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Size and shape of humic acid molecules by surface pressure-area isotherms at the air-water interface

空气-水界面处的表面压力面积等温线显示的腐植酸分子的大小和形状

基本信息

批准号：
03804044
负责人：
HAYASE Kohji
金额：
$ 1.22万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-03804044/
关键词：
Humic acid Monolayer Surface pressure-area isotherm Size of molecule Limiting Specific area Brown forest soil Volcanic ash soil Molecular fractionation 表面圧一面線曲線絶対値測定表面圧表面膜

项目摘要

Three humic acids (HAs) were extracted from volcanic ash soil at Shizuoka, brown forest soil at Aichi and sediment of Tokyo Bay. Sedimentary HA was fractionated into five molecular weight ranges. Surface pressure-area measurements were carried out on brown forest soil, volcanic ash soil and sedimentary HAs at an air-water interface. Surface pressure-area curves of the HAs exhibited a typical monolayer characteristic at the air-water interface. Limiting specific area of the sedimentary HAs decreased with the increase in molecular weight. A length of the sedimentary HAs was calculated as 3.1-8.7 nm and carbon number of the length was 23-67 from the lower molecular weight Ga to the higher one. A length of the brown forest soil and volcanic ash soil HAs were 3.8 and 12.1nm,respectively. Carbon number for the brown forest soil and volcanic ash soil HAs were 29 and 93, respectively. Size of the volcanic ash soil HA is appeared to be highly larger than the brown forest soil HA.Then, HA is found to be a linear but not a spherical structure. Because, if such the thickness is a radius of a sphere, volume of the HA will become extremely high comparing to the molecular weight of the HA. These estimated values (thickness) are considered to be ascribed to a length of the molecule of HA, whose structure is a rod or linear shape.Since there is no actual model compounds for HA, only relatively determined size has been known for HA. In this study, however, it is noteworthy that a length of the HAs was determined directly and absolutely. It will be continued to carry out the direct size determination of many kinds of HA macromolecules for the promotion of the chemical characterization of humic substances.

从静冈火山灰土、爱知棕色森林土和东京湾沉积物中提取了三种腐殖酸。沉积HA被分馏成五个分子量范围。在大气-水界面上，对棕色森林土、火山灰土和沉积性腐殖土进行了表面压力-面积测量。表面压力-面积曲线的HA在空气-水界面处表现出典型的单分子层特性。随着分子量的增加，沉积型腐殖酸的极限比表面积逐渐减小。计算出沉积的HAs的长度为3.1- 8.7nm，从低分子量Ga到高分子量Ga的长度的碳数为23-67。棕色森林土和火山灰土的HA长度分别为3.8和12.1nm。棕色森林土和火山灰土HA的碳数分别为29和93。火山灰土HA的粒径明显大于棕色森林土HA，HA呈线状结构，而非球状结构。因为，如果这种厚度是球体的半径，则HA的体积与HA的分子量相比将变得非常高。这些估计值（厚度）被认为是归因于HA分子的长度，其结构是棒状或线状的。然而，在这项研究中，值得注意的是，HA的长度是直接和绝对确定的。今后将继续开展多种HA大分子的直接粒度测定，以促进腐殖物质的化学表征。