Abstract:

In this study, a microcosm experimental system was established to assess the effect of tubificid worms on the removal of nitrogen from anaerobic sediment water through oxygen-carrying zeolite capping as well as the potential mechanism underlying this process. The results indicated that the application of oxygen-carrying zeolite significantly increased the dissolved oxygen (DO) concentration in the overlying water after 20 days and was 2.78 times higher than that of the control group. However, the presence of tubificid worms was responsible for a 56.73% reduction in DO concentration compared to the control but promoted the diffusion of oxygen bubbles released from the oxygen-carrying zeolite to the deeper layers of the sediment. Therefore, the DO concentration was significantly higher than that of the group with oxygen-carrying zeolite capping (3.77‒0.47 mg∙L⁻¹). Meanwhile, the presence of tubificid worms increased the abundance of denitrifying bacteria, such as Comamonadaceae in the sediment and Novosphingobium and Proteiniclasticum in the capping layer. After 20 days incubation, the concentration of total nitrogen in the overlying water reached 9.89 mg∙L⁻¹ (oxygen-carrying zeolite group), 10.40 mg∙L⁻¹ (oxygen-carrying zeolite+Tubificid worm group), 11.60 mg∙L⁻¹ (zeolite group), 12.49 mg∙L⁻¹ (zeolite+Tubificid worm group), 18.59 mg∙L⁻¹ (control group), and 20.99 mg∙L⁻¹ (Tubificid worm group), respectively. However, irrespective of the presence of Tubificid worms, nitrous oxide emission upon application of oxygen-carrying zeolite at the end of the incubation period was not influenced and was significantly lower than that of other treatments (p<0.05). The results indicated that the downward movement of tubificid worms in the sediment facilitated the influence of oxygen-carrying zeolite in the deeper sediment, thereby increasing the DO concentration in the sediment, altering the microbial community structure, and benefiting nitrogen removal in deeper sediment layers.

Key words: endogenous pollution, oxygen-carrying material, zeolite, tubificid worm, nitrogen

摘要： 以粉煤灰基载氧沸石为覆盖材料，通过构建沉积物柱试验体系，探究了在水丝蚓（Limnodrilus Claparède）的影响下覆盖粉煤灰基载氧沸石后厌氧沉积物-水体系氮的去除效果与潜在机制。结果表明，覆盖20 d后，粉煤灰基载氧沸石覆盖显著提升了上覆水中溶解氧（DO）浓度，较对照升高2.78倍。但水丝蚓的存在促进了粉煤灰基载氧沸石中的氧气向深层沉积物的扩散，导致上覆水DO浓度较对照降低了56.73%，且表层沉积物剖面中DO浓度显著高于粉煤灰基载氧沸石组（3.77－0.47 mg∙L⁻¹）；同时，表层沉积物中Comamonadaceae和覆盖层中的Novosphingobium、Proteiniclasticum等反硝化菌的丰度明显提升。因此，20 d后各处理组上覆水中的总氮含量为9.89 mg∙L⁻¹（粉煤灰基载氧沸石组）、10.40 mg∙L⁻¹（粉煤灰基载氧沸石+水丝蚓组）、11.60 mg∙L⁻¹（粉煤灰基不载氧沸石组）、12.49 mg∙L⁻¹（粉煤灰基不载氧沸石+水丝蚓组）、18.59 mg∙L⁻¹（对照组）、20.99 mg∙L⁻¹（水丝蚓组），但实验结束时，水丝蚓的存在并未增加粉煤灰基载氧沸石覆盖下氧化亚氮释放通量（均显著低于其他处理组，p<0.05）。沉积物中水丝蚓向下运动能够使粉煤灰基载氧沸石作用到更深处的沉积物中，从而提高沉积物中的溶解氧含量，同时改变了微生物群落结构，进而促进了深层沉积物脱氮。

关键词: 内源污染, 载氧材料, 沸石, 水丝蚓, 氮