Estimation of monthly bulk nitrate deposition in China based on satellite NO2 measurement by the Ozone Monitoring Instrument

Remote sensing technology has great potential to expand the observation of ground-level nitrogen deposition from local monitoring sites to a regional scale, with high spatial and temporal resolutions. A new methodology is developed to estimate the spatial distribution of monthly bulk nitrogen deposition on a regional scale, based on precipitation amounts and HNO3 and aerosol nitrate (NO3−) columns, derived from OMI NO2 columns and the relationship of NO2, HNO3 and NO3− from MOZART. The accuracy assessment shows that the proposed model has achieved a reasonably high predictive power for monthly NO3−-N deposition (slope = 0.96, intercept = 0.35, R = 0.83, RMSE = 0.72) across China. The spatial NO3−-N deposition shows a significant gradient from industrial areas to undeveloped regions, ranging from 0.01 to 26.76 kg N ha− 1 y− 1 with an average of 5.77 kg N ha− 1 y− 1 over China during 2010-2012. The bulk NO3−-N deposition shows a clear seasonal variation, with high depositions occurring in the warm season (March-November) and peaking in July and August, and low bulk NO3−-N deposition appearing in winter (December-February). This study proves for the first time that the atmospheric boundary layer (ABL) HNO3 and NO3− columns and precipitation are powerful to predict the bulk nitrate deposition.