UA-Led Team Studying Nitrate in Urban Areas

A team of University of Arizona-led researchers has received a federal grant totaling more than $875,000 to investigate nitrogen levels in Tucson and Phoenix water supplies.
Dec. 21, 2009
Kathleen A. Lohse
Kathleen A. Lohse
Paul Brooks
Paul Brooks
Thomas Meixner
Thomas Meixner
(Click to enlarge). The UA-led team studying nitrate levels in semi-arid and arid regions in southern Arizona will be focusing on areas in Tucson and Phoenix. (Photo courtesy of Kathleen A. Lohse)
(Click to enlarge). The UA-led team studying nitrate levels in semi-arid and arid regions in southern Arizona will be focusing on areas in Tucson and Phoenix. (Photo courtesy of Kathleen A. Lohse)

The presence of nitrates in drinking water is a pervasive concern in semi-arid and arid regions in Arizona, much of California, the Midwest region and large areas in the South despite government regulations.

Part of what is driving the problem is that water managers and urban planners in certain regions prone to nitrate contamination don't always have adequate information about sources of nitrates and ways to control or manage the chemical's presence.

Kathleen A. Lohse, an assistant professor in the UA's School of Natural Resources and the Environment, is heading up a collaborative project to offer up answers.

The team, which includes collaborators from Arizona State University and Purdue University has just received a three-year, $875,000 grant from the National Science Foundation, with UA's portion totaling more than $325,000. 

The project, "Collaborative Research: Impacts of Urbanization on Nitrogen Biogeochemistry in Xeric Ecosystems," is meant to identify sources of nitrate contamination in both surface water in urban regions of Arizona while involving citizen-scientists, graduate and undergraduate students and also decision makers.

The team will investigate the presence of nitrates in Tucson and Phoenix and also provide answers to aid water managers and urban planners. 

"Nitrate contamination is one of the most common contaminates in our Arizona aquifers and it's a large concern in a lot of areas in semi-arid regions," said Lohse, the lead principal investigator on the project.

"The reason nitrate is a common concern in aquifers, rather than ammonium, is because nitrate is relatively mobile – it moves with water and it is not held in soil as readily," she added, saying this type of movement can lead to an accumulation of nitrate.

Nitrate can be found in water and soil, and can enter ecosystems in various ways. Some of the leading causes of elevated levels of nitrates include fossil fuel combustion, fertilizer use and leaching from septic and sewage tanks.

The team's grant proposal to NSF explained: "Urbanization dramatically modifies the movement and transformations of nitrogen compounds in semi-arid ecosystems. In particular, nitrate contamination of drinking water is a growing concern in urban areas, especially in arid and semi-arid environments, where urban runoff is actively-managed to recharge groundwater and augment water supplies."

Yet the team also will evaluate different surface levels to determine ways that nitrates may modify downstream systems, while also studying which surfaces are more effective in removing the chemical.

The team noted in its proposal to the NSF that it is particularly advantageous to study deserts and semi-arid regions, as they make up nearly one-third of the surface of the Earth, are experiencing tremendous population growth and depleted water resources.

"Understanding these interactions and their feedback will be critical for developing science-based management strategies to sustain these limited resources," the team also noted.

The investigation also is particularly timely given government-level concerns about nitrate levels. 

The U.S. Environmental Protection Agency first began regulating water suppliers during the 1990s, making them responsible for curbing nitrate levels in water. More recently, the Arizona Department of Environmental Quality in a 2005 report established nitrogen management areas to control and regulate nitrate sources to aquifers, noting that elevated levels can cause health problems for infants.

The team, Lohse said, is building on two years of prior research that had been funded by the Technology Research Initiative Fund, which Arizona voters approved in 2000. 

Collaborators on the current project also will work to improve the general understanding of ways to counter and control nitrogen levels by characterizing patterns of nitrate levels in runnoff, focusing keenly on differentials depending on seasonal changes and also population density.

The team seeks to answer three critical questions:

  • How does urbanization impact the processes controlling delivery of nitrate from upland to lowland parts of the desert landscape?  
  • What are the dominant nitrate sources in arid urban watersheds?
  • How does wash substrate type modulate in-stream/wash processing of nitrate?

Answering these questions will allow the team to inform future planning and, more specifically, aid in the preservation of water. The team also will develop interactive visualization products to aid planners.

"This is one of our broader impacts – this is how we want to take our data and apply it," Lohse said.

Paul Brooks and Thomas Meixner, both of the hydrology and water resources department at the UA are co-principal investigators on the project. Collaborators include Arizona State University professor Nancy Grimm and Stevan Earl, an academic associate at ASU; and also Greg Michalski, an assistant professor in the earth and atmospheric sciences department at Purdue University.

Laboratory groups headed by Lohse, Meixner and Brooks lab groups will each collect, preserve and analyze samples.

Grimm's laboratory will collect storm runoff specimens in Phoenix through help from Earl. Grimm and Earl also will facilitate the effort with UA researchers to create modeling and products for the visualization project. Michalski and his research group will analyze atmospheric samples from soil and surface water.

Lohse said the team carries an expansive background and expertise in ecosystem ecology, water quality, integrated socio-ecological systems and other key issues related to the preservation of natural resources.

And the collaborative and interdisciplinary nature of the proposal is its strong asset. "We want our research to align and to be synergetic with those efforts in Phoenix," Lohse said.

"Our information will be specific in understanding the sources contributing to nitrate in surface waters . We can start to begin identifying areas that may be hot spots of delivery of nitrate and thereby assist water and land use managers in management of surface and groundwater systems," Lohse said.

"We're hoping to bring together stakeholders from these areas to help them to learn from our work," she added. "By design or by modification, we may be able to improve the water quality by removing the nitrate before it makes its way to areas of more focused recharge."