This study was performed at three eutrophic rivers in Southeast China aiming to determine the magnitude and patterns of dissolved N2O concentrations and fluxes over a seasonal (in 2009) and diurnal (24 h) temporal scale.The results showed that N2O concentrations varied from 0.28 to 0.38 (mean 0.32±0.04),0.29 to 0.46 (mean 0.37±0.07),and 2.07 to 3.47 (mean 2.84±0.63) μg N-N2O L-1 in the Fengle,Hangbu and Nanfei rivers,respectively,in the diurnal study performed during the summer of 2008.The study found that mean N2O concentration and estimated N2O flux (67.89 ± 6.71 μg N-N2O m-2 h-1) measured from the Nanfei River with serious urban wastewater pollution was significantly higher than those from the Fengle and the Hangbu Rivers with agricultural runoff.In addition,the seasonal study during June and December of 2009 also showed that the mean N2O concentration (10.59±14.67 μg N-N2O L-1) and flux (236.87±449.74 μg N-N2O m-2 h-1) observed from the Nanfei River were significantly higher than those from the other two rivers.Our study demonstrated both N2O concentrations and fluxes exhibited seasonal and diurnal fluctuations.Over three consecutive days during the summer of 2008,N2O accumulation rates varied within the range of 3.91-7.21,2.76-15.71,and 3.23-30.03 μg N-N2O m-2 h-1 for the Fengle,Hangbu and Nanfei Rivers,respectively,and exponentially decreased with time. This study was performed at three eutrophic rivers in Southeast China aiming to determine the magnitude and patterns of dissolved N2O concentrations and fluxes over a seasonal (in 2009) and diurnal (24 h) temporal scale. The results showed that N2O concentrations varied from 0.28 to 0.38 to 0.46 (mean 0.37 ± 0.07), and 2.07 to 3.47 (mean 2.84 ± 0.63) μg N-N2O L-1 in the Fengle, Hangbu and Nanfei rivers, respectively, in the diurnal study performed during the summer of 2008. The study found that mean N2O concentration and estimated N2O flux (67.89 ± 6.71 μg N-N2O m-2 h-1) measured from the Nanfei River with serious urban wastewater pollution was significantly higher than those from the the Fengle and the Hangbu Rivers with agricultural runoff. In addition, the seasonal study during June and December of 2009 also showed that the mean N2O concentration (10.59 ± 14.67 μg N-N2O L-1) and flux (236.87 ± 449.74 μg N-N2O m-2 h-1) observed from the Nanfei River were significantly hig her than those from the other two rivers. Our study demonstrated both N2O concentrations and fluxes exhibited seasonal and diurnal fluctuations. Over three consecutive days during the summer of 2008, N2O accumulation varied among the range of 3.91-7.21, 2.76-15.71, and 3.23-30.03 μg N-N2O m-2 h-1 for the Fengle, Hangbu and Nanfei Rivers, respectively, and exponentially decreased with time.