Groundwater vulnerability to selenium in semi-arid environments: Amman Zarqa Basin, Jordan.

An evaluation of approximately 250 samples of groundwater in the Amman Zarqa Basin for selenium along with other major and trace elements showed that concentrations of Se ranged between 0.09 and 742 microg/L, with an average value of about 24 microg/L. Selenium concentrations exceeded the recommended threshold for drinking water of the World Health Organization (WHO; 10 micro/L of Se) in 114 samples, with greater than 50 microg/L (quantity equivalent to the Jordanian standard of the allowed concentration of the element in water) of Se in nine cases. The average concentrations of Se in the lower, middle, and upper aquifers of the basin were 3.41, 32.99, and 9.19 microg/L, respectively. Based on the correlation with geologic formations and the statistical analysis of major/minor constituents and Piper tri-linear diagrams, we suggest that carbonate/phosphate dissolution, oxidation-reduction processes, and fertilizers/irrigation return flow are, together, the primary factors affecting the chemistry of the groundwater. Factor analysis helped to define the relative role of limestone-dolomitic dissolution in the aquifers (calcium, magnesium, and bicarbonate), agricultural activities (sulfate, nitrates, phosphorus, and potassium), oxidation-reduction factor (Eh, Fe, Mn, Cu, Zn, and Se), and anthropogenic (industrial) factor (EC, Fe, Cr, Co, Zn, and As). The high variability in Se concentrations might be related to the possibility of a multi-source origin of Se in the area.

Low levels of toxic elements in Dead Sea black mud and mud-derived cosmetic products.

Natural muds used as or in cosmetics may expose consumers to toxic metals and elements via absorption through the skin, inhalation of the dried product, or ingestion (by children). Despite the extensive therapeutic and cosmetic use of the Dead Sea muds, there apparently has been no assessment of the levels of such toxic elements as Pb, As, or Cd in the mud and mud-based products. Inductively coupled plasma mass spectrometry analysis of eight toxic elements in samples collected from three black mud deposits (Lisan Marl, Pleistocene age) on the eastern shore of the Dead Sea in Jordan revealed no special enrichment of toxic elements in the mud. A similar analysis of 16 different commercial Dead Sea mud cosmetics, including packaged mud, likewise revealed no toxic elements at elevated levels of concern. From a toxic element standpoint, the Dead Sea black muds and derivative products appear to be safe for the consumer. Whatever the therapeutic benefits of the mud, our comparison of the elemental fingerprints of the consumer products with those of the field samples revealed one disturbing aspect: Dead Sea black mud should not be a significant component of such items as hand creams, body lotions, shampoo, and moisturizer.