Mapping potential salt minerals over Wadi El Natrun saline lakes, Egypt, using remote sensing and geophysical techniques

Abstract

Salt mineral characterization and mapping in soils are a persistent environmental concern worldwide to achieve effective use, exploration, and management of salts. We apply and develop integrated procedures of remote sensing (RS) and geophysical techniques verified by the field work to characterize and map the natural saline lake precipitation. As a research case study, the suggested approach is applied at Wadi El Natrun depression, which is one of the well-known geomorphological features at the northern part of Egyptian Western Desert. Wadi El Natrun saline lakes consist of sodium chloride, sodium sulfate, and sodium carbonate. Moreover, the economic saline lakes are rich in halite salts. Obviously, RS data can (i) represent the different environmental salt zones and (ii) characterize the types and distributions of the salt-rich sediments in each of such lakes. Moreover, the surface geology discrimination and temporal change detections of the lakes are achieved. Considering the surface salt zone characterization, the subsurface salts are investigated by the electrical resistivity tomography (ERT) and time domain–induced polarization (TDIP) methods to locate the salt-rich deposit occurrence. The 2D electrical models derived from ERTs and TDIP measurements point out to geological layers that are compatible with the available borehole data. The resistivity models indicate two main geoelectrical layers corresponding to shale, shaly sand, and salt-rich shale. Specifically, the chargeability of models enable to discriminate between the salt-rich deposits and shaly sand layer clearer than resistivity models. Accordingly, the integration of RS and electrical resistivity data can characterize and map the salt zones in a cost-effective way. Concluded in general, the present approach can be applied elsewhere and opens the way for detailed in situ mineralogical investigation at Wadi El Natrun saline lakes.