Spatial and seasonal patterns of atmospheric nitrogen deposition in North China

ABSTRACT As one of the regions with intensive agriculture and rapid economic development in China, North China also has a high nitrogen (N) deposition. This study characterized the spatial pattern of N deposition in North China, combining the tropospheric columns from satellite measurements and the simulated profiles from an atmospheric chemistry transport model. The total N deposition fluxes ranged from 16.3 to 106.5 kg N ha？1 yr？1, with an average of 54.5 ± 17.2 kg N ha？1 yr？1. The high values were concentrated in urban and farmland areas, while low values were found in forests and grasslands with less human activities. Of the total N deposition, 36% was deposited via precipitation, 12% was deposited through dry particulate deposition, and the remaining 52% was comprised of dry gaseous deposition. For the seasonal variation of dry deposition, gaseous HNO3 and particulate NO3 ？ were higher in winter and autumn, but lower in spring and summer. In contrast, gaseous NH3 and particulate NH4 + were higher in spring and summer, but lower in winter and autumn. This is possibly caused by the seasonal differences in emission intensity between NO x and NH3 emission sources. The gaseous NO2 deposition did not show strong seasonal variation. The wet deposition was mainly affected by precipitation, with high values in summer and low values in winter. This research provides an objective spatial perspective and insight into the total N deposition in North China. GRAPHICAL ABSTRAC