Nitrogen process in stormwater bioretention: effect of the antecedent dry days on the relative abundance of nitrogen functional genes

Abstract

In this study, we evaluated the relative abundance of nitrogen functional genes (amoA, nirK and nirS) involved in ammonia oxidation and denitrification bacteria in laboratory-scale bioretention columns in response to the environmental factors (e.g., moisture content, pH, soil organic matter, soil nitrogen) under different antecedent dry days (ADDs). We observed a decrease tendency of the relative abundance of ammonia-oxidizing bacteria at first and then increase when increasing ADDs from 1 to 22 day, while the relative abundance of denitrifying bacteria shown a downward trend. The abundance of bacteria genes amoA was positively associated with soil ammonia nitrogen concentration (r2 = 0.389, p < 0.05) and soil organic matter concentration (r2 = 0.334, p < 0.05), while the abundance of bacteria genes nirS was positively correlated with soil ammonia nitrogen (r2 = 0.730, p < 0.01), soil organic matter (r2 = 0.901, p < 0.01) and soil total nitrogen (r2 = 0.779, p < 0.01). Furthermore, Gene counts for bacteria genes nirS was correlated negatively with plant root length (r2 = 0.364, p < 0.05) and plant biomass (r2 = 0.381, p < 0.05). Taken together, these results suggest that both nitrification and denitrification can occur in bioretention system, which can be affected by environmental factors.