Near-surface moisture and biomass influences on the reliability of aerial radiometric surveys as a measure of natural radioelement concentrations

Norwine, Jim; Hansen, David J.; Saunders, D.F.; Galbraith, James H.

doi:10.2172/5324651

Cited by 7 publications

(5 citation statements)

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“…The main reasons for such variation of the radiometric signal are: (i) the water content of soils (Grasty, 1997), or the effect of vegetation cover (Norwine et al, 1980), metamorphic or hydrothermal alteration and (ii) superficial weathering effects (Wilford, 1995). Thus, in our opinion, no automatic determination of the lithology can be obtained using libraries.…”

Section: The Use Of Airborne Gamma-ray Spectrometrymentioning

confidence: 99%

“…Finally, the data were gridded with a spacing of 250 m, using a standard bi-directional gridding algorithm, in order to minimise spurious effects induced by the anisotropy of the line data. Over the forest, the canopy absorbs a small part of the gamma-ray emission (Norwine et al, 1980) which, in Guiana, has been determined equivalent to 25 m of air (Delor et al, 1997). The radiometric intensity is therefore slightly attenuated but relative variations are preserved and lateral contrasts related to the geology are recorded.…”

Section: Geophysical Data Characteristicsmentioning

confidence: 99%

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Classifying airborne radiometry data with Agglomerative Hierarchical Clustering: A tool for geological mapping in context of rainforest (French Guiana)

Martelet

Truffert

Tourlière

et al. 2006

International Journal of Applied Earth Observation and Geoinfor

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Section: The Use Of Airborne Gamma-ray Spectrometrymentioning

confidence: 99%

Section: Geophysical Data Characteristicsmentioning

confidence: 99%

Classifying airborne radiometry data with Agglomerative Hierarchical Clustering: A tool for geological mapping in context of rainforest (French Guiana)

Martelet

Truffert

Tourlière

et al. 2006

International Journal of Applied Earth Observation and Geoinfor

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“…For example, Table 1 shows that changes in lithology result in approximately parallel increases or decreases in all three radioelements simultaneously. Moisture in the soil or masses of vegetation cause absorption of gamma rays, and the relative amounts of absorption are generally similar for gamma radiation from thorium, uranium, and potassium (Norwine et al, 1980). Also, differences in counting geometry, because of topographic irregularities, will cause parallel variations in all three elements (Ward, 1981).…”

Section: Suppression Of Lithologic and Environmental Effectsmentioning

confidence: 99%

Tests of Australian aerial radiometric data for use in petroleum reconnaissance

Saunders¹,

Branch²,

Thompson³

1994

GEOPHYSICS

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Recon Exploration Pty. Ltd. has successfully completed initial testing of a new method for processing and interpretation of AGSO’s (Australian Geological Survey Organization, formerly Bureau of Mineral Resources) aerial gamma‐ray spectrometer data for petroleum exploration in the Canning Basin, Western Australia and the Otway Basin, Victoria. Count‐rate data for potassium and uranium were normalized to the thorium count rate for each sample to suppress unwanted effects of variations in surface lithology or soil type, soil moisture, vegetation cover, and counting geometry. The Canning Basin test area included five producing oil fields. All except one clearly exhibit significant and characteristic radiometric anomalies which include negative normalized potassium and more positive normalized uranium values. The Otway Basin test areas included PPL-1 commercial gas production which is associated with a group of significant radiometric anomalies similar to those in the Canning Basin. These results are similar to extensive ongoing tests in the U.S. and are explained in terms of well‐understood geological, geochemical, and geophysical models. Based on 69 wells in the three test areas, it is estimated that the chance of encountering hydrocarbons (economic production or shows) in wells within the radiometrically favorable zones is about 2.6 times greater than outside the favorable areas.

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“…Environmental gamma-ray spectroscopy measurements are influenced by plenty of experimental boundary conditions which knowledge help in interpreting radiometric data at different levels according also to the spatial scale of the surveys. Airborne gamma-ray spectroscopy already raised the attention on the attenuating effects on the gamma signal due to the presence of vegetation (Dierke and Werban, 2013;Norwine et al, 1979;Sanderson et al, 2004;Wilford et al, 1997). However, the presence of biomass in terms of plants, leaves and fruits is expected to play a much more critical role in proximal gamma-ray surveys, which implies that an accurate estimate of the signal reduction is needed.…”

Section: Introductionmentioning

confidence: 99%

Biomass water content effect on soil moisture assessment via proximal gamma-ray spectroscopy

et al. 2019

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Proximal gamma-ray spectroscopy supported by adequate calibration and correction for growing biomass is an effective field scale technique for a continuous monitoring of top soil water content dynamics to be potentially employed as a decision support tool for automatic irrigation scheduling. This study demonstrates that this approach has the potential to be one of the best space-time trade-off methods, representing a joining link between punctual and satellite fields of view. The inverse proportionality between soil moisture and gamma signal is theoretically derived taking into account a non-constant correction due to the presence of growing vegetation beneath the detector position. The gamma signal attenuation due to biomass is modelled with a Monte Carlo-based approach in terms of an equivalent water layer which thickness varies in time as the crop evolves during its life-cycle. The reliability and effectiveness of this approach is proved through a 7 months continuous acquisition of terrestrial gamma radiation in a 0.4 hectares tomato (Solanum lycopersicum) test field. We demonstrate that a permanent gamma station installed at an 2 agricultural field can reliably probe the water content of the top soil only if systematic effects due to the biomass shielding are properly accounted for. Biomass corrected experimental values of soil water content inferred from radiometric measurements are compared with gravimetric data acquired under different soil moisture levels, resulting in an average percentage relative discrepancy of about 3% in bare soil condition and of 4% during the vegetated period. The temporal evolution of corrected soil water content values exhibits a dynamic range coherent with the soil hydraulic properties in terms of wilting point, field capacity and saturation.

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Near-surface moisture and biomass influences on the reliability of aerial radiometric surveys as a measure of natural radioelement concentrations

Cited by 7 publications

References 0 publications

Classifying airborne radiometry data with Agglomerative Hierarchical Clustering: A tool for geological mapping in context of rainforest (French Guiana)

Classifying airborne radiometry data with Agglomerative Hierarchical Clustering: A tool for geological mapping in context of rainforest (French Guiana)

Tests of Australian aerial radiometric data for use in petroleum reconnaissance

Biomass water content effect on soil moisture assessment via proximal gamma-ray spectroscopy

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