Effects Of Biochar On Microbial Iron Reduction In Different Paddy Soils

Biochar is attracting many researchers because it has been one of the most important wayof agricultural and forestry waste recycling in China. The biochar has many physical andchemical properties, such as specific surface area, pore over, strong stability, high carboncontent, high ash content and so on, which have been used in agricultural soil improvementwidely. Biochar is also used in decreasing the emission of greenhouse gases.It can maximizeCO2, CH4, NOx and other greenhouse gases effectively. Paddy soil as the main source ofatmospheric greenhouse gases, methane production control has been the focus of intenseresearchers. Many studies found that it can occur microbial Fe(Ⅲ) reduction in the paddy soil,which process can be the inhibition of methanogenesis in paddy soil. Biochar and themicrobial Fe(Ⅲ) reduction would be the effective ways to suppress the emission ofgreenhouse gases. However, the relationship between them is not clearly. In this study, wesimulate the flooded anaerobic environment of paddy soil, and then add the biochar into thesoil to explore the relationship between biochar and microbial Fe(Ⅲ) reduction. Theexperiment is divided into four parts: the first is adding different content of Pagoda tree barkbiochar into acidic and alkaline paddy soil to discuss how the different amount of biochareffecting on the microbial Fe(Ⅲ) reduction process. Secondly, adding equal amount of threekinds of biochar: Pagoda tree bark biochar, apple tree biochar and the sawdust biochar into theexperimental system to explore how the different kinds of biochar to effect the microbialFe(Ⅲ) reduction; And then, exerting the same amount of different size of Pagoda tree barkbiochar into the paddy soil to research the affection of different particle size of biochar on themicrobial Fe(Ⅲ) reduction process, and adding the electron donor, electron acceptor andbiochar into the paddy soil system to study how they have effects on the microbial Fe (Ⅲ)reduction process.The research got principle conclusions as follows though anaerobic mud culture andmeasuring system Fe (Ⅱ) concentration and pH value:(1) adding different amounts of Pagoda tree bark biochar to the acidic paddy soil and alkaline paddy soil, the Fe (Ⅱ) concentration inthe paddy soil and the pH value are increasing with the increase of the amounts of Pagoda treebark biochar.(2) By scanning electron microscopy to determine the surface of Pagoda treebark biochar is the roughest one, and apple tree biochar is the smoothest one. The microbialFe(Ⅲ) reduction reaction of three kinds of biochar was not obvious difference.(3) With thedecreasing of particle size of biochar, the total amount of iron and Fe(Ⅱ) contention areincreasing, the anaerobic system microbial Fe(Ⅲ) reduction process role in promotingstronger.(4) In the condition of adding biochar, pH value in anaerobic system increased whenadded electronic donor (glucose), which could promote microbial Fe(Ⅲ) reduction in such asystem. The maximum Fe(Ⅱ) accumulation would be increased with adding electronicacceptor (amorphous iron oxide) into paddy soil. pH value would be increased with addingbiochar when both electronic acceptor and electronic donor exist in the system. Meanwhile,Fe(Ⅲ) reduction process can be promoted in acidic paddy soils in this condition.