uniform pattern throughout the year, the distribution of
these data was less critical than that of total oxidants, NO, and NC>2. Using this
approach, the following data were excluded from the analysis:
Chicago
Cincinnati
Denver
Philadelphia
St. Louis
Pollutant
Total oxidant
NO and N02
Total oxidants
NO and NO2
Total oxidants
Total oxidants
Total oxidants
Year(s)
1969
1970
1966, 1969, and 1970
1971
1967, 1909, 1970, and 1971
1969
1968, 1969, and 1970
Data for carbon monoxide, NO, and N02 were compared for the time periods 1962
through 1966 and 1967 through 1971. This division approximately halves the data rec-
ords for Chicago, Cincinnati, and Philadelphia because data acquisition at^these
stations began in 1962. Data collecting at Denver and St. Louis began in 1965 and
1964, respectively; therefore, the period 1967 through 1971 for these cities will in-
clude more data than the period 1962 through 1966. The average concentrations were
computed for the two periods, together with the averages of the annual second highest
values. The averages for the respective periods provide an indication of the long-
term trend component. On the other hand, the averages of the second highest 1-hour
values were used as estimators of changes in extreme values.
Tables 4-14 through 4-18 present the results of this analysis.
is discussed separately.
Each pollutant
Table 4-14. CARBON MONOXIDE CONCENTRATIONS MEASURED AT CAMP STATIONS BY NDIR METHOD
("ig/m3)
Station
Chicago
Cincinnati
Denver
Philadelphia
St. Louis
CAMP average
Annual average concentration
1962-1966
14.6
6.0
8.8
8.3
7.1
9.0
1967-1971
7.8
4.6
7.2
5.7
5.6
6.2
Percent
change
-46
-23
-18
-31
-21
-31
Average of annual 2nd highest
value
1962-1966
47
26
58
45
29
41
1967-1971
41
27
57
33
29
38
Percent
change
-13
+4
-2
-27
0
-7
4.2.2.1.1 Carbon monoxide - All five stations in Table 4-14 showed a decrease in an-
nual average CO concentrations for the two periods. This percentage decrease ranges
from 18 percent for Denver to 46 percent for Chicago. The percent decrease for the
average of the five stations is 31 percent. Graphs of the CO annual average concen-
trations (to be presented later) show a consistent decrease in concentrations through-
out the entire data period for most stations. Cincinnati showed a modest increase
in the average of the second highest values while Philadelphia showed the largest de-
crease (27 percent). Average concentrations^of CO appear to be decreasing at all the
CAMP stations, although a similar chctnge in the second highest value was not observed
at any station with the possible exceptions of Philadelphia and Chicago. The earlier
4-22
-------
Table 4-15. NITRIC OXIDE CONCENTRATIONS MEASURED AT CAMP STATIONS BY MODIFIED
SALTZMAN COLORIMETRIC METHOD
(yg/m3)
Station
Chicago
Cincinnati
Denver
Philadelphia
St. Louis
CAMP average
Average concentration
1962-1966
122.6
43.8
44.9
55.2
39.8
61.2
1967-1971
125.4
53.6
54.4
65.4
47.6
69.3
Percent
change
+ 2
+22
+21
+18
+19
+13
Average of annual 2nd highest
value
1962-1966
731
782
633
1331
541
804
1967-1971
969
1067
620
1395
578
926
Percent
change
+32
+36
- 2
+ 5
+ 7
+15
Table 4-16.
NITROGEN DIOXIDE CONCENTRATIONS MEASURED AT CAMP STATIONS BY
MODIFIED SALTZMAN COLORIMETRIC METHOD
(ug/m3)
Station
Chicago
Cincinnati
Denver
Philadelphia
St. Louis
CAMP average
Average concentration
1962-1966
86.1
62.0
66.0
67.7
58.5
68.1
1967-1971 '
101.2
60.0
67.9
77.6
54.2
72.2
Percent
change
+18
-3
+3
+15
-7
+6
Average of annual 2nd highest
value
1962-1966
444
391
498
361
320
403
1967-1971
499
367
493
414
267
408
Percent
change
+12
-6
-1
+15
-16
+1
Table 4-17. OXIDES OF NITROGEN (NO + N02) CONCENTRATIONS
MEASURED AT CAMP STATIONS
(yg/m3)
Station
Chicago
Cincinnati
Denver
Philadelphia
St. Louis
CAMP average
Average concentration
1962-1966
208.7 1
105.8
110.9
122.9
98.3
129.3
1967-1971
226.6
113.6
122.3
143.0
101.8
141.5
Percent
change
+ 8
+ 7
+10
+16
+ 3
+ 9
4-23
-------
Table 4-18. TOTAL OXIDANT CONCENTRATIONS MEASURED AT CAMP STATIONS
BY NEUTRAL BUFFERED KI METHOD
(ug/m3)
Station
Chicago
Cincinnati
Denver
Philadelphia
St. Louis
CAMP average
Average of
99th percenti le
1962-1966
128.2
191.9
-
211.5
-
177.2
1967-1971
166.2
176.9
-
169.6
-
171
Percent
change
+30
- 8
-
-20
-
- 3
Average of
annual 2nd highest value
1962-1966
263
333
-
459
-
352
1967-1971
299
287
-
299
-
295
Percent
change
+14
-14
-
-35
-
-16
change in CO instrumentation and operating procedures (1970) has probably exaggerated
this pattern of decreasing concentration. The overall effect is, therefore, difficult
to quantify with precision.
4.2.2.1.2 Nitric oxide - Nitric oxide concentration trends follow a pattern oppo-
site from that of CO (Table 4-15). The average (1967 through 1971) annual concentra-
tion is higher for each station; however, the increase in Chicago is slight (2 per-
cent). The percent increase in the five-station average is 13 percent. The increases
are larger for the averages of the annual second highest values for Chicago, 32 per-
cent, and Cincinnati, 36 percent. The other stations showed only very slight changes
between the two periods.
4.2.2.1.3 Nitrogen dioxide - The Chicago CAMP station (Table 4-16) showed the largest
increase (18 percent) in average concentrations. Philadelphia showed increases of 15
percent for both averages. Cincinnati, Denver, and St. Louis showed only very slight
changes. The composite N02 average for the five stations showed only a 6 percent in-
crease in the average annual concentration and essentially no change (1 percent) in
the second highest value average. These results indicate that N02 concentrations did
not parallel the increases noted for NO. This could have been caused by restraints
that limit the atmospheric conversion of NO to N0£. Such restraints could be the
amount of incident ultra-violet solar energy or the amount of reactive hydrocarbons
present.
4.2.2.1.4 Oxides of nitrogen - Most cities showed modest increases in the average
NOX (NO and N02) concentrations (Table 4-17). The composite average increase for the
five stations was 9 percent.
4.2.2.1.5 total oxidants - The total-oxicfant data are of limited value because they
are incomplete (Table 4-18). Only Chicago, Cincinnati, and Philadelphia had suffi-
cient data for analysis. Instead of the average concentrations, the weighted
averages (by the number of observations) of the annual 99th percentile concentrations
were computed together with the averages of the second highest values. The Chicago
station showed the highest increase (30 percent) in the average of the 99th percen
tiles, whereas Philadelphia had the largest decrease (20"percent). Cincinnati
showed only a modest decrease (8 percent) in the average 99th percentile. The limi-
tations in these data make it impossible to reach a meaningful conclusion concerning
trends in urban oxidant measurements.
4.2.2.2 Trend analysis by city - In addition to the analyses presented above, CAMP
annual averages for NO, N02, NOX, and CO are presented by city in Figures 4-14 through
4-17. Circled annual averages were derived from data that do not satisfy the National
4-24
-------
o INDICATES INVALID AVERAGE (AVERAGE BASED ON INCOMPLETE DATA)
20
10
10
10
•x.
o
o
10
10
CINCINNATI CAMP
DENVER CAMP
o
PHILADELPHIA CAMP
ST. LOUIS CAMP
1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972
YEAR
Figure 4-14. Trend lines for CO annual averages in five CAMP cities.
Aerometric Data Bank's minimum sampling criterion, which requires at least 75 percent
representation of all possible 1-hour samples in the year. To aid in the interpreta-
tion of these time plots, a simple linear regression analysis is provided in which
the annual average is displayed as a function of time for each station-pollutant com-
bination. The calculated least-squares regression lines are also shown superimposed
over the time plots of the annual averages.
The NO, N02, and NOx graphs and regression lines indicate, for the most part, an
increase in annual average concentration with time. The NO results show this pattern
more consistently from city to city than either NC>2 or NOx. The regression lines
for Philadelphia NO concentrations were computed with and without the 1962 average in-
cluded because it appeared to be unusually lower than subsequent averages. With 1962
omitted, the regression line has essentially zero slope, indicating no discernible
change in annual average concentration with time. Both the N02 and NOX data for Den-
ver and St. Louis also appear to have varied little over the time span considered.
The CO annual averages for all CAMP stations show substantial decreases with time.
The slopes of the regression lines (which can be interpreted as the average rates of
change in the annual average concentrations) range from -0.26 in Denver to -1.01 in
Chicago. The regressions for CO appear to fit the individual annual averages well,
indicating that the change in annual average CO concentrations with time is approxi-
4-25
-------
200
100
o INDICATES INVALID AVERAGE (AVERAGE BASED ON INCOMPLETE DATA)
* NOTE CHANGE IN ORDINATE SCALE FOR THESE DATA.
CHICAGO-
CAMP
0
100
50
0
100
SJ
C9
I
I I I i I
SO
0
100
50
DENVER'
CAMP
62 OMITTED
0
100
50
0
T I I I I
o o -
PHILADELPHIA
, | CAMP
L I I
ST. LOUIS'
CAMP
1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
YEAR
Figure 4-15. Trend lines for NO annual averages in five CAMP cities.
mately linear. Denver is the only station whose averages for the period 1969 through
1971 showed an increase from 6.5 mg/m3 (1969) to 8.3 mg/m3 (1971). The individual
regressions were all tested for statistical significance at the a =0.05 level. Table
4-19 shows a listing of the significant regressions together with the average percent
rate of change per year. The interpretation of trends in the CO d..: ,. is mentioned
before, must be conducted with a great deal of caution because of the change in in-
strumentation and the limited information available for recent years. The change in
instruments and procedures that occurred in the period 1969 through 1970 at all sta-
tions is believed to cause lower measured CO concentrations since the interference
of water vapor was presumably minimized.
Because standards for CO are written in terms of 8-hour and 1-hour averages,
it is more informative to observe the change with time of a parameter based on its
averaging time rather than on annual averages. The effect of the instrumentation
changes on the extreme values or the upper percentiles for these short-term averaging
times is not as great on a percentage basis as is true for the annual averages. The
annual 99th percentiles for hourly CO measurements are shown in Figure 4-18. In
most cases, this value has decreased over time. Again, Denver is the exception. De-
creases in the 99th percentile over the entire period ranged from about 17 percent
4-26
-------
200
100
0
100
50
o INDICATES INVALID AVERAGE (AVERAGE BASED ON INCOMPLETE DATA)
* NOTE CHANGE IN ORDINATE SCALE FOR THESE DATA.
a" o
S 100
50
•t
&
0
100
50
0
100
50
CHICAGO •
CAMP
I I I I 1
CINCINNATI
CAMP
T i
ri -. Q
DENVER
CAMP
PHILADELPHIA'
CAMP
ST. LOUIS
CAMP
1962 1963 1964 1965 196G 1967 1968 1969 1970 1971
YEAR
Figure 4-16. Trend lines for N02 annual averages in five CAMP cities.
(in St. Louis) to about 55 percent (in Philadelphia). The pattern in Denver was
fairly stable with the value for 1971 showing the largest change of about 22 percent
above the 1970 value.
The annual 99th percentiles for total oxidants are presented in Figure 4-19.
Only in the cases of Chicago and Philadelphia are sufficient data available to permit
the detection of possible trends. Chicago averaged 50 to 75 ug/m3 in 1962 and 1963.
This level increased to approximately 200 jig/m3 in 1964 and showed little change there-
after. The very low concentrations in the beginning may reflect the reducing effect
of S02 on oxidants. This effect was corrected in 1964 by the installation of an SO?
scrubber to the system. The Philadelphia plot reaches a maximum of almost 300 ;ig/m*
in 1966 and declines to a minimum of 118jug/m3 in 1971. The 1971 99th percentile for
St. Louis is the lowest of any annual value presented for this station. Although
Cincinnati lacks 3 years of data (1966, 1969, and 1970), the data that are available
indicate a stable situation.
4.3 TREND ANALYSES OF SELECTED AQCR'S
The previous section discussed air quality trends on a nationwide basis for TSP
and S02, while it examined the automobile-related pollutants in six cities at CAMP
4-27
-------
UJ
s
cc
UJ
X
O
400
200
0
200
100
0
200
100
0
200
100
o INDICATES INVALID AVERAGE (AVERAGE BASED ON INCOMPLETE DATA)
* NOTE CHANGE IN ORDINATE SCALE FOR THESE DATA
CHICAGO.
CAMP
0
200
100
CINCINNATI
CAMP
DENVER"
CAMP
PHILADELPHIA
0 CAMP
ST. LOUIS -
CAMP
1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
YEAR
Figure 4-17. Trend lines for NOX annual averages in five CAMP cities.
sites. The; yearly annual means and trend summaries for the NASN stations employed in
this analysis are indicated in Appendix F for each AQCR. Since this NASN Trend infor-
mation is frequently based on only one monitoring site in an AQCR, it can be mislead-
ing to assess the progress of an entire AQCR solely on this basis. This section illus-
trates this point by examining three specific AQCR-pollutant combinations in more de-
tail. By supplementing the NASN data with data from State and local agency monitoring
efforts, it is possible to obtain a more complete assessment of the various trends
within an AQCR. 'ne three cases treated are (1) oxidants in Los Angeles, (2) sus-
pended particulates in New Jersey-New York-Connecticut, and (3) sulfur dioxide in
Chicago. The Regions were selected because they had the most air monitoring sites
for each of the three pollutants, and they were Priority I Regions for the given
pollutant, indicating that the concentration of that pollutant in the Region is of
particular concern with respect to the air quality standards.
The AQCR analyses utilize both statistical tests (with the exception of Los
Angeles) and graphical presentations. All annual trends for individual sites were
determined by statistical tests based on contrasts of annual geometric means among
various years. In addition, graphs are presented for annual means showing trends at
selected sites, the behavior of composite averages, and the history of the maximum
4-28
-------
Table 4-19. CITY-POLLUTANT COMBINATIONS FROM CAMP STATIONS WHERE STATISTICALLY
SIGNIFICANT (6 = 0.05 LEVEL) LINEAR CHANGES IN ANNUAL AVERAGE
POLLUTANT CONCENTRATION WITH TIME WERE FOUND
City
Chicago
Chicago
Cincinnati
Cincinnati
Denver
Denver
Philadelphia
St. Louis
Pollutant
CO
N02
CO
NOX
NO
NOX
CO
CO
Pattern of
change
Decreasing
Increasing
Decreasing
Increasing
Increasing
Increasing
Decreasing
Decreasing
Rate of
change/yr
-1 .01 mg/m3
+3.82 ug/m3
-0.62 mg/m3
+2.95 yg/m3
+3.83 pg/m3
+4.01 pg/m3
-0.84 mg/m3
-0.36 mg/m3
Percent rate of
change/yr
-10
+4
-14
+3
-•7
+3
-15
-6
o INDICATES INVALID AVERAGE (AVERAGE BASED ON INCOMPLETE DATA)
40
20
CHICAGO
CAMP .
tu
2(1
o
W~
20
n
40
'n
n
20
0
CINCI
4NATI
o- o^^ nAMP
• -<
\
c
> <
>- [
^
1
DE
C
NVER
AMP
1
— o^_ ^^V PHILADELPHIA
^~~— ^ r. -"^^ N. CAMP
X-, n -"
|
c
D '
3— — (•
3 °" -(
1
ST.
W
5
.OUIS
IMP
o
C£.
tf
1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
YEAR
Figure 4-18. Trend lines for annual 99th percentiles of CO in five CAMP cities.
4-29
-------
o INDICATES INVALID AVERAGE (AVERAGE BASED ON INCOMPLETE DATA)
200
0
400
3
=! 200
3
o
tc
UJ
a. o
K 400
Si
_i
| 200
<
— 4UU
0
_i
fe 200
0
400
200
n
_^J
M
r
1
***
- — -f
CH!
W
1
CAGO
IMP -
1
c
>- — <
^
t
1-^c
1
C
^ C
)
CIHCII
o ™
INATI
IP -
c
) C
J
c
)
DE
C
NVER
AMP -
c
* «
^
*-— <
^
k
^-s
3
(
F
^
'HILADE
CAM
f
LPHIA
P —
—
c
3 1
3 <
) <
}
t
ST.
c;
[
.GUIS
IMP -
1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
YEAR
Figure 4-19. Trend lines for annual 99th percentiles of total oxidants in five CAMP cities.
yearly values for the annual means, either in the entire AQCR or in the largest"city
within the AQCR. The graph of a selected site illustrates the variability associated
with ambient air quality measurements, whereas the graph of the composite average
summarizes the general trend of all the sites. In forming the composite averagesj
interpolated values were used for missing values to form a consistent data set for
these sites throughout the period of interest. The maximum annual average values in
an AQCR were plotted to compare these values to the applicable annual air quality
standards.
In addition to this treatment of annual values, similar graphical presentations
are provided for various 99th percentile values of 24-hour or hourly measurements.
These quantities reflect the historical pattern of the AQCR with respect to short-
term air quality standards. In the case of sulfur dioxide and total suspended partic-
ulates, 99th percentile values for 24-hour measurements were used to examine the
trends in the AQCR with respect to the 24-hour quality standards. These results were
then compared with the trends determined for the annual means. For oxidants, the dis-
cussion of trends is limited by available data and is based solely on changes in the
99th percentile values of hourly measurements. These values are compared to the max-
imum hourly oxidant standard and no statistical tests for trends are made. The 99th
percentile value was used, rather than the maximum or second highest value, to allow
for the different number of observations made at various sites.
4-30
-------
In discussing air quality trends within individual AQCR's, it should be noted
that the placement of monitoring sites within a Region is not necessarily intended
to reflect average values throughout the AQCR. For example, one Region may concen-
trate its monitoring sites in high-pollution areas, whereas another may choose a more
uniform distribution of sites. For this reason, caution should be exercised in making
comparisons among Regions based on composite averages. This report is concerned pri-
marily with trends, and these trends should be viewed as applicable to the site rather
than to the AQCR as a whole in most instances.
The approach used in this analysis is primarily descriptive. In this report, the
emphasis has been placed on determining historical trends in air quality data rather
than seeking causal interpretations as to why these trends have occurred. For each
AQCR, the trend in ambient air quality levels is affected by factors such as emission
regulations and meteorological conditions, which are not discussed in depth in this
treatment.
In examining these AQCR's, it should be noted that only those sites having at
least 2 years of valid data during the period 1968 through 1971, one of which was
after 1969, are used in the analysis of trends in annual values.
The trends in annual means for the New Jersey-New York-Connecticut and the Metro-
politan Chicago AQCR's are down for the long term and mixed for the short term. The
Los Angeles AQCR has shown declines in 99th percentile values for total oxidant.
Discussions of the results for the Los Angeles AQCR, the New Jersey-New York-
Connecticut AQCR, and the Chicago AQCR follow.
4.3.1 Metropolitan Los Angeles Intrastate AQCR
4.3.1.1 Regional description - The Metropolitan Los Angeles Intrastate AOCR has an
area of 23,800 square kilometers (9200 square miles) and a population of 9.8 million.
The areas included in this Region are shown in Figure 4-20. A series of mountain
ranges forms a semicurcular barrier around the Los Angeles Basin area. This Basin
includes a small coastal strip extending northwest into Santa Barbara County. The
A INDICATES NUMBER OF SITES IN COUNTY.
• INDICATES NUMBER OF SITES WITHIN CITY OF LOS ANGELES.
TOTAL STATIONS: 16
Figure 4-20. Metropolitan Los Angeles Intrastate AQCR.
4-31
-------
mountain barrier and low-mixing depths associated with the semipermanent Pacific anti-
cyclone constitute an effective barrier that limits horizontal and vertical ventila-
tion of pollutants generated within the Basin. Particularly in the summer, frequent
clear skies with light westerly daytime winds, together with the existing mountain
barrier and the large number of automobiles, contribute greatly to the serious photo-
chemical smog problem in the Basin.
4.3.1.2 Oxidant trends - The 99th percentile values for hourly total oxidant values
in the Los Angeles AQCR have shown a short-term decline, but the region continues to
exceed the maximum hourly oxidant standard. This discussion compares the 99th per-
centile values at various stations with the hourly standard.* Twelve sites in the
National Aerometric Data Bank having at least 2 years of data during the period 1968
through 1971, one of which was after 1969, were used in this analysis. The geograph-
ical distribution of these sites is indicated in Figure 4-20. Annual percentile val-
ues for these sites are listed in Table 4-20 for the years 1963 through 1971. Figure
Table 4-20. 99th PERCENTILE VALUES FOR HOURLY OXIDANT CONCENTRATIONS
IN METROPOLITAN LOS ANGELES INTRASTATE AOCR
(ug/m3)
City
Anaheim
Azusa
Burbank
La Habra
Lennox
Long Beach
Los Angeles
Los Angeles
Los Angeles
Pomona
San Bernardino
Santa Ana
1963
333
470
353
196
372
372
392
1964
294
588
392
216
412
314
470
1965
470
608
490
274
255
451
353
450
1966
412
588
412
235
235
412
333
450
529
431
1967
392
647
568
255
196
392
353
529
568
451
1968
333
294
412
196
1969
353
1970
294
627
431
274
196
137
313
255
412
529
529
216
1971
235
510
392
392
176
157
274
216
353
392
451
274
4-21 displays the maximum 99th percentile values in the AQCR and also the composite
averages of these 99th percentile values. The absence of maximum values for the
years 1968 and 1969 can be attributed to the fact that data are available from NADB
for only four sites for 1968 and one site for 1969. Values for sites that show
consistently higher oxidant levels are not available for this period. The graph of
the composite average in Figure 4-21 illustrates both the recent decline in oxidant
values and the degree by which the Region exceeds the hourly oxidant standard. De-
spite this decline in the composite average, there has been no significant change in
the percentage of sites exceeding the oxidant standard for the period 1971 through
1972.
*99th percentile values, although not those used in the definition of the NAAOS's,
approximate the standard definition in that they comprise the 87 largest values out
of a possible 8760 observations for a year.
4-32
-------
700
600
500
;400
300
200
100
MAXIMUM AQCR VALUE
NOTE: ONLY 4 SITES IN 1968\
AND 1 SITE IN 1969
""^-•"'
** A
AQCR COMPOSITE AVERAGE
(12 SITES)
HOURLY OXIDANT STANDARD
1963
1967
YEAR
1971
Figure 4-21. 99th percentile values of hourly
oxidant concentratior s for the Los Angeles
Intrastate AQCR.
4.3.2 New Jersey-New York-Connecticut Interstate AQCR
4.3.2.1 Regional description - The New Jersey-New York-Connecticut Interstate AQCR
includes New York City and surrounding areas in the three -state Region as shown in
Figure 4-22. This Region has a population of 17.3 million and covers an area of
14,560 square kilometers (5,634 square miles). The terrain is generally level except
for some hilly areas along the northwest boundary. This terrain and the combination
of sea breezes reinforced by the heat-island effect of New York Citv contribute to a
high average wind speed that provides favorable horizontal dispersion as compared to
most locations in the Eastern United States.
4.3.2.2 Particulate trends - Forty-two monitoring stations provided the data used in
this analysis. Seven of these stations were NASN sites and the balance were State
agency sites. The New Jersey-New York -Connecticut AQCR showed an overall long-term
downward trend in annual TSP values for the past 12- and 8-year periods. Over the
past 4 years, the short-term pattern has been mixed, with the majority of these sites
showing no change. These results are summarized in Table 4-21.
Figure 4-23 displays the annual TSP geometric means for NASN sites at Newark,
New Jersey and New York City^ _Both locations show long-term downward trends with no
clearcut recent short-term trend. The composite average for all sites considered shows
a slight downward trend from 77 ^ig/rn^ to 72 >ig/m3 over the past 4 years. As presented
in Table 4-22, only one site showed a long-term upward trend. This increase occurred
in Suffolk County over the past 8 years and was attributed primarily to high values in
the past 4-year period. Although initially below the standard, TSP values at this site
rose above the primary standard in 1970.
Figure 4-24 displays 99th percentile TSP values relative to the 24-hour standards.
Although both the Newark and New York City NASN sites showed an overall downward pat-
4-33
-------
BRONX
NEW YORK
HUDSON
KINGS
RICHMOND
TOTAL PARTICIPATE MONITORS: 42
Figure 4-22. New Jersey-New York-Connecticut Interstate AQCR.
tern, it is also clear that the 99th percentile values of the second highest station
in the AQCR are increasing and are well above the 24-hour primary standard. Because
of the large number of sites in this AQCR, and extremely high values at a site for a
particular year, the second highest value was plotted rather than the maximum. Tables
4-23 and 4-24 summarize the status of these stations over the past 4 years with re-
spect to the standards. As would be expected from the mixed trends in the past 4
years, there has been no consistent improvement.
4.3.3 Metropolitan Chicago Interstate AQCR
4.3.3.1 Regional description - The Metropolitan Chicago AQCR includes the City of
Chicago and surrounding portions of Illinois and Indiana, as shown in Figure 4-25.
This Region has a population of 7.1 million and an area of 13,330 square kilometers
(5,149 square miles). The generally flat terrain of the Region allows free air
movement. Lake breezes and a favored storm-track position provide the strong vari-
able winds characteristic of the area. These favorable topographical and meteorolog-
ical features minimize the occurrence of stagnant air masses.
4.3.3.2 Sulfur dioxide trends- - The Chicago AQCR has shown a marked downward trend
in sulfur dioxide levels during the last 8-year period. All sites in the Region with
sufficient data showed long-term downward trends. There were 22 sites used for this
analysis. The trends at each site are shown in Table 4-25. Twenty of these sites
are located in the City of Chicago; the other two are NASN stations located in East
Chicago, Indiana and Hammond, Indiana.
The East Chicago site showed a downward trend over the past 8 years. Both Indi-
ana NASN sites showed downward short-term trends. As presented in Table 4-26, the
Chicago sites showed a mixed short-term pattern. This was attributed primarily to
relative increases in 1970 annual geometric means. The annual arithmetic means for
all the 18 stations reporting for 1972 remained below the annual secondary standard.
4-34
-------
Table 4-21. NUMBER OF STATIONS SHOWING TRENDS IN ANNUAL MEAN
TSP CONCENTRATIONS IN NEW JERSEY-NEW YORK-CONNECTICUT AQCR
Trend
UP
Down
No change
Total
Number of stations
1960-1971
5
2
7
1960-1967
6
6
1964-1971
1
11
10
22
1968-1971
4
9
29
42
200
180
160
140
*120
100
I I I I I
NEW YORK CITY SITE
AQCR COMPOSITE
AVERAGE (42 SITES)
\NEWARKNASNSITE-
\
ANNUAL PRIMARY STANDARD
3> ^-..
"*^"- -...i> /
rr Tun A air? ~ ir^ N
40
I960
ANNUAL SECONDARY STANDARD
I I I I I I I I I
19(5
YEAR
1971
Figure 4-23. TSP annual geometric means
for selected stations in the New Jersey-New
York-Connecticut Interstate AQCR.
Fourteen of these 18 stations reported lower levels for 1972 than for 1971, and 12
reported their all-time lowest annual levels. Of the nine sites showing upward short-
term trends in the period 1968 through 1971. Eight have reported data for 1972, and
seven of these reported all-time lows. This indicates tnat, despite the mixed short-
term pattern in the period 1968 through 1971, the long-term downward trend is still
continuing.
Although these trend determinations were based on annual geometric means, Figure
4-26 shows that the annual arithmetic means also support the downward pattern. Both
the Chicago City composite and the Chicago NASN site showed downward trends and, by
1971, the maximum AQCR annual mean was below the annual primary standard. This down-
ward trend is also apparent in Figure 4-27 for the 99th percentile values. Again, the
Chicago City composite and the Chicago NASN site showed downward trends and, by 1971,
4-35
-------
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4-36
-------
500
400
^300
a.
200 —
100
2ND HIGH AQCR VALUE/
24-HOUR
PRIMARY
STANDARD
NEWARK NASN SITE V
24-HOUR SECONDARY STANDARD
I I I
1960
1965
YEAR
1971
Figure 4-24. Annual TSP 99th percent!le for
selected NASN stations in the New Jersey-
New York-Connecticut Interstate AQCR.
Table 4-23. PERCENT OF STATIONS EXCEEDING ANNUAL TSP
STANDARDS IN NEW JERSEY-NEW YORK-CONNECTICUT AQCR
Year
1968
1969
1970
1971
Exceeding
primary standard
44
37
52
36
Exceeding
secondary standard
61
67
72
69
Table 4-24. PERCENT OF STATIONS WITH 99th PERCENTILE
VALUES EXCEEDING 24-hour TSP STANDARDS
IN NEW JERSEY-NEW YORK-CONNECTICUT AQCR
Year
1968
1969
1970
1971
Exceeding
primary standard
17
18
20
14
Exceeding
secondary standard
67
67
88
67
, 4-37
-------
McHENRY
OA
KANE
OA
KENDALL
OA
GRUNDY
OA
LAKE
OA
COOK
20A
DU PAGE
OA
CHICAGO1
v, 20
WILL
OA
KANKAKEE
OA
LAKE
2A
PORTER
OA
A INDICATES NUMBER OF SULFUR DIOXIDE SITES WITHIN THE COUNTY.
• INDICATES NUMBER OF SULFUR DIOXIDE SITES WITHIN CITY OF CHICAGO.
TOTAL S02 STATIONS: 22
Figure 4-25. Metropolitan Chicago AQCR.
the maximum AQCR value met the 24-hour primary standard for sulfur dioxide. Tables
4-27 and 4-28 further demonstrate the improvement of this Region with respect to the
24-hour and annual sulfur dioxide standards. Not only were these primary standards
achieved by all sites in 1971, but there was also definite and consistent improve-
ment with respect to the secondary standards.
4-38
-------
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4-39
-------
Table 4-26. NUMBER OF STATIONS SHOWING TRENDS IN S02
ANNUAL MEANS IN METROPOLITAN CHICAGO AQCR
Trend
Up
Down
No change
Indeterminant
Total
Time period
1964-1971
0
19
0
0
19
1968-1971
9
11
1
1
22
300
250
o
t-
UJ
S
atf IV
O
CD
ZOS
0
to
1
I I
CHICAGO CITY MAXIMUM
CHICAGO NASN SITE
CHICAGO CITY COMPOSITE
(20 SITES)
ANNUAL PRIMARY \
STANDARD-v \
ANNUAL '
SECONDARY STANDARD
1968
YEAR
1971
1000
800 —
i=600 —
o
ac
UJ
o.
0400 —
200
A I I I
24-HOUR
PRIMARY -x
STANDARD >
24-HOUR
SECONDARY-.
STANDARD >
CHICAGO AQCR 2ND HIGHEST VALUE
CHICAGO NASN SITE
CHICAGO CITY COMPOSITE
AVERAGE
1965
1968
YEAR
1971
Figure 4-27. 99th percent!le values for SO2
in the metropolitan Chicago AQCR.
Figure 4-26. Annual arithmetic means for
S02 m the metropolitan Chicago AQCR.
4-40
-------
Table 4-27. PERCENT OF STATIONS EXCEEDING ANNUAL
SULFUR DIOXIDE STANDARDS IN METROPOLITAN CHICAGO AOCR
Year
1968
1969
1970
1971
Exceeding
primary standard
40
33
37
0
Exceeding
secondary standard
65
67
50
20
Table 4-28. PERCENT OF STATIONS WITH 99th PERCENTILE
VALUES EXCEEDING 24-hour SULFUR DIOXIDE STANDARDS
IN METROPOLITAN CHICAGO AQCR
Year
1968
1969
1970
1971
Exceeding
primary standard
60
57
41
0
Exceeding
secondary standard
85
76
55
29
4-41
-------
-------
APPENDIX A.
NATIONAL PRIMARY AND SECONDARY
AMBIENT AIR QUALITY STANDARDS
A-l
-------
NOTE
The National Ambient Air Quality Standards have been published in their entirety
in the Federal Register (Vol. 36, No. 34, April 30, 1971). The cover sheet for that'
issue is included opposite this page. Should additional copies of that issue of the
Federal Register be required, they may be obtained from the Superintendent of Docu-
ments, Washington, B.C. 20402.
A-2
-------
FEDERAL
REGISTER
VOLUME 36 • NUMBER 84
Friday, April 30, 1971 • Washington, D.C.
PART II
ENVIRONMENTAL
PROTECTION AGENCY
National Primary and Secondary
Ambient Air Quality Standards
No. 84—Pt. II 1
A-3
-------
-------
APPENDIX B.
REQUIREMENTS FOR PREPARATION, ADOPTION,
AND SUBMITTAL OF STATE IMPLEMENTATION PLANS
B-l
-------
NOTE
The Requirements for Preparation, Adoption, and Submittal of Implementation
Plans have been published in their entirety in the Federal Register (Vol. 36, No. 84,
August 14, 1971). The cover sheet for that issue is included opposite this page.
Should additional copies of that issue of the Federal Register be required, they
may be obtained from the Superintendent of Documents, Washington, B.C. 20402.
B-2