Uncovering the effects of Urmia Lake desiccation on soil chemical ripening using advanced mapping techniques.

[Display omitted] • Soil chemical ripening was identified following Urmia Lake desiccation. • The spatial distribution of geochemical indices was successfully mapped using satellite imageries. • The geochemical indices demonstrate the transition from geogenesis to pedogenesis. • Ba/Sr emerged as the best index for detecting soil chemical ripening. • Digital mapping of the ripening process assists in interpreting pedogenesis. Urmia Lake in Iran has been gradually drying up since the 2000 s, revealing soil that was once underwater. There is limited research on how this drying process affects the distribution of soil chemical ripening in the lakebed sediments. To investigate this, 131 surface soil samples were collected in July 2017 from six zones based on their distance from the lake's shoreline. Elemental concentrations in the samples were measured using a portable X-ray fluorescence (XRF) spectrometer. Five geochemical indices (GCIs) were calculated: Titanium/Zirconium, Barium/Strontium, Silicon/Aluminium, Silicon/R 2 O 3 , and the Darmody index. A remote sensing image (Landsat-8 OLI) from the same sampling period was used as environmental covariates to explain the spatial distribution of GCIs. Random forests (RF) and cubist tree models were employed to model and map these GCIs. The bootstrapping method was used to assess the uncertainty of the maps. Results indicated that the RF model performed better than the cubist model based on the concordance values in the validation dataset. Remotely sensed clay minerals ratio and normalized burn ratio were identified as the most significant covariates in making predictions. The study found that the distribution of all geochemical indices was directly related to their distance from the shoreline. Ba/Sr emerged as the best index for detecting soil chemical ripening in the study area. The index displayed the most significant differences between the drying zones. This research demonstrated that combining satellite imagery with GCIs using the digital soil mapping (DSM) technique can effectively detect soil ripening progression. [ABSTRACT FROM AUTHOR]