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Reconnaissance scale mapping of salinity in three‐dimensions using EM38 and EM34 data and inversion modelling
Author(s) -
Wang Jie,
Zhao Xueyu,
Zhao Dongxue,
Arshad Maryem,
Zare Ehsan,
Triantafilis John
Publication year - 2020
Publication title -
land degradation and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.403
H-Index - 81
eISSN - 1099-145X
pISSN - 1085-3278
DOI - 10.1002/ldr.3684
Subject(s) - environmental science , soil salinity , soil science , salinity , transect , inversion (geology) , remote sensing , geology , soil water , geomorphology , oceanography , structural basin
In irrigated areas, the spectre of soil salinisation is ever‐present. To obtain baseline data to map salt, or the soil electrical conductivity of a saturated soil paste extract (EC e , dS m −1 ), we use electromagnetic (EM) data from a survey of EM38 and EM34 data with EM inversion software (EM4Soil). This is because the collected apparent electrical conductivity (EC a , mS m −1 ) can be inverted to estimate true electrical conductivity ( σ , mS m −1 ) and correlated with EC e . To do this we use a quasi‐two dimensional (Q‐2D) model along a pseudo‐transect, which includes seven soil sample locations, to make a linear regression (LR) calibration between σ and EC e (i.e., EC e = 0.0122 × σ − 0.0535 [ R 2 = .71]). From the joint inversion of interpolated EM38 and EM34 EC a across 40,000 ha, a quasi‐three dimensional (Q‐3D) model was then used to predict EC e . The model was validated using 30 soil sample locations scattered across the area. The agreement between predicted and measured EC e was moderate (Lin's concordance = 0.59) and conclude that useful information on a reconnaissance scale can be obtained and indicates where more detailed information may be collected to confirm areas of moderate salinity. To better predict EC e , more EC a could be collected on smaller grid spacings (i.e., 0.5 km and 1 km in irrigated and dryland areas, respectively). To improve resolving depth of EC e we recommend including EC a from a single‐frequency multiple‐coil array DUALEM‐421.