Seasonal and spatial characterisation of soil properties, nitrification and denitrification at the urban river-riparian interface with permeable revetments

Abstract

Understanding the seasonal and spatial variation characteristics and formation mechanism of soil nitrification and denitrification on permeable revetment can provide basis for revetment design and protecting the ecological function of river-riparian interface. In this study, permeable imitation wooden pile revetments, commonly used in Shanghai, were selected. In spring, summer and autumn, soil samples were collected and tested at different distances from the river and depths in the river-riparian interface. The seasonal and spatial variation characteristics of nitrification and denitrification potentials their relationships with soil properties were analysed. The results indicated the seasonal change of soil structure indexes were not significant, but that of the material content related indexes were significant. The influence of soil depth on soil properties is greater than the distance from the river. The soil nitrification potentials during spring (4.43 ± 4.26 mg kg−1 d−1) and autumn (5.24 ± 4.54 mg kg−1 d−1) were significantly higher than that during summer (3.53 ± 2.66 mg kg−1 d−1), whereas the soil denitrification potential was significantly higher during summer (11.65 ± 9.20 mg kg−1 d−1) than during autumn (10.79 ± 8.33 mg kg−1 d−1) and spring (10.21 ± 7.11 mg kg−1 d−1). The seasonal variations of the soil nitrification and denitrification potentials in the occasionally flooded area (0–20 cm depth) were larger than in the frequently flooded area (25–45 cm depth) and the permanently flooded area (55–75 cm depth). The seasonal and spatial differences determine the state of soil submergence, resulting in the difference in soil’s properties, leading to the difference in nitrification and denitrification intensity. The results of this study can provide the guidelines for urban revetment construction for nitrogen removal in riparian zones.