Evaluating and Maps of Chemical Weathering Indices for Gypsiferous Soils Using Geospatial Techniques

Abstract

Abstract The study aims to evaluate the status of chemical weathering of gypsiferous soils in Baiji District, Salahaldeen Governorate, Iraq, using geospatial techniques. The total area of the study is 85.24 km2. Seven soil pedons (P) were selected, and their morphology was described according to the American Soil Survey Staff principles. Soil samples were obtained from the horizons, and 56 soil samples were obtained from the surface layer 0-20 cm. The total oxides content were estimated using Spectro X-LAB 2000 XRF. Chemical weathering indices CIA, WIP, CWI, PIA, STI, MWPI, CPI, CVI, MIA (0) were calculated. The geospatial maps were prepared using the kriging interpolation model, and calculating of the strength of spatial dependence using the GS+ program. Spatial distribution maps were prepared using the IDW spatial derivation technique using the ArcGIS Ver program 10.3. The results revealed spatial variation in the distribution of oxide content and chemical weathering indicators vertically and horizontally, generally, the weathering processes are relatively weak. We note from the descriptive statistics results that the chemical indicators’ values were relatively homogeneous, with the coefficient of variation (CV%) values being less than 23.56%. The spatial reliability values ranged between moderate and strong for most of the chemical indicators, and the least effective distance was for the MWPI index, which amounted to 292m.