Theses and Dissertations at Montana State University (MSU)
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Item Distribution, characterization, and dietary risk assessment of indigenous salts in Mongolia's Darhad Valley(Montana State University - Bozeman, College of Agriculture, 2008) Barber, Loren Mickelle; Chairperson, Graduate Committee: Cliff Montagne.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.Item Water use potential and salt tolerance of riparian species in saline-sodic environments(Montana State University - Bozeman, College of Agriculture, 2004) Sessoms, Holly Nicol; Chairperson, Graduate Committee: James W. Bauder.Salinization of soil and water resources exists on a global scale, largely due to irrigated agriculture in semi-arid climates. Coal bed methane (CBM) development, resulting in the co-production of saline-sodic discharge water, is a potential new source of salinzation in the Powder River Basin of Montana and Wyoming. Constructed wetlands may serve to reduce CBM product water volumes while applying saline-sodic product water to a beneficial use. The objective of this study was to assess the potential of constructed wetlands as a new management tool for CBM product water management. To accomplish this, riparian species native to Montana and Wyoming and classified as halophytes were selected as experimental treatments. Species chosen were subjected to saline-sodic conditions designed to mimic CBM product water for a 24-week period and harvested once every 8 weeks. Water use rates, water chemistry, biomass production, forage value, and salinity tolerance of each species were monitored throughout the experimental period. Due to turbulent airflow and high diffusion rates of water vapor from the plant canopy, plant water use rates of mature plants exceeded reference evaporation rates over a range of salinities for most species. For high water use species, ratios between plant water use rates and reference evaporation exceeded 3.00 at lower salinities. High ratios between plant water use and reference evaporation indicate that reference evaporation buckets were not subjected to the same evaporative conditions as the plant canopy, and may not represent potential evapotranspiration. Biomass production of traditional wetland species declined following defoliation and under increasing salinity. Grass species increased biomass production following defoliation and under elevated salinity in the third growth period. Crude protein (CP) also decreased with progressive harvests for wetland species, but increased in the third period for grass species. Based on percent acid detergent fiber and CP, forage value of most species is equal to or greater than average grass hay forage value. Results suggest that wetlands constructed of species analyzed will thrive in salinesodic conditions, and will outperform or perform similarly to evaporation ponds for CBM product water disposal while providing a forage resource and beneficial use.