Assessment of N2O, NOx and NH3 emissions from a typical rural catchment in Eastern China

To evaluate the atmospheric load of reactive gaseous nitrogen in the fast-developing Eastern China region, we compiled inventories of nitrous oxide (N₂O), nitrogen oxide (NO_x) and ammonia (NH₃) emissions from a typical rural catchment in Jiangsu province, China, situated at the lower reach of the Yangtze River. We considered emissions from synthetic N fertilizer, human and livestock excreta, decomposition of crop residue returned to cropland and residue burning, soil background and household energy consumption. The results showed that, for the 45.5 km² catchment, the annual reactive gaseous emission was 279 ton N, of which 7% was N₂O, 16% was NO_x and 77% was NH₃. Synthetic N fertilizer application was the dominant source of N₂O and NH₃ emissions and crop residue burning was the dominant source of NO_x emission. Sixty-seven percent of the total reactive gaseous N was emitted from croplands, but on a per unit area basis, NO_x and NH₃ emissions in residential areas were higher than in croplands, probably as a result of household crop residue burning and extensive human and livestock excreta management systems. Emission per capita was estimated to be 18.2 kg N year⁻¹ in the rural catchment, and emission per unit area was 56.9 kg N ha⁻¹year⁻¹ for NH₃ + NO_x, which supports the observed high atmospheric N deposition in the catchment. Apparently, efficient use of N fertilizer and biological utilization of crop straw are important measures to reduce reactive gases emissions in this rural catchment.