I read about the poor reproducibility of soil gas data in repeat surveys. So, why should anyone use instant soil gas surveys?
The question is related to several factors: • Seepage is a dynamic process with some variability of the seep rate due to changing and alternating subsurface conditions. Thus, some variation is expected and, in fact, observed. • In some cases the gas sampling is carried out at very shallow depth; no wonder the variability of highly fugitive gases is large. • Much of the soil HC content has nothing to do with seepage but with biological soil in-situ HC generation and destruction. Most of the variability of soil gases originates from these processes. Once the true seep HC are identified, the seep signal is present and stable as presented in many repeat GEL surveys.
