地下水与地表水相互作用下硝态氮的迁移转化实验

全球水体氮污染形势严峻，且以硝态氮(NO₃--N)污染为主，研究地下水与地表水(G-S)相互作用模式对NO₃--N在“潜流带”(HZ)中迁移转化的影响是开展水体氮污染综合防控的关键.开展地表水(S)补给地下水(G)(下降流)、地下水(G)补给地表水(S)(上升流)以及交替作用3种模式的NO₃--N迁移转化实验，研究表明:3种模式下，出水NO₃--N浓度可降低95%以上；上升流中反硝化强度大于下降流；异化还原作用(DNRA)对下降流与上升流出水氨氮(NH₄+-N)浓度的贡献分别约为71%和11%；上升流实验后水-土界面有机氮含量是下降流实验后水-土界面的2.3倍.结果表明，G-S相互作用下NO₃--N的衰减途径主要包括:合成有机氮、反硝化及DNRA；相互作用模式对各衰减途径的强度存在影响；HZ介质通过吸附NH₄+-N和微生物作用合成有机氮的方式截留氮素. 

Experiment on Migration and Transformation of Nitrate under Interaction of Groundwater and Surface Water

At present, the situation of water nitrogen pollution in the world is grim, and nitrate (NO₃--N) pollution is the main form. To study the effects of groundwater and surface water (G-S) interaction on the migration and transformation of NO₃--N in the hyporheic zone (HZ) is the key for comprehensive prevention and control of water nitrogen pollution. Three modes of NO₃--N migration and transformation experiments, including surface water (S) supply for groundwater (G) (down-welling), groundwater (G) supply for surface water (S) (up-welling) and the alternative mode, were carried out in the study. It is found that NO₃--N concentration of three modes effluent can be reduced more than 95%; the strength of denitrification in up-welling was greater than in down-welling; the contribution of the dissimilation reduction (DNRA) to the ammonia nitrogen (NH₄+-N) concentration in the outflow of down-welling and up-welling was about 71% and 11%, respectively. After up-welling experiment, the organic nitrogen content of water-soil interface was 2.3 times as much as the down-welling experiment. It was shown that the NO₃--N attenuation pathways under the G-S interaction mainly include denitrification, DNRA and the synthesis of organic nitrogen; G-S interaction modes had effects on the strength of each NO₃--N attenuation pathway; HZ media could intercept nitrogen through the adsorption of NH₄+-N and microbial synthesis of organic nitrogen.