Fluoride as an (eco)hydrological tracer in in semiarid mountainous streams: insights from comparing F/Cl ratio and water stable isotopes (δ18O y δ2H)

MACCHIOLI GRANDE, M.; POCA, M.; LARROVERE, M. A.; URAN, G. M.; JOBBÁGY, E.

San Luis

Workshop; I Regional Workshop on Isotope Ecohydrology; 2020

Mountainous semiarid streams are the main source of water for most of northwestern Argentina. The composition of these natural surface waters is controlled by weathering of the crystalline basement which crops out in this region. Some of these rivers contain high levels of fluoride, because of dissolution of F-bearing minerals from granitic rocks. Semiarid conditions would favor evaporative concentration of fluoride, similar to what occurs to its sister halogenide chloride, despite the former is mostly retained in minerals, and therefore has a different hydrochemical behavior. Additionally, little is known about F bio-accumulation, and whether F can be a good tracer of different sources of water uptake by plants. Therefore, the concentration of F in plants of different use of water (riverine vegetation vs crops irrigated with groundwater) could also help understanding the dynamic of this element in the plant-soil system, and assess a possible use as an ecohydrological tracer.