Stable nitrogen isotope composition of NOx of biomass burning in China.

Owing to the local characteristics of stable nitrogen isotopes in nitrogen oxides (δ15N-NOx) emitted from biomass burning, the lack of data on δ15N-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 δ15N-NOx values of open burning and rural cooking stoves in China ranged from -3.7‰ to 3.1‰ and -11.9‰ to 1.5‰, respectively. The δ15N values of nine biomass fuel sources (δ15N-biomass) ranged from 0.1‰ to 4.1‰. Significant linear relationships between the δ15N-biomass values and δ15N-NOx values of open burning (δ15N-NOx = 1.1δ15N-biomass - 2.7; r2 = 0.63; p < 0.05) and rural cooking stoves (δ15N-NOx = 1.7δ15N-biomass - 9.8; r2 = 0.72; p < 0.01) suggested that the variations in δ15N-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 δ15N-NOx values from open burning in comparison to rural cooking stoves. By combining the δ15N-NOx values of biomass burning with biomass burning emission inventory data, a model for calculating the δ15N-NOx values of biomass burning in different regions of China was established, and the estimated δ15N-NOx value of biomass burning at the national scale was -0.8 ± 1.2‰. But the limited δ15N-biomass values increase the uncertainty of model in national scale.