Assessing nonpoint-source uranium pollution in an irrigated stream-aquifer system | JoVE Visualize

Assessing nonpoint-source uranium pollution in an irrigated stream-aquifer system

¹Dept. of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80523, USA; Dept. of Civil and Environmental Engineering, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia.

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Summary

Irrigation mobilizes uranium (U) in arid regions, posing health risks. A numerical model shows U levels exceed EPA standards in 44% of Colorado

Area of Science:

Background:

Uranium (U) mobilization in arid/semi-arid environments by irrigation and fertilization presents significant environmental and health risks.
Elevated U, often co-occurring with selenium (Se) and nitrate (NO3), requires diligent monitoring and management strategies.
Understanding U transport in stream-aquifer systems is crucial for assessing pollution dynamics.

Purpose of the Study:

To develop and apply a numerical model for assessing uranium pollution in an irrigated stream-aquifer system.
To quantify uranium levels and identify contributing factors in Colorado's Lower Arkansas River Valley (LARV).
To establish a baseline for evaluating future best management practices (BMPs) for uranium mitigation.

Main Methods:

Developed a distributed-parameter numerical model coupling MODFLOW for groundwater/stream flow and RT3D-OTIS for reactive uranium transport.
Applied the model to a 552 km2 region in Colorado's LARV over a 14-year period.
Calibrated the model using PESTPP-iES iterative ensemble smoother (iES) software against observed uranium concentrations.

Main Results:

The model revealed substantial and variable uranium levels across the LARV, identifying potential hotspots.
Uranium concentrations exceeded the US EPA chronic standard (30 μg/L) in groundwater across 44% of the region and along the river by an average factor of 2.9.
Simulated average uranium concentrations (aquifer: 124 μg/L, river: 60 μg/L) closely matched measured values (aquifer: 112 μg/L, river: 62 μg/L).

Conclusions:

Geological composition, irrigation practices, and riparian landscapes are key factors influencing uranium distribution.
The developed model provides a valuable tool for assessing uranium pollution in irrigated regions.
Findings offer a baseline for evaluating BMPs and a transferable methodology for other affected areas.