PUBLICATIONS--Policy on Publishing Constituents with Both Field and Laboratory Values
In Reply Refer To: January 22, 1982
EGS-Mail Stop 412
QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM No. 82.06
Subject: PUBLICATIONS--Policy on Publishing Constituents
with Both Field and Laboratory Values
Quality of Water Branch Technical Memorandum No. 81.04
assigned WATSTORE parameter codes to laboratory measurements
of pH, specific conductance, and alkalinity. In addition,
codes were assigned for hydroxide, carbonate, bicarbonate,
and carbonate alkalinity measurements by incremental
titration and fixed-pH endpoint titration in the field and
laboratory.
Several questions have been raised recently as to the policy
on publication and storage of these data. The purpose of this
memorandum is to provide such policy guidance.
Some background information may help explain the guidelines
given below. Parameter codes were assigned to laboratory
values of pH, specific conductance, and alkalinity so that
both field and laboratory values could be stored without
ambiguity as to source. Until this action was taken,
laboratory measurements could be, and often were, substituted
under the same parameter code for questionable field values
in publications and data storage. As was stated in Quality of
Water Branch Technical Memorandum 73.02, the U.S. Geological
Survey considers the field value to be the better of the two
since changes in these characteristics can occur in transit
to the laboratory. Substituting laboratory values for field
values both obscures the source of the data and incurs the
risk that one incorrect value will be replaced by another.
The only unambiguous action that can be taken when both
laboratory and field values are available for the same
measurement is to store both under separate parameter codes.
After the decision was made to store both field and
laboratory values, appropriate STORET parameter codes were
sought. In this exercise we encountered some conflicts. In
particular, STORET code 00094, Specific Conductance, Field,
seemed to be the appropriate code under which to store field
specific conductance values. Historically, however, the
Geological Survey has stored the "best value," based on the
judgement of the observer, under code 00095, Specific
Conductance, per STORET instructions. Because of this
practice the file contains both laboratory and field values
stored under this code. It would be impractical and extremely
confusing to both ourselves and EPA to separate the huge
number of field and laboratory values now stored under code
00095 and restore the field value under 00094. But it was
clear that the practice of substituting a laboratory value
for a questionable field value should cease.
Therefore, it was desided to create a 90000-series code
(90095) for laboratory specific conductance and continue to
use code OOO95 for storage of field values. Since the title
for STORET code 00095 does not explicitly state field or
laboratory and, by accepted EPA usage, this code has been
assumed to represent "best value," its use by the Geological
Survey conforms to EPA's intent.
Codes for both field and laboratory pH were available in
STORET and they did not conflict with present usage. Thus,
use of code 00400 continues for field pH and 00403 for
laboratory pH.
In the case of alkalinity, no STORET code specifying
laboratory analysis existed and again, a 90000-series code
(90410) was assigned.
As directed in Quality of Water 8ranch Technical Memorandum
80.27, after October 1, 1980, the incremental titration
method of Barnes (1964), a new description of which was
transmitted under Quality of Water Branch Technical
Memorandum 82.05, is the only acceptable method for
determination of the individual chemical species carbonate
and bicarbonate. This policy was intended to stop the use of
the fixed-pH endpoint method for all carbonate species-
related measurements except alkalinity (00410 or 90410),
which continues to be measured by acid titration to pH 4.5.
It was also intended that the values of the measurements
discussed that were in storage before October 1, 1980,
eventually be identified as to method and source (field or
lab) and be reassigned to parameter codes identifying both
method and source. Quality of Water Branch Technical
Memorandum 81.04 assigned parameter codes for this purpose.
To avoid a great deal of work and expense that would be
involved in reassigning codes for hydroxide, carbonate,
bicarbonate, and carbonate alkalinity to existing data in the
historic file, the old codes, namely 71830, 00445, 00440 and
00430 were retained but were identified as field
determinations by the fixed-pH endpoint method. Except in
rare cases, no data were to be entered under these codes
after October 1, 1980. Values obtained by the accepted method
(incremental titration in the field) are to be entered under
codes 99830, 99445, 99440 and 99430 until acceptable new
STORET codes can be obtained from EPA. In addition, 90000-
series codes were assigned to hold values from the historic
record obtained in laboratories by either the incremental
titration method or the fixed-pH endpoint method. No current
data should be stored under these codes because the National
Water Quality Laboratories stopped measuring these
constituents in 1978. The intention here was that districts
could identify historic data stored under the old codes that
had been obtained by methods other than fixed-pH endpoint in
the field and shift those data to one of the appropriate new
90000-series codes.
The guidelines on publication given here are based on our
belief that the field measurements of pH, specific
conductance, alkalinity, hydroxide, carbonate, bicarbonate,
and carbonate alkalinity, when done correctly, are the best
measurements available and should be given priority in
publication and transferral to the STORET data base.
Guidelines for publication and storage are as follows:
1. Under no circumstances will laboratory values be
substituted for field values or vice versa in either the data
files or data publications.
2. When both field and laboratory values are available, the
field value will be published in preference to the laboratory
value unless there is reason to suspect the quality of the
field measurement.
3. When the field value is unavailable or questionable, the
laboratory value may be published.
4. Only values of hydroxide, carbonate, bicarbonate, and
carbonate alkalinity obtained in the field by the incremental
titration method will be published. Rare exceptions have been
allowed by written permission of the Assistant Chief
Hydrologist for Research and Technical Coordination for
projects locked into the field fixed-pH endpoint method.
These values may be published in a column suitably labeled
"field, fixed-pH endpoint." Transferral of these data to
STORET must await appropriate STORET codes from EPA. Note
that publication and storage of alkalinity measurements in
the field (00410) and laboratory (90410) are governed by
guidelines 1, 2, and 3.
To assist in the WY 1981 data reports, the column headings
from the tabling program for codes 90095, 90410 and 00403
have been made to read "laboratory"; headings for codes
99830, 99445, 99440 and 99430 have been made to read "field,
incremental titration."
R. J. Pickering
Chief, Quality of Water Branch
This memorandum supersedes Quality of Water Branch Technical
Memorandum 73.02 and supplements Quality of Water Branch
Technical Memorandums 80.27 and 81.04.
Key words: water quality, publications, publication policy,
WATSTORE, parameter codes
WRD Distribution: A, B, S, FO, PO