Department of Environment and Energy, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea.
Department of Environment and Energy, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea.
Sci Total Environ. 2019 Apr 10;660:169-176. doi: 10.1016/j.scitotenv.2019.01.035. Epub 2019 Jan 6.
In this study, we utilized a size exclusion chromatography (SEC) system that was equipped with a fluorescence emission scanning mode to explore the heterogeneous distribution of the humification index (HIX) values within bulk dissolved organic matter (DOM). The HIX-based SEC chromatograms showed that the molecular weight (MW)-dependent distribution of aromatic condensation was heavily affected by the DOM sources and the progress of biodegradation. The HIX heterogeneity across different MW was more pronounced for terrestrial versus aquatic DOM sources. Microbial incubation of leaf litter DOM led to the initial enhancement of the HIX at a relatively low MW, followed by a gradual increase at larger MW values. The dynamic changes of the HIX can be attributed to (1) the preferential removal of non-aromatic or less-aromatic molecules by microorganisms, (2) the production of microbial metabolites, (3) microbial humification, and (4) self-assemblage of humic-like molecules. From the SEC chromatograms, the HIX-based average molecular weight (or MW) was proposed as a unifying surrogate to represent an MW that was highly associated with aromatic condensation. The MW discriminated four different DOM sources and described well the biodegradation-induced changes. The MW also presented a good positive correlation with pyrene organic carbon-normalized binding coefficients (K). The prediction capability of the MW for pyrene K was higher than those based on the single descriptors of bulk DOM, such as HIX and MW, which revealed its superior linkage with the DOM reactivity related to both MW and HIX.
在本研究中，我们利用配备荧光发射扫描模式的排阻色谱（SEC）系统来探究腐殖化指数（HIX）值在整体溶解有机质（DOM）内的非均相分布。基于 HIX 的 SEC 色谱图表明，芳香缩合的分子量（MW）依赖性分布受到 DOM 来源和生物降解进程的强烈影响。与水生 DOM 来源相比，陆地 DOM 来源的不同 MW 之间的 HIX 非均质性更为显著。落叶凋落物 DOM 的微生物培养导致在相对较低的 MW 处最初增强 HIX，随后在较大 MW 值处逐渐增加。HIX 的动态变化可归因于：（1）微生物优先去除非芳香或低芳香分子；（2）微生物代谢产物的产生；（3）微生物腐殖化；和（4）类腐殖质分子的自组装。从 SEC 色谱图中，我们提出了基于 HIX 的平均分子量（或 MW）作为一个统一的替代物，以代表与芳香缩合高度相关的 MW。MW 区分了四种不同的 DOM 来源，并很好地描述了生物降解诱导的变化。MW 还与芘有机碳归一化结合系数（K）呈良好的正相关。MW 对芘 K 的预测能力高于基于 DOM 整体的单一描述符（如 HIX 和 MW），这表明其与与 MW 和 HIX 都相关的 DOM 反应性具有更好的联系。
