# Environmental Controls on Bioavailability of Arsenic and Toxic Metals

> **NIH NIH P42** · UNIVERSITY OF ARIZONA · 2022 · $285,934

## Abstract

ABSTRACT (Project 4: Jon Chorover and Mark Brusseau)
Legacy mine tailings are a primary source of arsenic and toxic metal exposure to proximal communities
throughout the semi-arid Southwest. Because they are geochemically unstable under Earth surface conditions,
tailings begin to undergo weathering transformations that lead to changes in the molecular form or “speciation”
of toxic metal(loid)s immediately upon their deposition. Weathering reactions, which are driven by meteoric
inputs of water and gases, are manifest as a “reaction front”, or a transition zone from highly-weathered to
unweathered tailings with increasing depth below the surface. The rate of the reaction front propagation and
the types of reaction products formed depend on climate and tailings mineral composition. The weathering-
induced transformations of arsenic, lead, and zinc alter their bioavailability, yielding particles that can be more
or less toxic than the primary tailings particles when ingested or inhaled. Although climate and tailings lithology
control the weathering rate, the weathering process itself occurs at the grain scale, where fluid filled pores,
sometimes in close proximity to each other, may exhibit sharp gradients in chemical composition and
concentration. The transport and reactions that occur at this pore- to core-scale must be understood
mechanistically to better predict the diagenetic alteration of tailings and contaminant bioavailability as a
function of climate, and to enhance our capacity for accurate risk assessments and effective remedial
approaches. We will evaluate the weathering processes underway at 10 federal Superfund Sites spanning a
wide range in climate, where human health risk is primarily associated with elevated arsenic concentrations in
sulfide-ore derived tailings media. Cores will be collected from each of the sites as a function of depth and
transported to the laboratory for detailed characterization of physical, mineralogical, microbial, and
geochemical composition. Depth-dependent weathering trends and reaction fronts will be determined. These
bulk reaction fronts and transformations will be correlated with alterations in arsenic, lead, and zinc molecular
speciation and bioaccessibility. A subset of the extracted cores, representing distinct pathways of metal(loid)
transformation, will be utilized in instrumented column experiments conducted in the laboratory under
controlled conditions. Columns will be subjected to detailed studies of the evolution over the course of the
experiment of pore-structure, metal(loid) speciation, and associated bioaccessibility. These experiments, which
will comprise solution samplers as a function of length along the column, will enable the collection of a reactive
transport dataset to identify the biogeochemical reactions controlling metal(loid) transformation under different
conditions. The data generated will be used to implement a reactive transport and fate model of tailings
diagenesis that will ...

## Key facts

- **NIH application ID:** 10337263
- **Project number:** 5P42ES004940-33
- **Recipient organization:** UNIVERSITY OF ARIZONA
- **Principal Investigator:** Jon D Chorover
- **Activity code:** P42 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $285,934
- **Award type:** 5
- **Project period:** 1997-04-01 → 2025-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10337263

## Citation

> US National Institutes of Health, RePORTER application 10337263, Environmental Controls on Bioavailability of Arsenic and Toxic Metals (5P42ES004940-33). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10337263. Licensed CC0.

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