Impacts of fluorite dissolution in semiarid endemic soil and ecotoxic effect estimated in Allium cepa.

Abstract

Fluorite (CaF₂) leaching and weathering (30 days) were conducted to measure fluoride dissolution in semiarid endemic soil and controlled synthetic solutions, and determining the main chemical species involved in these processes via atomic force microscopy (AFM), X-ray diffraction (XRD) and Scanning electron microscopy (SEM-EDS). Ecological health response in this system was assessed exposing Allium cepa bulbs to 10, 50, 100, 450, 550 and 950 mg CaF₂ kg^-1 soil to determine genotoxic damage, protein and systemic fluorine concentrations. Results indicated 3 cycles of passive-active fluorite dissolution enabling fluoride concentrations up to 164 mg L^-1 under endemic conditions; however, highest fluoride dissolution was 780 mg L^-1 for synthetic sulfates solution. Cyclic behavior was associated with the formation of ultrafine-sized calcite (CaCO₃)-like compounds. Fluorine concentrations ranged from 5 to 300 mg kg^-1 in vegetable tissue. The electrophoretic profiles revealed changes in the protein expression after 7, 15 and 25 days of exposure. Genotoxic damage rate was 50, 82 and 42% for these exposures (950 mg CaF₂ kg^-1 soil). The dose‒response curves of the normalized total protein content revealed the kinetics vegetable health damage rates for only 7 and 25 days. This behavior was best adjusted for only 7 days. These findings exhibited characteristics for initial damage and adaptation-recovery stage after 15 days. Environmental implications of these findings were further discussed.