Hydrogen in soil gas in Southern Moravia (Czech Republic): Origin and implications for exploration

Efforts for natural hydrogen exploration have vastly increased over the last years and although soil gas measurements represent one of the standard methods for natural hydrogen exploration, results are often ambiguous and difficult to interpret. This study presents a case where high hydrogen (>1000 ppmv), methane (≤47.6 vol%) and carbon dioxide (≤29.4 vol%) were detected in soil gas during a natural hydrogen exploration campaign in Southern Moravia (Czech Republic). Using an integrated approach including statistics, gas geochemistry, microbiological analyses, and soil characterization these gases can be attributed primarily to a soil-related microbial rather than a geological source. The soil gas composition was found to be strongly impacted by soil properties, in particular soil pH, and showed significant seasonal variations. These results underline the importance of supporting soil (microbial) analyses for correct interpretation of hydrogen shows in soil gas and the assessment of an area's geologic hydrogen potential.