LAUSR

Nanoparticles released into soil environment potentially impact microorganisms, which furtherly disturb terrestrial biogeochemical cycles. However, how rare earth oxide nanoparticles affect the functional microorganisms inhabited in natural soil is still unknown. This study was aimed to investigate the effect of different types of rare earth oxide nanoparticles on the ammonia-oxidizing microorganisms. Soil respectively added with 0, 10, 50, and 100 mg kg−1 of La2O3, Nd2O3, or Gd2O3 nanoparticle were incubated at 25 °C in the dark for 60 days. The potential ammonia oxidation (PAO), abundance and communities of ammonia-oxidizing archaea (AOA), and ammonia-oxidizing bacteria (AOB) were measured at the 1st, 7th, and 60th day. Our results showed that the PAO in soils with nanoparticles significantly decreased due to nanoparticle toxicity at the 1st day, but it gradually increased to the control level owing to the adaptation of AOA and AOB in soils with nano-Nd2O3 and nano-Gd2O3. Interestingly, the abundance of AOB as reflected by the qPCR analysis was upregulated for the hormesis effect of AOB responding to nano-Nd2O3 or nano-Gd2O3 with 50 mg kg−1 level. Moreover, terminal restriction fragment length polymorphism (T-RFLP) results suggested that the communities for AOA and AOB shifted with nanoparticles type and incubation time. Rare earth oxide nanoparticles could inhibit activities of ammonia-oxidizing microorganisms, and thus they might be used as potential nitrification inhibitors to improve nitrogen use efficiency in the agricultural ecosystems.