Adsorption of humic acid to interlamellar surfaces of montmorillonite

土壤是世界上最大的陆地有机碳库，几乎是陆地生物碳库的3倍，是大气碳库的两倍多。尽管土壤有机碳(SOC)储量巨大，但仍有相当大的潜力进一步增加SOC，特别是在受管理的生态系统中，SOC的固存速度估计高达每年12亿吨。这些SOC的增加被提议作为抵消温室气体排放的一种手段，从而帮助实现《京都议定书》中确立的目标。在SOC可被固定到的各种组分中，只有平均停留时间超过1000年的被动库具有足够的稳定性，可以作为有机C的长期储存库。因此，有机C在这个耐火库中的放置仍然是所有综合固碳策略的目标。其中最顽固的有机分子是腐植酸，如腐植酸和黄腐酸。当这些材料被强烈吸附到矿物表面时，它们特别耐降解。因此，矿物型腐殖质是稳定的SOC储集层的重要组成部分。这项研究的目的是确定腐植酸是如何吸附到蒙脱石的内表面上的，蒙脱石是一种常见的土壤矿物。我们将检验这一假设，即某些天然有机分子具有长的饱和碳氢链，并结合到蒙脱石边缘，作为腐植酸的附着点，从而将这种有机分子定位在走廊入口处附近，从而促进层间吸附。我们的数据将揭示腐殖质通过膨胀层硅酸盐而成为插层物质的机制，从而有助于稳定的SOC池。这项研究还将为全球土壤碳管理战略提供信息，指导那些长期有机碳储存最受欢迎的土壤的碳固存工作。

The world's soils are the largest repository of terrestrial organic carbon, nearly 3 times larger than the terrestrial biotic C pool, and more than twice the size of the atmospheric C pool. Despite the magnitude of the soil organic carbon (SOC) reservoir, there is considerable potential for further SOC additions, especially in managed ecosystems, with rates of SOC sequestration estimated to be as high as 1.2 Gigatons per year. These SOC additions have been proposed as a means to offset greenhouse gas emissions, thereby helping to achieve targets established within the Kyoto Protocol. Among the various fractions to which SOC may be sequestered, only the passive pool, with mean residence times in excess of 1,000 years, has sufficient stability to serve as a suitable long-term store of organic C. Placement of organic C in this refractory pool therefore remains the aim of all comprehensive C sequestration strategies. Among the most recalcitrant organic molecules are the humic substances, such as humic acid and fulvic acid. These materials are particularly resistant to degradation when they are strongly adsorbed to mineral surfaces. Thus, mineral-complexed humic materials are an important and desirable component of the stable SOC reservoir. The aim of this investigation is to determine how humic acid becomes adsorbed to the internal surfaces of montmorillonite, a common soil mineral. We will test the hypothesis that a certain group of natural organic molecules, possessing long saturated hydrocarbon chains and bound to montmorillonite edges, serve as attachment points for the humic acid, thus positioning this organic molecule near the gallery entrance and so facilitating interlamellar adsorption. Our data will reveal the mechanisms through which humic materials become intercalated by expanding layer silicates, contributing to the stable SOC pool. This research will also inform global soil C management strategies, guiding C sequestration efforts to those soils in which long-term organic C storage is most favoured.