黄土高原植被恢复过程中土壤表面电化学性质演变特征

土壤胶体表面所带电荷是土壤具有一系列物理、化学性质的根本原因。表面电荷数量、比表面积、表面电荷密度、表面电场强度以及表面电位是土壤胶体颗粒重要性质,影响土壤中物理、化学、生物化学过程。运用带电颗粒表面性质联合分析法,测定黄土高原子午岭地区不同植被类型下土壤表面电荷性质,研究自然植被恢复过程对土壤表面电荷性质的影响。结果表明:随着植被的演替,子午岭林区土壤表面电荷数量、比表面积、表面电荷密度均随植被的恢复增加,变化范围分别为10.88～19.85 cmol·kg~(–1)、40.67～61.71 m~2·g~(–1)和0.22～0.31 c·m~(–2),平均值分别为16.18 cmol·kg~(–1)、54.88 m2·g~(–1)和0.28 c·m~(–2),土壤表面电场强度达108 V·m~(–1)数量级;土壤黏粒、有机碳含量是影响表面电荷性质的主要因素,解释率分别为62.5%和27.9%;土壤基本性质对表面电荷性质的影响由强到弱依次为:黏粒、有机碳、砂粒、全氮、C/N、粉粒、碳酸钙、pH。研究结果对于进一步认识黄土高原土壤颗粒表面性质,加深理解土壤中发生的一系列物理化学过程具有重要意义。     

氧化石墨烯和五价砷在改性多孔介质中的共迁移特征

砷是农田土壤重金属污染的主要元素之一,在砷污染农田土壤的修复过程中往往忽视纳米颗粒能够使结合态的砷重新释放,导致有效态砷浓度升高,探究土壤中黏土矿物对氧化石墨烯(Graphene Oxide,GO)和五价砷(As(V))在多孔介质中迁移行为的影响,对进一步完善农田土壤砷修复理论以及提高农作物产量、保护人体健康具有重要意义。该研究利用蒙脱石和高岭石改性石英砂,通过砂柱迁移试验系统地研究了GO、As(V)和GO-As(V)在填加0%、10%、30%和50%的蒙脱石和高岭石改性石英砂柱中的迁移行为。研究结果表明,随着高岭石和蒙脱石改性石英砂填加比例的增加,GO和As(V)的迁移能力均呈降低趋势,且GO和As(V)在不同条件下的迁移曲线均存在显著差异(P0.05);GO在50%高岭石和蒙脱石改性石英砂柱中的回收率相对于石英砂柱分别下降了14%和17%,As(V)分别下降了15%和12%;在共迁移试验中,GO和As(V)在石英砂柱中回收率分别上升至99%和100%。分析表明,As(V)在蒙脱石改性石英砂柱中的迁移能力大于高岭石改性石英砂,而GO与之相反;当GO和与As(V)共迁移时,二者在介质中的迁移能力均大于其单独迁移。本研究表明GO、As(V)释放到土壤后,能够加速As(V)的迁移,造成土壤砷污染的扩大化。     

柱撑酸化蒙脱土催化合成丙烯酸正丁酯的研究

将蒙脱土经不同方法进行改性处理,并以此为催化剂,催化丙烯酸与正丁醇反应生成丙烯酸正丁酯。考察了以微波处理的柱撑酸化蒙脱土为催化剂催化合成丙烯酸正丁酯的反应条件。结果表明,以微波处理的柱撑酸化蒙脱土催化效果最好,适宜的反应条件为：丙烯酸为0.1 mol,醇酸的摩尔比为1.2：1,阻聚剂为对苯二酚,其用量为0.3 g,约为丙烯酸质量的4%,催化剂的用量1.7g,约为丙烯酸质量的20%,反应的时间为7 h,在回流状态下,其酯化率为84.1%。催化剂可以重复使用。     

Evaluation on Tolerance of Montmorillonite as a Mycotoxin Adsorbent

In order to study the tolerance dose of Kunming mice to montmorillonite as a mycotoxin adsorbent in diets,the experiment selected 60 healthy male Kunming mice with initial average body weight of (17±0.12)g,randomly divided them into 5 treatments with two replicates per group and 6 mice per replicate.Five experimental diets were added to 0 (control group),0.5%,1%,2% and 5% montmorillonite,respectively.After 30 days,the growth performance,nutrients apparent digestibility,serum biochemical indices and internal organization were tested to determine the tolerance dose of montmorillonite for Kunming mice.The results showed that the ADFI was significantly increased in 0.5% group (P< 0.05),while there were no significant differences in ADFI and ADG between 1% group and control group (P> 0.05),then the ADFI was significantly decreased with the increasing of montmorillonite supplemental level (P< 0.05).The ADG in 2% group had no significant difference when compared with the control group (P> 0.05),while significantly lower than that in 0.5% and 1% groups (P< 0.05).The apparent digestibility of DM,CP and EE showed no significant effect at any level of montmorillonite (P> 0.05).Serum ALT,AST activities and MDA content were gradually increased with the montmorillonite supplemental level increasing,and that in 1%,2% and 5% groups were significantly higher than that in control group (P< 0.05),but there were no significant differences between 0.5% group and control group (P> 0.05).Tissue sections showed that mice livers were damaged in varying degrees when the montmorillonite supplemental level was 5%.In conclusion,based on a comprehensive consideration of all indexes,it could be seen that the tolerance dose of the tested montmorillonite for Kunming mice was between 0.5% and 2% when mycotoxin contents in diets were in security range.     

酚醛树脂/蒙脱土混合溶液固化特性研究

用单因素法分析蒙脱土和酚醛树脂混合溶液的固化情况,结果表明蒙脱土分散浓度增加,混合溶液固化时间增长;酚醛树脂浓度和固化温度加大,固化时间缩短,其中温度是影响固化效果较为明显的因素;不加固化剂时固化效果更好.     

纳米蒙脱石抑菌性能研究

本文采用快速分散、研磨、高速离心的方法对高纯蒙脱石进行分级,研究普通蒙脱石和纳米蒙脱石抑制黄曲霉菌的效果。结果表明:蒙脱石在水中分散后,逐步由悬浮液转变为凝胶体,当中位径为3.9μm时,抑菌效果较差;中位径为0.92μm时,抑菌效果明显提高;中位径为0.26μm时,抑菌效果最好。     

华北平原农灌咸淡水侵入界面渗透性变化机理研究

从研究应用背景、基础理论及模型、实验模拟等方面就微咸水灌溉过程,侵入界面土壤渗透性变化进行分析研究.以衡水典型研究区微咸水分布及水质矿化度分析数据为基础,应用地球化学模式PHREEQC,结合水敏性机理分析矿物迁移的存在形式及各种形式之间的转化关系.结果表明:含高价离子农灌微咸水加快粘土胶体颗粒絮凝沉降能力强于低价离子,...     

Soil colloids-bound plasmid DNA: Effect on transformation of E. coli and resistance to DNase I degradation

The adsorption and binding of plasmid p34S DNA on four different colloidal fractions from a Brown soil and clay minerals in the presence of various Ca²⁺ concentrations, the ability of bound DNA to transform competent cells of CaCl₂-treated Escherichia coli, and the resistance of bound DNA to degradation by DNase I were studied. DNA adsorption on soil colloids and clay minerals was promoted in the presence of Ca²⁺. Kaolinite exhibited the highest adsorption affinity for DNA among the examined soil colloids and clay minerals. In comparison with organo-mineral complexes (organic clays) and fine clays (<0.2 μm), DNA was tightly adsorbed by H₂O₂-treated clays (inorganic clays) and coarse clays (0.2-2 μm). The transformation efficiency of bound DNA increased with increasing concentrations of Ca²⁺ at which soil colloid or clay mineral-DNA complexes were formed. DNA bound by kaolinite showed the lowest transformation efficiency, and especially no transformants were observed with kaolinite-DNA complex prepared at 5-100 mM Ca²⁺. Compared to organic clays and fine clays, DNA bound on inorganic clays and coarse clays showed a lower capacity to transform E. coli at different Ca²⁺ concentrations. The presence of soil colloids and minerals provided protection to DNA against degradation by DNase I. Montmorillonite, organic clays and fine clays showed stronger protective effects for DNA than inorganic clays and coarse clays. The protection mechanisms as well as the differences in transforming efficiency of plasmid DNA molecules bound on various soil colloidal particles are discussed. The information obtained in this study is of fundamental significance for the understanding of the horizontal dissemination of recombinant DNA and the fate of extracellular DNA in soil environments.     

蒙脱石矿物材料絮凝剂的制备、絮凝效果及机理研究

为了降低絮凝剂毒性、提高絮体的分离效果,以无机矿物材料蒙脱石(MTS)为原料,通过酸改性,制备蒙脱石絮凝剂(MTSF),对比聚合氯化铝(PAC)絮凝剂来处理模拟废水。实验结果表明,MTS没有絮凝作用,但经过酸改性后的MTSF具有很好的絮凝效果,最大浊度去除率为96.73%,在絮体沉降速度及体积上,MTSF远优于PAC。MTSF絮凝机理是吸附-电中和,絮凝过程是固体颗粒和可溶性盐两者的协同作用,MTSF显示出较好的沉降性能和压缩性能,絮体达到沉降平衡后,其体积不足PAC的三分之一。MTSF与PAC絮凝剂复合使用,可有效地减少絮体体积,提高絮体沉降性能。总之,MTSF具有与PAC相同的絮凝效果,但是絮体的沉淀压缩性能远优于PAC,是一种综合性能优越的絮凝剂。     

Cu2+和Zn2+在土壤电场中的极化对黑土胶体凝聚的影响

金属离子在土壤胶体固-液界面上的行为差异引起土壤胶体絮凝过程的差异,并深刻影响土壤溶液中养分或污染物的迁移转化。为明确Cu~(2+)和Zn~(2+)两种金属离子界面行为对土壤胶体凝聚的影响,本文选取黑土胶体为研究对象,利用动态/静态光散射技术研究专性吸附离子Cu和Zn体系中不同离子浓度条件下黑土胶体的凝聚行为。结果表明:(1)Cu~(2+)和Zn~(2+)两种金属离子引发黑土胶体凝聚的机制相似,均是低浓度下的慢速凝聚和高浓度下的快速凝聚,达到快速凝聚机制后,胶体的总体平均凝聚速率受离子种类影响较小。(2)Cu~(2+)对黑土胶体聚沉能力大于Zn~(2+),Zn~(2+)的临界聚沉浓度是Cu~(2+)的3.51倍,在黑土胶体的凝聚过程中存在强烈的离子特异性效应。(3)两种离子体系中颗粒间相互作用的活化能差异随离子浓度的降低而增大。此两种离子在凝聚作用的较大差异性源于Cu~(2+)较Zn~(2+)对有机配位体有较强的亲和力,以及黑土胶体表面附近强电场对离子的强烈极化作用扩大了两种离子本身的微小差异。