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Improved Piezometer Construction and Sampling Techniques to Determine Pore Water Chemistry in Aquitards
Author(s) -
Wassenaar Leonard I.,
Hendry M. Jim
Publication year - 1999
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1999.tb01143.x
Subject(s) - piezometer , aquifer , pore water pressure , geology , sampling (signal processing) , groundwater , geotechnical engineering , engineering , electrical engineering , filter (signal processing)
Due to extremely slow water recovery rates in aquitards and high contamination potential from sealing materials, installation of piezometers in aquitards for geochemical studies requires specialized construction and careful sampling techniques. Few methods have been demonstrated for obtaining representative ground water samples for geochemical parameters from piezometers in aquitards. Here we implement and evaluate an aquitard piezometer installation and ground water chemistry sampling strategy and show that the use of an inert gas pocket in piezometer construction can be used to delay seal contamination for at least three years and avoid oxygenation and disturbance of downhole redox conditions. Major ion analyses did not change appreciably through the standing water columns in the aquitard piezometers over time; however, reliable measurements of typically unstable geochemical parameters (dissolved oxygen, pH, and oxidation‐reduction potential) were best obtained using downhole, in situ instrumentation, provided there was at least 2 to 10 m of standing water in the piezometer.