Distribution, characterization, and dietary risk assessment of indigenous salts in Mongolia's Darhad Valley
Barber, Loren Mickelle
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Natural salt deposits around the world are used as human and livestock dietary mineral sources. The nomadic herders of the Darhad Valley, in northern Mongolia, harvest the precipitate that forms around saline lakes throughout their valley. The precipitate is termed hujir, and the main harvest location is Tukh. Darhad people are concerned about the declining amount of a hujir in the Tukh precipitate area and are curious about possible health effects related to hujir consumption. These studies focus on formulating the best management practices for sustainable hujir harvest by evaluating factors influencing the formation of hujir, and by establishing the mineralogy and ionic concentrations in Tukh soil, water, and hujir through chemical and spatial analyses. A dietary risk assessment was also accomplished by obtaining consumption rates through interviews, and determining exposure values from the consumption rates and ionic concentrations. Exposures were compared to chronic oral endpoints to relate potential health risks. A map of Tukh was created using Global Positioning System and Geographic Information System technologies and acts as baseline spatial data on the area. Minerals present include trona, halite, calcite, and other evaporites. According to pH and EC results, the area used for human harvesting at Tukh is more saline than the remainder of the lake. The soil profile within the precipitate area showed a TDS of 49 mg/L and pH of 7.2 in the surface horizon relative to an EC of 0.4 mg/L and a pH of 6.4 lower in the profile. This indicates a presence of capillary rise from groundwater, resulting in evaporation and salt precipitate at the soil surface. High exposure of arsenic, antimony, and lead compared to U.S. Environmental Protection Agency and World Health Organization endpoint values resulted in risk quotients of 33, 1.7, and 14, respectively, which create concern in the population's hujir consumption. Further epidemiological and biomonitoring research would provide insight in the health relationships to hujir consumption. Future research could benefit from the resulting spatial and chemical data completed in these studies.