考虑植被影响时垃圾填埋场生物炭覆盖层水气耦合运移机理与污染调控方法

The landfill cover barriers consisting of vegetation and biocover is the new type of final covers developed in the recent years to reduce the percolation rate and mitigate the landfill gas transport. However, the great majority of the existing studies focus on the investigation of the effect of vegetation on the hydraulic properties of landfill cover soils. The effects of water uptake of vegetation and development of root on the water and gas transport and methane oxidation in the biocovers need further studies. Incubation tests and column tests will be carried out to investigate the mechanisms of landfill gas transport in the biochar amended cover soils considering the effects of water content, gas pressure, temperature and degree of compaction. The modeling and field scale tests will also be carried out to investigate the effects of different types of plant root shapes on methane oxidation rate and water and gas transport properties of biochar amended soils. The determination formulas for gas transport parameters in the biochar amended soils will be proposed considering the effect of vegetation. The coupled model will then be developed to model gas and water transport in the biochar amended cover soils considering the effects of water uptake by the vegetation and the methane oxidation in the covers. On the basis of the proposed coupled model, the effects of different types of plants and biochars, different contents of the biochar, climate conditions on the performance of landfill cover system will be investigated. The results of the project will enrich coupled theory for transport problems in the porous media. The research work will also provide scientific basis for the rational design of landfill final cover systems.

植被生物覆盖层利用植被的蒸腾和生物层的甲烷氧化能力以减少雨水入渗和气体排放，是填埋场封顶系统的发展趋势，但目前研究主要针对植被对覆盖层水力特性方面的研究，植被吸水和根系发展对生物覆盖层水气运移和甲烷氧化的影响机理尚不清楚。本课题拟通过室内培养瓶试验和土柱试验等揭示含水量、气压、温度和压实度等对填埋气在生物炭覆盖层中的运移特性等的影响规律；通过室内模型桶试验结合现场试验研究不同根系形态植被对生物炭覆盖层甲烷氧化能力、水气传导特性的影响机理，提出考虑植被影响的气体运移特性参数计算方法；建立考虑植被蒸腾和根系吸水、甲烷氧化等的填埋气在生物炭覆盖层的水气耦合运移模型，在此基础上分析不同植物类型、生物炭种类和掺量、气候等对覆盖层服役性能的影响规律。本课题的研究成果将完善多孔介质的耦合运移理论，为新型植被生物炭覆盖屏障的优化设计提供科学依据。

我国填埋场覆盖层服役环境复杂，受到填埋场产生的多组分气体、降雨条件、覆盖层的成层性及植被覆盖等因素的共同作用，在多场作用下多组分填埋气在覆盖层中的运移机理是关键科学问题，本项目针对这一关键科学问题，采用室内Batch实验、土柱实验和现场静态箱等方法研究了黄土、生物炭改性黄土和GCL中填埋气的吸附、对流和扩散规律，获得了填埋气在不同覆盖层介质的气相渗透系数、扩散系数和吸附分配系数等重要的填埋气运移有关参数。在此基础上，建立了填埋气在成层覆盖层中的一维运移解析模型、多组分填埋气在覆盖层中的运移数值模型和考虑植被影响的填埋气在覆盖层中的运移数值模型，揭示了覆盖层的非均质性、生物炭改性、多组分气体相互作用和植被根系吸水等对填埋气在覆盖层中运移的影响规律。在西安某大型填埋场和杭州某大型填埋场进行了填埋气释放的静态箱试验，获得了现场尺度的填埋气释放通量及其影响因素，研究了气象条件、植被覆盖情况、覆盖层性质和导气层气体收集效率等对填埋气释放通量的影响。在此基础上采用提出的解析模型和数值模型对临时覆盖层和终场覆盖层的服役性能进行了分析，该研究成果可为填埋场临时覆盖层和终场覆盖层的有效设计提供科学依据。本项目共发表学术论文26篇，其中SCI期刊论文17篇，EI收录论文3篇；授权实用新型专利1项，申请发明专利1项；培养博士生4名，硕士生3名。