Investigating the Sources, Spatial Variation and Movement of Nitrate Contamination in the Casper Aquifer, Laramie, WY
- Project Number: 69
- PIs: YKen Sims, UW Dept. of Geology and Geophysics; David Williams, UW Dept. of Botany; Morteza Dejam, UW Dept. of Energy and Petroleum Engineering
- Period: July 2026 - June 2028
Abstract:
Nitrate is an increasingly problematic contaminant threatening drinking water sources
in Wyoming and across the United States. Nitrate contaminants in surface and groundwater
are responsible for eutrophication, a cause for drinking water resources to become
unusable, and medical conditions like methemoglobinemia (“blue baby syndrome”). Identifying
the source and movement of nitrate in groundwater sources used for drinking water
is essential for maintaining high quality water resources.
In this proposal, researchers at the University of Wyoming will collaborate with the
City of Laramie and Albany County to develop a methodology for investigating nitrate
contamination in their shared drinking water resource. We propose measuring the stable
isotopes of nitrate and water, in addition to strontium and radium, in samples of
groundwater, local snow and rain precipitation, agricultural runoff, septic system
effluent, and fertilizers, all of which are potential sources of nitrate to groundwater.
These isotopic measurements will provide the researchers with a powerful tool for
identifying the source and quantifying the impact of nitrate on the Casper Aquifer
groundwater system.
Our comprehensive study will have five main objectives: (i) Characterize the isotopic
composition of nitrates from both natural and anthropogenic sources, including atmospheric
deposition, geological sources, livestock areas, septic system effluent, and fertilizers.
(ii) Determine the spatial and temporal variance of nitrate (NO3-) isotopes in the
groundwater of the Casper Aquifer over two years with monthly measurements conducted
from July 2026 through June 2028 at designated wells. (iii) Determine the characteristics
of aquifer source rocks and water flow paths through measurements of 87Sr/86Sr ratios, as well as cation and anion analyses. (iv) Calculate groundwater ages and
the timescales of water-rock interaction using measurements of (228Ra/226Ra). (v) Interpret the nitrate signals in the context of aquifer mixing and flow pathways
by integrating the information collected from water isotope analyses, 87Sr/86Sr ratios, (228Ra/226Ra) measurements, and cation and anion data to gain a comprehensive understanding
of nitrate sources and flow dynamics in the Caper Aquifer.
This research will support mitigation efforts and the development of policies aimed
at protecting water quality. Although this proposal focuses on the Casper Aquifer
system, the methodology we have developed can be applied throughout the state, where
nitrate contamination may also pose a problem.
