Abstract
Since the industrial revolution, it has been assumed that fossil-fuel combustions dominate increasing nitrogen oxide (NOx) emissions. However, it remains uncertain to the actual contribution of the non-fossil fuel NOx to total NOx emissions. Natural N isotopes of NO3− in precipitation (δ15Nw-NO3−) have been widely employed for tracing atmospheric NOx sources. Here, we compiled global δ15Nw-NO3− observations to evaluate the relative importance of fossil and non-fossil fuel NOx emissions. We found that regional differences in human activities directly influenced spatial-temporal patterns of δ15Nw-NO3− variations. Further, isotope mass-balance and bottom-up calculations suggest that the non-fossil fuel NOx accounts for 55 ± 7% of total NOx emissions, reaching up to 21.6 ± 16.6Mt yr−1 in East Asia, 7.4 ± 5.5Mt yr−1 in Europe, and 21.8 ± 18.5Mt yr−1 in North America, respectively. These results reveal the importance of non-fossil fuel NOx emissions and provide direct evidence for making strategies on mitigating atmospheric NOx pollution.
Highlights
Since the industrial revolution, it has been assumed that fossil-fuel combustions dominate increasing nitrogen oxide (NOx) emissions
It is almost impossible to budget NOx emission amounts from diverse biomass burnings and microbial N cycles that occur in different solid- and liquidphase substrates[16,17,18]
According to the simulation results of atmospheric chemical transport and terrestrial ecosystem models, biomass burning and soil emissions account for about 20% and 22% of global NOx emissions, respectively[19,20,21]
Summary
It has been assumed that fossil-fuel combustions dominate increasing nitrogen oxide (NOx) emissions. To investigate the importance of non-fossil fuel NOx emissions to total NOx emissions, we compiled available δ15 N values of NO3− in precipitation (denoted as δ15Nw-NO3− hereafter) at urban and non-urban sites of East Asia, Europe, and North America (detailed in “Methods”) (Fig. 1).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
