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Fashionable Techniques for Assessment of Groundwater Potential, Pollution, Prevention, and Remedial Measures
Published in M. Thangarajan, Vijay P. Singh, Groundwater Assessment, Modeling, and Management, 2016
R. Annadurai, Sachikanta Nanda
Groundwater applications of near-surface geophysics include mapping the depth and thickness of aquifers, mapping aquitards or confining units, and locating preferential fluid migration paths such as groundwater and that from saltwater intrusion.
Groundwater investigation using ground magnetic resonance and resistivity meter
Published in ISH Journal of Hydraulic Engineering, 2021
Uttam Singh, Pramod Kumar Sharma, C. S. P. Ojha
The physical property used in near-surface geophysics applications of NMR is the spin of the hydrogen protons in water molecules. The magnetic spin is an intrinsic property of an atom that possesses an angular momentum, without physically rotating, and an associated magnetic moment (Coates et al. 1999; Walsh 2008; Dalgaard et al. 2012). When the magnetic moment of the hydrogen protons is situated within a static magnetic field (B0), they possess the static magnetic field at the Larmor frequency where 0.2675 × 109 s−1T−1 is the proton gyrometric ratio and represents the Larmor angular frequency. The Larmor frequency depends on the static field strength, which ranges over multiple orders of magnitude for geophysical NMR measurements (Dunes et al. 2002; Levitt 2001). For surface NMR measurements, the static field is Earth’s magnetic field (), which ranges from about 25 to 65 , corresponding to Larmor frequencies ranging from about 1.06 to 2.8 kH. For borehole NMR, the static field is generated by the instrument and the field strength ranges from 5.75 to 57 mT corresponding to Larmor frequencies ranging from 0.245 to 2 MHz. Geophysical lab-NMR studies use instruments with a large range of magnetic field strengths. Measurements can be collected using Earth’s magnetic field or using instruments with field’s strengths up to 9.4 T; this corresponds to Larmor frequencies on the order of kHz to 400 MHz (Levitt 2001).