George N. Mungai1, 2*, Hellen N. Njenga1, Eliud M. Mathu3 and Vincent O. Madadi1
1Department of Chemistry, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya
2Department of Physical Sciences, Meru University of Science and Technology, P.O. Box 972 60200, Meru, Kenya
3Department of Geology and Meteorology, South Eastern Kenya University, P.O. Box 170-90200, Kitui, Kenya
Abstract
Carbonated spring waters are natural sources of trace minerals considered to have important biological and therapeutic functions. However, some trace elements are toxic to the human body upon exposure even at low concentration levels. Ten carbonated springs located in Meru County, on the Eastern Slopes of Mt. Kenya were investigated to determine the levels of trace elements. The host communities draw the carbonated mineral waters regularly for drinking, cooking, watering the livestock and selling. Cavity ring-down spectroscopy was used for the analysis of dissolved inorganic carbon in the spring waters and inductively coupled plasma-optical emission spectrometry for the determination of the following trace elements: As, B, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se and Zn. Host rocks analysis for major toxic elements As, Cd, Cr, Cu, Hg and Pb was done by X-ray fluorescence. The reported dissolved inorganic carbon in the waters was significant ranging from 39.2-89.0 mmol/kg and this enhanced dissolution of minerals from rocks due to the presence of carbonic acid. Levels of As in six springs ranged from 11.1 to 21.5 μg/L and exceeded the 10 μg/L WHO recommended limit for drinking-water. There was a strong positive correlation with r = +0.8, between As levels and dissolved inorganic carbon. The other elements were within the safe limit. Toxic elements in the rocks ranged from As 30-170 ppm, Cd <10 ppm, Cr <10-100 ppm, Cu 40-180 ppm, Hg <10 ppm and Pb <10-370 ppm. Therefore, water-rock interaction contributed significantly to the presence of toxic elements in the carbonated waters. Arsenic (As) is a well-known carcinogen and poses many other health risks to humans. An epidemiological study on clinical manifestations of As toxicity in the region as well as removal of As from the waters prior to consumption are recommended.
Keywords:
Arsenic toxicity, carbonated springs, mineral waters, trace minerals
