Grasslands of the Konza Prairie near Manhattan may soon reveal more about the way groundwater is contaminated by nitrogen or the way nature keeps groundwater supplies clear.
This spring, researchers from Kansas University, the Kansas Geological Survey and Kansas State University began a three-year study of groundwater and nitrogen at the Konza Prairie. The work, funded by the National Science Foundation, is being done by Gwendolyn Lee Macpherson, KU geology department; Marios A. Sophocleous, Kansas Geological Survey; and, from Kansas State, M. Katherine Banks and James Koelliker, Department of Civil Engineering; Walter K. Dodds, Division of Biology; and Charles W. Rice and A. Paul Schwab, Department of Agronomy.
The Konza Prairie Research Natural Area covers 8,500 acres. It is owned by the Nature Conservancy and operated by Kansas State's Division of Biology. Konza is the largest parcel of tall-grass prairie in North America set aside for ecological research.
Researchers are interested in the transition area between the soil's unsaturated zone and the groundwater table. In particular, they want to learn how nitrogen is changed in this transition zone. According to Sophocleous, scientists have previously focused on water flow and chemical processes near the soil's surface.
"Bacteria found in the transition zone interact with and may transform nitrogen compounds before they enter the groundwater," Sophocleous said. This process affects what eventually becomes the drinking water for about 90 percent of rural Kansans.
Scientists believe that subsurface nitrogen contamination may be linked to agriculture and is probably related to fertilizers. High levels of nitrogen or nitrate in groundwater can cause blue-baby syndrome in infants who drink the contaminated water.
Because some of the land at Konza has been left in pasture and some has been farmed, it provides the chance to compare water quality from a native ecosystem with an agricultural ecosystem. In April, the Survey drilled two sets of wells on the Konza Prairie, one in an area where land was cultivated and another in pristine prairie.
The scientists took water and soil samples from the drilled holes at both sites until reaching bedrock about 30 feet. They analyzed the samples in labs at KSU's agronomy department and KU's geology department. They will take water samples from various depths in the wells every two weeks during the project, analyzing the samples for dissolved nitrogen compounds. They also will count and study bacteria populations to try to understand their impact on nitrogen content.
Sophocleous said scientists believe a "hot spot" may form where the soil's unsaturated zone and groundwater table meet. In a "hot spot," bacteria concentrate because of the high oxygen and food availability in the form of nitrogen and carbon.
"We want to learn how important the bacteria in the soil are in transforming nitrogen compounds," Sophocleous said. The scientists want to know whether bacteria eliminate nitrogen in a natural system the same way they do in an agricultural system. "If nitrogen compounds aren't transformed by these 'bugs' before reaching the groundwater, contamination is likely."
The scientists also will study nitrogen transformation in the laboratory by adding nitrogen compounds to unsaturated and saturated soils and measuring the bacteria's response.
By the end of the project, the researchers hope to be better able to predict and control problems caused by agricultural chemicals in soils and aquifers.