外源碳氮输入对沟道底泥反硝化潜势与阈值影响——以宁夏引黄灌区排水沟为研究对象

采集宁夏引黄灌区排水沟道底泥，开展上覆水土柱培养试验，分别模拟0，5，10，20mg/L 4种外源氮输入梯度和0，100mg/L 2种外源碳输入梯度处理下沟道水质的变化情况.在水力停留培养47d内对上覆水NO₃^--N、NH₄⁺-N、DOC及反硝化速率进行测定，并计算氮素消纳量以评估底泥反硝化脱氮潜势与阈值.结果表明：上覆水NO₃^--N浓度随时间延长而降低（P<0.01），且同时段内上覆水NO₃^--N浓度在外源碳添加较无碳源条件下显著降低（P<0.05），试验末期NO₃^--N浓度在无碳源和添加碳源条件下分别下降52.1%，93.6%；添加碳源条件下上覆水NO₃^--N浓度在20d时已稳定至较低水平，而未添加碳源处理NO₃^--N浓度在试验47d后仍有较大消纳空间；无碳源和添加碳源条件下底泥反硝化氮素消纳量阈值分别为263.7，865.6μmol/L，氮素累积消纳量占培养柱体系内总氮量的比率随外源碳氮的增加而增大（P<0.05），未添加碳源条件下反硝化过程可以消纳培养土柱体系内10.3%~11.4%的氮量，而在添加碳源后提高至17.7%~37.3%本研究可为引黄灌区农业面源污染高效治理提供科学依据.

Impact on denitrification potential and threshold of ditches sediment with exogenous carbon and nitrogen addition: A case of ditches in Ningxia Yellow River Irrigation area

In this study, laboratory incubation experiments were conducted for sediment denitrification potential study in farmland ditches of the Yellow River Diversion Irrigation Area of Ningxia. Experiments were conducted under condition of four exogenous nitrogen concentration gradients of 0, 5, 10, 20mg/L and two exogenous carbon concentration gradients of 0 and 100mg/L in the overlying water. The NO₃^--N, NH₄⁺-N, and DOC concentration of the overlying water were measured as well as denitrification rates during 47days of incubation to evaluate the denitrification potential and its threshold. The results showed that sediment denitrification increased with the increase of exogenous nitrogen and of carbon. The NO₃^--N concentration of the overlying water decreased with the time (P<0.01), but the concentration of NO₃^--N in the overlying water decreased significantly with the addition of exogenous carbon compared with the condition without carbon source (P<0.05). At the end of the experiment, NO₃^--N concentration decreased by 52.1% and 93.6% respectively without and with carbon sources. Under the condition of adding carbon source, the concentration of NO₃^--N in the overlying water stabilized to a low level at 20d, while the concentration of NO₃^--N in the treatment without carbon source addition still had a large decreasing space after 47d of the incubation. The thresholds of denitrification removal rate in sediment without carbon source and with carbon source were 263.7 and 865.6µmol/L, respectively. The ratio of cumulative nitrogen removal to total nitrogen in the culture column system increased with the increase of exogenous nitrogen and carbon source (P<0.05), denitrification process could remove 10.3%~11.4% of nitrogen in the culture column system without exogenous carbon, but increased to 17.7%~37.3% with the exogenous carbon addition. In conclusion, This study can provide scientific basis for efficient control of agricultural non-point source pollution in the irrigated area of Yellow River diversion.