Practical Considerations for
Measuring Hydrogen Concentrations
in Groundwater
F R A N C I S H . C H A P E L L E , * , †
D O N A . V R O B L E S K Y , †
J O A N C . W O O D W A R D , ‡ A N D
D E R E K R . L O V L E Y §
U.S. Geological Survey, 720 Gracern Road, Suite 129,
Columbia, South Carolina 29210, U.S. Geological Survey,
430 National Center, Reston, Virginia 22092, and
Department of Microbiology, University of Massachusetts,
Amherst, Massachusetts 01003
Several practical considerations for measuring concentra-
tions of dissolved molecular hydrogen (H2) in groundwater,
including (1) sampling methods, (2) pumping methods, and
(3) effects of well casing materials were evaluated. Three
different sampling methodologies (a downhole sampler,
a gas-stripping method, and a diffusion sampler) were
compared. The downhole sampler and gas-stripping
methods gave similar results when applied to the same wells.
The diffusion sampler, on the other hand, appeared to
overestimate H2 concentrations relative to the downhole
sampler. Of these methods, the gas-stripping method is better
suited to field conditions because it is faster (∼30 min
for a single analysis as opposed to 2 h for the downhole
sampler or 8 h for the diffusion sampler), the analysis is
easier (less sample manipulation is required), and the data
computations are more straightforward (H2 concentrations
need not be corrected for water sample volume).
Measurement of H2 using the gas-stripping method can be
affected by different pumping equipment. Peristaltic,
piston, and bladder pumps all gave similar results when
applied to water produced from the same well.
It was
observed, however, that peristaltic-pumped water (which
draws water under a negative pressure) enhanced the gas-
stripping process and equilibrated slightly faster than
either piston or bladder pumps (which push water under a
positive pressure). A direct current (dc) electrically driven
submersible pump was observed to produce H2 and was not
suitable for measuring H2 in groundwater. Measurements
from tw