Effect of moisture and carbon dioxide on concentrations of helium in soils and soil gases

Abstract

Helium is often measured in exploration programs, either in interstitial soil gases collected by hollow probe or in gases desorbed from pore spaces of soil samples. However, measured helium concentrations are affected by various parameters that must be considered when interpreting data, including the variation in concentration of other soil gases. The effects of moisture and carbon dioxide in the soil are particularly important. This study compares helium concentrations with soil moisture and carbon dioxide contents of soil and soil gas samples collected in several areas. Where soil moisture was below about 4% by weight, helium concentrations in soil gases collected by hollow probe correlated well with helium concentrations desorbed from soil at the same site. Measured helium concentrations were significantly reduced, however, in areas where soil moisture was greater than 10% and were below the concentration of helium in air in areas where soil moisture exceeded 18%. Carbon dioxide content of the samples also affects helium concentrations. Helium concentrations were significantly reduced in samples where the carbon dioxide content exceeded 1% by volume of the gas sample.

Statistical approach for the geochemical signature of two active normal faults in the western Corinth Gulf Rift (Greece)

“…1d). The soil gas survey was performed during the dry season, in order to provide stable meteorological conditions and minimal soil gas variation due to soil humidity (Hinkle and Ryder, 1994).…”

Assessment of Radiological Risks due to Indoor Radon, Thoron and Progeny, and Soil Gas Radon in Thorium-Bearing Areas of the Centre and South Regions of Cameroon

“…Only 3% of the data among those surveyed had a soil gas concentration higher than the allowed level prescribed by the UNSCEAR [42]. Radon in soil gas concentration can be influenced by many environmental factors, the most important among these factors being air temperature, barometric pressure, rainfall and snowfall on the radon signal acquired to possibly filter them out [40,[43][44][45]. In the other hand, radon release from soils and rocks is complex because in rock, uranium fixed in minerals along grain boundaries and in defects is susceptible to leaching, thus releasing radon trapped therein.…”

Multi-parametric geochemical survey on evaluation of hydrocarbon potential of trap structure in a desert area: A case of TD-2 structure in the Tarim Basin, China

“…Therefore, these uncertainties are sometimes so strong that they often weaken, even mask the nearsurface geochemical anomalies formed directly or indirectly by the hydrocarbons migrating from subsurface oil and gas reservoirs (Wu Xueming and Zhao Wenxian, 1995;Liu Xiaoyan et al, 2006). The previous research suggested that increases in soil moisture might lead to decreases in the concentrations of light hydrocarbons (Hinkle and Ryder, 1987). In addition, upward migration of gaseous hydrocarbons from subsurface oil and gas reservoirs is not strictly vertical (Xie Xuejing, 1992), but follows complicated pathways of faults, fractures, bedding planes, unconformities, or undiscovered microfissures (Jones and Drozd, 1983).…”