United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/S3-90/040
Aug. 1990
&EPA Project Summary
Summary Report for the
National Atmospheric
Deposition Program/National
Trends Network (NADP/NTN)
Site Visitation Program for the
Period October 1987 through
September 1988
W. C. Eaton, C. E. Moore, R. W. Murdoch, R. C. Shores, and D. A.
Ward
The proper collection of precipitation
and the accurate measurement of its
constituents are important steps in
attaining a better understanding of the
distribution and effects of "acid rain" in
the United States. One of NAPAP Task
Group IV's major programs concerns wet
deposition monitoring. One of that pro-
gram's projects, 4A-15, "Quality Assur-
ance Support for Wet Deposition Mon-
itoring," is sponsored by the U.S.
Environmental Protection Agency (EPA)
to evaluate the sample collection process
and provide technical assistance to the
NADP/NTN network through a site
visitation program. Research Triangle
Institute, as contractor to EPA, conducts
these visits. If deficiencies or nonstand-
ard procedures are noted, the site
operator and supervisor are notified. Brief
reports are sent to the EPA Project
Officer, the NADP/NTN Quality Assur-
ance Manager, and others. In this way,
necessary changes can be made
promptly.
All NADP/NTN sites were visited in
1985-1986. A second round of visits
began in October 1986, with the goal of
visiting approximately one-third of the
200 sites each year over the next three
years. This document is a summary report
of the findings from the 1987-1988 (Fiscal
Year 1988) site visitation program to 57
of the sites of the NADP/NTN network.
In its present configuration, the network's
research and monitoring programs are
supported and operated by the U.S.
Geological Survey; State Agricultural
Experiment Stations; the Departments of
Agriculture, the Interior, Commerce, and
Energy; and EPA. Additional support is
provided by state agencies, public
utilities, and industries.
Protocols and procedures followed in
conducting the site visits are described.
Results of systems and performance
audits are discussed for siting, collection
equipment, and the field support labor-
atories. Where exceptions are found, the
potential effects of nonstandard siting,
improperly operating equipment, and
improper sample handling or analysis
technique on the database are dis-
cussed.
This report was submitted in partial
fulfillment of EPA Contract No. 68-D8-
0001 by Research Triangle Institute. This
report covers site visits made during the
period October 1, 1987, through Sep-
tember 30,1988. All work was completed
as of September 30,1988.
This Project Summary was developed
by EPA's Atmospheric Research and
Exposure Assessment Laboratory,
Research Triangle Park, NC, to announce
key findings of the research project that
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Is fully documented In a separate report
of the same title. (See Project Report
ordering Information at back).
Introduction
The main report summarizes quality
assurance assistance and findings from
site visits made to the National Atmo-
spheric Deposition Program/National
Trends Network (NADP/NTN) precipita-
tion collection stations for the period
October 1987 through September 1988.
Each site is located and operated accord-
ing to protocols and procedures as given
in the siting and operating manuals for
the networks. The purposes of the site
visitation program, sponsored by the U.S.
Environmental Protection Agency (EPA),
are to verify that each site is operating
within control limits and according to
established procedures, and to provide
technical assistance as required.
Fifty-seven of the 196 sites that were
in operation as of January 15,1989, were
visited during this time frame. Figure 1
shows the NADP/NTN site locations.
Goals of the Site Visitation Program
The goals of the site visitation program
for quality assurance assistance to the
NADP/NTN collection sites are as
follows:
1. Provide a qualitative assessment of
each site and its surroundings, the
operator's adherence to sample col-
lection and analysis procedures, and
the condition of the site's collection and
analysis equipment through an on-site
systems survey;
2. Provide a quantitative assessment of
the operation of the precipitation
collector and the accuracy of response
of field and laboratory measurement
devices for precipitation depth, mass,
temperature, conductivity, and pH
through, an on-site performance
survey;
3. Provide technical assistance to the
opierator by verbal explanation, minor
troubleshooting, repair and calibration
of equipment, and by making recom-
mendations for sources of corrective
action;
4. Prepare brief reports for each site
detailing site characteristics, results of
quality assurance tests, and technical
assistance provided. Submit the
reports to the NADP/NTN Quality
Assurance Manager, the Central Ana-
lytical Laboratory's Site Liaison, and
the EPA Project Officer;
5. Computerize results of all information
gathered from each site and submit this
to the NADP/NTN Quality Assurance
Manager on an annual basis;
6. Document the sites and their surround-
ings by assembling a collection of site
maps and color photographs.
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Figure 1. Location of active sites in the NADP/NTN network as of August 1989.
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Conclusions
Fifty-seven of the 196 active NADP/
NTN precipitation collection sites were
visited over the one-year period, October
1987 through September 1988. About
one-third of the sites were visited during
this second year of a three-year effort.
The sites are located in all regions of the
country and are sponsored and operated
by numerous agencies. Each site is
located according to established siting
criteria and operates according to pub-
lished procedures. This report assesses
the degree to which criteria and proce-
dures are adhered to; predicts, where
possible, the relative impact on the data
that might be expected from the variances
found; and compares results thus far from
the second round of visits to those docu-
mented in the first round of visits that
occurred over the period December 1984
through September 1986.
Siting
Improvements in adherence to siting
criteria were noted at most of the sites
visited in 1988 that were not in compliance
at the time of the first round of visits in
1985-1986. A number of sites had sepa-
rated the collector and rain gauge to the
prescribed 5-m distance and had oriented
the collector's wet-side bucket to the
west. Obstructions and sources of dust
such as animals, parking lots, and chem-
ical storage areas had been removed, or
the site's equipment had been moved
away from them.
For the 13 siting criteria summarized
in this report, 41 of 57 sites (72%) visited
in FY 1988 had at least one variance.
Twenty-five percent of the sites had three
or more variances. However, most of the
variances are expected to have minimal
effects on the database because of the
nature of certain criteria and/or the
degree to which the criteria were
exceeded. For example, network siting
criteria require that the precipitation
collector and rain gauge be separated by
at least 5 m but not more than 30 m.
Twenty-six percent of the 57 sites did not
meet this criterion, always because of
inadequate separation.
Sample Collection
Designated sample collection proce-
dures were adhered to at almost all the
sites in the network. All operators were
careful not to touch the inside of the
collection bucket or lid or contaminate the
sample in any' way. All site operators
stated that they checked the sample for
contaminants (leaves, bird droppings,
etc.) at the time of the bucket's removal
from the collector. This procedure was not
being well adhered to at the time of the
first round of visits.
To ensure accurate precipitation data,
it is most important that the precipitation
collector and rain gauge are properly
working and well-maintained. Only two
sites were unable to make a weekly equip-
ment check. A properly working precip-
itation collector should uncover the wet
bucket at the beginning of a precipitation
event and recover the wet bucket shortly
after the event stops to keep matter such
as dust out of the wet bucket when there
is no precipitation. There were indications
at 13 of 57 sites (23% of the total) that
the clutch on the Aerochem Metrics
precipitation collector was wearing;
however, only 2 of these 13 failed to
operate properly when tested with a 1600-
g load. Only 2 of 55 sensors checked were
not operating properly. Fifty-two percent
of the rain gauges (29 of 56) were found
to be out of calibration by more than ±0.1
in. at some point on the 0-12-in. scale.
This is not believed to be a major source
of error because the calibration errors
usually occurred at a depth of 5 in. or
more, and the operator is instructed to
empty the catch bucket before this depth
is reached. Calibration checks showed
that 48 of the 56 gauges (86%) met
acceptable calibration criteria (±0.1 in.)
over the range of 0 to 5 in.
Field Laboratory Procedures
Field laboratory procedures for sample
handling, conductivity measurements,
and pH determinations were being carried
out properly and accurately in almost all
cases. Proper procedures were dis-
cussed or demonstrated to site operators
as needed.
Results were improved over those
noted at the time of the first round of visits.
For example, all but three sites were able
to determine the pH to within ±0.1 unit
of the designated value. Two sites had
inoperative pH meters and could not be
checked. All six of the sites that were
outside of tolerance for pH measurements
in Round 1 were within tolerance in
Round 2. Overall, 95% of the 55 field
laboratories checked in 1988 agreed
within ±0.1 pH unit with the audit solu-
tion's designated value.
For conductivity measurements, each
of the 53 sites checked (100%) determined
the audit solution's conductivity to within
±4 juS/cm of the designated value. Four
sites had exceeded the limit of agreement
during Round 1 visits. Four sites had
malfunctioning or broken equipment and
thus could not be audited.
The solution balances were operating
properly in all of the 56 cases checked.
Of 56 balances checked, more than half
agreed within ±1 g with the designated
weight over the range of 823 to 4043 g.
All but one balance agreed within ±5 g
with the designated weight over the same
range. In terms of percent variation with
respect to weight, the worst case for the
55 balances that operated within ±5 g
agreement would be ±0.6% at a loading
of 823 g and ±0.1 % at a loading of 4043 g.
Recommendations
The site precipitation collector and rain
gauge,are central to the successful
operation of the network. However, the
equipment in the NADP/NTN network is
aging and will require increased main-
tenance. Therefore, weekly equipment
checks by the operator should continue
to detect problems as early as possible.
The collector's clutch assembly should be
inspected for signs of wear. The failure
of the precipitation collector's sensory
heaters has greatly diminished. A simple
check of the collector's sensory heater
by activating the collector with water and,
after 5 min, lightly touching the sensory
surface to verify it is heating, should con-
tinue.
A number of rain gauges were found
to be out of calibration. However, many
of those calibrated in 1985-1986 met
specifications in 1988. It is recommended
that a simple, on-site calibration check1
of the rain gauge be carried out every
six months. A copy of the gauge chart
used for the check should be forwarded
to the network's Central Analytical Labor-
atory (CAL) for review.
Recommendations for improving site
locations center on those siting criteria
that, if violated, may affect the catch
efficiency or chemistry of the precipitation
samples. Specifically, it is recommended
that the NADP/NTN Coordination Office
take the following steps to correct con-
ditions at several sites.
Relocate the collector or remove the
obstruction (tree, etc.) that causes the
45° angle rule to be violated (five sites).
Relocate the collector or restrict use
of nearby parking lots and storage
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facilities so that a 100-m separation is
achieved (six sites).
Relocate the collector or install fencing
so that animals are kept at least 30 m
away (12 sites)
Relocate the collector so that transpor-
tation roadways and sources are at
least 100 m away (two sites).
Reorient the collectors whose wet-side
collection bucket faces north or east
so that all wet-side buckets face west
(seven sites).
Where expedientand inexpensive to do
so, relocate collectors or rain gauges
so that a minimum separation distance
of 5 m is achieved (15 sites).
Emphasize to site operators and super-
visors that grass, weeds, and small
trees or bushes should be kept at a
height of 2 ft or less in a circle with
a radius of 30 m from the collector.
Level any collectors or rain gauges that
are out of tolerance (two sites).
Investigate whether or not the resistivity
required to activate the collector sensor
should be set closer to the factory value
of 80K n for several of the collectors.
Supply rain gauge dampening fluid
(silicone oil) to those sites that may
need to fill reservoirs to within 0.25 in.
of the top.
Site Survey Visits
A quality assurance systems survey
was conducted at each site to qualitatively
assess the site, its surroundings, and the
operator's adherence to procedures
specified in the NTN design document
and in the NADP/NTN site operator's
instruction manual. Criteria for siting an
NADP/NTN precipitation station are
illustrated in Figure 2. The operator was
asked to demonstrate sample collection
and analysis, procedures. These were
observed with special attention given to
calibration procedures and sample han-
dling technique. Site equipment was
examined for signs of wear or faulty
operation. It was noted whether solutions
and equipment were properly stored. Site
logbooks and rain gauge charts (if
present) were examined for legibility,
completeness, and accuracy.
Information from the systems survey
was entered in the systems survey
questionnaire. Two sets of photographs
(color slides) of the sites were taken. The
N, E, 8, and W views were photographed
with the precipitation collector in the
foreground. Additional views were taken
as specified in the questionnaire.
A quantitative performance survey was
conducted at each site. Table 1 lists the
equipment that was checked for perfor-
mance and the type of test used. Criteria
for evaluating performance are specified
in the NADP Quality Assurance Plan.
Wo residential
structures
within 30m,
within 30° .
cone of
mean wind
direction
Wo
~~ object
should
project
_ beyond \
Wet bucket-
Collector L-X
Overhead
wire, tree,
building,
etc.
5m
Conversion
m-ft
0.3-1.0
0.6-2.0
5-16
20-66
30-98
500-1640
km - mi
10-6.2
20-12.4
40-24.8
\
Notes
Platforms discouraged; however, no higher than anticipated ^_
snowpak
Spacing between the gauge and collector at 5 to 30m
* Wo residential buildings within upwind 30° cone
If more than 2096 of precipitation Is snow, gauge must have an
alter wind shield, pivot axis at same elevation as gauge inlet
In snow areas, collector roofs should be properly counter
weighted
* Question future land use
Changes must be submitted to coordinator's office
Wo objects greater than 1 m in height
20m* Slopes±15%
> Natural vegetation <0.6 m :
1 Wo grazing animals , '
30m* No sudden changes in slope greater than ±15%
Farm area should be nothing except vegetation maintained at less
than 0.6 m
TOO m* No surface storage of agricultural products, fuels, vehicles,
parking lots, or maintenance yards
No moving source of pollutants such as runway, taxiway,
road, or navigable river
500 m* No feed lots, dairy barns, or large concentration of
animals
10 km * No downwind industries, factories, chemical or
power plants
* No downwind urban areas greater than 10,000
20 km No upwind industries, factories, chemical
or power plants
No upwind urban areas greater than
10,000
> Wo downwind urban areas greater than
75,000
40 km* No upwind urban areas greater than 75,000
Figure 2. NADP/NTN siting criteria.
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Table 1. NADP/NTN Site Measurements and Performance Survey Methods
Site
Measurement
Measurement
Device
Performance
Survey Method
Designated
Performance
Criteria
Rain depth
Precipitation sample
collection
Mass
PH
Conductivity
Rain gauge (Belfort)
Precipitation collector (Aero-
chem Metrics)
Triple beam balance
pH meter and electrode
Conductivity meter and cell
Challenge with known
weights that simulate rainfall.
Measure resistance across
sensor, measure tension and
drop of bucket lid, measure
temperature and resistance
of activated sensor.
Challenge with traceable
weights.
Challenge with simulated
precipitation sample of
known pH.
Challenge with simulated
precipitation sample of
known conductivity.
Agreement within ±0.1 in. of
test weight value over the
range 0-12 in.
Resistance in range of 60-
90K n. Lid drop distance >3
mm. Sensor temperature
ambient prior to activation;
temperature of 50-70° C after
activation.
Agreement within ±5 g of
test weight value.
Agreement within ±0.1 pH
unit of test solution's desig-
nated value.
Agreement within ±4 fjS/cm
of test solution's designated
value.
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W. C. Eaton, C. E. Moore. R. W. Murdoch, R. C. Shores, and D. A. Ward are with
Research Triangle Institute, Research Triangle Park, NC 27709.
Berne I. Bennett is the EPA Project Officer (see below).
The complete report, entitled "Summary Report for the National Atmospheric
Deposition Program/National Trends Network (NADPiNTN) Site Visitation
Program for the Period October 1987 through September 1988," (Order No.
PB 90-212 614/AS; Cost: $17.00, 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
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-90/040
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