填埋场生物炭-甲烷氧化菌改性覆层的甲烷氧化特性

填埋场覆盖层是一种控制甲烷逃逸的最简单可行办法，然而一般的土质覆盖层工程特性差，与微生物甲烷氧化菌的甲烷氧化效能低。生物炭施加到土体中能够改变土体的微环境和微生物活性，进而可影响生物氧化甲烷的效能。为了研究生物炭-甲烷氧化菌改性土的甲烷氧化效率，使用甲烷检测仪，测定不同pH、甲烷浓度、土样干密度和生物炭掺量下，有菌和无菌土样的甲烷降低率的变化规律。结果表明：当无机盐培养液的pH值为7时，甲烷氧化菌具有较高的氧化效能；pH值为9时，甲烷氧化菌的甲烷降低小于pH值为7时。在一定初始甲烷浓度下，甲烷氧化菌的氧化效能随着初始甲烷浓度的增大而增大，但当初始甲烷浓度超过一定值时会抑制甲烷氧化菌的氧化效能，生物炭掺量和干密度均会影响甲烷氧化菌甲烷削减效能。随着生物炭掺量的增加，生物炭-甲烷氧化菌改性土的甲烷氧化效率是逐渐增大的；在干密度和生物炭掺量为1.20 g/cm³和15%时，无菌和有菌两种工况的甲烷降低率降幅较明显，分别为10.38%和39.72%。由此表明添加生物炭改变了填埋场覆盖层土体的微环境，提高了甲烷氧化菌的甲烷氧化效能，该研究对填埋场温室气体减排、大气污染防治及土体固碳减排具有重要学术意义和实际价值。

Methane oxidation characteristics of biochar-methanotroph amended cover soil in landfill

The landfill cover is the simplest and most feasible method to control methane emissions. Besides its low gas conductivity, methane emissions can be further reduced due to the methane oxidation by soil microbes. However, ordinary soil covers have poor engineering properties, and the methane oxidation efficiency of soil and microbial methane-oxidizing bacteria is low. Biochar is a carbon-rich, black, refractory solid material obtained through pyrolysis of biomass (such as peanut shells, wheat straw, sawdust, and rice straw) under oxygen-limited conditions. Due to its porous structure, high surface area, and pH characteristics, biochar applied to soil can change the microenvironment of the soil, which in turn can affect the efficiency of methane biological oxidation. To investigate the methane oxidation efficiency of biochar-methane oxidizing bacteria modified soil, methane detectors were used to measure the changes in methane reduction rates of both sterile and non-sterile soil samples under different pH levels, methane concentrations, soil dry densities, and biochar dosages. The results showed that when the pH of the inorganic salt culture solution was 7, the methane-oxidizing bacteria had high oxidation efficiency. The methane oxidation curve at pH value 7 is located at the bottom, indicating that the methane oxidizing bacteria have the optimal methane oxidation efficiency in neutral solution (i.e., at pH value 7). When the solution reaches alkaline properties at pH value 9, the methane reduction rate of methane oxidizing bacteria is significantly lower than that at pH value 7. This suggests that the growth, reproduction, and metabolic activity of methane oxidizing bacteria are inhibited in an alkaline environment, leading to a decrease in the efficiency of biological methane oxidation. At a certain initial methane concentration, the oxidation efficiency of methane-oxidizing bacteria increases with the increase of initial methane concentration, but when the initial methane concentration exceeds a certain value, it inhibits the oxidation efficiency of methane-oxidizing bacteria. In the control group experiment without the addition of bacteria, the slope of the curve is close to zero, indicating that the methane emission reduction efficiency is significantly lower in the sterile state compared to the condition with bacteria added. Both the biochar content and dry density affect the methane reduction efficiency of methane-oxidizing bacteria. The methane reduction amplitude with the addition of biochar is greater than that without biochar incorporation. The reason for this is that biochar has a porous structure and low density. When added to the soil, it increases the porosity of the soil and reduces its density, indirectly increasing the physical adsorption capacity of methane. Therefore, the methane reduction rate is more significant. Under the same conditions, the greater the dry density of the sample, the lower the oxidation efficiency of methane. With the increase in biochar content, the methane oxidation efficiency of biochar-methane oxidizing bacteria modified soil gradually increases. When the dry density and biochar content are 1.20 g/cm3 and 15%, respectively, the methane reduction rates under sterile and inoculated conditions show more significant decreases, being 10.38% and 39.72% respectively. This demonstrates that the addition of biochar has altered the microenvironment of the landfill cover soil, enhancing the methane oxidation efficiency of methanotrophs. This research holds significant academic and practical value for reducing greenhouse gas emissions from landfills, preventing air pollution, and promoting soil carbon sequestration.