土壤镉吸附的研究进展

综述了土壤镉吸附的机理和土壤pH、有机质含量、粘粒矿物类型及含量、土壤溶液中竞争性阳离子、共存阴离子、土壤温度等土壤性质对土壤镉吸附的影响；总结了土壤镉的吸附量随土壤pH增加、温度升高及有机质、铁锰氧化物和粘土矿物含量增加而增加的机理；竞争性阳离子的存在抑制镉的吸附，土壤溶液中共存阴离子对镉吸附的影响取决于阴离子种类和土壤类型。     

有机酸对铝氧化物吸附磷的影响

以存在不同配位阴离子 (硫酸根、磷酸根、草酸根、柠檬酸根 )时合成的铝氧化物为对象 ,用平衡吸附法研究了草酸、柠檬酸等的浓度和 pH对铝氧化物吸附磷的影响 ,并讨论有机酸影响磷吸附的机制。结果表明 :六种合成铝氧化物的最大吸磷量 (Xm)介于 0.189～ 0.838mmol/g ,以Al(OH)x的吸磷量最高 ,铝 柠檬酸复合物 (Al-CA)的吸磷量最低 ;有机酸浓度升高时 ,铝氧化物的吸磷量降低 ,且柠檬酸的影响程度高于草酸 ;先加 pH为 2的草酸或酒石酸 ,Al(OH)x对磷的次级吸附量最低 ,而有机酸pH为 3时 ,Al(OH)x对磷的次级吸附量达最高 ,有机酸溶液 pH由 4增至 9,铝氧化物吸磷量变化不大或逐渐降低。有机酸与磷混合加入同单加磷相比 ,pH 3时差异较小 ,pH 4～ 6时差异最显著 ,pH 7～ 8时又减小 ;有机酸降低铝氧化物吸磷量的机理包括酸性溶解和络合竞争两方面 ,在 pH 2时以前者为主 ,pH 3～ 9时以后者为主 ,且铝氧化物表面的吸附点位对供试配位阴离子都是亲合的     

镉砷复合污染土壤钝化材料研究进展

我国土壤重金属污染严重,尤以镉砷污染最为突出。镉砷复合污染土壤中各元素间表现为拮抗和协同等作用,其有效态含量受土壤pH变化和氧化还原电位等的影响,增加了镉砷复合污染土壤的修复难度,严重威胁我国粮食安全。综述了常见的镉砷复合污染土壤钝化修复材料的优缺点及其对镉砷复合污染土壤钝化修复效果和机理。常见的钝化材料有生物质炭类、磷酸盐类、金属及其氧化物类、含硅类材料、黏土矿物类、有机肥类和新型材料等。有大量研究表明生物质炭材料对镉有良好的吸附效果,为了同时钝化镉砷,通常使用改性生物质炭或与其他材料配合施用,常见的改性/配施材料有金属及其氧化物、黏土矿物、家禽粪便、复合肥等,其钝化反应机制包括离子交换、共沉淀和表面络合等;磷酸盐类主要与铁盐或铁粉配施,通过吸附和同晶替代钝化镉、点位竞争机制钝化砷;金属及其氧化物类多与生物质炭、石灰和黏土矿物等配施,通过专性吸附和共沉淀钝化镉、氧化还原和络合作用等钝化砷;铁硅肥、硅钙肥、硅钾肥等通过共沉淀钝化镉、专性吸附和点位竞争机制钝化砷;黏土矿物中多施用海泡石,主要与金属氧化物和钙镁磷肥等配施,通过离子交换、沉淀和络合反应钝化镉砷;污泥和动物粪便中含有腐殖化程度较高的有机质,主要通过吸附、氧化还原和有机络合以及微生物作用钝化镉砷;此外,富含巯基和氨基、谷聚多以及富含硫和硒的物质也可有效钝化镉砷。本文对镉砷复合污染土壤钝化修复材料进行总结,归纳了镉砷钝化材料特性,以期为镉砷复合污染土壤修复提供一定的指导。     

阳离子与金霉素在土壤中竞争吸附的研究

<正>有研究表明,不同土壤对金霉素的吸附能力存在差异。同时其Kf值与土壤吸附平衡溶液pH之间显著负相关[1]。作为两性抗生素,金霉素在不同土壤溶液pH下的解离状态或存在状态不同,其随介质pH不同而呈阳离子、一价阴离子、二价阴离子或兼性离子状态,从而导致了其在4种不同类型土壤中的吸附差异。     

As(Ⅲ)在可变电荷土壤中的吸附与氧化的初步研究

用一次平衡法研究了两种可变电荷土壤与As(Ⅲ)之间的吸附和氧化还原反应。结果表明,当As(Ⅲ)溶液平衡浓度由0·25上升到1·0mmolL-1,砖红壤对砷的吸附量由15·0增加至25·9mmolkg-1,红壤由7·6增至13·0mmolkg-1,砖红壤对砷的吸附量约为红壤的2倍,这是因为前者铁、铝氧化物的含量高于后者。在pH3~7范围内,土壤对As(Ⅲ)的吸附量随pH的增加而增加。砖红壤中的氧化锰能将As(Ⅲ)氧化为As(V),砷的氧化量在pH3~7范围内随体系pH的增加而减小。砷在红壤中的氧化反应不显著。用1·0molL-1的KNO3对吸附性砷进行解吸的结果表明,砷的解吸率在35%以下,说明大部分砷通过形成内圈型表面络合物为土壤所吸附。在pH2~7范围内,砷的解吸率随吸附体系pH的升高而增加,说明较高pH下外圈型表面络合物的比例增加。     

土壤中砷吸附机理及其影响因素研究进展

土壤中砷(As)的生物可利用性、迁移、转化及归宿在很大程度上依赖于其在土壤中的吸附反应.本文首先概述了土壤中As污染物的主要形态、价态及其与吸附的关系,较为系统地介绍了土壤中As吸附的主要影响因素和土壤中As吸附机理等方面的最新研究进展,并重点对X-射线吸收精细结构光谱(XAFS)、红外光谱(IR)等现代分析技术和方法在As吸附研究中的应用和进展进行了论述.由于土壤组分与结构的复杂性,As在环境介质中的吸附机理研究目前仍集中在单纯矿物上的吸附行为,为As在土壤中的吸附研究提供了理论基础.X-射线吸收精细结构光谱及红外光谱研究结果证明As在土壤中的吸附主要与含Fe、Al等矿物结合,形成以双齿双核结构为主的配位结构;其吸附机理与土壤矿物及As污染物的价态、吸附浓度等有关,主要包括表面络合反应和表面沉淀作用:但是土壤中As吸附机理研究还需要进一步深入研究.文章最后分析了有关土壤中As吸附研究的发展趋势和重要动向.     

土壤腐殖质-矿物质交互作用的机制及研究进展

腐殖质、氧化物、层状硅酸盐矿物间的相互作用主要通过阴离子交换、配体表面交换、疏水作用、熵效应、氢键作用及阳离子桥键、静电作用等多种结合键能进行.影响有机-矿质复合体相互作用的主要因素是腐殖质、粘土矿物的性质及溶液pH值和离子强度等.矿物的比表面积、表面酸碱反应位、表面电荷以及腐殖酸的羧基、酚羟基、醇羟基、羰基、氨基等官能团含量和酸度、芳香性、干湿状况、分子大小等基本性质都会影响腐殖酸被矿物吸附的状况.矿物对腐殖酸的吸附量随着pH值的升高而降低,随着离子强度的增加而升高.本文针对土壤腐殖质、铁/铝氧化物、层状硅酸盐矿物相互作用的机制及其影响因素进行了综述.     

四种典型重金属污染对土壤吸附磷的影响

以空白土壤和人工制备的不同浓度铜、砷、镉和铅污染土壤为对象,研究了在不同pH值、温度和柠檬酸浓度条件下重金属污染对土壤吸附磷的影响,并对其进行了相关过程的等温和吸附动力学的机理分析。研究结果表明,空白土壤和As污染土壤吸附磷的等温吸附过程符合Temkin方程,Cu、Pb、Cd污染土壤吸附磷的等温吸附过程符合Freundlich方程,空白土壤和重金属污染土壤吸附磷的动力学过程均符合Elovich方程;重金属污染对土壤吸附磷有一定的抑制作用,抑制程度与污染物浓度呈现显著的正相关,且随外在环境因子的改变而不同。当重金属元素铜、铅、砷、镉的含量分别为200、80、25、0.8 mg kg^-1时:pH值为5时,重金属对土壤吸附磷抑制作用最小,土壤吸附磷量分别降低了30.18%、13.54%、30.74%、37.23%,其抑制作用程度为:Cd> As> Cu> Pb;土壤吸附磷量与温度呈现显著的正相关,温度变化为25~45℃时,土壤对磷的吸附量分别增大了17.14%~28.83%、6.72%~16.05%、8.68%~9.13%、10.30%~23.45%,同一条件下重金属对土壤吸附磷抑制作用程度为Cu> Cd> As> Pb;重金属污染土壤吸附磷量与柠檬酸浓度成负相关,柠檬酸浓度为50 mg L^-1时,土壤吸附磷量分别降低了19.87%、21.94%、23.18%、24.84%,相同柠檬酸浓度下其抑制作用程度为Cd> As> Pb> Cu。     

低分子量有机还原性物质与土壤的相互作用 Ⅱ. 低分子量有机还原性物质与土壤作用的化学反应

论述了有机还原性物质与土壤作用的吸附、氧化还原和络合反应。土壤对该类物质的吸附量达加入量的60%～75%,其中强、弱还原性有机物质各约占1/2。负电荷物质的吸附量随土壤铁、锰氧化物及其所带负电荷量而变,并表现为电性吸附。对含—COOH、—C—NOH2功能团物质的吸附佐证了固相表面存在络合作用;在氧化-还原平衡中该类物质作为电子供体还原了铁、锰而自身被氧化;络合态亚铁、亚锰的形成服从络合-离解平衡,有机配位体的数量和H+离子争夺配位体的络合基可对其产生强烈的影响。     

金属离子在铁(氢)氧化物与腐殖质微界面上的吸附机理和模型研究进展

铁(氢)氧化物和腐殖质是广泛分布在土壤中的重要天然活性物质,因其具有较大的比表面积并且铁(氢)氧化物表面的-OH与腐殖质表面的-COOH、-OH等活性官能团可通过静电作用、配体交换等多种机制对重金属离子产生较强吸附,从而影响重金属离子在环境中的迁移、转化和生物效应。深入了解重金属离子在铁(氢)氧化物-腐殖质复合体微界面相互作用的分子机理,对于阐明重金属离子在环境中的迁移、转化过程具有重要意义。本文综述了金属离子在铁(氢)氧化物与腐殖质上吸附机理和模型的研究进展,为重金属污染土壤的风险评估和控制提供理论依据。     

土壤中砷的来源及迁移释放影响因素研究进展

砷是一种高致癌风险的类金属,自然环境中高砷(As)含量可对人类和生态系统构成直接的健康威胁。研究自然环境中砷的来源、存在形式及影响因素有助于进一步理解环境中砷的迁移转化规律,降低人体摄入砷的风险。对文献的分析表明,铁锰氧化物矿物的还原性溶解、黄铁矿及其他硫化物矿物的氧化溶解、铝氢氧化物表面的砷还原、有机质抑制砷吸附以及Eh降低和pH升高是造成砷向环境迁移的主要原因。本文综述了环境中砷的来源及其向环境迁移的多种影响因素,分析了这些因素与砷之间的作用机制,以期为加强砷污染治理提供科学依据。     

Sorption und Wirkung von Arsen auf die mikrobielle Aktivität von Waldhumusformen

Arsenate adsorption and effects of arsenate pollution on microbial activity of different types of humus soils Perfusion experiments using Na₂HAsO₄ were carried out in order to investigate adsorption and effects of arsenate on microbial activity of L-, O-, and A-horizons of a mull, a moder, and a mor soil. Arsenic adsorption of mineral A-horizons was positively influenced by their contents of amorphous Al- and Fe-oxides. It is assumed that arsenic was mainly precipitated as Al-, Mn- or Ca-arsenate in the organic layers during the perfusion experiments. The Freundlich equation was valid to describe As-adsorption of all layers under investigation. Microorganisms seemed to be very tolerant to arsenate pollution. Soil respiration and enzyme activities were reduced when liquid concentrations exceeded 8 μg As/ml. Extremely high As-additions (up to 10 mg As/g) did not reduce microbial processes to a greater degree than lower ones of 0,5 mg As/g.     

Minerals controlling arsenic distribution in floodplain soils

As a consequence of intensive mining of the western Erzgebirge since medieval times, floodplain soils of the Mulde river contain large concentrations of arsenic (As) (>50 mg kg⁻¹). Arsenic in soil is often bound to poorly crystalline Fe and Mn (hydr)oxides, which may dissolve under reducing conditions. Part of the As may also exist in primary minerals, predominately sulphides, or in secondary minerals formed upon weathering. In order to better understand the impact of seasonal flooding, we surveyed As‐bearing mineral phases, especially of iron (Fe) (hydr)oxides. Because Fe (hydr)oxides are clay‐sized, soil samples were fractionated into six particle‐size fractions. The fractions were digested with aqua regia for determination of total element concentrations, extracted with hydroxylammonium chloride (NH₃OHCl; selective for Mn (hydr)oxides and NH₄ oxalate), and analysed by X‐ray diffraction and scanning electron microscopy. The largely similar distribution of As and lead (Pb) suggested the potential co‐existence of the two elements in primary or secondary mineral phases. However, neither As–Pb minerals nor any other As mineral were detected. Association with Mn oxides was negligible. The predominant As‐bearing phases were poorly crystalline Fe (hydr)oxides, which also incorporated large amounts of Pb and were affected by redox dynamics.     

土壤中砷的生物转化及砷与抗生素抗性的关联

砷是一种广泛存在于自然环境中毒性较强的类金属元素,农田生态系统中的植物(尤其水稻)很容易吸收积累土壤环境中的砷。植物中的砷沿食物链向高等动物传递,威胁人类健康。除土壤本身的理化性质外,土壤中砷的生物转化也强烈影响砷的生物有效性。目前研究发现异化砷酸盐(As(V))呼吸性还原、细胞质As(V)还原、亚砷酸盐(As(III))氧化、As(III)甲基化和有机砷的去甲基化在土壤砷的生物地球化学过程中起重要作用。随着分析化学和分子生物学技术的进步,最新研究发现土壤生物也参与了砷糖、砷糖磷脂、砷甜菜碱、砷代草丁膦、硫代砷等有机砷的合成,其中三价一甲基砷和砷代草丁膦可作为新型抗生素,但其合成机制及生态学功能有待进一步研究。本文还详细介绍了为适应复合污染环境微生物通过自身的进化对抗生素和重金属形成的四种共选择抗性机制:共抗性,交叉抗性、共调控和生物膜感应,特别提出了土壤中砷污染与抗生素抗性相关联这一新的研究方向。最后对砷生物转化和砷与抗生素共抗机制的未来研究方向做了展望。     

Arsenic Chemistry in Soils: An Overview of Thermodynamic Predictions and Field Observations

Published information, both theoretical and experimental, on As chemical behavior in soils is reviewed. Because of many emission sources, As is ubiquitous. Thermodynamic calculations revealed that As(V) species (HAsO ₄ ^2- >H₂AsO ₄ ^- at pH 7) are more abundant in soil solutions that are oxidized more than pe+pH>9. Arsenic is expected to be in As(III) form (HAsO ₂ ⁰ =H₃AsO ₃ ⁰ >AsO ₂ ^- =H₂AsO ₃ ^- at pH 7) in relatively anoxic soil solutions with pe+pH<7. Adsorption on soil colloids is an important As scavenging mechanism. The adsorption capacity and behavior of these colloids (clay, oxides or hydroxides surfaces of Al, Fe and Mn, calcium carbonates, and/or organic matter) are dependent on ever-changing factors, such as hydration, soil pH, specific adsorption, changes in cation coordination, isomorphous replacement, crystallinity, etc. Because of the altering tendencies of soil colloids properties, adsorption of As has become a complex, empirical, ambiguous, and often a self contradicting process in soils. In general, Fe oxides/hydroxides are the most commonly involved in the adsorption of As in both acidic and alkaline soils. The surfaces of Al oxides/hydroxides and clay may play a role in As adsorption, but only in acidic soils. The carbonate minerals are expected to adsorb As in calcareous soils. The role of Mn oxides and biogenic particles in the As adsorption in soils appears to be limited to acidic soils. Kinetically, As adsorption may reach over 90% completion in terms of hours. Precipitation of a solid phase is another mechanism of As removal from soil solutions. Thermodynamic calculations showed that in the acidic oxic and suboxic soils, Fe-arsenate (Fe₃(AsO₄)₄)₂) may control As solubility, whereas in the anoxic soils, sulfides of As(III) may control the concentrations of the dissolved As in soil solutions. In alkaline acidic oxic and suboxic soils, precipitation of both Fe- and Ca-arsenate may limit As concentrations in soil solutions. Field observations suggest that direct precipitation of discrete As solid phases may not occur, except in contaminated soils. Chemisorption of As oxyanions on soil colloid surfaces, especially those of Fe oxide/hydroxides and carbonates, is believed to a common mechanisms for As solid phase formation in soils. It is suggested that As oxyanions gradually concentrate on colloid surfaces to a level high enough to precipitate a discrete or mixed As solid phase. Arsenic volatilization is another As scavenging mechanism operating in soils. Many soil organisms are capable of converting arsenate and arsenite to several reduced forms, largely methylated arsines which are volatile. These organisms may generate different or similar biochemical products. Methylation and volatilization of As can be affected by several biotic (such as type of organisms, ability of organism for methylation, etc.) and abiotic factors (soil pH, temperature, redox conditions, methyl donor, presence of other ions, etc.) factors. Information on the rate of As biotransformations in soils is limited. In comparison to the biologically assisted volatilization, the chemical volatilization of As in soils is negligible.     

铁铝氧化物–层状硅酸盐矿物互作对Cr (Ⅵ)和As (Ⅴ)吸附的影响

以高岭石、蒙脱土、针铁矿和三水铝石四种单一典型土壤矿物以及针铁矿-蒙脱石和三水铝石-蒙脱石（质量比为1:1）两种代表性土壤矿物复合体为吸附材料，采用吸附平衡实验、能谱分析（(EDS）、红外光谱、扫描电镜、酸碱滴定和zeta电位测定等方法，研究了铁铝氧化物与层状硅酸盐矿物之间的相互作用对Cr(Ⅵ)和As(Ⅴ)吸附的影响及其机制。吸附平衡实验和EDS实验结果表明，两种复合体对Cr(Ⅵ)和As(Ⅴ)的吸附容量均小于其两种组成矿物单一体系吸附量的平均值，即铁铝氧化物与蒙脱石的互作降低了这些氧化物对Cr(Ⅵ)和As(Ⅴ)的吸附能力。表面性质表征结果表明，与蒙脱石复合后，针铁矿与三水铝石表面的正电荷均被完全中和，电荷符号发生反转。与理论值相比，三水铝石-蒙脱石复合体的表面位点总浓度无明显变化，比表面积减小。针铁矿-蒙脱石复合体的比表面积与理论值无明显差异，但矿物表面位点浓度减小，表面羟基红外吸收峰强度减弱。氧化物与层状硅酸盐矿物互作改变了矿物表面性质，这可能是导致氧化物对Cr(Ⅵ)和As(Ⅴ)的吸附能力降低的主要原因。当评估污染元素在土壤中有效性时应当考虑土壤固相组分间的互作对离子吸附的影响。     

Legacy Arsenic Pollution of Lakes Near Cobalt,Ontario, Canada: Arsenic in Lake Water and Sediment Remains Elevated Nearly a Century After Mining Activity Has Ceased

Century old mine tailings in the Cobalt and Silver Center areas are widely dispersed throughout the terrestrial and aquatic environments and contain high concentrations of arsenic. Arsenic concentrations were found to be as high as 972 μg/L in surface waters and 10,800 mg/kg in lake sediment. The mean values for arsenic in surface waters and sediment from 9 lakes directly influenced by mining activity were 431 μg/L and 1704 mg/kg, respectively, whereas in the 12 control lakes with no mining activity in their catchment had mean values of 2.2 μg/L and 11 mg/kg in their water and sediment, respectively. Lakes impacted by downstream tailing migration (n?=?4) were also assessed and had intermediate concentrations of arsenic. Principal component analysis identified contaminated lakes as having different geochemical signatures than control lakes but lake sediment that was sampled below tailings in contaminated lakes, deposited pre-mining, can resemble the geochemistry of those found in control lakes. Arsenic concentrations in these samples ranged from 4.4 to 185 mg/kg, which can be considered reasonable background as these areas contained abundant mineral deposits that could naturally elevate background concentrations. Even though background concentrations are naturally elevated, the presence of arsenic-rich tailings in these lakes has prevented any natural recovery from occurring. Fe-Mn oxides at the water-sediment interface perpetually scavenge arsenic from buried tailings below and from contaminated surface waters that cause arsenic concentrations to remain enriched in the upper sediments even after tailings have been buried by lake sediment. This process has prevented recovery of the lake ecosystems even after nearly a century without mining.     

基于不同分析方法研究磷酸根在矿物表面吸附机制的进展

磷素是植物生长必需的营养元素,也是联系生态系统中生物与非生物作用的关键元素。对磷酸根在矿物表面吸附反应机制的深入认识,有助于了解其在陆地和水环境中的形态、迁移、转化和生物有效性。本文主要综述了磷酸根在常见(土壤)矿物表面吸附机制的研究进展。各种分析技术或方法,如OH–释放量分析、Zeta电位分析(电泳迁移率测试)、等温滴定量热法、原子力显微镜、X射线光电子能谱、红外光谱、核磁共振波谱、X射线吸收光谱、表面络合模型、量子化学计算等,均以不同方式揭示磷酸根在不同矿物体系的吸附机制。磷酸根在矿物(尤其是铁、铝氧化物)表面的吸附通常伴随着水基和羟基的交换。一般认为磷酸根在矿物表面主要形成双齿双核、单齿单核内圈络合物,且受pH的影响较大。pH以及磷酸根在矿物表面的吸附密度影响内圈络合物的质子化状态。在低pH、高磷浓度、较高反应温度、较长吸附时间,以及弱晶质矿物吸附等条件下矿物表面吸附的磷可在矿物表面转化形成含磷的表面沉淀,造成矿物溶解转化以及磷生物有效性的进一步降低。最后展望了磷酸盐在矿物-水界面吸附有关的研究热点和方向。     

改性磁性荔枝皮对水及果汁中砷的吸附效果及动力学分析

为探索安全高效实用的果汁类食品砷吸附材料,以天然植物副产物荔枝皮为材料,通过共沉法制备砷吸附材料磁性荔枝皮(magnetic litchi peel,MLP),采用电感耦合等离子体质谱法测定砷含量,以砷清除率为判断指标,研究了MLP对三价砷和五价砷吸附效果及机理。结果表明:改性MLP表面含有粉末状的Fe3O4,与未改性荔枝皮相比部分官能团增加,表面粗糙、更加凹凸不平,结构疏松,微孔数量增加,有利于吸附作用的进行,在砷浓度为0.20 mg/L水溶液中三价砷和五价砷吸附率为88%和90%,对苹果汁中的三价砷和五价砷吸附率为83%和93%;MLP对三价砷和五价砷溶液吸附等温线符合Langmuir等温线模型,拟合决定系数R2均大于0.99,为单分子层吸附,在298 K条件下饱和吸附量三价砷为0.181 mg/g,五价砷为0.225 mg/g;MLP对砷溶液吸附动力学可以通过准二级吸附动力学模型描述,R2均高于0.99;MLP对三价砷和五价砷的吸附过程中吉布斯自由能小于0,吸附反应是自发进行的,焓变小于0,MLP对两种价态砷的吸附都是放热反应。研究结果可为改性荔枝皮在果汁类食品中砷脱除方法和工艺的应用提供理论与数据参考。