几种物理因素对四氧化三铁纳米颗粒在有机质存在条件下的饱和多孔介质中迁移持留行为的影响

近些年来,环境研究者对纳米颗粒的迁移性进行了部分研究,但是对环境稳定性低、反应活性高的金属氧化物工程纳米颗粒在多孔介质中的运移沉积行为的系统探讨还很不足,尤其是对其在有机质（NOM）存在条件下迁移行为的了解非常有限。本研究选用四氧化三铁磁纳米颗粒（MENPs）作为研究对象,采用填充柱淋溶实验法,对其在饱和多孔介质中的迁移持留行为展开探讨,其目的是考察几种主要介质环境物理因素对其在天然有机质存在条件下的纵向淋溶过程及其在介质中持留量的影响作用。结果显示,不利吸附条件下的MENPs集聚体在多孔介质中的吸附持留及迁移性能取决于多种合力的作用效果。其中,孔隙水流速增大时,MENPs在多孔介质中的迁移性增强,持留性减弱,持留MENPs在介质中的逐层分布随孔隙水流速改变而变化;而且,MENPs在多孔介质中的迁移持留性与介质颗粒的表面物理性质也有关,天然有机质的存在一定程度上可以改善石英砂表面的异质性。另外,介质颗粒粒径大小也是影响MENP-介质间持留机制的重要因子。当多孔介质颗粒粒径大小改变时,MENPs穿透曲线及持留分布曲线随之变化明显,MENPs的吸附沉积机制也相应有所不同。     

砂质多孔介质中土壤颗粒的迁移

通过室内模拟试验,研究了不同土壤悬液浓度和不同多孔介质组成条件下土壤颗粒在砂质多孔介质中的截留和迁出特征,以揭示土壤颗粒在砂质多孔介质中的迁移特征。结果表明,土壤颗粒在砂质多孔介质中迁移时会受到土壤颗粒粒级、浓度和介质组成的影响。截留作用在土壤颗粒通过砂质多孔介质时起主导作用,土壤颗粒截留比例随着土壤颗粒浓度的增大逐渐增加;而随着多孔介质中粗砂比例的增大,其逐渐降低。土壤总颗粒、50μm和1~50μm土壤颗粒迁出量分别与该粒级相应投入量呈幂函数增加趋势,而1μm土壤颗粒的迁出量与其投入量呈线性增加趋势。土壤总颗粒迁出量与介质中粗砂比例之间存在线性增加关系。因此,多孔介质组成、颗粒粒径和浓度在土壤颗粒迁移过程中起着重要作用,在多孔介质中土壤颗粒和污染物迁移研究方面需要充分考虑这些因素。     

胶体颗粒对不同粒径饱和多孔介质渗透性的影响

探讨胶体颗粒在多孔介质中迁移所发生的物理、化学及生物作用过程,在许多学科中具有重要的科学意义。采用室内石英砂柱实验,开展了定水头条件下不同浓度和粒径的胶体颗粒在饱和多孔介质中的运移行为研究。共使用了3种胶体粒径、3种浓度的胶体溶液和3种粒径范围的石英砂。实验表明:多孔介质的相对渗透系数K/K0(K为各时刻计算所得的渗透系数,K0为初始渗透系数)减小程度与颗粒浓度成正比;胶体颗粒越大,越易在表层沉积,而小颗粒易向下部迁移,但总体来看粒径效应没有浓度效应明显;当胶体颗粒在不同粒径的饱和多孔介质中迁移时,粒径大的多孔介质各段K/K0均有明显降低,而粒径小的只在表层变化明显。不同条件下总体相对渗透系数与时间之间呈二次方相关关系,但当多孔介质粒径较小时,相关性不显著。介质渗流流速及砂柱不同位置胶体颗粒浓度变化与介质渗透性变化相对应。用扫描电镜(Scanning Electron Microscope,SEM)进行定性表征,进一步说明胶体颗粒会堵塞多孔介质孔隙影响其渗透性。实验中发现当输入浓度C0小于0.5 g·L–1且dp/Dp>0.018(dp为胶体颗粒粒径,Dp为石英砂算数平均粒径)时,会出现多孔介质局部K/K0增大的现象。     

生物炭颗粒在饱和多孔介质中的迁移与滞留

生物炭在实际生产实践中具有许多潜在的农业和环境效益,因此受到了越来越多的关注。生物炭在多孔介质中的迁移不仅会影响它在土壤中的归趋,还可能会影响微生物群体及土壤有机质的动态变化以及被吸附的污染物对环境的影响。实验通过柱实验研究了微米级生物炭颗粒在饱和多孔介质中的迁移和滞留特性,主要选取了四种影响生物炭迁移的潜在因素:原材料、裂解温度、背景溶液pH值和离子强度。实验结果显示微米级生物炭在饱和多孔介质中具有一定的迁移能力,但是大部分的微米级生物炭会滞留在饱和多孔介质的表面和孔隙间。生物炭的制备原材料对于生物炭的表面电势特性有较大影响,从而影响了微米级生物炭在饱和多孔介质中的迁移能力。热解温度越高,生物炭的表面电势越大,迁移能力越弱。随着背景溶液离子强度增加和pH值减小,微米级生物炭颗粒在多孔介质中滞留增加,迁移能力减弱。     

有机质去除对黄土纳米颗粒悬浮液稳定性的影响

土壤纳米颗粒是有机无机复合体,研究有机质对土壤纳米颗粒体系稳定性的影响具有重要意义。以塿土和褐土纳米颗粒以及去除有机质塿土和去除有机质褐土纳米颗粒为研究对象,分别测定颗粒的粒径分布、zeta电位、临界聚沉浓度(Critical coagulation concentration,CCC)等指标,利用德查金-朗道-维韦-奥弗比克(Derjauin-Landau-Verwey-Overbeek,DLVO)理论计算颗粒的哈默克(Hamaker)常数和相互作用能。结果表明:塿土和褐土纳米颗粒的平均直径分别为94.00nm和88.20 nm,去有机质黄土纳米颗粒的平均直径则略高于100 nm;相较于黄土纳米颗粒,去有机质黄土纳米颗粒的zeta电位绝对值降低,颗粒间静电排斥势能降低;DLVO模型拟合得到塿土和褐土纳米颗粒在真空中的哈默克常数分别为6.86×10^-20 J和9.73×10^-20 J,去有机质处理后相应数值为3.14×10^-20 J和3.40×10^-20 J,后者范德华引力势能降低;去有机质黄土纳米...     

CeO2纳米颗粒催化柴油燃烧氧化特性分析

为了深入了解柴油中添加Ce O2纳米催化剂后生成颗粒的氧化特性,该文配制了Ce O2质量分数分别为0、50、100 mg/kg的纳米催化燃油,利用微粒分级采样装置采集柴油机燃用3种燃料生成的颗粒样品,采用扫描电镜研究了Ce O2质量分数对颗粒形貌特征的影响,通过热重分析方法研究了升温速率、Ce O2质量分数对颗粒氧化特性的影响并采用Coast-Redfern方法计算了颗粒的活化能。结果表明:颗粒群为团簇状结构,粒径范围在20~70 nm之间;随着Ce O2质量分数增加,颗粒平均粒径减小,粒径向小粒径方向移动,计盒维数增大。随着升温速率的增加,颗粒氧化过程出现滞后现象,氧化反应区域变宽,初始氧化温度、峰值失重温度和氧化终止温度增高,失重率峰值变小。升温速率对颗粒反应活化能影响较小。升温速率相同时,随着Ce O2质量分数的增加,颗粒的反应活化能、初始氧化温度、峰值失重温度和氧化终止温度均降低,Ce O2质量分数越高,降幅越大。Ce O2纳米催化剂添加到柴油后,使颗粒粒径变小,并能促进颗粒的氧化,降低颗粒起燃温度,可有效降低柴油机微粒捕集器(diesel particulate filter,DPF)再生温度和延长再生周期,对柴油机排气净化具有重要的意义。     

煤矸石组分与表土质地对充填重构土壤导气率的影响

研究煤矸石组分及表土质地对煤矸石重构土壤导气率的影响,探讨重构土壤这种差异显著的非均质土壤导气内在机理,为进一步研究复杂的非均质土壤导气特性提供理论基础。通过在煤矸石中掺杂不同粒径碎石来改变其组分,并利用3种不同质地的土壤在土柱内进行土壤剖面重构,采用一维瞬态法测量其导气率。结果表明:(1)不同碎石粒径和质量分数对混合基质饱和含水量影响不同,掺杂2~5mm粒径碎石,随着质量分数的增加,饱和含水量逐渐增加,从7.29%增加到12.9%;掺杂5~10mm粒径碎石,饱和含水量随着质量分数的增加先增加后减少,分别为7.28%,8.5%,6.9%。(2)煤矸石的导气率远大于土壤,并且煤矸石的导气率对水分的敏感度随质量含水量的增加而增加,而土壤的导气率对水分变化的敏感度均随质量含水量的增加而降低。(3)碎石的存在为大孔隙的产生创造条件的同时也会减少了土壤通气断面,阻隔空气传输的通道。(4)重构土壤导气率受表土质地和底部填充介质的共同影响,覆土土壤导气率决定了重构土壤的导气率大小,而充填基质导气率决定了充填介质对重构土壤导气率影响的系数(Ska)。Ska与充填介质导气率呈显著相关,可以通过指数函数进行拟合(R2=0.93)。通过充填介质及覆土土壤的导气率可以对重构土壤导气率进行估算,简化了重构土壤导气率的测定过程。     

腐殖酸和pH对典型轮胎磨损颗粒迁移行为的影响机制

轮胎磨损颗粒（tire wear particles, TWPs）作为微塑料（microplastics, MPs）的重要种类之一，当下其生态风险已受到生态学家的高度重视。通常，颗粒型污染物的环境行为过程是其生态风险的重要影响因素。然而，TWPs在土壤等多孔介质中的迁移过程及影响机制至今尚未见报道。选择冷冻破碎制备的C-TWPs（冷冻破碎轮胎磨损颗粒）以及道路磨损产生的R-TWPs（滚动摩擦轮胎磨损颗粒）和S-TWPs（滑动摩擦轮胎磨损颗粒）为典型研究对象，以石英砂柱来模拟研究TWPs在土壤等环境多孔介质中的迁移行为，并探究天然有机物腐殖酸（HA）及不同pH（4、7和10）环境对以上三种类型TWPs迁移行为的影响。结果显示：HA（50 mg?L-1）能够显著增强三种类型TWPs的迁移性，并且在HA（50 mg?L-1）存在下，不同pH（4、7和10）对TWPs迁移行为影响不同，中碱性环境（pH=7/10）更有利于TWPs的迁移。主要原因在于，HA存在或（和）中碱性环境有利于（同时）增大TWPs和石英砂颗粒表面的Zeta电位值（绝对值），此时，一方面TWPs的分散性得到改善，有较小的粒径分布，另一方面增加了TWPs和石英砂颗粒间的静电排斥力，有助于TWPs的迁移。值得注意的是，HA存在和不同pH环境条件下，低温破碎制备的C-TWPs的迁移性较R-TWPs和S-TWPs强，主要由于C-TWPs制备时携带有较多的负电荷、较小的等电点和较强的疏水性，上述性质也可促使其吸附更多的HA，从而加强其电负性；而R-TWPs和S-TWPs由于粘附了道路矿物、金属盐或灰尘而减弱以上性质，表面具有较小的电负性。研究结果揭示了不同类型TWPs在自然界中地球化学迁移行为的差异性，并暗示了研究源头性质（排放方式）以确定同种材质微塑料环境行为及生态风险内在差异的必要性。     

土壤团聚体氧化亚氮排放潜势与微生物学机制

氧化亚氮（N2O）是主要温室气体之一,土壤是N2O的重要排放源,其排放主要受N2O产生和还原的功能微生物影响。土壤团聚体是由原生颗粒（砂、粉、黏粒）、胶结物质和孔隙组成的土壤基本结构单元。土壤不同粒径团聚体之间因基质和孔隙差异形成特殊独立的微生境被视为N2O的生物化学反应器。在不同的微生境中,N2O产生和还原的功能微生物分布不同,因而土壤不同粒径团聚体N2O排放可能存在差异。目前在不同生态系统土壤全土N2O排放特征的报道较多,而对于不同粒径土壤团聚体N2O排放相对贡献尚不清楚、功能微生物分布还未知、N2O产生和还原热区尚未明确。本文综述了近年来国内外关于土壤团聚体对N2O产生和排放机制的研究,总结了土壤团聚体性状特征对N2O产生和还原的影响,阐述了不同粒径土壤团聚体对N2O排放影响的微生物学机制,进一步明确了今后需加强土壤团聚体N2O产生和还原的热区、环境因子阈值范围的确定、系列功能基因（酶）整体性的研究,以期为N2O模拟排放模型优化提供参考,为土壤N2O减排提供理论依据。     

3D格子Boltzmann传质模型模拟生物膜降解有机污水

以膜生物法有机污水处理为研究背景,将3D格子Boltzmann传质模型与多孔介质四参数随机生成法耦合,获得生物膜多孔介质详细的孔隙分布,进而对反应器内生化降解反应过程进行模拟计算。研究分析了生物膜孔隙率及孔隙分布对流动传质及生化反应性能的影响,并与试验结果比较证明了模型的可行性。结果表明:各方向生长概率p1-14=0.005,随着生物膜孔隙率增大,反应器内底物降解效率先增大后减小,且在孔隙率ε=0.5时达到最大,50.97%;孔隙率ε=0.5时,改变各方向生长概率重构获得5种不同结构生物膜,其降解效率随之改变,生物膜为结构1(p_(3-4)=0.01,p_(1,2,5-14)=0.005)时,底物降解效率最高,52.54%。因此,3D格子Boltzmann传质模型可用于膜生物反应器内的流动传质及生化反应过程的模拟,研究结果将对反应器的优化具有一定的指导作用。     

Alteration of Phytotoxicity and Oxidant Stress Potential by Metal Oxide Nanoparticles in Cucumis sativus

This study was carried out to examine the phytotoxicity and oxidant stress by CuO and ZnO nanoparticles (NPs) in Cumumis sativus and the characterization of CuO and ZnO NP suspensions. We estimated the bioaccumulation of CuO and ZnO NP in plant, reactive oxygen species enzyme (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) activities in plant tissue of root, and observed CuO and ZnO NPs with transmission electron microscopy. We found that the seedling biomass significantly decreased to 75% and 35% of that of control at 1,000?mg/L of CuO and ZnO NPs, respectively. The bioavailability and oxidant stress potential of plants exposed to metal oxide particles were dependent in the size, concentration, and species of the NPs. The median inhibition concentrations of CuO and ZnO NPs were 376 and 215?mg/L, respectively. In transmission electron microscopy, CuO and ZnO NPs greatly adhered to the root cell wall, and NPs were observed in the root cells. Another finding indicated that both CuO and ZnO NPs caused statistically significant increase in SOD, CAT, and POD activities and significant increase at 100?mg/L concentration levels. These results indicated that NPs alter both phytotoxicity and oxidative stress in plant assays. We further suggest that the oxidative stress markers appear to be a good predator of potential future toxicity of nanoparticles.     

Effects of coated and non-coated ZnO nano particles on cucumber seedlings grown in gel chamber

Zinc oxide-engineered nanoparticles (ZnO ENPs) have received the most attention in recent years. This increasing interest has been directed towards studying the environmental fate and effects of ZnO ENPs on ecological terrestrial species. In this study, ZnO NPs were synthesized by atmospheric pressure solution evaporation method and were coated or uncoated with humic acid (HA). The root uptakes of uncoated and HA-coated ZnO NPs and zinc (Zn) were investigated by gel-grown cucumber. Two ZnO levels (1 and 200 µM) were applied in the form of coated (T₃) and non-coated (T₂) NPs or bulk particles (T₁). The results showed that coating NPs by HA increases zeta potential of NPs and decreases their aggregation size due to the increase in the repulsion forces among the particles. Addition of 1 mgL^?1 ZnO into gel chamber enhanced root and shoot biomass; however, the shoot growth was higher in the presence of NPs compared to its bulk counterpart. Moreover, greater phytotoxicity of ZnO from the source of NPs than bulk particles in shoot was observed. Scanning electron microscopy results showed a clear evidence of the penetration of NPs into root cells.     

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。     

Wechselwirkungen von Mikroorganismen und Tonmineralen-eine Übersicht

Relationships Between Soil Microorganisms and Clay Minerals-a Review Clay minerals belong to the most important environmental factors in soils, influencing the composition and metabolic activity of soil microflora. Their influence on bacteria, actinomycetes and microscopic fungi is very complex and includes trophogenic relationships, cation exchange capacity, sorptive activity, osmotic and other physico-chemical effects in microbial environments. In this review, different effects of clay minerals on soil microorganisms and also the influence of microorganisms on the clay minerals are briefly discussed.     

Retention and Transport of PAH-Degrading Bacterium <Emphasis Type="Italic">Herbaspirillum chlorophenolicum</Emphasis> FA1 in Saturated Porous Media Under Various Physicochemical Conditions

Dispersal of functional microorganisms is a rate-limiting process during in situ bioremediation of contaminated soil and groundwater. In this work, series of column experiments were conducted to investigate the retention and transport behaviors of Herbaspirillum chlorophenolicum FA1, a promising bacterial agent for bioremediation, in saturated porous media under conditions of different combinations of grain size, solution pH, solution ionic strength (IS), and humic acid (HA) concentration. Experimental data showed that the mobility of FA1 in saturated porous media was strongly dependent on the physicochemical conditions. The breakthrough curves (BTCs) indicated that the amounts of FA1 in the effluent increased with increasing in sand size, solution pH, and HA concentration, but decreased with increase of solution IS. The shape of retention profiles (RPs) was hyper-exponential. The amounts of retained bacteria in the media also varied with the experimental conditions with opposite trends to that of effluent. Both experimental BTCs and RPs were simulated by a mathematical model that accounted for deposition kinetics to better interpret the effects of physicochemical conditions on FA1 deposition dynamics. Findings from this study showed that fate and transport of the functional bacterium FA1 in porous media strongly relied on the environmental conditions. Both experimental and modeling results can provide guidelines for field application of functional bacteria for soil and groundwater remediation.     

Effects of Silver Nanoparticles on Soil Ammonia-Oxidizing Microorganisms Under Temperatures of 25 and 5℃

The excellent bactericidal performance of silver nanoparticles (Ag NPs) has led to their wide applications, resulting in increasing concerns about their potential environmental impacts. This study evaluated the influences of different concentrations of Ag NPs (0, 1, 10, and 100 μg g^-1 dry soil) on the ammonia-oxidizing microorganisms in soil at cultivation temperatures of 25 and 5℃ for 37 d. The results showed that 1 μg g^-1 dry soil of Ag NPs had no acute effects on the ammonia-oxidizing microorganisms. However, 10 and 100 μg g^-1 dry soil of Ag NPs levels were found to significantly inhibit the activities of soil nitrification, with a decrease of 69.89% and 94.55%, respectively, at 25℃ and 61.65% and 83.79%, respectively, at 5℃ compared to the control (0 μg g^-1 dry soil of Ag NPs). These levels of Ag NPs also obviously decreased soil urease activity from about 380.47 ±0.07 (at 5℃) and 529.76 ±13.44 (at 25℃) mg N g^-1 dry soil d^-1 to 61.70 ±2.97 and 68.29 ±8.22 mg N g^-1 dry soil d^-1, respectively, after 37 d of cultivation. Quantitative polymerase chain reaction showed the abundance of ammonia-oxidizing archaea and bacteria. For the same exposure time, the effects of Ag NPs on the activities of ammonia-oxidizing microorganisms and urease decreased with decreasing temperature. The threshold concentration of Ag NPs that induced negative effects on ammonia-oxidizing microorganisms was higher at 5℃ than at 25℃. Therefore, the temperature has a major impact on the toxicity of Ag NPs to ammonia-oxidizing microorganisms and on the urease activity, with toxicity being reduced with decreasing temperature.     

Nanoplastic–plant interaction and implications for soil health

Nanoplastics (NPs) are accumulating in the soil environment at a rapid rate, which may cause serious consequences for ecosystems and human health. However, environmental behaviour and toxicity of NPs in the soil–plant system remain poorly understood. This review summarizes current studies on NP–plant interactions to unravel uptake mechanisms and phytotoxicity of NPs. NPs could be taken up by plant roots and transported upwards through the xylem to all organs of the plant, even to the edible parts such as the grain, thereby threatening human health. The interaction of NPs with plants affects plant transport of water and nutrients. Besides, it induces significant oxidative stress leading to inhibition of physiological and biochemical activities such as photosynthesis, and thus adversely affects plant growth and development. In addition, the co-transport of NPs with other soil pollutants may induce the combined toxic effects. This study also discussed the potential mechanism of NP–plant interactions based on previous experience with engineered nanomaterials. Finally, a comprehensive assessment of the key challenges in each area was presented, and future perspectives are offered.     

利用粘粒矿物修复重金属污染农业土壤研究进展

Heavy metal contamination of agricultural soils poses risks and hazards to humans.The remediation of heavy metal-polluted soils has become a hot topic in environmental science and engineering.In this review,the application of clay minerals for the remediation of heavy metal-polluted agricultural soils is summarized,in terms of their remediation effects and mechanisms,influencing factors,and future focus.Typical clay minerals,natural sepiolite,palygorskite,and bentonite,have been widely utilized for the in-situ immobilization of heavy metals in soils,especially Cd-polluted paddy soils and wastewater-irrigated farmland soils.Clay minerals are able to increase soil pH,decrease the chemical-extractable fractions and bioavailability of heavy metals in soils,and reduce the heavy metal contents in edible parts of plants.The immobilization effects have been confirmed in field-scale demonstrations and pot trials.Clay minerals can improve the environmental quality of soils and alleviate the hazards of heavy metals to plants.As main factors affecting the immobilization effects,the pH and water condition of soils have drawn academic attention.The remediation mechanisms mainly include liming,precipitation,and sorption effects.However,the molecular mechanisms of microscopic immobilization are unclear.Future studies should focus on the long-term stability and improvement of clay minerals in order to obtain a better remediation effect.