【作者】 张坤峰；

【导师】 沈照理； 何江涛；

【作者基本信息】 中国地质大学（北京） ， 环境科学与工程， 2010， 博士

【摘要】 有机污染物在从地表进入地下水的垂向入渗过程中,一方面表层土壤/沉积物中含有较高的有机质,对有机污染物的吸附起到了重要作用;另一方面由于包气带下部土壤介质数量巨大,对于有机污染物的吸附同样有重要影响;因此,开展有机污染物在垂向剖面介质中吸附行为特征研究,具有重要意义,本论文以三氯乙烯(TCE)为典型的有机污染物,以北京某地区包气带土壤为研究对象,实验室条件下,研究了垂向剖面上土壤组成、有机质变化规律及其对有机污染物TCE的吸附行为影响特征。论文主要取得以下研究成果:(1)包气带下部土壤的理化性质之间有明显的相关关系,特别是粘粒含量是影响土壤垂向剖面有机质含量、结构组成、腐殖化度以及有机质-矿质复合体变化的一个重要因素,其影响可能高于土壤沉积形成时期有机质初始含量和沉积年代,而有机质含量、结构组成、腐殖化度和复合体的差异对TCE吸附行为产生直接影响,因此,垂向剖面上粘粒含量的变化是影响TCE迁移、转化的关键因素。碱提取液吸光度测量方法简便,可以用作土壤腐殖化度的表征,与胡富比(HA/FA)和HA/TOC表征腐殖化度结果一致。(2)富里酸比胡敏酸酸性强,富里酸多以羧酸形式存在,胡敏酸多以羧基负离子的形式存在,胡敏酸结构比富里酸结构更为致密,同一层位胡敏酸比富里酸含碳量高,饱和程度也更高;表层土壤提取出来的胡敏酸与包气带土壤提取胡敏酸性质不同,表土胡敏酸中含有较多的甲基、亚甲基、羟基和羰基官能团,腐殖化程度相对较低,稳定性差,实验浓度范围内,对TCE吸附的Kd和Koc值均大于包气带土样胡敏酸。(3)在有机污染物垂向入渗的过程中,包气带介质中大量无机矿物的吸附作用不容忽视,土壤矿物组分对TCE等温吸附式为langmuir等温吸附,有最大吸附量;包气带下部土壤吸附过程中,在foc较小时,非线性较明显,当foc<0.16%以下时,无机矿物对TCE吸附贡献率相对较高,贡献率可能高达20%以上;随着有机碳含量的升高,当foc>0.82%以后,无机矿物的平均贡献率小于5%;有机质对TCE吸附贡献率显著提高,线性吸附趋势显著增强。(4)TCE溶液浓度对吸附产生影响,不同的污染物浓度会引起有机质和矿物质在吸附中的贡献率发生变化,污染物TCE浓度越高,有机质的吸附贡献率相对上升,矿物质的吸附贡献率相对下降。foc=0.16%时,在TCE浓度为50-500μg·L-1范围内,矿物质的贡献率波动范围为28%-16%。而foc>1%时,矿物质对吸附的贡献率下降到3%-1%之间。(5)土壤中有机质与粘土矿物是以有机质-矿质复合体形式存在;一方面,复合体中有机质并不是均匀覆盖在矿物质表面,矿物质对有机质存在选择性的吸附,高岭石易于吸附有机质中的—CH2基团,蒙脱土主要吸附芳烃基团;另一方面,土壤中有机质与矿物质结合形成有机质-矿质复合体后,有机质会进一步聚合,形成缩聚体,缩聚体中含有大量孔隙结构,随着复合体中有机质含量的增加,缩聚体聚合更加紧密,复合体内部孔径变小;有机质官能团的吸附效应和空隙填充效应两方面共同作用的结果,最终影响有机质-矿质复合体对有机污染物的吸附;即粘土含量高,复合体中有机质含量高,腐殖化度高,由于官能团对污染物的吸附作用强,空隙填充作用小。更多还原

【Abstract】 On the course of organic contaminants go into groundwater from surface on profile, there are a large mass of organic matter in topsoil/sediment. It plays an important role of sorption of organic contaminants. On the other, as there are so much soil medium in the subsoil on profile. This must do great influence for sorption of organic contaminants. As the result, it will be much usage to begain the researches of sorption of organic contaminants on vedose zone. This research aimed at the organic contaminants of TCE. In the laboratory, with the soil of vidose zone on profile in one area of Beijing, this paper studyed the sorption behaviors of organic contaminants trichloroethylene (TCE) with the changes of compose of soil and organic matter. The results of the research were as follows:(1) The correlation is close among clay content, clay mineral, humification degree and TOC. The clay content of soil compose is the key influence to the content of TOC and the degree of humification of subsoil on profile. Particularly, the clay content influences the content of organic matter, structure and humification degree and organo-mineral complexes. The influence of clay content must be greater than the initial content of organic matter in the era of sedimentation and the deposit years. The differences, such as the content of organic matter, structure, humification degree and the complexes, affect the sorption behaviors of TCE. Consequently, the change of clay content is the key factor to influence the remove and transformation of TCE on vertical profile. The absorbance of alkali liquid can be used to replace HA/FA and HA/TOC to character the degree of humification of soil. (2) The carboxyl functional groups of HAs are mainly COO– and the FAs’are COOH. Thus the acidity of FAs is higher. The structure of HAs is more compact than FAs, and HA has more saturation and more content of carbon than FA extracting from the same soil samples. The humic acids between topsoil and subsoil do not have the same characters. Tophumic acids have much methyl, methylene, hydroxyl group and carbonyl group. Tophumic acids have less humification degree and less stability. Kd and Koc of humic acids extracted from topsoil(tophumic acids) to TCE sorption are bigger than the humic acids exctracted from subsoil(subhumic acids) normally. (3) Organic adsorption behavior of TCE plays a very important role. However, on the course of organic contaminants go into groundwater from surface on profile, there is a large mass of mineral in vadose zone. The sorption of mineral does not be neglected. The TCE adsorption isotherm of soil sample is nonlinearity clearly in subsoil and the contribution ration of mineral adsorption is higher while foc is less. The linear of the adsorption isotherm of soil samples is bigger obviously with a little increasing of content of organic matter on vertical profile. The TCE adsorption isotherm of mineral is Longmuir and there is the biggest adsorption. (4) The adsorption isotherm of sample can be changed by the solute concentration of TCE, foc increases and n values increase gradually. Different concentration of TCE will lead to the much difference in adsorption ratio between organic matter and mineral. The more is concentration of TCE, the higher is sorption rate of organic matter and the less is adsorption rate of mineral. The adsorption rate of mineral changes between 28% and 16% when foc equals 0.16% and TCE changes between 50μg·L-1 and 500μg·L-1. The adsorption rate of mineral changes between 3% and 1% when foc greater than 1% and the influence of the adsorption rate of mineral and organic matter to TCE is less. (5) The mineral is not covered uniformly by organic matter but is distributed irregularly on sorption point after the organo-mineral complex formed in soil. Kaolinite attracts–CH2 easily and montmorillonite aromatic group easily. On the other hand, the complexes can be contracted to form polymerizations with the increasing of organic matter. There is a great deal of interspace in the polymerizations. The higher is the content of organic matter the more compact is the polymerizations. The interspace diameter gets smaller. The results of two aspects affect the TCE sorption of complexes.更多还原