GEOTECHNICAL AND ENVIRONMENTAL IMPACTS OF STEEL SLAG IN EMBANKMENTS

Steel slag is a byproduct of iron and steel production by the metallurgical industries. Annually, 21 million tons of steel slag is produced in the United States. Most of the slag is landfilled, which represents a significant economic loss and a waste of valuable land space. Steel slag has great potential for the construction of highway embankments; however, its use has been limited due to its high swelling potential and alkalinity. The swelling potential of steel slags may lead to deterioration of the structural stability of highways, and high alkalinity poses an environmental challenge as it affects the leaching behavior of trace metals. This study seeks a methodology that promotes the use of steel slag in highway embankments by minimizing these two main disadvantages. Accelerated swelling tests were conducted to evaluate the swelling behavior of pure steel slag and water treatment residual (WTR) treated steel slag, where WTR is an alum-rich by-product of drinking water treatment plants. Sequential batch tests and column leach tests, as well as two different numerical analyses, UMDSurf and WiscLEACH, were carried out to check the environmental suitability of the methods. Tests were conducted to study the effect of a common borrow fill material that encapsulated the slag in the embankment and the effects of two subgrade soils on the chemical properties of slag leachate. The results indicated that an increase in WTR content in the steel slag-WTR mixtures yields a decrease in pH and most of the leached metal concentrations, except aluminum. The change in the levels of pH, after passing through encapsulation and subgrade, depends on the natural pHs of materials.

Effects of Environmentally Relevant Concentrations of Poultry Litter Associated Contaminates on the Sexual Development of Xenopus laevis

Poultry litter contains high levels of natural sex hormones, nitrogen, phosphorous, and trace amounts of heavy metals. Poultry litter runoff from poultry and farming operations in the Delmarva region can have serious impacts on frog development in the Chesapeake Bay Watershed. In this study, we investigated potential effects of litter compounds on Xenopus laevis development when exposed to environmental levels (0.35 and 0.70 g/L) of litter solution. We found that despite rapid hormone degradation, poultry litter solution still affected X. laevis development. Hormones were also more persistent in the lower poultry litter concentration, leading to even greater effects. Slowed growth and increased female gonadal abnormalities were observed after exposure to 0.35 g/L but not to 0.70 g/L of litter solution, and increased male gonadal abnormalities were observed after treatment to both litter concentrations. The developmental impacts examined in this study may have greater environmental impacts on frog reproduction and survival.