Spatiotemporal Evolution and Driving Factors of Soil NO Emissions in China from 2001 to 2020

With the continuous reductions in anthropogenic NOx emissions and persistent surface O3 pollution in China, soil NO emissions have become an increasingly important component of the regional NOx budget. In this study, an updated Berkeley–Dalhousie Soil NO Parameterization model driven by MERRA-2 reanalysis data was used to develop a 20-year soil NO emission inventory for China from 2001 to 2020. Multiple sensitivity scenarios were designed to quantify the relative contributions of nitrogen fertilizer application, meteorological variations, land use changes, and canopy factors on the interannual variations in soil NO emissions. The results showed that soil NO emissions exhibited an overall pattern of initial increase followed by fluctuating decline, with an average annual emission of 0.92 ± 0.05 Tg N year−1 and a peak of 0.98 Tg N year−1 in 2014. Summer was the dominant emission season, accounting for 57.7–61.9% of annual emissions. Spatially, emissions were concentrated in agriculturally intensive regions, particularly East China and Central China. With the decline in anthropogenic NOx emissions, the relative contribution of soil NO to total NOx emissions showed a recovery after 2012, indicating its increasing importance in future NOx budget assessments. Driver attribution analysis showed that nitrogen fertilizer application determined the long-term emission potential, whereas meteorological conditions regulated interannual and seasonal variability. These findings highlight the need to incorporate soil NO emissions into sustainable nitrogen management and ozone-related air quality assessments.