State Water Resources Research Institute Program

Project ID: 2008WI191B
Title: Occurrence and Generation of Nitrite in Ground and Surface Waters in an Agricultural Watershed
Project Type: Research
Start Date: 3/01/2008
End Date: 2/28/2009
Congressional District: 2
Focus Categories: Nitrate Contamination, Agriculture, Hydrogeochemistry
Keywords: nitrite, drinking water, nitrogen biogeochemistry, groundwater-surface water interactions
Principal Investigator: Stanley, Emily H. (University of Wisconsin-Madison)
Federal Funds: $ 33,901
Non-Federal Matching Funds: $ 29,024
Abstract: The overarching goal of the proposed research is to better understand the extent of nitrite (NO2-) occurrence in groundwater, and the conditions that promote the accumulation of this potentially toxic form of nitrogen in both groundwater and surface waters of agriculturally-dominated catchments. This work is motivated by the observation of relatively high concentrations of NO2- in several Wisconsin streams and similar reports of elevated NO2- in N-enriched groundwater and interstitial riverine environments elsewhere. The potential occurrence of NO2- in groundwater could pose a health risk to the large percent of the State's population that relies on this drinking water source. Further, discharge of nitrogen-rich groundwater leading to NO2- accumulation in streams creates similar stresses on sensitive aquatic communities, even at low concentrations. Thus, this proposal will provide valuable information on the extent of this chemical and the environmental circumstances in which it can occur--critical first steps for dealing with issues of nitrite contamination.

The proposed study, to be undertaken by the PI (E.H. Stanley), a graduate student and an undergraduate, will (1) examine temporal patterns of groundwater and surface water chemistry and NO2- occurrence along four upland-to-stream transects, (2) measure NO2- generation in a series of controlled laboratory experiments to quantify rates and likely pathways of NO2- formation; and (3) conduct a survey of groundwater chemistry to determine if NO2- is present in groundwater at diverse locations in Wisconsin. This mixture of monitoring, surveys, and field and lab experiments should substantially expand our understanding of the processes and conditions leading to NO2- accumulation in water, and provide insights into new and poorly understood pathways of nitrogen cycling. In particular, we will determine if disappearance of groundwater NO3- is caused by denitrification or conversion to ammonium. This latter process, known as dissimilatory nitrate reduction to ammonium (DNRA) may be responsible for substantial NO3- losses in wetlands, but rather than remove nitrogen from water, it simply converts it to another form. If DNRA is an important process in groundwater, then our current understanding of the effectiveness of wetlands and riparian buffers in removing nitrogen may be incorrect, and nitrogen management strategies would need to be adjusted accordingly.

This work is expected to be of broad interest to researchers interested in nitrogen biogeochemistry, particularly with respect to groundwater-surface water interactions, as well as to management agencies responsible for protecting in-stream habitats and communities and protecting vulnerable groundwater drinking water sources in agricultural landscapes.

Progress/Completion Report, 2008, PDF
Progress/Completion Report, 2011, PDF

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