Abstract: The sources and sinks of atmospheric N₂O have already been well analyzed both on global and regional scales. However, the spatiotemporal distribution characteristics and mechanism of N₂O concentration in urban areas is relatively unclear. In this study, we investigated the spatial pattern and determinants of nearsurface urban N₂O concentration during spring in Shanghai, the commercial and financial center of China. A total number of 173 sampling points covering the whole urban area were collected and analyzed with gas chromatograph (GC). The results indicated that the average N₂O concentration for the region was 311.0±2.0 nmol·mol^-1, with the highest and lowest values in central city (312.0±1.4 nmol·mol^-1) and Qingpu district (309.9±1.7 nmol·mol^-1) of Shanghai, respectively. There was no significant correlation between the concentration of N2O and urbanization. N2O concentration in transportation area and commercial area differed from green land area. N₂O emission from urban rivers, biogenic sources in rural cropland soils and fossil fuel combustion were the main sources of near-surface N₂O in Shanghai.

Key words: soil organic carbon, biochar, mineralization, carbon sequestration., priming effect