Effects of revetments on soil denitrifying communities in the urban river-riparian interface

Abstract

The river-riparian interface plays an important role in removal of nitrogen pollution. Many revetments have been built in urban riparian zones, which has affected soil denitrification function of river-riparian interface. However, the impacts of revetments on denitrifying communities of soil in the river-riparian interface are still unclear. In this study, in the case of eliminating the influence of plants, three modes of revetments (No Revetments (NR), Impervious Masonry Revetments (IR), and Permeable Concrete Imitation Pile Revetments (PR)) were employed to determine the influence of revetments on denitrifying communities of soil among three distances from revetments (1.0, 0.6 and 0.3 m). It was shown in comparison with IR and NR, PR promoted the abundance, diversity and relative abundance of major strains in nirS and nirK denitrifying bacteria (P < 0.05), but these effects decreased as distances increased. Compared with the IR (2.95 ± 1.15 × 10⁵ copies g^-1) and NR (4.13 ± 2.14 × 10⁵ copies g^-1), abundances of nirK denitrifying bacteria adjacent to PR (6.19 ± 1.89 × 10⁵ copies g^-1) were significantly higher (P < 0.05). Rubrivivax and Bradyrhizobium were the dominant bacterial genera, accounting for 16.02-23.94% and 29.25%-38.25% of nirS- and nirK- denitrifying bacteria, respectively. SOC and nitrogen availability were the primary factors which influence the gene richness of nirK and nirS, while soil bulk density, sand content and WFPS as the major elements were impacting compositions of nirK and nirS communities. The results will improve the comprehension of theoretical process of denitrification affected by revetment types.

Keywords: Denitrifying communities; Environmental factors; Revetments; nirK; nirS.