太湖梅梁湾沉积物中铁氧化氨作用及其脱氮贡献

Anaerobic Ammonium Oxidation Coupled to Ferric Iron Reduction and Its Contribution to Nitrogen Loss in the Sediment of Meiliang Bay, Lake Taihu

铁氧化氨反应是最近发现的一种新型氮转化途径,在林地、水稻田和湿地土壤氮循环过程中具有重要作用。然而,鲜有研究关注富营养化湖泊沉积物中的铁氧化氨过程。该研究在调查太湖梅梁湾沉积物理化性质和主要铁还原菌丰度的基础上,采用同位素示踪技术和C_2H_2抑制法研究了沉积物的铁还原速率和铁氧化氨过程,以实验过程中^(30)N_2和^(29)N_2的产生速率核算了沉积物的铁氧化氨速率。通过考察沉积物相关理化性质、铁还原菌丰度与铁氧化氨速率之间相关性,确定了这些因子对铁氧化氨的影响。结果表明:在太湖梅梁湾4个采样点的沉积物中均存在铁氧化氨过程,该过程能够在厌氧条件下将NH_4^+直接氧化为N_2,或者将NH_4^+氧化为NO_2^-、NO_3^-,然后厌氧氨氧化或反硝化过程将NO_2^-、NO_3^-转化为N_2导致沉积物氮损失。梅梁湾沉积物铁氧化氨速率范围为0.28~0.43 kg^(-1)·d^(-1),占太湖人为输入无机氮的6.1%~9.4%。沉积物Fe(Ⅲ)含量和TOC含量与铁氧化氨速率之间呈显著相关性(P>0.05),在铁氧化氨过程中起重要作用。相反,pH与铁氧化氨之间无显著相关性(P<0.05)。地杆菌属(Geobacteraceae spp.)、希瓦氏茵属(Shewanella spp.)、酸微菌科(Acidimicrobiaceae)及微酸菌A6属(Acidimicrobiaceae A6)与铁氧化氨呈显著相关性(P<0.05),表明铁还原菌可能直接参与铁氧化氨过程。综上,铁氧化氨是富营养化湖泊沉积物中氮素迁移转化的重要途径之一。

Anaerobic ammonium oxidation coupled to Fe(Ⅲ)reduction(Feammox)is a recently discovered pathway of nitrogen(N)transformation process which plays an important role in nitrogen cycling of forest soils,paddy soils and wetland soils.However,little information is known about the pathways of N transformation via Feammox process in the sediment of eutrophic lake.This study measured the physical and chemical characteristics and the abundances of iron reducing bacteria(FeRB)of sediment in eutrophic lake.The Fe(Ⅲ)reduction and the Feammox process were investigated by combining 15NH4+isotopic tracing and C2H2 inhibition method.The Feammox rates of sediment from Meiliang bay were calculated based on the 30N2 and 29N2 production rates.The effect of physical and chemical properties of sediment and the abundances of FeRB on the Feammox process were studied by analyzing the relationships between these factors and the Feammox rates.The results demonstrated that Feammox process occurred in all sediments from the four sampling sites in Meiliang Bay,Lake Taihu.N2 directly from the oxidation of NH4+by Feammox or Feammox-generated NO2-or NO3-followed by anammox or denitrification could cause the nitrogen loss from sediment of eutrophic lake.The rates of Feammox ranged from 0.28 to 0.43 kg^-1·d^-1,account for approximately 6.1%~9.4%of the human-induced inorganic N input annually into Taihu.The positive relationships between Fe(Ⅲ)content,TOC content and Feammox rates indicated that Fe(Ⅲ)and TOC might play a significant role in the Feammox process.In contrast,pH had little influence on Feammox rates in eutrophic lake sediment.The significant positive correlations between the Feammox rates and the abundances of Geobacteraceae spp.,Shewanella spp.,Acidimicrobiaceae and Acidimicrobiaceae A6(P<0.05)demonstrated that FeRB might have an essential role in Feammox process.Overall,Feammox is one of the important nitrogen conversion pathways in the sediment of eutrophic lake.