水铁矿对水稻土Feammox过程的影响及微生物群落分析

Effect of ferrihydrite on Feammox process in paddy soil and microbial community analysis

文章通过厌氧培养和乙炔抑制技术对水稻土进行模拟培养,证明水稻土中存在厌氧氨氧化耦合Fe(Ⅲ)还原,即铁氨氧化(Feammox)过程,并研究外加不同浓度水铁矿对Feammox过程产N_(2)速率及途径的影响。结果表明:水稻土中Feammox过程产N_(2)速率(以N计,下同)为(0.85±0.14)mg/(kg·d),在添加10、50 mmol/L水铁矿后,其产N_(2)速率分别为(0.86±0.15)mg/(kg·d)、(1.09±0.20)mg/(kg·d);水铁矿的加入能够促进氨氮直接通过Feammox过程氧化为N_(2),随着水铁矿浓度从10 mmol/L增加到50 mmol/L,Feammox过程直接产N_(2)途径占总产N_(2)的比例从49.41%增加到62.82%;Fe(Ⅲ)的还原速率与N_(2)的产率具有很强的相关性(R^(2)=0.901,p<0.01)。微生物群落分析结果表明,uncultured Acidimicrobiaceae、Anaeromyxobacter和Clostridium 3种菌的相对丰度随Feammox过程产N_(2)速率的增加而显著增加,3种菌可能参与Feammox过程。该文研究表明,水铁矿的加入促进Feammox过程中NH_(4)^(+)向N_(2)的直接转化,加速水稻土中氮元素的流失。

In this study,anaerobic culture and acetylene inhibition technology were used to simulate the cultivation of paddy soil,and the existence of anaerobic ammonium oxidation coupled to Fe(Ⅲ)reduction(Feammox)process in paddy soil was proved.The effects of adding ferrihydrite at different concentrations on Feammox rates and pathways were studied.The results showed that the Feammox rate(expressed by N)in paddy soil was(0.85±0.14)mg/(kg·d).Feammox rates after adding 10 mmol/L and 50 mmol/L ferrihydrite were(0.86±0.15)mg/(kg·d)and(1.09±0.20)mg/(kg·d).The addition of ferrihydrite could promote the oxidation of ammonia nitrogen to N_(2) directly through Feammox.As the concentration of ferrihydrite increased from 10 mmol/L to 50 mmol/L,the proportion of direct N_(2) production via Feammox to total gas production increased from 49.41%to 62.82%.It was found that the reduction rate of Fe(Ⅲ)was strongly correlated with the yield of N_(2)(R^(2)=0.901,p<0.01).Microbial community analysis results showed that the relative abundance of uncultured Acidimicrobiaceae,Anaeromyxobacter and Clostridium increased significantly with the increase of Feammox rate and might participate the Feammox process.Overall,this study illustrated that the addition of ferrihydrite facilitated the direct conversion pathway of NH_(4)^(+) to N_(2) via the microbial Feammox process,and accelerated nitrogen loss from paddy soil.