Rapid Nondestructive Bulk Density and Soil‐Water Content Determination by Computed Tomography

Abstract

Computed tomography (Ct) is a promising tool that may help provide measurements needed to obtain finer resolution in soil‐water content and bulk density for water uptake studies or detailed investigation of root‐soil interactions. A need exists for a unified method to accurately predict soil bulk density and water content using output from CT. Research was conducted on soil collected from the A horizon of Mexico silt loam (Udollic Ochraqualfs) and the B2t horizon of Crider silt loam (Typic Paleudalfs) to evaluate the relationship between linear attenuation coefficients and volume fraction of soil solids and water. Air‐dry soil (<2 mm) was packed into polyvinyl chloride cylinders at densities between 1.2 and 1.6 Mg/m3 and CT slices or tomographs were taken before and after water was added. The relationship between attenuation coefficients and volume fraction of soil solids was linear for both of the soils evaluated. Parameter values for the Mexico soil compared favorably with those determined on previous data collected from Metea fine sandy loam (Arenic Hapludalfs). Differences in the parameter values for the Mexico and Crider soils were attributed to differences in Fe content. An experiment with Fe added to the Mexico soil was conducted that verified the effect of Fe content on the attenuation coefficients. Approximately 98% of the variation between the attenuation coefficients and volume fraction of soil water was accounted for by using linear regression relationships after correction for swelling. Results from this study indicate that it may be possible to develop a universal relationship for computed tomography data vs. soil bulk density and water content; however, more research is needed to characterize the influence of sample size on the calibration relationship.

High-resolution X-ray computed tomography in geosciences: A review of the current technology and applications

“…This 3D reconstruction technique was almost immediately used for medical applications, allowing visualisation of the human body and brain (Gawler et al, 1974;Ledley et al, 1974;Paxton and Ambrose, 1974). Applications in other research domains such as wood technology (Onoe et al, 1983;Taylor et al, 1984), palaeontology (Conroy and Vannier, 1987;Zollikofer et al, 1998), soil science (Anderson et al, 1988;Braz et al, 2000;Crestana et al, 1986;Crestana et al, 1985;Petrovic et al, 1982), marine sciences (Boespflug et al, 1995) and geosciences in general (Coles et al, 1991;Vinegar and Wellington, 1987;Wellington and Vinegar, 1987), as well as industrial applications (Hopkins et al, 1981) followed shortly.…”

Computed tomography scan analysis of Site 941 cores, western mass-transport deposit, Amazon Fan

“…In particular, the difference in content of high atomic number elements influences the CT value of the sample even if the bulk density is unchanged (cf. Anderson et al, 1988;Boespflug et al, 1995). In addition, it is proposed that the difference in chemical composition in the samples influences the adequacy of Equation 2.…”

“…Using the empirical relationship between the linear X-ray attenuation coefficient and Fe content ( fig. 6 in Anderson et al, 1988) enables us to estimate the increase in CT value with the increase of the Fe content. As a result, the increase of 0.65 wt%, the difference between 7.75 wt% and 8.40 wt% in the Fe 2 O 3 content, corresponds to the increase of 16 units in the CT value, which corresponds to an error of 0.013 g/cm 3 to the correct bulk density.…”

Magnetic fabric analysis of sediments from the Côte d'Ivoire-Ghana Transform Margin

“…This study also uses CT scan analysis to investigate the density of sediments (e.g., Anderson et al, 1988;Soh et al, 1993;Ashi, 1995). The image of X-ray CT scanning can be obtained by mathematical reconstruction of penetrated X-ray intensity, with its attenuation coefficients calculated from absorption or scattering in objects (Iwai, 1979), which provides high-resolution density information.…”