Patent Number: 053496248
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing in detail, FIG. 1 depicts X-ray tube 10 generating an X-ray beam 12 with sufficient flux and energy to form images of a soil sample 14 pursuant to the present invention. As shown, the soil sample is positioned within an analysis zone between an imaging device 16 and the point source 18 of radiation from X-ray tube 10 along an axis 20 to the image plane 22 of the imaging device. Controlled scanning movement relative to the X-ray beam 12 is imparted to the soil sample 14 along perpendicular scanning axes 24 and 26 intersecting the beam axis 20. Magnification of X-ray images formed on plane 22, on the other hand, is controlled by movement 28 along axis 20 imparted to the soil sample as denoted in FIG. 1. Thus, a controllably scanned and magnified x-ray image of the soil sample is formed at the image plane 22 by generation of the microfocused X-ray beam 12 through equipment associated with X-ray tube 10, such as an X-ray machine operating under a voltage of 80 kv and current of 35 ma. Such a commercially available X-ray machine is marketed, for example, by Feinfocus U.S.A., Inc., as model FSX-100.25. As shown in FIG. 2, the soil sample 14 undergoing examination within the analysis zone between X-ray tube 10 and the image plane 22 is a body of soil 30 contaminated by heavy metal particles 32, including extremely small particles less than one millimeter and as small as 10 microns in size. The contaminated soil body 30 occupies a cylindrical volume formed within a container 34 having circular retainer lids 36 at opposite axial ends. Because the contaminant particles 32 have a significantly higher X-ray absorption coefficient than the low absorption coefficient for the soil alone, the X-ray image 38 of the soil sample as shown in FIG. 3 includes high contrast image feature portions 32' corresponding to the contaminant particles 32. Accordingly, measurement of the size and location of each image portion 32' within its image 38 will provide accurate and useful analysis data from which the size and distribution of the contaminant particles 32 within the body of soil 30 is calculated, based on the geometrical parameters of the soil sample 14 and analysis zone as hereinbefore described with respect to FIG. 1. According to actual analyses performed pursuant to the present invention, the cylindrical soil samples 14 utilized had a diameter (d) of 1/2 inch and a thickness (t) between 0.2 and 0.4 inches. The soil in such sample without contamination had an X-ray absorption coefficient between approximately 0.1 and 0.5 cm.sup.2 /g, which is substantially lower than the X-ray absorption coefficient of the contaminants. The X-ray image 38 as depicted in FIG. 3 may be recorded on photographic film or captured by electronic means through the imaging device 22. Magnification of the X-ray image is varied to accommodate the size range of the contaminant particles to be detected for measurement purposes, up to a maximum magnification factor of about 250:1 under microfocus X-ray capabilities of presently available X-ray machines. Detection of contaminant particles as small as 10 microns is thereby made possible. Detection of the contaminant particles, as dark spot image portions 32' depicted in FIG. 3, may be further enhanced by electronic image processing. The scanning movement imparted to the soil sample 14 as hereinbefore described is utilized to obtain measurement data from which the location of the particles 32 may be calculated. Alternatively, a stream of soil may be moved through the analysis zone for intermittent examination of soil samples. The contaminant particle size and location data so obtained may be digitized and fed to automatic computer controlled equipment for subsequent physical separation of the particles. The X-ray images or views may also be captured and measured electronically to provide digitized data on contaminant particle size and location by computer programmed calculation. The foregoing sample analysis method is depicted in FIG. 4, wherein block 40 represents a source of contaminated soil fed to a sample analysis zone 42 irradiated by the microfocus X-ray beam from source 10 to produce the image display represented by block 44. Scanning and image magnification control respectively denoted by blocks 46 and 48 is exercised as hereinbefore explained in order to enable measurement of magnified image features through a system denoted by block 50. The measurement data output of the system 50 is then utilized to calculate in situ size and location for contaminant particles through a computer program, as denoted by block 52, in order to obtain a data readout 54. As also denoted in FIG. 4 by block 56, the size and location data output of program 52 controls operation of particle separation apparatus to which the contaminant soil is fed after passage through the sample analysis zone 42, in order to obtain separated contaminant particles 58 and contaminant-free soil 60. The particle separation apparatus 56 may utilize, for example, an air stream vacuum technique to produce a stream of the contaminant-free soil denoted by block 60. As a result of the foregoing described method, specific in-situ data on size and shape of contaminant particles is produced, and because of soil sample scanning, precise particle location data is provided as the basis for more efficient use of a particle separation technique as well as to drastically reduce the duration and equipment cost for soil sample assessment. Numerous other modifications and variations of the present invention are possible in light of the foregoing teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.