红层包气带铁、锰对氮素生物转化的影响

Influence of iron and manganese in the vadose zone of red beds on the nitrogen biotransformation

研究红层土介导下Fe(Ⅲ)、Mn(Ⅱ)对硝化与反硝化优势菌种功能酶及氮转化的影响,结果表明Acinetobacter及Pseudomonas分别是红层包气带中硝化和反硝化效率最高的优势菌种.当Fe(Ⅲ)、Mn(Ⅱ)浓度分别为20、10mg/L时,优势菌硝化和反硝化效率最佳;当达到30mg/L左右后,受到抑制;达到60mg/L时,抑制明显.加入灭菌红层土的SFe0组硝化酶AMO、HAO比酶活比未加红层土的Fe0组提高了4.69%~107.5%,红层土添加明显促进了后期NH_4^(+)向NH_2OH的转化;反硝化酶NAR、NIR、NOS比酶活提高了9.16%~73.36%,明显促进了初期NO向N_2O的转化.SMn0组AMO、HAO提高了22.23%~120.29%,明显促进了后期NH_2OH向NO_(2)^(-)和NO_(3)^(-)的转化;反硝化酶NAR、NOR、NOS总体均有提高,明显促进了初期NO_(2)^(-)向NO的转化;在最适浓度下,SFe20组硝化和反硝化速率在0~12h分别提高了58.91%、121.17%,SMn10组分别提高了42.17%、55.68%;在抑制浓度下,SFe60组分别提高了61.79%、65.91%,SMn60组分别提高了30.26%、80.03%.红层土能够有效促进硝化和反硝化过程,缓解高浓度Fe(Ⅲ)、Mn(Ⅱ)的抑制作用.

The red beds vadose zone acts as a natural barrier against groundwater nitrogen pollution,but the influence of iron and manganese on the biotransformation of nitrogen remain unclear.Therefore,this study investigates the effects of Fe(Ⅲ)and Mn(Ⅱ)on the functional enzymes of dominant nitrifying and denitrifying bacterial species,as well as nitrogen conversion,mediated by the red beds vadose zone.The results showed that Acinetobacter and Pseudomonas were the dominant strains with the highest efficiency in nitrification and denitrification processes,respectively,in the vadose zone of the red beds.The optimal efficiency of nitrification and denitrification was observed at Fe(Ⅲ)and Mn(Ⅱ)concentrations of 20 and 10mg/L,respectively.However,inhibition of these processes occurred at concentrations around 30mg/L,and significant inhibition was observed at 60mg/L.The addition of sterilized red beds soil in the SFe0 group increased the activities of nitrification enzymes AMO and HAO by 4.69%~107.5%compared to the Fe0 group without red beds soil,promoting the conversion of NH_(4)^(+) to NH_(2)OH in the later stages.The activities of denitrification enzymes NAR,NIR,and NOS were increased by 9.16%~73.36%,facilitating the conversion of NO to N2O in the early stages.In the SMn(0)group,AMO and HAO activities were increased by 22.23%~120.29%,significantly promoting the conversion of NH_(2)OH to NO_(2)^(-)and NO3-in the later stages.Overall,the activity of denitrifying enzymes NAR,NOR,and NOS was enhanced,promoting the conversion of NO_(2)^(-)to NO in the early stages.At optimal concentrations,the SFe20 group were increased in nitrification and denitrification rates of 58.91%and 121.17%,respectively,while the SMn10 group were increased by 42.17%and 55.68%.Under inhibitory concentrations,the SFe60 group showed an increase of 61.79%and 65.91%in nitrification and denitrification rates,respectively,while the SMn60 group increased by 30.26%and 80.03%.The red beds vadose zone effectively promotes nitrification and denitrification processes and alleviates the inhibitory effects of high concentrations of Fe(Ⅲ)and Mn(Ⅱ).