Department of Soil and Water Sciences, the Hebrew University of Jerusalem, Israel.
J Environ Qual. 2012 Mar-Apr;41(2):526-33. doi: 10.2134/jeq2011.0362.
Interactions of dissolved organic matter (DOM) with soil minerals, such as metal oxides and clays, involve various sorption mechanisms and may lead to sorptive fractionation of certain organic moieties. While sorption of DOM to soil minerals typically involves a degree of irreversibility, it is unclear which structural components of DOM correspond to the irreversibly bound fraction and which factors may be considered determinants. To assist in elucidating that, the current study aimed at investigating fractionation of DOM during sorption and desorption processes in soil. Batch DOM sorption and desorption experiments were conducted with organic matter poor, alkaline soils. Fourier-transform infrared (FTIR) and UV-Vis spectroscopy were used to analyze bulk DOM, sorbed DOM, and desorbed DOM fractions. Sorptive fractionation resulted mainly from the preferential uptake of aromatic, carboxylic, and phenolic moieties of DOM. Soil metal-oxide content positively affected DOM sorption and binding of some specific carboxylate and phenolate functional groups. Desorptive fractionation of DOM was expressed by the irreversible-binding nature of some carboxylic moieties, whereas other bound carboxylic moieties were readily desorbed. Inner-sphere, as opposed to outer-sphere, ligand-exchange complexation mechanisms may be responsible for these irreversible, as opposed to reversible, interactions, respectively. The interaction of aliphatic DOM constituents with soil, presumably through weak van der Waals forces, was minor and increased with increasing proportion of clay minerals in the soil. Revealing the nature of DOM-fractionation processes is of great importance to understanding carbon stabilization mechanisms in soils, as well as the overall fate of contaminants that might be associated with DOM.
溶解有机质 (DOM) 与土壤矿物质（如金属氧化物和粘土）的相互作用涉及各种吸附机制，并可能导致某些有机部分的吸附分馏。虽然 DOM 对土壤矿物质的吸附通常具有一定程度的不可逆性，但尚不清楚 DOM 的哪些结构成分对应于不可逆结合部分，以及哪些因素可以被认为是决定因素。为了阐明这一点，本研究旨在研究 DOM 在土壤吸附和解吸过程中的分馏。采用有机质含量低、碱性土壤进行了 DOM 批量吸附和解吸实验。傅里叶变换红外（FTIR）和紫外-可见光谱用于分析 bulk DOM、吸附 DOM 和解吸 DOM 馏分。吸附分馏主要是由于 DOM 中芳香族、羧酸和酚类部分的优先吸收。土壤金属氧化物含量对 DOM 的吸附和一些特定的羧酸盐和酚盐官能团的结合有积极影响。DOM 的解吸分馏表现为一些羧酸部分的不可逆结合性质，而其他结合的羧酸部分则容易解吸。内配位（相对于外配位）配体交换络合机制可能分别负责这些不可逆和可逆相互作用。与土壤中芳香族 DOM 成分的相互作用，可能是通过弱范德华力进行的，作用较小，但随着土壤中粘土矿物比例的增加而增加。揭示 DOM 分馏过程的性质对于理解土壤中碳稳定机制以及与 DOM 相关的污染物的整体归宿具有重要意义。
