Concentration in soil gas

Radon concentration in soil gas at depths well below the surface can be estimated from ... 

Kerfoot [6] examined the performance of a grab sampling technique for soil-gas measurement analyses, at a site with groundwater known to be contaminated with chloroform. The study assessed the correlation between soil-gas and groundwater analyses with chloroform as a model volatile organic compound. Chloroform concentration in soil gas increased linearly with depth in the unsaturated zone. 

Reimer, G.M., Roberts, A.A. and Denton, E.H., 1976. Diurnal effects on the helium concentration in soil-gas and near surface atmosphere. US Geol. Survey, Open File Report, 76-715, 6 pp. 

Analytical methods are available which allow for the quantification of radon in air, water, and soil. However, methods for the measurement of radon concentrations in soil-gas are limited. The ability to accurately measure soil-gas is needed to provide a better understanding of the emanation rate of radon gas from soil. 

Radon and helium soil-gas surveys may be useful in detailed or semi-regional exploration programmes by virtue of the fact that both are inert gases derived from the radioactive decay of uranium and its daughters. As such, the gases may migrate away from a buried uranium deposit to yield anomalous concentrations of radon and/or helium in soil gas. Thus, a buried uranium deposit may be remotely detectable indirectly by detection of anomalous radon and/or helium concentrations in soil gas. 

When a single organic compound is present in the soil matrix as NAPL, its concentration in soil air (Ca) can be directly calculated from the vapor pressure of this compound (P°) and the Ideal Gas Law ... 

Concentrations of hydrogen sulfide in soil gas from samples taken at some NPL sites ranged from 75 to 47,000 ppm (HazDat 1997). Data on soil gas concentrations at all NPL sites were not available. 

Measures to reduce radon concentrations have been studied in an old house in which the radon decay-product concentration initially exceeded 0.3 Working Level (WL). Some of the measures were only partially successful. Installation of a concrete floor, designed to prevent ingress of radon in soil gas, reduced the radon decay-product concentration below 0.1 WL, but radon continued to enter the house through pores in an internal wall of primitive construction that descended to the foundations. Radon flow was driven by the small pressure difference between indoor air and soil gas. An under-floor suction system effected a satisfactory remedy and maintained the concentration of radon decay products below 0.03 WL. 

The subsoil is the principal source of radon in this house. Both the activity concentration of radium-226 in subsoil and of radon in soil gas are above levels for building ground that might result in significant indoor radon concentrations. The radon decay-product concentration in the dwelling before remedial measures were taken was substantially higher than the reference value of 120 mWL. 

Radon in soil gas is present everywhere throughout the province in all geologic terrains. Soil gas Rn concentrations range from a low of 0.1 kBq/m3 to a high of 207.0 kBq/m3 with a mean of 25.3 kBq/m3 (Fig. 3). The highest Rn soil gas concentrations are also associated with Middle-to-Late Devonian leucomonzogranite of the South... 

The volatility potential (slope of the vapor pressme vs. concentration in soil organics) of GA is 2.4 x 10" mm Hg/mg/kg and its air-soil partition coefficient (for a soil density of 1.4 g/cm ) of 1 x 10 mg/m (MacNaughton and Brewer, 1994), indicate that GA will evaporate from soil into the air. Results of a field trial with GA showed 10% evaporation in 0.27 horns and 90% evaporation in 4.66 hours (Morrill et al., 1985). 

In geochemical exploration, soil samples, either surficial or (in arid regions) microlayer are the recommended sample medium for the collection of sulphur compounds in soil gases. Soils should be placed in plastic bags or glass containers that are as air-tight as possible. An entire study area should be sampled at one time, over a period of as few days as possible, to avoid weather-related or seasonal fluctuations in soil-gas concentrations. The soil samples should be stored in a cool place or in a freezer. All of the soil samples from a particular area should be analysed as quickly as possible after collection. They should be sieved to the same mesh size and should be of the same weight for analysis. 

Variations in soil-gas radon concentration with depth and barometric pressure (Irom Bogslovkaya etal., 1932)... 

Comparing the spreading behavior of CAH and MTBE is to be considered that by the spill of the CAH into the subsoil usually a pure phase product of PCE, TCE or 1.1.1-TCA is infiltrated. Most CAH contaminations were released by degreasing plants in the metal manufacturing industry. Due to their noticeable vapor pressure, CAH develop a gas phase body in the unsaturated zone, which is characterized by high CAH concentrations in soil air. 

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