Studies On Microwave Dielectric Behavior Of Moist Salt Soil And Inversion Of The Moisture And Salt Content

The paper focused on the way to retrieve the soil-water and salt content. To fulfill the purpose, two models, one for imaginary part of soil dielectric constant and one for inverseon model, were put forward respectively. The following was the details about the models:This paper had presented the expressions for imaginary part of dielectric constant of moisture salt soil at low and high frequencies respectively, which is functions of 1) soil water content and 2) soil salt content. This paper carried out a series of relation studies, including: the relation of imaginary part of dielectric constant ε"and soil bulk conductivity σ_a; relation of soil bulk conductivity σ_a and conductivity of soilsolution σ_w ; relation of conductivity of soil solution σ_w and soil solution concentration S_M_v ; and relation of soil solution concentration S_M and soil salt content S have been established gradually (ε" ~ σ_a ~ σ_w ~ S_M_v ~ S). Based on theserelations, the relation of ε"and S,M_v had been established, which is the dielectric imaginary part model for wet and salty soil. Dielectric constants of 150 samples fromfive soil types had been measured with microwave net analyzer at the 396 frequencies that ranged from 0.2GHz to 20GHz with the interval of 0.05GHz. These measured data were applied to calibrate the dielectric imaginary part model and then achieved the calibrated model at different frequencies. In addition, another 41 soil samples in Jilantai had been measured to test the dielectric model; as a result, the calculated value from model and the measured value had a strong correlation.Although the relations of backscattering coefficients and soil-water and salt content are the real problems about inversion, the relation of backscattering coefficients and dielectric constants is the key problem. In addition, a lot of physical geographical features in arid areas, such as the ground surface with sparse vegetation, little soil water in dry seasons, are useful to retrieve physical parameters of the surface. According to these features, using IEM model, which was developed by Fung et al in 1992, generated simulated backscattering coefficients in arid areas. These data included HH and VV polarizations and different seasons (wet and dry seasons) data. Different seasons data were achieved by changing dielectric constant. By analyzing these data, we found: in non-salinized areas, 1) there is a strong correlation (>0.9) between o°wa -o°dry (the difference between the dry- and wet-season SAR a0) and￡wet ~ ￡dry (tne difference between wet and dry seasons surface dielectric constants); and 2) dry-season edry (soil water Mv ) has little effect on the relation of o\a - a°dry and ewa - edry, which ensures there is no need of specific informationabout dry-season soil water in inversion of wet-season soil water. In salinized areas, 3) there is a good correlation between oBwet-a°dry and I(￡wa)-I(ed^,) (the difference between wet and dry seasons imaginary part of dielectric constants) that is related with soil salt content when I{ewel) -l(edry) is great. This may provide a way to monitorsalinization although quantitative inversion is not feasible for imaginary part of dielectric constant is related with both soil water and salt content, it is hard to separate their effects.Conclusions the paper made: 1) Effect of salt content will decrease with the increasing frequency;...