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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Water Quality and Ecology Research » Research » Publications at this Location » Publication #382355

Research Project: Strategic Investigations to Improve Water Quality and Ecosystem Sustainability in Agricultural Landscapes

Location: Water Quality and Ecology Research

Title: Temperature and carbon availability interact to enhance nitrous oxide production via denitrification in alluvial plain river sediments

item SPEIR, SHANNON - University Of Notre Dame
item TANK, JENNIFER - University Of Notre Dame
item Taylor, Jason
item GROSE, AMELIA - University Of Notre Dame

Submitted to: Limnology and Oceanography Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2023
Publication Date: 8/7/2023
Citation: Speir, S.L., Tank, J.L., Taylor, J.M., Grose, A.L. 2023. Increased temperature and carbon availability enhances nitrous oxide production due to incomplete denitrification in river sediments. Limnology and Oceanography Letters.

Interpretive Summary: Nitrous oxide is a greenhouse gas that contributes to global climate change. Streams and rivers are important natural sources of nitrous oxide to the atmosphere; however, it remains unclear how varying environmental conditions might alter nitrous oxide production in streams and rivers in the future. Our study provides evidence that increased carbon availability combined with warming temperatures may enhance nitrous oxide production from streams with high nitrogen (>1 mg L-1 nitrate). Our results suggest nitrous oxide production from flowing waters may become more important in the context of climate-relevant greenhouse gas emissions, particularly in systems with high nitrogen and dissolved carbon availability, both common characteristics of agricultural watersheds. This finding highlights the need for best management practices that reduce nitrogen inputs to streams.

Technical Abstract: Streams and rivers are key sources of nitrous oxide (N2O), which is a powerful greenhouse gas. Incomplete denitrification results in N2O production, which is controlled by nitrate (NO3--N) and organic carbon (C) availability, as well as water temperature. Yet, few studies have experimentally isolated these drivers, especially in flowing waters. We used sediment core incubations conducted at 15 °C and 25 °C, and membrane inlet mass spectrometry (MIMS) to understand how NO3--N, C, and temperature influence N2O production rates and yields (as %) from sediment denitrification. In general, conditions that enhanced denitrification rates also increased N2O production. At both temperatures, we observed higher N2O production with added C, and rates remained high across the NO3--N gradient. Contrary to previous studies, C additions increased N2O yields. Thus, as global temperatures warm and rivers “brown,” N2O production from riverine sediments will likely increase.