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

-------
  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.
                                          ,
                 '.,V~-3  ••>   .  „         ..   ..   \     ..~5?"£
                 '•'••»  .->.\>      „    i	:  '-...e^
                    •h     c»^ «d   v—-TT	1          T      s
                 v.^       ic    ••   ;           I     SO   -c    -^   ~x  SH  '
         T-   ND.«,  \    ~"v
          I           I MN
                   •>—C         vvwv    t   •"   -L?_V   K-^
                    /      •-rW    •        ,'	4       •S-sAJ"  jfe?
                    (    «v     '        T^r~.-L, "• «   A  "    }i   T>T.T-,
                   •0\       bf      »cj P%o **"     j	X      V    **J  IM  !tS_/v
                                                                    0  100 200 300 400 Mi
                                                                           1 - 1
                     AS
                      \9*
                                                                    0  161 322 483 644 Km
                                                                                                         OS?
Figure 1. Location of active sites in the NADP/NTN network as of August 1989.

-------
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

-------
   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.

-------
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.

-------

-------

-------
 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

-------