Conformational changes of humic substances induced by some hydroxy-, keto-, and sulfonic acids

被引:78
作者
Cozzolino, A [1 ]
Conte, P [1 ]
Piccolo, A [1 ]
机构
[1] Univ Naples Federico II, Dipartimento Sci Chim Agr, I-80055 Portici, Italy
关键词
humic substances; supramolecular associations; organic acids; self-assembling conformations; molecular sizes;
D O I
10.1016/S0038-0717(00)00196-6
中图分类号
S15 [土壤学];
学科分类号
0903 ; 090301 ;
摘要
We studied the effect of organic acids of plant, microbial. or anthropic origin on the molecular size distribution of dissolved humic acids (HAs). High Performance Size Exclusion Chromatography (HPSEC) was used to evaluate size changes in four different HAs upon addition of hydroxy- (glycolic and malic), keto- (glyoxylic), and sulfonic (benzenesulfonic and methanesulfonic) acids. All humic substances showed a decrease of peaks absorbance when the pH of HAs dissolved in HPSEC mobile phase was lowered from 7 to 3.5 by acid addition before analysis. This effect, combined with an increase of peaks elution volumes in most cases, was interpreted as a disruption of supramolecular humic associations into smaller-size but energy-richer conformations brought about by the formation of mixed intermolecular hydrogen bonding upon acid treatment. The extent of size variation was related to the pKa of acids and also to the chemical and stereochemical affinity of humic components with the chemical structure of the acids. Dicarboxylic malic acid was the most effective in modifying humic conformations in all HAs whereas the aromatic-rich superstructure of HA from an oxidized coal was effectively disrupted by the relatively small methanesulfonic acid and the chemically akin benzenesulfonic acid. These results suggest that the conformational association of humus dissolved in the soil solution may be systematically altered by organic acids present in the rhizosphere and might have effects on plant and microbial activities. (C) 2001 Elsevier Science Ltd. All rights reserved.
引用
收藏
页码:563 / 571
页数:9
相关论文
共 32 条
[1]  
ALBRECHT OJ, 1991, PLANTS ROOT, P455
[2]  
[Anonymous], PLANT ROOTS HIDDEN H
[3]  
[Anonymous], CH PI INTERACTION EV
[4]  
AUTRY AR, 1990, BIOL FERT SOILS, V10, P50
[5]  
CANTOR CR, 1980, BIOPHYSICAL CHEM 1, P144
[6]   Conformational arrangement of dissolved humic substances. Influence of solution composition on association of humic molecules [J].
Conte, P ;
Piccolo, A .
ENVIRONMENTAL SCIENCE & TECHNOLOGY, 1999, 33 (10) :1682-1690
[7]   High pressure size exclusion chromatography (HPSEC) of humic substances: Molecular sizes, analytical parameters, and column performance [J].
Conte, P ;
Piccolo, A .
CHEMOSPHERE, 1999, 38 (03) :517-528
[8]   Quantitative aspects of solid-state 13C-NMR spectra of humic substances from soils of volcanic systems [J].
Conte, P ;
Piccolo, A ;
Van Lagen, B ;
Buurman, P ;
de Jager, PA .
GEODERMA, 1997, 80 (3-4) :327-338
[9]  
FREIFELDER D, 1982, PHYSICAL BIOCH, P500
[10]   MACROMOLECULAR STRUCTURES OF HUMIC SUBSTANCES [J].
GHOSH, K ;
SCHNITZER, M .
SOIL SCIENCE, 1980, 129 (05) :266-276