Effect of Salinity on the Dielectric Properties of Geological Materials: Implication for Soil Moisture Detection by Means of Radar Remote Sensing

We consider the exploitation of dielectric properties of saline deposits for the detection and mapping of moisture in arid regions on both Earth and Mars. We present simulated and experimental study in order to assess the effect of salinity on the complex permittivity of geological materials and, therefore, on the radar backscattering coefficient in the [1-7 GHz] frequency range. Laboratory measurements are performed on sand/sodium chloride aqueous mixtures using a vectorial network analyzer coupled to an open-ended coaxial dielectric probe. We aim at calibrating and validating semiempirical dielectric mixing models. In particular, we evaluated the dependence of the real and imaginary parts of complex permittivity on the microwave frequency, water content, and salinity. Our results confirm that if the real part is mainly affected by the moisture content, the imaginary part is more sensitive to salinity. In addition to the classic formulas of mixing models, the ionic-conductivity losses, which are due to mobile ions in the saline solution, are taken into account in order to better assess the effect of salinity on the dielectric properties of mixtures. Dielectric mixing models are then used as input parameters for the simulation of the radar backscattering coefficients by means of an analytical model: the integral equation model. Simulation results show that salinity should have a significant impact on the radar backscattering recorded in synthetic aperture radar data in terms of the magnitude of the backscattering coefficient. Moreover, our results suggest that VV polarization provides a greater sensitivity to salinity than HH polarization.

[1]  Nicolas Baghdadi,et al.  Subsurface structures detection by combining L-band polarimetric SAR and GPR data: example of the Pyla Dune (France) , 2001, IEEE Trans. Geosci. Remote. Sens..

[2]  Kang Li,et al.  Bilayered dielectric measurement with an open-ended coaxial probe , 1994 .

[3]  Pascale C. Dubois,et al.  Measuring soil moisture with imaging radars , 1995, IEEE Trans. Geosci. Remote. Sens..

[4]  Adrian K. Fung,et al.  Backscattering from a randomly rough dielectric surface , 1992, IEEE Trans. Geosci. Remote. Sens..

[5]  D. Möhlmann,et al.  Water in the upper martian surface at mid- and low-latitudes: presence, state, and consequences , 2004 .

[6]  T. Schmugge,et al.  An Empirical Model for the Complex Dielectric Permittivity of Soils as a Function of Water Content , 1980, IEEE Transactions on Geoscience and Remote Sensing.

[7]  F. Bonn,et al.  Potentiality of RADARSAT-1 images in the detection of salt affected soils in the arid zone: Wadi El-Natrun, Egypt , 2003, IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477).

[8]  F. Ulaby,et al.  Microwave Backscatter Dependence on Surface Roughness, Soil Moisture, and Soil Texture: Part I-Bare Soil , 1978, IEEE Transactions on Geoscience Electronics.

[9]  A. Shutko,et al.  Mixture Formulas Applied in Estimation of Dielectric and Radiative Characteristics of Soils and Grounds at Microwave Frequencies , 1982, IEEE Transactions on Geoscience and Remote Sensing.

[10]  Stanislaw S. Stuchly,et al.  An Equivalent Circuit of an Open-Ended Coaxial Line , 1983, IEEE Transactions on Instrumentation and Measurement.

[11]  P. V. Narasimha Rao,et al.  Dielectric properties of salt-affected soils , 1995 .

[12]  F. Ulaby,et al.  Microwave Dielectric Behavior of Wet Soil-Part 1: Empirical Models and Experimental Observations , 1985, IEEE Transactions on Geoscience and Remote Sensing.

[13]  J. Kong,et al.  Theory of microwave remote sensing , 1985 .

[14]  Amalendu Chandra,et al.  Frequency dependence of ionic conductivity of electrolyte solutions , 2000 .

[15]  Ramata Magagi,et al.  MODELLING THE BACKSCATTERING COEFFICIENT OF SALT-AFFECTED SOILS: APPLICATION TO WADI EL-NATRUN BOTTOM, EGYPT , 2004 .

[16]  Kun-Shan Chen,et al.  A reappraisal of the validity of the IEM model for backscattering from rough surfaces , 2004, IEEE Trans. Geosci. Remote. Sens..

[17]  J. A. Lane,et al.  Dielectric dispersion in pure polar liquids at very high radio frequencies - III.The effect of electrolytes in solution , 1952, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[18]  J R Carr,et al.  Establishing a relationship between soil moisture and RADARSAT-1 SAR data obtained over the Great Basin, Nevada, U.S.A. , 2004 .

[19]  Qin Li,et al.  A generalized power law spectrum and its applications to the backscattering of soil surfaces based on the integral equation model , 2002, IEEE Trans. Geosci. Remote. Sens..

[20]  Huadong Guo,et al.  Microwave dielectric behavior of moistsalt soil - experimental observations and improved dielectric models , 2003, IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477).

[21]  Peter K. Weyl.  ON THE CHANGE IN ELECTRICAL CONDUCTANCE OF SEAWATER WITH TEMPERATURE 1 , 1960 .

[22]  Philippe Paillou,et al.  Effect of multiple scattering on the phase signature of wet subsurface structures: applications to polarimetric L- and C-band SAR , 2005, IEEE Transactions on Geoscience and Remote Sensing.

[23]  F. Ulaby,et al.  Microwave Dielectric Behavior of Wet Soil-Part II: Dielectric Mixing Models , 1985, IEEE Transactions on Geoscience and Remote Sensing.

[24]  Jiancheng Shi,et al.  Estimation of bare surface soil moisture and surface roughness parameter using L-band SAR image data , 1997, IEEE Trans. Geosci. Remote. Sens..

[25]  A. Stogryn,et al.  Equations for Calculating the Dielectric Constant of Saline Water (Correspondence) , 1971 .

[26]  M. A. Stuchly,et al.  Equivalent circuit of an open-ended coaxial line in a lossy dielectric , 1982, IEEE Transactions on Instrumentation and Measurement.

[27]  V. H. Kaupp,et al.  Generalized refractive mixing dielectric model for moist soils , 2004, IEEE Transactions on Geoscience and Remote Sensing.

[28]  Huadong Guo,et al.  Effect of dielectric properties of moist salinized soils on backscattering coefficients extracted from RADARSAT image , 2003, IEEE Trans. Geosci. Remote. Sens..

[29]  William V. Boynton,et al.  Global distribution of near-surface hydrogen on Mars , 2004 .

[30]  V. L. Mironov,et al.  Frequency dispersion in microwave for complex permittivity of bound water stored in soils and wet salts , 1999, IEEE 1999 International Geoscience and Remote Sensing Symposium. IGARSS'99 (Cat. No.99CH36293).

[31]  D. Ritson,et al.  Dielectric Properties of Aqueous Ionic Solutions. Parts I and II , 1948 .

[32]  Kun-Shan Chen,et al.  Note on the multiple scattering in an IEM model , 2000, IEEE Trans. Geosci. Remote. Sens..

[33]  Philippe Paillou,et al.  A phase signature for detecting wet subsurface structures using polarimetric L-band SAR , 2004, IEEE Transactions on Geoscience and Remote Sensing.

[34]  H. Falkenhagen,et al.  The Principal Ideas in the Interionic Attraction Theory of Strong Electrolytes , 1931 .

[35]  Peter Coppo,et al.  A further study of the IEM surface scattering model , 1997, IEEE Trans. Geosci. Remote. Sens..

[36]  Rajat Bindlish,et al.  Subpixel variability of remotely sensed soil moisture: an inter-comparison study of SAR and ESTAR , 2002, IEEE Trans. Geosci. Remote. Sens..

[37]  Yangjun Zhang,et al.  New density-independent moisture measurement using microwave phase shifts at two frequencies , 1999, IEEE Trans. Instrum. Meas..

[38]  Nigel H. Hancock,et al.  Dielectric behavior of moist swelling clay soils at microwave frequencies , 1997, IEEE Trans. Geosci. Remote. Sens..

[39]  Kamal Sarabandi,et al.  An empirical model and an inversion technique for radar scattering from bare soil surfaces , 1992, IEEE Trans. Geosci. Remote. Sens..