United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-90/028 May 1990
&EPA Project Summary
Analysis of Acid Precipitation
Samples Collected by State
Agencies: 1988
Lloyd S. Shepard
This report presents analytical
data from the 30 acid precipitation
collection sites in the State-Operated
Network. Samples are collected
weekly in plastic bag liners and
shipped in 500 mL polyethylene
bottles to Global Geochemistry Cor-
poration (the central laboratory for
the network). The report contains
maps showing the location of each
site, plots of analytical data, tables of
all field and analytical data, plots
comparing field and laboratory pH
and conductivity, and information on
data quality. Samples are analyzed
for pH, strong acid, conductivity,
fluoride, chloride, nitrite, phosphate,
bromide nitrate, sulfate, ammonium,
sodium, potassium, calcium, and
magnesium. The central laboratory
renders technical assistance to the
collection sites on problems con-
cerning pH and conductivity. Each of
the 11 participating state agencies
receives analytical reports for the
samples analyzed the previous
month. Analyte concentration data
are sent to the Acid Deposition
System (ADS) for inclusion in the
National Acid Precipitation Data
Base.
This Project Summary was devel-
oped by EPA's Atmospheric Research
and Exposure Assessment Laboratory,
Research Triangle Park, NC, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
As the central laboratory for the State-
Operated Network, Global Geochemistry
Corporation (GGC) analyzes acid pre-
cipitation samples for pH, strong acid,
conductivity, fluoride, chloride, nitrite,
phosphate, bromide, nitrate, sulfate,
ammonium, sodium, potassium, calcium,
and magnesium. The central laboratory
provides the collection sites with plastic
bucket liners, 500 mL sample bottles,
field data sheets, pH and conductivity
solutions, and other supplies incidental to
collecting and shipping a collected rain
sample. The central laboratory also
provides technical assistance whenever it
is requested by the field sites. This
assistance has consisted mostly of ad-
vice on field pH and conductivity mea-
surement procedures and equipment.
The report contains maps showing the
location of each site, plots of analytical
data during the time period, tables of all
field and analytical data, a comparison of
analyte concentrations at all sites (fre-
quency of occurrence), precipitation
weighted data for each site, plots com-
paring field and laboratory pH and
conductivity, and quality control tables
and plots. Each participating state agen-
cy and sponsoring EPA region receives a
monthly report of analytical data. Data
are summarized on magnetic tape for in-
clusion in the yearly report of the national
acid rain data base, the Acid Deposition
System (ADS), funded by EPA.
Network Description
There were 30 acid rain collection
sites in operation during most of 1988.
-------
Table 1.
pH and Conductivity-Field vs. Laboratory
pH
Kygra pH Field - pH Lab vs Time
i
48.00
o
O
Conductivity
Kygra Cond Field - Cond Lab vs Time
ID Number (Time)
0.00 12.00 24.00 36.00
ID Number (Time) (X10)
48.00
The State-Operated Network collects
weekly samples using a wet/dry bucket
collector. Samples are collected in a
plastic bag bucket liner, and an aliquot is
sent to the central laboratory unrefrig-
erated in a 500 ml polyethylene bottle.
The following analytes are measured:
pH, conductivity, strong acidity, chloride,
sulfate, phosphate, nitrate, ammonium,
sodium, potassium, calcium, and magne-
sium. Plots are presented in the main
report showing the weekly concentration
of each analyte throughout the year. The
amount of precipitation is given for each
weekly collection period. Each site
conducts field measurements for pH and
conductivity. Representative plots are
presented for a single site in Table 1 for
all samples analyzed since 1983.
Once every two months the central
laboratory sends each collection site
replacement supplies, including 500 ml
of pH reference solution and 500 ml of
conductivity reference solution. Sites are
instructed to measure the reference
materials in the same way as a sample.
This procedure provides the sites with
on-going quality assurance self-checks of
the accuracy of their measurements.
The analytical methods used by the
central laboratory are shown below in
Table 2.
The occurrence of different
concentration levels at each site are
given in the main report. The concentra-
tions greater than the given values are
listed for each site and for each analyte.
This is illustrated in Table 3 for pH
Table 2
Analyte
Analytical Method
pH EPA Method 150.1
Conductivity EPA Method 120.1
Acidity Gran Titration
Cl', PO4-3, SO4-2, N03 Ion Chromatography
NH4 + EPA Method 350.1
Na+, K + , Ca*-2, Mg+2 EPA Methods 273.1,
258.1, 215.1, 242.1
Performance Evaluation
Surveys (Audits) of Field pH
and Conductivity
Performance evaluations of the field
pH and conductivity measurements were
done in March and in September 1988.
The results of these evaluations are
shown in Table 4. Overall, the mean
values reported for both evaluations
agreed very well with the expected
values. However, it was noted that in the
September 1988 audit, 32% of the 22
participants reported a pH value that
differed from the target value by more
than 0.10 pH units. This compares to only
three (12%) of the 24 participants
exceeding this value for the March audit.
Two of these three participants exceeded
the target value in both audits.
Quality Control
To validate the accuracy of routine
analytical procedures, the central
laboratory included duplicate and spike
samples with all analyses. The duplicate
samples were randomly chosen acid rain
samples. Spike samples were prepared
from stock solutions and were unknown
to the analyst. Quality control plots for all
analytes are presented in Appendix A of
the main report.
-------
Table 3.
Site
ALMOB
ALTAL
DEGEO
DELUM
GABFG
GADAW
GADUF
GAHIW
GASUM
GAWAY
KYGRA
KYMAN
LACAR
LACHS
LAHOM
LAROS
MD3EC
MDRGP
MSUNI
SCCAP
SCCON
SCDEL
SCLON
SDAPR
SDBPR
SDCUS
TNCEN
WVAPC
WVGRN
WVNEW
Table 4
Date
Cumulative Frequency of Occurrence: pH
% of Samples
#PTS
36
28
44
36
23
34
77
21
36
28
38
36
24
38
10
42
39
37
35
31
37
34
36
3
3
17
30
21
14
22
100%
3.97
4.00
3.25
3.73
3.67
3.43
4.07
3.84
3.63
3.70
3.29
3.65
4.33
3.78
4.76
4.07
3.54
3.27
3.56
3.67
3.62
3.47
3.84
4.98
4.96
4.98
3.79
3.82
4.02
3.50
75%
4.29
4.24
4.77
4.04
4.23
4.27
4.47
4.72
4,72
4.44
4.00
4.24
4,72
4.38
4.29
4.47
4.02
3.99
4.43
4.37
4.73
4.79
4.77
3.74
3.72
5.76
4.27
4.08
4.27
3.82
Greater than Given Value
50%
4.55
4.56
4.40
4.77
4.46
437
4.62
4.39
4.27
4.70
4.22
4.47
5.72
4.67
4.44
4.72
4.22
4.29
4.67
4.49
4.40
4.37
4.37
5.69
5.64
5.67
4 46
4.24
4 42
3.97
Summary of Survey of pH and Conductivity Accuracy
Survey Averages
pH
Std. Dev.
Conductivity
Std. Dev.
25%
4.76
4.82
4.63
4.46
4.62
4.60
4.73
4.58
4.50
4.87
4.46
4.52
5.56
4.90
4.87
4.97
4.47
4.45
4.76
4.66
4.62
4.47
4.55
6.39
6.33
5.98
4.62
4.37
4.57
4.74
0%
4.93
5.77
5.66
5.25
4.98
5.36
5.58
4.87
5.04
554
5.79
4.87
5.99
5.27
5.02
5.37
6.23
6.48
5.33
5.84
5.70
5.76
4.79
6.39
6.35
6.79
4.86
4.56
4.77
4.60
Expected Values
pH
Conductivity
March 1988
Oct. 1988
4.24
4.26
37.6
38.1
2.2
3.4
4.28
4.23
37.4
38.1
-------
Lloyd S. Shepard is with Global Geochemistry Corporation, Canoga Park, CA
91303-2194
Berne I. Bennett is the EPA Project Officer (see below).
The complete report, entitled "Analysis of Acid Precipitation Samples Collected
by State Agencies: 1983," (Order No. PB 90-191-7841 AS; Cost: $31.00,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-90/028
------- |