Nitrite stimulates HONO and NOx but not N2O emissions in Chinese agricultural soils during nitrification

Abstract

The long-lived greenhouse gas nitrous oxide (N2O) and short-lived reactive nitrogen (Nr) gases such as ammonia (NH3), nitrous acid (HONO), and nitrogen oxides (NOx) are produced and emitted from fertilized soils and play a critical role for climate warming and air quality. However, only few studies have quantified the production and emission potentials for long- and short-lived gaseous nitrogen (N) species simultaneously in agricultural soils. To link the gaseous N species to intermediate N compounds [ammonium (NH4+), hydroxylamine (NH2OH), and nitrite (NO2‒)] and estimate their temperature change potential, ex-situ dry-out experiments were conducted with three Chinese agricultural soils. We found that HONO and NOx (NO + NO2) emissions mainly depend on NO2‒, while NH3 and N2O emissions are stimulated by NH4+ and NH2OH, respectively. Addition of 3,4-dimethylpyrazole phosphate (DMPP) and acetylene significantly reduced HONO and NOx emissions, while NH3 emissions were significantly enhanced in an alkaline Fluvo-aquic soil. These results suggest that ammonia-oxidizing bacteria (AOB) and complete ammonia-oxidizing bacteria (comammox Nitrospira) dominate HONO and NOx emissions in the alkaline Fluvo-aquic soil, while ammonia-oxidizing archaea (AOA) are the main source in the acidic Mollisol. DMPP effectively mitigated the warming effect in the Fluvo-aquic soil and the Ultisol. In conclusion, our findings highlight the important role of NO2‒ in stimulating HONO and NOx emissions from dryland agricultural soils. In addition, subtle differences of soil NH3, N2O, HONO, and NOx emissions indicated different N turnover processes, and should be considered in biogeochemical and atmospheric chemistry models.