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Environmental influences upon mercury, radon and helium concentrations in soil gases at a site near Denver, Colorado
Abstract
Variations in soil gas Hg, Rn and He concentrations and meterological variables were monitored daily at one site over a period of 22 months. Air and soil temperature, humidity, barometric pressure, soil moisture, wind direction and velocity, soil freeze-thaw, water table elevation, crustal strain and gas emissions were determined simultaneously in order to assess the influence of the environmental variables on gas emission.Mercury concentrations were found to be higher in the summer while Rn and He concentrations were higher in the winter. It is hypothesized that adsorption-desorption controls the migration of Hg whereas Rn and He concentrations are controlled by diffusion and mass transport. Gas emissions respond to seasonal and shorter-term changes in environmental conditions. Stepwise multiple regression using gas emissions as the dependent variables suggests that environmental parameters account for 62% of the total Hg variance, 83% of the total Rn variance, and 33% of the total He variance. Temperature, barometric pressure and soil moisture exert the most influence on gas emissions with temperature effects dominating gas emissions throughout the year. Soil gas emissions display a predictable behavior during winter and summer when more stable meteorological conditions exist. During the transitional seasons of spring and fall, soil gas emissions become erratic and exhibit increased variability. Environmental variables are interrelated and appear to control the manner of gas migration.Increased adsorption by solids during the season of falling temperature decreases soil gas Hg<0.0001 ng L−1, which is desorbed as the soil warms in the spring. Transport of Rn and He is primarily by convection. During the winter months, air temperatures are less than soil temperatures promoting upward movement of Rn and He by convection. During the summer, soil temperatures are less than air temperatures and an inversion layer below the level of sampling reduces upward flux and observed concentration.
... [36] Various models have been developed to interpret the effects of atmospheric pressure changes on radon transport from soil to atmosphere. The two major components of radon migration are diffusion and advection [Tanner, 1964; Klusman and Jaacks, 1987; Nazaroff, 1992]. Some researchers used pure diffusion models to simulate the radon transport process [e.g., Kraner et al., 1964; Tanner, 1964; Nazaroff, 1992]. ...
... On the basis of measurements of radon concentration in a column under well-defined conditions, Schubert and Schulz [2002] concluded that there is no impact of atmospheric pressure variations on radon migration and the atmospheric pressure leads to long-term changes in radon concentration rather than diurnal alterations. In addition, both positive [Galmarini, 2006] and negative [Klusman and Jaacks, 1987; Schery et al., 1989; Hutter, 1996; Iakovleva and Ryzhakova, 2003; Smetanov a et al., 2010] correlations between radon concentration and atmospheric pressure were found. Some researchers stated that only sudden drops or increases of atmospheric pressure (of the order of 1.0–1.5 kPa) can affect the radon exhalation [Kataoka et al., 2003; Galmarini, 2006]. ...
... Methane Transport [44] A changing atmospheric pressure exerts a pumping effect on the soil gas, drawing gas out from the ground during periods of decreasing pressure and forcing atmospheric air into the ground during periods of increasing pressure [Pinault and Baubron, 1997; Gebert and Groengroeft, 2006]. Barometric pumping has been found to have a significant influence on trace gases movement through any highly permeable medium [Klusman and Jaacks, 1987; Massman et al., 1995]. Christophersen et al. [2001] observed that during a drop in atmospheric pressure the landfill gas (CH 4 and CO 2 ) fluxes changed dramatically within a very short time. ...
Subsurface airflow in unsaturated zones induced by natural forcings is of importance in many environmental and engineering fields, such as environmental remediation, water infiltration and groundwater recharge, coastal soil aeration, mine and tunnel ventilation, and gas exchange between soil and atmosphere. This review synthesizes the published literature on subsurface airflow driven by natural forcings such as atmospheric pressure fluctuations, topographic effect, water table fluctuations, and water infiltration. The present state of knowledge concerning the mechanisms, analytical and numerical models, and environmental and engineering applications related to the naturally occurring airflow is discussed. Airflow induced by atmospheric pressure fluctuations is studied the most because of the applications to environmental remediation and transport of trace gases from soil to atmosphere, which are very important in understanding biogeochemical cycling and global change. Airflow induced by infiltration is also an extensively investigated topic because of its implications in rainfall infiltration and groundwater recharge. Airflow induced by water table fluctuations is important in coastal areas because it plays an important role in coastal environmental remediation and ecological systems. Airflow induced by topographic effect is studied the least. However, it has important applications in unsaturated zone gas transport and natural ventilation of mines and tunnels. Finally, the similarities and differences in the characteristics of the air pressure and airflow are compared and future research efforts are recommended.
... Bq/l (Singh et al. 1986) and a conversion factor of 1 pCi/l=37 Bq/l (DOE 1988). Klausman and Jaacks (1987) showed that dry soil condition usually results in decrease in radon exhalation and emanation rate. ...
... During the raining season, air temperatures are less than soil temperatures thus promoting upward movement of radon soil–gas by convection (Fig. 7). On the other hand, during the dry season, soil temperatures are less than air temperatures, and the presence of inversion layer below the sampling point contribute to significant reduction of upward radon flux (Klausman and Jaacks 1987). Figure 7 is a schematic diagram of sub-terrestrial radon circulations during dry and wet seasons. ...
In an effort to quantify the geogenic radon soil–gas potential and appraise the use of radon technique as a geological mapping
tool in a crystalline basement rock terrain of Ile–Ife Nigeria, radon measurement concentration were made using a radon detector
instrument (EDA RD-200) that measures radon isotopes by a scintillator cell coupled to a photomultiplier tube. The data were
collected from soils derived from three different lithologic rock units. The observed values were then correlated with the
geology of the area. Significant differences in the radon soil–gas concentrations among the three geologic units were observed.
Granite gneiss has the highest concentration, followed by grey gneiss and mica schist in that order. The geometric mean (GM)
concentration of radon-222 measured in soils directly overlying the three different rock types were 301.4pCi/l for granite
gneiss, 202.8pCi/l for the grey gneiss, and 199.4pCi/l for mica schist. Conversely, the average values for radon-220 averaged
1510.0, 815.4, and 733.0pCi/l for granite gneiss, grey gneiss, and mica schist rocks, respectively. Statistical t test (α=0.05) results indicated that there was no significant difference in the geometric mean of radon soil–gas measured
between low and medium potential zones. However, significant differences were found between the low and high radon potential
zones, and between the medium and high zones. The low concentrations of radon soil–gas emission observed in this study is
explained in terms of the seasonal variation due to thermal convection fluid movement, while the radon concentrations were
found to be controlled by the lithology and geochemistry of the underlying bedrock.
... The average radon concentrations and the associated standard deviations were calculated seasonally (spring, summer, autumn and winter). Soil temperature affects mostly the soil gas radon levels (Klusman and Jaacks, 1987; Zmazek et al., 2005). Therefore, each season is defined using seasonal variation of soil temperature (Table 3). ...
Previous studies showed that tectonic movement and meteorological events are accompanied with radon release. In this study soil gas radon and tectonic movements were investigated with meteorological factors taking into account. Soil gas radon measurements were collected over a-two year period (2008-2010) at the Tuzla Fault in Turkey. The relationship between radon anomalies and seismic activities was evaluated using Dobrovolsky's form. It is shown that not only magnitude of earthquake but also distance from the measurement site should be used for identifying radon anomalies.
... The soil gas method experienced further applications and developments in the last decade through studies of CO 2 storage sites or natural analogues (e.g. in Europe : Annunziatelis et al., 2008; Battani et al., 2010; Beaubien et al., 2008; Gal et al., 2010; Krüger et al., 2009; Pauwels et al., 2007). Joint quantification of several gases can indeed help increase accuracy in detecting abnormalities associated with leakage of structural discontinuities in the crust (faults, magmatic fumaroles …) and energy flows (Baubron and Sabroux, 1984; Baubron et al., 2002; Ciotoli et al., 1999; Guerra and hal-00575575, version 1 -10 Mar 2011 Lombardi, 2001; Klusman et Jaccks, 1987; Walia et al., 2010). Indeed, soil gas monitoring combines the quantification of ubiquitous species in soil atmosphere (CO 2 and O 2 ) with that of radon-222 activities and helium-4 concentrations, both gases originated from the decay chain of uranium-238. ...
Soil gas monitoring techniques (CO2, O2, 222Rn, 4He) are used in the geographical context of the recent volcanic system of Lake Pavin (Puy-de-Dôme), to get a better knowledge of local gaseous emissions, in order to establish whether or not this system can present evidence of reactivation. Concentrations up to 100% CO2 and 50 ppm of helium are measured in a narrow geographical area (Escarot mofette), together with a magmatic origin for these gases. Radon activity in the mofette area is quite high, but does not show, compared to surrounding areas, enrichments as high as those measured for CO2 or helium. Hourly records of these radon activities, performed during several weeks, suggest the existence of pulsed radon exhalation in the mofette area. The period of this pulsation is around 40 days but its origin remains poorly understood. Apart from this mofette, no evidence of gas originating from depth is highlighted.RésuméLes techniques de monitoring des teneurs en gaz dans les sols (CO2, O2, 222Rn, 4He) sont utilisées dans le cadre géographique du système volcanique récent du lac Pavin (Puy-de-Dôme), afin de réaliser un état des lieux des émanations gazeuses locales, et de déterminer si ce système peut présenter des indices de réactivation. Des teneurs jusqu’à 100 % de CO2 et 50 ppm d’hélium sont mesurées dans un étroit périmètre (mofette d’Escarot), soulignant une origine magmatique pour ces gaz. Les activités radon y sont assez importantes, sans toutefois présenter, par rapport aux zones environnantes, des enrichissements aussi importants que ceux mesurés pour le CO2 ou l’hélium. Des enregistrements horaires sur plusieurs semaines de ces activités radon semblent indiquer l’existence, dans la zone de la mofette, de pulsations de longue période (40 jours), dont l’origine est mal cernée. En dehors de cette mofette, aucun indice de présence de gaz d’origine profonde n’est mis en évidence.
... Regarding long-term variations, soil gas concentrations have shown temporal patterns with: (i) high summer and low winter 222 Rn (Rose et al., 1990); (ii) high winter/spring and low summer/ autumn (Klusman and Jaacks, 1987; Schumann et al., 1989); (iii) winter minima and autumn maxima (Hutter, 1996); and (iv) no annual pattern (Fleischer et al., 1979; Hutter, 1996). The same discrepancies have been found for radon exhalation rates (Dö rr and Mü nnich, 1990). ...
Residues from industrial activities involving naturally occurring radioactive materials (NORMs) may cause radiation exposures to members of the public, particularly when NORM-affected land is brought into residential use. To provide an adequate protection against radiation in such situations, the following limiting criteria are currently required in Spain for releasing NORM-affected land: (i) no more than a 300 microSv yr(-1) increase (excluding radon doses) over the natural background; (ii) (222)Rn concentrations in hypothetical future dwellings lower than 200 Bq m(-3); and (iii) reduction of all radiation exposures to as low as reasonable achievable. This paper addresses some of the problems encountered in translating the (222)Rn criterion into site-specific release limits and in demonstrating compliance with them.
Radon (Rn) and helium (He) gases from uranium decay form distinct anomalies related to buried uranium deposits. In order to trace the geochemical anomalous sources from the volcanic-related uranium deposits in deeply buried areas, systematical Rn contents and He isotope ratios were analyzed from the Daguanchang uranium deposit. The soil gas Rn concentrations above the deep uranium are ten times higher than those in barren areas, indicating that instantaneous Rn content measurements can be used to detect deeply buried uranium. The helium isotope ratios (3He/4He) of the unmineralized samples from the mineralized drill hole (ZK1) are relatively lower and uniform compared to those of the samples from no-mineral drill hole (ZK2). However, the Th and U contents of the drill core samples from ZK1 are slightly lower than those of the samples from ZK2, indicating that the lower 3He/4He ratios in ZK1 are most likely due to the addition of 4He from underlying uranium intervals. The differences in the instantaneous Rn contents are consistent with the variations in the He isotope ratios of the drill core samples. These results demonstrate that soil gas Rn and 3He/4He ratios are useful tracers and can indicate the existence of deeply buried volcanic-related hydrothermal uranium ores.
Radon (Rn-222 or Rn) is a naturally occurring chemical element that belongs to the progeny of U-238 released from soil and rocks into the atmosphere, whose impact on organisms is not negligible when it occurs inside confined spaces, such as mine shafts or low-ventilated buildings. The current methodologies for indoor radon assessment are based on passive and active detection. If passive detectors are mainly designed for long-term assessment, active detectors are electronic equipment that can allow on-time visualization of results and, therefore, faster decision-making on risk mitigation measures implementation. However, despite offering a prompt and informed decision, the uncertainty associated with active detector results may cast doubt on the quality of the measurements, which especially arises from the duration of the monitoring campaign. Since radon emanation from soils and rocks depends on a set of variables related to meteorological parameters and soil structure, the seasonal variation of these parameters impacts indoor radon concentration assessment, both on short-term and long-term measurements. Therefore, short-term monitoring campaigns lasting a month, a week, or a day may not produce a statistically representative description of indoor radon exposure for the monitored building. Accordingly, the study compares the reliability of short-term and long-term indoor radon measurements. It proposes a procedure for assessing the indoor Radon Exposure Potential (RnEP) based on in situ measurements through the analysis of the frequency of occurrence of results divided into three classes of potential exposure (low, moderate and high) to reduce occupants' radon risk exposure.
The soil radon (Rn²²²) and thoron (Rn²²⁰) concentrations recorded at Badargadh and Desalpar observatories in the Kutch region of Gujarat, India, have been analyzed to study the sources of the radon emissions, earthquake precursors, and the influence of meteorological parameters on radon emission. Radon and meteorological parameters were recorded using Radon Monitor RMT 1688-2 at these two stations. We used the radon data during February 21, 2011 to June 8, 2011, for Badargadh and March 2, 2011 to May 19, 2011, for the Desalpar station with a sampling interval of 10 min. It is observed that the radon concentrations at Desalpar varies between 781 and 4320 Bq m⁻³with an average value of 2499 Bq m⁻³, whereas thoron varies between 191 and 2017 Bq m⁻³with an average value of 1433.69 Bq m⁻³. The radon concentration at Badargadh varies between 264 and 2221 Bq m⁻³with an average value of 1135.4 Bq m⁻³, whereas thoron varies between 97 and 556 Bq m⁻³. To understand how the meteorological parameters influence radon emanation, the radon and other meteorological parameters were correlated with linear regression analysis. Here, it was observed that radon and temperature are negatively correlated whereas radon and other two parameters, i.e., humidity and pressure are positively correlated. The cross correlogram also ascertains similar relationships between radon and other parameters. Further, the ratio between radon and thoron has been analyzed to determine the deep or shallow source of the radon emanation in the study area. These results revealed that the ratio radon/thoron enhanced during this period which indicates the deeper source contribution is prominent. Incidentally, all the local earthquakes occurred with a focal depth of 18–25 km at the lower crust in this region. We observed the rise in the concentrations of radon and the ratio radon/thoron at Badargadh station before the occurrence of the local earthquakes on 29th March 2011 (M 3.7) and 17th May 2011 (M 4.2). We clearly observed the radon level crossing the mean + 2*sigma level before the occurrence of these events. We conclude that these enhanced radon emissions are linked with alteration of the crustal stress/strain in this region as this observing station is near the epicenters of the earthquakes. We did not observe considerable variations in radon at the Desalpar station which is far from the earthquake location.
This research investigates the main factors influencing changes in hydrogen concentration in a fault zone and analyzes the relationship between hydrogen and tectonic activity. Based on the hydrogen concentration in the fault gas and continuous observation data from Mashankou, Neixiang County, Henan Province, the relationships between the variation in hydrogen concentration and ground temperature, atmospheric temperature, and atmospheric pressure are analyzed. In addition, the earth tide effect on hydrogen in the fault zone is discussed. The results show that the direct influence of atmospheric or ground temperatures on the hydrogen concentration is not significant. The atmospheric and ground temperatures have some impact on the hydrogen concentration only when ground temperature increases. By means of a wavelet analysis method, which separates the semidiurnal wave and diurnal wave signals of hydrogen, the results show that the hydrogen concentration is capable of indicating the solid earth tide when comparing the pressure tide and solid earth tide signals in the same period.
In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009-2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.
Metal migration processes, by means of gas-transported particles, from an iron magnetite skarn deposit beneath Quaternary transported overburden, to surface was studied at the Kaxiutata iron deposit. This study area is located in the desert of the Inner Mongolia region in northern China. Ascending gas-transported particles were collected using passive adsorption methods; a total of 50 samples were obtained over the known mineralization (30 within the mining area and 20 from the exploration area), and 15 samples were collected over background areas for comparison. The morphology, categorization, and chemical composition of particles in these samples were determined by transmission electron microscopy (TEM). In the mining and exploration area, the particles related to the subsurface mineralization (ore-bearing particles) are primarily Fe-, Cu-, Zn-, Pb-, and Bi-bearing, and particles show significant common characteristics. Sulphur is generally absent, or its content is notably low. However, based on the geological description of primary mineralization, Cu, Zn, and Pb occur mainly as sulphides, implying that the minerals were subjected to in situ or transport-associated oxidation. Most particles are actually aggregates of various smaller particles of diverse origin. Evidence of oxidation and agglomeration of particles may reflect the high porosity and gas permeability of the sandy overburden, which provides an oxidizing environment for gas-transported particles. The distribution of ore-bearing particles is correlated with the subsurface mineralization. Iron-rich particles (> 30% Fe) and Cu-, Zn-, and Bi-bearing particles collected above the mining area were also collected in the exploration zone, and these types of particles are likely indicators of underlying iron mineralization. Samples collected from the background zone revealed no Cu-, Bi-, Mo-, and Pb-bearing particles. The migration mechanism of gas-transported particles in the desert area is summarized and discussed based on this and previous studies.
Supplementary material
Some of the TEM images, high resolution TEM images and SAED patterns of the particles with no relation to mineralization are supplemented in Appendix 1 which is available at http://www.geolsoc.org.uk/SUP18810 .
Health risk assessments for mercury are subject to uncertainties associated with the prediction of exposure from multiple pathways (air, water, and food). In order to accurately predict multipathway exposure, an understanding of the transport and transformation processes that govern mercury's multimedia distribution is required. Modeling and analysis of multimedia exposure requires knowledge of the physicochemical properties, partition coefficients, and intermedia transport properties of a compound. Although a number of reviews of the behavior of mercury in the environment have been published over the last decade, little attention has been given to the environmental multimedia distribution of mercury and the governing intermedia transfer factors. This review provides a comprehensive evaluation of the chemical and physical processes that govern mercury distribution among the major environmental media. Physicochemical properties, partition coefficients, and intermedia transport parameters that can be used to predict abiotic and biotic transfer of mercury among environmental media are also presented.
A multidisciplinary approach integrating self-potential, soil temperature, heat flux, CO2 efflux and gravity gradiometry signals was used to investigate a relatively small fissures-related hydrothermal system near the summit of Mt. Etna volcano (Italy). Measurements were performed through two different surveys carried out at the beginning and at the end of July 2009, right after the end of the long-lived 2008–2009 flank eruption and in coincidence with an increase in diffuse flank degassing related to a reactivation of the volcano, leading to the opening of a new summit vent (NSEC). The main goal was to use a multidisciplinary approach to the detection of hidden fractures in an area of evident near-surface hydrothermal activity. Despite the different methodologies used and the different geometry of the sampling grid between the surveys, all parameters concurred in confirming that the study area is crossed by faults related with the main fracture systems of the south flank of the volcano, where a continuous hydrothermal circulation is established. Results also highlighted that hydrothermal activity in this area changed both in space and in time. These changes were a clear response to variations in the magmatic system, notably to migration of magma at various depth within the main feeder system of the volcano. The results suggest that this specific area, initially chosen as the optimal test-site for the proposed approach, can be useful in order to get information on the potential reactivation of the summit craters of Mt. Etna.
Natural emissions of Hg are attracting increased interest both for their environmental implications and for possible applications in the exploration of mineral, petroleum and geothermal fields. However, daily and seasonal fluctuations in concentrations of Hg in the atmosphere, caused by meteorological and environmental variables, has made it very difficult to assess Hg anomalies by conventional analytical procedures. Some species of widespread foliose lichens from an abandoned cinnabar mining and smelting area (Mt. Amiata), geothermal fields (Larderello, Bagnore and Piancastagnaio, Central Italy), and active volcanic areas (Mt. Etna and Vulcano, Southern Italy) seem to be very suitable biomonitors of gaseous Hg; especially as lichen thalli have an Hg content which reflects average values measured in air samples. We discuss the advantages of quantitative biological monitoring by lichens with respect to conventional air sampling in large-scale monitoring.
The flux of elemental mercury vapor from intact mill tailings (36 to 1270 mug Hg/g), soil (7 mug Hg/g), and cinnabar ore (934 mug Hg/g) was measured as a function of temperature (20°-60°C) and wind velocity (0.2-0.8 m/s) using a controlled environment, open gas-exchange system. Continuous air movement over core surfaces in the gas-exchange chamber resulted in a logarithmic decline in mercury flux with time. Measurement of the effect of environmental parameters on mercury flux was done after attainment of a quasi steady state of flux. Prior to attainment of this state the activation energy for mercury flux was less than the molar heat of vaporization of element mercury (14 kcal/mol). At steady state the substrate-to-air flux of mercury vapor increased logarithmically with temperature, mimicking the element's vapor pressure curve; and activation energies (16.4 to 25.7 kcal/mol) for mercury flux were higher than the molar heat of vaporization of elemental mercury due to physicochemical properties of the soil (e.g., porosity, organic matter, clay content) that affect gas-phase mercury transport and fate. A change in wind velocity from 0.2 to 0.8 m/s resulted in an increase in mercury flux by a factor of 2 for a core with >150mugHg/g and no significant response from two cores with
A summary of geochemical techniques for purposes of determination of a baseline condition and subsequent monitoring of potential gas microseepage from CO2-EOR or geologic sequestration is presented. The methods include; above ground open-atmosphere techniques, measurements at the land surface–atmosphere interface, and shallow subsurface sampling and measurements. The advantages and disadvantages are presented based on previously published measurements utilizing these techniques.The monitoring for seepage from a CO2-EOR or geologic sequestration project might logically focus on measurements of CO2. Carbon dioxide measurements, particularly in the atmosphere will suffer some quantifiable disadvantages; relatively high atmospheric concentration for a tracer, high environmental variance, multiple natural sources, and solubility/reactivity with water. These factors combine to suggest that CO2 may not effectively serve as an early warning tracer or surface indicator of seepage.Other methods and tracers that are discussed focus on gas exchange measured at the surface and shallow soil gas measurements utilizing a variety of tracers. These parameters include; CO2, CH4 and light hydrocarbons, stable carbon isotopic measurements of carbon-containing gases, carbon-14 content of CO2, inert gases, and artificial tracers entrained in the injected CO2. Use of secondary carbonates in the soil or upper portion of the sedimentary column and their readily measured stable isotopic ratios, and composition of shallow groundwater are included. These materials can be useful in the baseline characterization and provide evidence for fossil gas leakage from depth.
A model for a reduced chimney above ore deposits is presented that complements the existing electrical charge model. This new model emphasizes the role of reduced gases in the formation of the chimney. A computer model for the transport of reduced gases in the unsaturated zone and subsequent microbial oxidation is applied to a hydrocarbon gas chimney. The role of nitrogen soil gases is demonstrated for active epithermal systems. The formation of gaseous As(CH(3))(3) and its transport and oxidation in the unsaturated zone is postulated for the formation of near-surface extractable As, and possibly other elements. The transport of Hg and its flux into the atmosphere is demonstrated to have a significant seasonal variation. This in turn results in variation in seasonal soil gas Hg concentrations. The unsaturated zone model is applied to the vertical transport of ultrafine particulates with application to Au. Barometric pumping causes pressure gradients in the unsaturated zone that are capable of moving sub-micron Au particulate to the surface. A variety of exploration methods are suggested by the data and modelling of transport processes.
In order to determine the extent and causes of radon variability in soil gas, repeated measurements of 222Rn, 220Rn, and soil properties including moisture, temperature, permeability, and diffusivity have been made at five sites in central Pennsylvania. Concentrations of 222Rn and 220Rn to a depth of 2 m varied temporally in an annual, approximately sinusoidal pattern having an amplitude of twofold to tenfold at all five sites. The existence of the annual pattern is independent of monitoring method, soil drainage, or bedrock parent material. Radon variability is caused by changes in soil moisture content and distribution; the action of soil water on Rn is classified into two distinct regimes: (1) At low and moderate moisture contents, diffusion occurs dominantly in air-filled pores, and Rn is distributed between air and water approximately at equilibrium. Under these conditions Rn in soil air at depth increases with increasing moisture. (2) At high moisture contents diffusion occurs largely in water-filled pores, and air/water equilibrium exists only near interfaces. Under these conditions, Rn in soil air can be low. Since Rn partitioning between gas and water is temperature sensitive and because soil moisture and temperature change in annual cycles, much of the variability in 222Rn concentration occurs in annual cycles. As a result, knowledge of regional and temporal soil moisture and temperature patterns allows estimates of 222Rn concentration in soil gas. In areas where the soil substrate has a significantly lower Ra concentration, emanation coefficient, or dry bulk density than the soil, the substrate can act as a Rn sink with respect to the soil. Under extreme conditions the [Rn] profile in the soil may actually display a concentration gradient toward the rock. The process of horizon formation during soil genesis significantly affects the vertical distribution of Ra, emanation coefficient and porosity, and therefore Rn production in soil.
In this work, the soil-gas method is being used to compare geochemical data with the geological and structural information on Lesbos Island (NE Aegean) in particular in the Aghia Paraskevi–Kalloni region, the epicentral area of an earthquake in 1867. The island belongs to an seismically active zone, part of the right-lateral and normal fault systems of North Anatolia and North and Central Aegean. Field observations, aerial photo interpretation and microearthquake distribution show two main fault systems trending NE–SW to NNE–SSW and NW–SE. The strongest known destructive earthquake hit the island in 1867 with its epicentral area in the central part of Lesbos (estimated intensity IX–X for the most central and eastern part of the island and VI–VII for the rest). The soil-gas sampling was performed in August 1996 in the Aghia Paraskevi area. By this soil-gas survey, an attempt was made for the recognition of active faults, using the soil-gases as fault tracers. High values of all the investigated gases (He, 222Rn, CO2 and CH4) characterize the central and southern sector of the area. The soil-gas anomalous concentrations are probably linked to the very active extensional tectonic structures, that cause the characteristic seismicity of Lesbos (especially those of 222Rn and CO2). After statistical processing of the data and the use of contour and dot-maps of each investigated gas, an important accordance was found between the interpreted linear gas anomalies and the observed faults which possibly generated the 1867 shock.
Vapour levels of metallic mercury in the atmosphere of an abandoned mercury mine and distillation plant at Abbadia S. Salvatore (Mount Amiata, Tuscany, Italy) were detected by means of the mercury accumulation rate in leaves of azaleas located in 100 sampling sites. The response of azalea leaves to a constant mercury concentration in the air (30 ng/L) was calibrated in the field, in relation to indoor conditions. No significant methylation of mercury was found to occur in spontaneous vegetation or contaminated azalea samples. The volatilization of mercury at different temperatures and the use of bioconcentrators to detect mercury vapours in contaminated areas is discussed.
This text provides a review of recent research on geological controls of [sup 222]Rn concentrations in soil gas in relation to the problem of high indoor radon concentrations in houses. The importance of the subject matter is highlighted in the preface by the observation that the US Environmental Protection Agency (EPA) estimates that 15,000 to 25,000 deaths result from radon-induced lung cancer each year in the United States. The text contains 8 Chapters: (1) Geology of radon in the United States; (2) Sensitivity of soil radon to geology and the distribution of radon and uranium in the Hylas Zone Area, Virginia; (3) Geologic and environmental implications of high soil-gas radon concentrations in The Great Valley, Jefferson and Berkeley Counties, West Virginia; (4) Soil radon distribution in glaciated areas: an example from the New Jersey Highlands; (5) Radon in the coastal plain of Texas, Alabama, and New Jersey; (6) Effects of weather and soil characteristics on temporal variations in soil-gas radon concentrations; (7) A theoretical model for the flux of radon from rock to ground water; (8) The influence of season, bedrock, overburden, and house construction on airborne levels of radon in Maine homes. The individual chapters are written by different authors in the form of self-contained research papers, each of which is followed by a comprehensive list of references.
Mercurial, the metaphor for volatile unpredictable behavior, aptly
reflects the complexities of one of the most insidiously interesting and
scientifically challenging biogeochemical cycles at the Earth's surface.
Elemental mercury is readily recognized as a silvery liquid at room
temperature. Its gas phase is important geochemically, since mercury and
some of its compounds have relatively high vapor pressures. Mercury (Hg,
from the Latin hydrargyrum or "watery silver") is sulfur loving (i.e.,
chalcophilic) and extremely active biologically. It is mobilized
tectonically, and significant deposits are found in mineralized regions
characterized by subduction zones and deep-focus earthquakes
(Schlüter, 2000). Many of the major deposits are shown in Figure 1
(Kesler, 1994).
Soil CO2 concentration data were collected periodically from July 2001 to June 2005 from sampling site grids in two areas located
on the lower flanks of Mt. Etna volcano (Paternò and Zafferana Etnea–Santa Venerina). Cluster analysis was performed on the
acquired data in order to identify possible groups of sites where soil degassing could be fed by different sources. In both
areas three clusters were recognised, whose average CO2 concentration values throughout the whole study period remained significantly different from one another. The clusters with
the lowest CO2 concentrations showed time-averaged values ranging from 980 to 1,170ppm vol, whereas those with intermediate CO2 concentrations showed time-averaged values ranging from 1,400 to 2,320ppm vol, and those with the highest concentrations
showed time-averaged values between 1,960 and 55,430ppm vol. We attribute the lowest CO2 concentrations largely to a biogenic source of CO2. Conversely, the highest CO2 concentrations are attributed to a magmatic source, whereas the intermediate values are due to a variable mixing of the two
sources described above. The spatial distribution of the CO2 values related to the magmatic source define a clear direction of anomalous degassing in the Zafferana Etnea–Santa Venerina
area, which we attribute to the presence of a hidden fault, whereas in the Paternò area no such oriented anomalies were observed,
probably because of the lower permeability of local soil. Time-series analysis shows that most of the variations observed
in the soil CO2 data from both areas were related to changes in the volcanic activity of Mt. Etna. Seasonal influences were only observed
in the time patterns of the clusters characterised by low CO2 concentrations, and no significant interdependence was found between soil CO2 concentrations and meteorological parameters. The largest observed temporal anomalies are interpreted as release of CO2 from magma batches that migrated from deeper to shallower portions of Etna’s feeder system. The pattern of occurrence of
such episodes of anomalous gas release during the observation period was quite different between the two studied areas. This
pattern highlighted an evident change in the mechanism of magma transport and storage within the volcano’s feeder system after
June 2003, interpreted as magma accumulation into a shallow (<8km depth) reservoir.
The importance of study of heavy metal distribution in river sediments is a component in understanding the exogenic cycling as well as in assessing the effect of anthropogenic influences of the elements. In India, the river Subernarekha flows over Precambrian terrain of Singhbhum craton in the eastern India. The geological succession in this part of India is through (1) iron ore series, (2) ultrabasic igneous rocks, (3) diorite, (4) granite, (5) newer dolerites, (6) newer tertiary and (7) alluvium. The first four groups belong to the Archaean era, and the representative is the iron ore series consisting of iron ore, manganese and chromite which are abundantly present. The primary rock types are schist and quartzite layers. One main tributary, the Kharkhai flow through granite and schist and quartzite layers. Two important creeks are Gurma and Garra, respectively. The former after originating in basic igneous area travels through schist quartzite, while the later one originates in granite area where some functional but old gold mines are located. Freshly deposited sediments of river were collected upstream and downstream the industrial zone (East Singhbhum district). Samples were collected from four locations and analysed in <63 μm sediment fraction for heavy metals like Ni, Co and Cr by adsorption stripping voltammetry on hanging mercury drop electrode and Hg by anodic stripping voltammetry using polished rotating gold disk electrode. Enrichment of these metals over and above the local natural concentration level (NCL) has been calculated and applied to determine metal-pollution index (MPI) proposed by Goncalves et al. and also geo-accumulation index (I
geo) by Muller. Based on Muller’s classification, Ni, Cr and Hg have been classified from unpolluted to moderately polluted range in pre-monsoon period but for metals Ni and Cr, during the post-monsoon period the values have reached moderately polluted level while Hg has been classified under unpolluted to moderately polluted level except at the monitoring station situated upstream to Gurma Creek where it was found at unpolluted level. Presence of natural resources of the minerals is primarily the reason for their detection in river sediments (lithogenic) but some anthropogenic sources are also contributing for their presence at some sampling stations. Hg is considered to be chalcophilic in nature and is detected wherever known sulphidic ores of copper or nickel are present.
Little information is available on the long-term reproducibility of radon in soil gases, or on the vertical distribution of radon concentrations in soil gas. For five sites in central Pennsylvania, the radon activity in soil gas at depths exceeding about 70 cm varies by factors of 3 to 10 during the year, and shows even larger variability at shallow depths. At depths greater than about 70 cm, values are lower in winter than in summer, apparently because radon is retained in the soil in some form other than the air phase, perhaps in soil moisture or sorbed on solids, as a result of increased moisture or decreased temperature during winter. The low radon values in winter are observed at depths below the frozen surface zone, so they do not result directly from freezing. Values at depths shallower than about 70 cm at one site studied in detail appear to average slightly higher in winter than in summer, but with erratic highs and lows defining a 3-fold annual range. At two other sites, the shallow values show patterns similar to the deep values, with highs in summer. Vertical profiles show reversal and other features differing from previous models for simple diffusive transport. Sampling during the summer period at depths greater than 75 cm shows the best reproducibility for these soils.
A soil gas survey has been carried out in the Vulsini Mts. volcanic area, around Bolsena Lake, with the objective of testing the reliability of this geochemical method for geothermal exploration. The thermal gradient is high all over the area; the He/Ne ratio, and He, CO2, and H2 concentrations have been determined in 259 samples (2 per km2, over an area of 130 km2). Compared with its surroundings, this area exhibits an overall positive CO2 anomaly, but the distribution of diffusive gases (He and H2) allows us to distinguish three different sectors around the lake: (1) a northern sector with high CO2, and H2/CO2, He/CO2, and He/Ne ratios close to the background value; (2) a south-eastern sector, characterized by the presence of cold fumaroles, with high He, H2, CO2 and He/Ne, and generally low H2/CO2 and He/CO2; (3) a southern sector with generally atmospheric He and CO2 and few high H2 and CO2 spots. Permeability is assumed to be the main factor controlling the differences between the above three sectors. In sector 1, the flysch (1 km thick) is intruced by a great number of sills and dikes, and the underlying limestones are completely metamorphosed into marbles; CO2 (thermometamorphic?) is the late stage of a heavy degassing process. Sector 2 includes several volcanic spatter cones along the tectonic trends; the high permeability allows the deep gases to be ducted with minor changes. Sector 3 is an elongated strip with an anti-Apennine trend; diffusion of H2 only is the result of the thick (>3 km) unaltered flysch cover. In sector 3 the underground outflow of the lake through shallow volcanics entrains large quantities of air and masks any deep gases; the few anomalous spots reproduce situations like that of sector 2. One of these spots is located near a producing well tapping the geothermal reservoir.
Soil gas 220Rn and 222Rn concentrations were measured at sites in Chester and Aberdeen, New Jersey (NJ). Two years of 222Rn and 220Rn data were obtained from a depth of 0.85 m, followed by two years from depths of 0.28, 0.56, 0.85, and 1.28 m. Variations of 220Rn and 222Rn, before the first winter that sample tubes were installed, were larger than later, indicating that the soil structure, disturbed during installation of the tubes, may have significantly redistributed after the first winter, thus ensuring that the sample was drawn from near the bottom of the tube. At the Chester site, autumn 222Rn concentrations were found to be up to 10 times higher than winter values, variations larger than predicted assuming diffusion-only transport. Spatial variations up to an order of magnitude were observed over distances of a few meters. The 220Rn concentrations were typically ∼2 to 3 times higher during summer than during winter. At the Aberdeen site, 220Rn and 222Rn concentrations were about an order of magnitude less than the lowest Chester site values with no statistically significant temporal or spatial variations. Permeability, thought to be an indicator of parameters controlling soil gas Rn variations, showed poor correlations with 220Rn or 222Rn at both sites.
Anomalies have been observed in Rn content in soil gas from 3 boreholes at the Orlica fault in the Krško basin, Slovenia. To distinguish the anomalies caused by environmental parameters (air and soil temperature, barometric pressure, rainfall) from those resulting solely from seismic activity, the following approaches have been used: (i) deviation of Rn concentration from the seasonal average, (ii) correlation between time gradients of Rn concentration and barometric pressure, and (iii) regression trees within a machine learning program. Approach (i) is much less successful in predicting anomalies caused by seismic events than approaches (ii) and (iii) if ±2σ criterion is used and is equally successful if ±1σ is used. Approaches (ii) and (iii) did not fail to observe an anomaly preceding an earthquake, but show false seismic anomalies, the number of which is much lower with (iii) than with (ii). Model trees are shown to outperform other approaches. A model has been built which, in the seismically non-active periods when Rn is presumably influenced only by environmental parameters, predicts the concentration with a correlation of 0.8. This correlation is reduced significantly in the seismically active periods.
The Pechelbronn oilfield (Rhine Graben, France), where mining activity ended in the 1960s, has been used for waste disposal for twenty years. Since the wastes are varied, work is underway to identify the discharged materials and their derivatives, as well as to locate and quantify potential discharge sites. Two major goals were assigned to the present work. The first was to identify or refine the location of hidden structures that could facilitate gas emanation up to the surface, by studying soil gas concentrations (mainly (222)Rn, CO(2), CH(4) and helium) and carbon isotope ratios in the CO(2) phase. The second was devoted to examining, from a health and safety viewpoint, if the use of the oilfield as a waste disposal site might have led to enhanced or modified gas emanation throughout the area. It appeared that CO(2) and (222)Rn evolution in the whole area were similar, except near some of the faults and fractures that are known through surface mapping and underground observations. These (222)Rn and CO(2) anomalies made it possible to highlight more emissive zones that are either related to main faults or to secondary fractures acting as migration pathways. In that sense, the CO(2) phase can be used to evaluate (222)Rn activities distant from tectonic structures but can lead to erroneous evaluations near to gas migration pathways. Dumping of wastes, as well as oil residues, did not appear to have a strong influence on soil gaseous species and emanation. Similarly, enhanced gas migration due to underground galleries and exploitation wells has not been established. Carbon isotope ratios suggested a balance of biological phenomena, despite the high CO(2) contents reached. Other monitored gaseous species (N(2), Ar, H(2) and alkanes), when detected, always showed amounts close to those found subsurface and/or in atmospheric gases.
Lobes of the lichen Pseudevernia furfuracea (L.) Zopf and shoots of the moss Hypnum cupressiforme Hedw. were subjected to different treatments (water washing, oven drying, HNO3 washing, NH4-oxalate extraction) to assess the influence of vitality on accumulation efficiency, during a 6-week exposure in bags in two Italian cities, Trieste and Naples. No trend emerged between treatments, in terms of accumulation ability, for major and trace elements. Only water-washed lichens showed an increased C and N content after exposure in both cities. Element concentrations generally reached higher values in mosses than in lichens, especially for Al, Fe, and Zn (both cities), and for Cu, Mg and Na (Naples). Surface development strongly influenced accumulation capacity of the biomonitors. Quartzose and cation exchange filters revealed, on a weight basis, a poor performance. In urban environments, surface interception of atmospheric particulate seems to play a major role in accumulation, irrespective of organism vitality.
To enhance the reliability of the moss and lichen transplant technique for active biomonitoring of trace metals in urban environments, we evaluated the natural variability in the chemical composition of the (epilithic and epiphytic) moss Hypnum cupressiforme and the epiphytic lichen Pseudevernia furfuracea from two reference areas in NE Italy. Green shoots of epilithic mosses and lobes of epiphytic lichens from larch branches showed rather homogenous composition and were selected for the exposure in nylon bags. As different physico-chemical pre-treatments are usually applied to selected cryptogamic material before its exposure, we also evaluated the effects of oven-drying at 120 degrees C for 24h, washing in 1N HNO3 solution, and in 0.5% NH4 oxalate solution at 85 degrees C for 15 h on the chemical composition and morphology of water-washed moss shoots and lichen lobes. Pre-treatments remarkably changed the chemical composition of selected materials but not their surface morphology.
Vertical profiles of radioactive radon gas ((222)Rn) and dissolved gaseous mercury (DGM) in seawater in the Mediterranean Basin have been measured. They were found in the range 1.7-19.3 Bq m(-3) and 22-200 ng m(-3), respectively, at the bottom and 2.0-20.0 Bq m(-3) and 6-80 ng m(-3), respectively, at the surface. Preliminary results indicate a positive correlation between concentrations of both gases at some locations, but not at others. Further analyses will be performed, after (226)Ra contents in sediment and water have been determined, taking into account environmental parameters such as air and water temperatures, barometric pressure and water flow, in order to better interpret these profiles.
Recent advances in surface geochemical prospecting have enabled age-old seep-detection technology to be used to determine the gas versus oil character of a potential fairway. Extensive field work has demonstrated that the chemical compositions of near-surface hydrocarbon soil gases, measured by flame ionization gas chromatography, are largely determined by the hydrocarbons in nearby underlying reservoirs. By using compositions and ratios of the light hydrocarbons, methane, ethane, propane, and butane, one may predict whether oil or gas is more likely to be discovered in the prospect area. Geochemical profiles over known production areas are shown for the Sacremento and San Joaquin basins in California and for the Utah-Wyoming Overthrust belt. Geochemical predictions were documented by subsequent drilling near the Pineview field in Utah. Geochemical prospecting must be used with caution, and only in conjunction with geologic and geophysical tools. Refs.
Anomalous concentrations of methane, ethylene, helium, and hydrogen are found in overburden gases from depths of 6 m (19.7 ft) over the subcrop of a major fault that intersects the Gingin gas reservoir, Western Australia. A helium anomaly (5.5-5.8 ppm), with no associated hydrocarbon anomaly, is present over the subcrop of a fault within the nearby Bootine structure. Normalization of the helium data with neon-20 eliminates much of the anomaly, leaving only two sites over Gingin and the single site at Bootine with above-background helium concentrations. At other sample sites, the elevated helium concentrations are reduced to near atmospheric values and, thus, must be due to residual enrichment resulting from the consumption of major gas components, presumably by near-surface biologic processes. Ethylene, hydrogen, and perhaps some methane are products of these processes. However, the restricted occurrence of the overburden-gas anomaly over a fault and the presence of anomalous Câ-Câ alkanes and helium suggest that gas is leaking from the reservoir. Therefore, the biologic activity causing the helium enrichments is probably due to alkane-oxidizing microorganisms. Such microorganisms are likely to be present in all oil and gas seeps; hence, the expression of such seeps shown by surface gas surveys will always be a combination of near-surface biogenic effects and deep-seated thermogenic effects. 6 figures, 4 tables.
The Geosat test site at Patrick Draw, Wyoming, was resampled during the summer field season of 1983, to conduct a more detailed soil-gas survey on and around the area's producing fields. The results of this study agree with the 1980 Geosat assessment that the faults and fractures visible as linear features on satellite and aircraft imagery provide paths for active microseepage of hydrocarbons from depth to the near surface. Discriminant analysis suggests that the geochemical seepage signature found over the fields differs statistically from that present for adjacent areas of no known production. This observation was found to be true for all three soil-gas techniques used in this study. Anomaly patterns appear to be related to the type of soil-gas sample studied.
Adsorbed, free, and headspace soil-gas samples collected from the Patrick Draw field, Wyoming, were analyzed by routine geochemical techniques. Gas chromatography was used to determine the light-hydrocarbon (C 1 to C 7 paraffins) concentrations in the samples. Anomalous hydrocarbon concentrations appear in those areas near lineaments mapped from Landsat images of the Patrick Draw field. This approach should prove particularly helpful in frontier areas where predictive information would be valuable.-from Authors
Carbon dioxide, oxygen and radon concentrations in soil atmospheres have been investigated for use in geochemical exploration under the effects of changing meteorological conditions. Three localities in the United Kingdom were studied: fluorite-barite-sulfide orebodies at Kenslow Farm and Long Rake in Derbyshire and the tungsten stockworks at Hemerdon, Devon. The contrast between soil-gas compositions over orebodies and those over surrounding rocks varied considerably over several months, but shorter-term variations were less marked. Soil-gas geochemistry provides the exploration geochemist with valuable information, particularly when rapid, on-site analytical techniques are employed.
Orientation surveys were conducted over five deposits to test the potential of determining helium in overburden gas as a pathfinder for uranium mineralization and other deposits containing uranium or thorium. Samples were collected via fixed tubes emplaced at depths of 6 m in backfilled holes drilled for this purpose. Compared to the atmospheric background value of 5.24 ppm v/v He, a variable weak anomaly (maximum 5.45–5.65 ppm He) was found over part of the Angela uranium deposit, N.T., in an arid area where mineralization is mostly at a depth of 60–90 m, at or below the water-table. Helium contents were mostly at background levels over a uranium deposit in the Officer Basin, W.A., where mineralization is at the water-table at 30–35 m, although radon gave a marked anomaly. Neither helium nor radon indicated the Manyingee deposit, W.A., which has uranium mineralization in a confined aquifer at 60–110 m. Similarly, no helium anomalies were found over the uranium- and thorium-rich Mt. Weld carbonatite or mineral sands at Eneabba.
The applicability of Hg as a pathfinder for base metal mineralization has been investigated in an Australian case-history-based study. The principal objectives of the project were: (a) to compare the behaviour of Hg with that of the target elements in the secondary environment with reference to the intensity and extent of the anomalies around outcropping base metal mineralization under varying conditions of climate and geomorphology; (b) to determine whether vapour-generated Hg anomalies can be detected in surface media over buried and blind mineralization, and if so under what geological, geomorphic and climatic conditions; (c) to define the most appropriate sampling media and methods for use in Hg surveys; (d) to develop appropriate techniques for the determination of Hg in geological samples.
Several gaseous elements and compounds have been found to occur in anomalous concentrations in soil gas or air over mineral deposits. These gases or vapors include mercury, sulfur dioxide, carbon dioxide, hydrogen sulfide, fluorine, chlorine, bromine, and iodine. Ore deposits buried by as much as several hundred meters of barren or postmineral overburden have been detected, and buried faults, fractures, and zones of tectonic disturbance have been mapped by use of gas anomalies. Some gases are measured directly with sensitive instrumental methods while others are concentrated and analyzed by traditional analytical methods. Temperature, barometric pressure, and other meteorological parameters influence gas anomalies, although their effects are incompletely understood. Gas anomalies extend the usefulness of geochemical exploration in the search for buried ore deposits.
Adsorbed, free, and headspace soil-gas samples collected from the Patrick Draw field, Wyoming, were analyzed by routine geohemical techniques. Gas chromatography was used to determine the light-hydrocarbon (Câ to Câ paraffins) concentrations in the samples. Anomalous hydrocarbon concentrations appear in those areas near lineaments mapped from Landsat images of the Patrick Draw field. These lineaments represent extensional faults and fractures produced during development of the Rock Springs uplift to the west. Because several of these mapped lineaments extend to depth, they are able to serve as conduits allowing the preferential microseepage of hydrocarbons to the surface from the reservoir rock. These effusive soil gases, in the Patrick Draw area, indicate the nature of the expected hydrocarbons at depth. Further, by targeting easily observable, pervasive lineaments, studies of this nature might be useful as a fast and economical means to screen out or high-grade areas of potential hydrocarbon plays. This approach should prove particularly helpful in frontier areas where predictive information would be valuable.
Mercury anomalies in soils in geothermal areas form as a result of vapor transport. Comparison of the Hg distribution in Long Valley, measured in 1975 and again in 1982, indicates that a new Hg anomaly formed in the Inyo crater zone in the intervening period. Two models can explain this new anomaly: (1) geothermal water has reached shallow levels as a result of increased permeability created by seismic activity, or (2) addition of a CO2-rich, magnetic vapor to the geothermal system at depth caused vapor exsolution in zones where it did not occur before. If the Hg anomaly in the Inyo crater zone is related to the addition of magmatic vapors, the site of the new anomaly may overlie young, intruding magma. *Present Address: Department of Earth and Environmental Sciences, Wesleyan University, Middle-town, Connecticut 06457
The diurnal variations in soil-gas helium concentration have been monitored at depths of 0.5-2.0 m in three localities in Colorado, Wyoming, and Californa. Barometric pressure, air temperature, wind speed, soil temperature and moisture, relative humidity, and precipitation were also measured. The helium variation below a 1-m sampling depth usually did not exceed the analytical sensityivity of 10 ppm He. The meteorologic parameters that have the greatest effect on helium variation are wind speed and precipitation; another factor is the atmospheric pumping created by air temperature changes and its associated effect on near-surface soil moisture content. The absolute helium variation rarely exceeds 1% of the back-ground helium concentration in air and can easily be compensated for because it follows a regular daily pattern. Similar diurnal changes in soil-gas helium concentration would not impose any severe limitations on the use of these data for earthquake prediction purposes.
Considerable variation occurs at one aseismic location in the emission rate of mercury and emanation rate of random from the earth. Improvements are made in the use of seasonal parameters to explain variance in mercury emission. The rate of emission of mercury and radon have contrasting seasonal fluctuations. This may be the result of radon emanation being dominated by diffusion and possible convection processes, whereas mercury emission is strongly influenced by sorption of mercury by soil particles. An understanding of the non-seismic induced variation in gas emission processes may allow reliable application of these techniques to earthquake prediction. The data presented suggest randon offers more promise than mercury in this application.
The effect of large-scale atmospheric pressure changes on the 22Rn tlux across the soil-air interface is investigated. Field data collected during 1972 and 1973 show that pressure changes of 1-2'7o associated with the passage of frontal systems produce changes in the 222Rn flux from 20 to 60%, depending upon the rate of change of pressure and its duration. A simple model of molecular ditrusion combined with pressure-induced transport in the soil has been confirmed by laboratory experiments using a vertical column of 226Ra-bearing sand. On the basis of this model, pressure changes of 10-20 mbar occurring over a period of 1-2 days produce Darcy velocities o1' the order ot' 10 -4 cm s-' near the surface of a soil having a permeability of 10 -8 cm 2. The corresponding variations in theRn tlux predicted by the model are in agreement with those observed from valley alluvium in central New Mexico. Radon 222 is an inert radioactive (half-life of 3.8 days) ele- ment that occurs naturally in the surface materials and at- mosphere of the earth. Atmospheric 222Rn originates mainly from the decay of 26Ra (half-life of 1600 yr) atoms that are located in and on the surfaces of the mineral grains in the soils and rocks of the earth's crust. The 6Ra concentration in average soils is of the order of a picogram of 2Ra per gram of dry soil. A fraction of the totalORa produces '''Rn, which is free to migrate in the pore space of the soil. This is termed the 'effective' ORa (Wilkening, 1974) and is dependent upon the surface-to-volume ratio of the mineral grains and weathering processes. Once the 2Rn atoms are in the pore space, they may move through it by molecular diffusion and/or by flow of the interstitial fluid (soil gas). Either or both of these mechanisms may be important. The net rate at whichRn atoms enter the atmosphere across a unit geometric area of the earth's surface is the 2Rn flux. Measured values for land surfaces vary with location from 0.1 to 2.5 atoms cm - s -1 with a mean of 0.75 atom cm - s -1 (Wilkening et al., 1974). Known areas of surface uranium deposits, lava flows, and ice fields are excluded. Fluctuation in 2Rn flux and soil gasRn concentration at a given location produced by changes in atmospheric parameters has been the subject of numerous investigations with conflicting results in some cases (e.g., Kovach, 1945; Kraner et al., 1964; Pearson, 1967; Pohl-Riiling and Pohl, 1969; Wilkening et al., 1974). The studies involving atmospheric pressure indicate that changes of the order of 1% or less may be responsible for variations in the 2Rn flux of as much as 50-100%. The only proposed model for this effect is a qualitative one put forth by Kroner et al. (1964). It states that during periods of decreasing atmospheric pressure, 2Rn rich air is drawn from the ground and during periods of rising pressure, air low inRn is forced into the ground. The case of steady state diffusion of 2Rn from an infinite plane source through aORa-free medium in the presence of a constant gas velocity is given by A. G. Grammakov as quoted by Tanner (1964). Equations for pure molecular diffusion of 2Rn in porous media are discussed by Kraner et al. (1964), Culot et al. (1973), and others. No analytical treatment of transient effects due to pressure-induced transport has been found.
Published data suggest that soil gas helium concentrations of 5.28–5.34 ppm v/v over uranium and hydrocarbon deposits are significantly anomalous compared to the ambient atmospheric background of 5.24 ppm. However, analyses for helium by mass spectrometers having constant-pressure inlet systems, from which most of these data are derived, are subject to errors of equivalent magnitude. These errors arise when the major component composition of unknown and standard gases differ, for the different gases have different flow rates through the inlet system — relative rates being O2 < dry air < water-saturated air < N2 < CO2 ⪡ CH4. Soil gas compositions can vary greatly and, compared to a dry air standard, the flow-rate of a water-saturated gas containing 10% biogenic CO2 will increase, enhancing the apparent He content to 5.33 ppm. Accurate helium analyses can be achieved by using a constant-volume inlet and integrating the detector response over the period of the samples' passage through the detector.
The emission of gas from the earth's crust is a complex process influenced by meteorological and seasonal processes which must be understood for effective application of gas emission to geochemical exploration. Free mercury vapor emission and radon emanation are being measured in a shallow instrument vault at a single nonmineralized site in order to evaluate these influences on gas emission.Mercury concentrations in the instrument vault average 9.5 ng/m3 and range from < 1 ng/m3 to 53 ng/m3 with a strong seasonal effect. Mercury has a direct relationship to vault temperature, air temperature, soil temperature, barometric pressure, water table, and the frozen or thawed state of the soil. Air and soil temperature, barometric pressure, and relative humidity are most important in influencing mercury emission while soil moisture is also important in radon emanation. Diurnal cycles are common but do not occur on all days. A heavy precipitation event on a dry soil seals the soil resulting in a rise in mercury concentration. Precipitation on a soil that is already wet does not increase mercury emission because of the compensation caused by lowering of the soil temperature by the precipitation event. Freezing of the soil changes the physical state of the vault-soil-soil gas-atmosphere system and emits the lowest concentrations of mercury. Phase lag effects are likely important. Stepwise multiple regression of mercury as dependent variable with meteorological and seasonal parameters as independent variables gives a cumulative R value of 0.563 and R2 of 0.317. The short-term noise coupled with phase lags are an important factor.The radon measurements integrated over weekly intervals smooth out much of the short-term noise. Stepwise multiple regression of radon as dependent variable with meteorological and seasonal parameters as independent variables gives a cumulative R value of 0.967 and R2 of 0.934. In this portion of the study the variation in the radon emanation is adequately predicted by meteorological and seasonal parameters.
A literature review of the source and occurrence of helium shows that it can, under favorable conditions, lead to the discovery of radioactive ore deposits, oil and gas pools, and fracture zones associated with mineral occurrences. Analytical results show that anomalous helium is present in groundwaters and near uranium occurrences and thus can aid in the identification of uranium occurrences or prospective target areas for uranium exploration.
Mercury is commonly present in trace amounts in base metal sulfides. The chemical characteristics of Hg permit its release from oxidizing sulfides and, being extremely volatile, it can migrate through considerable depths of overburden. Anomalous concentrations of Hg may often be detected in soil gas overlying a deeply buried sulfide source, providing sufficiently sensitive analytical techniques are available such as the new Au thin film Hg detector. Laboratory experiments simulating natural occurrences were used to evaluate the effects of changes in barometric pressure, temperature, and soil moisture on the migration and release of Hg from soil gas. Diurnal changes in barometric pressure affect the emission of Hg in soil gas so as to limit accurate sampling using a static collection system such as plastic hemispheres. By use of a soil pump a pressure gradient is artificially produced, overcoming short term variations in atmospheric pressure. Wet soil inhibits Hg migration in soil gas sufficiently to make accurate measurements difficult. A variety of base and precious metal deposits were tested and in all cases Hg anomalies were detected in soil gas. The most intense and reproducible anomalies occur over high-grade vein deposits, especially those containing Zn-Pb-Ag mineralization. Anomalies over porphyry Cu deposits are less intense and are often difficult to distinguish from normal background variation. Laboratory experiments and field studies indicate that Hg vapor in soil gas is a valuable geochemical prospecting tool.
An analytical solution for simple one-dimensional geometry establishes the basic theory of the movement of 222Rn (radon) in overburden, involding diffusion and convection. The computer-adapted finite-difference method is then used to determine radon concentrations for the following more complex configurations: a two-dimensional source, and multilayered overburden. The key parameters are the radon concentration at the source, the diffustion coefficient of the overburden, and the geometry. This analysis indicates that if diffusion is the only transport process considered, the maximum depth at which uranium mineralization can be detected by the usual types of field equipment is limited to a few tens of meters. However, if convective transfer is also considered, radon attenuation is significantly decreased, e.g., by as much as a factor of 800 for a one-dimensional configuration considered. It appears that an upward velocity component for the movement of radon, or geochemical dispersion of uranium and radium, are needed for long-distance detection of uranium mineralization. -Authors
Helium isotope ratios have been measured in geothermal fluids from Iceland, The Geysers, Raft River, Steamboat Springs and Hawaii. These ratios have been interpreted in terms of the processes which supply He in distinct isotopic ratios ( i.e. magmatic He, ~10 R a ; atmospheric He, R a ; and crustal He, ~0.1 R a ) and in terms of the processes which can alter the isotopic ratio (hydrologic mixing, U-Th series alpha production and weathering release of crustal He, magma aging and tritiugenic addition of 3 He). Using this interpretational scheme, Iceland is found to be an area of hot-spot magmatic He implying an active volcanic source although the data are suggestive of high-temperature weathering release of crustal He incorporated in the geothermal fluids. By comparison to fumarolic gases from Hawaii and Juan De Fuca and Cayman Trench basaltic glass samples, The Geysers contains MOR type magmatic He again implying an active volcanic source possibly a "leaky" transform related to the San Andreas Fault System. Raft River contains only crustal He indicating no active volcanic sources. Steamboat Springs He isotope ratios are distinctly less than typical plate margin volcanics but must still have a magmatic source. A preliminary assessment of the cause for this low ratio is made assuming an "aging" magma source.
A new, innovative method of integrated gas geochemical exploration for petroleum has recently been developed and is being evaluated. The technique involves the shallow burial of Curie-point wire coated with a small amount of activated carbon in a cylindrical container in the topsoil where the carbon interacts with emanating soil gases. A collection period of several days to weeks is employed, depending on soil conditions. After removing the wires from the support apparatus, analysis is conducted using a Curie-point pyrolyzer directly coupled to a quadrapole mass spectrometer. The resulting mass spectra are analyzed by multivariate statistics using the program, ARTHUR. The results of the data analysis have been correlated to the presence of oil and gas along with the effects of gas emission on areal pattern variation. The initial gas geochemical experiments have been conducted over known accumulations of petroleum in the Weld County section of the Denver-Julesburg basin, the southern overthrust belt in central Utah, and the Patrick Draw oil field in the eastern Green River basin of Wyoming. Initial testing of the technique has been over a period extending from June through September 1982. Effects on gas emission rates and pattern variations will be discussed with respect to geologic structure, hydrodynamic factors, soil conditions, and seasonal variations. The advantages and disadvantages of the integrative sampling techniques when compared to conventional gas geochemical methods used in petroleum exploration will also be discussed. Although the technique has been applied to a limited number of areas, the early results show great promise in reducing many of the problems associated with other gas geochemical methods.
To investigate the control on small-scale variation of He in soil gas exercised by minor fracturing, shallow surveys have been carried out over a cave system formed along an approximately orthogonal set of fractures in Devonian limestone in southwest England. The possibilities that He variation could be related to deep-seated, major fractures or hidden mineralisation, and that other soil gases may also be affected by minor fracturing were assessed by contemporary surveys for CO2 and O2. Comparisons of soil gas values with variations in electrical apparent resistivity were also carried out. Location of fractures with direct connection to the cave system was determined by spiking the cave atmosphere with He and then resurveying after equilibration.
Helium emanometry has considerable potential for locating deeply buried uranium deposits. In order to determine whether near surface helium-4 anomalies are present over and in close proximity to deeply buried uranium deposits, helium measurements were carried out at three sites having known uranium ore bodies: the Red Desert in Sweetwater County, Wyoming; Copper Mountain in Fremont County, Wyoming; and Spokane Mountain in Stevens Couty, Washington. At each research site, near surface soil and soil gas (probe) samples were collected. Borehole water and soil gas (collector) samples were also taken at selected locations. The samples were analyzed at the laboratory for their helium, light hydrocarbon, and nitrogen content. In most instances it was not necessary to correct the soil gas data. In determining the quantity of helium-4 present in the soil gas samples, the practical precision was +- 50 ppb. The reproducibility of the helium-4 analyses of the water samples varied from +- 5% to +- 20%. The total error in the calculated soil helium-4 levels ranged from 5% to 10% of the value. The calculated corrected soil, water and oil gas helium-4 results were analyzed employing statistical techniques in order to separate the background and anomalous populations. The anomalous population was divided into five subsets for purposes of data presentation. The data are then presented in the form of histograms, dot maps and anomaly contour density maps.One can conclude that the results from this study confirm that near surface helium anomalies are present in the gas of the soil micropores overlying three types of uranium deposits situated in widely differing geological environments. The data obtained from the soil gas (probe) helium samples are also encouraging in that anomalies were found to be present over portions of the known extent of each of the three deposits.
A mobile mass spectrometer to measure He concentrations has been developed by the U.S. Geological Survey. This instrument has been tested in areas of known uranium deposits, and He anomalies have been found in both soil gas and water. A gas sample is collected in a hypodermic syringe, injected into the spectrometer, and analyzed for He. Over 100 analyses a day can be performed with a sensitivity of 10 parts per billion (ppb). One detailed study conducted in Weld County, Colorado, shows that values for He in soil gas can be contoured to outline an anomalous area and that the anomaly is displaced from the deposit in the direction of groundwater flow. Other studies include the Schwartzwalder uranium mine, Jefferson County, Colorado, where He anomalies may be related to geologic structure; near Ambrosia Lake, New Mexico, where the location of He anomalies are related to groundwater movement; and tests for diurnal effects showing only slight variations probably related to soil-moisture content.
This study presents several one-dimensional mathematical models derived to simulate the distribution of radionuclides in soil overlying uranium ore deposits. The migration of gaseous products away from the ore is simulated by mechanisms of molecular diffusion and advective transport. A homogeneous overburden containing no uranium or radium is assumed throughout. The study is intended to be a first step in analyzing the feasibility of detecting uranium ore by remote geochemical measurements. A steady-state diffusion model predicts the detectability of radon-222 and some of its daughter products several tens of meters from a uranium deposit. In reality this range would be shortened by the masking effect of radon generated in the overlying soil itself. Krypton-85 is found to be only marginally detectable even in the immediate vicinity of the ore. Xenon-133 would be detectable at half the range of /sup 222/Rn. The effect of soil gas motion as an additional transport mechanism is evaluated using both steady-state and transient models. A constant soil gas velocity of 1 x 10/sup -4/ cm/sec causes gaseous radioisotope activities to change by several orders of magnitude. Detectability of uranium could be significantly increased if long-term soil gas motion is confirmed. A transient numerical model is used to simulate barometric influences on the migration of /sup 222/Rn away from an ore deposit. It was found that near-surface effects are +-15% which would not appreciably affect the detectability of uranium by geochemical means.
This is the only book devoted entirely to hydrothermal uranium deposits. It provides a summary of their geology, mineralogy and geochemistry and discusses genetic models for their origin. Uranium-fueled fission reactors will probably be needed for at least the next fifty years to provide an important share of the world's energy. However, concern about the sufficiency of uranium ores which can be mined at reasonable cost and without serious environmental consequences has led to a remarkable renaissance of interest in uranium and its ores in recent years. The first part of the volume deals with the geology and geochemistry of hydrothermal uranium deposits, and discusses genetic models for their origin. The second part contains descriptions of the geology and mineralogy of most of the major hydrothermal deposits of uranium; emphasis is placed particularly on those features which bear on the origin of the deposits. Practicing mining and economic geologists involved in uranium exploration and development will find in this work the most comprehensive summary of current knowledge and the tables and ore deposit descriptions together with their extensive bibliographies will provide an invaluable reference source.
The differences between the CO2 and O2 concentrations in soil air and atmospheric air have been measured where sulfide mineralization occurs beneath transported exotic overburden in semi-arid and arid areas of the USA, South West Africa (Namibia) and Saudi Arabia. These mineralizations are reflected near surface by anomalous levels of CO2 and O2 in soil air, whereas in most cases heavy-metal anomalies are absent. The normal background variability of CO2 and O2 in soil air falls with increasing aridity, and anomaly definition improves with increasing aridity. Thus soil air CO2 and O2 data are potentially useful in exploring for concealed mineralization, especially in regions with an arid climate or conspicuous dry season.
Noble gases have been measured mass spectrometrically in samples collected during 1977 from producing wells at Cerro Prieto. Positive correlations between concentrations of radiogenic (He and 40Ar) and atmospheric noble gases (Ne, Ar and Kr) suggest the following dynamic model: the geothermal fluids originated from meteoric water that penetrated to more than 2500 m depth (below the level of first boiling) and mixed with radiogenic He and 40Ar formed in the aquifer rocks. Subsequently, small amounts of steam were lost by a Raleigh process (0 – 30%) and mixing with shallow cold water occurred (0 – 30%). Noble gases are sensitive tracers of boiling in the initial stages of 0 – 3% steam separation and complement other tracers, such as C1 or temperature, which are effective only beyond this range.
Noble gases were studied in six wells, located on a 4.5 km south to north section across the Larderello field. Depth of wells, flow and gas/steam ratios are known to increase from south to north. Exploitation progressed in the same direction. The following noble gas patterns are observable: (a) Atmospheric Ar, Kr and Xe reflect productions of gas-depleted water at Colombaia 2 and progressively more gas-enriched steam towards the Gabbro wells. (b) Radiogenic4He and40Ar are observed in increasing concentrations from south to north. (c) The radiogenic and atmospheric gases reveal a positive correlation, indicating that the recharging water enters deep into the system, and gets well mixed with the radiogenic gases prior to the steam separation. (d) Gas contents and relative abundances of radiogenic argon decrease with production, thus supplying markers for the degree of exploitation in a well and a guide for optimum well spacing. (e) Excess neon over argon is observed and discussed in terms of crustal origin versus possible fractionation of atmospheric noble gases due to pertial steam separation.
The Roving Automated Rare Gas Analysis (RARGA) lab of Berkeley's Physics Department was deployed in Yellowstone National Park for a 19 week period commencing in June, 1983. During this time 66 gas and water samples representing 19 different regions of hydrothermal activity within and around the Yellowstone caldera were analyzed on site. Routinely, the abundances of five stable noble gases and the isotopic compositions of He, Ne, and Ar were determined for each sample. In a few cases the isotopes of Kr and Xe were also determined and found to be of normal atmospheric constitution.
Measurements in 1981 of the helium content of the Earth's lower atmosphere have given a value of 5.222 ± 0.017 ppm by volume. This value, obtained by isotope dilution mass spectrometry, is 0.3% lower, but in essential agreement with the currently accepted value of 5.239 ± 0.004 ppm determined by Glueckauf in the 1930's. A consideration of processes that could have altered the helium concentration since the 1930's indicates that the concentration could have increased measurably due to release of helium by natural gas production. Possible net helium loss from the atmosphere is, however, not readily quantifiable.
Noble gas elemental and isotopic abundances were measured in steam from four wells in the Baca geothermal reservoir located in the Valles Caldera, New Mexico. The ratio and noble gas elemental abundances relative to 36Ar are all strongly correlated with 1/36Ar, the inverse of the argon content. Ratios of (α,n)-produced 21Ne∗ and radiogenic 40Ar∗ to total 4He (dominantly radiogenic) are nearly constant at 2.1 × 10−8 and 0.20, respectively. The ratio covers a restricted range of 3.9 to 4.8 times atmospheric. The high 3He content of the gas indicates the presence of a helium component ultimately derived from the mantle. Kr and Xe isotopic compositions are close to atmospheric; excess 129Xe∗ is <0.25% of the total 129Xe.The high degree of linear correlation among the various noble gas results strongly suggests that the Baca reservoir contains two distinct fluids that are produced in varying proportions from individual wells. The noble gases in fluid A (~2900 mg/1 C1) are air-like, but with lighter gases and isotopes preferentially enriched. The fluid A 36Ar content is low, only 13% that of 10°C air-saturated water (ASW). The second fluid, B (~ 1700 mg/1 C1), is the dominant carrier of the radiogenic and mantle-derived gases. The heavier non-radiogenic gases are preferentially enriched in fluid B, and its 36Ar content is very low, only 5–7% ASW. The source of the noble gases in fluid A is tentatively ascribed to leaching of the relatively young (<1.4 m.y.) volcanic Bandelier Tuff. The radiogenic gases and mantle-derived helium in fluid B suggest a deeper source, possibly including gases escaping from a magma.
Five surface soils from southeastern Montana were exposed to air containing elemental mercury vapor. The majority of the sorbed Hg was found to volatilize at 100–200°C. The sorbed Hg was resistant to extraction by water, neutral salts, methanol or DTPA. Cysteine, acetylacetone and cupferron showed limited extraction of sorbed Hg, while benzene and to a greater extent, hydrochloric acid and sodium hydroxide demonstrated high removals of sorbed Hg. The observed behavior suggests that elemental Hg may be retained by soils as an organo-complex.
Scattered observations suggest that radon can migrate through the earth for distances of ≳100 m, a process of great potential aid in both earthquake prediction and uranium exploration. It is noted that existing theories predict that fluid convection in the earth, driven by the local geothermal gradient, can occur in areas of relatively high permeability. The velocity of fluid flow may be sufficient to transport radon over large distances before it decays. The convection hypothesis also provides a possible explanation of seasonal effects that have been observed in local and general radon emanation into the atmosphere.
Experimental measurements show no evidence for diurnal variation in exhalation of radon and thoron from soil due to convection induced by thermal gradients in the top few decimeters of soil as suggested by several authors. Estimates based on convective calculations indicate that even in the unlikely event of either vertical temperature gradients large enough to cause vertical instability, or horizontal gradients sufficient to cause significant convection, any effect would be too small to be detected. These same calculations suggest that it is difficult to conceive of cases involving typical thermal gradients in unfractured porous media such as soil where thermally induced convection would play an important role in transport of radon or thoron.
An evaluation of the Hg distribution in soils of the Long Valley, California, geothermal area, was made. A1-horizon soil samples were collected utilizing a grid system from the resurgent dome area and the Long Valley area. In addition, samples were collected in five traverses across three fault systems and four traverses across east-west-oriented gullies to measure the importance of aspect. Additional samples were collected in an analysis of variance design to evaluate natural variability in soil composition with sampling interval distance.The primary objectives of this study were to further evaluate the applicability of anomalously high Hg concentration in soils to exploration for geothermal systems and the importance of secondary controls on Hg concentration in soils above geothermal systems.Statistical analysis indicates that there are two populations of Hg concentrations in soils; one affected by geothermal activity and the other unaffected. Samples from the resurgent dome are shown to be statistically different from the samples collected in Long Valley proper with respect to Hg, organic carbon, and pH. This suggests that secondary influences may be important in controlling Hg distribution in soils.Organic carbon in soils is shown by stepwise multiple regression to be the most important secondary parameter controlling Hg concentration. For the most part, the secondary controls of Hg are overwhelmed in an area of prominent geothermal activity. Some faults exhibit prominent anomalies in total Hg concentration and others do not, indicating the possibility of low levels of hydrothermal activity or effective sealing of faults to gas leakage.The analysis of variance results indicate that there is a regional trend in Hg concentration across the resurgent dome. Soils can be sampled for Hg by utilizing a grid of about 0.4 km spacing. However, some local irregularities appear in this pattern and anomalous areas should be prospected at intervals of 100 m or less.
The adsorption of elemental mercury vapor on a thin (several hundred angstroms) gold film produces resistance changes in the film. An instrument for the detection of mercury based on this phenomenon is simple and rapid and requires no chemical separations other than passage of the vapor sample through a few standard dry filters. The instrument is portable, and the technique is directly applicable to environmental problems and geochemical prospecting. The limit of detection of the prototype instrument is 0.05 nanogram of mercury.
Variations of the helium/argon ratio of gas bubbles in a mineral spring along a fault zone coincide with fluctuations of areal
dilation induced by the earth tide. This observation suggests that deep-seated gases characterized by higher heliumlargon
ratios are squeezed out by stress preceding an earthquake.
Vapor dispersion of mercury and radon at Cachinal, northern
- H A Arias
- M Hale
- J S Webb
Arias, H.A., Hale, M. and Webb, J.S., 1979. Vapor dispersion of mercury and radon at Cachinal, northern Chile. Rev. Geol. Chile, 8: 3-12.
Collection and analysis of soil gases emanating from buried sulfide mineralization, Cochise County, Arizona
- Hinkle
Hinkle, M.E. and Kantor, J.E., 1978. Collection and analysis of soil gases emanating from buried sulfide mineralization, Cochise County, Arizona. J. Geochem. Explor., 9: 209-215.