Effects of Revetments on Nitrification and Denitrification Potentials in the Urban River–Riparian Interface

Abstract

River–riparian interfaces (RRIs) are not only an important type of urban land but also a key area for mitigating and controlling urban river nitrogen pollution. However, the material and energy exchange dynamics in the natural interaction between rivers and RRIs undergo changes due to the introduction of recently constructed revetments, affecting the nitrogen cycling of the RRI, and the impact of revetments on the control and mitigation of river nitrogen pollution in an RRI is unknown. Therefore, RRI soil properties, nitrification potentials (NPs), and denitrification potentials (DPs) were measured in natural, permeable, and impervious revetments in this study. Furthermore, structural equation models were developed to investigate the potential mechanism of the revetment’s impact on RRI NPs and DPs. The NPs of the natural revetment (NR) (7.22 mg/(kg·d)) were 2.20 and 2.16 times that of the impervious revetment (IR) and permeable revetments (PRs), respectively. The most important influencing factors of NPs were the aboveground biomass (AB) and available nitrogen. Similarly, the denitrification potential (DP) of the PR was 3.41 and 2.03 times that of the NR (22.44 mg/(kg·d)) followed by the IR (37.59 mg/(kg·d)). Furthermore, the AB had the greatest direct and total benefit on the DP, and nitrate may be a factor limiting the denitrification process. A revetment primarily disturbs the anaerobic environment and soil properties at RRIs, as well as changing the nitrification and denitrification potentials via soil erosion, solute exchange, and dry–wet alternation. These research results furnish a theoretical foundation for the restoration of urban rivers’ ecology and additionally provide benchmarks for sustainable development in urban areas.