Stable nitrogen isotope composition of NOx of biomass burning in China

Owing to the local characteristics of stable nitrogen isotopes in nitrogen oxides (delta N-15-NOx) emitted from biomass burning, the lack of data on delta N-15-NOx values associated with biomass burning in China limits the use of this parameter in identifying and quantifying the sources of atmospheric nitrate (NO3-) and NOx. The results showed that the delta N-15-NOx values of open burning and rural cooking stoves in China ranged from -3.7 parts per thousand to 3.1 parts per thousand and -11.9 parts per thousand to 1.5 parts per thousand, respectively. The delta N-15 values of nine biomass fuel sources (delta N-15-biomass) ranged from 0.1 parts per thousand to 4.1 parts per thousand. Significant linear relationships between the delta N-15-biomass values and delta N-15-NOx values of open burning (delta N-15-NOx = 1.1 delta N-15-biomass 2.7; r(2) = 0.63; p < 0.05) and rural cooking stoves (delta N-15-NOx = 1.7 delta N-15-biomass 9.8; r(2) = 0.72; p < 0.01) suggested that the variations in delta N-15-NOx values from biomass burning were mainly controlled by the biomass fuel source. The isotopic fractionation of nitrogen during the biomass burning process might have led to the higher delta N-15-NOx values from open burning in comparison to rural cooking stoves. By combining the delta N-15-NOx values of biomass burning with biomass burning emission inventory data, a model for calculating the delta N-15-NOx values of biomass burning in different regions of China was established, and the estimated delta N-15-NOx value of biomass burning at the national scale was -0.8 +/- 1.2 parts per thousand. But the limited delta N-15-biomass values increase the uncertainty of model in national scale. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that the stable nitrogen isotopes values of nitrogen oxides emitted from biomass burning in China are influenced by the biomass fuel sources, leading to increased uncertainty in the national scale model due to limited data on δ N-15-NOx values.