纳米Fe、Si降解黄褐土中PCB77

采用振荡培养实验研究了纳米Fe0、纳米Si0和纳米Fe3O4对黄褐土中PCB77的降解作用。结果表明,土壤中PCB77投加量为20 mg kg-1,仅投加纳米Fe0时,投加量为40 mg g-1,反应24 h后PCB77含量接近最低,纳米Fe0对灭菌和未灭菌土壤中的PCB77降解过程均符合一级反应动力学,反应速率常数Kobs分别为0.0057 h-1和0.0081 h-1;反应64h后,反应体系中PCB77残留率分别为68.2%,和53.2%,可见灭菌土壤较未灭菌土壤中PCB77降解效果降低。纳米双元体系能促进PCB77的降解,当纳米Si0:纳米Fe0=1∶10时,土壤中PCB77降解效果最好,反应64h后,土壤中PCB77残留率仅为53%,当纳米Fe3O4∶纳米Fe0=1∶4时,土壤中PCB77降解效果较佳,反应64h后,土壤中PCB77残留率仅为42.5%。土壤中PCB77降解产物中除联苯外未发现其他降解产物,可能是PCB77在纳米Fe0表面连续脱氯的原因造成的。     

纳米Fe^0与微生物协同降解土壤中PCB77

以红壤、黄褐土和砂姜黑土为供试土壤,以3,3′,4,4′-四氯联苯（PCB77）为目标化合物,进行了纳米Fe0、微生物以及联合体系降解土壤中PCB77的动力学研究。结果表明,土壤中PCB77自然降解率低,投加纳米Fe0和微生物均能显著加快土壤中PCB77降解速率,降解过程可用一级反应动力学方程拟合。当PCB77初始浓度为4mg·kg-1,纳米Fe0投加量为20mg·g-1,PCB77在红壤、黄褐土和砂姜黑土中反应速率常数k分别为0.0205d-1、0.0165d-1和0.0145d-1;通过富集培养的方法从污染土壤中分离出一株多氯联苯降解菌,初步鉴定该菌株为Pseudomonas sp.,当降解菌投加量为2×108cfu·g-1时,PCB77在3种土壤中反应速率常数分别为0.0136d-1、0.0094d-1和0.0124d-1;当同时投加20mg·g-1纳米Fe0和2×108cfu·g-1降解菌时,其反应速率常数分别为0.0264d-1、0.0218d-1和0.0232d-1。纳米Fe0与微生物协同降解的效果要明显优于纳米Fe0和微生物的单一体系。     

纳米Fe3O4/微生物联合体系对2,4-D和阿特拉津降解的研究

采用纳米Fe3O4/微生物联合体系降解溶液中2,4-D和阿特拉津,考察了不同2,4-D和阿特拉津初始浓度、微生物接种量、纳米Fe3O4投加量、溶液ｐＨ值等对降解效果的影响。结果表明,纳米Fe3O4/微生物联合体系对2,4-D和阿特拉津的降解率显著高于纳米Fe3O4和微生物单一体系;2,4-D和阿特拉津初始浓度在0～10 mg·L^-1、微生物接种量在0～12 mg·L^-1、纳米Fe3O4的投加量在0～200 mg·L^-1范围内,2,4-D和阿特拉津的降解率随其初始浓度、微生物接种量和纳米Fe3O4 投加量的增大而增加。溶液pH3．0左右、2,4-D和阿特拉津初始浓度10 mg·L^-1、微生物接种量12 mg·L^-1、纳米Fe3O4投加量200 mg·L^-1,是反应的最佳条件,此实验条件下反应7 d,2,4-D和阿特拉津的残留率分别降低至35．7％和54．0％。     

CeO2添加比例对Fe基催化剂催化纤维素气化制氢的影响

为研究CeO2添加对生物质催化气化制氢特性的影响，该研究采用分级气化系统分析了不同CeO2/Fe2O3比例（Ce∶Fe摩尔比为0∶1、3∶7、5∶5、7∶3、1∶0）双金属催化剂对纤维素水蒸气催化重整制氢气体产物产量、组成以及催化剂的结构演变特性的影响。结果表明，CeO2/Fe2O3催化剂在制氢反应中的催化性能明显优于纯CeO2或Fe2O3催化剂，当Ce∶Fe摩尔比为3∶7时，在800℃下氢气的最大产率为21.63 mmol/g（以纤维素计，下同）；当温度大于等于800℃时，催化剂氧化还原反应后可生成CeFeO3，且CeFeO3的存在对纤维素水蒸气气化过程有促进作用。CeO2的引入提高了催化剂的氧化性能和稳定性，提高了使用寿命。该研究对生物质气化机制的深入理解具有一定的指导意义。     

铁锰营养失衡对商陆根系分泌物的影响

以商陆为实验材料,用水培方法设置了8个实验处理:Fe0Mn0(对照),Fe0Mn-,Fe0Mn ,Fe-Mn0,Fe-Mn-,Fe-Mn ,Fe Mn0,Fe Mn-,Fe Mn 。处理30 d时,对根系分泌物中可溶性糖、总氨基酸、pH值以及根系质膜透性进行测定。结果表明,Fe-Mn-的可溶性糖含量稍高于对照,其余各处理组均低于对照,Fe0Mn ,Fe Mn 达到显著水平;氨基酸含量在铁锰失衡条件下普遍有所增加,其中Fe-Mn0分泌的氨基酸含量最大,与对照差异显著;除Fe0Mn 外,各处理组的pH值与对照组相比都显著增加,其中以铁毒处理组(Fe Mn0,Fe Mn ,Fe Mn-)的增加率最高;铁毒处理组(Fe Mn0,Fe Mn ,Fe Mn-)使商陆根系质膜透性增加,对商陆根系造成一定的伤害。总体而言,铁锰的缺乏或过量都会引起商陆根系分泌物含量的变化,其中以铁胁迫和锰毒对其影响最大;另外,相对单铁或单锰处理而言,铁锰之间的交互作用对商陆根系分泌物的变化也有一定的影响。     

玉米铁营养不服从报酬递减律的研究

试验研究不同供Fe水平对玉米幼苗Fe营养的影响结果表明 ,0～ 0 .10 μmol/LFe浓度内随Fe浓度的增加而玉米茎叶鲜物质量渐降 ,不服从矿质营养的报酬递减律 ;而 0 .10～ 10 0 μmol/LFe浓度内随Fe浓度的增加而玉米茎叶鲜物质量渐增 ;玉米根则以 0 .0 1μmol/LFe浓度处理生长量最小。 0～ 1μmol/LFe浓度内随Fe浓度的增加而玉米茎叶Fe含量渐降 ,叶片黄化渐重和叶绿素含量降低 ,尤以 1μmol/LFe浓度处理叶片黄化最重 ;1～ 10 0μmol/LFe浓度内随Fe浓度的增加而玉米叶片Fe含量渐增 ,且叶绿素含量亦增高。根内Fe含量的变化呈相同趋势 ,但致根Fe含量最低的营养液Fe浓度低于致茎叶Fe含量最低的营养液Fe浓度。而低量供Fe对玉米体内可溶性糖、氨基酸和NO-3 N含量及总Fe吸收量均比完全不供Fe处理的危害更重     

鱼嘴式穹隆格栅坝型泥石流水石分离拦挡结构

提出了一种新型的适用于稀性、黏性及过渡性大流量泥石流的水石分离结构——鱼嘴式穹隆格栅坝,其为外形类似于鱼嘴状的流线型穹隆状格栅过滤筛,基本组成为格栅坝、鱼嘴及嘴前锚、坝后基础、坝下基础、驳岸等导流设施、护坦、泄流槽,格栅坝主体为纵横向劲性骨架,格栅上覆盖柔性网加密格栅网眼。就鱼嘴式穹隆格栅坝的空间形态、结构和设计要点进行初步探讨。     

低温等离子体耦合Fe2O3催化剂去除粮食仓储环境中磷化氢

为了探究低温等离子体（Non-Thermal Plasma,NTP）耦合催化剂对粮仓中磷化氢（PH3）的去除效果,该文采用介质阻挡放电低温等离子体与催化剂耦合的反应装置,研究了NTP与Fe2O3催化剂耦合对PH3去除率的影响,并对耦合反应后的催化剂进行表征,分析产物及反应机理。结果表明,载体和催化剂与NTP耦合改变了NTP的放电状态,提高了PH3去除率;不同载体负载Fe2O3后,在输入功率超过53 W时,NTP与Fe2O3催化剂耦合对PH3去除率均高于无填充,Fe2O3/Al2O3与NTP耦合效果最好,去除效率达到了100%。耦合前后催化剂的表征结果表明,耦合反应之后,Fe2O3/Al2O3催化剂的比表面积降低了11.23%,Fe3+/(Fe2++Fe3+)含量提高了21.06%,Osur/(Olatt+Osur+Oads)含量减少了2.24%,Fe含量降低了4.69%,P含量增加了4.34倍。产物分析表明耦合后生成的主要产物为磷酸。研究结果表明NTP耦合Fe2O3/Al2O3催化剂具有很好的PH3去除效果,为粮食仓储行业去除磷化氢提供理论依据。     

泥石流梁式格栅坝拦砂性能试验研究

通过特殊泥石流试验装置 ,对泥石流梁式格栅坝拦砂性能进行研究 ,初步得到 :梁式格栅坝有全部闭塞、临时闭塞、半闭塞、未闭塞 4种闭塞类型。当梁间距 b与泥石流体中最大颗粒粒径 dm ax之比 b/ dmax≤ 1.0时 ,格栅坝基本闭塞 ;b/ dmax≥ 1.5时 ,格栅坝未闭塞 ;1.0 相似文献   

适宜操作条件提高松木屑超临界水气化制氢效果

为了解操作条件对生物质在超临界水中气化制氢过程的影响,该文以松木屑作为原料,在反应温度500℃、反应压力30 MPa、停留时间30 min、木屑质量分数8%、粒径8~16目的条件下,探索了Fe、Na2CO3、Cu SO4 3种催化剂对制氢过程的催化活性:FeNa2CO3Cu SO4。选用Fe催化剂,考察了反应压力30 MPa、停留时间30 min、反应温度(420~500℃)、木屑质量分数(8%~40%)、粒径(2~1 000目)对制氢过程的影响。试验结果表明:Fe催化剂质量分数增大,能显著提高制氢效果;随着温度的升高,气化率、碳气化率、氢气化率及氢气产量均相应增大;木屑质量分数越低,气化率和氢气化率越高;粒径对气化结果影响不大;在优化后的操作条件下(反应温度500℃、反应压力30 MPa、停留时间30 min、Fe质量分数2%、松木屑质量分数8%、粒径8~16目),H2的摩尔分数、氢气化率、氢气产量分别达到42.1%、98.1%、6.62 mol/kg。该文研究结果可为该技术今后的工业化发展和应用提供参考。     

Using Synchronous Fluorescence Technique as a Water Quality Monitoring Tool for an Urban River

This paper presents a study performed to evaluate the feasibility of implementing a series of heating rods within a zero-valent iron permeable reactive barrier (ZVI-PRB) to enhance the conventional design of PRBs, and thus to improve the barrier’s removal efficiency, and reduce construction and reactive material costs. A numerical modeling approach is undertaken where a hypothetical case is introduced and typical site values are assigned to it. The amount of electrical energy required to heat the barrier from an initial temperature, T ₁, to a final temperature, T ₂ is assessed. Through different simulation cases, the effect of (1) initial temperature of the groundwater entering the PRB, (2) different amounts of total heat injected, (3) distribution of the heating rods, and (4) different types of porous media, on the temperature increase within the PRB are evaluated. Results show that the amount of energy required to increase the temperature of our hypothetical case by 10°C is approximately 935 W, which could be provided by renewable energies such as solar. It is explained that there are multiple benefits for increasing the temperature within the PRB. Apart from boosting reaction rates, temperature increase can reduce water viscosity and increase flow within the barrier, which broadens a barrier’s catch area. It can enhance solubility of gases to reduce blockage caused by gas generation. An upward flow is formed inside the wall which can also help reduce gas blockage. By implementing heating rods, design widths are reduced, which could potentially reduce the materials (thus cost) used and/or justify the use of more expensive reactive material in PRBs. Heating the PRB was found to generate a heat plume of 20 m length downstream of the PRB after one year, which would increase biodegradation of the residual contaminants leaving the PRB within this zone. Overall, it is concluded that implementing the proposed technology within a ZVI-PRB can be justified, and is found to be beneficial in many aspects.     

Relative effects of road mortality and decreased connectivity on population genetic diversity

Roads can have two important effects on populations that impact genetic variation: reduced gene flow and reduced abundance. Reduced gene flow (“barrier effects”) due to road avoidance behavior or road mortality can lead to reduced genetic diversity because genetic drift is enhanced in fragmented populations. Road mortality can also reduce population abundance (“depletion effects”) whenever road-caused mortality outpaces recruitment, also lowering diversity even when barrier effects are inconsequential. Although roads are expected to affect both genetic diversity and fragmentation, most research focuses only on fragmentation. Furthermore, in studies that do investigate road effects on genetic diversity, correlations are usually attributed to barrier effects and little attention is paid to the potentially confounding influence of mortality-caused depletion effects. Here we investigate the relative importance of barrier and depletion effects on genetic diversity of populations separated by a road by performing coalescent simulations wherein these two road effects are varied independently. By simulating wide ranging rates of migration and population decline, we also determine how the importance of these forces changes depending on their relative magnitude. We show that the vast majority of potential variation in genetic diversity is governed by depletion (mortality) rather than barrier effects. We also show that unless migration is sufficiently high and population decline due to mortality is sufficiently low, increasing migration across roads will generally not recoup genetic variation lost due to road mortality. We argue that the genetic effects of road-mediated mortality have been underappreciated and should be more often considered before prioritizing road-mitigation measures.     

天然地形和人工沙棘风障对排土场平台植被恢复的影响

以霍林河露天煤矿为例 ,通过对排土场不同地段植被的观察、野外小区实验和室内分析的方法 ,调查研究了天然地形风障以及人工沙棘风障对半干旱地区露天煤矿排土场平台植被恢复状况的影响。研究结果表明 ,地形与人工沙棘风障不仅起到防风作用 ,还可以改善土壤理化性质 ,促进其它植物的生长 ,防治水土流失 ,加速排土场的植被恢复与生态重建的进程。     

根系分隔方式对玉米/大豆根际土壤碳含量及磷有效性的影响

【目的】豆科与禾本科间作体系中对磷有效性的影响主要集中在根系分泌物的活化作用,由根际沉淀引起的土壤碳含量与磷酸酶活性变化及其对红壤磷有效性的影响机制尚不清楚。【方法】本研究以间作玉米大豆为研究对象,设置根系完全分隔、尼龙网分隔、不分隔3种方式,在0、21.83、43.67、65.50和87.34 P mg kg-1（分别记为P0、P1、P2、P3和P4）磷肥施用水平下进行盆栽试验,研究根系分隔方式对间作玉米大豆根际土壤微生物量碳（MBC）、溶解性有机碳（DOC）、根际土壤有机碳（ROC）、酸性磷酸酶活性（ACP）、碱性磷酸酶活性（ALP）、速效磷和Hedley磷组分的影响。【结果】相比完全分隔,根系不分隔可提高玉米和大豆根际土壤MBC含量,显著降低玉米根际土壤DOC含量,低磷水平（P0、P1）时显著提高大豆DOC含量,显著提高玉米（仅在低磷时）和大豆根际土壤ACP活性,低磷时显著提高大豆根际土壤ALP活性。除玉米活性磷组分外,根系分隔方式对间作玉米大豆根际土壤速效磷、磷组分有显著或极显著影响。根系不分隔较完全分隔可通过降低大豆根际活性无机磷（Pi）(P0除外)和中活性Pi从而提高玉米根...     

PRB修复垃圾渗滤液污染地下水过程中pH值变化分析

随着城市化的不断发展,生活垃圾产生量越来越多,因管理不善,导致垃圾渗滤液污染地下水的问题越来越突出,污染地下水的修复研究迫在眉睫。实验模拟地下环境,以被垃圾渗滤液污染地下水为研究对象,分别用沸石、无烟煤、陶粒、活性炭、炉渣、粉煤灰、零价铁作为反应介质,设计了6种地下可渗透反应墙（PRB）,分别为反应器1、2、3、4、5和6。分3个阶段对PRB技术治理污染地下水中pH值影响和变化进行模拟研究,分析反应器pH值降低的原因并探讨pH值变化机理。实验结果表明,所有反应器pH值较进口降低,第三阶段出口pH值平均值较进口平均降低0.40;因水解酸化反应存在,产生一定量NH4＋和有机酸,造成反应器出水pH值降低和复合填充材料NH4＋相对去除率降低,说明PRB技术治理渗滤液污染地下水具有一定可行性,但技术方法有待继续深入研究。     

不同沙埋程度下带状沙障的防风固沙效果研究

沙障在防护过程中,易发生沙障沙埋现象。为了对比分析不同沙埋程度下沙障的防风固沙效果差异,该文通过风洞模拟和野外试验相结合的方法,研究了沙袋沙障在裸露、浅埋、深埋3种状态下,防护区近地层风流场、输沙通量等风沙运动规律,并以未设置沙障的流沙区作为对照,明确了沙埋过程中沙障的防风固沙效果变化规律。结果表明,沙障在经历裸露至深埋过程中:1)对过境气流的防护距离、防护高度逐渐减小,近地层风速廓线变化趋势与对照相同,并逐渐服从对数函数;2)沙障防护区输沙分布高度显著降低(P0.01),输沙分布高度由42 cm(裸露)降低至34 cm(浅埋),最终降至28 cm(深埋),而对照的输沙分布高度为24 cm;3)近地层输沙率分布曲线逐渐服从对数函数,0～50 cm高度范围输沙量也呈现递增趋势;4)3种埋设深度野外试验说明,经过两个风季后,裸露、浅埋、深埋的沙袋沙障防护区土壤风蚀呈现降低趋势,风蚀深度分别比对照降低了18.53%、72.97%、80.40%。研究可以为沙障高度优化及应用技术提升提供理论依据。     

基于土地利用的三峡库区生态屏障带生态风险评价

[目的]揭示三峡库区生态屏障带生态风险,为库区生态风险评估及土地利用优化提供理论依据。[方法]基于遥感影像数据,运用RS与GIS技术,计算土地利用相对合理性指数,同时构建生态风险评价模型,划分高程/坡度带定量评价三峡库区生态屏障带的生态风险情况,划分生态风险等级,并对生态风险进行空间自相关分析。[结果]较低生态风险区占比例最大,为36.77%,高生态风险区及较高生态风险区主要分布在沿长江两岸建设用地及耕地较为集中的区域,土地利用相对合理性指数随高程增高逐渐变大,随坡度增大逐渐减小,研究区生态风险空间自相关分析呈现出十分显著的局部自相关性。[结论]研究区内生态风险总体呈现较低值,沿江高值区需对土地利用进行重点优化。     

Evaluation of Natural Zeolite as a Material for Permeable Reactive Barrier for Remediation of Zinc-Contaminated Groundwater Based on Column Study

The permeable reactive barrier (PRB) filled with natural zeolite plays the role of a reactive treatment zone for remediation of contaminated groundwater. Based on column lab experiments, the volume of remediated solution, the distribution (K_d) and retardation (R_d) coefficients were evaluated, confirming successful removal and retention of zinc from contaminated groundwater. The effect of hydrodynamic dispersion on zinc capturing by zeolite in PRB was evaluated by the hydrodynamic dispersion coefficient (D_L) and retarded hydrodynamic dispersion coefficient (D_LR) using the Brigham method. For different assumed distances of the barrier, the simulation of one-dimensional zinc concentration profile from the point source through the barrier has been modeled by a simple analytical pulse model. The results show that the flow rate has the most significant effect on the concentration profile, peaks, and broadening of curves. The residence contact time (τ) corresponding to higher K_d and R_d as well as lower D_L and D_LR values outcomes the optimal range of 6.2–9.4 min. This interval corresponds to the experimental performance at the bed length of 8 and 12 cm and flow rate in the range of 6.38–9.57 PV/h. The calculated minimum thickness and longevity confirm the successful application of zeolite as a material in PRB for remediation of zinc contaminated groundwater.     

Characterization of the interaction between two food aroma components, alpha-pinene and ethyl butyrate, and ethylene-vinyl alcohol copolymer (EVOH) packaging films as a function of environmental humidity

The ethylene-vinyl alcohol copolymers (EVOHs) are well-known high oxygen barrier materials that are being used successfully in the design of packaging structures for oxygen-sensitive food or pharmaceutical products. Recently, there has been increasing interest in using EVOH materials to provide a high barrier to organic compounds as a means to reduce food aroma scalping. However, the barrier function of this family of materials diminishes significantly in humid environments, and it is supposed that so does the organic vapor barrier. In this work, a new sorption-based method to characterize the interaction between food aroma and polymer films for packaging as a function of relative humidity is presented and is used to determine the barrier to ethyl butyrate and alpha-pinene of EVOH at 23 degrees C. The results show that although EVOH is an excellent barrier to food aroma when dry, a property that even improves at low relative humidity (RH), the solubility and diffusivity of the compounds tested increase dramatically with humidity at medium to high water activities. However, even in the worst case (100% RH), EVOH outperforms low-density polyethylene (LDPE) as a barrier to organic vapors at least 500,000-fold.     

基于风洞模拟试验的典型机械防沙工程防护效益对比

为探究3种典型机械防沙工程措施实施后所体现的防护效益，通过风洞模拟试验，以敦煌黑山嘴地区的典型机械防沙工程为参考，对草方格与尼龙网格状沙障及阻沙栅栏的防风、固阻沙效益进行系统的对比分析。结果表明：草方格与尼龙网格状沙障的布设均能有效降低风速，当指示风速为20 m/s时，1.5 cm高度的风速降低率分别达到82.5%与80.9%,同时极大地增加流沙地表粗糙度，显著影响当地的风速变化；此外，两者在不同高度对风速削弱能力差异明显；草方格与尼龙网格状沙障也深刻影响当地风沙流结构，其中草方格沙障的固沙能力主要体现在近地表；阻沙栅栏前后平均输沙率降低44.2%,同时对当地流场结构影响深刻。综合分析可知，草方格与尼龙网格状沙障防风、固沙效益良好，阻沙栅栏阻沙效益显著。研究结果可为当地机械防沙工程建设提供指导，同时对其他地区防沙工程布设予以借鉴。