Origin of Fluoride and Arsenic in the Main Ethiopian Rift Waters

Minerals

Claudio Natali¹  Tewodros Rango Godebo²  Chiara Marchina³  Gian Marco Salani⁴  Alessandro Rasini⁴  Gianluca Bianchini⁴  Valentina Brombin⁴ 

[1] Department of Earth Sciences, University of Florence, 50121 Florence, Italy;Department of Environmental Health Sciences, Tulane University, New Orleans, LA 70112, USA;Department of Land, Environment, Agriculture and Forestry, University of Padua, 35020 Padua, Italy;Department of Physics and Earth Sciences, University of Ferrara, 44122 Ferrara, Italy;

关键词: fluoride and arsenic;    Main Ethiopian Rift;    water–rock interaction;    weathering;    tolerance limit;    geogenic contamination;   

DOI  :  10.3390/min10050453

来源: DOAJ

【 摘 要 】

In the Main Ethiopian Rift (MER) area, rural populations often use water that exceeds the World Health Organization thresholds for fluoride (F^–) and arsenic (As), two elements that are hazardous for human health. In this study, twenty-nine water samples were collected from lakes and hot and cold springs in southern MER to investigate source(s) and health-risk of the F^– and As contamination. According to major ion and trace element analyses, only cold spring water is safe for consumption, whereas hot spring water is the most contaminated. Leaching tests performed with the MER rhyolitic volcanic rocks and their weathered products (fluvio-lacustrine sediments) demonstrate that the main cause of the F^– and As release is geogenic, i.e., not related to anthropogenic activities. The weathering of volcanic glass and minerals (apatites, clays, hydro-oxides) by CO₂-bearing alkaline water induces the mobilisation of F^– and As from solid to liquid phase. This process is particularly fast, when fluvio-lacustrine sediments are involved, and can be further enhanced by hot groundwater leaching. This study, investigating the distribution, sources, and mechanisms of F^– and As release in MER water, could be of interest also for other sectors of the East African Rift and other similar volcano-tectonic settings.

【 授权许可】

Unknown