Author(s): Alessandra Marzadri; Daniele Tonina; Alberto Bellin
Linked Author(s): Daniele Tonina
Keywords: No keywords
Abstract: Streams and rivers represent the natural connectivity between terrestrial and marine environments through which solutes, nutrients, contaminants, and pathogens, move along both their surface and subsurface environments. In the recent decades, the importance of the subsurface environments, and particularly the benthic and hyporheic zones in contributing and controlling both water quantity and quality, has received more and more attention [see Boano et al., and reference therein]. The benthic zone is the ecological region of the streambed located at the interface between water and sediment, where both aquatic fauna and flora can be found; while the hyporheic zone is the band of streambed material mainly saturated with stream water [see Tonina and reference therein]. Field evidence confirm that within these surface and subsurface aquatic environments, the biogeochemical processes that control N cycle, contribute to the production of nitrous oxide, N2O, one of the most important greenhouse gas; which additionally is also responsible for stratospheric ozone destruction. According to the IPCC report CO2, CH4 and N2O account for the 94% of the global radiative forcing; with N2O that in terms of global warming potential (GWP) for the 100-year time horizon, is 300 times more potent (per molecule) than CO2. Therefore, the role of riverine environments cannot be neglected in the perspective of characterizing their contribution on climate change. However, most of the available studies do not identify the linkage between hydromorphological and biochemical characteristics of riverine environments on N2O emissions and very few provide predictive models at the regional and larger scales. Here, we focused our attention on the contribution of riverine environments in controlling the fate of the dissolved inorganic nitrogen species (DIN) that enter within surface water in the form of ammonium (NH4) and nitrate (NO3) and are converted, mainly through microbially mediated processes of nitrification-denitrification, to N2O and dinitrogen (N2). We analyzed the production of N2O from riverine environments at different spatial scales (i. e., from local reach scale to global scale). Firstly, we characterized the local reach scale behavior under different streambed morphologies considering also possible effects of streambed heterogeneity and groundwater intrusion. At this scale, the stream boundaries are extended beyond the surface water in order to include the interaction with benthic and hyporheic zones, but then in order to represent N2O emissions at the network scale we need to identify a framework able to account for local processes and at the same time based only on reach scale quantities.
Year: 2022