vvEPA
United States Environmental Monitoring Systems
Environmental Protection Laboratory
Agency Research Triangle Park NC 27711
EPA/600/4-86/013
Feb 1986
Research and Development
National
Performance Audit
Program—Ambient
Air Audits of
Analytical
Proficiency—1984
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EPA/600/4-86/013
NATIONAL PERFORMANCE AUDIT PROGRAM
AMBIENT AIR AUDITS OF ANALYTICAL PROFICIENCY
-1984-
by
Elaine F. Parr, Robert L. Lampe, Gregory Pratt,
Oscar L. Dowler and William J. Mitchell
Quality Assurance Division
Environmental Monitoring Systems Laboratory
Research Triangle Park, North Carolina 27711
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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NOTICE
This document has been reviewed in accordance with U.S. Environmental
Protection Agency policy and approved for publication. Mention of trade
names or commercial products does not constitute endorsement or recommenda-
tion for use.
11
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ABSTRACT
This report presents the results of the U.S. Environmental Protection
Agency's 1984 National Audit Program by pollutant and_by analytical method.
Semiannual audits were conduced for Pb, N03~ and S0^~ (filter strips) and
one audit was conducted for S(>2 (bubbler), N02 (bubbler), CO and high-volume
flow rate. Continuous S02 monitors were audited throughout the year, such
that no monitor was audited more than once. Approximately 30 laboratories
participated in each semiannual acid rain audit. Twenty laboratories par-
ticipated in the S02 bubbler audit, and 21 in the N02 audit, a 20% decrease
from 1983. Approximately 55 laboratories participated in each NOj" and S0^~
audit and approximately 100 laboratories in each Pb audit. Three hundred
and thirty CO monitors, 221 S02 monitors and 1402 high volume flow samplers
were also audited. The results for each 1984 audit are presented in tabu-
lar form for each concentration level. The overall performance for all
participants for each audit conducted since the beginning of the program is
also illustrated in a series of figures.
iii
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CONTENTS
Abstract ill
Tables vii
Figures ix
Acknowledgments . xi
1. Introduction 1
2. Summary and Conclusions 3
3. Audit Materials 4
4. Audit Results . 7
References 13
Tables 14
Figures 40
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TABLES
Number Page
1 Agency Participation ..... 14
2 Audit Results for Manual Sulfur Dioxide 15
3 Results for the Pararosaniline Method 16
4 Percent of Sulfur Dioxide Measurements Within
Indicated Percent of Assigned Values (Statistical
Outliers Removed) 17
5 Audit Results for Nitrogen Dioxide 17
6 Audit Results for Nitrogen Dioxide by the Sodium
Arsenite Method 18
7 Percentage of Nitrogen Dioxide Measurements Within
Indicated Percentage of Assigned Value (Statistical
Outliers Removed) 19
8 Audit Results for Carbon Monoxide 19
9 Audit Results for Carbon Monoxide by the NDIR Method ... 20
10 Percentage of Carbon Monoxide Measurements Within
Indicated Percentage of Assigned Value (Statistical
Outliers Removed) 20
11 Audit Results for Sulfate on Filter Strips ........ 21
12 Audit Results for Sulfate by the Manual Methods 22
13 Audit Results for Sulfate by the Automated Methods .... 23
14 Percentage of Sulfate Measurements Within Indicated
Percentage of Assigned Value (Statistical Outliers
Removed . ...... 24
15 Audit Results for Nitrate on Filter Strips 25
16 Audit Results for Nitrate by the Automated Methods .... 26
17 Percentage of Nitrate Measurements Within Indicated
Percentage of Assigned Value (Statistical Outliers
Removed) 27
18 Audit Results for Lead on Filter Strips 28
19 Percentage of Lead Measurements Within Indicated
Percentage of Assigned Value (Statistical Outliers
Removed 29
20 Audit Results for Sulfur Dioxide Continuous Monitors
(All Data) 30
21 Audit Results for Sulfur Dioxide Continuous Monitors
by Various Instrumental Methods 30
22 Audit Results for High-Volume Flow Rate 31
23 Percentage of Hi-Vol Flow Measurements Within
Indicated Percentage of Assigned Value (All Data) .... 31
24 Acid Rain Results for pH, Conductivity and Acidity
(All Data) 32
VI1
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TABLES (Con't.)
Number Page
25 Acid Rain Audit Results for pH, Conductivity and
Acidity (Outliers Removed) 33
26 Acid Rain Audit Results for Anions (All Data) 34
27 Acid Rain Audit Results for Anions (Outliers Removed). . . 35
28 Acid Rain Audit Results for Cations (All Data) 36
29 Acid Rain Audit Results for Cations (Outliers Removed) . . 37
30 Acid Rain Audit Results for Trace Metals (All Data). ... 38
31 Acid Rain Audit Results for Trace Metals
(Outliers Removed) 39
Vlll
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FIGURES
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
S02 Bubbler Audits . . ,
NC>2 Bubbler Audits . . ,
Carbon Monoxide Audits .
Sulfate Audits . . . . ,
Nitrate Audits
Lead Audits
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
Acid Rain Audit Results
for pH ,
for Conductivity . . .
for Acidity ,
for 804 (Reported as S)
for N03 (Reported as N)
for Cl ,
for F ,
for NH4 (Reported as N)
for Ca ,
for K ,
for Mg ,
for Na . . ,
for Mn
for Fe ,
for Cd ,
for Ca .........
for Ni ,
for Pb ,
for Zn ,
40
40
41
41
42
42
43
43
44
44
45
45
46
46
47
47
48
48
49
49
50
50
51
51
52
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ACKNOWLEDGMENTS
Recognition is due to the technical staff of Northrop Services, Inc.,
Research Triangle Park, North Carolina, who produced and analyzed all of
the high quality chemical samples utilized in the audits. Also, we thank
the staff of Global Geochemistry, Inc. for their responsive analytical
services as the referee laboratory. Appreciation is due, too, to our QAD/
EMSL colleagues, who contributed to the diverse activities associated with
the audits, in particular Linda Porter, Avis Hines and Dorothy Drooz.
XI
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SECTION 1
INTRODUCTION
The ambient air audits of analytical proficiency are managed by the
Environmental Monitoring Systems Laboratory (EMSL), of the U.S. Environmen-
tal Protection Agency (EPA). These audits are a part of a continuing
program entitled the National Performance Audit Program. This program
allows EPA to monitor the performance of laboratories (agencies) making air
pollution measurements to assist EPA in assessing the quality of air moni-
toring data. It also allows participating agencies to assess their per-
formance with respect to other agencies making similar measurements. The
audits are conducted by the Quality Assurance Division (QAD) of EMSL.
Inquiries and applications to participate should be directed to: U.S.
Environmental Protection Agency, Quality Assurance Division, Environmental
Monitoring Systems Laboratory, MD-77B, Research Triangle Park, North Caro-
lina 27711.
Agencies participating in the audits are solicited by the EPA Regional
Quality Control Coordinator in each of EPA's 10 regions. Agencies perform-
ing ambient air monitoring of criteria pollutants are required by Federal
regulation to participate. Once a laboratory enrolls in a particular audit,
it is automatically notified of subsequent audits of that pollutant. Parti-
cipants are assigned a permanent identifying code number. Federal, state,
local, industrial and foreign air pollution monitoring agencies participate
in the surveys.
Sample materials furnished for the audits are designed to simulate the
several types of collected air pollution samples as closely as possible.
The materials for the manual methods evaluate only the analytical portion
of the total air measurement process; i.e., they do not determine errors in
sample collection, transportation, handling, storage, and data processing.
For the high volume method for total suspended particulate (TSP), the audit
evaluates only the flow measurement portion of the method.
In 1984, audits were conducted twice for lead, sulfate, nitrate and
acid rain and once for carbon monoxide, high-volume flow rate, manual
sulfur dioxide and manual nitrogen dioxide. Audits on S02 continuous
monitors were conducted throughout the year.
Each laboratory participating in an audit received an evaluation of
its performance shortly after the audit was completed. When practical,
laboratories submitting abnormally high or low results were offered an
opportunity to analyze another set of samples. However, the retest results
are not included in this summary report.
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There are approximately 667 laboratories registered in the National
Performance Audit Program. This report presents the results of those labo-
ratories that participated in the 1984 audits. The category and number of
participants in each audit are presented in Table 1. Compared to the 1983
audits (1) the number of participants in the SC>2 and N(>2 bubbler audits
decreased by 20% and the number in the CO audit decreased 50% (only one
audit was done in 1984 versus two in 1983^. Participation in the other
audits, however, increased as follows: S0^~, 7%; NOj", 5%; Pb, 4%; high
volume flow rate, 4%, and S02 continuous, 18%.
Throughout this report, reference is made to "assigned values." These
values are the standards against which reported results are evaluated and
have been so designated after consideration of the analytical results of
the referee laboratory, the QAD/EMSL Standards Laboratory, and the manufac-
turer of the audit material.
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SECTION 2
SUMMARY AND CONCLUSIONS
The 1984 results closely parallel those of last year. The overall
average accuracy for all 1984 audits is 95 percent, the same as for the
1983 and 1982 audits (I, 2). With outliers removed and the values for all
levels averaged, the percentage of results within 20 percent of the as-
signed values ranged from a low of 92% (nitrate) to a high of 100% (N02).
The following percentage of results were rejected as outliers for each
type of audit: SO, bubbler (0%), N02 bubbler (0%), CO (1.8%), S04= (3.7%),
N03~ (7.7%), Pb (4.47%), flow rate (6.6%), S02 continuous (0%) and acid
rain (0%).
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SECTION 3
AUDIT MATERIALS
The audit samples span the wide range of pollutant concentrations
experienced in ambient air monitoring. This is achieved directly with the
CO samples, which are prepared in cylinders. Dilution is necessary for the
acid rain samples, lyophilized S02 and aqueous N02 samples in order to obtain
desired concentrations. Lead, NO-> , and SO*" filter strip samples require
both dissolution and dilution to arrive at the needed range of concentra-
tions. The S02 continuous monitor audit samples require dilution of the
S02 with zero air.
Although many air monitoring sites rarely encounter pollutant concen-
trations at the higher audit sample levels, these concentrations are in-
cluded to assure that monitoring methods are verified at the higher levels.
The following paragraphs describe each sample type used in the 1984
audits.
SULFUR DIOXIDE (MANUAL)
Lyophilized samples, composed of sodium sulfite and potassium tetra-
chloromercurate, simulate ambient air samples collected according to the
Pararosaniline Method, the reference method for determining S02 in the
atmosphere. In the 1984 audits, the concentrations ranged from approxi-
mately 65 to 220 ug of sulfur dioxide equivalent per cubic meter when
reconstituted properly. A sample set consisted of five different concen-
trations.
NITROGEN DIOXIDE (MANUAL)
Nitrogen dioxide samples consist of aqueous sodium nitrite solutions
that simulate ambient N02 samples collected by a 24-hour N02 bubbler method.
Audit results are expressed in terms of micrograms per milliliter (nitrite
concentration). These solutions, when properly diluted according to direc-
tions, are equivalent to collected atmospheric N02 concentrations of approx-
imately 0.4 to 1.2 yg/m£. A sample set consists of five different concen-
trations.
CARBON MONOXIDE
These audit materials consist of a mixture of CO, C02 and CIfy and zero
air in a pressurized gas cylinder that simulates an ambient air sample. The
concentrations of the three CO samples used in the 1984 audits ranged from
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4 to 41 ppm. Directions specify that the gas sample be introduced into a
continuous analyzer in the "sample" mode, which permits the analyzer to
draw the sample in the same fashion and at the same flow rate as during
ambient air monitoring.
SULFATE, NITRATE, AND LEAD ON FILTER STRIPS
The filter strip samples used in sulfate, nitrate and lead audits are
each 1.9 cm wide by 20 cm long. They are cut from 20- by 24-centimeter
glass fiber filters that have been spiked with an aqueous solution of the
appropriate solution and then oven dried. After analysis, pollutant con-
centrations are computed by assuming that the samples were collected on the
prescribed high-volume filter with a sample air volume of 2,000 m3. Six
sample strips comprise a set.
Sulfate and nitrate audit samples are prepared from sodium sulfate and
potassium nitrate. Calculated nitrate concentrations ranged from 0.85 to
14.0 pg/m3 and sulfate from 1.7 to 26.0 yg/m3. Lead samples, which are
prepared from lead nitrate ranged in concentration from 0.61 to 7.4 pg/m3
of lead.
HIGH-VOLUME FLOW RATE (ReF DEVICE)
The reference flow (ReF) device used for audits of high-volume flow
rates consist of a modified orifice, a wind deflector, a manometer, and a
series of resistance plates that simulate particulate loading. A single
ReF device is supplied to each participating agency with instructions to
check samplers at as many sampling sites as feasible within the allotted
time.
Each ReF device is calibrated with a positive displacement meter
before use. During use, the device is mounted on top of the sampler,
replacing the filter face plate. A wind deflector is used to prevent
fluctuations in the measurements due to wind blowing across the orifice.
SULFUR DIOXIDE CONTINUOUS MONITORS
The continuous monitor auditing system is an auditing device for S02
continuous ambient air monitors. The device is a porous plug dilution
system that provides a mechanism whereby controlled quantities of S02 and
diluent air are continuously combined in a mixing chamber and passed into
the monitor. The flow rate of each gas is controlled by maintaining a
predetermined pressure drop across the porous plus flow restrictor. Vari-
able S02 concentrations are obtained by switching between four restrictors.
The audit device, which is housed in a compact, lightweight, impact-
resistant case, is constructed so that only those controls required for
system operation are exposed. By opening and closing different toggle
valves, it is possible to generate up to seven preset pollutant concentra-
tions. Five are used for the audit. Two compressed gas cylinders are
supplied with each unit, one as the pollutant source and the other for
dilution.
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Each audit device is calibrated for flow at all the settings used in
the audit. Flow calibrations are referenced to laminar flow elements
traceable to National Bureau of Standards flow standards. Sulfur dioxide
concentrations ranging from 0.00 to 0.702 ppm were used in the 1984 audits.
ACID RAIN
Approximately 34 laboratories participated in each 1984 audit. Five
samples in polyethylene bottles were shipped to each of the participa-
ting laboratories. Three samples were analyzed for pH, conductivity,
acidity and the major cations and anions normally measured in precipitation
samples. The other two samples were analyzed for heavy metals. The latter
two samples were acid stabilized to prevent loss of metals from the solution.
The chemical composition of these samples was certified by the U.S.
National Bureau of Standards. The participants analyzed the samples using
the analytical procedures they normally employ when analyzing their precip-
itation samples. The results were reported based on the sample concentra-
tion after dilution (1:50).
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SECTION 4
AUDIT RESULTS
The results of the 1984 audit are presented in Tables 2 through 31.
The term "audit mean" in these tables denotes the average of all values re-
ported by the participants for that sample after elimination of outliers.
Elimination of outliers was accomplished in a two step procedure. First,
results from laboratories/sites reporting values exceeding ± 20 percent of
the assigned value for all samples in a particular audit were removed from
the data base. These excluded values represented 4.8 percent of the total
number of laboratories/sites reporting results (approximately the same as
in 1982 and 1983). Then, individual results were rejected as outliers
based on Chauvenet's Criterion (4). After eliminating outliers, the results
from all participants were normally distributed.
At each audit level, the percent accuracy (% Ace.) and the precision,
as measured by the percent coefficient of variation (%CV), were computed as
follows:
% Ace. = audit mean - EPA assigned value x IQQ
EPA assigned value
% CV = audit standard deviation x IQQ
audit mean
The percent accuracy measures how well the average of all participants
agrees with EPA's assigned values. The percent coefficient of variation
measures the variability among participants. The accuracy results for the
acid rain audit were also calculated in terms of the median because of the
low participation level.
Overall accuracy and precision values for each audit were also calcu-
lated and plotted (Figures 1 through 25) to show the historical record of
performance for each type of audit. Many readers may find that scanning
these figures provides a better understanding of the 1984 results compared
to scanning the tabulated results and reading the text of this report.
SULFUR DIOXIDE (BUBBLER)
Twenty laboratories participated in the audit - 20 percent less than in
1983. Participation has steadily decreased since 1981 (3) due to the in-
creasing number of laboratories changing to automated analyzers. Because of
the low level of participation, this audit will be discontinued after 1985.
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The audit mean, percent accuracy and percent CV, with and without out-
liers, are reported in Table 2. As usual the lowest precision and accuracy
was achieved in level one. Overall, however, the average percent accuracy
appears to have stabilized over the past four audits when compared to
audits of previous years (Figure 1). Precision, which improved in 1982 and
1983 continued to improve (Figure 1).
As shown in Table 3, accuracy for the manual pararosaniline method,
ranged from -11.6 to 6.6% for all data and -3.8 to 5.0% after outliers
are removed. Accuracy for the automated method ranged from -0.44 to 21.3%
for all data and 0.44 to 9.6% after outliers were removed. Concentration
did not appear to affect the precision for either methods.
Table 4, constructed with the outliers removed, shows the percentage of
laboratories that obtained results within ± 10, 20, 30 and 50 percent of the
assigned values. Better than 90 percent of the measurements fell within 20
percent of the assigned values, a greater percentage than 1983 (87%) and 1982
(88%).
NITROGEN DIOXIDE
Twenty-one laboratories participated in the 1984 audit — 20% less than
in 1983 and 50% less than in 1982. The decrease, which occurred among the
state and local participants, likely resulted because an increasing number
of laboratories are replacing bubblers with continuous analyzers. Because
of the low level of participation, this audit will be discontinued after
1985.
The audit mean, percent accuracy and percent CV with and without out-
liers are reported in Tables 5 and 6. The accuracy was about the same as for
1983 audits (Figure 2). This figure also shows that with a few exceptions
the precision and accuracy over the years has been good. In fact, in 1984,
all values were within 10% of the .assigned value.
CARBON MONOXIDE
In 1984, 330 monitors were audited — a 50% decrease from 1983. This
decrease occurred because for budgetary reasons only one audit was done in
1984 versus two in 1983. Ninety-five percent of the monitors audited were
NDIR — about the same as 1983. Although other types of CO monitors were
also audited, the number were too few to make meaningful comparisons with
the 1983 audit results.
As shown in Figure 3, both precision and accuracy have reached a
plateau in the last five years. For example, the number of measurements
falling within 20% of the assigned value (Table 10) closely parallels the
1983 and 1982 results. Also, as shown in Figure 3, the accuracy has oscil-
lated back and forth across the x-axis for the last four years.
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SULFATE ON FILTER STRIPS
Approximately 55 laboratories participated in each audit — about 7
percent fewer than in 1983. The audit mean, percent accuracy and preci-
sion are given in Table 11. Over the years accuracy has varied quite a
bit, but it now seems to have stabilized (Figure 4). Precision, on the
other hand, has continued to improve slightly. In 1983, the precision and
accuracy of the manual method increased with concentration, but this year,
no such relationship is apparent (Table 12). As in 1983, there also is no
apparent relationship between concentration and either precision or accu-
racy for the automated method (Table 13).
Except for the lowest sample concentration, between 70 and 96 percent
of the laboratories reported results within ± 20 percent of the assigned
values (Table 14). These results are worse than for 1983 where the values
were 84 and 97 percent, respectively.
NITRATE ON FILTER STRIPS
Approximately 46 laboratories participated in each 1984 audit. Parti-
cipation was down approximately 2 percent from 1983 but, as in the sulfate
audits, the number of participants has been fairly constant since 1979.
Accuracy continues to vary widely from audit to audit, but precision seems
to have reached a plateau (Figure 5).
The results from the 1984 nitrate audits show a slight decrease in
both precision and accuracy with respect to the 1983 audits (Figure 5,
Table 15). This decrease is also evident in the automated methods (Table
16) which reverses the general improvement that was observed in 1982 and
1983.
Some other methods used by a few of the participants included the man-
ual cadmium reduction, brucine, hydrazine, 2,4 xylenol, selective ion elec-
trode, and the szechrome NAS methods. The number of results reported was
too small to calculate precision and accuracy.
The percentage of values that fell within ± 20 percent of the assigned
values was considerably lower (84%) than in 1983 (90%) and 1982 (90%).
LEAD ON FILTER STRIPS
One hundred and four laboratories participated in the 0184 audit and
102 in the 0784, a 3 percent increase over the 1983 audits. The increase
was due to more participation from federal and foreign agencies. Partici-
pation has leveled off in the past three years and has ranged from 95 to
105 laboratories per audit.
The audit mean, percent accuracy and percent CV (precision) are shown
in Table 18. Accuracy has continued to show the negative bias present
since the audits were initiated in 1977 and precision has remained at the
same level since 1982 (Figure 6). (There is no explanation for the nega-
tive bias at this time.) In 1984 the number of measurements within ± 20
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percent of the assigned value (79%) was slightly lower (Table 19) than in
the 1983 audits. With the exception of two laboratories using the induc-
tively coupled argon plama optical emission spectrometric method, all
others used the atomic absorption method.
SULFUR DIOXIDE (CONTINUOUS MONITORS)
The number of monitors audited totaled 221 (Table 20). Compared to
1983, this was an increase of 18 percent and resulted mainly because of
increased participation among local agencies.
The accuracy for each of the methods is shown in Table 21. The methods
most commonly used were: fluorescence (204), flame photometric (8) and
coulometric (5). In relation to 1983, these numbers represent a 30% in-
crease, 300% decrease and 15% decrease, respectively. Whether the large
decrease in the number of flame photometric analyzers and the large increase
in the number of fluorescent analyzers represents a shift in user preference
is not known at this time. With one exception the accuracy of the fluores-
cent and the coulometric methods showed improvement over the 1983 results.
HIGH VOLUME
The number of monitors audited in 1984 was 1402 which represented a
4% increase over 1983. The pressure transducer continued to be the most
widely used method of measurement (49.4%), the rotameter was next (27.5%),
followed by pressure transducer/flow controller (5.5%). Other methods
which accounted for the remaining 17.6 percent of the results, included:
orifice manometer, manometer, flow gauge, and pressure transducer/non-con-
tinuous. The results (Table 22) showed an overall decrease in accuracy
compared to 1983. For example, in 1983 20% of the results were within 1.1%
of the assigned value (all methods) but in 1984 only 20% were within 1.3%.
The corresponding values at 40% were 2.3 and 2.7.
Table 23 shows the percentage of the flow measurements within ± 20%
of the true value for each resistance plate used in the ReF (audit) device.
These results are similar to the CY-83 results.
ACID RAIN
Thirty-seven laboratories participated in the 0484 audit and thirty-
three participated in the 1184 audit. Overall this represents a 17% in-
crease in participation compared to 1983. Because of the short history
of this audit (1983 was only the second year), it is possible at this time
to make only general observations about the results. In the tables that
follow, the accuracy is expressed in terms of the mean value. However, the
low participation level in each audit means that only a few analyses are
reported for certain of the analytes. In such situations the median value
may give a better estimate of the accuracy. For this reason the percent
accuracy is presented in Figures 7 to 25 in terms of the median (solid
line) and the mean (dashed line).
10
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Also, because of the low concentrations present in some of the samplers,
the relative precision sometimes appears as poor, when, in absolute terms
(e.g., mg/1) the precision is reasonably good.
Results for pH, Conductivity and Acidity
The results are presented in Table 24 (all data), Table 25 (outliers
removed) and in Figures 7 (pH), 8 (conductivity) and 9 (acidity). Inspec-
tion of the data in the tables does not reveal any correlation between sam-
ple concentration and either precision or accuracy. This is very different
from the ambient air audits reported earlier in this report, i.e., for these
latter audits precision and accuracy generally correlate with the concentra-
tion. For both pH and acidity, the median and the mean value give approxi-
mately the same overall accuracy result (Figures 7 and 9, respectively).
However, in the calculation of the overall accuracy for conductivity, the
results from using the mean value differs considerably from that obtained
using the median value. Precision on the other hand has been relatively
constant for pH and conductivity (Figures 7 and 8, respectively) but it has
been erratic for acidity.
Major Anions Results (S04, N03, Cl, F)
The results for these four parameters are presented in Table 26 (all
data), Table 27 (outliers removed) and in Figures 10 (804), 11 (N03), 12
(Gl) and 13 (F). Inspection of these figures shows that the % accuracy
value calculated from the median value generally agrees with that calcu-
lated for the mean value. Precision has exceeded 10 percent in all audits
and has also been erratic. As shown by comparing the precision in Tables
26 and 27, however, removal of only a few results yields a larger improve-
ment in precision. Thus, the results are not as poor as they appear on
the surface.
Major Cations (Nlfy, Ca, K, Mg, Na)
The results for these five major ions are presented in Table 28 (all
data), Table 29 (outliers removed) and in Figures 14 (Nlty), 15 (Ca), 16 (K),
17 (Mg) and 18 (Na). Inspection of these figures shows that for three of
the ions (Nlty, Ca, K) the % accuracy value calculated from the median value
agrees with that calculated from the mean value. This is not the case,
however, for the other two ions (Mg, Na). As in the case for the major
anions, the precision has been erratic for all five anions over the history
of the audit. But, also as in the anion case, removing just one or two
values yields a dramatic improvement in precision. Thus, the results are
not as poor as they appear.
Trace Metals Results (Mn, Fe, Cd, Cu, Ni, Pb, Zn)
The results for these seven metals are presented in Table 30 (all
data), Table 31 (outliers removed) and in Figures 19 (Mn), 20 (Fe), 21 (Cd),
22 (Cu), 23 (Ni), 24 (Pb), and 25 (Zn). As in the case for the cations,
for some metals the % accuracy as calculated from the median value agrees
well with that calculated from the mean value (Mn, Cd, Cu and Zn), but this
is not the case for the other metals (Fe, Ni, and Pb). Also as in the case
11
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of both the anions and cations, the precision has varied in an erratic manner
for most of these metals (Zn is the exception). It should be borne in mind,
however, that the small concentrations used for these metals does mean that
a small absolute difference appears as a large relative difference.
12
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REFERENCES
1. Lampe, R.L., B.F. Parr, G. Pratt, O.L. Dowler and W.J. Mitchell.
National Performance Audit Program. Ambient Air Audits of Analytical
Proficiency, 1983. U.S. Environmental Protection Agency Report EPA
600/4-84-077. Research Triangle Park, North Carolina 27711. October
1984.
2. Lampe, R.L., B.F. Parr, B.I. Bennett, G. Pratt and W.J. Mitchell.
National Performance Audit Program. Ambient Air Audits of Analytical
Proficiency, 1982. U.S. Environmental Protection Agency Report EPA
600/4-84-005. Research Triangle Park, North Carolina 27711. January
1984.
3. Bennett, B.I., R.L. Lampe, L.F. Porter, A.P. Hines and J.C. Puzak.
National Performance Audit Program. Ambient Air Audits of Analytical
Proficiency, 1981. U.S. Environmental Protection Agency Report EPA
600/4-83-009. Research Triangle Park, North Carolina 27711. April
1983.
4. Chauvenet, W. A Manual of Spherical and Practical Astronomy. J.B.
Lipincott and Company, Philadelphia, Pennsylvania, 1863. pp. 558-566.
13
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TABLE 1. AGENCY PARTICIPATION
Distribution (%)
Survey
SO 2
N02
CO
804
S04
N03
N03
Pb
Pb
S02
— June 1984
— June 1984
— April 1984
— February 1984
— August 1984
— February 1984
— August 1984
— January 1984
— July 1984
(continuous)
States
20.0
38.1
43.8
47.3
41.7
44.4
45.6
40.8
41.1
56. 1
Local
45.0
42.9
43.6
20.0
18.9
15.6
15.2
24.2
27.4
39.8
Industry
30.0
19.0
7.3
21.8
24.7
28.9
23.9
26.4
23.5
2.3
Federal
5
0
0
1
3
0
2
4
3
0
.0
.0
.1
.8
.4
.0
.2
.3
.9
.9
Foreign
0
0
5
9
11
11
13
4
3
0
.0
.0
.2
.1
.3
.1
.1
.3
.9
.9
No. of
Laboratories3
20
21
—
55
53
45
46
104
102
—
(0)
(0)
(2)
(2)
(2)
(7)
(5)
(4)
No. of
Monitors3
—
—
330 (6)
—
1111
— —
-~ —
221 (0)
High-Volume Flow-Rate —
May
Acid
Acid
1984
Rain — April 1984
Rain — October 1984
37.7
43.2
42.4
7.2
8.1
12.1
13.2
27.0
30.3
0
21
15
.4
.6
.2
1
0
0
.5
.0
.0
_«
37
33
1402 (92)
—
3Value in parentheses is the number of laboratories/monitors that reported all values off by more than ± 20%
from the true value.
-------
TABLE 2. AUDIT RESULTS FOR MANUAL SULFUR DIOXIDE
METHOD (BUBBLER)
Audit
Level
n
Assigned
value (yg/m^)
Mean
% Ace.
% CV
A. ALL DATA
0684
0684
1
2
3
4
5
1
2
3
4
5
20
20
20
19
20
19
20
19
18
18
67.70
91.60
122.60
145.20
218.20
B. OUTLIERS
67.70
91.60
122.60
145.20
218.20
71.16
90.88
113.20
152.57
226.33
REMOVED
66.51
90.88
118.55
151.23
223.48
5.11
-0.79
-7.67
5.00
3.73
-1.76
-0.79
-3.30
4.15
2.42
30.35
7.47
22.19
6.50
33.37
9.08
7.47
6.60
5.46
5.09
15
-------
TABLE 3. RESULTS FOR THE PARAROSANILINE METHOD
Manual Method
Audit
0684
Level
1
2
3
4
5
Assigned
value
(pg/m3)
67.70
91.60
122.60
145.20
218.20
n
13
13
13
12
13
Mean
(pg/m3)
72.19
88.06
108.42
148.72
205.66
(01)
% Ace.
A.
6
-3
-11
2
-5
% CV
n
Automated
Mean
(pg/m3)
Method (02)
% Ace.
% CV
ALL DATA
.63
.86
.57
.42
.75
B. OUTLIERS
0684
1
2
3
4
5
67.70
91.60
122.60
145.20
218.20
12
13
12
11
12
64.92
88.06
116.50
147.16
220.87
-4
-3
4
1
1
.11
.86
.98
.35
.22
36.72
6.06
27.83
4.91
27.20
REMOVED
6.28
6.06
7.07
3.50
5.23
7
7
7
7
7
7
7
7
7
6
69.25
96.12
122.06
159.17
264.71
69.28
96.12
122.06
159.17
228.69
3.29
4.83
-0.44
9.62
21.32
2.33
4.93
-0.44
9.62
4.81
11.65
6.56
4.90
6.79
36.16
11.65
6.56
4.90
6.79
4.31
-------
TABLE 4. PERCENT OF SULFUR DIOXIDE MEASUREMENTS WITHIN INDICATED
PERCENT OF ASSIGNED VALUES (ALL DATA)3
Audit
0684
Level
1
2
3
4
5
Assigned
value (pg/m^)
67.70
91.60
122.60
145.20
218.20
10%
70.0
80.0
90.0
75.0
75.0
20%
95.0
100.0
90.0
90.0
90.0
30%
95.0
100.0
95.0
95.0
90.0
50%
95.0
100.0
95.0
95.0
90.0
Percentage difference table unchanged after outliers deleted.
TABLE 5. AUDIT RESULTS FOR NITROGEN DIOXIDE
MANUAL METHOD (BUBBLER)
Audit
0684
0684
Level
1
2
3
4
5
1
2
3
4
5
n
21
21
21
21
21
19
20
20
21
21
Assigned
value (pg/ml)
A. ALL
0.363
0.636
0.750
0.960
1.205
B. OUTLIERS
0.363
0.636
0.750
0.960
1.205
Mean
( lag/ml )
DATA
0.355
0.602
0.748
0.956
1.147
REMOVED
0.352
0.600
0.750
0.956
1.147
% Ace.
-2.20
-5.35
-0.27
-0.42
-4.81
-3.03
-5.66
0.00
-0.42
-4.81
% CV
4.23
2.82
2.27
3.35
2.44
2.56
2.27
2.00
3.35
2.44
17
-------
TABLE 6. AUDIT RESULTS FOR NITROGEN DIOXIDE BY THE SODIUM ARSENITE METHOD
oo
Manual Method (05)
Audit
0684
0684
Level
1
2
3
4
5
1
2
3
4
5
Assigned
value
(yg/mL)
0.363
0.636
0.750
0.960
1.205
0.363
0.636
0.750
0.960
1.205
n
14
14
14
14
14
14
13
17
14
14
Mean
(ng/mL)
0.356
0.600
0.751
0.954
1.146
B.
0.356
0.596
0.751
0.954
1.146
% Ace.
A. ALL DATA
-1.93
-5.66
0.13
-0.63
-4.90
% CV
4.78
3.17
2.13
3.77
2.53
n
7
7
7
7
7
Automated Method (06)
Mean
(yg/mL)
0.354
0.607
0.740
0.959
1.150
% Ace.
-2.48
-4.56
-1.33
-0.10
-4.56
% CV
2.26
2.47
2.57
2.50
2.35
OUTLIERS REMOVED
-1.93
-6.29
0.13
-0.63
-4.90
4.78
2.18
2.13
3.77
2.53
7
7
7
7
7
0.354
0.607
0.740
0.959
1.150
-2.40
-4.56
-1.33
-0.10
-4.56
2.25
2.47
2.57
2.50
2.25
-------
TABLE 7. PERCENTAGE OF NITROGEN DIOXIDE MEASUREMENTS WITHIN INDICATED
PERCENTAGE OF ASSIGNED VALUE (ALL DATA)3
Audit
0684
Level
1
2
3
4
5
Assigned
value (pg/mL)
0.36
0.64
0.75
0.96
1.21
10%
100.0
100.0
100.0
100.0
100.0
20%
100.0
100.0
100.0
100.0
100.0
30%
100.0
100.0
100.0
100.0
100.0
50%
100.0
100.0
100.0
100.0
100.0
Percentage distribution table unchanged after outliers removed.
TABLE 8. AUDIT RESULTS FOR CARBON MONOXIDE
Audit
0484
Level
1
2
3
n
333
334
332
Assigned
value (ppm)
A. ALL DATA
4.33
17.59
40.50
Mean
(ppm)
4.33
17.62
40.51
% Ace.
0.00
0.17
0.02
% CV
50.12
10.56
5.87
B. OUTLIERS REMOVED
0484
1
2
3
324
322
321
4.33
17.59
40.50
4.18
17.69
40.79
-3.46
0.57
0.72
10.53
3.45
2.60
19
-------
TABLE 9. AUDIT RESULTS FOR CARBON MONOXIDE BY THE NDIR METHOD
Audit
0484
0484
Level
1
2
3
1
2
3
Assigned
value (ppm)
4.33
17.59
40.50
4.33
17.59
40.50
NDIR
n
308
309
307
301
299
298
Mean (ppm)
A. ALL
4.34
17.64
40.51
B. OUTLIERS
4.19
17.71
40.79
% Ace.
DATA
0.23
0.28
0.02
REMOVED
-3.23
0.68
0.72
% CV
51.84
10.77
5.75
10.50
3.39
2.60
TABLE 10. PERCENTAGE OF CARBON MONOXIDE MEASUREMENTS WITHIN INDICATED
PERCENTAGE OF ASSIGNED VALUE
Audit
0484
Level
1
2
3
Assigned
value (ppm)
A.
4.33
17.59
40.50
10%
ALL DATA
77.6
96.7
99.4
20%
96.7
98.8
98.5
30%
98.5
99.4
98.8
50%
99.4
100.0
100.0
B. OUTLIERS REMOVED
0484
1
2
3
4.33
17.59
40.50
78.0
98.5
99.4
95.4
99.4
99.4
98.8
99.7
99.4
99.4
100.0
100.0
20
-------
TABLE 11. AUDIT RESULTS FOR SULFATE ON FILTER STRIPS
Audit
0284
0884
Level
1
2
3
4
5
6
1
2
3
4
5
6
n
52
54
55
55
55
55
51
51
53
53
53
51
Assigned
value (pg/m^)
A. ALL DATA
1.72
3.24
7.75
11.34
18.73
25.59
1.98
3.54
11.58
25.88
18.64
5.04
Mean
(Ug/m3)
2.20
3.50
8.03
11.08
18.16
24.59
2.40
3.76
12.74
26.30
19.40
5.93
% Ace.
27.91
8.02
3.61
-2.29
-3.04
-3.91
21.21
6.21
10.02
1.62
4.08
17.66
% CV
62.72
32.29
39.48
19.68
11.67
13.58
33.75
34.84
33.99
35.36
35.57
40.98
B. OUTLIERS REMOVED
0284
0884
1
2
3
4
5
6
1
2
3
4
5
6
48
49
51
52
51
52
46
47
51
50
50
48
1.72
3.24
7.75
11.34
18.73
25.59
1.98
3.54
11.58
25.88
18.64
5.04
1.96
3.31
7.78
11.18
18.39
24.50
2.18
3.54
11.95
25.44
18.83
5.37
13.96
2.16
0.39
-1.41
-1.82
-4.26
10.10
0.00
3.20
-1.70
1.02
6.55
33.16
16.31
9.77
9.84
7.40
10.24
19.27
13.28
6.03
5.90
6.11
12.66
21
-------
TABLE 12. AUDIT RESULTS FOR SULFATE BY THE MANUAL METHODS
N>
BaCl2 (17)
Audit
0284
0884
0284
0884
Level
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
Assigned
value
(yg/m3)
1.72
3.24
7.75
11.34
18.73
25.59
1.98
3.54
11.58
25.88
18.64
5.04
1.72
3.24
7.75
11.34
18.73
25.59
1.98
3.54
11.58
25.88
18.64
5.04
n
8
9
9
9
9
9
10
10
10
10
10
10
8
9
8
8
9
9
10
10
10
9
10
10
Mean
(pg/m3)
2.39
3.35
7.20
10.63
17.49
23.33
3.04
4.30
12.15
25.01
19.09
6.76
B.
2.39
3.35
7.81
11.17
17.49
23.33
3.04
4.30
12.15
24.50
19.09
5.91
% Ace.
A. ALL DATA
38.95
3.40
-7.10
-6.26
-6.62
-8.83
52.54
21.47
4.92
3.36
2.41
34.13
% CV
41.84
16.72
28.33
17.59
15.78
11.62
26.32
24.42
5.10
7.36
7.70
42.16
n
2
2
3
3
3
3
2
2
3
3
3
2
Sulfa-Ver (19)
Mean
(pg/m3)
1.50
1.97
5.91
11.23
18.01
24.19
2.28
3.40
11.68
23.62
17.06
5.51
% Ace.
-12.79
-39.20
-23.74
-0.97
-3.84
-5.47
15.15
-3.95
0.86
-8.73
-8.48
9.33
% CV
130.00
119.80
61.08
10.77
9.33
4.96
21.49
10.29
9.67
13.76
11.20
2.90
OUTLIERS REMOVED
38.95
3.40
0.77
-1.50
-6.62
-8.83
53.64
21.47
4.92
-5.33
2.41
17.26
41.84
16.72
12.42
8.86
15.78
11.62
26.32
24.42
5.10
3.88
7.70
17.09
2
2
3
3
3
3
2
2
3
3
3
2
1.50
1.97
5.91
11.23
18.01
24.19
2.28
3.40
11.68
23.62
17.06
5.51
0.00
-39.20
-23.74
-0.97
-3.84
-5.47
15.15
-3.95
0.86
-8.73
-8.48
9.33
130.00
119.80
61.08
10.77
9.33
4.96
21.49
10.25
9.67
14.18
11.20
2.90
-------
TABLE 13. AUDIT RESULTS FOR SULFATE BY THE AUTOMATED METHODS
Methyl Thymol Blue (16)
Audit
0284
0884
0284
0884
Level
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
Assigned
value
(pg/m3)
1.72
3.24
7.75
11.34
18.73
25.59
1.98
3.54
11.58
25.88
18.64
5.04
1.72
3.24
7.75
11.34
18.73
25.59
1.98
3.54
11.58
25.88
18.64
5.04
n
24
24
24
24
24
24
22
22
23
23
23
22
22
21
21
23
23
22
21
21
23
22
23
22
Mean
(yg/m3)
2.26
3.50
8.60
11.16
18.03
24.08
2.12
3.45
11.96
25.53
18.91
5.78
B.
1.85
3.28
7.73
11.14
18.37
24.06
2.03
3.39
11.96
25.74
18.91
5.38
% Ace.
A. ALL DATA
31.40
0.02
10.97
-1.59
-3.74
-5.90
7.07
-2.54
3.28
-1.36
1.46
14.68
% CV
78.31
34.00
49.88
8.78
10.93
16.36
25.00
12.17
5.27
6.46
5.71
10.59
n
13
14
14
14
14
14
15
15
15
15
15
15
Ion Chromatograph (34)
Mean
(ug/m3)
1.89
3.78
8.29,
11.15
19.09
25.88
2.43
3.95
14.62
28.98
20.89
6.38
% Ace.
9.88
16.67
6.97
-1.68
1.92
1.13
22.73
11.58
26.25
11.98
12.07
26.59
% CV
14.29
30.95
17.73
35.25
10.63
10.12
42.39
55.19
54.31
59.90
62.18
58.62
OUTLIERS REMOVED
7.56
1.23
-0.26
-1.76
-1.92
-5.98
2.53
-4.24
3.28
-0.54
1.45
6.76
24.86
12.80
5.69
6.10
5.82
9.19
14.78
9.14
5.27
5.32
5.71
10.59
11
12
12
12
12
12
12
13
12
12
12
12
1.88
3.33
7.73
11.39
18.42
26.06
2.09
3.49
11.66
25.75
18.38
4.98
9.30
2.78
-0.26
0.44
-1.66
1.84
5.56
-1.41
0.69
-0.50
-1.39
-1.19
7.45
7.21
3.36
7.90
5.81
7.25
4.78
5.44
4.97
2.72
3.37
5.42
-------
TABLE 14. PERCENTAGE OF SULFATE MEASUREMENTS WITHIN INDICATED PER-
CENTAGE OF ASSIGNED VALUE
Audit
0284
0884
Level
1
2
3
4
5
6
1
2
3
4
5
6
Assigned
value (jjg/m-^)
A.
1.72
3.24
7.75
11.34
18.73
25.59
1.98
3.54
11.58
25.88
18.64
5.04
10%
ALL DATA
29.1
45.5
76.4
81.8
76.4
67.3
49.1
56.6
61.1
84.9
83.0
62.3
20%
50.9
70.9
87.3
89.1
90.9
87.3
67.9
77. ^
96.2
94.3
94.3
79.2
30%
63.6
81.8
90.9
94.5
96.4
96.4
71.7
81.1
96.2
96.2
98.2
83.0
50%
76.4
87.3
92.7
96.4
100.0
100.0
81.1
90.6
96.2
96.2
96.2
88.7
B. OUTLIERS REMOVED
0284
0884
1
2
3
4
5
6
1
2
3
4
5
6
1.72
3.24
7.75
11.34
18.73
25.59
1.98
3.54
11.58
25.88
18.64
5.04
36.2
45.5
79.2
84.9
79.2
69.8
50.9
58.8
84.3
88.2
86.3
64.7
50.9
73.6
90.6
92.5
94.0
88.7
70.6
80.3
100.0
98.0
98.0
82.4
64.2
84.9
94.3
96.2
98.1
98.1
74.5
84.3
100.0
100.0
100.0
86.3
77.4
90.6
96.2
98.1
100.0
100.0
84.3
92.1
100.0
100.0
100.0
92.2
24
-------
TABLE 15. AUDIT RESULTS FOR NITRATE ON FILTER STRIPS
Audit Level
0284 1
2
3
4
5
6
0884 1
2
3
4
5
6
0284 1
2
3
4
5
6
0884 1
2
3
4
5
6
n
43
45
45
45
45
45
43
43
44
44
44
44
41
42
41
41
42
42
35
34
35
35
35
37
Assigned Mean
value (yg/nr*) (pg/m3)
A. ALL DATA
0.85
2.00
5.42
8.89
11.69
13.93
0.74
2.09
5.46
9.83
11.38
13.44
B. OUTLIERS REMOVED
0.85
2.00
5.42
8.89
11.69
13.93
0.74
2.09
5.46
9.83
11.38
13.44
1.25
2.26
5.48
8.48
11.29
13.06
0.99
2.36
6.12
10.62
12.54
14.82
1.07
2.26
5.56
9.02
11.69
13.49
0.83
2.15
5.41
9.64
11.44
13.49
% Ace.
47.06
13.00
1.11
-4.61
-3.42
-6.26
33.78
12.92
12.09
8.04
10.19
10.29
25.88
13.00
2.58
1.46
0.00
-3.16
12.16
2.87
-0.92
-1.93
0.53
0.37
% CV
107.20
34.50
20.43
25.23
15.77
18.30
68.69
61.86
60.29
63.37
62.68
67.11
27.10
20.35
8.63
11.53
6.50
11.71
19.07
16.46
9.06
6.85
5.16
7.12
25
-------
TABLE 16. AUDIT RESULTS FOR NITRATE BY THE AUTOMATED METHODS
NJ
Ion Chromatograph (34)
Audit
0284
0884
0284
0884
Level
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
Assigned
value
(pg/m3)
0.85
2.00
5.42
8.89
11.69
13.93
0.74
2.09
5.46
9.83
11.38
13.44
0.85
2.00
5.42
8.89
11.69
13.93
0.74
2.09
5.46
9.83
11.38
13.44
n
11
12
12
12
12
12
13
13
13
13
13
13
10
11
11
11
11
12
12
12
12
12
12
12
Mean
(pg/m3)
1.06
2.24
5.68
8.35
11.65
14.00
0.92
1.99
5.60
9.27
11.39
13.17
B.
1.01
2.15
5.58
9.05
11.79
14.00
0.82
2.09
5.27
9.61
11.27
13.36
% Ace.
A. ALL DATA
24.71
12.00
4.80
-6.07
-0.34
0.50
24.32
-4.78
2.56
-5.70
0.09
-2.01
% CV
22.64
20.54
7.92
29.22
5.66
10.57
46.74
19.60
22.14
13.27
4.30
6.30
n
21
21
21
21
21
21
16
16
17
17
17
17
Cadium Reduction (12)
Mean
(pg/m3)
1.41
2.27
5.33
8.21
10.85
12.45
1.00
2.64
6.73
12.08
14.27
16.69
% Ace.
65.80
13.50
-1.66
-7.65
-7.19
-10.62
35.14
26.32
23.26
22.89
25.40
24.18
% CV
135.46
41.41
28.71
29.84
21.57
23.69
78.00
65.91
68.20
66.64
64.54
62.49
OUTLIERS REMOVED
18.82
7.50
2.85
1.80
0.86
0.50
10.81
0.00
-3.48
-2.24
-0.97
-0.60
17.82
17.67
5.38
4.64
10.57
10.57
30.49
6.70
7.97
2.08
2.22
3.74
19
19
19
19
19
19
14
14
15
15
15
15
1.04
2.17
5.29
8.86
11.54
13.24
0.78
2.17
5.47
9.87
11.58
13.78
22.35
8.50
-2.40
-0.34
-1.28
-4.95
5.41
3.83
0.18
0.41
1.76
2.53
2.98
12.90
13.23
15.46
6.85
12.01
11.54
8.76
8.76
7.60
3.97
7.18
-------
TABLE 17. PERCENTAGE OF NITRATE MEASUREMENTS WITHIN INDICATED PER-
CENTAGE OF ASSIGNED VALUE
Audit
0284
0884
Level
1
2
3
4
5
6
1
2
3
4
5
6
Assigned
value (pg/m3)
A.
0.85
2.00
5.42
8.89
11.69
13.93
0.74
2.09
5.46
9.83
11.38
13.44
10%
ALL DATA
24.4
55.6
75.6
80.0
80.0
66.7
45.5
61.4
59.1
72.7
75.0
70.5
20%
46.7
68.9
88.9
86.7
91.1
86.7
59.1
68.2
77.3
79.5
79.5
77.3
30%
57.8
68.9
91.1
86.7
95.6
91.1
63.6
72.7
81.8
81.8
81.8
81.8
50%
75.6
86.7
95.6
93.3
97.8
95.6
68.2
79.5
86.4
88.4
81.8
81.8
B. OUTLIERS REMOVED
0284
0884
1
2
3
4
5
6
1
2
3
4
5
6
0.85
2.00
5.42
8.89
11.69
13.93
0.74
2.09
5.46
9.83
11.38
13.44
25.6
58.1
79.1
80.0
80.0
69.8
54.1
73.0
70.3
86.4
89.2
83.8
48.8
72.1
90.7
88.4
95.3
88.4
70.3
81.1
91.9
91.9
94.6
91.9
60.4
83.7
93.0
88.4
97.7
93.0
75.7
86.5
94.6
94.6
94.6
94.6
79.1
90.7
97.7
95.3
100.0
97.7
81.1
91.9
97.3
100.0
94.6
94.6
27
-------
TABLE 18. AUDIT RESULTS FOR LEAD ON FILTER STRIPS
Audit Level
0184 1
2
3
4
5
6
0784 1
2
3
4
5
6
0184 1
2
3
4
5
6
0784 1
2
3
4
5
6
n
103
104
103
104
104
104
102
102
102
102
101
102
95
97
96
98
97
95
97
97
96
96
93
94
Assigned Mean
value (yg/m3) (yg/m3)
A. ALL DATA
0.61
1.20
2.69
2.99
5.51
7.39
0.75
2.21
2.51
4.05
4.34
7.10
B. OUTLIERS REMOVED
0.61
1.20
2.69
2.99
5.51
7.39
0.75
2.21
2.51
4.05
4.34
7.10
0.58
1.17
2.62
3.01
5.29
6.95
0.73
2.06
2.37
3.86
4.16
6.85
0.58
1.15
2.62
2.95
5.27
7.04
0.73
2.10
2.39
3.91
4.21
7.01
% Ace.
-4.92
-2.50
-2.60
0.67
-3.99
-5.98
-2.67
-6.79
-5.58
-4.69
-4.16
-3.52
-4.92
-4.17
-2.60
-1.34
-4.36
-4.74
-2.67
-4.98
-4.78
-3.46
-3.00
-1.27
% CV
12.06
15.36
6.49
17.39
8.88
10.50
22.00
13.11
10.55
10.62
11.06
11.39
8.62
6.96
4.96
7.46
5.12
3.98
6.80
5.71
4.60
4.09
4.28
4.28
28
-------
TABLE 19. PERCENTAGE OF LEAD MEASUREMENTS WITHIN INDICATED PER-
CENTAGE OF ASSIGNED VALUE
Audit
0184
0784
0184
0784
Level
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
Assigned
value (pg/rn^)
A. ALL
0.61
1.20
2.69
2.99
5.51
7.39
0.75
2.21
2.51
4.05
4.34
7.10
B. OUTLIERS
0.61
1.20
2.69
2.99
5.51
7.39
0.75
2.21
2.51
4.05
4.34
7.10
10%
DATA
73.1
78.8
87.5
87.5
83.7
85.6
77.5
85.3
83.3
87.3
82.4
87.3
REMOVED
75.8
81.8
90.9
90.0
86.9
88.9
80.6
88.8
86.7
90.8
85.7
90.8
20%
90.4
93.3
98.1
95.2
95.2
95.2
96.1
95.0
97.1
99.0
97.0
95.1
90.9
94.9
98.0
96.0
96.0
97.0
98.9
96.9
100.0
100.0
98.9
95.9
30%
96.2
98.1
99.0
96.2
98.1
99.0
98.0
98.0
99.0
99.0
97.0
99.0
96.0
99.0
99.0
97.0
99.0
100.0
98.9
98.9
100.0
100.0
98.9
100.0
50%
98.1
99.0
99.0
98.1
100.0
99.0
98.0
98.0
99.0
99.0
98.0
99.0
98.0
100.0
99.0
99.0
100.0
100.0
98.9
98.6
100.0
100.0
98.9
100.0
29
-------
TABLE 20. AUDIT RESULTS FOR SULFUR DIOXIDE CONTINUOUS MONITORS (ALL DATA)
Flow
setting
1
2
3
4
5
6
Number of
reported
values*
29
216
219
220
220
156
Range of
values (ppm)
0.577 to 0.702
0.377 to 0.513
0.200 to 0.270
0.151 to 0.206
0.040 to 0.073
0.000
Mean
ppm
0.004
0.006
0.004
0.003
0.002
0.001
differences
% diff.
0.4
1.6
1.7
2.0
3.2
MM
Standard
deviation
(ppm)
0.066
0.033
0.016
0.013
0.006
0.003
*1984 Audit: Data returned for 221 monitors
TABLE 21. AUDIT RESULTS FOR SULFUR DIOXIDE CONTINUOUS MONITORS
BY VARIOUS INSTRUMENTAL METHODS
Flame ^photometric
Flow average difference
setting n
1 0
2 8
3 8
4 8
5 8
6 7
ppm
0.008
0.010
0.008
0.003
0.002
%
2.0
4.6
5.0
6.0
— — *•
Fluorescent
average difference
n
28
201
203
204
204
145
ppm
0.003
0.006
0.003
0.003
0.002
0.001
%
0.3
1.5
1.5
1.8
3.2
___
Coulometric
average difference
n
0
4
5
5
5
2
ppm
-0.000
0.004
0.003
0.000
0.000
%
0.1
1.7
1.5
-0.6
—
30
-------
TABLE 22. AUDIT RESULTS FOR HIGH-VOLUME FLOW RATE
Results within indicated
No. of % of assigned value
Method results 20% 40% 60% 80%"
Rotameter (visifloat) 12331 1.59 3.11 5.28 8.42
Pressure transducer (continuous) 24282 1.08 2.37 3.87 6.25
Flow controller 1693 0.71 1.44 2.55 3.66
Pressure transducer/flow controller 2361* 1.63 3.18 4.65 6.82
Other methods 8365 1.96 3.63 5.24 7.85
All methods 48676 1.30 2.71 4.37 6.85
measurements reported
22594 measurements reported
3 183 measurements reported
4 240 measurements reported
5 902 measurements reported
^5236 measurements reported
TABLE 23. PERCENTAGE OF HI-VOL FLOW MEASUREMENTS WITHIN INDICATED
PERCENTAGE OF ASSIGNED VALUE (ALL DATA)
Plate
number
5
7
10
13
18
Number of
measurements
776
891
1036
1011
1013
Approximate
flow (m3/min)
0.7
0.9
1.1
1.2
1.3
10%
73.1
84.2
87.8
90.0
91.2
20%
89.3
95.4
96.2
97.4
97.2
30%
95.1
97.2
98.4
98.6
98.8
50%
98.7
98.0
99.3
99.6
98.9
31
-------
TABLE 24. ACID RAIN RESULTS FOR pH, CONDUCTIVITY AND ACIDITY (ALL DATA)
Audit
0484 pH
Conductivity
(yS/cm)
Acidity
(yequiv/L)
1084 pH
Conductivity
(pS/cm)
Acidity
(yequiv/L)
Level
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
n
36
36
36
32
32
32
20
20
20
32
32
32
29
29
29
16
16
16
Assigned
value
4.28
4.01
3.55
24.00
50.70
136.20
52.80
102.00
304.40
4.28
3.88
3.73
24.40
66.00
92.70
53.10
137.20
197.00
Mean
4.27
3.98
3.54
22.51
49.51
124.63
51.29
95.17
261.46
4.24
3.86
3.711
37.35
86.50
90.92
74.76
157.05
217.05
% Ace.
-0.23
-0.75
-0.28
-6.21
-2.35
-8.49
-2.86
-6.70
-14.11
-0.93
-0.52
-0.54
53.07
31.06
-1.92
40.79
14.47
10.18
% CV
4.23
3.92
2.94
22.03
30.67
10.82
54.59
51.67
48.23
5.51
4.53
3.93
202.29
124.90
9.30
35.52
16.31
12.59
32
-------
TABLE 25. ACID RAIN RESULTS FOR pH, CONDUCTIVITY AND ACIDITY
(OUTLIERS REMOVED)
Audit
0484 pH
Conductivity
(l-iS/cm)
Acidity
(laequiv/L)
1084 pH
Conductivity
(yS/cm)
Acidity
(pequiv/L)
Level
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
n
34
34
34
30
31
31
20
20
20
30
30
30
28
28
28
16
15
15
Assigned
value
4.28
4.01
3.55
24.00
50.70
136.20
52.80
102.00
304.40
4.28
3.88
3.73
24.40
66.00
92.70
53.10
137.20
197.00
Mean
4.27
3.98
3.54
22.33
47.00
126.51
51.29
95.17
201.46
4.30
3.90
3.75
23.33
66.73
89.89
74.76
152.19
212.99
% Ace.
-0.23
-0.75
-0.28
-6.96
-7.30
-7.11
-2.86
-6.70
-33.80
0.47
0.52
0.54
-4.39
1.11
-3.03
40.79
10.83
8.12
% CV
4.23
3.12
1.81
10.47
11.47
6.68
54.59
51.67
48.23
1.39
1.13
1.07
10.93
28.25
7.22
35.52
11.33
10.68
33
-------
TABLE 26. ACID RAIN AUDIT RESULTS FOR ANIONS (ALL DATA)
Audit Level
0484 804 (reported 1
as S) 2
3
N03 (reported 1
as N) 2
3
Cl 1
2
3
F 1
2
3
1084 804 (reported 1
as S) 2
3
N03 (reported 1
as N) 2
3
Cl 1
2
3
F 1
2
3
Assigned
n value (mg/1)
28
32
32
30
30
30
29
29
29
22
22
22
29
29
29
28
28
28
29
29
29
21
21
21
0.81
2.11
3.68
0.11
0.11
1.55
0.28
0.41
1.26
0.04
0.08
0.25
0.87
2.75
3.68
0.12
0.12
0.14
0.29
0.63
0.92
0.03
0.09
0.26
Mean
(mg/1)
0.86
2.43
3.87
0.12
0.16
1.47
0.32
0.42
1.18
0.05
0.08
0.26
1.03
3.11
4.21
0.11
0.12
0.14
0.46
0.91
1.14
0.04
0.08
0.26
% Ace.
6.17
15.17
5.16
9.09
45.45
-5.16
14.29
2.44
-6.35
25.00
0.00
4.00
18.39
13.09
14.40
-8.33
0.00
0.00
58.62
44.44
23.91
33.33
-11.11
0.00
% CV
40.67
43.32
33.70
20.69
128.57
25.34
54.11
56.77
22.93
51.11
44.87
14.06
65.53
41.77
38.55
26.79
21.01
21.48
191.32
191.79
100.88
68.42
30.95
13.36
34
-------
TABLE 27. ACID RAIN AUDIT RESULTS FOR ANIONS (OUTLIERS REMOVED)
Audit Level
0484 804 (reported 1
as S) 2
3
N03 (reported 1
as N) 2
3
Cl 1
2
3
F 1
2
3
1084 804 (reported 1
as S) 2
3
N03 (reported 1
as N) 2
3
Cl 1
2
3
F 1
2
3
n
27
30
30
29
29
29
28
28
27
21
22
21
27
27
27
26
27
27
28
28
28
20
20
20
Assigned
value (mg/1)
0.81
2.11
3.68
0.11
0.11
1.55
0.28
0.41
1.26
0.04
0.08
0.25
0.87
2.75
3.68
0.12
0.12
0.14
0.29
0.63
0.92
0.03
0.09
0.26
Mean
(mg/1)
0.80
2.20
3.57
0.11
0.12
1.52
0.29
0.38
1.19
0.04
0.08
0.26
0.87
2.76
3.78
0.12
0.12
0.14
0.30
0.59
0.93
0.03
0.09
0.27
% Ace.
-1.23
4.27
-2.99
0.00
9.09
-1.94
3.57
-7.52
-5.56
0.00
0.00
4.00
0.00
0.36
2.72
0.00
0.00
0.00
3.45
-6.35
1.09
0.00
0.00
3.85
% CV
15.60
24.09
15.85
17.54
24.19
23.10
38.36
31.67
17.30
46.51
44.87
8.81
33.45
5.93
6.51
11.76
12.20
12.14
42.47
24.79
25.97
61.76
20.45
11.28
35
-------
TABLE 28. AGIO RAIN RESULTS FOR CATIONS (ALL DATA)
Audit Level
0484 NH4 (reported 1
as N) 2
3
Ca 1
2
3
K 1
2
3
Mg 1
2
3
Na 1
2
3
1084 NH4 (reported 1
as N) 2
3
Ca 1
2
3
K 1
2
3
Mg 1
2
3
Na 1
2
3
n
27
27
27
25
25
25
24
24
24
24
23
25
26
26
26
27
27
27
26
26
26
26
26
26
25
.25
25
26
26
26
Assigned
value (mg/1)
0.08
0.63
0.80
0.06
0.01
0.12
0.07
0.09
0.09
0.02
0.01
0.04
0.19
0.24
0.49
0.08
0.61
0.79
0.05
0.13
0.01
0.07
0.08
0.10
0.02
0.01
0.04
0.19
0.25
0.49
Mean
(mg/1)
0.38
0.64
0.84
0.06
0.03
0.11
0.08
0.07
0.10
0.02
0.01
0.04
0.26
0.35
0.55
0.08
0.63
0.81
0.10
0.17
0.05
0.09
0.09
0.12
0.02
0.01
0.04
0.18
0.27
0.49
% Ace.
375.00
1.59
5.00
0.00
200.00
-8.33
14.29
-22.22
11.11
0.00
0.00
0.00
36.84
45.83
12.24
0.00
3.28
2.53
100.00
30.77
400.00
28.57
12.50
20.00
0.00
0.00
0.00
-5.26
8.00
0.00
% CV
396.82
15.43
15.67
46.77
126.47
24.78
35.80
34.38
53.54
28.57
135.71
33.33
99.61
91.09
51.00
35.44
15.77
14.96
139.60
52.30
242.59
113.19
26.60
77.50
47.37
75.00
36.84
28.80
51.28
27.85
36
-------
TABLE 29. ACID RAIN AUDIT RESULTS FOR CATIONS (OUTLIERS REMOVED)
Audit Level
0484 NH4 (reported 1
as N) 2
3
Ca 1
2
3
K 1
2
3
Mg 1
2
3
Na 1
2
3
1084 NH4 (reported 1
as N) 2
3
Ca 1
2
3
K 1
2
3
Mg 1
2
3
Na 1
2
3
n
26
25
25
23
23
24
23
23
23
23
22
24
25
25
24
26
25
25
25
25
25
25
24
25
25
24
23
25
25
25
Assigned
value (mg/1)
0.08
0.63
0.80
0.06
0.01
0.12
0.07
0.09
0.09
0.02
0.01
0.04
0.19
0.24
0.49
0.08
0.61
0.79
0.05
0.13
0.01
0.07
0.08
0.10
0.02
0.01
0.04
0.19
0.25
0.49
Mean
(mg/1)
0.09
0.63
0.84
0.05
0.02
0.11
0.08
0.10
0.09
0.02
0.01
0.04
0.22
0.30
0.48
0.08
0.63
0.81
0.08
0.17
0.03
0.07
0.09
0.10
0.02
0.01
0.04
0.18
0.25
0.47
% Ace.
12.51
0.00
5.00
16.70
100.00
-8.30
14.30
11.10
0.00
0.00
0.00
0.00
15.80
25.00
-2.04
0.00
3.20
2.53
60.00
30.80
200.00
11.40
12.50
0.00
0.00
0.00
0.00
-5.26
0.00
-4.08
% CV
49.44
8.52
9.81
16.67
86.96
19.27
26.32
27.00
39.56
25.00
40.00
20.51
73.73
68.00
14.32
28.05
8.37
8.61
100.00
48.48
174.19
38.03
19.35
25.24
47.37
70.00
19.51
17.71
26.61
19.11
37
-------
TABLE 30. ACID RAIN AUDIT RESULTS FOR TRACE METALS (ALL DATA)
Audit
0484 Mn
Fe
Cd
Cu
Ni
Pb
Zn
1084 Mn
Fe
Cd
Cu
Ni
Pb
Zn
Level
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
n
17
19
17
17
17
17
17
17
15
16
16
18
17
17
12
12
11
11
12
12
12
12
11
11
12
12
12
12
Assigned
value (mg/1)
0.05
0.10
0.05
0.12
0.03
0.11
0.05
0.16
0.03
0.10
0.11
0.31
0.11
0.72
0.05
0.10
0.06
0.13
0.04
0.16
0.06
0.30
0.07
0.07
0.12
0.23
0.10
0.85
Mean
(mg/1)
0.05
0.10
0.05
0.12
0.03
0.10
0.05
0.15
0.04
0.10
0.10
0.31
0.10
0.71
0.06
0.10
0.05
0.12
0.03
0.15
0.05
0.30
0.07
0.06
0.10
0.20
0.11
0.87
% Ace.
0.00
0.00
0.00
0.00
0.00
-9.09
0.00
-6.25
33.33
0.00
-9.09
0.00
-9.09
-1.39
20.00
0.00
-16.67
-7.69
-25.00
-6.25
-16.67
0.00
0.00
-14.29
-16.67
-13.04
10.00
2.35
% CV
8.16
12.24
14.00
10.08
16.67
17.53
29.41
10.39
59.46
47.52
7.07
12.34
11.76
4.40
28.81
8.16
74.51
20.97
37.50
12.84
34.00
6.42
41.54
33.90
48.96
48.98
20.00
8.62
38
-------
TABLE 31. ACID RAIN AUDIT RESULTS FOR TRACE METALS (OUTLIERS REMOVED)
Audit
0484 Mn
Fe
Cd
Cu
Ni
Pb
Zn
1084 Mn
Fe
Cd
Cu
Ni
Pb
Zn
Level
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
4
5
n
15
18
16
16
16
16
16
16
14
15
15
16
16
16
11
11
10
11
11
11
11
11
10
10
12
12
11
11
Assigned
value (mg/1)
0.05
0.10
0.05
0.12
0.03
0.11
0.05
0.16
0.03
0.10
0.11
0.31
0.11
0.72
0.05
0.10
0.06
0.13
0.04
0.16
0.06
0.30
0.07
0.07
0.12
0.23
0.10
0.85
Mean
(mg/1)
0.05
0.10
0.04
0.12
0.03
0.09
0.05
0.15
0.03
0.09
0.10
0.30
0.10
0.71
0.06
0.10
0.04
0.12
0.04
0.15
0.06
0.29
0.07
0.06
0.10
0.20
0.10
0.85
% Ace.
0.00
0.00
-20.00
0.00
0.00
-18.18
0.00
-6.25
0.00
-10.00
-9.09
-3.23
-9.09
-1.39
20.00
0.00
-33.33
-7.69
0.00
-6.25
0.00
-3.33
0.00
-14.29
-16.67
-13.04
0.00
0.00
% CV
4.00
5.00
12.24
6.61
6.90
7.53
14.58
7.10
42.42
29.67
4.95
5.07
5.77
3.38
20.00
6.00
48.78
20.97
17.14
7.84
12.73
4.45
23.94
20.31
48.90
48.98
12.00
5.98
39
-------
Ofr
AVERAGE ACCURACY, pircint
AVERAGE ACCURACY. pi>c
-------
>BASED ON MEAN VALUE
IBASED ON MEDIAN VALUE
04/83 11/83 04/84 10/3
ACCURACY
I I I L
04,B3 11 83 04 84 10/84
PRECISION
Figure 11 Acid rain audit results for NO3 (reported as N)
•BASED ON MEAN VALUE
•BASED ON MEDIAN VALUE
11/83 04/84 10/84
ACCURACY
i 50
3 -.
J i I I
11 83 04 84 10.84
PRECISION
Figure 1 2 Acid rain audit results for Cl
41
-------
§10
•BASED ON MEAN VALUE
»BASED ON MEDIAN VALUE
j I
04/83 11 83 04 84 10'84
ACCURACY
J I I I
04 83 11 83 04 84 10 84
PRECISION
Figure 9 Acid ram audit results for acidity
--•BASED ON MEAN VALUE
-•BASED ON MEDIAN VALUE
I I I I
04/83 11/83 04.84 10 84
ACCURACY
J I I I
04 83 11 83 04 84 10 84
PRECISION
Figure 10 Acid ram audit results for SOA (reported as S)
42
-------
• •BASED ON MEAN VALUE
• »BASED ON MEDIAN VALUE
04/83 11/B3 04/84 10/84
ACCURACY
04 83 11 83 04 84 10 84
PRECISION
Figure 7 Acid ram audit results for pH
S o .
•BASED ON MEAN VALUE
•BASED ON MEDIAN VALUE
04 83 11 83 04 84 10 84
ACCURACY
_] 1 \ 1
04/83 11/83 04/B4 10/84
PRECISION
Figure 8 Acid rain audit results for conductivity
43
-------
50rn—rn—\
02/77 01/77 02/71 00/71 02/79 OB/79 02/81 00/80 02/81 08/81 02/02 08/12 02/13 01/83 02/84 08/84
AUDIT DATE, month/yoi
ACCURACY
10/78 02/77 08/77 02/78 01/78 02/79 08/70 02/10 01/10 02/lt 01/11 02/12 01/12 02/13 00/83 02/84 08/84
AUDIT DATE, montii/yur
PRECISION
Figure 5. Nitrate audits.
10
08/77
01/71 06/71 01/79 07/79 01/10 07/10 01/11 07/81 01/12 07/12 01/83 07/83 01/84 07/04
AUDIT DATE, month/yew
ACCURACY
01/77 01/78 07/78 01/79 07/79 01/10 07/80 01/11 07/11 01/82 07/12 01/13 07/13 01/84 07/84
AUDIT DATE, month/year
PRECISION
Figure 6. Lead audits.
-------
I I I
I I I
I I I I
10/79 03/77 09/77 03/78 09/79 03/79 09/79 03/90 09/80 03/81 09/91 03/92 09/82 OS/93 10/93 04/84
AUDIT DATE, month/yur
ACCURACY
I-
£20 —
10/76 03/77 09/77 03/76 09/7S 03/79 09/79 03/80 09/10 03/91 09/11 03/92 09/92 05/13 10/93 04/94
AUDIT DATE, moMh/ynr
PRECISION
Figures. Carbon monoxide audits.
en
10/71 02/77 09/77 02/79 08/79 02/79 08/79 02/90 08/89 02/81 08/81 02/82 08/82 02/83 09/93 02/94 08/94
AUDIT DATE, month/ynr
ACCURACY
10/79 02/77 08/77 02/78 08/78 02/7> 08/79 02/80 09/80 02/81 08/81 02/82 09/82 02/83 08/83 02/84 08/84
AUDIT DATE, mooth/yui
PRECISION
Figure 4. Sulfate audits.
-------
• 0BASED ON MEAN VALUE
•—•BASED ON MEDIAN VALUE
I 20
g
3 '«
:
S o
04/83 11/83 04 84 10.84
ACCURACY
04/83 11/83 04/84 10/84
PRECISION
Figure 13 Acid rain audit results for F
S o.
•BASED ON MEAN VALUE
ABASED ON MEDIAN VALUE
I i
04/83 11/83 04/84 10/84
ACCURACY
I I I I
04/83 11/83 04/84 10/84
PRECISION
Figure 14. Acid rain audit results for NH4 (reported as N).
46
-------
AVERAGE ACCURACY, percam
to
c
m
5
o>
c
0.
AVERAGE CV. percent
i £
I
I
ss
tn to
m m
O D
O O
m m
D >
z <
c
m
Tl
CQ
C
S
ffi
C
O.
o
o
—I—
II
CD CD
tn to
m m
D O
O O
Z Z
m m
O >
Z <
M
c m
m
AVERAGE CV. parcai
-------
—-•BASED ON MEAN VALUE
•BASED ON MEDIAN VALUE
J I
11"83 04/84 10/84
ACCURACY
E
150
s
!
04 83 11 83 0», 94 10 84
PRECISION
Figure 17 Acid ram audit results for Mg.
I o
•BASED ON MEAN VALUE
»BASED ON MEDIAN VALUE
j i i i ,
14/83 11/83 04/84 10/84
ACCURACY
S 40
I I I I
04/83 11/83 04/84 10/84
PRECISION
Figure 18. Acid rain audit results for Na
48
-------
§ 20
I
"
g
I
> o
•BASED ON MEAN VALUE
•BASED ON MEDIAN VALUE
04/83 11'83 04/94 10/84
ACCURACY
04/83 11/83 04/84 10/84
PRECISION
Figure 19 Acid ram audit results for Mn
§10
•BASED ON MEAN VALUE
•BASED ON MEDIAN VALUE
J I I I
04/83 11/83 04/84
ACCURACY
04/83 11/83 04/84 10/84
PRECISION
Figure 20 Acid rain audit results for Fe
49
-------
i 20
I
-••BASED ON MEAN VALUE
-•BASED ON MEDIAN VALUE
11 -83 04/84 10 84
ACCURACY
£ 40
04 83 11 83 04 84 10 84
PRECISION
Figure 21. Acid rain audit results for Cd.
S
B o
•BASED ON MEAN VALUE
•BASED ON MEDIAN VALUE
11/83 04/84 10/84
ACCURACY
5 40
11/83 04/84
PRECISION
Figure 22. Acid rain audit results for Ca
50
-------
S o
• BASED ON MEAN VALUE
•BASED ON MEDIAN VALUE
11/83 04/84
ACCURACY
11/B3 04
PRECISION
Figure 23. Acid ram audit results for Ni.
• BASED ON MEAN VALUE
ABASED ON MEDIAN VALUE
04 «3 11
S3 D4 84 10 84
ACCURACY
04/83 11/83 04/84 10-84
PRECISION
Figure 24. Acid rain audit results for Pb.
51
-------
• BASED ON MEAN VALUE
>BASED ON MEDIAN VALUE
S «o
04/83 11/83 04/84 10/84
ACCURACY
04/83
11/83 04/84 10/84
PRECISION
Figure 25. Acid rain audit results for Zn.
S GOVERNMENT PRINTING OFFICE 1986 - 646-116/20773
52
------- |