不同粒径黄河沉积物中可提取腐殖质的含量分布及光谱特性

Concentration and Spectrum Characteristic of the NaOH Extracted Humic Substances in Three Size Fractions of Sediments from the Yellow River

测定了黄河表层沉积物3种粒径组分（Ⅰ：100-300μm;Ⅱ：63-100μm;Ⅲ：〈63μm）中总有机碳和可提取腐殖质的含量,分析了可提取腐殖质的紫外-可见吸收光谱、红外光谱和三维荧光光谱特征,探讨了不同粒径组分沉积物中可提取腐殖质含量分布及其化学组成特性.结果表明,沉积物有机质主要为粘土矿物吸附的天然腐殖质成分,总有机碳中可提取腐殖质的比例随沉积物有机质与矿物质相互作用的增强而降低,顺序为Ⅰ〉Ⅱ〉Ⅲ.3种粒径组分沉积物中可提取腐殖质的紫外-可见吸收光谱相似但相对峰强不同;红外光谱主要有5个吸收峰,各吸收峰面积百分含量的计算结果表明酚、醇及羧酸类官能团为主要的活性官能团,占可提取腐殖质组成的75%以上;三维荧光光谱主要有3个荧光峰,除了典型的类腐殖质荧光峰（峰A和峰C）外,还有源于小分子类蛋白或酚类物质的荧光峰（峰T′）.比较3种粒径组分沉积物中可提取腐殖质的紫外-可见、红外及三维荧光光谱的特征参数,发现Ⅰ、Ⅱ组分沉积物中可提取腐殖质的芳香度高,脂肪族和芳香族含量高于Ⅲ组分,而Ⅲ组分沉积物可提取腐殖质中酚、醇及羧酸类活性基团含量相对较高.

The concentrations of total organic carbon （TOC） and the NaOH extracted humic substances were analyzed in three size fractions （ Ⅰ：100- 300 μm, Ⅱ： 63 - 100 μm and Ⅲ ： 〈 63 μm） of sediments sampled in the middle Yellow River. Moreover, UV-visible absorption spectra, fourier transform infrared spectra （FUR） and three-dlmensional excitation emission matrix fluorescence spectra （3DEEM） were used to characterize the chemical structures of the NaOH extracted humic substances in three sediment size fractions. The results show that sediment organic matter in all the size fractions of the collected sediments is dominated by humic substances absorbed on the clay minerals. The proportions of the NaOH extracted humic substances to TOC decrease with decreasing sediment grain size （ Ⅰ 〉 H 〉Ⅲ）. This may result from the stronger interaction of the humic substances with clay minerals in finer size fractions of the colleted sediments. Similar UV-visible spectra with different absorbance intensity are observed for the NaOH extracted humic substances in three sediment size fractions. The infrared spectra of the NaOH extracted humic substances show five strong peaks in all fractions of the samples. The area ratios of FTIR peaks suggest that the contents of the phenolic, alcoholic and carboxylic groups account for more than 75% in the NaOH extracted humic substances. Three characteristic excitation-emission peaks present in the 3DEEM of the NaOH extracted humic substances： peak A （UV humic-like compounds）, peak C （visible humic-like compounds） and peak T＇ （phenolic compounds or protein like compounds）. UV-visible, FUR and 3DEEM results imply that the aromatic degree of the NaOH extracted humic substances is higher in fractions Ⅰ and Ⅱthan in fraction Ⅲ. The results also indicate that the aliphatic and aromatic contents are higher in fractions Ⅰand Ⅱ, whilst the phenolic, alcoholic and carboxylic contents are higher in fraction Ⅲ.