Date of Award

Spring 12-6-2017

Document Type


Degree Name

Master of Science (MS)

First Advisor

Diane M. McKnight

Second Advisor

Robert L. Runkel

Third Advisor

Roseanna Neupauer


Quantifying and understanding the transport of rare earth elements (REEs) in relation to heavy metals within acidic alpine rivers is relatively understudied. However, employing solute transport models, specifically One-Dimensional Transport with Inflow and Storage (OTIS) can provide insight on the reactivity and transport of REEs. The Snake River is located along the Colorado Mineral Belt in Summit County, Colorado and drains into metropolitan Denver’s drinking water source – Dillon Reservoir. The Snake River is of particular interest due to its hydrological and geochemical similarity to other alpine streams impacted by acid mine drainage throughout Colorado.

In previous studies, most REEs were found to behave conservatively at lower pH. In general, the higher concentrations of REEs were found at the headwaters containing lower pH levels with decreasing concentrations as pH increased from 4.13 to 8.52. Using size-partitioning experiments, the composition of colloidal and dissolved metal oxides were obtained to determine the dominant state of Fe and Al, and subsequent interaction with REEs. Fractionation experiments showed that REEs are proportionally more abundant in their dissolved form at lower pH < 5. The distribution between colloidal and dissolved phases increased as pH increased.

The influence of pH on metal complexation, precipitation/dissolution and oxidation/reduction was investigated using simulations, and parameter estimation to analyze data collected from synoptic sampling and tracer injection experiments. Modeling the transport of these REEs of industrial importance will significantly resolve issues concerning acid mine drainage remediation and future mineral extraction.