矿物改性生物炭在土壤中的降解特征和激发效应

As a promising tool for carbon sequestration, biochar has been paid extensive attention. It is being increasingly recognized that application of biochar into soil can be an effective way for mitigating global climate change. Therefore, it is of practical significance to create biochar with high carbon retention and strong stability for long-term carbon sequestration. Researches showed that mineral modification played a positive role on improving functional characteristics of biochar, such as increasing the adsorption capacity. However, stability of mineral modified biochar and its degradation characteristic and priming effect in soils have rarely been reported at present. In this study, vermiculite and rice straw was chosed to produce modified biochar at different carbonization temperatures. The stability of both modified and unmodified biochar will be systematically evaluated through thermogravimetric analysis, elemental analysis, chemical oxidation experiment. The interaction between mineral constituent and carbon, and the relative proportion changes of carbon in each chemical functional group will be detected for biochar before and after modifying treatment by X-ray diffraction and cross-polarization magic angle spinning 13C nuclear magnetic resonance spectra analysis. A constant temperature incubation experiment will be carried out in laboratory to study the biotic and abiotic oxidative degradation dynamic characteristics of modified biochar in two typical soils in Zhejiang province. Half-life period of biochar will be scientifically calculated according to the result of this experiment. Furthermore, priming effect of biochar on the mineralization of native soil organic carbon will be investigated. Finally, the regulatory mechanism of mineral modified biochar for carbon sequestration in the soil will be clarified.

生物炭作为极具固碳潜力的新兴技术受到越来越广泛的关注，生物质炭化还田有望成为人类应对全球气候变化的有效途径。开发碳持留率高和稳定性强的生物炭对于长期持续发挥其固碳效应具有重要的现实意义。研究表明，矿物改性对提高生物炭吸附能力、优化生物炭功能特性具有积极作用，但目前关于矿物改性生物炭稳定性及其在土壤中的降解特征和激发效应的研究鲜见报道。本项目拟选用蛭石和水稻秸秆在系列炭化温度条件下制备矿物改性生物炭，通过热重分析、元素分析和化学氧化等实验手段，研究蛭石改性对生物炭自身稳定性的影响，并通过XRD和NMR分析，揭示改性前后生物炭无机矿物组分和不同碳素形态分布等变化情况；通过室内恒温培养试验，模拟研究改性生物炭在浙江两种典型类型土壤中的生物与非生物氧化降解动力学特征，科学测算生物炭降解半衰期，并探索改性生物炭对土壤有机碳矿化的激发效应，阐明矿物改性对生物炭发挥其土壤固碳减排作用的影响及调控机制。

生物炭作为极具固碳潜力的新兴材料受到越来越广泛的关注，生物质炭化还田有望成为人类应对全球气候变化的有效途径。开发碳持留率高和稳定性强的生物炭对于长期持续发挥其固碳效应具有重要的现实意义。矿物改性对优化生物炭功能特性具有积极作用，但目前关于矿物改性生物炭稳定性及其在土壤中的降解特征和激发效应的研究鲜见报道。本项目以水稻秸秆和蛭石为原材料和改性材料，在系列炭化温度（300-700℃）条件下制备生物炭，采用热重分析、红外光谱、核磁共振等技术手段，阐明了蛭石改性对生物炭稳定性的影响及机制；通过室内恒温培养实验，研究不同水分条件下改性生物炭在浙江典型土壤中的短期降解特征；结合稳定同位素标记技术，探索改性生物炭对土壤有机碳（SOC）矿化的激发效应。结果表明：1）生物炭的产率和碳素持留率均随炭化温度的升高而降低，经蛭石改性处理后分别提高13.5%-38.8%和5.2%-22.1%。生物炭的碳素热失重率、H/C原子比和碳素氧化损失率均随炭化温度的升高而逐渐降低，说明其热化学稳定性逐渐增强。改性处理通过增加总矿物尤其是Fe、Al、Mg、Si等矿物组分含量，促进或增强生物炭表面Si–O–C、Fe–O等化学键的形成，提高炭化过程中芳构化反应速率（即由烷基碳和羰基碳向芳香碳的转化），从而增强生物炭的热化学稳定性。2）与水分条件相比，土壤类型对生物炭稳定性的影响更大；与水稻土相比，无论炭化温度高低和改性与否，生物炭在红壤中的稳定性更强。3）对于红壤，低温生物炭（300℃）促进SOC矿化，表现为正激发效应；高温生物炭（700℃）抑制SOC矿化，表现为负激发效应；培养时间延长、炭化温度升高和蛭石改性均使激发效应朝负向移动。对于水稻土，不同温度生物炭对SOC矿化均起到负激发效应，强度高低表现为500℃>700℃>300℃。正激发效应是由于生物炭中溶解性有机碳含量越高，其引发的微生物共代谢作用越强，进而促进SOC矿化；而负激发效应主要受到生物炭孔隙结构的影响，比表面积和总孔容越大，其对SOC的包封和吸附保护作用越强，进而抑制SOC矿化。本研究为功能改性生物炭的研发及其在固碳减排方面的应用提供了科学依据和技术支撑。