水钠锰矿(Birnessite)对Mn2+持留机理的研究

本试验研究了一种合成水钠锰矿对Mn²⁺的持留机理和Mn²⁺被吸附后的去向,并进一步探讨了三种锰盐溶液(MnSO₄,MN(NO₃)₂和MnCl₂)对水钠锰矿晶体结构变化的影响。.试验结果表明,水钠锰矿对MN²⁺离子的吸附包括专性吸附和非专性吸附。随着吸附后的老化过程,吸附在矿物表面的锰逐渐扩散到晶格内,其置换性随之降低。.在MnSO₄,Mn(NO₃)₂和MnCl₂溶液中,水钠锰矿最终转化成六方锰矿(Nsutite),一种比水钠锰矿更稳定,结晶更好的晶体。MnSO₄溶液在加入水钠锰矿后pH值比其它两种溶液高,除生成六方锰矿外还形成大量拉锰矿(Ramsdellite)。随着生成新矿物的老化,最初被吸附的Mn被固定在晶格内而失去其置换性和生物有效性。     

含Ni六方水钠锰矿的表征及其对Pb 2+ (Zn2+)环境行为的影响

六方水钠锰矿是土壤中普遍存在、活性最强的氧化锰矿物。它常常富集各种过渡金属如Ni等,对其地球化学行为具有重要影响。在六方水钠锰矿形成过程中加入Ni2+,Ni以+2价存在于矿物中。进入水钠锰矿结构中的Ni大部分以[NiO6]八面体形式存在于层内;部分Ni存在于八面体空位上下方。含Ni水钠锰矿沿c轴方向堆叠锰氧八面体层数逐渐减小,而a-b板面晶体大小没有明显变化,即层片状晶体逐渐变薄,比表面积显著增大。随着Ni含量的增加,水钠锰矿结构中锰氧八面体空位数减少,而层边面吸附位点数基本保持不变,其对重金属离子(Pb2+/Zn2+)吸附去除能力逐渐降低。本文为明确过渡金属离子(Ni)对土壤中氧化锰矿物的形貌、结构及其性质的影响提供了参考。     

Pb2+在不同锰氧化度水钠锰矿表面配位形态的EXAFS研究

采用X-射线吸收精细结构光谱(XAFS)研究了Pb2+在不同锰氧化度的水钠锰矿表面的吸附形态,通过比较其吸附形态的差异,进一步探讨Pb2+在水钠锰矿表面的吸附机理。结果表明,锰氧化度高的水钠锰矿对Pb2+的吸附容量较大。Pb2+邻近存在一个Pb-O配位壳层和两个Pb-Mn配位壳层,对于相同锰氧化度的水钠锰矿,当Pb2+吸附量低时(600 mmol kg-1),Pb-O配位壳层中的氧原子与Pb2+的配位数为3.1,与Pb2+的距离为0.227 nm,两个Pb-Mn配位壳层的锰原子与Pb2+的配位数分别为2.8、6.1,与Pb2+的距离分别为0.357、0.377 nm;当Pb2+的吸附量增大时(2 344 mmol kg-1),其配位环境发生畸变,拟合得到的Pb-O配位壳层中的氧原子与Pb2+的配位数减少为1.2,与Pb2+的距离为0.226 nm;两个Pb-Mn配位壳层的锰原子与Pb2+的配位数分别减少为1.0、2.8,与Pb2+的间距分别为0.356、0.375 nm。Pb2+在不同锰氧化度水钠锰矿表面的吸附形态基本相同,皆存在三种吸附形态,一是与八面体空位形成三齿共角配合物,二是与水钠锰矿层结构u轴方向层边面形成单齿共角配合物,三是与结构a或b轴方向层边面形成双齿共角配合物。     

几种土壤中铁锰结核的重金属离子吸附与锰矿物类型

土壤与水体中的锰氧化物对某些重金属离子有强烈的富集作用 ,本研究表明我国几种土壤铁锰结核中锰氧化物的重金属离子 (Pb、Cu、Zn、Co、Ni和Cd)吸附量占结核吸附这些离子总量的 60 %～ 1 0 0 %。结核中所含锰矿物类型不同 ,对重金属离子吸附的能力不一样。山东砂姜黑土中含钙锰矿和锂硬锰矿 ,其锰氧化物的重金属离子吸附量最高 ;其次是湖北黄棕壤和黄褐土中铁锰结核的锰氧化物 ,它们为锂硬锰矿与水钠锰矿组合 ;吸附量最低的是湖南红壤中铁锰结核的锰氧化物 ,它们仅为锂硬锰矿。上述几种锰矿物构造上的差异和结晶程度不同是导致不同土壤铁锰结核中锰氧化物吸附重金属离子量不一样的重要原因。Co2 在吸附过程中被氧化及试样中氧化锰含量和Mn(Ⅳ )百分率不同也是影响其铁锰结核中Co吸附量变化的原因。     

含Ni六方水钠锰矿的表征及其对Pb 2+ (Zn2+)环境行为的影响

六方水钠锰矿是土壤中普遍存在、活性最强的氧化锰矿物。它常常富集各种过渡金属如Ni等,对其地球化学行为具有重要影响。在六方水钠锰矿形成过程中加入Ni²⁺,Ni以+2价存在于矿物中。进入水钠锰矿结构中的Ni大部分以[NiO₆ ]八面体形式存在于层内;仅有小部分Ni存在于八面体空位上下方。含Ni水钠锰矿沿c轴方向堆叠锰氧八面体层数逐渐减小,而a-b板面晶体大小没有明显变化,即层片状晶体逐渐变薄,比表面积显著增大。随着Ni含量的增加,水钠锰矿结构中锰氧八面体空位数减少,而层边面吸附位点数基本保持不变,其对重金属离子(Pb²⁺/Zn²⁺)吸附去除能力逐渐降低。本文为明确过渡金属离子(Ni)对土壤中氧化锰矿物的形貌、结构及其性质的影响提供了参考。     

水钠锰矿对Cr(Ⅲ)离子的吸附解吸及氧化行为

采取等温吸附热力学方法,探讨了锰氧化合物(水钠锰矿)对Cr(Ⅲ)离子的吸附解吸和氧化特征及温度、pH等因素对其影响。研究结果表明,随着Cr(Ⅲ)初始加入量的增加,总铬吸附量逐渐增大,用Langmuir方程可以很好地描述吸附等温线数据;达到反应平衡时,水钠锰矿对Cr(Ⅲ)离子的氧化量与加入初始Cr(Ⅲ)的浓度呈极显著线性正相关,而水钠锰矿对Cr(Ⅲ)的氧化率,随初始Cr(Ⅲ)浓度增加而减小;温度是影响水钠锰矿对Cr(Ⅲ)的吸附和氧化的重要因素,35℃时的吸附量显著低于25℃时的吸附量,而35℃时的氧化量、氧化率明显高于25℃时的氧化量、氧化率,表明升温对吸附反应不利,而对氧化反应有利;溶液酸度对于Cr(Ⅲ)的吸附和氧化有着不同的影响,随着pH的升高,Cr(Ⅲ)离子氧化量、氧化率增大,然而,水钠锰矿对总Cr的吸附量则随着pH的升高而减小,表明pH的升高有利于氧化反应,而对吸附反应不利。     

不同氧化度六方水钠锰矿的结构研究

通过反复试验法(trial-and-error)粉末X射线衍射(XRD)结构模拟和X射线吸收光谱(XAS)研究了不同锰平均氧化度(manganese average oxidation state,Mn AOS)六方水钠锰矿的结构变化特点.合成的系列六方水钠锰矿中(样品HB1到HB6),Mn AOS由3.92减小为3.67,晶胞参数b由2.838 (A)增加至2.848 (A).在a-b平面上的紧密堆叠尺寸(CSD)由12.0 nm减小至7.0 nm,沿c轴堆叠的锰氧八面体层数约为10.6～13.4层.随着Mn AOS逐渐降低,样品中八面体空位含量由18％减小至8％.Mn AOS与空位含量呈极显著正相关,它们与晶胞参数b呈负相关.X射线吸收近边结构光谱(XANES)线性拟合表明,样品中Mn主要以+4价存在,随着空位含量的减少,低价锰(Mn2+/3+)含量逐渐增多.扩展X射线吸收精细结构光谱(EXAFS)全多重散射模型拟合分析表明,不同氧化度六方水钠锰矿样品的晶体结构和Mn局域配位环境基本相同.由于空位含量和颗粒尺寸减小,从HB1到HB6的表观锰位点占有率(focc)由0.74减小至0.66.随着Mn AOS逐渐降低,Mn-Mn(O)配位壳平均键长增加.     

水钠锰矿提高红壤性水稻土N2O释放速率和氨氧化细菌amoA基因丰度

  【目的】  土壤中的氧化亚氮 (N₂O) 来源于硝化与反硝化作用,锰可与硝化或反硝化作用产物反应产生N₂O或氮气,已有研究表明土壤中锰含量高会影响硝化作用。因此,本试验以水钠锰矿 (KMnO₂·H₂O) 与土壤硝化作用与反硝化作用的生物化学耦合反应为切入点,研究水钠锰矿的添加对土壤N₂O释放速率及微生物的影响,进一步认识N₂O释放与土壤环境因子的相互关系。  【方法】  以红壤性水稻土为供试土壤,通过微宇宙培养试验,在土壤中添加不同质量百分比的水钠锰矿 (0%、0.1%、0.3%、0.7%、1.5%),预培养7 天后,加入硫酸铵N 100 mg/kg继续培养14天。在培养第1、3、7、14天,采用气密性注射器抽取10 mL气体样品,气相色谱仪测定N₂O含量;同时取土壤样品,比色法测定铵态氮与硝态氮含量。培养结束时,测定土壤pH,采用实时荧光定量PCR测定土壤16S rDNA与氨氧化细菌 (AOB) amoA基因拷贝数,高通量测序技术分析微生物群落组成及多样性。  【结果】  水钠锰矿提高了土壤N₂O释放速率,增加了土壤N₂O累积释放量,以添加0.1%水钠锰矿的N₂O累积释放量最高,添加1.5%的最低。土壤铵态氮含量随培养时间的延长而迅速降低,硝态氮含量则迅速增加。水钠锰矿显著提高了土壤pH与表观N₂O产量 (N₂O-N/NO₃?-N),pH随着水钠锰矿添加量的增加整体提高,N₂O-N/NO₃?-N则随着水钠锰矿添加量的增加呈降低趋势。适量水钠锰矿显著增加了土壤细菌16S rDNA与氨氧化细菌 (AOB) amoA基因拷贝数,并显著提高了土壤16S rDNA与AOB amoA基因拷贝数的比值,但随着水钠锰矿添加量的增加,细菌16S rDNA和AOB amoA基因拷贝数的增加量整体降低;放线菌、变形菌与拟杆菌是所有处理中的优势菌门,通过非度量多维尺度分析发现不同处理间的微生物群落结构差异显著,未添加水钠锰矿处理与添加水钠锰矿1.5%处理的微生物群落结构差异最大,其他处理的微生物群落结构介于两者之间。  【结论】  土壤中添加0.1%质量比的水钠锰矿,可以通过增加AOB的数量促进红壤性水稻土N₂O的释放,显著影响微生物物种丰度与群落结构。但水钠锰矿高添加量处理对AOB的刺激作用减弱,因此,应将土壤锰含量作为影响土壤N₂O释放的因素加以考虑。     

几种土壤锰结构对Cr（Ⅲ）的氧化与锰矿物类型

以几种土壤锰结核为实验材料，研究了不同氧化锰对Cr(Ⅲ）的氧化特性。结果表明，供试锰结核对Cr(Ⅲ）的氧化能力大小顺序为N1－1＞N4－1＞N2－1＞N5－1，与他们所含量还原性锰含量顺序不一致。换算的还原性锰对Cr(Ⅲ）的氧化后，则其顺序为N4－1＞N2－1＞N1－1＞N5－1。由组成供试锰结核的主要氧化锰矿物得知，对Cr(Ⅲ）的氧化能力：钠水锰矿＞锂硬锰矿＞钙锰矿。这可能与氧化锰矿物的结晶程度、晶体构造和Mn(Ⅳ）含量的差异以及Cr(Ⅲ）在氧化锰表面的吸附位置有关。     

土壤胡敏酸与锰离子的络合特征及生物有效性研究

试验从沈阳农业大学棕壤肥效长期定位实验田中选择8个处理:(1)对照(CK);(2)低量氮肥(N1);(3)氮磷肥(N1P);(4)氮磷钾肥(N1PK);(5)低量有机肥(M1);(6)低量有机肥+氮肥(M1N1)(7)低量有机肥+氮磷化肥(M1NP);(8)低量有机肥+氮磷钾肥(M1N1PK),采用田间与盆栽试验相结合的方法,对土壤胡敏酸与锰离子的络合特征及生物有效性进行了研究。研究结果表明,各施肥处理均可提高土壤HA与Mn2+的络合稳定常数,其中,有机无机配合施用处理大于单施化肥处理,氮磷钾配施处理大于氮磷或单施氮肥处理;HA-Mn2+趋与形成1∶1型络合物,施用有机肥增加了土壤HA对Mn2+的吸附数量和吸附强度,施用化肥降低土壤HA对Mn2+吸附的数量,增加其吸附强度。水培试验的结果证实,源于单施化肥处理的土壤HA对玉米Mn2+的吸收影响不显著,而来自有机肥各处理的土壤HA降低了玉米的吸锰量。络合稳定性指标和吸附强度指标与玉米吸锰量呈显著负相关关系,可以用来作为评价养分有效性的指标。     

Pb<Superscript>2+</Superscript> adsorption on birnessite affected by Zn<Superscript>2+</Superscript> and Mn<Superscript>2+</Superscript> pretreatments

Purpose  

Lead contamination is ubiquitous, and much attention has been paid due to its toxicity. The phyllomanganate birnessite is the most common Mn oxide in soils. The MnO₆ octahedral layers may have significant Mn vacancies in the hexagonal birnessites. Among heavy metal ions, birnessites possess the greatest adsorption affinity and capacity for Pb²⁺. The aim of this study was to understand the relationship between vacant Mn octahedral sites and Pb²⁺ adsorption.     

Forms and Uptake of Manganese in Relation to Soil Taxonomic Orders in Alluvial Soils of Punjab,India

Different forms of manganese (Mn) were investigated, including total, diethylenetriamine penta-acetic acid (DTPA) extractable, soil solution plus exchangeable (Mn), Mn adsorbed onto inorganic sites, Mn bound by organic sites, and Mn adsorbed onto oxide surfaces, from four soil taxonomic orders in northwestern India. The total Mn content was 200–950 mg kg^?1, DTPA-extractable Mn content was 0.60–5.80 mg kg^?1, soil solution plus exchangeable Mn content was 0.02–0.80 mg kg^?1, Mn adsorbed onto inorganic sites was 2.46–90 mg kg^?1, and Mc adsorbed onto oxide surfaces was 6.0–225.0 mg kg^?1. Irrespective of the different fractions of Mn their content was generally greater in the fine-textured Alfisols and Inceptisols than in coarse-textured Entisols and Aridisols. The proportion of the Mn fractions extracted from the soil was in the order as follows: Adsorbed onto oxide surfaces > adsorbed onto inorganic site > organically bound > DTPA > soil solution + exchangeable. Based on coefficient of correlation, the soil solution plus exchangeable Mn, held onto organic site and oxide surface (amorphous) and DTPA-extractable Mn, increased with increase in organic carbon of the soil. The two forms, adsorbed onto inorganic site (crystalline) and DTPA extractable, along with organic carbon, increased with increase in clay content of the soil. DTPA-Mn and Mn adsorbed onto oxide surfaces and held on organic site decreased with increased with an increase in calcium carbonate and pH. Total Mn was strongly correlated with organic carbon and clay content of soil. Among the forms, Mn held on the organic site, water soluble + exchangeable and adsorbed onto oxide surface were positively correlated with DTPA-extractable Mn. DTPA-extractable Mn seems to be a good index of Mn availability in soils and this form is helpful for correction of Mn deficiency in the soils of the region. The uptake of Mn was greater in fine-textured Inceptisols and Alfisols than in coarse-textured Entisols and Aridisols. Among the different forms only DTPA-extractable Mn was positively correlated with total uptake of Mn. Among soil properties Mn uptake was only significantly affected by pH of the soil.     

Selenite adsorption by a variety of oxides

Abstract

Selenite adsorption by a variety of oxides consisting of iron (Fe), aluminum (Al), titanium (Ti), manganes (Mn), and silicon (Si), and by two humic acids were investigated in order to grasp selenite behavior and fixation mechanisms in soil. It was found that selenite was apparently adsorbed even by the Mn oxides on which surface negative charge was dominant in normal pH range (pH <4). No selenite adsorption was observed in the silicon dioxide (SiO₂) and the two humic acids. A sequential extraction of adsorbed selenite with competitive anions showed the differences of binding force or stability of adsorbed selenite among the minerals. While the goethite fixed selenite strongly, selenite adsorbed on the Mn oxide was easily released to the liquid phase with other anions, such as phosphate. Each mineral had its inherent characteristic in ligand exchange reactions accompanied with selenite sorption. Selenite sorption by the Mn and the Ti oxides resulted in large increase of surface negative charge, while only a little increase in the Fe and Al oxides. Proton consumption with selenite sorption was extremely smaller for the Mn oxide than for the others.     

Soils in the semi-arid area of the El Melah Lagoon (NE Tunisia) — Variability associated with a closing evolution

Soils of the semi-arid area of the El Melah coastal lagoon (NE Tunisia), with a closing evolution dynamic, were studied aiming: (1) the chemical and mineralogical characterization of surface and subsurface layers of soil profiles from locations previously submerged and of soils developed on dunes; (2) to evaluate the dependence on the environment conditions of the geochemical patterns of the soils; and (3) to determine chemical and mineralogical variations with the emersion of the sediments resulting from the decrease in the extent of the area permanently covered by water in the lagoon. The compositional results obtained showed significant differences depending on the environment (littoral plain, old dunes and sandy spit), but soils of the different environmental zones studied do not appear to be significantly polluted as far as trace elements are concerned. Among the elements studied, high element/Sc ratios and variations were found for As, Sb and Zn. Antimony is more concentrated in coarser samples suggesting its adsorption in Fe or Mn oxides coating quartz grain surfaces. Arsenic and zinc may be incorporated into the carbonates structure, as well as adsorbed on, or coprecipitated with, iron oxides. Zinc may also be significantly incorporated in clay minerals. Iron was found to be more oxidized in the cultivated soil from the old dune strand; and more reduced in the sandy spit where ankerite occurs suggesting the reduction of Fe³⁺ in oxide/hydroxides by microorganisms and incorporation of Fe²⁺ in carbonates. REE patterns, particularly the HREE/LREE are correlated with carbonates, indicating preferential incorporation of the HREE in carbonates, and of the LREE in clay minerals/iron oxides. High Ga contents were found in soils and sediments rich in clay minerals/Al, suggesting its incorporation in clay minerals structure. Therefore, Ga may be used as an indicator of the clay minerals proportion in sediments and soils. Carbonates, sulphates, besides Fe and/or Mn oxides and clay minerals, appear to play an important role on the trace elements distribution.     

Adsorption,activity, and kinetics of acid phosphatase as influenced by selected oxides and clay minerals

Abstrac

The effects of 3 oxides (Fe, Al, and Mn oxides) and 3 clay minerals (kaolin, montmorillonite, and allophane) on the adsorption and subsequent kinetic properties of acid phosphatase were compared. The amount of enzyme adsorbed by the oxides and clay minerals followed the order: montmorillonite ? kaolin > Mn oxide > Fe oxide > Al oxide ? allophane. The adsorption isotherms of the enzyme on the oxides and clay minerals, except for montmorillonite and allophane, fitted the Langmuir equation. The activity of the enzyme immobilized by the inorganic components studied was in the order of allophane > kaolin > Fe oxide > montmorillonite > Al oxide ≒ Mn oxide. Compared to the free enzyme, the V _max, K_m, and V _max / K _m values of the immobilized enzyme decreased, increased, and decreased, respectively. Among the oxides or clay minerals, the higher the ability of the inorganic components to adsorb the enzyme, the lower the value of the V _max / K _m ratio of the immobilized enzyme. These findings suggest that the catalytic efficiency of the enzyme complexes formed is determined by the adsorbability of the inorganic components for the enzyme.     

不同氧化物硼负载体吸附锰离子的特性研究

以人工合成针铁矿（Goethite，简写为G），水锰矿（Manganite，简写为M），经硼砂处理的吸附态针铁矿（简写为Ad—B-G），吸附态水锰矿（简写为Ad—B-M），经硼酸处理的包被态针铁矿（简写为Oc—B—G），包被态水锰矿（简写为Oc-B—M）等6种氧化物为研究对象，在等温条件下，用吸附平衡法研究了6种硼负载体对Mn^2＋的吸附解吸行为。结果表明，吸附Mn^2＋能力：Oc—B—G〉Ad—B—G〉G；Ad—B—M和Oc—B—M吸附Mn^2＋量最大，M吸附能力最弱。6种硼负载体Mn^2＋吸附量随pH升高而增加,但铁氧化物和锰氧化物之间有差别。不同形态锰氧化物吸附Mn^2＋前后溶液pH变化不同，吸附等量Mn^2＋离子时，Ad—B—M向溶液中释放H^＋量最多，Oc—B—M最少。上述结果说明，硼的参与不仅可改变氧化物吸附Mn^2＋离子的行为，而且对反应体系的影响也不尽相同。     

THE ASSOCIATION OF MANGANESE AND COBALT IN SOILS—FURTHER OBSERVATIONS

Soil Mn was mineralized either as birnessite or lithiophorite in five out of seven widely distributed soils taken from Bermuda, Europe, and the Middle East countries. The majority of the soil Co was associated with these minerals. This agrees with earlier work on Mn in Australian soils and suggests that these two minerals are the most common soil forms of secondary Mn minerals.