Date of Award
Master of Science (MS)
The objective of this paper is to test and review some of the published hypotheses as that may relate to selenium geochemistry in soil and water system at the Hovland Ranch, Haakon County, South Dakota. Representative samples were collected from soil, water, and soil moisture in the field. Preparation of samples and chemical analysis were done in the Water Quality Laboratory, Dept. of Geology and Geological Engineering, University of North Dakota and Human Nutrition Research Center Lab, USDA/ARS, Grand Forks, North Dakota. The analysis results were statistically analyzed to find correlation between the occurrence of selenium and other associated chemical elements in the soil and water system in the ranch area.
Both total and water soluble selenium in the soil and water samples is significantly positively correlated to sodium, sulfate, and phosphorus. Water soluble selenium is mostly selenate. Selenite is below detection limit in the water soluble extracts of soils. Very little total selenium is water soluble, with an average of only 2%. Selenium is significantly positively correlated to arsenic in both water soluble and acid extracted soil extraction and soil moisture samples. Total organic maintains a positive correlation with selenium. Selenium in the water and soil moisture samples is positively correlated to electrical conductance. Nitrate-nitrogen shows positive correlation with selenium in soil extracts, but the correlation is negative for water and soil moisture samples. Calcium has very little or no correlation with selenium in both the soil (water soluble extracts) and water samples. But calcium has positive correlation with selenium in the acid extracted soil samples. Total selenium maintains no correlation with depth. Water soluble selenium shows poor but significant negative correlation with depth. Water soluble selenium shows poor but positive correlation with elevation. Total selenium has very little spatial variation over the area with insignificant standard deviation, but the spatial distribution of water soluble selenium is distinct with high standard deviation.
All the chemical analysis data suggest that sodium, magnesium and sulfate minerals create a major geochemical sink for water soluble selenium. The solubility of these salts may be the principal factor controlling the mobility and transport of selenium in the soil-water environment.
Sharif, Salah U., "Effect of geochemical processes and environment on the spatial pattern of selenium in soil, surface water, and groundwater at the Hovland Ranch, central South Dakota" (2003). Theses and Dissertations. 273.