Abstract:Using a portable hydrogen analyser, field measurements are performed to determine hydrogen (H2) concentrations in the soils of the north China plain, Loess plateau, Changping district, Haiyuan fault zone, and Beiluntai fault at the edge of south Tianshan. The factors affecting soil gas H2 concentration, such as the sampler type, test hole depth, soil characteristics, and fault characteristics, and the mechanisms of their influence are discussed in terms of a gas diffusion equation. The results show that: (1) the soil gas H2 concentration is mainly affected by the time lapse between the hole drilling and measurement, test hole depth, and sampler shape; (2) the measured soil gas H2 concentration agrees well with the analytical solution of the gas diffusion equation, and the curve shape is closely related to the degree of H2 enrichment in the soil and the soil density; and (3) the soil gas concentration in the fracture zone is largely affected by tectonism, the fault slip rate, the degree of fault locking, the development degree of fractures between the hanging wall and footwall, and the degree of fracture locking, because these factors can alter the H2 upward transport channels and degree of surface enrichment.