Uso do GPR na Identificação da Interface Água Doce/Água Salgada em Cordões Arenosos da Praia de Itaipuaçú – Município de Maricá (RJ)

Pereira, Alípio José; Gambôa, Luiz Antônio Pierantoni; Silva, Maria Augusta M. da; Costa, Ariovaldo da; Rodrigues, Amilsom Rangel

doi:10.3997/2214-4609-pdb.168.arq_188

Cited by 2 publications

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“…Ground‐penetrating radar (GPR) and electrical methods have been applied with success to locate the fresh‐water/seawater interface in the subsoil (e.g. Pereira et al ), and to map the location of NAPL spills on the basis of the dielectric and electrical properties (Greenhouse et al ; Benson ; Daniels et al ; Carcione et al ; Carcione and Seriani ; Osella et al ; de la Vega et al ; Carcione et al ). In fact, at radar frequencies, NAPLs have, in general, lower permittivity and conductivity than groundwater.…”

Section: Introductionmentioning

confidence: 99%

Fresnel reflection coefficients for GPR‐AVA analysis and detection of seawater and NAPL contaminants

Carcione

Gei

Botelho

et al. 2005

Near Surface Geophysics

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We obtain the transverse electric (TE) and transverse magnetic (TM) Fresnel reflection coefficients for different interfaces in the subsoil: air/fresh‐water, air/seawater, fresh‐water/seawater, air/NAPL (non‐aqueous phase liquid), NAPL/water and water/NAPL. We consider a range of NAPL saturations, where the complementary fluid is water with 0.65 ppt (parts per thousand) of NaCl. The common feature is that the TM mode (parallel polarization) has a negative anomaly and the TE mode (perpendicular polarization) has a positive anomaly. For the cases studied in this work, pseudo‐Brewster angles appear beyond 40° for the air/NAPL and NAPL/water interfaces and at near offsets (below 40°) for the water/NAPL interface. Pseudo‐critical angles are present for the water/NAPL interface. Besides the reflection strength, the phase angle can be used to discriminate between low‐ and high‐conductivity NAPL, when the properties of the upper medium are known. A wavenumber–frequency domain method is used to compute the reflection coefficient and phase angle from synthetic radargrams. This method and the curves can be used to interpret the amplitude variations with angle (AVA) of reflection events in radargrams obtained with ground‐penetrating radar (GPR).

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