The influence of silver nanoparticles (AgNPs) on the denitrification performance, enzyme activity, and functional gene relative abundances of sediment was investigated based on the methods of laboratory simulation incubation in the Dagu River estuary and bay area in the northwest of Jiaozhou Bay. The different dosages of AgNPs (i.e., 0, 135, and 1350 mg·L-1 in final concentration) was added to the incubation system containing surface sediments and in-situ bottom water. During six days' incubation, the concentrations of NO3- and NO2-, NO3-, and NO2- reductases activity, and relative abundances of narG and nirS genes were measured to explore the effects of AgNPs on denitrification and its mechanism. The results showed that AgNPs significantly inhibited NO3- and NO2- reductive capacity, NO3- and NO2- reductase activity, and narG and nirS gene relative abundances, which led to aggravated accumulation of NO2-. The inhibition of NO2- reductase was significantly greater than that of NO3- reductase, and the inhibition of the nirS gene was significantly higher than that of the narG gene. The inhibition of NO3- reduction was mainly ascribed to the inhibition of functional genes, but the inhibition of NO2- reduction was mainly due to the inhibition of reductase activity. The inhibition of NO3- and NO2- reductive capacity, NO3- reductase activity, and narG and nirS gene relative abundances in the northwest of Jiaozhou Bay was significantly higher than that in the Dagu River estuary.
Keywords: Jiaozhou Bay; denitrification; gene abundances; reductase activity; silver nanoparticles.