云贵高原湖泊近代沉积作用的Fe、Mn、S指示

铁、锰、硫具有强烈的氧化还原敏感性，在湖泊沉积地球化学过程中扮演着重要的角色。铁、锰、硫控制了沉积物中的氧化还原分带，对磷及其它一些微量金属元素的形态和分布具有重要影响。因此本文中我们选择铁、锰、硫来指示湖泊沉积作用中氧化还原过程的变化，为进一步高精度提取环境信息奠定基础。本文对比阿哈湖、洱海和阳宗海，通过铁、锰、硫在湖水、孔隙水和沉积物体系内的垂直剖面特征分析，阐述了三湖沉积物中氧化还原过程的区别、氧化还原边界层对铁锰循环的控制作用以及铁-锰-硫对重金属的控制作用，深入探讨了铁、锰、硫及微量元素记录的早期成岩改造特征及其对湖泊沉积作用的指示意义，进一步阐明了沉积物中的有机质降解规律及早期成岩机制，获得了如下结论：1．阿哈湖水中铁、锰出现季节性释放，锰的季节性释放强度比铁大；在冬季和夏季，阿哈湖沉积物界面铁、锰均出现富集。冬季的富集程度强于夏季，锰的富集程度远远强于铁。沉积物表层由冬季的黄褐色转变为夏季的黑色，表示铁、锰氧化物层转变为FeS层。2．洱海沉积物中，铁、锰均在沉积物一水界面出现富集，界面以下，铁、锰的含量逐渐递降。铁、锰在孔隙水中产生扩散迁移，而在沉积物表层形成富集，说明洱海沉积物表层处于较好的含氧状况，氧化还原边界层处于沉积物中；阳宗海沉积物孔隙水中铁锰峰值均位于界面2cm处，而沉积物中铁在表层出现亏损，表明夏季阳宗海表层处于缺氧状态，氧化还原边界层位于湖水中。3．铁、锰的界面扩散和沉降通量在不同湖间差异较大。但锰的扩散通量占沉降通量的比例高于铁，锰在界面的沉积后再迁移程度和沉积记录的改造程度比铁显著。湖泊中铁、锰在有机质降解过程的驱动下，围绕沉积物一水界面形成氧化还原循环。其中锰的循环相当激烈，铁则较为缓和。铁、锰界面循环受氧化还原边界层和沉积物—水界面的双重控制。4．三湖沉积物界面处均存在硫酸盐的还原作用。洱海硫酸盐由于其含量较低以及表层良好的含氧状况因此不可能成为有机质降解的主要氧化剂，而阳宗海和阿哈湖则情况相反。阿哈湖沉积物柱芯好氧菌和SRB的分布进一步证实了表层处硫酸盐在SRB的参与下强烈的还原作用，同时说明有机质的好氧和厌氧降解并不是完全对立的；水体向沉积物内部扩散是高硫酸盐浓度湖泊的主要清除作用，而对于低硫酸盐含量湖泊而言，水体浮游生物如藻类吸收和同化作用应是水体硫酸盐的主要清除机制。5．三湖沉积物硫主要都以黄铁矿存在。阳宗海的AVS含量较高，AVS和FeS_2在界面的富集进一步证实了在阳宗海沉积物界面存在着强烈的硫酸盐还原作用；阿哈湖沉积物中硫酸盐的还原与季节无太大联系。在夏季和冬季，沉积物表层均表现出明显的SO_4~(2-)还原作用。只不过随着氧化还原边界层的迁移，SO_4~(2-)还原作用的范围也随之发生迁移。铁氧化物作为电子受体参与有机质分解的过程中，水铁矿和纤铁矿等Feo首先被还原而溶解出来。同时，Feo和Fec是可以互相转化的，针铁矿和赤铁矿等晶体铁氧化物可以向水铁矿和纤铁矿转化。6．三湖中Corg都表示出明显的降解趋势，证明了沉积物表层存在的早期成岩作用。洱海表现出“沉降一降解一堆积”三阶段分布特征，而阳宗海和阿哈湖沉积物中Corg表现出“降解一堆积”二阶段分布特征；洱海沉积物中有机质的选择性分解不明显，C／N指示沉积物有机质主要来自无纤维束的陆源植物；阿哈湖沉积物中C／N很高，均>20，且随深度增加呈现上升的趋势，说明阿哈湖沉积物中有机质含易降解的低N和难降解的高C，有机质主要来源于陆源输入。7．洱海和阳宗海沉积物中均存在明显的重金属再迁移现象。洱海沉积物中铁、锰循环对Pb、Cu的迁移影响很大；颗粒物的吸附一解析作用是影响Cd迁移的主要因素；洱海沉积物中可迁移释放的Ni含量并不高。8．阳宗海沉积物孔隙水中Ni、Cu、Cd均与铁、锰表现出良好的相关性，铁、锰氧化物的还原是造成它们在孔隙水表层富集的主要控制因素。而Pb与铁、锰呈现微弱的正相关。Pb、Cd相对于Cu、Ni的释放趋势较强，再迁移作用较剧烈。Pb、Cd在表层孔隙水中与一些有机、无机化合物络合，由于沉积物的吸附作用而再次沉降到沉积物表层形成富集。沉积物中重金属的再迁移主要受有机质降解、铁锰氧化物还原和硫化物沉积控制，但是不同的湖泊控制因索各不相同。

贵州红枫湖沉积物-水界面Fe、Mn地球化学研究

在地球环境的界面及其附近，发生着重要的物理、化学和生物反应，进行着频繁的物质交换和输送。研究和认识环境界面的地球化学过程对揭示环境演化、评价环境净化、认识成矿机理均具重要的科学意义。Fe、Mn是地表水环境中两个丰度最大的微量营养元素，也是典型的氧化还原敏感性元素，因其氧化物的吸附特性而对其它微量元素的地球化学行为有着显著的控制作用。因此，Fe、Mn地球化学的研究历来是水环境领域中令人瞩目的一个焦点。地表水环境中Fe、Mn的研究始于海底锰结核的发现及其成因问题的探讨，而Fe、Mn在湖泊研究中受到重视则始于湖泊富营养化问题的出现。二次大战使湖泊Fe、Mn的研究一度中断，直到七十年代因水资源短缺和水环境污染问题的出现才使这一研究重新受到重视，并于近十年得到迅速发展在采样技术、分析方法、Fe、Mn的形态、氧化还原作用、早期成岩作用以及地球化学循环机理的研究上取得了一系列重要的进展。其中以英国Davison的工作最引人注目。一般认为，Fe、Mn在湖泊中的行为受氧化还原边界层的控制。但是，由于研究方法的局限，缺乏将湖水和沉积物作为一个整体的系统研究。尤其是未能对沉积物-水界面及其附近Fe、Mn的行为开展细致的工作，因此在Fe、Mn循环机理的认识上尚存许多疑点。有鉴于此，本项研究着重探讨沉积物-水界面及其附近Fe、Mn的地球化学行为和特征。利用自制的湖泊沉积物和孔隙水取样装置，分别于春秋两季在红枫湖按垂直剖面采集湖水、界面水、孔隙水和沉积物样。采用滤膜技术作湖水、界面水和孔隙水Fe、Mn的形态分析，并作沉积物Fe、Fe~(3+)、Fe~(2+)、Mn、S和孔隙水P、HCO_(3~-)、SO_4~(2-)、NO_(3~-)等项目的分析，完成湖水、界面水的水化学全分析和沉积物的X-射线衍射分析。从而获得以下结果和认识：1.形态。湖水中Fe、Mn均呈微粒态；界面水中Fe呈微粒态，Mn则以微粒态为主，尚有部分离子态；孔隙水中Fe以离子态为主，存在部分胶体态，Mn则以离子态存在。2.特征剖面。春秋季湖水中距沉积物-水界面5m以上，Fe、Mn分布均一，5m以下，Fe、Mn均向界面递增10倍左右；界面水中，Fe、Mn继续向界面递增，但Fe在距界面10cm左右向界面略有递减，同时，在距界面20cm高度Fe的溶解态出现峰值分布，而Mn的溶解态则向界面递增；孔隙水中Fe、Mn均呈峰值分布，并均于12cm深度以下趋于稳定，其中Mn峰位于3cm深度，Fe峰则位下去8cm深度，Fe在10cm深度还存在一谷值分布；沉积物中Fe于7cm深度含量略呈下降趋势，Mn则在界面出现高值，并于0.5cm深度含理突降。3.界面通量。Fe在界面的沉降通量为10.9mg.cm~(-2)a~(-1)，扩散通量为-0.24mg.cm~(-2)a~(-1)，净重通量则为10.7mg.cm~(-2)a~(-1)，扩散量只有沉降通量的2%；Mn在界面的沉降通量为0.203mg.cm~(-2)a~(-1)，扩散通量为-0.062mg.cm~(-2)a~(-1)，净通量则为0.141mg.cm~(-2)a~(-1)，扩散通量占沉降通量的30%。Fe、Mn在界面的平流通量均可忽略不计。4.氧化还原作用。Fe、Mn在沉积物中按氧化电位的高低先后充当有机质分解的主要氧化剂，发生还原溶解，然后经扩散作用重新进入湖水中，并在氧化过程的作用下于界面附近形成微粒态Fe、Mn的富集。5.平衡矿物。沉积物孔隙水中Fe(II）的平衡矿物在8-12cm深度范围内为单硫铁矿（FeS)和黄铁矿（FeS_2)，12cm深度以下为菱铁矿（FeCO_3)；Mn（II）的平衡矿物则为菱锰矿（MnCO_3)。6.界面循环机理。在湖泊中Fe、Mn循环均受沉积物-水界面的控制围绕界面进行，循环过程由还原、扩散、氧化和沉降四个环节组成，其中Mn循环就在界面附近，而Fe循环则深入沉积物内部。Mn的界面循环相当激烈，Fe则较为缓和。Fe、Mn界面循环的结果使界面附近的湖水和沉积物中出现Fe、Mn的富集，其中Fe的富集程度 相对较小，Mn则非常显著。7.环境效应。Mn的界面循环可能导致~（210）Po的沉积后再迁移，而~（210）Pb的沉积后再迁移则可能与Fe的界面循环有关；Fe、Mn界面循环所形成的富集层对湖泊水库的水质构成严重的潜在威胁；根据Fe、Mn的还原优势作用带可以确定湖泊沉积物的氧化还原环境。

Regeneration behaviors of Fe/Si-2 and Fe-Mn/Si-2 catalysts for C2H6 dehydrogenation with CO2 to C2H4

The catalytic performance of Fe/Si-2 and Fe-Mn/Si-2 catalysts for conversion of C2H6 with CO2 to C2H4 was examined in a continuous-flow and fixed-bed reactor. The results show that the Fe-Mn/Si-2 catalyst exhibits much better reaction activity and selectivity to C2H4 than those of the Fe/Si-2 catalyst. Furthermore, the coking-decoking behaviors of these catalysts were studied through TG. The catalytic performances of the catalysts after regeneration for conversion of C2H6 or dilute C2H6 in FCC off-gas with CO2 to C2H4 were also examined. The results show that both activity and selectivity of the Fe-Mn/Si-2 catalyst after regeneration reached the same level as those of the fresh catalyst, whereas it is difficult for the Fe/Si-2 catalyst to refresh its reaction behavior after regeneration.

Struktura fizyczna gruntu, zawartość substancji organicznej oraz skład chemiczny gleb w podłożach 21 stanowisk zieleni miejskiej na terenie Poznania. Część IV. Zawartość mikroelementów: Cl, Fe, Mn, Zn, Cu, B oraz Na, Pb i Cd. Wskaźnik zasolenia EC

This article presents the physical structure of the land, organic substances content and the chemical composition of soil comprising subsoil of 21 urban greenery locations in the city of Poznań. As they tend to be commonly underestimated, they have also been presented with view to their vital functions in plants’ life processes. The analysed microelements are referred to their levels, the so-called geo-chemical background of Polish soils and the limit values for field soils with medium levels of nutrients.

Contenido de Fe, Mn, y Zn en nogal (Carya illinoensis, L. Koch) en huertas comerciales de Bustamante, Nuevo León

Tesis ( Maestro en Ciencias en Producción Agrícola) U.A.N.L.

Water-soluble Cu, Fe, Mn and Zn species in nuts and seeds

An approach was developed to estimate molecular weight distribution of water-soluble Cu, Fe, Mn and Zn species in Brazil nut, cupuassu seed and coconut pulp by size exclusion chromatography (SEC) coupled on-line to ultra-violet (UV) and off-line to graphite furnace atomic absorption spectrometry (GF-AAS) detectors and matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF-MS). SEC-UV analytical signals showed the prevalence of high molecular weight (HMW) species (79-1.7 kDa for Brazil nut, 50-1.7 kDa for coconut pulp, and 34-1.7 kDa for cupuassu seeds). The Brazil nut SEC-UV, GF-AAS and MALDI-TOF mass spectra gave confirmation of the association of the elements with water-soluble compounds. The elemental profiles were associated with fractions of compounds of molecular weight 1.2-16 kDa for Brazil nut, 1.7-13 kDa for coconut pulp, and 1.2-7.6 kDa for cupuassu seeds. (C) 2009 Elsevier Inc. All rights reserved.

Fast sequential multi-element determination of Ca, Mg, K, Cu, Fe, Mn and Zn for foliar diagnosis using high-resolution continuum source flame atomic absorption spectrometry: Feasibility of secondary lines, side pixel registration and least-squares background correction

The fast sequential multi-element determination of Ca, Mg, K, Cu, Fe, Mn and Zn in plant tissues by high-resolution continuum source flame atomic absorption spectrometry is proposed. For this, the main lines for Cu (324.754 nm), Fe (248.327 nm), Mn (279.482 nm) and Zn (213.857 nm) were selected, and the secondary lines for Ca (239.856 nm), Mg (202.582 nm) and K (404.414 nm) were evaluated. The side pixel registration approach was studied to reduce sensitivity and extend the linear working range for Mg by measuring at wings (202.576 nm; 202.577 nm; 202.578 nm; 202.580 nm: 202.585 nm; 202.586 nm: 202.587 nm; 202.588 nm) of the secondary line. The interference caused by NO bands on Zn at 213.857 nm was removed using the least-squares background correction. Using the main lines for Cu, Fe, Mn and Zn, secondary lines for Ca and K, and line wing at 202.588 nm for Mg, and 5 mL min(-1) sample flow-rate, calibration curves in the 0.1-0.5 mg L-1 Cu, 0.5-4.0 mg L-1 Fe, 0.5-4.0 mg L-1 Mn, 0.2-1.0 mg L-1 Zn, 10.0-100.0 mg L-1 Ca, 5.0-40.0 mg L-1 Mg and 50.0-250.0 mg L-1 K ranges were consistently obtained. Accuracy and precision were evaluated after analysis of five plant standard reference materials. Results were in agreement at a 95% confidence level (paired t-test) with certified values. The proposed method was applied to digests of sugar-cane leaves and results were close to those obtained by line-source flame atomic absorption spectrometry. Recoveries of Ca, Mg, K, Cu, Fe, Mn and Zn in the 89-103%, 84-107%, 87-103%, 85-105%, 92-106%, 91-114%, 96-114% intervals, respectively, were obtained. The limits of detection were 0.6 mg L-1 Ca, 0.4 mg L-1 Mg, 0.4 mg L-1 K, 7.7 mu g L-1 Cu, 7.7 mu g L-1 Fe, 1.5 mu g L-1 Mn and 5.9 mu g L-1 Zn. (C) 2009 Elsevier B.V. All rights reserved.

Evaluation of alternate lines of Fe for sequential multi-element determination of Cu, Fe, Mn and Zn in soil extracts by high-resolution continuum source flame atomic absorption spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Determinação direta e simultânea de Al, As, Fe, Mn e Ni em cachaça por espectrometria de absorção atômica em forno de grafite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparative procedures for the sample decomposition of rocks used in organic agriculture and the determination of Cu, Fe, Mn, and Zn by FAAS

The aim of this work was to develop an appropriate sample preparation procedure for the flame atomic absorption spectrometry determination of Cu, Fe, Mn, and, Zn in rocks used in organic agriculture as a source of macro- and micronutrients.Six different procedures were evaluated and are classified into three groups: (a) pressure digestion system with Teflon bombs, (b) conventional wet digestion in a digester heating block, and (c) closed microwave system with pressure and temperature control.Two standard reference materials and two commercial samples were analyzed. It was found that the closed microwave system required low reagent consumption, less time, and resulted in low contamination.