Contribution of nitrogen sources to streams in mixed-use catchments varies seasonally in a cold temperate region

Kristin J Painter; Robert B Brua; Geoff Koehler; John Spoelstra; Adam G Yates

doi:10.1016/j.scitotenv.2020.142824

Contribution of nitrogen sources to streams in mixed-use catchments varies seasonally in a cold temperate region

Sci Total Environ. 2021 Apr 10:764:142824. doi: 10.1016/j.scitotenv.2020.142824. Epub 2020 Oct 7.

Authors

Kristin J Painter¹, Robert B Brua², Geoff Koehler³, John Spoelstra⁴, Adam G Yates⁵

Affiliations

¹ The University of Western Ontario and Canadian Rivers Institute, Department of Geography and Environment, 1151 Richmond Street, London, Ontario N6A 5C2, Canada. Electronic address: kpainte3@uwo.ca.
² Environment and Climate Change Canada, National Hydrology Research Centre, 11 Innovation Boulevard, Saskatoon, Saskatchewan S7N 3H5, Canada.
³ Environment and Climate Change Canada, National Hydrology Research Centre, 11 Innovation Boulevard, Saskatoon, Saskatchewan S7N 3H5, Canada; NHRC Stable Isotope Laboratory, 11 Innovation Boulevard, Saskatoon, Saskatchewan S7N 3H5, Canada.
⁴ Environment and Climate Change Canada, Canada Centre for Inland Waters, 867 Lakeshore Road, Burlington, Ontario L7S 1A1, Canada; Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada.
⁵ The University of Western Ontario and Canadian Rivers Institute, Department of Geography and Environment, 1151 Richmond Street, London, Ontario N6A 5C2, Canada.

PMID: 33757258
DOI: 10.1016/j.scitotenv.2020.142824

Abstract

Intensive agriculture and growing human populations are important nitrogen (N) sources thought to be associated with eutrophication. However, the contribution and seasonality of N delivery to streams from human activities is poorly understood and knowledge of the role of stream communities in the assimilation of N from human activities is limited. We used N and oxygen stable isotope ratios of dissolved inorganic N (DIN) and concentrations of artificial sweeteners to identify the relative contribution of key sources of anthropogenic N (i.e., fertilizers, human, and livestock waste) to tributaries of the Red River Valley (RRV), Manitoba, Canada. Water and algae were sampled in 14 RRV tributaries during snowmelt, spring, summer, and autumn; and water was sampled at three locations in the Red River in spring, summer, and autumn. δ¹⁵N values of DIN in tributary water differed seasonally and were greatest during snowmelt. Incorporation of ammonium δ¹⁵N provided evidence for the importance of manure N to tributaries during snowmelt. Fertilizer and municipal lagoons served as principal sources of N to streams in spring and summer. Human and livestock waste sources of N were the dominant contributor to algae at greater than 90% of sites and algae δ¹⁵N was greatest at sites downstream of municipal lagoons. We also showed that the tributaries contribute human and livestock waste N to the Red River, though much of the nitrate in the river originates outside of Manitoba. Overall, our study determined that the anthropogenic sources of N to RRV streams vary seasonally, likely due to regional hydrologic conditions. Our study also showed the potential of artificial sweeteners and ammonium δ¹⁵N as tools for identifying N sources to rivers. Moreover, we demonstrate the need for the management of N sources and the protection of stream function to control downstream transfer of N from landscapes to waterbodies.

Keywords: Artificial sweeteners; Land use; Nitrogen; Stable isotopes; Stream ecology.

MeSH terms

Canada
Environmental Monitoring
Humans
Manitoba
Nitrates / analysis
Nitrogen Isotopes / analysis
Nitrogen* / analysis
Water Pollutants, Chemical* / analysis

Substances

Nitrates
Nitrogen Isotopes
Water Pollutants, Chemical
Nitrogen