Role of mineral genesis, dissolution, and sorption on arsenic fate in contaminated waste sites (2010-2015)

Problem: 

In 2001 the U.S. Environmental Protection Agency (US EPA) reduced the arsenic drinking water MCL from 50 to 10 ppb (micrograms/liter).  The US EPA has estimated that as a result of this revised arsenic rule, over 2700 metric tons (6 million pounds) of arsenic-bearing solid waste containing over 14 metric tons (31,000 pounds) of arsenic are now disposed of in municipal solid waste landfills each year. Such waste may not be stable under landfill conditions, and can release arsenic back into the environment.

Dr. Wendell Ela and his group are studying the factors that control arsenic’s association with various media. Their projects study how mineral genesis and dissolution impacts arsenic mobility. Arsenic’s association with natural and engineered mineral phases controls its aqueous concentration. Thus, the success of existing contaminated site clean-up and the prevention of new arsenic contaminated sites can be gauged by the degree to which arsenic is rendered insoluble via sequestration on or in solid phases. Interfacial processes involving arsenic (e.g., adsorption/desorption, precipitation/dissolution, and reduction/oxidation) not only control the release of arsenic into the aqueous phase, but form the basis of technologies for removing arsenic from water. Their projects focus on arsenic-bearing solid wastes under typical deposition conditions such as those occurring in landfills, mine tailings and refuse sites, mono-fill solid waste sites (e.g., power plant fly ash landfills) and contaminated sediments.

Significance: 

These studies will achieve an enhanced fundamental understanding of arsenic behavior and control at critical solid-water interfaces, and will address both prevention and remediation objectives with regard to arsenic contamination of water.

Specific Aims: 
  1. Arsenic Association with Iron Solids: Determine the mechanisms of arsenic waste retention by ferric iron solids, including the processes of solid genesis and transformation.
  2. Arsenic Association with Sulfur Solids: Evaluate the effect of sulfur system mineral speciation, transformation and dissolution on arsenic mobility under conditions where arsenic-bearing solid wastes are found or disposed.
  3. Engineered Intervention Approaches: Develop, to a proof-of-concept stage, engineering intervention strategies that utilize biological and geochemical mineral retention processes to minimize arsenic mobility from solid wastes.