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Evaluation of preservation techniques for trace metals and major cations for surface waters collected from the U.S. Geological Survey's National Water Quality Network Sites

Metadata Updated: July 6, 2024

The USGS National Field Manual (NFM) states “A representative sample is one that typifies in time and space that part of the aqueous system to be studied” and “obtaining representative samples is of primary importance for a relevant description of the environment.” The NFM contains detailed chapters on the best practices for representative and contamination free sampling of major and trace metals (U.S. Geological Survey 2006). However, as analytical capabilities have advanced and new preservation methods developed, there is a need to study the effectiveness of various amounts of nitric acid preservation for trace metals and major cations in surface water and groundwater. The amount of nitric acid prescribed by the NFM for the preservation of cations and trace metals (0.4% v/v concentrated nitric acid, see attachment 1; U.S. Geological Survey 2002) is lower than some other commonly used methods (e.g., 1% v/v concentrated nitric acid). Furthermore, the NFM calls for the final sample pH to be less than 2, which may not always be measured or may change as the sample equilibrates (e.g. groundwater). The additional acid volume will likely prevent the formation of precipitates and may simplify field sampling protocols (i.e. measuring the final pH of the preserved sample may not be necessary). A total of eighty-eight replicate samples from sixty-nine different sites were collected from the U.S. Geological Survey's National Water Quality Network (NWQN). One replicate sample was preserved using the current method prescribed by the NFM (0.4% v/v concentrated nitric acid) and additional nitric was added to the second replicate sample (total of 1% v/v concentrated nitric acid). The paired samples were analyzed for trace metals by inductively coupled plasma-mass spectrometry and major cations by inductively coupled plasma-optical emission spectrometry.

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Metadata Created Date June 1, 2023
Metadata Updated Date July 6, 2024

Metadata Source

Harvested from DOI EDI

Additional Metadata

Resource Type Dataset
Metadata Created Date June 1, 2023
Metadata Updated Date July 6, 2024
Publisher U.S. Geological Survey
Identifier USGS:626863f6d34e76103cd011b3
Data Last Modified 20220915
Category geospatial
Public Access Level public
Bureau Code 010:12
Metadata Context
Metadata Catalog ID
Schema Version
Catalog Describedby
Harvest Object Id 7bb98e29-c773-4be7-88a4-b6a0fe8f09ba
Harvest Source Id 52bfcc16-6e15-478f-809a-b1bc76f1aeda
Harvest Source Title DOI EDI
Metadata Type geospatial
Old Spatial -162.9,20.97,-73.4,62.35
Publisher Hierarchy White House > U.S. Department of the Interior > U.S. Geological Survey
Source Datajson Identifier True
Source Hash 12c8ebeee6bf61d17ddc79fd4f5898c118afb6ca0693a9efdd3510f41e48f847
Source Schema Version 1.1
Spatial {"type": "Polygon", "coordinates": -162.9, 20.97, -162.9, 62.35, -73.4, 62.35, -73.4, 20.97, -162.9, 20.97}

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