TiCl 4改性钠基膨润土的制备及其对U(Ⅵ)和Th(Ⅳ)的吸附性能研究

采用阳离子插层法制备了TiCl_4改性的钠基膨润土(Ti-Na-bent),并研究了Ti-Na-bent对U(Ⅵ)和Th(Ⅳ)的吸附性能。扫描电镜(SEM)和X射线粉末衍射(XRD)表征结果显示,钛以粒状非晶态的形式存在于钠基膨润土(Na-bent)的表面或层间。吸附实验结果表明,当温度为298K,吸附剂用量为10mg,U(Ⅵ)、Th(Ⅳ)初始质量浓度为500mg/L,pH分别为5.0、2.5,反应时间为2h时,Ti-Na-bent对U(Ⅵ)和Th(Ⅳ)的最大吸附量分别为336.25、231.62mg/g,比改性前分别提高了1.67倍、70%。吸附U(Ⅵ)和Th(Ⅳ)的过程符合Freundlich模型和准二级动力学模型,属于吸热、熵增的自发过程,吸附机理主要为UO_2~(2+)、Th~(4+)、[(UO_2)_n(OH)_(2n-1)]~+、[Th(OH)_2]~(2+)与Na-bent上可交换的阳离子和Ti(OH)_4上的氢之间的离子交换。Ti-Na-bent对U(Ⅵ)、Th(Ⅳ)的吸附容量高、稳定性好,有望用于处理含U(Ⅵ)、Th(Ⅳ)的放射性废水和用作高放废物地质处置库缓冲/回填材料。     

3种改良剂对铅锌矿渣中重金属形态及植物富集的影响

以衡阳市某铅锌尾矿库的矿渣作为土壤基质,泥炭土、红壤、蛭石作为改良剂,夹竹桃作为受试植物,进行室外盆栽试验,考察了3种改良剂对夹竹桃生长、重金属(Pb、Zn)富集转移能力以及土壤基质中Pb、Zn形态的影响。结果表明:(1)在5%(质量分数,下同)～15%的添加量下,3种改良剂均显著(p0.05)提高夹竹桃的株高增量与生物量增量,根系形态指标值也均有所提高,总体改良效果为蛭石泥炭土红壤。(2)夹竹桃地下部分Pb、Zn含量高于地上部分,添加改良剂后地上部分与地下部分Pb、Zn含量降低,说明改良剂高效抑制了重金属在夹竹桃中的富集;红壤与蛭石可抑制夹竹桃体内Pb的转运,但泥炭土却对Pb的转运起促进作用;除蛭石15%处理外,其余所有处理均促进了Zn在夹竹桃体内的转运。(3)3种改良剂在不同添加量下均显著降低了矿渣中弱酸可提取态Pb、Zn的含量(p0.05),有效降低了重金属Pb、Zn在土壤基质中的活性。     

油菜对铜胁迫的生理响应及铜在茎杆和籽粒中的富集特征

以秦优九号为材料,通过盆栽试验研究了0、50、100、200、400mg/kg铜处理对油菜生长、产量、矿质元素含量的影响及铜在茎杆和籽粒中的富集特征.结果表明,低质量浓度(50mg/kg)铜处理,在一定程度上刺激了油菜的生长,植株的生物量、产量和矿质元素含量等指标均略高于对照或与对照相当,但差异不显著.随着土壤中铜浓度...     

高岭土胶体对nZVI修复Pb、U污染硅藻土的影响及机制

纳米零价铁 (nZVI) 大量应用于土壤重金属污染的修复,但由于土壤广泛存在的胶体可协同污染物的迁移与扩散,影响nZVI对土壤的修复效果。针对这一问题,通过硅藻土柱实验和重金属运移速率分析,并采用微观结构表征分析 (SEM) 与物相分析 (XRD) 方法,探究高岭土胶体对nZVI修复铅 (Pb) 、铀 (U) 重金属污染土壤的影响机制。结果表明,nZVI可固化Pb和U,阻滞其运移以修复土壤;高岭土胶体的加入可削弱nZVI对重金属的阻滞效果,增强Pb和U的运移能力;但在高岭土胶体与nZVI同等质量浓度下,高岭土胶体对阻滞效果的影响有限;另外,在Pb、U复合体系中,存在竞争吸附现象,nZVI对Pb的阻滞效果优于U,U的运移更易受到高岭土胶体的影响。本研究结果可为土水重金属污染防治提供参考。     

小花南芥与玉米间作对Pb化学形态及富集特征的影响

间作植物根与根之间的相互作用影响根际土壤理化性质。目前关于超富集植物与作物间作根际土壤pH是否引起Pb赋存形态的变化,不同赋存形态与超富集植物和作物富集Pb的差异机理尚不清楚。设置不同Pb处理浓度,小花南芥和玉米间作、单作为对照的土培实验。随着Pb处理浓度增加,间作小花南芥生物量显著增加,范围为19.00%~181.08%,Pb富集系数为2.78,显著增加74.02%,转运系数为1.46,变化不显著,其中Pb含量显著增加25%。Pb赋存形态主要以难溶态果酸盐、蛋白质和磷酸盐结合态存在,约占总量的50%,间作显著降低小花南芥根际土壤溶液、根和茎叶中的pH;间作玉米生物量随着Pb处理浓度先显著增加后降低,增加范围为18.59%~49.48%,Pb富集系数平均为0.53,显著降低34.57%,转运系数平均为0.56,显著降低12.51%,Pb赋存形态以草酸盐结合态存在,约占30%,间作显著增加玉米根际土壤溶液、根和茎叶中的pH。揭示间作改变2种植物根际土壤溶液、根和茎叶中pH,从而引起Pb化学形态不同,这是导致超富集植物小花南芥吸收富集Pb,降低玉米体内Pb的主要原因。     

Effects of amendments on the uptake and distribution of DDT in Cucurbita pepo ssp pepo plants

The effects of soil amendments on the phytoextraction of ∑DDT (DDT + DDD + DDE) from soil ([∑DDT] ∼ 1500 ng/g) by a pumpkin variety of Cucurbita pepo ssp pepo were tested and the patterns of ∑DDT storage throughout the plant shoot were examined. The soil amendments did not increase the total amount of ∑DDT extracted into plant shoots, but new information about ∑DDT distribution in the plants was obtained. As observed previously, the ∑DDT concentration in plant leaves (mean 290 ng/g) was significantly lower than in plant stems (mean 2600 ng/g). Further analysis revealed that ∑DDT composition was consistent throughout the plant shoot and that ∑DDT concentration in leaves and stems decreased exponentially as distance from the root increased, which was previously unknown. This new information about the patterns of ∑DDT uptake and translocation within pumpkin plants highlights the need for appropriate plant sampling strategies in future POPs phytoextraction research.     

Effects of soil properties on heavy metal accumulation in flowering Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) in Pearl River Delta,China

This study was conducted to investigate the effects of soil properties on the heavy metal accumulation in flowering Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) at the field scale. The concentrations of cadmium (Cd), mercury (Hg), and chromium (Cr) in topsoil and vegetable samples from Nanhai district of Foshan city in the Pearl River Delta (PRD) were analyzed. The results showed that 56.5% of the soil samples exceeded the grade II of the Chinese Soil Environmental Quality Standard (GB 15618-1995) for Hg concentrations, while 8.70% and 17.4% of the vegetable samples exceeded the criteria of the Chinese Safety Qualification of Agricultural Products (GB 18406.1-2001) for Cd and Hg concentrations, respectively. The calculated bio-concentration factor (BCF; i.e., the ratio of the metal concentration in the edible parts of flowering Chinese cabbage to that in soil) values were ranked as: Cd (0.1415) > Cr (0.0061) > Hg (0.0012) (p < 0.01), which demonstrated that Cd was easier to be accumulated in the edible parts of flowering Chinese cabbage than Hg and Cr. Furthermore, the following relationships between (bio-concentration factor) BCF values (BCFs) and soil physicochemical properties were concluded from our results: i) the mean BCFs of coarse-textured soils were higher than those of fine-textured soils; ii) the BCFs decreased with increasing soil pH; iii) the soils with high organic matter(OM) and Cation exchange capacity (CEC) have low BCFs, resulting from their high sorption capacities for Cd, Hg, and Cr. The stepwise linear multiple regression analyses showed that total metal concentrations and available calcium in soils were two main factors controlling the accumulation of Cd, Hg, and Cr in the flowering Chinese cabbage.     

Effects of methamidophos on the community structure,antagonism towards Rhizoctonia solani,and phlD diversity of soil Pseudomonas

A microcosm incubation study using an aquic brown soil from northeast China (a Cambisol in the UN Food and Agriculture Organization FAO Soil Taxonomy) was conducted to examine the effects of different concentrations (0, 50, 150, and 250 mg kg^?1) of methamidophos (O,S-dimethyl phosphoramidothioato) on Pseudomonas, one of the most important gram-negative bacteria in soil. Amplified ribosomal DNA restriction analysis (ARDRA) was performed to study the Pseudomonas community structure, an in vitro assay was made to test the antagonistic activity of isolated Pseudomonas strains against soil-borne Rhizoctonia solani, a major member of the pathogens highly related to soil-borne plant diseases, and special primer amplification and sequencing were performed to investigate the diversity of phlD, an essential gene in the biosynthesis of 2, 4-diacetylphloroglucinol (2, 4-DAPG), which has biocontrol activity in phlD ⁺isolates. With exposure to increasing methamidophos concentrations, the total number of soil Pseudomonas ARDRA patterns decreased significantly, but with less change in the same treatments over 1, 3, and 5 weeks of incubation. The number of isolated Pseudomonas strains with antagonistic activity against R. solani as well as the diversity and appearance frequency of the strains' phlD gene also decreased with increasing concentrations of methamidophos, especially at high methamidophos concentrations. Applying methamidophos could increase the risk of soil-borne plant diseases by decreasing the diversity of the soil Pseudomonas community and the amount of R. solani antagonists, particularly those with the phlD gene.