珠江三角洲弱透水层―含水层地区的碳循环机理以及二氧化碳和甲烷排放机制的研究

Regional greenhouse gas emission and carbon cycle are important driving forces of regional climate change and have been worldwide hot issues.The study on investigating mechanism of greenhouse gas emission and analyzing the sources of the greenhouse gases should not only consider the greenhouse emission from the river and soil surface, but also investigate the carbon cycle inside the whole system including aquifer, aquitard, vadoze zone and river. A typical region located at the pearl river delta is chose as the study site. Trough insitu measurement and long term monitoring of the greenhouse emission from the river and soil surface, this project aims to clarify the spatial and temporal characteristics of the greenhouse emission.To reveal the mechanisms of the production, transformation, migration and emission of the greenhouse gases in the strata, the chemical composition of groundwater at different depth of the strata was analyzed and monitored through a multi-level monitoring system. In addition to make clear the carbon cycle inside the phreatic aquifer, aquitard, vadose zone and river, this project would also focus on the greenhouse gas transmission between the interfaces between the different aforementioned units (aquitard phreatic aquifers and vadose zone and aquifer, river aquifer, meteoric vadose zone - Atmospheric and river). Finally, a concept model of interface transmission will be established and contribution of greenhouse gas by each unit will be quantified. The research results will provide theoretical and scientific basis for regional energy saving and sustainable development of economy.The exploration of the greenhouse gas emission mechanism and carbon cycle in the formation will also be an important supplement to the global climate change research.

区域温室气体排放和碳循环是区域气候变化的重要驱动因素，因此成为全世界广泛关注的热点问题。研究温室气体排放机制，分析温室气体来源，不能只研究地表水和土壤表面的溢散，应考虑将区域内弱透水层、潜水含水层、包气带及河流等单元作为整体。.本项目拟选取珠江三角洲典型地区为研究对象，通过区域温室气体排放量实测及典型温室气体排放的日夜及季节观测，阐明温室气体天然排放量的空间分布以及时变特征；通过地下多层监测系统采样，揭示温室气体在地层中产生、迁移转化及排放机制；并在探明各单元碳循环机理的基础上，重点探讨各单元界面间（弱透水层-潜水含水层、包气带-潜水含水层、河流-潜水含水层等）的温室气体传输机理和物质传输机制，最终建立界面传输概念模型以及量化各个单元对温室气体排放的贡献。研究结果将为区域节能减排和经济可持续发展提供理论和科学依据。探索地层中碳循环机理以及温室气体排放机制也将是对全球气候变化研究的重要补充。

本项目通过沉积物与水取样、野外实验、数值模拟、遥感分析多学科手段综合评价了珠江三角洲地区弱透水层-含水层系统内地下水系统演化及生物地球化学反应所引起的碳排放含量。定期监测含水层-弱透水层内咸淡水混合的地下水动态、营养盐以及环境同位素的变化规律，评估了系统内地下水系统的演化，预测了三角洲地区所埋藏的盐分量及受海水污染地下水量，评估了海进海退后所遗留的高氨及无机碳含量，对未来的地下水排泄携带入海通量进行了估计。初步评价了地下水流过程的演化，揭示古沉积环境下珠江三角洲系统内的地下水动力学问题。并通过重力卫星数据评估珠江流域长期旱涝特征及其对气候变化的响应。目前正在进行甲烷、二氧化碳气体含量及其同位素的分析工作，以期进一步掌握珠三角地层内的温室气体排放机制。项目组成员目前已参加国际学术会议7人次，发表标注本项目的SCI学术论文3篇。在开展项目期间的4年间，培养博士后2名，博士毕业生4名。项目将利用结余经费进一步开展如下工作：结合实测数据，开展系统的数值模拟，通过耦合复杂溶质运移的反应网络，掌握珠江三角洲地区弱透水层-含水层系统内的碳循环机理。