Practical Considerations for Measuring Hydrogen Concentrations in Groundwater

Abstract

Several practical considerations for measuring concentrations of dissolved molecular hydrogen (H 2 ) 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 H 2 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 (H 2 concentrations need not be corrected for water sample volume). Measurement of H 2 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 gasstripping 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 H 2 and was not suitable for measuring H 2 in groundwater. Measurements from two field sites indicate that iron or steel well casings produce H 2 , which masks H 2 concentrations in groundwater. PVC-cased wells or wells cased with other materials that do not produce H 2 are necessary for measuring H 2 concentrations in groundwater. ES970085C X Abstract published in Advance ACS Abstracts, August 15, 1997.

Hydrogen and bioenergetics in the Yellowstone geothermal ecosystem

“…We measured aqueous H 2 concentrations in Yellowstone waters [hot springs, streams, geothermal vents, and a well (27)] with a modified bubble-stripping method (28). Source waters were pumped with a 12-V portable peristaltic pump through insulated, H 2 -impermeable polyethylene tubing for 20 min at a flow rate of 200 ml͞min, through a 250-ml glass bottle bubble stripping device (28). Twenty milliliters of atmospheric air was introduced into the water-filled bottle.…”

Effect of 3-nitrooxypropanol on methane and hydrogen emissions, methane isotopic signature, and ruminal fermentation in dairy cows

“…The TILDAS measures isotopologue specific absorption in the 163 mid infrared (ca. 8.5μm wavelength) region (corresponding C-H and C-D bending 164 vibrations) using multipass (76 m pathlength) direct absorption cell and continuous 165 wavelength quantum cascade lasers (Ono et al, 2014 At the time of gas collection, a sample of rumen fluid was collected from the 180 ventral rumen, filtered through 4 layers of cheesecloth, transferred into 20-mL 181 scintillation vials (Fisher Scientific, Pittsburgh, PA), and stored at 4°C until analyzed for 182 dissolved H 2 (Vaportech Services, Valencia, PA) according to Chapelle et al (1997). 183…”

Removal of chlorinated solvents from carbonate-buffered water by zero-valent iron

“…Hydrogen concentrations found in the box are three orders of magnitude higher than normal concentrations found in subsurface environments where natural attenuation processes occur [8]. This observation may explain why dehalogenation of chlorinated ethenes in PRBs is completed with ethane as the final product compared to natural attenuation sites where ethene is often found in high concentrations [13][14][15].…”

“…Analyses of chlorinated ethenes and light hydrocarbon gases (methane, ethane, ethene) were performed by a static headspace method using a ThermoFinnigan-Trace (Thermo, USA) gas chromatograph (GC) (with a flame ionization detector (FID). Dissolved H 2 analyses were performed by GC using a static headspace method and concentrations were determined by the method described by Chapelle et al [8]. Prior to sample collection, field parameters, such as temperature, pH, oxidation-reduction potential (Eh), and electrical conductivity (EC), were determined for each sample using calibrated electrodes (WTW, Germany).…”