[Nitrogen Release from Sediment Under Dry and Rainy Season Alternation and Its Contribution to N Export from Xiangxi Watershed in Jiangxi Province].

In this study, N export from Xiangxi River Basin in Qianyanzhou station was measured by long-term monitoring, and simulation study on N. release law from the sediment in watershed was carried out based on orthogonal experiment, and at last the contributions of N release from sediment to N transport from watershed under dry and rainy season alternation were estimated. The results showed that the maximum of TN release rate was 36 mg x (m2 x d)(-1) in stable status, which decreased with increasing time; the impact of the three controlling factors on the N release followed the order of temperature > disturbance > pH, and the effect of temperature and pH on N release from the sediment was significant when disturbance was considered as the error term; TN release rate increased with increase of temperature, and acidic and alkaline conditions could also promote N release from sediment, wherein the effect of acidic conditions on N release was stronger; the changes of TN and available N content in sediment were 414.7-899.6 mg x kg(-1) and 17.5-58.9 mg x kg(-1), so the percentage of available N only accounted for 3%-10% of TN; the TN transport concentrations were 0.58-2.40 mg x L(-1) and 1.73-4.87 mg x L(-1) in dry and wet seasons, respectively, the N release flux from sediment was about 106.34 kg x a(-1), the total N transport from watershed was 864.15 kg x a(-1), and the contribution rate of N release from sediment to N transport from watershed was about 12.31%, so we should pay much attention to the contribution of N release from sediment to water eutrophication.