| Abstract: | Silver nanoparticles (AgNPs) have been widely used in medicine and consumer products. And it enters the river in dif-ferent ways, then finally converges to the ocean through the estuary. AgNPs polution can affect NO2? and N2O production by denitri-fiers in aquatic system. The effects of AgNPs on denitrification activity, nitrogen transformation and nitrous oxide (N2O) emission were investigated in Dagu River Estuary (DRE) and Jiaozhou Bay (JZB). The results showed that the potential denitrification activity (PDA), NO3? and NO2? reduction rates decreased with an increase of AgNPs concentration in DRE and JZB. However, the N2O ac-cumulation was significantly increased at AgNPs concentrations above 5 mg kg?1 in both areas, and the accumulation rate was greater in estuary than in bay (P < 0.05). Moreover, the total bacterial count showed a slightly increasing trend with an increase of AgNPs concentration (P > 0.05) in DRE and JZB. Importantly, the relative abundance of narG, nirS and nosZ gene in two areas decreased with the increase of AgNPs concentration, and the negative effect of AgNPs varied in order: nosZ>nirS>narG, inferring that the expression of denitrifying related genes could be significantly and differently inhibited by AgNPs addition. Thus, this study demon-strated that the inhibitory effect of AgNPs on different denitrification process, which may lead to the increase of inorganic nitrogen accumulation and N2O realease. This study provides a scientific basis for the further studies of AgNPs on the ecological impact mechanism and environmental effects of offshore sedimentary environment. |
