Dissertation/Thesis Abstract

Spatial and Temporal Study of Arsenic and Lead in Soil and Sediment Samples Collected from the San Juan River on the Navajo Nation after the Gold King Mine Spill
by Settimo, Adam K., M.S., Northern Arizona University, 2017, 136; 10623146
Abstract (Summary)

On August 5, 2015, contracted workers for the Environmental Protection Agency (EPA) near Silverton, CO. at the Gold King Mine, while performing maintenance to the tailing pond dam with heavy equipment, knocked the dam wall loose releasing 3 million gallons of contaminated wastewater into Cement Creek, a tributary of the Animas River which is a tributary of the San Juan River. Following the release, a large yellow/orange plume was observed moving downriver through several agricultural communities of the San Juan, on the Navajo Reservation. The goal of this work is to quantify lead, arsenic, and uranium being deposited in the river and canal sediment over time, as well as the agricultural topsoil.

Sample collection took place 3, 6, and 9 months after the spill. Sediment samples were collected in cleaned two foot PVC pipes for the core samples and ultraclean whirl-Pak bags for the agricultural topsoil. The top one inch of the core was taken for analysis as well as the bottom 1 inch for comparison. All samples were processed, acid digested either partially or completely by EPA methods 3051 or 3052, and analyzed for trace metal composition by ICP-MS (Thermo Fisher XSeries 2 ICP-MS). This work has focused on the analysis of samples in the communities of northern New Mexico in Shiprock and Upper Fruitland on the Navajo Nation. The larger dataset was digested by partial digest (EPA 3051) with a smaller dataset being completed by a total hydrofluoric digest (EPA 3052).

The overall goal with this research was to take samples and produce data to inform the affected communities of the possible contamination by the elements of interest in this study. Without an idea of the background of the river and the area, that information isn’t as helpful for the communities; therefore, the secondary goal was to gather some background information that would provide some context. The end result of this work was that within the time that sampling was conducted the concentrations for arsenic and lead were far below maximum levels set by the EPA and uranium was below that of the earth crust background but slightly above what the background samples we collected and analyzed reported. Some of the results showed increasing trends for arsenic and lead in the time sampled and further sampling to gather more data should conducted regarding this.

Background samples were pulled from upstream of the convergence of the two rivers along the San Juan. These samples were used to fulfill the second goal and to give context to the rest of the study. The data collected from them should be used to give context to future monitoring or studies conducted.

Indexing (document details)
Advisor: Ingram, Jani
Commitee: Lee, Michael V., Mihay, Martin
School: Northern Arizona University
Department: Chemistry and Biochemistry
School Location: United States -- Arizona
Source: MAI 57/02M(E), Masters Abstracts International
Subjects: Chemistry, Analytical chemistry, Environmental Justice, Native American studies, Environmental science
Keywords: Analytical chemistry, Chemistry, Environmental analytical chemistry, Gold King Mine Spill, Navajo Nation, New Mexico, San Juan River, Utah
Publication Number: 10623146
ISBN: 9780355567892
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