【作者】 李光林；

【导师】 魏世强； 青长乐；

【作者基本信息】 西南农业大学 ， 土壤学， 2002， 博士

【摘要】 在地球生态环境中，腐殖酸是分布最为广泛的天然有机物质，几乎所有的环境中都有分布，如土壤、水体和沉积物等。由于它含有多种功能基，如羧基、醇羟基、酚羟基、醌型羰基和酮型羰基、甲氧基、醛、酮、醚等，因此具有很高的反应活性，能与环境中的金属离子、氧化物、氢氧化物、矿物质、有机质、有毒活性污染物等物质发生相互作用，形成具有千差万别的化学和生物学稳定性的溶于水和不溶于水的物质。这些相互作用对于土壤中养分的保蓄、土壤良好结构的形成、土壤酸碱度调节、水土保持、土壤和水环境中有害毒性物质的降低或清除、植物元素营养平衡、乃至整个土壤和水生生态系统的结构、功能等方面起着重要的调控作用。尽管以土壤肥力为中心的腐殖质研究已有近100年历史，但真正认识到腐殖质在生态环境中的重要作用和意义则是近十多年。 无论是腐殖质在维持土壤肥力还是其对环境物质的迁移、转化以及循环的中枢调控作用，其内在机制均源于其特殊的理化性质和极高的反应活性。尽管研究重点有所不同，但涉及的内在机理确有着共同性，其中腐殖酸组分与不同类型金属离子的反应在两方面都具有特别重要意义，探讨腐殖酸与重金属离子相互作用特征参数和反应机理，是理解腐殖酸调控金属离子生物有效性或毒性控制，计算金属离子在环境中的存在形态和分布的基础。尽管在简单的化学体系中，金属离子与有机物质的相互作用已有很详尽的认识，但当有腐殖酸参与时，由于腐殖酸结构的复杂性，则使情况变得十分复杂。国际上的研究针对单一元素研究较多，且有大部份研究忽略了腐殖酸溶液的实际存在状态，而偏重采用不同数学模型拟合实验数据。国内目前只对铜、锌、汞等元素有一定研究，且只偏重对络合常数测定方面。事实上，金属元素的种类和形态是多样的，而且自然界中重金属污染多为伴生性和综合性，如Cd、Zn两元素具有相同的地化和环境特征，在锌矿开采中就常有Cd向环境释放，而对腐殖质本身来说，也常因提取方法、地域、气候、植被等差异，而在结构和性质方面不尽相同。因此针对这些情况，本实验重点研究Cu、Pb、Cd在腐殖酸上的吸附与解吸特征，溶液PH、温度、离子强度影响、反应的动力学和热力学特征，以及Cd、Zn单独和共存时与腐殖酸的络合稳定性和配位数。在研究方法上，采用改进的电位滴定、离子选择电极和离子交换平衡法，在研究步骤上：首先对供试腐殖酸进行基本组分和功能基的测定，对使用电极用标准液进行校准，探讨腐殖酸与质子反应体系特征，建立“稳态”指标，利用建立的稳态指标对腐殖酸进行电位滴定，确定解离常数，然后在稳态条件下用电极法研究腐殖酸对Cu、Pb、Cd离子的吸附规律，确定特征参数，以及pH、温度、离子强度对吸附特征参数的影响；其三是比较研究腐殖酸对三种金属元素的吸附和解吸性能差异，最后利用离子交换平衡法研究Cd、Zl单视在和复合时腐殖酸 Cd（Zn）络合物稳定常数和配位数。通过这些研究力图揭示腐殖酸与o、ph、－Cd络合机理、吸附特征，两种金属离子交互作用时稳定性和生物有效性，为预测和控制生态环境中重金属元素迁移、转化奠定了理论基础。主要研究结果如下： 腐殖酸两组分胡敏酸主耍功能基含量为；总酸性基为6．8500OI／g，按基2．921111llOI／g，酚羟基3．93mmollg，富里酸总酸性基 10．58 mmUg i基687 mmollg，酚羟基 3．71 mmollg。胡敏酸总酸性基小于富里酸，富里酸波基含量大于胡敏酸，田羟基胡敏酸略大于富里酸。腐殖酸吸附金属高于多少，主要由酸性基的数量决定，富里酸单位碳量吸附金属离子远大于胡敏酸，主要原因在此。胡敏酸碳含量为46．38％，氮含量为3．98O／O；灰分量为0．99％；而富里酸碳含量为38．30％，氮含量为2刀9％，灰分量为l．26％。 采用经改进的电位滴定研究了胡敏酸与质子反应动力学特征，在保证连续恒定通氮气严格无氧条件下，用标准酸将胡敏酸从叫7．8左右逐步滴定到pHZ．6左右，在每一滴定点的质子反应动力学可分为快反应和慢反应两个阶段，每一滴定点体系因加入标准酸受到扰动后。需经过25小时才能建立新的平衡，以初始滴定点（pH7石3－－．42）的反应动力学为例，体系加入标准酸后，氧化还原电位ER开始升高，最后逐渐下降，经过 12（y－－xo分钟才达到新的“稳态＼而玻璃电极电位EG的变化也出现开始有一升高，最后趋于稳态，但趋于稳态的时间比ER快得多。玻璃电极电位与反应时间可用 Et；＋（EZ－EI）（1－e””）＝－41．2＋5．2（l护·％（p0．9945，o。0．001，n＝62）动力学方程描述。E，为初始玻璃电位，面为稳态玻璃电位，时间常数T表征反应快慢程度，不同滴定点T值的变化在 58．7－－－－x3刀8分钟之间，pH降低，时间常数增加，每一滴定点 EG到达新的“稳态”时间增加。体系滴定点（PH7石3～－－x．42）氧化还原电位随时间的变化用动力学方程 ＿矿 E。＝。（r－AI．9997”’．Q＝62．Q d．001） O．O133矿一O．1813加以描述。同时发现在一定条件下，特别是在pH7．62左右，慢反应阶段还可观察到明显的ER?更多还原

【Abstract】 Humic acids, the most widely distributed natural organic matter in the biological environment, are distributed almost everywhere in our environment such as the soil, water and deposit. Owing to their great variety of function groups, such as carbonyle group, alcohol hydroxyl group, phenol alcohol group, keto acid, aldehyde, ketone, and ether, et al, they have great activation in reaction, and can react on such matters as metal ions, oxide, hydroxide, minerals, organic matters and toxic pollutants. These reactions can produce endless variety of soluble and insoluble substances of physical and chemical stability,and they are greatly significant in controlling and adjusting the maintenance of soil nutrients, the formation of good soil structure,the soil acidity and basicity, thewater and soil conservation, the decrease or removal of toxic substances in soil and water, the balanceof plant element nutrient, the structure and function of the overall soil and aquatic biological system.Although the study on humus focused on soil fertility has been going on for over 100 years, it is not until the recent 10 years that the great significance of humus to the biological environment has been realized.Both the function of humus in maintaining soil fertility and in controlling and adjusting the shifting, transformation and circulation of substances are based on its special physical and chemical qualities and its great activation. In spite of the different focuses, different studies have generalities, in which the reaction of humic acid on different kinds of metal ions are of great significance in two aspects. The study on the characteristic parameter and mechanism in the reaction of humic acids on heavy metal ions is the basis to understand the way humic acids control and adjust the organic effectness of metalions or toxicity control, and to measure the shape and distribution of metal ions in the environment Although in simple chemical system there has been thorough understanding of the reaction of metal ions on organic matters, yet because of the complexity of humic acids, the reaction will become rather complicated when humic acids are involved.On the one hand, there have been manystudies worldwide on single elemnt, and most of them lay particular stress on imitating experimentaldata by means of different mathematical models, but ignore the actual existing form of humic acids solution. On the other hand, presently, there have been only some studies on such elements as Cu, Zn and Hg, and they only focus on the determination of complexing constant.But metal elements are in fact of various kinds and forms, and the heavy metal pollution in the nature is mainly satellite phemnenon and syndrome. For example, Cd and Zn have the same geochemical and environmental characteristics, and in zinc mining there is often emitting into the environment. And humus often differs in its structure and qualities because of the difference in refining method, area, climate and plantation.This experiment aims at these problems and focuses on studying the characteristics of theadsorption and desorption of Cu. Pb and Cd on huic acids, the pH of the solution, temperature, the effect of ion strength, the kinetic and thermological characteristics of reactions, and the complexing stability and cooridination number of Cd and Zn to humic acid, both respectively and put together. Such methods as improved potentialtitration, ion selective electrode, and ion-exchange equilibrium method are used in the experiment. The following procedure is followed in the experiment: Firstly, determine the basic components and the function groups of the humic acids on trial; calibrate the chosen electrode with standard solution; probe into the characteristics of the system of reaction of proton on humic acids; set up a "stable index"; use this "stable index" to get the potential titration of humic acids and determine the disosociation constant and the study the adsorption pattern of humic acids to Cu, Pb and Cd by using electrode under constant conditions and thus de更多还原