Evaluation of nitrogen removal, functional gene abundance and microbial community structure in a stormwater detention basin

Abstract

Stormwater control measures such as detention basins are used to mitigate the negative effects of urban stormwater resulting from watershed development. In this study, the performance of a detention basin in mitigating nitrogen pollution was examined and the abundance of N-cycling genes (amoA, nirK, nosZ, hzsB and Ntsp-amoA) present in the soil media of the basin was measured using quantitative PCR. Results showed a net export of nitrogen from the basin, however, differences between in- and outflow concentrations were not significant. Furthermore, the quantitative PCR showed that nirK (denitrification gene) was more abundant in the winter season, whereas amoA (nitrification gene) was more abundant in the summer season. The abundance of nirK, Ntsp-amoA and hzsB genes also varied with the sampling depth of soil and based on 16S rRNA gene sequencing of soil samples, Actinobacteria and Proteobacteria were the most dominant phyla. Species diversity appeared higher in summer, while the top and bottom layer of soil clustered separately based on the bacterial community structure. These results underline the importance of understanding nitrogen dynamics and microbial processes within stormwater control measures to enhance their design and performance.

Keywords: Denitrification; High-throughput sequencing; Nitrification; Nitrogen cycling; Quantitative polymerase chain reaction; Stormwater.