Arsenic and selenium transport from coal combustion product utilization and disposal sites.

摘要

More than 120 million tons of solid wastes are produced by coal fired electric generating stations in the U.S. each year. It is projected that U.S. coal combustion products (CCP) production will increase 1% per year to the year of 2015. To reasonably use this huge amount of valuable products instead of spending a lot of money to dispose them is a promising and significant mission for engineers.; Mine sites using CCP remain as an unsolved issue due to the concern about groundwater contact potential and rich leaching elements from CCP, like arsenic and selenium, whose leaching characteristics are already known.; What will happen to arsenic and selenium after their leaching from CCP is still not known. Starting from this point, this research focused on testing the groundwater solved arsenic and selenium adsorption and desorption by materials around CCP utilization sites. These soil and degraded rock materials were representative of the CCP surroundings in the Midwestern U.S. area and usually, they could decide the fate of trace elements leached from CCP. The tested adsorption and desorption properties of these materials on arsenic and selenium provided a comprehensive information which included different adsorption factors like pH environment, components of soil samples and the effects of the existence of other chemical species.; Adsorption and desorption isotherms were used in Random Walk based particle movement model to simulate the pollutant distribution in groundwater and soils. The self-written model can simulate pollutant movement by either retardation or distribution method. This model also overcame the lack of considering of desorption by other numerical or analytical simulation models.; The research found that the arsenic adsorption was affected by soil size and selenium adsorption was affected firstly by solution pH value and then soil size. Hysteresis did exist between the adsorption and desorption isotherms of arsenic and selenium. Distribution method pollutant transportation simulation results were different from those of retardation simulation method. Pollutant simulation result differences also existed between with and without the consideration of desorption.