United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-89/024 Sept. 1989
<>EPA Project Summary
Quality Assurance Audits of the
EPA State-Operated
Precipitation Collection
Network: I987
W. Gary Eaton, Curtis E. Moore, R. W. Murdoch, and Dan A. Ward
The collection of precipitation and
the measurement of its constituents
are important steps In attaining a
better understanding of the distribu-
tion and effects of "acid rain" in the
United States.
The full document reports the find-
ings from quality assurance and
technical assistance visits made in
1987 to the 29 sites that comprise the
State-Operated Precipitation Network.
The network Is staffed mainly by
personnel from state environmental
agencies and forestry commissions.
It is under the overall sponsorship of
regional and national offices of the
U.S. Environmental Protection
Agency.
Procedures followed in conducting
the site visits are described. Results
of systems and performance audits
are discussed for siting, collection
equipment, and field laboratories.
Where exceptions are found, the
possible effects of nonstandard sit-
ing and improperly operating equip-
ment on the data base are discussed.
Recommendations are given for
improvement and standardization of
sites and the network as a whole.
The findings from visits to the sites
in 1985/86 are compared to the find-
ings frorrt^he 1987 visits.
This Project Summary was devel-
oped by EPA's Atmospheric Research
and Exposure Assessment Laboratory,
Research Triangle Park, NC, to an-
nounce 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
This document is the summarizing re-
port of quality assurance audits and
technical assistance provided to the
State-Operated Network of precipitation
collection stations during survey visits
made in the period May through October
1987. During the period covered by this
report, the State-Operated Network con-
sisted of 29 sites in EPA Regions III, IV,
VI, and VIII that collect precipitation sam-
ples on a weekly basis. States or local
government agencies sponsor the collec-
tion site and its operations and provide
personnel. The EPA regional offices
assist in site selection, operator training,
data processing, coordination of the net-
work, and fund the analysis of samples
through the central laboratory, Global
Geochemistry, Corp., Canoga Park, CA.
EPA-RTP provides a quality assurance
site visitation program through a contract
with Research Triangle Institute (RTI)4.
Data from the network are submitted to
the Acid Deposition System (ADS) for
Statistical Reporting, Battelle Pacific
Northwest Laboratory, Richland, WA.
Goals
The goals for the program of on-site
quality assurance assistance to the sites
in the State-Operated Network are to:
(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 re-
sponse of field and laboratory
measurement devices for precipita-
tion depth, mass, temperature, con-
ductivity, and pH through on-site
performance tests;
(3) Provide technical assistance to the
operator by verbal explanation, mi-
nor troubleshooting, calibration of
equipment, and by making recom-
mendations for corrective action;
(4) Submit brief reports for each site
detailing site characteristics, results
of quality assurance tests, and tech-
nical assistance provided;
(5) Document the locations of the sites
and their surroundings by assem-
bling a collection of site maps and
color slides.
Conclusions
The State-Operated Network is a week-
ly precipitation collection network of 29
sites located primarily in the eastern and
southeastern United States. State agen-
cies have provided personnel to service
the sites and laboratories to analyze the
samples and submit them to the central
laboratory for further analysis. The site
supervisors, operators, and analysts were
found to be familiar with their duties,
handled the precipitation samples
carefully, analyzed the samples accu-
rately in most cases, and seemed genu-
inely interested in the network and the
data.
A number of the sites still need to be
improved upon in terms of siting and
maintenance of sample collection and
analysis equipment. Emphasis should be
placed on proper placement and
operation of precipitation collectors,
installation and proper operation of rain
gauges, and standardization of field
laboratory techniques.
Compared to results of the 1986 site
visits, the 1987 data show significant
improvements have been made in the
accuracy of site pH and conductivity
measurements; in the cleanliness of the
collection bucket lid and the goodness of
its seal against the collection bucket; and
m satisfying the criteria for collector
height above ground and in relation to the
rain gauge. Several sites are still in need
of modification in order to be removed
from nearby obstructions.
Recommendations
The following recommendations are
drawn from the Results and Discussion
section of this summary. The first four
recommendations are the most important
to institute.
1. Precipitation Collector
Malfunctions
Repair or replace those collectors that
were found to be malfunctioning.
Particular attention should be given to the
sensors that do not heat properly. In this
way, the collection of wet-only samples is
assured.
2. Sample Collector Relocation
Any sample collection equipment that
is obstructed by trees or structures
should be relocated so that the 45°
projection angle and 30° arc siting
criteria are satisfied. Rain gauges should
be repositioned so that they are sepa-
rated from the collector by at least 5 m
(but no more than 30 m), and so that their
orifices are level and in the same plane
(to ± 1 foot) as that of collector bucket
rims. The collector should be installed
such that when the long axis of the
collector is oriented west to east, the
collector's wet-side bucket faces west.
3. Repair or Acquire Rain
Gauges
Inoperative rain gauges should be re-
paired and repositioned to meet siting
criteria. Recording rain gauges should be
acquired for those four sites that do not
have them. Precipitation collectors should
be electrically connected to the rain
gauges so that their openings and clos-
ings can be noted as event marks on the
rain gauge chart. Use the rain gauge
chart and the event marker as a quality
control tool to validate the proper opera-
tion of the collector. Periodic quality con-
trol checks should be made to ensure
that the rain gauges are operating cor-
rectly and accurately.
4. Quality Control Check of
Sensor
There is still a need to institute a
simple quality control check to be per-
formed by the operator at least once per
month to detect collector sensors that
heat improperly so that corrective action
can be taken.
5. Standardize Field Laboratory
Techniques
Field laboratory techniques and equip-
ment should be standardized so that
small volumes of samples are usec
determine conductivity and pH. !
operators should abide by the guide
that requires that the central labora
receive priority in analysis of sm
volume weekly samples.
6. Correct Siting Criteria
Variances
Other siting criteria variances not nc
in (2) above should be corrected as ft
ing and time allow.
Approach
The following approach was utilizec
preparing for and providing quality as!
ance assistance to agencies maintair
precipitation collection sites in the Sfc
Operated Network.
First, pertinent network documents .
reports were reviewed, and from tfi
two questionnaires were prepared I
are specific to the operation of the St<
Operated Network. One questionnaire
used to conduct a systems and p
formance survey of the site z
laboratory operations and the operati
adherence to designated procedur
The other questionnaire addresses sil
criteria for either a regionally-located
an urban-influenced site. The syste
and performance survey questionn;
can be found in the project work plai
The siting criteria questionnaires w
given in the report of 1985/1986 Qu«
Assurance Audits and are illustrated
regionally located and urban-located si
in Figures 1 and 2, respectively.
Second, contact was made by t
phone and letter with those perst
whose sites were to be visited. Rep
sentatives from the EPA regional offi
the state and/or local air quality organi
tion, and, if applicable, the sponsor
agency were invited to be present ak
with the site supervisor and operator.
The dates for the site visits were '.
the itinerary planned, and informat
such as maps, source inventories, ;
photographs were acquired for sti
prior to the actual site visit. Source lo
tion "bulls-eye" maps were created fr
the 1980 NAPAP Emissions Invent
data base and used to verify the pr
ence or absence of sources within a
km radius of the site.
Third, the sites and field laborator
were visited and evaluated. During
visit, the questionnaires were comple
and each site was documented
sketch, photographs, and by ascertain
its location on a map such as the US
1:24,000 series. A one-page brief s
survey report of findings was comple
-------
Regionally located: Rural area at least 5 km distance from urban carters oflOOOO
inhabitants and at least 10 km distance from mapr industrial sources or urban centers
0175000 inhabitants
500 m Surrounding vegetation, land features and structures should
\ be typical of region (3)
No sources of fugitive dust (cement plant or granary) (10)
No large concentration of animals, such as a dairy feed lot (11)
not to
30* arc and
vertical atovation
nodomcafldtSMS)
Conversion
m
05
06
5
10
20
30
50
75
100
500
km
075
10
20
50
10
20
ft
- 16
- 20
- 16
- 33
- 66
- 98
- 164
246
- 328
- 1640
- ml
- 05
06
- 1 2
- 31
- 62
- 124
5 m No collocated equipment (2)
10m
50m
* No roads (14)
75m
Ground cover less than 06 m in height (3)
No driveways (14)
20 m No domesticated grazing animals (6)
No cultivated fields (7)
30m Slope of ground should be less than 20° (1)
Hilltop sites should have a slope of less than 30° (1 1
Wooded sites at least 30 m from woodline (4)
No parking lots with greater than 10 vehicles and where traffic
movement is limited to brief episodes daily (12)
100m
Spacing between the gauge and the collector should be 5m to 30 m(1)
Collector and gauge should be mounted at ground level or at an elevation
of no more than 1 m(1)
Spacing between the gauge and the collector can be less than 5 m
if mounted on a platform in high snowfall areas (1)
No sources such as landfills, sewage treatment facility (8)
No open surface storage of agricultural products, fuels or vehicles (9)
No large parking (>20 vehicles), smarter parking areas with frequent
use and vehicle/equipment service area (13)
No roads with more than 30 veh/h-24 h avg to 30 m radius 115)
Nearest small community (100-1,000) (17)
Nearest urban area (1.000 -10.000) (18)
20km* No oceans or saltwater bodies (16)
No interstate highway, railroad complex (22)
5km« Nearest urban area(10,000-75,000)(19)
10 km Nearest industrial source, power plant.
chemical plant (2t)
20km. Nearest urban area (>75.000) (20)
Figure 1 Siting criteria diagram for regionally located state-operated precipitation network sites
>nd reviewed with the operator at the
inclusion of the site visit.
Fourth, a brief report of the visit was
>repared for each site. These reports
vere reviewed by the EPA Project Offi-
:er, revised as appropriate, and sent to
egional, state, and/or local officials re-
ponsible for the collection site
Questionnaires
Two questionnaires were used during
le site visits. The first was a field site
ystems and performance survey ques-
onnaire that allows the site visitor to ask
Decific questions and record information
oncernmg the following collection site
atures:
the precipitation sampler,
the rain gauge,
sample collection and handling
procedures,
the field laboratory, recordkeepmg,
and site notebook,
the pH meter,
the conductivity meter, and
the balance
The questionnaire contents are based on
those features common to the National
Atmospheric Deposition Program (NADP)
and National Trends Network (NTN)
precipitation collection networks. It may
be found in the work plan for quality
assurance assistance to the State-
Operated Network1. The EPA's "Quality
Assurance Manual for Precipitation
Measurement Systems"2 was also used
as a source of information. Additional
questions are included concerning this
network's use of plastic bag bucket liners
and polyethylene bottles for shipping
samples from the site to the central
Iaboratory3
The second questionnaire concerns
siting criteria. Depending on location, a
questionnaire designed for either a re-
gionally-located or an urban-influenced
site was used. Information in the
questionnaires is based on that given in
three documents: the EPA "Quality As-
surance Manual for Precipitation Meas-
urements,"2 the U.S. Geological Survey
document "Design of the Nationaf Trends
Network for Monitoring the Chemistry of
Acid Precipitation,"4 and the "NADP
Instruction Manual. NADP'NTN Site
Selection and Installation. "5 The siting
criteria questionnaires were used to
evaluate the suitability of each site m
terms of:
-------
Urban located: Ctoaer than 5 km to an urban center of 10^ to 7S0TO (or more)
inhabitants or dosar than 10 Km to major industrial source
5m* No collocated equipment
10m No driveways (11)
Ground cover less than 0.6 m in height
30m Wooded sites at least 30m from woocHine (5)
Steepest slope of ground should be less than 20° (D
Hilltop sites should have a slope of less than 30° (1)
No roads (11)
No large parking areas (>20 vehicles), smaller parking areas
with frequent use and vehicle/equipment service area (10)
50 m No roads with more than 120 veh/h-24 h avg to 30 m radius (12)
Conversion
m
05
0.6
5
10
30
50
100
200
500
km
1
2
32
ft
- 16
- 20
- 16
- 33
98
- 164
- 328
- 656
1640
- ml
- 06
- 1 2
- 20
Notaa
Spacing between the gauge and the collector should be 5m to 30 m(1)
Spacing between the gauge and the collector can be less than 5 m
if mounted on a platform in nigh snowfall areas (1)
The collector should not be located on the ground level along heavily
traveled city streets (12)
Rooftop siting (2)
- Roof approximately the same height as those of surrounding buildings
-Free of dusty materials
- Buildings of 1 to 3 stones preferred
- Located new the canter of the building as far as possible from exhaust
or inlet vents
- Be cognizant of chimneys, exhausts, etc. on adjacent buildings
100 m No sources such as landfills, sewage treatment facility (7)
No open surface storage of agricultural products, fuels or chemicals (8)
200 m No sources of fugitive dust, such as a cement plant (9)
500 m Surrounding vegetation, land features and structures
should be typical of region (3)
1 km No interstate highways, major thoroughfare.
airport or railroad complex (15)
2 km No oceans or saltwater bodies which may
contribute salt spray (13)
3 2 km No major industrial source, coal or oil
burning plant or foundry (14)
Figure 2. Siting criteria diagram for urban located state-operated precipitation network sites.
type and height of groundcover in
the immediate vicinity of the pro-
posed location of the sampling
equipment (important to avoid
sample contamination from the soil
or plants)
distance of the sample collector
equipment from obstructions (im-
portant to avoid sample contami-
nation and variation in sample catch
efficiency)
distance of the sample collection
equipment from nearby and distant
sources of contamination and pollu-
tion (important to avoid undue
source influences on the sample's
constituent concentrations which, if
present, make the sample less rep-
resentative of the region)
human or animal activities in the
vicinity of the collection site (im-
portant to avoid sample
contamination)
topographic, hydrologic, and
orographic features of the land
surrounding the site (important for
regional representativeness, catch
efficiency, avoidance of sample
contamination, and desirable collec-
tor sensor operation).
Quality Assurance Audit
Procedures
Auditors accompanied the operator and
others to each collection site and field
laboratory with the dual aims of (1) doc-
umenting the site, its operation, and the
accuracy of its instrument response to
various quality assurance tests, and (2)
providing information, training, and in-
struction for operators and supervisors,
equipment calibration and minor main-
tenance as needed, and establishing con-
tacts for further information and/or major
repairs. A list of items checked is given in
Table 1. All data from the site visit are
recorded in a bound and numbered
notebook. This notebook contains infor-
mation concerning the site, a record of
pre-trip confirmation of test solutions and
audit devices, and the questionnaires.
The original notebook is filed at P
under a document control system.
Systems Survey
A quality assurance systems survi
was conducted to quantitatively asse
the site and its surroundings. One of t\
siting criteria questionnaires was ei
ployed, depending on whether the s
was regionally-located or urban-infl
enced. The criteria address a site
spatial relationship to different types
sources and interferents which m
cause precipitation collected at the site
be unrepresentative of the region. T
factors determining the criteria inclui
nearby point sources (e.g., mdustr
burners), line sources (e.g., roads), ov<
head obstructions to the collector (e.
trees), and obstacles or land and aqua
features which may alter the wii
patterns near the collector.
The operator's adherence to proc
dures specified in the site operator's
struction manuals2'3.6 was also assesse
The operator demonstrated sample c
lection and analysis procedures whi
-------
Table 1. Ust of Hems Checked During Site Survey Visit
Precipitation Sampler
lid/bucket seal
sensor heater works
clutch tension
clutch wear
winter problems
proper counterbalance
contamination by straps
snow roof design, material, orientation
level
lid tension or drop
bucket/sample handling
orientation, height
distance from other equipment
Supplies
check inventory
shortage
excess
plastic bag bucket liners
accuracy of response
calibration weight handling
tolerance checks
correct use of balance
Siting Characteristics
distances from collector to:
other equipment
obstructions
roads, towns, cities
sources
topographic features
land use
photographs, sketches
Precipitation Gauge
winterization
calibration of weight response
cleanliness
time calibration
event marker working
accuracy of chart reading (±0.1 inch)
gauge data that is reported
distance from other equipment
height
pH Meter and Use
accuracy of response
no electrodes in bucket
± 0.2 pH units agreement with test solution
electrode condition electrode brand
order of use
use of pH check solution
storage of buffers, check solutions
Conductivity
accuracy of response
no electrode in bucket
use of 75 itmho/cm standard
Sample Collection Procedures
bag liner changed after 7 days
collector checked each Tuesday
contamination checks
were observed, with special attention
given to sample handling technique and
calibration procedures. Site equipment
was examined for proper installation and
for signs of wear or faulty operation.
It was noted whether solutions and
equipment were properly stored. Site
field reports and rain gauge charts were
examined for legibility, completeness,
and accuracy.
Results and Discussion
Collection Site
Precipitation Collector System
Checks
Systems checks were made of the pre-
cipitation collector. In 1987, the State-
Operated Network had four different
brands of collectors in use: Aerochem
Metrics, N-CON, MIC, and Andersen.
Each is a wet-dry collector of similar
design; thus, the systems checks gener-
ally apply to each brand. The checks are
explained and discussed below.
Height Standard
The collector should be installed on its
standard 1-meter-high aluminum base.
To prevent obstructions to windflow, the
base should not be enclosed. Six of the
29 collectors were not at standard height.
In all cases, this was due to their being
on a platform or shelter roof. The War-
wood and Charleston collectors were on
the roofs of two-story buildings and met
urban siting criteria. None of the col-
lectors had the base enclosed.
Platform
In areas having an accumulation of
over 0.5 meter of snow, the collector may
be raised off the ground on a platform.
The platform should be no higher than
the maximum anticipated snow pack. For
the most part, the platforms were short -
not more than 1 or 2 feet in height. The
higher platforms (Rocky Gap, Cape
Romaine, and Congaree Swamp) were
necessary to raise the collector orifice
above the level of a nearby earthen dam,
a nearby monitoring shelter, and to pre-
vent flooding at times of high water in the
swamp, respectively. The effect of these
platforms on the sample is believed to be
minimal. For those collectors located on
the tops of monitoring sites or buildings
(Greenbrier, New Manchester, Charles-
ton, and Warwood), it is not clear what
the effect may be. If the collectors were
placed near ground level at the West
Virginia sites, platforms would probably
still be required due to the snow.
Wet Bucket Orientation
The collector should be mounted level
with the wet side bucket to the west and
the sensor facing north. In this way, the
wet bucket is generally upwind of the dry
side bucket (winds generally being from
the S to SW in the eastern United
-------
States), and the sensor is downwind of
the wet side bucket. This placement is:
designed to lessen the chance for con-
tamination and to minimize obstruction to
sample entry by the collector itself.
Fifteen of the 29 collectors are
correctly installed with the wet bucket
facing to the 3W, W, or NW. Two are
installed with the wet bucket facing S.
These southerly installations probably
have no effect on the data. The 12
collectors that are installed with the
collection bucket facing N or E may
cause an aberration in the collection effi-
ciency or sample chemistry. It is recom-
mended that all collectors be oriented
with the wet bucket facing W and the
sensor facing N. The date this change
occurs must be documented and accom-
pany the data base. This arrangement is
not possible with the Andersen sampler
since the sensor faces south when the
wet bucket is oriented to the west.
Distance from Rain Gauge
The collector should be located within
a distance of 30 m of the rain gauge but
no closer than 5 m. This guideline is set
so that the collector and gauge "see" the
same precipitation event, and so that
neither piece of equipment offers an
aerodynamic interference to the other's
collection ability.
Of the 25 sites that have collocated rain
gauges (West Virginia sites do not have
them), 14 were closer to the precipitation
collector than the prescribed 5 meters. Of
the 14 that were too close, three were
tipping bucket rain gauges. Because the
volume they displace is small compared
to the larger Belfort weighing rain
gauges, the effect of being closer than 5
meters is thought to be negligible. The
other gauges that were too close should
be moved further away if possible. These
moves must be documented and noted in
the data record through the Acid
Deposition System (ADS) of data
tabulation and retrieval7.
Collector Connected to Event
Marker
To assess the proper operation of the
collector, a switch should be included in
its mechanism to send a signal to an
event marker to signal the opening and
closing of the wet side bucket. It is con-
venient to have this record on the rain
gauge chart.
Eight of the sites lack such a feature.
Four of these eight have no rain gauge
present. It is recommended that these
sites acquire event marker capability,
preferably on the rain gauge chart.
Height Correct with Respect to
Rain Gauge
The heights above ground of the col-
lection bucket and the rain gauge orifices
should be within 1 foot of each other.
Two of twenty-five sites did not meet
this criteria. In one of these cases
(Hiawassee), the relative heights were
very close to meeting the criteria, and the
effect on the data is expected to be
negligible. If the collector and/or gauge
are repositioned in the future, this could
be corrected and documented at that
time. The Center Hill's tipping bucket
gauge is mounted on a meteorological
tower 25 feet above the collector.
Cover Seats Properly on Wet
Bucket
The collector's bucket cover should fit
tightly and evenly on the rim of the wet
(and dry) bucket so that dust cannot
enter during dry periods (and so that the
cover is protected during wet periods). All
covers seated properly.
Precipitation Collector
Performance Checks
Six performance checks were con-
ducted on the precipitation collectors. Not
all checks were carried out on all col-
lectors since the checks were designed
for the Aerochem Metrics collector and
there was concern that certain tests
might affect the adjustments of the other
brands of collectors. The tests and re-
sults are discussed below.
Lid Tension
The force that the bucket cover exerts
against the rim of the collection bucket
may be assessed by lifting the lid slightly
above the bucket and reading the force
(in grams) required to do so. A spring
scale is used. Generally, tensions of 1500
g or greater are found for the Aerochem
Metrics brand. Two of 21 collectors
checked had lid tensions less than 1500
g. It should be noted that each of these
was a brand other than Aerochem Met-
rics and the covers seated properly on
the wet buckets. Whether or not these
lower tensions are significant is not
known.
Lid Drop Distance
Another measure of adequate
lid/bucket seal tension is the lid drop
distance--the distance the lid drops when
the wet bucket is momentarily removed.
The Central Analytical Laboratory (Illinois
State Water Survey) of the NADP/NTN
network has found that a distance of 3
mm or greater is required to give tight,
dust-free seals with the Aeroch
Metrics collector. Of 16 collectors tes
all had 6 mm or greater lid d
distances. One of the two collectors \
low lid tension (as measured by
spring scale) had a 16 mm lid drop i
tance; the other collector was not teste
Ambient Sensor Grid
Temperatures
Generally, the temperature of the pr<
pitation collector sensor is at ambi
level when there is no precipitation. If
air temperature is below 4°C, the sen
heater (of the Aerochem Metrics) is se
come on, at a lower power level, to n
ice or snow that may fall. A sensor sho
not be heating at high temperatu
(50°C or higher) unless it is raining, If i
heating, light rainfall striking the sen
may evaporate before a sufficient amo
can accumulate, complete the circuit, £
open the lid.
Three of the 29 sensors were found
be heating at temperatures considera
above ambient when no rain was falli
Sensors at Lum's Pond, Grant Fore
and Carville should be repaired. T
Greenbrier and Charleston N-CON c
lectors are apparently set to heat at
times.
Sensor Grid Temperature Five
Minutes after Activation
There were a number of problems w
the temperature of the activated sense
eight sensors heated at all times (al
temperature either too hot or too co<
five sensors did not heat at all; nine SE
sors heated, but the temperature attain
was lower than 50°C.
Liner Condition
Most of the plastic lid liners were
good condition. Three had mold or rr
dew on the undersides. It was recoi
mended that this be removed by wipi
with deionized water and a laboratc
tissue.
Resistance to Activate Sensor
Sensors activated at a median res
tance of 80 Kohms. Three sites (Grays
Lake, Mammoth Cave, and Center H
required a very low resistance. Four sit
(Mobile, Tallassee, Greenbrier, and N<
Manchester) had a very high resistanc
The collector sensors' very low r
sistance requirements were all associate
with the MIC-type collector. Three of tl
very high resistance sensors were tl
Andersen brand; one was the N-CC
brand. Because these sensor resistanc
are so extraordinarily different from tl
ACM sensor, it is recommended that the
-------
be adjusted to activate at resistances of
70 to 80 Kohms. The low resistance
sensors may not activate at the desired
times; the high resistance sensors may
activate too often, or in response to
leaves or insects.
Rain Gauge System Checks
The four sites in West Virginia do not
have rain gauges. Seven sites use tipping
bucket gauges; 18 sites use the Belfort
weighing rain gauge. All gauges were
level and installed in a stable manner.
The reason for several gauge openings
not being 1.5 meters above ground is that
these gauges are mounted on platforms.
Event marks (corresponding to opening
and closing of the precipitation collector)
were not being made at the Lum's Pond,
Dawsonville, and University sites. It was
recommended that repairs be made.
Rain Gauge Performance
Checks
Quantitative performance checks were
conducted at 16 of the 18 sites that use
Belfort rain gauges. Rain prevented the
audits of two gauges. The quantitative
performances of the tipping bucket
gauges were not checked. Thirteen of the
gauges were within the accuracy goal of
± 0.1 inch agreement with the audit
value over the entire 0 to 12 inch range.
Three varied by > ±0.1 inch; however,
for two of these the variation occurred at
depths of 6 inches or greater, a seldom
used range. Each of the out-of-calibration
gauges were readjusted to bring them
into ± 0.1 inch agreement over the entire
0 to 12 inch range.
Only the Rocky Gap, MD gauge was
out-of-calibration at depths below 6
inches. Values for the Rocky Gap gauge
are low by about 0.14 inch over the range
2 through 5 inches. It is still recom-
mended that site operators obtain and
use (twice a year) accurately weighed
bottles of sand or water to check the
performance of the rain gauges.
Sample Collection Procedures
Site operators were asked four ques-
tions concerning collection of the sample.
Did the operator approach the collector
from downwind? This is to prevent dust
or hair from blowing off the operator into
the bucket. Is the liner of the bucket
changed after 7 days? A sample should
be collected weekly. The bag liner in the
bucket should be changed weekly even if
no precipitation has occurred. Is the
collector checked on Tuesday? For uni-
formity across the network and for
comparison to other networks, the
designated sample retrieval day is Tues-
day. Also at this time the collector and
rain gauge should be checked for proper
operation. Is the bucket checked for
contamination? The person who re-
moves the sample from the collector
should visually check it at the time of re-
moval. Small dust particles or bird drop-
pings may dissolve and not be noted a
day or so later in the laboratory. These
observations should be entered on the
sample report form.
All operators were using proper sample
collection procedures, and no instances
of contamination were noted. Only one
operator left the sample bucket and liner
in the collector more than 7 days if no
rain had occurred. Protocol calls for the
bag liner to be removed and replaced
with a new one if no ram occurs for a
week.
Field Laboratory
Systems Check of Field
Laboratory
The laboratories that support the field
collection sites are generally state or
county laboratories and have adequate
space, are clean, and are temperature-
controlled.
Several laboratories serve more than
one site. The South Carolina Department
of Environmental Health and Control
Laboratory in Columbia performs the field
measurements on samples from the four
South Carolina sites. The West Virginia
Air Pollution Control Commission's labo-
ratory in Charleston serves the Charles-
ton and Greenbrier sites. A branch labo-
ratory of the Commission in Warwood,
WV serves the Warwood and New Man-
chester sites. Similarly, the state of Dela-
ware laboratory analyzes samples for
both the Georgetown and Lum's Pond
sites.
Most of the laboratories handle the
samples in a prompt manner and keep
annotated records. Only one site was
taking longer than 3 days before mailing
samples to the network's central labora-
tory; the samples were being mailed
within one week.
It is important to note that during part
of 1987, the West Virginia sites were not
sending their samples to the network's
central laboratory for detailed analysis.
Instead, the samples were analyzed at
the Charleston and Warwood
laboratories.
It was not possible to check the rain
depth charts at all sites. Several sites
sent the charts to a central point for
review and archival. The two Kentucky
sites used strip chart recorders, and the
four West Virginia sites did not use
recording rain gauges.
Conductivity
Five items that relate to techniques
used for conductivity measurements were
examined. Few of the site laboratories
use the small YSI conductivity cell and
thus cannot use the cell in an inverted
position to economize on sample volume.
With one exception, all site laboratories
tested the conductivity standard before
testing their deionized water. The pur-
pose of doing this is to establish a
correction factor (for the cell and tem-
perature) for use with subsequent meas-
urements at the same temperature
All site operators asked said they used
distilled water to rinse the electrode dur-
ing the analysis and before storing it. All
sites queried also rinsed the conductivity
cell with sample before refilling it with
sample and taking the final reading
Almost all field laboratory operators
corrected their conductivity readings to
25 °C (the standard temperature) before
recording the value. Two sites in West
Virginia did not.
All site operators and laboratory ana-
lysts measured sample conductivity then
sample pH. This is the prescribed order.
The only recommendation is that sites
seek uniformity in the volume of sample
required for conductivity measurements.
On a within-state or within-agency basis,
the data sets may be consistent. How-
ever, when the entire State-Operated
Network data base is considered, some
sites may not have as many analyses of
low-volume events due to the larger
amounts used in the field analyses. In
general, the central laboratory, not the
local laboratory, should be given priority
in receipt of samples.
pH
Five items concerning pH measure-
ment techniques were examined. A wide
variety of electrode storage solutions are
still in use. The use of deionized water is
acceptable, but probably shortens the life
of the electrode. All sites determined pH
with the electrode's electrolyte fillhole
open. It should be open during calibration
and analysis to allow free flow of
electrolyte through the junction. At all but
one site, the pH electrode was rinsed
with deionized water, operators handled
the electrode properly, and all but one
site (Warwood, WV) used the two-buffer
calibration technique with slope adjust.
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Results of Field Site Analysis of
Simulated Precipitation
Each field laboratory was asked to
analyze a performance audit solution for
conductivity and pH. These solutions
were prepared by dilution of EPA
supplied performance test solutions; the
audit value is designated by EPA. Desig-
nated quality limits are ± 0.1 unit for pH
and ± 4 nS/cm for conductivity.
References
1. Eaton, W. C. and E. L. Tew. Work
Plan for Quality Assurance Assistance to
New and Existing Acid Precipitation Col-
lection Sites in the State-Operated
Network. October 1985. Prepared under
EPA Contract 68-02-4125.
2. Topol, L. E., et al. Quality Assurance
Manual for Precipitation Measurement
Systems. Part I. Quality Assurance
Manual. U.S. Environmental Protection
Agency Publication No. EPA-600/4-82-
042a. Revised January 1985.
3. Eaton, W. C. and E. D. Estes. Use of
Plastic Bags as Bucket Liners for the
Aerochem Metrics Precipitation Collector.
May 1984. Prepared under EPA Contract
68-02-3767, Task 86.
4. Robertson, J. K. and J. W. Wilson.
Design of the National Trends Network
for Monitoring the Chemistry of Atmos-
pheric Precipitation. U.S. Geological Sur-
vey Circular 694, 1985.
5. Bigelow, D. S. NADP Instructi
Manual: NADP/NTN Site Selection a
Installation. National Atmospheric Depo
tion Program Coordinator's Offic
Colorado State University, Fort Collii
Colorado, July 1984.
6. Topol, L. E., et al. Quality Assuran
Handbook for Air Pollution Measurer
Systems, Volume V - Manual for Prec
itation Measurement Systems, U.S. E
vironmental Protection Agency Public
tion No. EPA-600/4-82-042b, revised Ji
1986.
7. Watson, C. R. and A. R. Olsen. A(
Deposition System (ADS) for Statistii
Reporting - System Design and Use
Code Manual. EPA-600/8-84-023, Se
tember 1984.
W. Cary Eaton, Curtis E. Moore, R. W. Murdoch, and Dan 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 "Quality Assurance Audits of the EPA State-
Operated Precipitation Collection Network: 1987," (Order No. PB 89-154
4801 AS; Cost: $18.95, 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/S3-89/024
floTECTIO. AGE.CY
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