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