Nitrate Contamination in the Albuquerque Basin

Science Center Objects

Globally, nitrate is the most ubiquitous groundwater contaminate including within the Albuquerque Basin in New Mexico. Ingesting high concentrations of nitrate (> 10 mg/L as N) in drinking water can lead to an increased risk of cancer and in infants, methemoglobinemia. Historical groundwater sampling in Albuquerque and Kirtland Air Force Base have found high (> 10 mg/L as N) and sometime extreme (> 50 mg/L as N) nitrate concentrations in groundwater. There are many potential sources of nitrate in this region including fertilizers, septic leach fields, sewer lines, historical acid waste outfall from Sandia National Laboratory, landfills, and potentially—naturally occurring nitrate built up in desert soils.

This study seeks to use extensive geochemical analyses of groundwater and surface water to differentiate between various sources of nitrate contamination on Kirtland Air Force Base and parts of the Albuquerque Basin. Our goal is to create a template for future studies to follow when investigating complex—likely mixed—sources of nitrate in groundwater and surface water.

Kirtland AFB, USGS - NMWSC

Driving through a less populated part of Kirtland Air Force Base on our way to sample more wells.

The U.S. Geological Survey collected 54 groundwater samples from wells and six samples from ephemeral streams from within and from outside of areas of known nitrate contamination. To fingerprint the sources of nitrate pollution, samples were analyzed for major ions, trace metals, nutrients, dissolved gases, δ15N and δ18O in NO3, δ15N within N2 gas, and, δ2H and δ18O in H2O. Furthermore, most sites were sampled for artificial sweeteners and numerous contaminants of emerging concern including pharmaceutical drugs, caffeine, and wastewater indicators. This study will also investigate the age distribution of groundwater using 3He/4He, δ13C, 14C, 3H, and the approximate age of anthropogenic NO3 contamination using pharmaceutical drugs and artificial sweeteners with known patent and U.S. Food and Drug Administration approval dates. This broad suite of analytes will be used to differentiate between naturally occurring and multiple anthropogenic NO3 sources, and to potentially determine the approximate date of NO3 contamination.

 

Sediment core collection, USGS, NMWSC

In addition to groundwater sampling, we collected sediment cores to look for nitrate and chloride built up in the desert soils. This naturally occurring nitrate could serve as an additional source of nitrate if land use changes flushed nitrate from the soil to the aquifer.