The distribution of selenium and other trace elements in Texas waters and soils

Abstract

The distribution of selenium in aquatic systems has not been widely investigated. For example, there is very little reliable Se data for Texas river waders. This thesis aims to draw a first order picture of the Se distribution in several Texas rivers. I analyzed 139 water samples collected by Mr. Kuo-Tung Jiann from 8 Texas rivers in 1997 and 1998 for Se before I made two sampling trips to collect waters, soils, sediments, and a few rocks in Feb. 1999 and in May 1999. The distribution I attend of Se in Texas waders indicated that the upper Brazos River, the Colorado River and the Red River had significantly higher Se than other rivers. The waters in the Big Spring area have the highest Se. Most of the Se in waters existed in the dissolved form. A significant correlation between Se and conductivity was found for river waders collected on both trips. However, there was no significant relationship between Se and conductivity for waders collected in the Big Spring area, which might be caused by Se removal from the waders into sediments. Se had good correlations with the major elements because Se behaves conservatively like the major elements in river waters. Se concentrations in soils, sediments and rocks were also determined in this research. The central Texas region of high Se rocks and soils had high Se river water buy there were no significant relations between Se in waters and Se in soils and sediments collected nearby. This indicated that there must be factors in addition to the source of Se in soils controlling the Se concentration in waters. The correlation between Se and Fe and Ca in soils indicates that the majority of Se is probably in inorganic forms. The common cc-occurrence of Se with S in both soils and sediments probably reflects the similar chemical behavior of these two elements, but a chemical bond is not necessarily implied. The correlation of Se with Al, Be, Cu, Fe, and Mg in sediments implies that the Se was removed from the water mainly through adsorption onto inorganic matter.