Ranking Coal Ash Materials for Their Potential to Leach Arsenic and Selenium: Relative Importance of Ash Chemistry and Site Biogeochemistry

Grace E. Schwartz, James C. Hower, Allison L. Phillips, Nelson Rivera, Avner Vengosh, Heileen Hsu-Kim

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


The chemical composition of coal ash is highly heterogeneous and dependent on the origin of the source coal, combustion parameters, and type and configuration of air pollution control devices. This heterogeneity results in uncertainty in the evaluation of leaching potential of contaminants from coal ash. The goal of this work was to identify whether a single leaching protocol could roughly group high-leaching potential coal ash from low-leaching potential coal ash, with respect to arsenic (As) and selenium (Se). We used four different leaching tests, including the Toxicity Characteristic Leaching Protocol (TCLP), natural pH, aerobic sediment microcosms, and anaerobic sediment microcosms on 10 different coal ash materials, including fly ash, lime-treated ash, and flue gas desulfurization materials. Leaching tests showed promise in categorizing high and low-leaching potential ash materials, indicating that a single point test could act as a first screening measure to identify high-risk ash materials. However, the amount of contaminant leached varied widely across tests, reflecting the importance of ambient conditions (pH, redox state) on leaching. These results demonstrate that on-site geochemical conditions play a critical role in As and Se mobilization from coal ash, underscoring the need to develop a situation-based risk assessment framework for contamination by coal ash pollutants.

Original languageEnglish
Pages (from-to)728-738
Number of pages11
JournalEnvironmental Engineering Science
Issue number7
StatePublished - Jul 2018

Bibliographical note

Funding Information:
We thank Kaitlyn Porter for her assistance with ICP-MS measurements. This work was supported by the National Science Foundation (CBET-1235661 and CBET-1510965). G.E.S. was partly supported by a doctoral scholarship from the Environmental Research and Education Foundation. The effort of A.L.P. was supported by Duke’s Program in Environmental Health (ITEHP) Training Grant from the National Institute of Environmental Health Sciences (T32-ES021432).

Publisher Copyright:
© 2018 Grace E. Schwartz et al.


  • arsenic
  • biogeochemistry
  • coal ash
  • disposal
  • leaching potential
  • selenium

ASJC Scopus subject areas

  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution


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