Abstract
Addition of nutrients, such as nitrogen, can degrade water quality in lakes, rivers, and estuaries. To predict the fate of nutrient inputs, an understanding of the biogeochemical cycling of nutrients is needed. We develop and employ a novel, parsimonious, process-based model of nitrogen concentrations and stable isotopes that quantifies the competing processes of volatilization, biological assimilation, nitrification, and denitrification in nutrient-impacted rivers. Calibration of the model to nitrogen discharges from two wastewater treatment plants in the Grand River, Ontario, Canada, show that ammonia volatilization was negligible relative to biological assimilation, nitrification, and denitrification within 5 km of the discharge points.
Highlights
Nitrogen (N) is essential for life but can be present in the environment in excess of growth requirements due to human activities
NH3 is toxic to aquatic life.(Canadian Council of Ministers of the Environment 2010) elevated concentrations of NO3- degrade water quality by harming aquatic life (Canadian Council of Ministers of the Environment 2012) and above drinking water limits can lead to adverse health effects in people (Iwanyshyn et al 2008)
Ecosystems the size of the Grand River are not amenable to experimental isotope tracer additions but afford us the opportunity to assess many of the processes resultant from the discharge of nitrogen-rich waste-water treatment plants (WWTPs) effluent
Summary
Nitrogen (N) is essential for life but can be present in the environment in excess of growth requirements due to human activities. Nitrate (NO3-) and total ammonia nitrogen (TAN; where TAN includes both ammonia (NH3) and ammonium (NH4+)) are the two inorganic N forms that determine the critical loads beyond which aquatic ecosystems experience eutrophication or acidification (Posch et al2001, Schindler et al 2006). The fate of these inorganic N species is a key determinant in the health of ecosystems and the services they provide to humans. Understanding the environmental fate of TAN and NO3- discharged to surface waters is important for managing of humandisturbed aquatic ecosystems
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