南方可变电荷土壤铁循环缓冲土壤酸化的微观化学机制

可变电荷土壤广泛分布于我国长江以南地区，其理化特性显著差异于欧洲及北美的恒电荷土壤。剧烈的人为活动导致华南地区土壤的加速酸化，严重威胁生态系统的稳定性和资源的高效利用。华南地区土壤中氧化铁的含量高、活性大，氧化铁铝取代是其典型成土特征，影响土壤致酸源离子的反应活性，因而具备缓冲土壤酸化的潜力。本项目以土壤典型铝取代氧化铁为模型矿物，以铁循环缓冲土壤酸化的微观化学机制为研究核心科学问题，综合运用同步辐射结合矿物表面物理化学、结构化学的研究方法，研究主要包括：氧化铁抑制活性致酸源水解产酸的主控因子及其调控机制；影响典型可变电荷土壤酸碱缓冲能力大小的特征理化因子；土壤次生矿物组成、氧化铁铝取代特征与土壤pH变化的年际关系；氧化铁铝取代效应缓冲土壤酸化的微观化学机制；调控可变电荷土壤酸碱缓冲能力的微观矿物学响应机制。预期成果可为解析红壤酸化的关键过程和驱动因子，研发相应调控技术提供科学依据。

The variable charge soils that have been developed in tropical and subtropical zones are unique soils compared with the constant charge soils that have been developed in Europe and North America, especially the sensitivity of the particle surface charges to environmental factors in the variable charge soils. Soil acidification is a natural process, and it is well known that soil acidification can be accelerated by certain human activities. Ferrosols is a special soil orders in Chinese Soil Taxonomic Classification, which contain a large amount of amorphous iron (hydr)oxides (IOx) and is widely distributed in China, especially in tropical and subtropical zones in Southern China, which are belonging to the variable charge soils. In these areas, Al-substituted IOx is one of the most important feature under the effect of soil desilicification and allitization; and the isomorphous substitution of Al for Fe in the IOx crystal structures influence the activity of Al3+ (potential acid) and H+ (activated acid) in soils, which are two important cations responsible for soil acidification, further illustrate the buffering abilities of soil iron redox cycles on soil acidification. Nevertheless, how this acidification occurs and how the mineralogies of iron oxides as the important active clay components in variable charge soil respond to the acidification is still less understood. This proposal will choose various synthesized Al-substituted IOx as the research model objects, and the main target of this proposal is set up to investigate the chemical mechanism of soil iron redox cycles on buffering soil acidification in the variable charge soils. Synchrotron radiation cooperated with various advanced analysis methods will be applied in the experiments of this proposal, whereas experiments are designed and conducted to investigate the chemical mechanism of Al-substituted IOx on the reactivity of acidification cations. In detail, (1) to study the impact of iron oxides on the activities of Al3+ (potential acid) and H+ (activated acid) in soils and their influence factors; (2) to figure out these key factors on controlling the variable charge soils’ acidification buffering capacities; (3) to investigate the interannual relations among the components of soil second minerals, the characteristics of Al-substituted IOx and soil acidification trend; (4) to illustrate the chemical mechanism of Al-substituted IOx on buffering soil acidification; and (5) to find the mineralogical response mechanism of regulating acid-base buffer capacity of variable charge soil. The expected results can provide a scientific basis for the analysis of key processes and driving factors of red soil acidification, as well as the development of corresponding control technologies.