title: The quantification of hydrogen and methane in contaminated groundwater: validation of robust procedures for sampling and quantification.
abstract: A number of currently recommended sampling techniques for the determination of hydrogen in contaminated groundwater were compared regarding the practical proficiency in field campaigns. Key characteristics of appropriate sampling procedures are reproducibility of results, robustness against varying field conditions such as hydrostatic pressure, aquifer flow, and biological activity. Laboratory set-ups were used to investigate the most promising techniques. Bubble stripping with gas sampling bulbs yielded reproducible recovery of hydrogen and methane which could be verified for groundwater sampled in two field campaigns. The methane content of the groundwater was confirmed by analysis of directly pumped samples thus supporting the trueness of the stripping results. Laboratory set-ups and field campaigns revealed that bubble stripping of hydrogen may be restricted to the type of used pump. Concentrations of dissolved hydrogen after bubble stripping with an electrically driven submersible pump were about one order of magnitude higher than those obtained from diffusion sampling. The gas chromatographic determination for hydrogen and methane requires manual injection of gas samples and detection by a pulsed discharge detector (PDD) and allows limits of quantification of 3 nM dissolved hydrogen and 1 µg L⁻¹ dissolved methane in groundwater. The combined standard uncertainty of the bubble stripping and GC/PDD quantification of hydrogen in field samples was 7% at 7.8 nM and 18% for 78 nM.
authors: BAM Federal Institute for Materials Research and Testing, Berlin, Germany. ute.dorgerloh@bam.de
authors: Ute
authors: U
authors: Dorgerloh
authors: Roland
authors: R
authors: Becker
authors: Hubert
authors: H
authors: Theissen
authors: Irene
authors: I
authors: Nehls
mesh_terms: D002849:Chromatography, Gas; D004784:Environmental Monitoring / Q000379:methods*; D006859:Hydrogen / Q000032:analysis*; D008697:Methane / Q000032:analysis*; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply
chemical_list: D014874:Water Pollutants, Chemical; D014867:Water; D006859:Hydrogen; D008697:Methane