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;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。     

有机质和陪伴阴离子对土壤吸附Zn的影响

本文研究了土壤有机质和陪伴阴离子对黄棕壤、红壤和砖红壤吸附Zn²⁺的影响。结果表明:土壤有机质含量与吸附Zn²⁺的数量呈正相关;陪伴阴离子对土壤吸Zn²⁺量有显著的制约作用,土壤从ZnCl₂溶液中吸附的Zn²⁺数量高于Zn(NO₃)₂的0.77-1.16倍;△pH值与吸Zn²⁺量呈直线关系。由解吸情况可以判明红壤胶体表面的高能吸附位占的比例明显大于黄棕壤或砖红壤。     

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.     

土壤对铜离子的专性吸附及其特征的研究

供试土壤专性吸附铜的等温线均符合Langmuir方程。红壤吸附量最低,砖红腹与黄泥土最大吸附量相近,但在铜浓度低时砖红壤吸铜量远低于黄泥土,而在高浓度则反之。土壤专性吸附铜是在溶液中Na⁺浓度比Cu²⁺高8.3—100倍条件下,Na⁺离子仍不足以与之竞争的那些专性吸附点所吸持的铜。按其解吸条件区分为松结合铜(可为N NH₄Cl解吸)和紧结合铜(仅能为0.1 N HCl解吸)两种。紧结合铜受平衡溶液铜浓度影响很小,所占据的吸附点对Cu²⁺有较强亲和力。松结合铜则随平衡铜溶液浓度增大而增加,符合Langmuir方程。对于砖红壤和黄泥土,在铜浓度低时紧结合铜>松结合铜;浓度高时则反之。红壤专性吸附铜始终以松结合铜为主。三种土壤比较,紧结合铜是砖红壤>黄泥土>红壤;松结合铜则是黄泥土>砖红壤>红壤。造成这些差别的原因可能与土壤性质、氧化物、有机质和粘土矿物组成等不同有关。用平衡法研究三种土壤专性吸附铜在不同浓度NH₄Cl和HCl溶液中的解吸表明,可进一步区分为三或四种不同的结合状况。红壤对铜吸附容量最小,且最易解吸。     

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。     

土壤对重金属离子的竞争吸附

本文研究了理化性质不同的黄棕壤、红壤和砖红壤对Zn、Ni、Co的竞争吸附。采用含有不同重金属离子量的0.05molL^₁Ca(NO₃)₂溶液平衡,pH为5.5。结果表明,其吸附量的顺序:黄棕壤>砖红壤>红壤。对各离子的选择性为:Zn>Ni≥Co。竞争吸附的机制与非竞争吸附有明显的不同。其特征首先表现在吸附量上,竞争吸附要比非竞争吸附高得多。特别明显的,土壤去掉游离氧化铁后其吸附量不但不降,反而有不同程度的增加,Zn²⁺表现尤为突出;影响吸附量很大的陪伴阴离子作用受到严重抑制;反映土壤与重金属离子间作用能力大小的pH₅₀的变化符合吸附等温线的特点。其次根据土壤对重金属离子的吸附和解吸的情况,可以认为,红壤胶体表面吸附位数量远不及黄棕壤和砖红壤,但高能吸附位的比例高。     

浙江省灵江流域地表水化学特征及灌溉适宜性

[目的] 灵江是浙南诸河流域重要河流,在浙南一带具有典型性和代表性。分析灵江流域地表水体的水化学特征和演化机理及其灌溉适宜性,为该区域生态保护和高质量发展提供科学依据。[方法] 综合利用数理统计、Piper三线图、主成分分析和离子比等方法对流域地表水体进行水化学统计分析及成因判别;通过绘制Wilcox图和USSL图评估流域内地表水体灌溉适宜性。[结果] ① 灵江流域地表水的化学类型在空间上具有分带性。从中上游(Ⅰ区)-下游温黄平原河网区(Ⅱ区)-台州湾入海口(Ⅲ区)水化学类型从HCO₃-Ca型向Cl-Na型过渡。②Ⅰ区地表水的化学特征主要受到岩石风化作用中的硅酸盐岩溶解影响,少量受碳酸盐岩溶解影响;Ⅱ区地表水的水化学特征主要受硅酸盐岩溶解影响,Ⅲ区地表水的化学特征主要受蒸发盐岩溶解影响。③Ⅰ,Ⅱ区地表水的K⁺,Na⁺主要来源于硅酸盐矿物溶解,Ca²⁺,Mg²⁺,HCO^-₃,SO^-2₄主要受硅酸盐岩溶解,少量来源于碳酸盐岩的溶解。NO^-₃则主要来源于人类活动。④Ⅰ,Ⅱ区地表水适用于农业灌溉,Ⅲ区地表水灌溉适宜性较差,易引起盐碱害。[结论] 灵江流域地表水体的水化学组分受天然溶解及人类活动共同影响,中上游和下游温黄平原河网区地表水适宜农业灌溉,台州湾入海口地表水易引起盐碱害,在制定农业灌溉及生态保护和高质量发展规划时应予以重视。     

铝铁柱撑黏土活化单过硫酸盐降解邻苯二甲酸二乙酯的研究

邻苯二甲酸二乙酯(DEP)是地表水和土壤环境中一种常见的有机污染物,研究DEP的去除方法对于人体健康和环境安全具有十分重要的意义。蒙脱土是一种廉价易得的粘土矿物,通过将铝铁聚合阳离子引入蒙脱土的层间域可得到比表面积大和催化活性高的环境友好型催化材料-铝铁柱撑粘土(Al/Fe-PILCs)。利用XRD、BET、FTIR及HRTEM等手段对材料的理化性质进行表征,并研究了其活化单过硫酸盐(PMS)对DEP的去除效果。结果表明：在Al/Fe-PILCs活化PMS体系中,反应24 h后DEP的降解率约为92%,且反应后的溶液中未检测到溶解性Fe离子。体系中产生的强氧化性.OH是DEP降解的主要原因。同时,环境中常见的阴离子(Cl_^-, NO_3^-和CO_3^2-)不能完全抑制DEP降解。因此,在实际水体和土壤环境中Al/Fe-PILCs作为活化PMS的催化材料,具有一定的应用潜力。     

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。     

Effect of manganese-reducing rhizosphere bacteria on the growth of Gaeumannomyces graminis var. tritici and on manganese uptake by wheat (Triticum aestivum L.)

Summary Five bacterial strains capable of Mn reduction were isolated from the rhizosphere of plants growing in different South Australian soils. They differed in their Mn-reducing capacity. The antagonism of these strains compared to the imported strain 2–79 (from the United States) against Gaeumannomyces graminis var. tritici was tested in agar and in a soil sandwich experiment at different Mn²⁺ concentrations in the soil. In addition, wheat seeds were coated with the different strains and with MnSO₄ or with MnSO₄ only in order to investigate their effect on plant growth and Mn uptake. With one exception, all strains inhibited the growth of G. graminis in agar, but to different degrees. In contrast, only two strains significantly inhibited the growth of the fungus in the soil. The hyphal density was decreased more than the hyphal length. The Mn²⁺ concentration in the soil also had a marked effect on fungal growth; low Mn concentrations slightly increased while high Mn concentrations strongly decreased the fungal growth. Seed treatment with MnSO₄ only (+Mn) increased Mn uptake above that of the control (no seed treatment). Only the weakest Mn reducer on agar significantly increased plant growth and Mn uptake from soil in comparison with the Mn treatment. One strain was tested as seed coating without adding MnSO₄; it increased the plant growth to an extent similar to the Mn treatment. Increasing the Mn uptake by plants may be one of the growth-promoting effects exerted by rhizosphere bacteria.     

Effects of selected cations and anions on pK-0.5pCa values for a Mn oxide system

We studied the relative influences of Mn²⁺, Al³⁺ NO₃^? and SO₄^2? on the K-Ca relationship, as expressed by a pK-0.5pCa value, in a Mn oxide suspension system using a double indicator electrode technique. With an increase in the quantity of solution Mn²⁺ and Al³⁺ in the system, Mn²⁺ ions showed a stronger effect than Al³⁺ on increasing pK-0.5pCa values, though this was not the case when the amount of the cations added was low. The stronger effect of Mn²⁺ on the K-Ca relationship was attributed to stronger specific adsorption of the Mn²⁺ ion on the Mn oxide as compared with Al³⁺. When K⁺ and Ca²⁺ were added after the addition of Mn²⁺ and Al³⁺, activities of K and Ca in equilibrium solution were higher than those when K⁺ and Ca²⁺ were added first, indicating that the exchange reaction of the cations on the Mn oxide was not fully reversible. Compared to NO₃^? added systems, the pK-0.5pCa values for SO₄^2? added systems were lower when the initial K/Ca molar ratios were 0.5 and 2. This effect of SO₄^2? on the pK-0.5pCa values was also related to the quantity of Ca ions in the system since no significant difference in pK-0.5pCa values was observed between the SO₄^2? and NO₃^? added systems when the K/Ca molar ratio was 8. The present results revealed that both cationic and anionic environments had a profound influence on the adsorption of K and Ca and, thus, the pK-0.5pCa values in a Mn oxide system. The findings of this study help attain a better understanding of the chemistry of K in soils, particularly those with variable charge.     

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.     

Fractionation and Speciation of Manganese in Rhizosphere Soils of Pseudomonas sp. Rhizobacteria Inoculated Pistachio (Pistacia vera L.) Seedlings Under Salinity Stress

Enhancement of manganese (Mn) availability in saline and Mn-deficient soils is very important for plant growth. An experiment was carried out to evaluate the effect of Pseudomonas sp. rhizobacteria (P₀ (control), P₁, P₂ and P₃) and Mn (0 and 10 mg Mn kg^?1 soil) on the distribution of Mn in the rhizosphere of pistachio seedlings under salinity stress (0, 1000 and 2000 mg NaCl kg^?1 soil). The results showed that salinity decreased the dry weight, Mn uptake and chlorophyll content of the pistachio seedlings. However, inoculation with rhizobacteria increased these parameters in saline conditions. Application of rhizobacteria increased the availability of Mn in the rhizosphere soil. The use of rhizobacteria decreased the residual-Mn form in the rhizosphere. Inoculation with rhizobacteria increased the percent of Mn²⁺ and MnCl⁺ species in the soil solution. However, pistachio seedlings inoculation with rhizobacteria increased the contents of Mn available forms in the rhizosphere soil.     

Adsorption features of Cu(II), Pb(II), and Zn(II) by an ordinary chernozem from nitrate,chloride, acetate,and sulfate solutions

The effect of Cl^?,SO ₄ ^2? , CH₃COO^?, and NO ₃ ^? anions on the adsorption of copper, lead, and zinc by an ordinary chernozem has been studied. The effect of the anions on the adsorption of Cu²⁺, Pb²⁺, Zn²⁺ ions is significant but uncertain. It has been shown that the attendant anions affect the shape of the adsorption isotherms, which are described by the Langmuir, Freundlich, or Henri equations. The constants of the adsorption from a nitrate solution calculated from the Langmuir equation (K _L) decrease in the following order: Cu²⁺ > Pb²⁺ >> Zn²⁺. The values of the maximum adsorption (C _max) decrease in the following order: Cu²⁺ ≥ Zn²⁺ > Pb²⁺ for acetate solutions and in the series Pb²⁺ > Zn²⁺ ≥ Cu²⁺ for nitrate solutions. The values of the Henry constants (K _H) calculated for the adsorption of the same cations from chloride solutions decrease in the same order as the values of K _L. The CH₃COO^? anion has the highest effect on the constant values. The NO ₃ ^? and Cl^? anions “switch their places” depending on the attendant cation, but their effect is always lower than that of the acetate anion. The values of C _max for copper and zinc are most affected by the CH₃COO^? anion, and the adsorption of zinc is most affected by the Cl^? and NO ₃ ^? anions. The assessment of the mobility of the adsorbed cations from the extraction with ammonium acetate (pH 4.8) has shown that the content of the desorbed metals is always lower than the content of the adsorbed cations and varies from 0.025 to 83%. According to their mobility, the adsorbed metals form the following order: Zn²⁺ > Pb²⁺ > Cu²⁺. The effect of the attendant anions on the extractability of the adsorbed cations decreases in the following order: chlorides > sulfates > acetates > nitrates.     

Transformation of catechol in the presence of a laccase and birnessite

The transformation of naturally occurring phenols to humic polymers through oxidative coupling reactions may involve oxidoreductive enzymes and soil minerals as catalysts. There is limited information on the possible inhibitory or synergistic interactions between oxidoreductases and mineral catalysts as they participate in oxidative coupling of phenolic substrates. In this study, a ternary system was investigated, in which a fungal enzyme (Trametes villosa laccase), birnessite (δ-MnO₂), and a naturally occurring phenolic compound (catechol) were reacted together to model soil processes. Binary systems (catechol/laccase and catechol/birnessite) were included for comparison. In the absence of the mineral, T. villosa laccase (950 katal ml⁻¹) transformed 31% of catechol, whereas birnessite (1 mg ml⁻¹) in the absence of the enzyme showed a 24% catechol transformation. The percentages of catechol transformation in the binary systems did not accumulate in the ternary system; instead, birnessite and laccase tested together transformed only 36% of catechol. This suggested that birnessite had an inhibitory effect on substrate transformation by laccase catalysis. Enzyme assays indicated that inhibition was a result of enzyme deactivation by humic-like polymers produced by birnessite, and by Mn²⁺ ions released from the mineral. These observations underscore the importance of considering enzyme-soil mineral-organic matter interactions in studies of humus formation and contaminant removal.     

Effect of nitrogen forms on reduction of manganese oxides in an Oxisol by plant root exudates

Reductive dissolution of soil manganese (Mn) oxides increases potential toxicity of Mn²⁺ to plants. In order to examine the effect of nitrogen forms on reduction of Mn oxides in rhizosphere soil, a rhizobox experiment was employed to investigate the reduction of Mn oxides due to the growth of soybean and maize in an Oxisol with various contents of NO₃^–-N and NH₄⁺-N and a total N of 200 mg kg^?1. The results showed that exchangeable Mn²⁺ in rhizosphere soil was 9.6–32.7 mg kg^?1 higher than that in bulk soil after cultivation of soybean and maize for 80 days, which suggested that plant root exudates increased reduction of soil Mn oxides. Application of ammonium-N promoted reduction of Mn oxides in rhizosphere soil compared to application of nitrate and nitrate together with ammonium. Soybean cultivation led to a higher reduction in soil Mn oxides than maize cultivation. Application of single ammonium enhanced Mn uptake by the plants and led to more Mn accumulating in plant leaves, especially for soybean. Therefore, application of ammonium-based fertilizer can promote reduction of soil Mn oxides, while application of nitrate-based fertilizer can inhibit reduction of soil Mn oxides and thus reduce Mn²⁺ toxicity to plants.     

Residual Organic Compound Removal from Aqueous Solution Using Commercial Coconut Shell Activated Carbon Modified by a Mixture of Seven Metal Salts

The modified activated carbon (MAC) derived from commercial coconut shell activated carbon (AC) with mixture of seven metal salts was used as an adsorbent to remove target residual organic compound (sucrose) from aqueous solutions in batch modes. The results indicated that the highest adsorption capacity of sucrose onto MAC reached when the AC was modified at the ratio of impregnation of AC with mixture of seven metal salts, including nitrate silver (AgNO₃), manganese nitrate (Mn (NO₃)₂), potassium bichromate (K₂Cr₂O₇), nitrate cobalt (Co (NO₃)₂·6H₂O), nitrate copper (Cu (NO₃)₂·3H₂O), nitrate nickel (Ni (NO₃)₂·6H₂O) and nitrate iron (Fe (NO₃)₂·9H₂O) of 3% (w/w). The most appropriate conditions for sucrose adsorption onto MAC in batch experiments obtained at pH 7, contact time of 120 min, 800 mg MAC/50 mL of sucrose solution with initial concentration of 1500 mg/L. At this condition, the highest adsorption capacity of sucrose onto MAC reached 28.28 mg/g. The Langmuir, Freundlich, and Sips adsorption isothermal equilibrium models can adequately describe the adsorption properties of sucrose on MAC. The adsorption kinetic of sucrose onto MAC obeyed pseudo-first-order and pseudo-second-order models with the chemical sorption process. The saturated MAC was recovered by heat from an oven. The highest recovery efficiency of saturated MAC obtained at 180 °C in 120 min. The highest adsorption capacity of sucrose onto recovered MAC was 24.31 mg/g, appropriately adsorption capacity of initial MAC.