Contribution of Abiotic Pathways to N2o Production In Acidic Soils  with Hydroxylamine and Nitrite Addition

Abstract

Acidic soils are widely distributed in the world and can make great contribution to soil nitrous oxide (N2O) emission. However, the mechanisms responsible for N2O production in acidic soils remain unclear. In this study, we collected 16 acidic soils and one alkaline soil and conducted a laboratory incubation experiment by adding hydroxylamine (NH2OH) and nitrite (NO2-) to sterilized and non-sterile soils, to explore the contribution of abiotic processes to N2O production in acidic soils. Our results demonstrated that NH2OH and NO2- addition induced large amount of N2O production in the acidic and alkaline soils, with N2O conversion ratios of 4.0-114.3% and 3.1-16.3%, respectively. More than 60% of N2O production was attributed to abiotic processes with NH2OH and NO2- addition in acidic soils. Nevertheless, in the alkaline soil, abiotic processes contributed only 49% to total N2O production with NO2- addition. Further study showed that abiotic N2O production from NH2OH and NO2- was related to soil Mn and pH, respectively. Moreover, the values of N2O site preference (SP) with NH2OH and NO2- addition were 25‰-30‰ and around 20‰, which fell in the scopes of ammonia oxidation and chemodenitrification processes, respectively. Our results indicated that abiotic processes play crucial roles in N2O production from acidic soils.

Keywords: γ sterilization, acidic soil, abiotic processes, nitrification intermediates, chemodenitrification, N2O site preference