阴离子界面反应的量子机制及其对土壤胶体凝聚的影响

Aggregation of soil colloids occurs spontaneously with variation of the environmental thermodynamic conditions, and has a great influence on the properties, fertility and ecological function of soil. As is known to us, the surface of soil colloids are usually negatively charged, the aggregation of soil colloids is therefore dominated by the electrolyte cations dominance, showing strong specific ion effects. The electrolyte anions, however, would be repelled from surface due to the repulsion forces; as a result, the effect of anions on the soil colloids aggregation is generally ignored. Actually, studies have shown that, due to anion specific effect, the anions can significantly affect ion distribution on negatively charged colloids, bio-membrane formation, protein-protein interactions and DNA enzyme efficiency etc. Therefore, experimental studies on the specific anion effects on surface electrochemical properties of soil colloids, aggregation kinetics, as well as morphology and structure characteristics of aggregates, combined with the theoretical determinations of the interaction forces between colloidal particles and computer simulations of ions/colloids/ water interaction based on quantum chemistry will be carried out in this project. On the basis of these researches, the strength of specific anion effects and the intensity of ions/colloids/ water interaction will be quantitatively characterized, and then the quantum mechanism of anion interface interactions and the mechanism of soil colloid aggregation taking into consideration of specific anion effects will be systematically interpreted.

土壤胶体的凝聚随环境热力学条件的改变自发进行，并在很大程度上影响着土壤的性质、肥力和生态功能。土壤胶体表面带净的负电荷，其凝聚过程由电解质中阳离子支配，表现出强烈的离子特异性效应的影响；而电解质中阴离子会受到胶体表面负电荷的排斥，一般忽略其对土壤胶体凝聚的可能影响。事实上，已有研究表明，由于阴离子特异性效应的存在，阴离子会显著影响到带负电荷胶体表面的离子分布、生物膜的形成、蛋白质相互作用及DNA酶切效率等。因此，本项目将开展阴离子特异性效应作用下土壤胶体表面电化学性质、凝聚动力学过程及凝聚体形貌和结构特征的实验研究，结合土壤胶体颗粒间相互作用力的测定以及基于量子化学的离子/胶体/水相互作用的计算机模拟研究，以期阐明土壤胶体凝聚中阴离子特异性效应；通过定量表征阴离子特异性效应的强度、离子/胶体/水相互作用能的强度，系统解释阴离子界面反应的量子机制和基于阴离子特异性效应的土壤胶体凝聚机制。

土壤胶体的凝聚随环境热力学条件的改变自发进行，并在很大程度上影响着土壤的性质、肥力和生态功能。土壤胶体表面带净的负电荷，其凝聚过程由电解质中阳离子支配，表现出强烈的离子特异性效应的影响；而电解质中阴离子会受到胶体表面负电荷的排斥，一般忽略其对土壤胶体凝聚的可能影响。事实上，已有研究表明，由于阴离子特异性效应的存在，阴离子会显著影响到带负电荷胶体表面的离子分布、生物膜的形成、蛋白质相互作用及DNA酶切效率等。因此，本项目通过开展阴离子特异性效应作用下土壤胶体表面电化学性质、凝聚动力学过程及凝聚体形貌和结构特征的实验研究，结合土壤胶体颗粒间相互作用力的测定以及基于量子化学的离子/胶体/水相互作用的计算机模拟研究，取得了如下研究结果：明确了阴离子特异性效应会显著影响带负电荷胶体的凝聚，研究表明几种阴离子核外电子云结构的差异带来的显著不同的极化效应是其本质原因，这一研究意味着我们要重视阴离子对负电荷胶体表面性质及相互作用的影响，而传统土壤学长期以来忽略了阴离子的研究；提出了土壤胶体表面电荷与吸附态离子形成的电场可能是土壤胶体凝聚中离子特异性效应的内在作用力；建立了描述可变电荷胶体凝聚过程的新理论，这一理论可用来理论预测胶体凝聚速率与溶液温度、电解质浓度、pH、颗粒大小、表面电荷密度等的关系。基于这一理论，我们在基于动态光散射测定可变电荷胶体颗粒PZC和胶体颗粒的Hamaker常数的分析方法上取得进展；通过对离子-界面相互作用的研究，明确了离子特异性效应对胶体颗粒表面性质、表面吸附平衡状态以及吸附活化能的影响。