Tedmund M. Struzeski 20250319 1 spreadsheet https://doi.org/10.5066/P1BRC2GJ Tedmund M. Struzeski 20250401 draft publication The U.S. Geological Survey evaluated the stability of water-sample chemical analysis of nutrient, alkalinity, and acid neutralizing capacity constituents with respect to the duration between sample collection and laboratory analysis, also known as sample holding times. Included in this data release are results used to evaluate the stability of the chemical properties alkalinity (as calcium carbonate [CaCO3]), filtered; acid neutralizing capacity (as CaCO3), unfiltered; total ammonia (NH3) as nitrogen (N), filtered; total NH3 plus organic nitrogen as N, filtered and unfiltered; nitrite (NO2-) as N, filtered; nitrate (NO3-) plus NO2- as N, filtered; total N, filtered and unfiltered; orthophosphate (PO4-3) as phosphorous (P), filtered; and total P as P, (filtered and unfiltered) in water over holding times ranging between 2 and 180 days. In addition, graphs used for the study as well as blind sample results from the USGS Quality Systems Branch-Inorganic Blind Sample Project are included in this data release. Data for the hold time study (HTS) conducted in 2024 by the USGS Water Mission Area, Laboratory Analytical Services Division, Quality Systems Branch, in collaboration with the HTS team are presented. The results pertain specifically to samples collected by the USGS and analyzed by the National Water Quality Laboratory (NWQL). Wide application of the HTS results outside of the USGS is not intended. The results may not necessarily be applicable to samples collected, handled, and analyzed by methods that differ from those of the NWQL. The date range specified includes all data assessed at some point while developing this study even if some of those data were not directly used in the final report. 20211001 20241201 observed Complete None planned United States -125.5078 -67.8516 49.1530 24.2069 ISO 19115 Topic Category inlandWaters None water sample stability chemical analysis quality assessment quality assurance hold time nutrients USGS Thesaurus chemical analysis USGS Metadata Identifier USGS:6786eeacd34e60ddd4de2296 None. Please see 'Distribution Info' for details. None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Tedmund M. Struzeski USGS Chemist mailing and physical

Denver Federal Center, MS401, Bldg. 95

Denver CO 80225 USA 303.236.1872 struzesk@usgs.gov WIndows 11, Microsoft Excel 365, DR_Blank_All_Obs_Ppties.txt, DR_HoldTimeStudy_Main_table.txt, DR_SiteLocations.txt, DR_StandardRef_All_Obs_Ppties.txt Industry standard quality control measures were used for the analytical results. All data are logically consistent with expectations. Sample data are for water samples collected within the continental United States. Sample data are for five surface-water samples and one groundwater sample both collected in fall 2023. Quality assessment data represent National Water Quality Laboratory analytical performance on environmental waters. Not applicable Not applicable Regarding DR_HoldTimeStudy_Main_table.txt; Laboratory_Result_(uncensored). Samples were collected according to the U.S. Geological Survey National Field Manual (variously dated [book 9 chaps A1-A9 (variously paged)]). Results were generated by the National Water Quality Laboratory using the methodologies shown below. For each site, samples were analyzed at six or seven time intervals between approximately 2 and 180 after sampling. Each analysis compromised of the mean of three separate analyses (triplicate) from three separate bottles. Results were hand-entered into a shared spreadsheet. Data not publicly available via NWIS (U.S. Geological Survey, USGS water data for the Nation: U.S. Geological Survey National Water Information System database 1) Observed property: Alkalinity as CaCO3, water, fltd, fixed EP (pH 4.5) titr, lab; USGS method: I-2030-89; Reference: Fishman. M. J. and Friedman, L.C., 1989, Methods for determination of inorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water-Resources Investigations, book 5, chap. A1, 545 p 2) Observed property: ANC as CaCO3, water, unfltd, fixed EP (pH 4.5) titr, lab; USGS method: I-2030-89; Reference: Fishman. M. J. and Friedman, L.C., 1989, Methods for determination of inorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water-Resources Investigations, book 5, chap. A1, 545 p 3) Observed property: Total ammonia as N, water, fltd; USGS method: I-2522-90, Reference: Fishman. M. J., ed., 1993; Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey-Open File Report 93-125, 217 p. 4) Observed property: Total ammonia + organic nitrogen as N, water, fltd; USGS method: I-2515-91; Reference: Patton, C.J., and Truitt, E.P., 2000, methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of ammonium plus organic nitrogen by Kjeldahl digestion method and an automated photometric finish that includes digest cleanup by gas diffusion: U.S. Geological Survey-Open File Report 00-170, 31 p. 5) Observed property: Total ammonia + organic nitrogen as N, water, unfltd; USGS method: I-4515-91; Reference: Patton, C.J., and Truitt, E.P., 2000, methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of ammonium plus organic nitrogen by Kjeldahl digestion method and an automated photometric finish that includes digest cleanup by gas diffusion: U.S. Geological Survey-Open File Report 00-170, 31 p. 6) Observed property: Nitrite as N, water, fltd; USGS method: I-2540-90; Reference: Fishman. M. J., ed., 1993; Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey-Open File Report 93-125, 217 p. 7) Observed property: Nitrate + nitrite as N, water, fltd; USGS method: I-2548-11; Reference: Patton, C.J., and Kryskalla, J.R., 2011, colorimetric determination of nitrate plus nitrite and water bite in somatic reduction, automated discrete analyzer methods: U.S. Geological Survey techniques and methods, book 5, chapter. B8. 8) Observed property: Total nitrogen as N, water, fltd; USGS method: I-2650-03; Reference: Patton, C.J., and Kryskalla, J.R., Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Evaluation of Alkaline Persulfate Digestion as an alternative to Kjeldahl Digestion for Determination of Total and Dissolved Nitrogen and Phosphorus in Water, Water-Resources Investigations Report 03-4174, 33 p. 9) Observed property: Total nitrogen as N, water, unfltd; USGS method: I-4650-03; Reference: Patton, C.J., and Kryskalla, J.R., Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Evaluation of Alkaline Persulfate Digestion as an alternative to Kjeldahl Digestion for Determination of Total and Dissolved Nitrogen and Phosphorus in Water, Water-Resources Investigations Report 03-4174, 33 p. 10) Observed property: Orthophosphate as P, water, fltd; USGS method: I-2601-90; Reference: Fishman. M. J., ed., 1993; Methods of analysis by the U.S . Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey-Open File Report 93-125, 217 p. 11) Observed property: Phosphorus as P, water, fltd; USGS method: I-2610-91; Reference: Patton, C.J., and Truitt, E.P., 1992, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Determination of total phosphors by a Kjeldahl digestion method and automated colorimetric finish that includes dialysis: U.S. Geological Survey-Open File Report 92-146, 39 p. 12) Observed property: Phosphorus as P, water, unfltd; USGS method: I-4610-91; Reference: Patton, C.J., and Truitt, E.P., 1992, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Determination of total phosphors by a Kjeldahl digestion method and automated colorimetric finish that includes dialysis: U.S. Geological Survey-Open File Report 92-146, 39 p. N/A 20241219 N/A Tedmund M. Struzeski USGS Chemist mailing and physical

MS401, Bldg. 95, Denver Federal Center

Denver CO 80225 USA 303.236.1872 struzesk@usgs.gov Regarding DR_Blank_All_Obs_Ppties.txt; Laboratory_Result_(uncensored). Results were generated by the National Water Quality Laboratory using the methodologies shown below. 1) Observed property: Alkalinity as CaCO3, water, fltd, fixed EP (pH 4.5) titr, lab; USGS method: I-2030-89; Reference: Fishman. M. J. and Friedman, L.C., 1989, Methods for determination of inorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water-Resources Investigations, book 5, chap. A1, 545 p 2) Observed property: ANC as CaCO3, water, unfltd, fixed EP (pH 4.5) titr, lab; USGS method: I-2030-89; Reference: Fishman. M. J. and Friedman, L.C., 1989, Methods for determination of inorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water-Resources Investigations, book 5, chap. A1, 545 p 3) Observed property: Total ammonia as N, water, fltd; USGS method: I-2522-90, Reference: Fishman. M. J., ed., 1993; Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey-Open File Report 93-125, 217 p. 4) Observed property: Total ammonia + organic nitrogen as N, water, fltd; USGS method: I-2515-91; Reference: Patton, C.J., and Truitt, E.P., 2000, methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of ammonium plus organic nitrogen by Kjeldahl digestion method and an automated photometric finish that includes digest cleanup by gas diffusion: U.S. Geological Survey-Open File Report 00-170, 31 p. 5) Observed property: Total ammonia + organic nitrogen as N, water, unfltd; USGS method: I-4515-91; Reference: Patton, C.J., and Truitt, E.P., 2000, methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of ammonium plus organic nitrogen by Kjeldahl digestion method and an automated photometric finish that includes digest cleanup by gas diffusion: U.S. Geological Survey-Open File Report 00-170, 31 p. 6) Observed property: Nitrite as N, water, fltd; USGS method: I-2540-90; Reference: Fishman. M. J., ed., 1993; Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey-Open File Report 93-125, 217 p. 7) Observed property: Nitrate + nitrite as N, water, fltd; USGS method: I-2548-11; Reference: Patton, C.J., and Kryskalla, J.R., 2011, colorimetric determination of nitrate plus nitrite and water bite in somatic reduction, automated discrete analyzer methods: U.S. Geological Survey techniques and methods, book 5, chapter. B8. 8) Observed property: Total nitrogen as N, water, fltd; USGS method: I-2650-03; Reference: Patton, C.J., and Kryskalla, J.R., Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Evaluation of Alkaline Persulfate Digestion as an alternative to Kjeldahl Digestion for Determination of Total and Dissolved Nitrogen and Phosphorus in Water, Water-Resources Investigations Report 03-4174, 33 p. 9) Observed property: Total nitrogen as N, water, unfltd; USGS method: I-4650-03; Reference: Patton, C.J., and Kryskalla, J.R., Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Evaluation of Alkaline Persulfate Digestion as an alternative to Kjeldahl Digestion for Determination of Total and Dissolved Nitrogen and Phosphorus in Water, Water-Resources Investigations Report 03-4174, 33 p. 10) Observed property: Orthophosphate as P, water, fltd; USGS method: I-2601-90; Reference: Fishman. M. J., ed., 1993; Methods of analysis by the U.S . Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey-Open File Report 93-125, 217 p. 11) Observed property: Phosphorus as P, water, fltd; USGS method: I-2610-91; Reference: Patton, C.J., and Truitt, E.P., 1992, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Determination of total phosphors by a Kjeldahl digestion method and automated colorimetric finish that includes dialysis: U.S. Geological Survey-Open File Report 92-146, 39 p. 12) Observed property: Phosphorus as P, water, unfltd; USGS method: I-4610-91; Reference: Patton, C.J., and Truitt, E.P., 1992, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Determination of total phosphors by a Kjeldahl digestion method and automated colorimetric finish that includes dialysis: U.S. Geological Survey-Open File Report 92-146, 39 p. https://qsb.usgs.gov/ibsp/charts.php--Blind blanks 20241219 Inorganic Blind Sample Project website: https://qsb.usgs.gov/ibsp/charts.php; accessed 07/03/2024-07/11/204, 10/23/2024, and 02/11/2025 Tedmund M. Struzeski USGS Chemist mailing and physical

MS401, Bldg. 95, Denver Federal Center

Denver CO 80225 USA 303.236.1872 Regarding DR_StandardRef_All_Obs_Ppties.txt. Results derived from data originally generated at the National Water Quality Laboratory using the methodologies shown below. 1) Observed property: Alkalinity as CaCO3, water, fltd, fixed EP (pH 4.5) titr, lab; USGS method: I-2030-89; Reference: Fishman. M. J. and Friedman, L.C., 1989, Methods for determination of inorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water-Resources Investigations, book 5, chap. A1, 545 p 2) Observed property: ANC as CaCO3, water, unfltd, fixed EP (pH 4.5) titr, lab; USGS method: I-2030-89; Reference: Fishman. M. J. and Friedman, L.C., 1989, Methods for determination of inorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water-Resources Investigations, book 5, chap. A1, 545 p 3) Observed property: Total ammonia as N, water, fltd; USGS method: I-2522-90, Reference: Fishman. M. J., ed., 1993; Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey-Open File Report 93-125, 217 p. 4) Observed property: Total ammonia + organic nitrogen as N, water, fltd; USGS method: I-2515-91; Reference: Patton, C.J., and Truitt, E.P., 2000, methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of ammonium plus organic nitrogen by Kjeldahl digestion method and an automated photometric finish that includes digest cleanup by gas diffusion: U.S. Geological Survey-Open File Report 00-170, 31 p. 5) Observed property: Total ammonia + organic nitrogen as N, water, unfltd; USGS method: I-4515-91; Reference: Patton, C.J., and Truitt, E.P., 2000, methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of ammonium plus organic nitrogen by Kjeldahl digestion method and an automated photometric finish that includes digest cleanup by gas diffusion: U.S. Geological Survey-Open File Report 00-170, 31 p. 6) Observed property: Nitrite as N, water, fltd; USGS method: I-2540-90; Reference: Fishman. M. J., ed., 1993; Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey-Open File Report 93-125, 217 p. 7) Observed property: Nitrate + nitrite as N, water, fltd; USGS method: I-2548-11; Reference: Patton, C.J., and Kryskalla, J.R., 2011, colorimetric determination of nitrate plus nitrite and water bite in somatic reduction, automated discrete analyzer methods: U.S. Geological Survey techniques and methods, book 5, chapter. B8. 8) Observed property: Total nitrogen as N, water, fltd; USGS method: I-2650-03; Reference: Patton, C.J., and Kryskalla, J.R., Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Evaluation of Alkaline Persulfate Digestion as an alternative to Kjeldahl Digestion for Determination of Total and Dissolved Nitrogen and Phosphorus in Water, Water-Resources Investigations Report 03-4174, 33 p. 9) Observed property: Total nitrogen as N, water, unfltd; USGS method: I-4650-03; Reference: Patton, C.J., and Kryskalla, J.R., Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Evaluation of Alkaline Persulfate Digestion as an alternative to Kjeldahl Digestion for Determination of Total and Dissolved Nitrogen and Phosphorus in Water, Water-Resources Investigations Report 03-4174, 33 p. 10) Observed property: Orthophosphate as P, water, fltd; USGS method: I-2601-90; Reference: Fishman. M. J., ed., 1993; Methods of analysis by the U.S . Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey-Open File Report 93-125, 217 p. 11) Observed property: Phosphorus as P, water, fltd; USGS method: I-2610-91; Reference: Patton, C.J., and Truitt, E.P., 1992, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Determination of total phosphors by a Kjeldahl digestion method and automated colorimetric finish that includes dialysis: U.S. Geological Survey-Open File Report 92-146, 39 p. 12) Observed property: Phosphorus as P, water, unfltd; USGS method: I-4610-91; Reference: Patton, C.J., and Truitt, E.P., 1992, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory, Determination of total phosphors by a Kjeldahl digestion method and automated colorimetric finish that includes dialysis: U.S. Geological Survey-Open File Report 92-146, 39 p. https://qsb.usgs.gov/ibsp/charts.php--Percent RSD 20241219 Inorganic Blind Sample Project website: https://qsb.usgs.gov/ibsp/charts.php; accessed 07/03/2024-07/11/204, 10/23/2024, and 02/11/2025 Tedmund M. Struzeski USGS Chemist mailing and physical

MS401, Bldg. 95, Denver Federal Center

Denver CO 80225 303.236.1872 DR_Blank_All_Obs_Ppties.txt Data used to determine limits based on blind blank sample results analyzed by the National Water Quality Laboratory. Producer Defined Parameter_Description Parameter description is the National Water Information System (NWIS) long name which is the analyte long name with additional descriptors for the parameter given in the USGS NWIS Parameter Code Definition File (see https://waterdata.usgs.gov/code-dictionary/) Producer Defined Alkalinity, water, filtered, fixed endpoint (pH 4.5) titration, laboratory, milligrams per liter as calcium carbonate Alkalinity, water, filtered, fixed endpoint (pH 4.5) titration, laboratory, milligrams per liter as calcium carbonate Producer defined Acid neutralizing capacity, water, unfiltered, fixed endpoint (pH 4.5) titration, laboratory, milligrams per liter as calcium carbonate Acid neutralizing capacity, water, unfiltered, fixed endpoint (pH 4.5) titration, laboratory, milligrams per liter as calcium carbonate Producer defined Ammonia (NH3 + NH4+), water, filtered, milligrams per liter as nitrogen Ammonia (NH3 + NH4+), water, filtered, milligrams per liter as nitrogen Producer defined Ammonia plus organic nitrogen, water, filtered, milligrams per liter as nitrogen Ammonia plus organic nitrogen, water, filtered, milligrams per liter as nitrogen Producer defined Ammonia plus organic nitrogen, water, unfiltered, milligrams per liter as nitrogen Ammonia plus organic nitrogen, water, unfiltered, milligrams per liter as nitrogen Producer defined Nitrite, water, filtered, milligrams per liter as nitrogen Nitrite, water, filtered, milligrams per liter as nitrogen Producer defined Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen Producer defined Total nitrogen [nitrate + nitrite + ammonia + organic-N], water, filtered, analytically determined, milligrams per liter Total nitrogen [nitrate + nitrite + ammonia + organic-N], water, filtered, analytically determined, mg/L Producer defined Total nitrogen [nitrate + nitrite + ammonia + organic-N], water, unfiltered, analytically determined, milligrams per liter Total nitrogen [nitrate + nitrite + ammonia + organic-N], water, unfiltered, analytically determined, mg/L Producer defined Orthophosphate, water, filtered, milligrams per liter as phosphorus Orthophosphate, water, filtered, milligrams per liter as phosphorus Producer defined Phosphorus, water, filtered, milligrams per liter as phosphorus Phosphorus, water, filtered, milligrams per liter as phosphorus Producer defined Phosphorus, water, unfiltered, milligrams per liter as phosphorus Phosphorus, water, unfiltered, milligrams per liter as phosphorus Producer defined Parameter_Code National Water Information System (NWIS) parameter codes are 5-digit codes used to identify the constituent measured and the units of measure Producer Defined 00608 90410 Method_Code A unique identifier that maps to one or more parameter codes indicating use of a specific analytical methodology Producer Defined AKP01 TT040 Lab_Code Lab code is the National Water Quality Laboratory (NWQL) code defining the test applied to the combination of analyte, sample type, sample preservation, and analytical method that produced the laboratory result Producer Defined 70 3157 Analysis_Date Date laboratory analysis was performed for given Laboratory Result (uncensored) Producer Defined 10-6-2021 6-17-2024 Dates Day Laboratory_Result_(uncensored) Concentration in milligrams per liter (mg/L) Producer Defined -0.079 2.6728 Units Units of chemical concentration Producer Defined mg/L milligrams per liter Producer defined DR_StandardRef_All_Obs_Ppties.txt Data used to determine limits based on blind sample results of Standard Reference Samples analyzed by the National Water Quality Laboratory. Producer Defined Parameter_Description Parameter description is the National Water Information System (NWIS) long name which is the analyte long name with additional descriptors for the parameter given in the USGS NWIS Parameter Code Definition File (see https://waterdata.usgs.gov/code-dictionary/) Producer Defined Alkalinity, water, filtered, fixed endpoint (pH 4.5) titration, laboratory, milligrams per liter as calcium carbonate Alkalinity, water, filtered, fixed endpoint (pH 4.5) titration, laboratory, milligrams per liter as calcium carbonate Producer defined Acid neutralizing capacity, water, unfiltered, fixed endpoint (pH 4.5) titration, laboratory, milligrams per liter as calcium carbonate Acid neutralizing capacity, water, unfiltered, fixed endpoint (pH 4.5) titration, laboratory, milligrams per liter as calcium carbonate Producer defined Ammonia (NH3 + NH4+), water, filtered, milligrams per liter as nitrogen Ammonia (NH3 + NH4+), water, filtered, milligrams per liter as nitrogen Producer defined Ammonia plus organic nitrogen, water, filtered, milligrams per liter as nitrogen Ammonia plus organic nitrogen, water, filtered, milligrams per liter as nitrogen Producer defined Ammonia plus organic nitrogen, water, unfiltered, milligrams per liter as nitrogen Ammonia plus organic nitrogen, water, unfiltered, milligrams per liter as nitrogen Producer defined Nitrite, water, filtered, milligrams per liter as nitrogen Nitrite, water, filtered, milligrams per liter as nitrogen Producer defined Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen Producer defined Total nitrogen [nitrate + nitrite + ammonia + organic-N], water, filtered, analytically determined, mg/L Total nitrogen [nitrate + nitrite + ammonia + organic-N], water, filtered, analytically determined, mg/L Producer defined Total nitrogen [nitrate + nitrite + ammonia + organic-N], water, unfiltered, analytically determined, mg/L Total nitrogen [nitrate + nitrite + ammonia + organic-N], water, unfiltered, analytically determined, mg/L Producer defined Orthophosphate, water, filtered, milligrams per liter as phosphorus Orthophosphate, water, filtered, milligrams per liter as phosphorus Producer defined Phosphorus, water, filtered, milligrams per liter as phosphorus Phosphorus, water, filtered, milligrams per liter as phosphorus Producer defined Phosphorus, water, unfiltered, milligrams per liter as phosphorus Phosphorus, water, unfiltered, milligrams per liter as phosphorus Producer defined Parameter_Code National Water Information System (NWIS) parameter codes are 5-digit codes used to identify the constituent measured and the units of measure Producer Defined 00608 90410 Method_Code A unique identifier that maps to one or more parameter codes indicating use of a specific analytical methodology Producer Defined AKP01 TT040 Lab_Code Lab code is the National Water Quality Laboratory (NWQL) code defining the test applied to the combination of analyte, sample type, sample preservation, and analytical method that produced the laboratory result Producer Defined 70 3157 Blind_Sample_ID Identification of reference material used (as determined by the USGS Standard Reference Sample [SRS] Project) Producer Defined --- No data available Producer defined Identification of reference material used (as determined by the USGS Standard Reference Sample [SRS] Project) Mean Calculated mean value of multiple results used to calculate Percent Relative Standard Deviation (Percent RSD) Producer Defined --- No data available Producer defined Mean value calculated from multiple results from blind samples analyzed at the National Water Quality Laboratory for a given Blind Sample ID. Used to calculate Percent Relative Standard Deviation (Percent RSD). Standard_Deviation Calculated standard deviation value of multiple results used to calculate Percent Relative Standard Deviation (Percent RSD) Producer Defined --- No data available Producer defined Standard deviation calculated from multiple results from blind samples analyzed at the National Water Quality Laboratory for a given Blind Sample ID. Used to calculate Percent Relative Standard Deviation (Percent RSD). Percent_RSD Percent Relative Standard Deviation (Percent RSD) Producer Defined --- No data available Producer defined Percent Relative Standard Deviation (Percent RSD) calculated by dividing Standard Deviation by Mean then multiplying by 100 Number_of_Observations Number of values for given Blind Sample ID used to compute Mean, Standard Deviation, and Percent RSD Producer Defined --- No data available Producer defined Number of values for given Blind Sample ID used to compute Mean, Standard Deviation, and Percent RSD Units Units of chemical concentration Producer Defined --- No data Producer defined mg/L milligrams per liter Producer defined --- No data Producer defined DR_SiteLocations.txt Site information for each hold-time study sample number Producer Defined Hold_time_study_ID_number The Hold-time Study sample identification number for the samples specific to this study Producer Defined 1 6 State State Producer Defined State Site_number Site identification number used in the National Water Information System (NWIS) Producer Defined 1193050 375327097285401 Station_name Station name used in the National Water Information System (NWIS) Producer Defined Station name used in the National Water Information System (NWIS) Site_type Specifies if the sample type is surface water or groundwater Producer Defined SW Surface Water Producer defined GW Groundwater Producer defined Date Date sample was collected Producer Defined 11-13-2023 12-04-2023 Time Time sample was collected Producer Defined 0930 1220 Latitude Latitude Producer Defined 37.67601249 45.51750000 Longitude Longitude Producer Defined -122.66916670 -72.55314540 DR_HoldTimeStudy_Main_table.txt Dataset used to create percent recovery charts and control charts. Within this file are included individual analytical results, mean values of triplicate results, and (control) limits used outside of which indicate sample instability. Producer Defined Hold_time_study_ID_number The Hold-time Study sample identification number for the samples specific to this study Producer Defined 1 6 Observed_property A description of discrete sample data designed to be understood within and outside of the U.S Geological Survey. Producer Defined ANC as CaCO3, water, unfltd, fixed EP (pH 4.5) titr, lab Acid neutralizing capacity, water, unfiltered, fixed endpoint (pH 4.5) titration, laboratory, milligrams per liter as calcium carbonate Producer defined Phosphorus as P, water, fltd Phosphorus, water, filtered, milligrams per liter as phosphorus Producer defined Phosphorus as P, water, unfltd Phosphorus, water, unfiltered, milligrams per liter as phosphorus Producer defined Total ammonia + organic nitrogen as N, water, fltd Ammonia plus organic nitrogen, water, filtered, milligrams per liter as nitrogen Producer defined Total ammonia + organic nitrogen as N, water, unfltd Ammonia plus organic nitrogen, water, unfiltered, milligrams per liter as nitrogen Producer defined Alkalinity as CaCO3, water, fltd, fixed EP (pH 4.5) titr, lab Alkalinity, water, filtered, fixed endpoint (pH 4.5) titration, laboratory, milligrams per liter as calcium carbonate Producer defined Total nitrogen as N, water, fltd Total nitrogen [nitrate + nitrite + ammonia + organic-N], water, filtered, analytically determined, mg/L Producer defined Total nitrogen as N, water, unfltd Total nitrogen [nitrate + nitrite + ammonia + organic-N], water, unfiltered, analytically determined, mg/L Producer defined Total ammonia as N, water, fltd Ammonia (NH3 + NH4+), water, filtered, milligrams per liter as nitrogen Producer defined Nitrite as N, water, fltd Nitrite, water, filtered, milligrams per liter as nitrogen Producer defined Orthophosphate as P, water, fltd Orthophosphate, water, filtered, milligrams per liter as phosphorus Producer defined Nitrate + nitrite as N, water, fltd Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen Producer defined Duration_(days) Assigned bin related to number of days between sampling date and analysis date (may not equal actual days) Producer Defined 2 180 days Actual_Duration_(days) Actual number of days between sampling date and analysis date Producer Defined 1 94 days Laboratory_Result_(uncensored) Concentration in milligrams per liter (mg/L) Producer Defined -0.038 1275.90 miligrams per liter Mean_of_Triplicates Mean concentration in milligrams per liter (mg/L) Producer Defined -0.034 1273.93 miligrams per liter Percent_Recovery Percent recovery relative to mean value for Duration (days) = 2 Producer Defined -300.0 1144.7 Percent Replicate_Number Samples were analyzed in triplicate. This number represents the unique identifier within that batch of triplicates Producer Defined 1 3 Upper_stability_limit Largest value allowed before result is considered to have come from an instable sample matrix. Value is equal to "Mean_of_Triplicates" plus a variability value. The variability value is determined from blind-blank variability, SRS (Standard Reference Sample) variability, or 10% of "mean_of_triplicates," whichever is greater. Blind-blank variability = MDL calculated from blind-blank data (see DR_Blank_All_Obs_Ppties.txt). SRS variability = 2X SD from SRS data (see DR_StandardRef_All_Obs_Ppties.txt). Producer Defined 0.001 1401.33 Lower_stability_limit Smallest value allowed before result is considered to have come from an instable sample matrix. Value is equal to "Mean_of_Triplicates" plus a variability value. The variability value is determined from blind-blank variability, SRS (Standard Reference Sample) variability, or 10% of "mean_of_triplicates," whichever is greater. Blind-blank variability = MDL calculated from blind-blank data (see DR_Blank_All_Obs_Ppties.txt). SRS variability = 2X SD from SRS data (see DR_StandardRef_All_Obs_Ppties.txt). Producer Defined -0.088 1146.54 Parameter_Code National Water Information System (NWIS) parameter codes are 5-digit codes used to identify the constituent measured and the units of measure Producer Defined 00608 90410 Method_Code A unique identifier that maps to one or more parameter codes indicating use of a specific analytical methodology Producer Defined Values in this field indicate a unique identifier that maps to one or more parameter codes indicating use of a specific analytical methodology Laboratory_Code Lab code is the National Water Quality Laboratory (NWQL) code defining the test applied to the combination of analyte, sample type, sample preservation, and analytical method that produced the laboratory result Producer Defined 70 3157 Units Units of chemical concentration Producer Defined mg/L milligrams per liter Producer defined These data sets were used to create all values found in all tables and graphs in the Open File Report, "Evaluation of Nutrient, Alkalinity, and Acid Neutralizing Capacity Stabilities in Water Samples Analyzed by the National Water Quality Laboratory." Analytical results from the study can be found in "DR_HTS Main table." Data used to compute stability limits based on blanks can be found in "DR_BB_All Obs Ppties." Data used to compute stability limits based on Standard Reference Samples can be found in DR_SRS_All Obs Ppties. . Tedmund M Struzeski USGS - WATER Chemist mailing and physical

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Lakewood CO 80225 303-236-1872 struzesk@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Digital Data https://doi.org/10.5066/P1BRC2GJ None 20250324 Tedmund M Struzeski USGS - WATER Chemist mailing and physical

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Lakewood CO 80225 303-236-1872 struzesk@usgs.gov FGDC Biological Data Profile of the Content Standard for Digital Geospatial Metadata FGDC-STD-001.1-1999