Important contributions of non-fossil fuel nitrogen oxides emissions.

ABSTRACT: Since the industrial revolution, it has been assumed that fossil-fuel combustions dominate increasing nitrogen oxide (NO_x) emissions. However, it remains uncertain to the actual contribution of the non-fossil fuel NO_x to total NO_x emissions. Natural N isotopes of NO₃^- in precipitation (?¹⁵N_w-NO3-) have been widely employed for tracing atmospheric NO_x sources. Here, we compiled global ?¹⁵N_w-NO3- observations to evaluate the relative importance of fossil and non-fossil fuel NO_x emissions. We found that regional differences in human activities directly influenced spatial-temporal patterns of ?¹⁵N_w-NO3- variations. Further, isotope mass-balance and bottom-up calculations suggest that the non-fossil fuel NO_x accounts for 55?±?7% of total NO_x 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 NO_x emissions and provide direct evidence for making strategies on mitigating atmospheric NO_x pollution.

SUBMITTER: Song W 

PROVIDER: S-EPMC7801390 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature