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首页> 外文期刊>The Science of the Total Environment >Monitoring changes in the structure and properties of humic substances following ozonation using UV-Vis, FTIR and ~1H NMR techniques
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Monitoring changes in the structure and properties of humic substances following ozonation using UV-Vis, FTIR and ~1H NMR techniques

机译：使用UV-Vis，FTIR和〜1H NMR技术监测臭氧化后腐殖质的结构和性质变化

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The main objective of this work is to conduct a comprehensive structural characterization of humic substances using the following experimental techniques: FTIR, ~1H NMR and several UV-Vis parameters (Specific UV Absor-bance at 254 nm or SUVA_(254), SUVA_(280), A_(400) the absorbance ratios A_(210/254). A_(250/365), A_(254/203). A_(254/436). A_(255/465). A_(270/400). A_(280/350). A_(465/665). the Absorbance Slope Index (ASI), the spectral slopes S_(375-295). S_(350-400) and the slope ratio S_R). These UV-Vis parameters have also been correlated with key properties of humic substances such as aromaticity, molecular weight (MW) and trihalomethane formation potential (THMFP). An additional objective of this work is also to evaluate the usefulness of these techniques to monitor structural changes in humic substances produced by the ozonation treatment Four humic substances were studied in this work: three of them were provided by the International Humic Substances Society (Suwannee River Fulvic Acid Standard: SRFA, Su-wannee River Humic Acid Standard: SRHA and Nordic Reservoir Fulvic Acid Reference: NLFA) and the other one was a terrestrial humic acid widely used as a surrogate for aquatic humic substances in various studies (Aldrich Humic Acid: AHA). The UV-Vis parameters showing the best correlations with aromaticity in this study were SUVA_(254), SUVA_(280), A_(280/A350) ratio and A_(250)/A_(364) ratio. The best correlations with molecular weight were for SUVA_(254), SUVA_(280) and A_(280)/A_(350) ratio. Finally, in the case of the THMFP it was STHMFP-per mol HS the parameter showing good correlations with most of the UV-Vis parameters studied (especially with A_(280/A_(350) ratio. A_(265)/ A_(465) ratio and A_(270)/A_(400) ratio) whereas STHMFP-per mg C showed poor correlations in most cases. On the whole, the UV-Vis parameter showing the best results was A_(280)/A_(350) ratio as it showed excellent correlations for the three properties studied (aromaticity, MW and THMFP). A decrease in aromaticity following ozonation of humic substances can be readily monitored by ~1H NMR and FTIR; the latter technique also allows to monitor an increase in carboxylic acidity with ozone dosage. This organic matter originated following ozonation (more aliphatic in character and more polar) is expected to be recalcitrant to further oxidation. The terrestrial humic acid (AHA) showed some structural differences with the aquatic humic substances and its behavior upon ozonation also differed in some extent from that shown by them.
机译：这项工作的主要目的是使用以下实验技术对腐殖质进行全面的结构表征：FTIR，〜1H NMR和几个UV-Vis参数（254 nm处的特定UV吸收率或SUVA_（254），SUVA_（ 280），A_（400），吸光度比A_（210/254），A_（250/365），A_（254/203），A_（254/436），A_（255/465），A_（270/400） ）.A_（280/350）.A_（465/665）。吸光度斜率指数（ASI），光谱斜率S_（375-295）.S_（350-400）和斜率S_R）。这些UV-Vis参数还与腐殖质的关键特性（例如芳香性，分子量（MW）和三卤甲烷形成势（THMFP））相关。这项工作的另一个目标是评估这些技术对监测臭氧处理产生的腐殖质结构变化的有效性，研究了四种腐殖质：其中三种是国际腐殖质协会（Suwannee River）提供的。黄腐酸标准品：SRFA，苏-旺尼河腐植酸标准品：SRHA和北欧水库黄腐酸参考品：NLFA），另一种是陆生腐殖酸，在各种研究中被广泛用作水生腐殖质的替代品（Aldrich Humic Acid： AHA）。在本研究中显示出与芳香性最佳相关性的UV-Vis参数为SUVA_（254），SUVA_（280），A_（280 / A350）比和A_（250）/ A_（364）比。与分子量的最佳相关性是SUVA_（254），SUVA_（280）和A_（280）/ A_（350）的比率。最后，在THMFP情况下为STHMFP / mol HS，该参数与研究的大多数UV-Vis参数显示出良好的相关性（尤其是与A_（280 / A_（350）比率。A_（265）/ A_（465）） ）比率和A_（270）/ A_（400）比率），而STHMFP / mg C在大多数情况下显示出较弱的相关性，总体而言，显示最佳结果的UV-Vis参数为A_（280）/ A_（350）由于它显示出与所研究的三个特性（芳香性，MW和THMFP）极好的相关性，因此可以通过〜1H NMR和FTIR容易地监测到腐殖质臭氧化后芳香性的降低；后一种技术还可以监测羧基的增加酸度与臭氧剂量。臭氧化后产生的有机物（特性更多的脂肪族和极性更多）预计将阻碍进一步的氧化。腐殖酸（AHA）与水生腐殖质在臭氧化后表现出一些结构差异在某种程度上也有所不同从他们所展示的。

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