PROGRAMS AND PLANS: "Quality Assurance of WRD Water Quality Data: Past, Present, and Future"

                                              July 30, 1980

Quality of Water Branch Technical Memorandum No. 80.21

Subject: PROGRAMS AND PLANS: "Quality Assurance of WRD Water-
         Quality Data: Past, Present, and Future" by Linda C. 
         Friedman.

The enclosed paper, discussing primarily the evolution of 
laboratory quality assurance measures, was prepared originally by 
Linda Friedman for presentation at a Regional seminar. Because of 
the paramount importance of quality assurance in all of our 
activities, the paper is provided for your information.

Please circulate the paper as widely as possible in all district 
and project offices.

                             R. J. Pickering, Chief
                             Quality of Water Branch

Enclosure

Key Words: water quality, quality assurance, laboratories

Superseded memorandum: none

WRD Distribution: A, B, FO-L, PO

QUALITY ASSURANCE OF WRD WATER-QUALITY DATA:
PAST, PRESENT, AND FUTURE

Linda C. Friedman

Although no one would question the fact that any interpretation of 
data depends on the validity of that data, the need for quality-
assurance procedures frequently does not appear to be equally 
clear. However, two facts clearly indicate this need: Data usually 
are collected by a measurement process and errors are inherent in 
any measurement process.

Initially, water-quality data of the U.S. Geological Survey were 
collected in the field and supplemented by work done in state or 
university laboratories; quality control depended primarily on 
correct preparation of standards and accurate use of techniques 
such as gravimetric analysis. In the period 1905-1908, 
comprehensive water-quality studies were begun, as W. H. Durum 
points out in his "Historical Profile of Quality of Water 
Laboratories and Activities, 1879-1973," and these studies led to 
the development of quality control review techniques such as 
looking at the cation-anion balance (Durum, 1978).

In 1918, the first WRD chemical laboratory was established in 
Washington, D.C. Quality control at that time depended on 
correctly prepared standards, careful analyses, and the quality-
control relationships which had been developed in the previous 
decade or so. Refinement of these relationships is obvious in 
papers such as C. S. Howard's "Determination of Total Dissolved 
Solids In Water Analysis," which appeared in 1933 (Howard,1933).

In 1937, a second chemical laboratory was opened in the Texas 
District at Austin and, in the 40's, 50's, and 60's, additional 
district laboratories were added so that by the end of the 1960's, 
there were 22 WRD laboratories. Throughout most of this time, 
there was little change in quality-control procedures. One major 
addition was made in 1962, when the Standard Reference Water 
Sample (SRWS) program was begun as part of Marvin Skougstad's 
Methods Development Project. Initially, two samples of deionized 
water containing known concentrations of calcium, magnesium, 
sodium, potassium, sulfate, and chloride were prepared and sent to 
district laboratories. In 1965, the SRWS program was modified by 
replacing the deionized water solutions with natural waters 
(Skougstad and Fishman, 1975). Two samples were, and still are, 
distributed twice yearly to all participating laboratories and the 
quality of work of each laboratory is judged by comparing 
individual laboratory values with the means and standard 
deviations calculated from values submitted by all participating 
laboratories.

l/ As used in this paper, the term quality assurance describes the 
programs and sets of procedures, including (but not limited to) 
quality control procedures, which are necessary to assure data 
reliability. The term, quality control, on the other hand, is used 
to describe the routine procedures used to regulate measurements 
and produce data of satisfactory quality.

Beginning in 1972, performance of most analyses by district 
laboratories was phased out and these laboratories were replaced 
by the two central water quality laboratories in Atlanta, Georgia, 
and Denver, Colorado. Field analyses, however, remained very much 
a part of water-quality data-collection activities, and the number 
of state, university or other cooperator, and contractor 
laboratories collecting such data increased and now probably 
numbers in the hundreds. (An exact figure should be obtained 
within the next year.)

The problem of assuring the quality of the data produced by all 
these sources is massive and is compounded by the ever-increasing 
amount and variety of analytical work. For example, in 1919, an 
estimated 480 adjusted complete analyses were made with one 
laboratory in operation; and by 1970, approximately 50,000 
adjusted complete analyses were made by 22 laboratories (Durum, 
1978). Although the term "adjusted complete" has largely lost its 
meaning, it is useful for comparison. Applying an estimated 
adjusted complete value to FY 1979 results shows that 
approximately 132,000 adjusted complete analyses were made by the 
two central water-quality laboratories.

This estimate of the increase in amount of analytical work gives 
no indication of the increase in complexity of work. Major 
problems are related to assuring the quality of data produced by 
the huge variety of analytical methods and equipment being used 
today. Fifteen years ago, water samples were analyzed by the U.S. 
Geological Survey primarily for acidity, alkalinity, calcium, 
chloride, color, dissolved solids, fluoride, iron, magnesium, 
manganese, nitrate, pH, potassium, silica, sodium, specific 
conductance, sulfate, and turbidity. Analytical results were 
generally "when analyzed;" in other words, district personnel 
collected a single bottle of water and the lab analyzed all 
constituents from that single bottle. This procedure made things 
simple for both laboratory and field personnel, but gave (and 
gives) numerous problems in interpretation of past results; for 
instance, iron values were reported even if most of the iron had 
precipitated prior to analysis.

By contrast, in FY 1980, the capabilities of the central water-
quality laboratories have been extended to include close to 800 
different water quality characteristics (Figure 1). Samples 
analyzed today include filtered (dissolved) and unfiltered (total 
and total recoverable) water, suspended sediments, bottom 
materials, and cellular material. Preservation and pretreatment 
techniques are numerous, resulting in a plethora of bottles but, 
hopefully, also yielding more meaningful results.

Unfortunately, the district laboratories added few new quality-
assurance procedures as the number of phases being analyzed and 
the types of determinations being requested began to increase in 
the late 1960's and early 1970's. One of the few review checks 
added was to compare analyses to insure that "total" values were 
greater than "dissolved" values, if both had been determined on 
the same sample. This check did not take precision into account 
and often either the dissolved or total analyses would be repeated 
until the data "looked better'' (while in reality the values were 
statistically and analytically the same). The semiannual SRWS 
program gradually added the determination of metals and today over 
40 major, nutrient, and trace constituents are included in this 
program, providing a measure of analytical precision.

During the 1960's and 1970's, analytical methodology began 
changing rapidly. However, adequate records of when analytical 
changes were initiated were not kept. Because of this lack of 
record, there are doubts about the meaning of some of the chemical 
data collected during that period. For example, the initial 
procedure for determining mercury detected only inorganic mercury. 
An oxidant later was added which meant that some organic mercury 
was being detected as well as the inorganic mercury. Still later, 
a second oxidant was added and yielded more organic mercury. The 
concentrations of the two oxidants then were changed several 
times, each change making a greater proportion of the organic 
mercury susceptible to detection. Since records were not kept on 
which data had been obtained by which analytical procedure, an 
apparent increase in mercury values during the early 1970's could 
be due to a real increase or might be due only to methodology 
changes; interpretation is nearly impossible.

Although a record of analytical methodology is still not part of 
the WATSTORE system, a record is being kept in the Central 
Laboratories System through the use of lab codes. Different lab 
codes, recorded in the "Water Quality Laboratory Services 
Catalog," are used for different methods so that if, in the 
future, it becomes important to know how a sample was analyzed 
and/or what the expected precision of the method used was, the 
data will be available on the Central Laboratories System tapes. 
Eventually, it is expected that such information will be stored in 
WATSTORE.

All of the quality-control procedures developed in the past are 
used today in the Central Laboratories System. Heavy reliance 
still is placed on correct preparation of standards and careful 
use of analytical techniques. The analytical review checks, based 
largely on the relationships developed in the early l900's, are 
still used; however, these checks now are done by means of a 
computer, and result in "error messages" for the laboratory's 
quality-control staff.

Participation in the SRWS program also continues, although the 
primary aim of that program now is to document multi-laboratory 
analytical precision. In addition, inorganic reference materials 
are used daily by the laboratory analysts to check their work; 
reference materials also are submitted as "unknowns" daily by the 
laboratory chief and weekly by District personnel (unknown to 
anyone within the Central Laboratories System). Log-in sheets 
accompanying all "unknown" reference materials are coded for 
computer recognition, and the central laboratories' quality-
control sections are notified of discrepancies between analyzed 
and expected values within a day of when the samples were 
analyzed. This l-day delay in quality-control results will be 
eliminated when computer-analytical instrument links are completed 
and such information becomes immediately available.

Until recently, efforts made within the USGS to document 
interlaboratory precision of methods had been rather limited. 
Within the past 2 years, data, primarily from the SRWS program, 
have been analyzed and precision statements for most inorganic 
methods have been developed and recorded in book 5, chapter Al, of 
the Techniques for Water-Resources Investigation (TWRI) series. 
Such statements of analytical precision are necessary for 
interpretation of data obtained by the methods. For the 
convenience of District personnel, the Water-Quality Laboratory 
Services Catalog gives an indication of method precision so that a 
method (lab code) with the required precision can be selected when 
an analysis is requested.

Presently, efforts are underway to revise the computer programs so 
that "good" quality-assurance data (less than 1.5 standard 
deviations from the expected value) from unknown reference 
materials as well as "erroneous" data (greater than 1.5 standard 
deviations from the expected value) are stored in the computer 
files. This change will make it possible to program the computer 
to prepare quality-control charts that will facilitate the 
detection of an increase in bias or growing lack of precision 
before the problem becomes serious.

Procedures for the quality assurance of organic analyses lag far 
behind those designed for inorganic analyses, largely because 
appropriate standard samples are not available. Although 
concentrated reference materials are available in ampoules for 
many organic compounds from the U.S. Environmental Protection 
Agency, dilute samples would be more useful as they could be 
introduced into laboratories as unknowns. Poor stability and 
adsorption onto sample container walls are only two of the 
problems expected to be encountered in preparing reference 
materials of organic compounds, especially since many organic 
compounds are formulated to be unstable so that they will not be 
long-term threats to the environment.

In February 1980, a reference sample for selected herbicides and 
insecticides was prepared in tap water. This sample is being 
analyzed weekly to obtain information on sample degradation and 
has been distributed to approximately 30 laboratories through the 
SRWS program to obtain interlaboratory comparison data. Although 
not all data have been collected, preliminary information 
indicates that the sample is uniform and the pesticides relatively 
stable. In the meantime, the two central water-quality 
laboratories must rely largely on accurate preparation of organic 
standards and proper calibration of instruments for quality 
control of organic analyses. Analytical confirmation with a mass 
spectrometer often is used on positive results and both 
laboratories participate in EPA's performance evaluation program.

Quality-control procedures also include collecting recovery data 
from analyses of "known" concentrations and analyzing some samples 
in duplicate. For example, routine tests are made of recoveries of 
standards after extraction and concentration and recoveries after 
interference clean-up procedures. Data on method bias now are 
being collected through these studies. Similarly, data on analyses 
of duplicate samples are being collected for pesticides in bottom 
materials. Because concentration differences between "duplicates" 
vary with compound concentrations, standard quality-control 
procedures which were developed for looking at duplicates in 
"production" processes are not appropriate. Alternatives to these 
procedures are being developed and, as soon as acceptable 
procedures are available, should be useful in monitoring the 
quality of data not only from the central water-quality 
laboratories but also from cooperator and contractor laboratories.

As is true for chemical analyses, proper training of personnel and 
careful use of analytical techniques play a large part in the 
quality control of both sediment and biological analyses. In 
addition, eight particle-size reference materials were prepared in 
1979 (Delaney and Schroder, 1979), and can be used to examine the 
comparability of data produced by WRD sediment laboratories and 
submitted periodically to the laboratories as quality assurance 
samples. The biology section of the Atlanta Central Laboratory 
maintains a reference specimen collection, monitors analyses "in-
house", and participates in a program involving the interchange of 
samples between the section and the contractor performing 
phytoplankton analyses.

Data from cooperator and contractor laboratories are used 
interchangeably with data from the WRD central water-quality 
laboratories. Thus, equivalent quality-assurance procedures must 
be applied to all laboratories providing water-quality data to the 
U.S. Geological Survey. Currently, a program to monitor the 
quality of data from non-USGS laboratories is under development; 
it is hoped that by the beginning of FY 1981 most of these 
laboratories will have become part of a USGS quality-assurance 
program.

Meanwhile, in FY 1979, an extensive program to monitor the quality 
assurance of field pH and specific conductance measurements was 
developed. Over 10,000 reference samples have been distributed to 
District personnel since this program began. It is intended that 
the program will expand so that the quality of other field 
determinations, such as alkalinity, will be monitored. In 
addition, development of a computer program which compares field 
and laboratory pH and specific conductance values is being 
completed. It is expected that this program soon will be 
distributed to WRD districts and that the districts will be able 
to use this program in a self-monitoring process so that on a 
weekly or monthly basis they can compare field values with 
laboratory values (which, it is recognized, may differ because of 
actual changes in the sample). This program is intended to "fill 
in" the gaps between the semiannual distribution of reference 
materials.

Another active area of quality assurance is the testing of 
materials (filters, bottles, and so forth) used in sample 
collection. For example, the 1978 contamination of lead and 
cadmium in samples preserved with nitric acid in ampoules 
indicated the need for an improved program to assure the quality 
of materials used for trace metal analyses. A procedure to combine 
standard single- and double-sampling methods (Dodge-Romig, 1959) 
was formulated and was used to develop a program to assure the 
quality of ampouled acid and polyethylene bottles.

Although much work remains to be done, quality-assurance programs 
are undergoing rapid development. The need for the capability to 
compare data from samples presently being collected at site A by 
observer B which are analyzed by method C in laboratory D with 
data from samples collected ten years from now at site W by 
observer X and analyzed by method Y in laboratory Z clearly makes 
development of such programs of paramount importance.

REFERENCES

Delaney, B. M., and Schroder, L. J., 1979, Preparation of 
reference materials for particle-size analyses of silts and clays: 
U.S. Geological Survey Open-File Report 79-1590, 14 p.

Dodge, Harold F., and Romig, Harry G., 1959, Sampling inspection 
tables, single and double sampling, second edition: New York, John 
Wiley & Sons, Inc., 224 p.

Durum, W. H., 1978, Historical profile of quality of water 
laboratories and activities, 1879-1973: U.S. Geological Survey 
Open-File Report 78-432, 235 p.

Howard, C. S., 1933, Determination of total dissolved solids in 
water analyses: Industrial and Engineering Chemistry, v. 5, no. 1, 
p. 4-6.

Skougstad, Marvin W., and Fishman, Marvin J., 1975, Standard 
reference water samples: Proceedings American Water Works 
Association Water-Quality Technology Conference, December, 1974, 
p. XIX-l - p. XIX-6.