A Novel Water-Soluble Compounds Extraction Technique for Geochemical Surface Soil Exploration

Soil salinization is a major environmental process in arid and semi-arid regions, whereby more than 37% of salinized soils are located in deserts. Traditionally considered a constraint for agriculture and land productivity, salinization also offers a unique opportunity for geochemical exploration. Water-soluble forms of elements in soils reflect changes of environmental settings and play a significant role in soil salinization. The accumulation of specific elements in shallow soils is utilized in the present study as indicator for their secondary migration and dispersion from deeper-situated strata. In particular, elements from Groups I and II of the periodic table (e.g., Na, K, Ca, Sr, and Li) display high mobility under saline and alkaline conditions, often accumulating in shallow soil layers due to capillary rise and evaporation. An efficient and rapid water-based extraction technique was developed with high-accuracy ICP-OES instrumentation to identify anomalies of such water-soluble forms of elements in soil samples. The presented methodology was applied to 36 soil samples—including 32 aridisols and 4 sabkhas—from geochemically diverse landscapes of the Arabian Peninsula to identify geochemical anomalies linked to deeper sources of strategic elements. Significant anomalies in the abundance of Li, Na, K, and Be were detected for specific samples with an excess of up to 40 times relative to the median abundance. Soils with detected anomalous concentrations of strategic elements can serve as alternative source for mining purposes. The developed technique provides a faster and more accurate analytical procedure of extensive sample volumes for the mapping and identification of enhanced elemental accumulation in soil.