摘要
土壤腐殖质颗粒与金属离子间的相互作用深刻地影响着土壤中的微观过程和宏观现象的发生。而胡敏酸是土壤腐殖质的主要组成物质,本文利用光散射技术研究了不同浓度的Ca(NO3)2和Cu(NO3)2溶液中胡敏酸胶体颗粒的凝聚过程和形成凝聚体的结构,并在此基础上进行比较分析。结果表明:由于Ca2+和Cu2+在带电胶体表面的吸附方式不同而对胡敏酸胶体的凝聚的影响表现出很大差异。(1)散射光强的稳定与否可以反映体系的稳定性,Ca(NO3)2体系中散射光强可以在较宽的电解质浓度范围从0 mmol L-1至20 mmol L-1内保持稳定,而Cu(NO3)2体系中光强稳定的电解质浓度范围较窄,只有0 mmol L-1至3 mmol L-1。(2)随电解质浓度的提高,两种电解质体系中凝聚体的有效粒径随时间先呈线性增长再呈幂函数增长,但胡敏酸胶体凝聚过程对Cu(NO3)2体系浓度变化的敏感性远大于Ca(NO3)2体系,并且1 mmol L-1Cu2+吸附下胡敏酸胶体的凝聚速率为69.55 nm min-1,近乎是7.5 mmol L-1Ca2+吸附下凝聚速率23.94 nm min-1的3倍,可见Cu2+作用下颗粒的平均凝聚速率远远高于Ca2+作用的情况。(3)Ca(NO3)2体系中,电解质浓度越高形成凝聚体的结构越开放,但放置50 d后分形维数变小,结构变得更加疏松,说明该凝聚过程具有可逆性;而Cu2+作用下形成的凝聚体初期结构开放度较高,在放置50 d后分形维数变大,结构更加致密紧实,说明该凝聚过程具有不可逆性。这些信息为研究腐殖质超分子聚合物的形成机制提供了新思路。
The interactions between humus particles and metal ions profoundly affect occurrence of some soil micro- and macro-phenomena. As humic acid is the main component of soil humus, process of the aggregation of humic colloidal particles and structure of the resultant aggregates as affected by concentrations of Ca（ NO3 ）2 and Cu （NO3 ）2 in the solution was studied for comparison analysis in this research project using the light scattering technique. Results show that the difference between Ca（ NO3 ）2 and Cu（ NO3 ）2 in adsorption to the surface of charged colloids greatly affected aggregation of humic colloids. The stability of scattered light intensity reflected stability of the system. Scattered light intensity could remain steady in the Ca（NO3）2 system with the electrolyte varying in a wide range from 0 mmol L^-1 to 20 mmol L^-1 in concentration, but in the Cu（ NO3 ）2 system, the range was much narrower, from 0 mmol L^-1 to 3 mmol L^-1 only. In the two electrolyte systems, with rising electrolyte concentration, effective diameter of the humic aggregates increased linearly first and then as a power function of time, but the process of humic aggregation is much more sensitive to the variation of Cu （NO3 ） 2 concentration than to that of Ca （NO3 ） 2 concentration. The mean aggregation rate of humus colloids in the solution of 1 mmol L^-1 Cu^2＋ reached 69.55 nm min ^-1 , which is nearly 3 times as high as that （23.94 nm min ^-1 ） in the solution of 7.5 mmol L^-1 Ca^2＋. Obviously the mean aggregation rate is much higher under the action of Cu^2＋ than under the action of Ca^2＋. In the Ca（ NO3 ）2 system, the higher the electrolyte concentration, the more open, the structure of the resultant aggregates, which became more open or loose in structure and smaller in fractal dimension after being set aside for 50 days, suggesting that the aggregation process is reversible. However, in the Cu （NO3）2 system, the aggregates formed under the action of Cu^2＋ were quite open in structure at their initial stage, but they became higher in fractal dimension and more compact in structure after being set aside for 50 days, suggesting that the aggregation process is irreversible. All the findings provide a new way of thinking for understanding the mechanism of the formation of humic supermolecular aggregates.
出处
《土壤学报》
CAS
CSCD
北大核心
2012年第4期698-707,共10页
Acta Pedologica Sinica
基金
国家自然科学基金项目(40971196)
博士点基金课题(20090182110017)
西南大学研究生科技创新基金项目(Ky2011009)资助
关键词
胡敏酸
电解质
光散射
凝聚
分形维数
Humic substance
Electrolyte
Light scattering
Aggregation
Fractal dimension
作者简介
高晓丹（1987-），女，辽宁葫芦岛人，博士研究生，主要从事土壤胶体化学研究。E—mail：wataxi221@126．com
通讯作者，E—mail：hli22002@yahoo．com．cn，Tel．：023—68250674
