Sequential Extraction Insights into the Mobility of Arsenic (As), Lead (Pb), Chromium (Cr), and Copper (Cu) in Coal Fly Ash

Garcia, Estefania; Harrell, August; Tribby, Emily; Lim, Marie; Wen, Yinghao; Xu, Hang; Tang, Yuanzhi

doi:10.3390/min16080800

Open AccessArticle

Sequential Extraction Insights into the Mobility of Arsenic (As), Lead (Pb), Chromium (Cr), and Copper (Cu) in Coal Fly Ash

by

Estefania Garcia

^*

,

August Harrell

,

Emily Tribby

,

Marie Lim

,

Yinghao Wen

,

Hang Xu

and

Yuanzhi Tang

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332, USA

^*

Author to whom correspondence should be addressed.

Minerals 2026, 16(8), 800; https://doi.org/10.3390/min16080800

Submission received: 26 June 2026 / Revised: 25 July 2026 / Accepted: 28 July 2026 / Published: 31 July 2026

(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)

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Abstract

Coal combustion generates coal fly ash (CFA) as a solid byproduct, with nearly 16 million tons produced in 2023 alone. CFAs contain harmful trace metals, including arsenic (As), lead (Pb), chromium (Cr), and copper (Cu), whose mobility and environmental impact depend on their chemical speciation. This study examined a set of 16 representative CFAs across the U.S. with trace element speciation and mobility operationally defined by chemical sequential extraction. A principal component analysis (PCA) was performed on CFA bulk properties, and trace element partitioning data were projected onto the PCA space to explore associations. The residual and reducible fractions are the primary hosts for As, Pb, Cr, and Cu, accounting for 8%–95% and 2%–82% of total concentrations, respectively. Subbituminous CFAs were associated with a higher CaO content, whereas bituminous CFAs contained a higher Fe₂O₃ content. Interestingly, subbituminous CFAs were primarily associated with the more labile fractions (i.e., exchangeable, acid-soluble, reducible, and oxidizable). This suggests that Cu, Cr, and Pb may be more mobile in subbituminous CFAs, which are characterized by higher CaO and lower Fe₂O₃ contents in this study. A partial least squares discriminant analysis (PLS-DA) revealed that CaO and Fe₂O₃ content are statistically significant in determining the mobility of Cr.

Keywords: coal combustion residuals; trace metals; sequential extraction; speciation; principal component analysis; and partial least squares discriminant analysis

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MDPI and ACS Style

Garcia, E.; Harrell, A.; Tribby, E.; Lim, M.; Wen, Y.; Xu, H.; Tang, Y. Sequential Extraction Insights into the Mobility of Arsenic (As), Lead (Pb), Chromium (Cr), and Copper (Cu) in Coal Fly Ash. Minerals 2026, 16, 800. https://doi.org/10.3390/min16080800

AMA Style

Garcia E, Harrell A, Tribby E, Lim M, Wen Y, Xu H, Tang Y. Sequential Extraction Insights into the Mobility of Arsenic (As), Lead (Pb), Chromium (Cr), and Copper (Cu) in Coal Fly Ash. Minerals. 2026; 16(8):800. https://doi.org/10.3390/min16080800

Chicago/Turabian Style

Garcia, Estefania, August Harrell, Emily Tribby, Marie Lim, Yinghao Wen, Hang Xu, and Yuanzhi Tang. 2026. "Sequential Extraction Insights into the Mobility of Arsenic (As), Lead (Pb), Chromium (Cr), and Copper (Cu) in Coal Fly Ash" Minerals 16, no. 8: 800. https://doi.org/10.3390/min16080800

APA Style

Garcia, E., Harrell, A., Tribby, E., Lim, M., Wen, Y., Xu, H., & Tang, Y. (2026). Sequential Extraction Insights into the Mobility of Arsenic (As), Lead (Pb), Chromium (Cr), and Copper (Cu) in Coal Fly Ash. Minerals, 16(8), 800. https://doi.org/10.3390/min16080800

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Sequential Extraction Insights into the Mobility of Arsenic (As), Lead (Pb), Chromium (Cr), and Copper (Cu) in Coal Fly Ash

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