Electromagnetic Radiography (EMR) for the detection of low-level chemical contamination in the ground

摘要

Abstract: Electromagnetic Radiography (EMR)$+TM$/ provides direct, high- resolution images of low-level chemical contamination in the ground at concentration levels in the parts-per-billion range ($mu@g/kg). This new sensor system can distinguish between dense, non-aqueous phase liquids (DNAPLs) and light, non- aqueous phase liquids (LNAPLs). Ionic chemicals can be distinguished from non-ionic chemicals, and dissolved-phase chemicals in the water table can be distinguished from liquid- phase contaminants in the vadose zone trapped in the pore spaces of the soil. EMR$+TM$/ is derived from high-performance ground-penetrating radar (GPR). Like its predecessor, EMR$+TM$/ provides direct images of subsurface geologic structures, including faults, fracture zones, bedrock profiles, bedding planes, clay lenses and infiltration zones. The system employs electromagnetic impulses in the radio- frequency range of 30 MHz to 480 MHz. Specific chemicals have been found to produce unique responses in this frequency domain, leading to the discovery that discrete energy bands are being excited at the molecular level. Much work remains to be done on the characterization of specific chemicals in the radio-frequency (RF) domain. Meanwhile, conventional soil testing can be used to identify the chemicals and 'calibrate' the EMR$+TM$/ field data. It is now possible to use non- intrusive remote sensing techniques to map the lateral and vertical distribution of specific low-level chemical contaminants on a production basis. The EMR$+TM$/ system is currently capable of providing 100 percent volumetric inspection of 3 to 5 acres per day to a depth of several meters, including clay. !0