Mercury has been an element of great industrial importance since early times.This wide utilization of the element has led to pervasive mercury contamination in theglobal environment. Due to mercury's high toxicity, this is a matter of great concern. Anumber of methods, includ ing phytoremediation, filtration, and precipitation/chelation,have been investigated to remove mercury from the environment. Unfortunately, thesemethods are not entirely satisfactory for the in-situ remediation of mercury from aqueousenvironments.The hypothesis of this dissertation is that this can best be accomplished by theaddition of a large and flexible sulfur-based chelate, that will bind mercury in atetracoordinate and presumably tetrahedral environment, to mercury-contaminatedwaters. Although this proved difficult due to the tendency of these ligands to decomposeinto smaller, sulfur-containing rings, the synthesis and characterization of such a chelatewas achieved. Several potential mercury-binding ligands were eventually synthesizedsignificant amounts of mercury (91-100%) from the contaminated solutions, in one caselowering the mercury levels in the water to below the CVAF detection limits. Theresulting solids lost little (andlt;15 ppb) of their mercury during leaching studies.This work demonstrates the use of tetradentate chelates in precipating Hg2+ fromwater to produce stable mercury- ligand precipitates. A calculation for the quantification ofthe geometry of a four-coordinate compound was also developed and applied to aluminum,gallium, and mercury compounds. This calculation could also be applied to the mercurycompounds described in this thesis once X-ray structures become available

Mercury and arsenic are widespread contaminants in aqueous environments throughout the world. The elements arise from multiple sources including mercury from coal-fired power plants and wells placed in natural geological deposits of arseniccontaining minerals. Both elements have significant negative health impacts on humans as they are cumulative toxins that bind to the sulfhydryl groups in proteins, disrupting many biological functions. There are currently no effective, economical techniques for removing either mercury or arsenic from aqueous sources. This thesis will demonstrate a superior removal method for both elements by formation of covalent bonds with the sulfur atoms in N,N’-Bis(2-mercaptoethyl)isophthalamide (commonly called “B9”). That B9 can precipitate both elements from water is unusual since aqueous mercury exists primarily as a metal(II) dication while aqueous arsenic exists as As(III) and As(V) oxyanions.

A probabilistic risk assessment model using GOLDSIM software was developed to evaluate the uncertainty of selected hydrological and soil parameters on mercury releases from a mercury containment system, which will be constructed within the Environmental Management Waste Management Facility in the Bear Creek Valley at the Oak Ridge Reservation in Tennessee. The main objective was to determine the concentrations and risk of exceeding the drinking water standard of mercury in a selected receptor well. A series of simulations were then conducted for various design periods, with emphasis on 10,000 years to determine those concentrations and risks. Experimental data for selected parameters such as dry bulk density, partition coefficient, and porosity and infiltration rate were represented by Probability Density Functions in support of Monte Carlo analyses. A sensitivity analysis showed that concentrations and risk are, for instance, most sensitive to porosity in the unsaturated zone. The simulations suggest that all herein estimates of concentrations and risks of mercury in drinking water should be well below established limits.

An integrated flow and transport model using MIKE SHE/MIKE 11 software was developed to predict the flow and transport of mercury, Hg(II), under varying environmental conditions. The model analyzed the impact of remediation scenarios within the East Fork Poplar Creek watershed of the Oak Ridge Reservation with respect to downstream concentration of mercury. The numerical simulations included the entire hydrological cycle: flow in rivers, overland flow, groundwater flow in the saturated and unsaturated zones, and evapotranspiration and precipitation time series. Stochastic parameters and hydrologic conditions over a five year period of historical hydrological data were used to analyze the hydrological cycle and to determine the prevailing mercury transport mechanism within the watershed. Simulations of remediation scenarios revealed that reduction of the highly contaminated point sources, rather than general remediation of the contaminant plume, has a more direct impact on downstream mercury concentrations.