疏水性生物炭改性填埋场土壤覆盖层强化甲烷减排技术及其机理研究

Biochar-amended landfill cover become research fronts because it can minimize the adverse impacts of current biocover such as compost biocover, enhances methane transport and adsorption, and favors growth and methane oxidation activity of methanotrophs. Although biochar-amended landfill cover can enhance methane transport and adsorption, it can also promote the diffusion of the rainwater, and lead to the contradiction of waterproofness and gas permeability. Depending on the micro porous principle of the waterproof breathable material taking advantage of hydrophobic structure and micropore size, the project puts forward an integrated research program by hydrophobic biochar replacing ordinary biochar. The optimal parameters of waterproof and breathable coupling are determined by investigating the physical, geochemical and geotechnical properties of hydrophobic biochars and hydrophobic biochar-amended soils. The mechanism of methane transport and adsorption is determined and the optimal technical parameters of methane adsorption is obtained by researching the transport and enhanced adsorption of hydrophobic biochars and hydrophobic biochar-amended cover soils for methane and oxygen. The optimal operation parameters of promoting methane oxidation is obtained by investigating the rates of methane oxidation in hydrophobic biochars and hydrophobic biochar-amended soils. By porous ceramics replacing hydrophobic biochar, the mechanism of methane oxidation is revealed by the comparison of the rates of methane oxidation between porous ceramics-amended soils and hydrophobic biochar-amended soils. Based on the above research, a set of technology of enhancing methane mitigation in hydrophobic biochar-amended landfill soil cover is developed. It can improve the waterproofness and gas permeability of the cover material, and realize the maximization of methane oxidation. This project will result in a creative, low-cost, sustainable hydrophobic biochar-amended landfill soil cover to mitigate methane emissions at landfills and protect the environment and public health.

生物炭覆盖层因可克服传统生物覆盖层堵塞等缺点，促进甲烷氧化而成为覆盖层甲烷减排技术的前沿。但是添加生物炭促进甲烷和氧气扩散的同时，也会促进雨水的扩散，导致覆盖层防水透气的矛盾。根据防水透气材料利用材料的疏水结构和控制孔隙的微多孔原理，本项目提出采用疏水性生物炭替代普通生物炭，通过疏水性生物炭改性土壤物理化学性质的研究，确定其防水和透气耦合的最佳指标参数；通过疏水性生物炭改性土壤甲烷吸附研究，揭示甲烷吸附机理及变化规律，确定甲烷吸附的最佳技术参数；通过疏水性生物炭改性土壤甲烷氧化研究，获得促进甲烷氧化的最优操作参数和变化规律；采用多孔陶瓷颗粒替代生物炭，通过对比两者的甲烷氧化效果，揭示生物炭促进甲烷氧化的机理。在此基础上，形成一套疏水性生物炭改性土壤覆盖层强化甲烷减排技术，以改善覆盖材料的防水透气性能，实现甲烷减排的最大化。项目的研究将为填埋场甲烷减排提供技术支撑，具有重要的理论和应用价值。

针对填埋场生物炭土壤覆盖层甲烷氧化技术因促进CH4和O2扩散与防止雨水进入覆盖层存在矛盾，本研究提出采用疏水性生物炭替代普通生物炭，形成疏水性生物炭土壤覆盖层（RH），采用无机陶瓷材料替代生物炭，形成无机陶瓷材料改良土壤覆盖层（RC），同时设置传统土壤覆盖层（RS）、生物炭土壤覆盖层（RB）作为对照组，考察了其甲烷氧化性能；并借助高通量测序技术、荧光原位杂交（FISH）技术揭示了不同覆盖材料的微生物群落结构和功能微生物空间分布的变化规律。.结果表明，当模拟填埋气中CH4浓度为5-15%时，RB的甲烷减排性能提升较快,第81d时进气中99%的甲烷已被去除，RS在第95d时才达到99.16%的甲烷减排率；RS上、中、下3层的优势甲烷氧化细菌(MOB)为Methylocaldum，而RB的上层和中层为Methylobacter，下层则为Methylocaldum。至试验末期时，RS在上、中、下3层的总MOB相对丰度分别为9.05%、5.95%和42.12%，RB则分别为50.81%、42.67%和31.41%。同时在RS和RB中均检测出厌氧甲烷氧化古菌。由此表明生物炭的添加改变了填埋场土壤覆盖层的菌属分布，促进了MOB的生长,提高了甲烷减排性能。当模拟填埋气中CH4浓度为35%时，RB、RH和RC对CH4的总去除率分别为95.80%、99.50%和64.98%。RB和RH对CH4都表现出了较好的氧化效果，但是以RH最佳。在模拟降水条件下，RB和RH的总CH4去除率分别为71.59%和77.01%，RB和RH的含水率分别为31.22%和22.68%，渗透系数分别为1.15×10-7 m·s-1和7.68×10-8 m·s-1。RH对CH4的氧化能力比RB好，且防水能力更强。RB、RH和RC中不同深度相对丰度最大的细菌门类均为Proteobacteria，优势甲烷氧化菌属均为Methylobacter。RH上层的总甲烷氧化菌属的相对丰度比RB高13%以上，中层较RB低，下部相差不大，但RH使菌群在覆盖层中的分布更加均匀，且更有利于维护细菌群落多样性和丰度免受环境变化的影响。RC与RB的上层和中层差异不大，RC下层的总甲烷氧化菌属相对丰度比RB低10%以上。结合CH4的去除效果推测，RB较高的甲烷氧化效率是生物炭多孔结构和营养物质共同作用的结果。