沉积物碳氮交互效应及其对河流水体脱氮治理的影响——以厦门市西溪中下游为例

Interaction effect of sediment carbon and nitrogen and its influence on nitrogen removal in river water——A case study of the middle and lower reaches of Xixi River in Xiamen

通过福建厦门市内陆河流西溪中下游上覆水及沉积物中碳氮理化指标的时空分布特征,利用碳(13C)、氮(15N)稳定同位素技术研究了沉积物中厌氧氨氧化(ANAMMOX)、反硝化(denitrification)及反硝化型厌氧甲烷氧化(DAMO)的反应速率及其分布规律。结果表明:西溪中下游上覆水水质总氮为3.02~5.68mg·L^(-1);利用15N同位素技术测得西溪中下游沉积物中厌氧氨氧化的平均速率为18.953μmol·m^(-2)·h^(-1),平均脱氮贡献率为40.13%,反硝化平均速率为27.386μmol·m^(-2)·h^(-1),平均贡献率为59.87%;起主要脱氮贡献的为反硝化反应,但厌氧氨氧化的脱氮作用仍不可忽视。利用13C同位素技术测得西溪中下游沉积物中DAMO反应速率为0~6.122μmol·m^(-2)·h^(-1),平均速率为1.139μmol·m^(-2)·h^(-1)。这表明西溪中下游沉积物中存在DAMO反应,可在厌氧条件下以硝酸盐作为电子受体将CH_(4)转化为CO_(2)。在空间上,西溪中下游DAMO速率存在较大差异性;而在时间上,DAMO速率秋季高于冬春季。反硝化与厌氧氨氧化作用对西溪生态系统中脱氮具有重要意义,DAMO在西溪中下游沉积物虽然反应速率较低,但仍然证明了西溪沉积物生态系统存在连接碳氮循环的微生物反应。反硝化、厌氧氨氧化和DAMO的相互协同,在西溪中下游沉积物脱氮治理及相应过程中的温室气体减排中起到重要作用。

Based on the spatial and temporal distribution characteristics of carbon and nitrogen physical and chemical indexes in overlying water and sediments of the middle and lower reaches of Xixi River in Xiamen City,Fujian Province,the reaction rates and distribution of Anaerobic ammonia oxidation (Anammox),Denitrification and denitrifying anaerobic methane oxidation (DAMO) in sediments were studied by using carbon (13C) and nitrogen (15N) stable isotope techniques.The results showed that the total nitrogen concentration of overlying water in the middle and lower reaches of Xixi River ranged from 3.02 to 5.68 mg·L^(-1).The average rate of anaerobic ammonia oxidation in the sediments of the middle and lower reaches of Xixi River was 18.953μmol·m^(-2)·h^(-1),and the average contribution rate of denitrification was 40.13%.The average rate of denitrification was 27.386μmol·m^(-2)·h^(-1)and the average contribution rate was 59.87%.The main contribution of denitrification was denitrification,but the denitrification effect of anaerobic ammonia oxidation could not be ignored.The DAMO reaction rate was 0~6.122μmol·m^(-2)·h^(-1)and the average rate was 1.139μmol·m^(-2)·h^(-1)measured by13C isotope technique in the sediments of the middle and lower reaches of Xixi River,indicating that there was DAMO reaction in the sediments of the middle and lower reaches of Xixi River,which could convert CH_(4)into CO_(2)with nitrate as electron acceptor under anaerobic conditions.In space,the DAMO rate in the middle and lower reaches of Xixi River was quite different;in terms of time,the DAMO rate in autumn was higher than that in winter and spring.Denitrification and anammox were important for nitrogen removal in Xixi ecosystem.Although the reaction rate of DAMO in the sediments of the middle and lower reaches of Xixi was low,it still proved that there were microbial reactions connecting carbon and nitrogen cycles in Xixi sediment ecosystem.Denitrification,anammox and DAMO synergistically played an important role in sediment nitrogen removal and greenhouse gas emission reduction in the middle and lower reaches of Xixi River.