Lennart Malmqvist

Evidence for nondiffusive transport of 86Rn in the ground and a new physical model for the transport

Concentration of radon has been measured in the soil near the ground surface with solid‐state, nuclear track detectors with the inverted cup technique. Measurements were made in the overburden at depth intervals 0.1–0.7 m, at 0.1–6 m, and at a constant depth of 0.2 m, in a narrow rectangular matrix. The results disagree with the hypothesis that radon concentration only depends upon local production and migration by diffusion with a diffusion length of about 1 m. A transport length of 0.1–0.2 m is observed near the ground surface and the transport is dominated by a flow component. Radon measurements in the ground surface over the Laisvall lead mine have given evidence of radon transport through rock exceeding a distance of 100 m, which is possible only if the migration is a flow transport with a characteristic transport length larger than about 10 m/day. To explain the radon transport in the overburden and through the rock with a common transport system, the existence of a general upward flow of geo‐gas is...

Experimental evidence for an ascending microflow of geogas in the ground

A microflow of free ascending gas has been observed in 26 out of 30 tested boreholes at three different sites. The flow rates vary between 60 × 10−4 and 4 cm3/min m2 horizontally projected borehole area. Sampling has been made in ground boreholes as well as in holes drilled downwards from the lowest levels in two mines. The composition of the gas varies considerably. The main components of the gas are nitrogen, argon, oxygen and methane. Traces of heavier hydrocarbons are observed. At the site of the ground holes, only traces of methane are observed. In all sampled holes the existence of free oxygen is observed. The nitrogen/argon quotient is close to the atmospheric quotient in all sampled holes, indicating a partly atmospheric origin of the gas. The existence of methane and traces of heavier hydrocarbons indicates the existence of a second source.

Trace elements in the geogas and their relation to bedrock composition

Abstract The paper describes an investigation of a transport mechanism in the ground which has the capacity of lifting trace amounts of different elements from the bedrock to the ground surface. The transported matter is guided by a funnel system towards a thin membrane on which it is collected. The matter on the membranes is analysed with the PIXE method. The transport may be brought about by a very weak stream of gas bubbles which passes upwards through cracks and fissures in the bedrock. Remarkable similarities are found between the occurrence of elements on the membranes and the composition of a mineralization straight below the points of collection. The mechanism seems to have the power of revealing the existence of important base metal occurrences in the bedrock and may therefore be the basis for a new method of prospecting for concealed mineralizations.

A physical mechanism for the release of free gases in the lithosphere

Abstract A possible mechanism for the creation of free gas bubbles in the upper parts of the crust is postulated. The creation of a bubble is assumed to be initiated by α-particles produced in the decays of the radioactive elements of uranium, thorium and their daughter products. The gas is assumed to be supplied from groundwater oversaturated with dissolved gases. A bubble formed in this way can ascend through cracks and fissures because of its buoyancy. It remains as a free gas bubble because it passes through a groundwater already saturated with dissolved gases. This phenomenon seems important since it offers a one-way upward transport mechanism for atoms or aggregates of atoms attached to the bubbles through the lithosphere. The bubble creation can be simulated in the laboratory by means of mineral water and an uranium-rich rock sample.

The depth-dependence of the concentration of 86222Rn IN Soil gas near the surface and its implication for exploration

Abstract The depth-dependence of the radon concentration in the soil gas has been studied with cellulose nitrate plastic detectors with the inverted cup technique. The depth dependence can be characterized by the half length, L 1 2 , which is equal to the depth interval in which the radon concentration is changed by a factor of two. The half length is found to be a function of the depth in the soil and of the soil type. Values between 11 cm and 31 cm have been found in measurements close to the surface. Radon measurements made for exploration purposes should be corrected for differences in the depth of measurement and changes in the soil type should be considered. The near surface radon measurements are compared with the diffusional model of radon transport. It is found that for many of the sites of the experiment the results significantly disagree with this transport model irrespectively of the choice of the diffusion model parameters. A model which includes both diffusion and upward flow transport with a carrier gas seems necessary to explain the experimental data. Measurements taken close together at the same depth in the soil have revealed a very irregular concentration pattern indicating that the radon transport is partly a channeling phenomenon. Measurements of the radon concentration and the half length, L 1 2 , have been made along profiles. In one profile there are indications of the channelling of the radon carrier gas along strata of Quaternary deposits.

A New Method for Colour Measurements in Graphic Arts

This article presents a method for colour measurements directly on printed half-tone multicoloured pictures. The article introduces the concept of colour impression. By this concept we mean the CMY ...

Radon migration through soil and bedrock

Abstract To investigate radon migration in the ground a series of measurements have been made along a profile of 160 m length. The radon concentration was measured in the soil at different depths with the inverted cup technique. The emission of radon and the gamma emission were measured on soil samples from the profile and the exhalation of radon from two drill cores taken right below the profile was investigated. The radon profile agreed better with the drill core emission than with the measurements on the soil samples supporting the hypothesis that streaming transport from the bedrock exists and is important.

A method to determine the isotopic composition of cosmic ray carbon

We describe a method to determine the isotopic composition of cosmic ray carbon. As a detector we have used nuclear emulsions which were exposed to the primary radiation in a high altitude balloon flight. The mass determination are based on measurements of the relation between track width and residual range in the range interval 1 < R < 12 mm. The track width has been measured with a nuclear track photometer. The standard deviation of the experimentally determined mass values of 12C nuclei amounts to 2.9 %. We conclude that the method described can be used for studies of the isotopic composition of carbon in the primary cosmic radiation.

Microflow of geogas — A possible formation mechanism for deep-sea nodules — Reply

Abstract A formation model for deep-sea manganese nodules based on ascending bubble trains of geogas is proposed. The bubble train forces material in the sediments and particles adsorbed by the bubbles to the sediment—water interface where precipitation reactions occur. In the presence of a nucleating agent a nodule is formed. Such a model might explain a number of observations concerning nodular structure, genesis and distribution.

The relative abundance of the carbon isotopes12C and13C in primary cosmic radiation

Mass measurements have been performed on stopping cosmic ray carbon nuclei in a nuclear emulsion stack, which was exposed to the primary radiation in a high altitude balloon flight. The mass determinations are based on measurements of mean track width and residual range in the range intervals 0<R<0.75 mm and 1<R<12 mm. The mean track width measurements have been performed with nuclear track photometers of special construction. The mass measurements in the interval 0<R<0.75 mm have given a nearly symmetrical mass distribution. The width of the distribution is equal to that expected for a distribution which contains only one isotope. The result indicates that one of the stable isotopes is appreciably more abundant than the other. The measurements in the range interval 1<R<12 mm gave the isotopic ratio13C/12C+13C)=0.08. The ratio has been extrapolated to the cosmic ray source. It is found to be smaller in the source than at the point of measurement. Different assumptions about the origin of the cosmic radiation are discussed with regard to the results obtained in this investigation.