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A mini drivepoint sampler for measuring pore water solute concentrations in the hyporheic zone of sand‐bottom streams
Author(s) -
Duff John H.,
Murphy Fred,
Fuller Chrsistopher C.,
Triska Frank J.,
Harvey Judson W.,
Jackman Alan P.
Publication year - 1998
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1998.43.6.1378
Subject(s) - hyporheic zone , streams , sampling (signal processing) , hydrology (agriculture) , chloride , pore water pressure , geology , groundwater , environmental science , mineralogy , chemistry , geotechnical engineering , computer network , organic chemistry , filter (signal processing) , computer science , computer vision
A new method for collecting pore‐water samples in gravel streambeds is presented. We developed a mini drivepoint solution sampling (MINIPOINT) technique to collect pore‐water samples at 2.5‐cm vertical resolution. The sampler consisted of six small‐diameter stainless steel drivepoints arranged in a 10‐cm‐diameter circular array. In a simple procedure, the sampler was installed in the streambed to preset drivepoint depths of 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 cm. Sampler performance was evaluated in the Shingobee River, Minnesota, and Pinal Creek, Arizona, by measuring the vertical gradient of chloride concentration in pore water beneath the streambed that was established by the uninterrupted injection to the stream for 3 d. Pore‐water samples were withdrawn from all drivepoints simultaneously. In the first evaluation, the vertical chloride gradient was unchanged at withdrawal rates between 0.3 and 4.0 ml min − but was disturbed at higher rates. In the second evaluation, up to 70 ml of pore water was withdrawn from each drivepoint at a withdrawal rate of 2.5 ml min −1 without disturbing the vertical chloride gradient. Background concentrations of other solutes were also determined with MINIPOINT sampling. Steep vertical gradients were present for biologically reactive solutes such as DO, NH 4 + , NO 3 − , and dissolved organic C in the top 20 cm of the streambed. These detailed solute profiles in the hyporheic zone could not have been determined without a method for close interval vertical sampling that does not disturb natural logic mixing between stream water and groundwater.