Different mechanisms driving the preferential adsorption of dissolved organic matter by goethite and montmorillonite
Different mechanisms driving the preferential adsorption of dissolved organic matter by goethite and montmorillonite
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DOI：
10.1016/j.chemgeo.2021.120560
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发表时间：
2021-10
期刊：
影响因子：
3.9
通讯作者：
Lanfang Han;Yan Yang;Ke Sun;Biao Zhang;Yalan Chen;L. Fang;B. Xing
中科院分区：
文献类型：
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作者：
Lanfang Han;Yan Yang;Ke Sun;Biao Zhang;Yalan Chen;L. Fang;B. Xing
溶解有机物（DOM）在矿物-水界面的分子分馏决定了其在陆地和水生环境中的地球化学过程中的作用。然而，页硅酸盐上的DOM吸附分馏缺乏分子尺度的调查。此外，DOM在典型矿物表面的吸附分馏机制尚不清楚。采用超高分辨质谱、传统光谱法和不同背景电解质（CaCl 2、NaCl和NaCl-NaH 2 PO 4），研究了典型层状硅酸盐（蒙脱石）和羟基氧化铁（针铁矿）对DOM的分子分馏作用，为DOM吸附分馏的具体驱动机制提供了直接和定量的证据。Montreal选择性吸附相对较低的分子量（MW）和高O/C的成分具有脂肪族部分（主要是蛋白质和碳水化合物样的物种）或一个苯环作为第一次确定使用一个新的芳香性当量。这种结构偏好在“Ca ~（2+）桥连”反应贡献较大（45.6-76.0%）的吸附体系中更为显著。针铁矿则优先稳定含稠环数≥3的芳烃和高O/C的高分子量组分，这在“配体交换”机制占主导地位的体系中尤为明显（55.5-71.4%）。对于蒙脱石和针铁矿，当货车德瓦耳斯占主导地位时，检测到DOM的非选择性吸附。这些研究结果将促进对DOM在环境中的生态地球化学过程的机制的理解。
Molecular fractionation of dissolved organic matter (DOM) at the mineral-water interface governs its role in biogeochemical processes in both terrestrial and aquatic environments. However, adsorptive fractionation of DOM onto phyllosilicates lacks molecular-scale investigation. Moreover, the mechanisms driving DOM adsorptive fractionation onto typical mineral surface remains unknown. Using ultra-high resolution mass spectrometry, traditional spectroscopic method, and different background electrolytes (CaCl2, NaCl and NaCl-NaH2PO4), we investigated the molecular fractionation of DOM by typical phyllosilicate (montmorillonite) and iron oxyhydroxide (goethite) and provided direct and quantitative evidence for the specific driving mechanisms for the adsorptive fractionation. Montmorillonite selectively adsorbed the comparatively low molecular weight (MW) and high O/C constituents having aliphatic moieties (mainly protein- and carbohydrate-like species) or one benzene ring as first identified using a new aromaticity equivalent. This structural preference was more remarkable in the adsorption system with large contribution of “Ca2+bridging” reaction (45.6–76.0%). By contrast, goethite preferentially stabilized the constituents with high MW components containing aromatics with ≥3 condensed benzene rings and high O/C, which was notable in the system where “ligand exchange” mechanism predominated (55.5–71.4%). For both montmorillonite and goethite, non-selective adsorption of DOM was detected when van der Waals dominated. These findings would advance the mechanistic understanding of biogeochemical processes of DOM in the environments.