钝化剂在烟草植物修复铅镉污染土壤中的作用

重金属钝化剂可以改变土壤中重金属的形态，降低其在土壤中的有效浓度、植物毒性及生物有效性，影响污染土壤中植物的生长及其对重金属的吸收。在温室盆栽条件下研究了施加羟基磷灰石（HA）、纳米羟基磷灰石（nHA）、纳米零价铁（nFe0）和纳米TiO2（nTiO2）对烟草植物修复铅镉污染土壤的作用。结果表明，HA降低土壤中Ph、cd的有效性、促进烟草生长、增加了烟草叶、茎、根中cd的吸收量和根系中Pb的吸收量，有利于Ph、cd的钝化和植物修复。nHA也可以降低土壤中Pb、cd的有效性，增加了烟草叶中cd的吸收量，有利于Pb、cd的钝化和cd的植物提取。nFe0和nTiO2：对于土壤Pb和cd的钝化作用和植物修复均没有显著影响。综合来看，HA最适合应用于烟草植物修复铅镉污染土壤。     

锰掺杂WO3-TiO2复合光催化剂的制备及其性能研究

溶胶-凝胶和浸渍相结合的方法制备锰掺杂WO₃-TiO₂复合光催化剂，RXD表征，考察WO₃和Mn²⁺掺入量、焙烧温度、焙烧时间及催化剂用量对光催化降解甲基橙的影响。结果表明，500℃焙烧2h，掺杂量n_{（Mn²⁺）}∶n_（WO3）∶n_（TiO2）＝0.8∶1∶100时，光催化活性最高，光催化降解甲基橙溶液，120min后，降解率达90%, 比单纯 TiO₂的光催化活性提高81%。     

EDTA/纳米羟基磷灰石联合修复重金属污染土壤

土壤淋洗可能导致残留重金属活化,采用淋洗/钝化联合修复重金属污染土壤可在一定程度上减少这一影响。研究了EDTA淋洗、纳米羟基磷灰石钝化及两者联合修复对土壤重金属洗脱率、TCLP浸出浓度、化学形态分布的影响,构建了涵盖土壤重金属残留量、生物有效性和生理毒性的环境风险评价方法,对淋洗、钝化及其联合修复进行了评价。结果发现,EDTA淋洗对Pb和Cu的洗脱效果较好,对Zn浸出浓度的削减率较高。当EDTA投加量为2 g·L~(-1)时,Zn的浸出浓度降低了70.40%。纳米羟基磷灰石对Pb和Zn具有较好的钝化效果,对Cu和Cd的钝化作用相对较弱。当纳米羟基磷灰石投加量为2%时,Pb浸出浓度削减率高达89.65%。淋洗/钝化联合修复大幅度降低了Pb和Cd的浸出浓度,降低了可还原态Cu残留量、可还原态和残渣态Cd残留量,以及弱酸提取态和可还原态Zn、Pb残留量。当EDTA和纳米羟基磷灰石投加量分别为1 g·L~(-1)和1%时,土壤重金属总环境风险削减率达到74.12%。EDTA对土壤中Cu和Cd的洗脱效果较好,后续钝化修复作用有限,Pb和Zn则可通过淋洗/钝化联合修复大幅度提高削减环境风险削减率。     

新型絮凝剂含硼聚硅铝铁的制备和性能研究

向聚硅酸中引入Al³⁺、Fe³⁺、B，制得稳定性更好的高效絮凝剂含硼聚硅铝铁（PFASB）。通过实验得到其最佳配比为：n_(B)/n_(Si)=0.16、n_(Fe)/n_(Al)=0.5 、n_(Al+Fe)/n_(Si)=1。对造纸废水和焦化废水进行混凝实验表明，PFASB的除浊、除COD的能力均优于聚合铝、聚合铝铁和聚硅铝铁，而且矾花产生迅速，矾花粗大密实，是一种性能优异的新型高分子絮凝剂。实验还考察了絮凝剂的形貌和结构，结果表明B、铝及其水解产物、铁及其水解产物和聚硅酸等多种组分之间有相互作用，形成了尺度更大的聚集单元。PFASB的这种特殊结构是其具有良好稳定性和混凝性能的根本原因。     

Fe3O4/Ag磁性纳米颗粒去除水中的铅离子

采用水相共沉淀法制备小尺寸磁性Fe₃O₄纳米颗粒,以没食子酸作为还原剂和表面修饰剂,还原Ag[(NH₃)₂]⁺制备出Fe₃O₄/Ag磁性纳米颗粒。研究该磁性纳米颗粒对水溶液中铅离子的吸附行为,研究结果表明,pH为7.0,吸附温度30℃时可得到最好的处理效果,铅的去除率可达99.7%以上,Fe₃O₄/Ag颗粒吸附行为符合二级动力学模型(R² > 0.99)。该磁性纳米颗粒经过多次再生处理后,仍具有很好的吸附效果,表明Fe₃O₄/Ag在水处理方面拥有良好的应用前景。     

MWNTs及MWNTs/TiO2对水中1,2,3-三氯苯的吸附特性研究

采用批量平衡实验，对比研究了多壁碳纳米管（MWNTs）及多壁碳纳米管/二氧化钛复合材料（MWNTs/TiO₂）对水中1,2,3-三氯苯的吸附特性。结果表明，在相同条件下，MWNTs及MWNTs/TiO₂对1,2,3-三氯苯（1,2,3-TCB）的最大吸附量分别为71.8 mg/g和3.05 mg/g，pH值在2~11之间变化时，两者的吸附均不受pH值变化的影响。2种吸附剂的吸附过程均符合拟二级动力学方程，但MWNTs/TiO₂对1,2,3-TCB的吸附速率常数为0.4159 g/(mg·min)，约为MWNTs的50倍左右，说明MWNTs/TiO₂具有更强的吸附驱动力。1,2,3-TCB在2种吸附剂上的吸附过程均可用Freundlich吸附等温线来描述，其热力学参数吉布斯自由能△G⁰均为负、标准焓变△H⁰与熵变△S⁰均为正表明，MWNTs及MWNTs/TiO₂吸附1,2,3-TCB过程为自发吸热反应。与MWNTs相比，MWNTs/TiO₂具有可光催化再生的优点，能用于被污染水体的原位修复。     

原位水解生成的羟基氧化铁凝聚吸附除磷效能与机制简

将不同摩尔比Fe³⁺与OH^-（[Fe³⁺]：[OH^-]=1：0、1：1、1：2和1：3）反应获得原位水解生成的羟基氧化铁（in situ FeO_xH_y），研究了具有不同水解程度的羟基氧化铁对凝聚吸附除磷效能与机制。研究显示，In situ FeO_xH_y对磷的去除率随铁投量增大而升高，且均在中性pH范围内具有最佳除磷效果；在相同铁投量条件下，磷去除率随着[OH^-]：[Fe³⁺]的升高而降低；当体系碱度较低时（pH<6），引入OH^-可促进Fe³⁺水解而提高除磷效果。4种羟基氧化铁均可在15 s内可快速吸附磷，且吸附过程符合准二级动力学模型；Freundlich模型均可很好地描述磷在4种羟基氧化铁表面的吸附行为。磷酸盐吸附后，In situ FeO_xH_y表面Zeta电位明显降低，且[Fe³⁺]：[OH^-]为1：0的羟基氧化铁降低最为显著。结合MINITEQ计算软件磷酸盐、铁盐形态分析结果显示，对于碱度较低的体系，通过投加一定量OH^-可促进Fe³⁺水解，进而使得其更易与水中H₂PO₄^-与HPO₄^2-结合，生成具有多核羟基的磷酸铁络合物，进而提高除磷效果。     

TiO2纳米管催化活性再生处理技术简

采用H₂O₂、Fe₂（SO₄）₃和Fenton溶液对失活的TiO₂纳米管进行再生处理，重点考察了3种溶液的浓度和处理时间等对再生效果的影响，初步分析了经处理后TiO₂纳米管催化活性得到再生或增强的机理。结果表明，经H₂O₂溶液处理后TiO₂催化活性能得到有效再生，经Fe₂（SO₄）₃和Fenton溶液处理后其催化活性不仅得到再生，还能显著增强，这与H₂O₂和Fenton的强氧化作用，及进入TiO₂纳米管的Fe³⁺的阻止电子-空穴对再复合作用有关。     

O3/BAF工艺系统中有机物生物降解数学模型

研究臭氧预氧化/曝气生物滤池（O₃/BAF）联合工艺深度处理实际城市污水二级出水过程中，后续BAF系统中有机物的生物降解数学模型。以有机底物浓度、填料层高度两个基本变量为控制条件，研究BAF的总体运行常数和填料特性常数,得出BAF有机物生物降解动力学方程为S_e/S₀=exp(－Kh/qSⁿ₀)。出水与进水COD浓度比值（S_e/S₀）的对数与反应器填料高度（h）之间可表达成一次函数关系。在不同的进水浓度（S₀）下，根据ln（S_e/S₀）~h和关系式m=K/qSⁿ₀，得到方程ln(q_m)=－nln(S₀)+lnK。BAF总体运行常数K和填料特性常数n分别为1.708和0.5063。该模型对BAF工艺有如下指导意义：可以根据设计流量、进水有机物浓度和出水浓度，初步确定BAF的尺寸（如横截面积、高度等）。     

不同高级氧化法对水中低浓度药物甲硝唑降解过程的比较

采用UV、H₂O₂、UV/H₂O₂、Fenton、UV/Fenton和UV/TiO₂方法，对水中低浓度的药物甲硝唑进行降解。通过HPLC和UV-Vis光谱得到的甲硝唑去除率。详细讨论了Fe²⁺、TiO₂和H₂O₂的初始浓度以及溶液的初始pH值对降解效率的影响。结果表明，UV/Fenton和UV/TiO₂ 2种系统对水中低浓度甲硝唑均有很好的去除效果，但前者的光催化效率更高。在甲硝唑浓度=6 μmol/L，H₂O₂和Fe²⁺的初始浓度分别为0.5 mg/L和2.94 μmol/L，pH=4的条件下，UV/Fenton方法对甲硝唑水溶液光催化的最佳效率为95.8%。     

不同纳米修复剂对污染土壤中胡萝卜吸收、转运Cd的影响

通过盆栽实验研究不同纳米修复剂(羟基磷灰石HAP、赤泥RM、Fe3O4、胡敏酸-Fe3O4)对2种不同污染土壤Cd吸收、转运的影响。结果表明,上述纳米修复剂均可显著增加胡萝卜植株生物量,显著提高植株Cd胁迫的耐受指数;不同土壤施用不同纳米修复剂均显著降低胡萝卜植株Cd的含量,并且随着修复剂施加浓度的增加而显著降低;与对照相比,植株茎叶Cd含量最大降低达78.8%,根中Cd的含量最大降低67.8%;添加不同修复剂能不同程度地降低了土壤中Cd的转运系数和富集系数,这可能与施用不同纳米修复剂促进了土壤中非残留态Cd向残留态Cd的转化有关,总体而言,不同纳米型修复剂对降低Cd的有效性顺序为:RM～HAP>胡敏酸-Fe3O4>Fe3O4。     

Combined effects of titanium dioxide and humic acid on the bioaccumulation of cadmium in Zebrafish

The combined effects of titanium dioxide (TiO₂) nanoparticles and humic acid (HA) on the bioaccumulation of cadmium (Cd) in Zebrafish were investigated. Experimental data on the equilibrium Cd bioaccumulation suggest that only the dissolved Cd effectively contributed to Cd bioaccumulation in HA solutions whereas both the dissolved and TiO₂ associated Cd were accumulated in TiO₂ or the mixture of HA and TiO₂ solutions, due likely to the additional intestine uptake of the TiO₂-bound Cd. The equilibrium Cd bioaccumulation in the mixed system was comparable to that in the corresponding HA solutions, and significantly lower than that in the corresponding TiO₂ solutions (n = 3, p < 0.05). The presence of either HA or TiO₂ (5-20 mg L⁻¹) in water slightly increased the uptake rate constants of Cd bioaccumulation whereas combining HA and TiO₂ reduced the uptake rate constants.     

Effects of municipal solid waste compost and mineral fertilizer amendments on soil properties and heavy metals distribution in maize plants (Zea mays L.)

Soil amendments based on crop nutrient requirements are considered a beneficial management practice. A greenhouse experiment with maize seeds (Zea mays L.) was conducted to assess the inputs of metals to agricultural land from soil amendments. Maize seeds were exposed to a municipal solid waste (MSW) compost (50 Mg ha⁻¹) and NPK fertilizer (33 g plant⁻¹) amendments considering N plant requirement until the harvesting stage with the following objectives: (1) determine the accumulation of total and available metals in soil and (2) know the uptake and ability of translocation of metals from roots to different plant parts, and their effect on biomass production. The results showed that MSW compost increased Cu, Pb and Zn in soil, while NPK fertilizer increased Cd and Ni, but decreased Hg concentration in soil. The root system acted as a barrier for Cr, Ni, Pb and Hg, so metal uptake and translocation were lower in aerial plant parts. Biomass production was significantly enhanced in both MSW and NPK fertilizer-amended soils (17%), but also provoked slight increases of metals and their bioavailability in soil. The highest metal concentrations were observed in roots, but there were no significant differences between plants growing in amended soil and the control soil. Important differences were found for aerial plant parts as regards metal accumulation, whereas metal levels in grains were negligible in all the treatments.     

Influence of electrical fields (AC and DC) on phytoremediation of metal polluted soils with rapeseed (Brassica napus) and tobacco (Nicotiana tabacum)

The combined use of electrokinetic remediation and phytoremediation to decontaminate soil polluted with heavy metals has been demonstrated in a laboratory-scale experiment. The plants species selected were rapeseed and tobacco. Three kinds of soil were used: un-contaminated soil from forest area (S1), artificially contaminated soil with 15 mg kg⁻¹ Cd (S2) and multi-contaminated soil with Cd, Zn and Pb from an industrial area (S3). Three treatment conditions were applied to the plants growing in the experimental vessels: control (no electrical field), alternating current electrical field (AC, 1 V cm⁻¹) and direct current electrical field (DC, 1 V cm⁻¹) with switching polarity every 3 h. The electrical fields were applied for 30 d for rapeseed and 90 d for tobacco, each experiment had three replicates. After a total of 90 d growth for rapeseed and of 180 d for tobacco, the plants were harvested. The pH variation from anode to cathode was eliminated by switching the polarity of the DC field. The plants reacted differently under the applied electrical field. Rapeseed biomass was enhanced under the AC field and no negative effect was found under DC field. However, no enhancement of the tobacco biomass under the AC treatment was found. The DC field had a negative influence on biomass production on tobacco plants. In general, Cd content was higher in both species growing in S2 treated with AC field compared to the control. Metal uptake (Cd, Cu, Zn and Pb) per rapeseed plant shoot was enhanced by the application of AC field in all soils.     

Characterization of endophytic Rahnella sp. JN6 from Polygonum pubescens and its potential in promoting growth and Cd,Pb, Zn uptake by Brassica napus

Microbe-assisted phytoremediation has been considered as a promising measure for the remediation of heavy metal-polluted soils. In this study, a metal-tolerance and plant growth-promoting endophytic bacterium JN6 was firstly isolated from roots of Mn-hyperaccumulator Polygonum pubescens grown in metal-contaminated soil and identified as Rahnella sp. based on 16S rDNA gene sequence analysis. Strain JN6 showed very high Cd, Pb and Zn tolerance and effectively solubilized CdCO₃, PbCO₃ and Zn₃(PO₄)₂ in culture solution. The isolate produced plant growth-promoting substances such as indole-3-acetic acid, siderophore, 1-aminocyclopropane-1-carboxylic deaminase, and also solubilized inorganic phosphate. Based upon its ability in metal tolerance and solubilization, the isolate JN6 was further studied for its effects on the growth and accumulation of Cd, Pb and Zn in Brassica napus (rape) by pot experiments. Rape plants inoculated with the isolate JN6 had significantly higher dry weights, concentrations and uptake of Cd, Pb and Zn in both above-ground and root tissues than those without inoculation grown in soils amended with Cd (25 mg kg^?1), Pb (200 mg kg^?1) or Zn (200 mg kg^?1). The isolate also showed a high level of colonization in tissue interior of rapes. The present results demonstrated that Rahnella sp. JN6 is a valuable microorganism, which can cost-effectively improve the efficiency of phytoremediation in soils contaminated by Cd, Pb and Zn.     

Allocation and source attribution of lead and cadmium in maize (Zea mays L.) impacted by smelting emissions

Plants grown in contaminated areas may accumulate trace metals to a toxic level via their roots and/or leaves. In the present study, we investigated the distribution and sources of Pb and Cd in maize plants (Zea mays L.) grown in a typical zinc smelting impacted area of southwestern China. Results showed that the smelting activities caused significantly elevated concentrations of Pb and Cd in the surrounding soils and maize plants. Pb isotope data revealed that the foliar uptake of atmospheric Pb was the dominant pathway for Pb to the leaf and grain tissues of maize, while Pb in the stalk and root tissues was mainly derived from root uptake. The ratio of Pb to Cd concentrations in the plants indicated that Cd had a different behavior from Pb, with most Cd in the maize plants coming from the soil via root uptake.     

Response of antioxidant enzymes in Nicotiana tabacum clones during phytoextraction of heavy metals

Background, aim, and scope  Tobacco, Nicotiana tabacum, is a widely used model plant for growth on heavy-metal-contaminated sites. Its high biomass and deep rooting system make it interesting for phytoextraction. In the present study, we investigated the antioxidative activities and glutathione-dependent enzymes of different tobacco clones optimized for better Cd and Zn accumulation in order to characterize their performance in the field. Main features  The improved heavy metal resistance also makes the investigated tobacco clones interesting for understanding the plant defense enzyme system in general. Freshly harvested plant material (N. tabacum leaves) was used to investigate the antioxidative cascade in plants grown on heavy metal contaminated sites with and without amendments of different ammonium nitrate and ammonium sulfate fertilizers. Materials and methods  Plants were grown on heavily polluted soils in north-east Switzerland. Leaves were harvested at the field site and directly deep frozen in liquid N₂. Studies were concentrated on the antioxidative enzymes of the Halliwell–Asada cycle, and spectrophotometric measurements of catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), superoxide dismutase (SOD, EC 1.15.1.1), glutathione peroxidase (GPX, EC 1.11.1.9), glutathione reductase (GR, EC 1.6.4.2), glutathione S-transferase (GST, EC 2.5.1.18) were performed. Results and discussion  We tried to explain the relationship between fertilizer amendments and the activity of the enzymatic defense systems. When tobacco (N. tabacum) plants originating from different mutants were grown under field conditions with varying fertilizer application, the uptake of cadmium and zinc from soil increased with increasing biomass. Depending on Cd and Zn uptake, several antioxidant enzymes showed significantly different activities. Whereas SOD and CAT were usually elevated, several other enzymes, and isoforms of GST were strongly inhibited. Conclusions  Heavy metal uptake represents severe stress to plants, and specific antioxidative enzymes are induced at the cost of more general reactions of the Halliwell–Asada cycle. In well-supplied plants, the glutathione level remains more or less unchanged. The lack of certain glutathione S-transferases upon exposure to heavy metals might be problematic in cases when organic pollutants coincide with heavy metal pollution. When planning phytoremediation of sites, mixed pollution scenarios have to be foreseen and plants should be selected according to both, their stress resistance and hyperaccumulative capacity.     

Evaluation of metal mobility, plant availability and immobilization by chemical agents in a limed-silty soil

Metal-contaminated soils in the vicinity of industrial sites become of ever-increasing concern. Diagnostic criteria and ecological technologies for soil remediation should be calibrated for various soil conditions; actually, our knowledge of calcareous soil is poor. Silty soils near smelters at Evin (Pas de Calais, France) have been contaminated by non-ferrous metal fallout and regularly limed using foams. Therefore, the mobility, bioavailability, and potential phytotoxicity of Cd, Pb and Zn, were investigated using single soil extractions (i.e. water, 0.1 n Ca(NO(3))(2), and EDTA pH 7), and vegetation experiments, in parallel with a biological test based on (iso)-enzymes in leaves and roots, before and following soil treatment with chemical agents, i.e. Thomas basic slags (TBS), hydrous manganese oxide (HMO), steel shots (ST) and beringite. No visible toxicity symptoms developed on the above-ground parts of ryegrass, tobacco and bean plants grown in potted soil under controlled environmental conditions. Cd, Zn and Pb uptake resulted in high concentrations in the above-ground plant parts, but the enzyme capacities in leaves and roots, and the peroxidase pattern indicated that these metal concentrations were not phytotoxic for beans as test plants. The addition of chemical agents to the soil did not increase biomass production, but treatment with either HMO, ST or beringite markedly decreased the mobility of Cd, Zn and Pb. These agents were proven to be effective in mitigating the Cd uptake by plants. HMO and ST decreased either Pb or Zn uptake by ryegrass. TBS was effective in lowering Pb uptake by the same species. Beringite decreased Cd uptake by beans. If fallout could be restricted, the metal content of food crops in this area should be lowered by soil treatment. However, the differences in Cd uptake between plant species were not suppressed, regardless of the type of agents applied to the soil.     

Chemical methods and phytoremediation of soil contaminated with heavy metals

The effects of chemical amendments (calcium carbonate (CC), steel sludge (SS) and furnace slag (FS)) on the growth and uptake of cadmium (Cd) by wetland rice, Chinese cabbage and wheat grown in a red soil contaminated with Cd were investigated using a pot experiment. The phytoremediation of heavy metal contaminated soil with vetiver grass was also studied in a field plot experiment. Results showed that treatments with CC, SS and FS decreased Cd uptake by wetland rice, Chinese cabbage and wheat by 23-95% compared with the unamended control. Among the three amendments, FS was the most efficient at suppressing Cd uptake by the plants, probably due to its higher content of available silicon (Si). The concentrations of zinc (Zn), lead (Pb) and Cd in the shoots of vetiver grass were 42-67%, 500-1200% and 120-260% higher in contaminated plots than in control, respectively. Cadmium accumulation by vetiver shoots was 218 g Cd/ha at a soil Cd concentration of 0.33 mg Cd/kg. It is suggested that heavy metal-contaminated soil could be remediated with a combination of chemical treatments and plants.