共查询到20条相似文献，搜索用时 147 毫秒
1.
红壤酸化过程中铁铝氧化物矿物形态变化及其环境意义 总被引：10，自引：0，他引：10
铁铝矿物对土壤中有机质的稳定保持具有十分重要的作用。酸化作用的研究表明,随着浸泡时间的增加,红壤中铁铝总量降低,铝溶蚀较严重;红壤中铁铝氧化物的矿物形态变化表现为:游离态晶质铁铝氧化物大量溶出,而无定形和络合态变化不大。酸性条件下有机质溶出显著,说明除了可能发生水解作用外,游离态铁铝的溶出也起着关键性作用。此外,SEM观察也表明酸化作用引起了土壤团聚体结构的破坏。 相似文献
2.
土壤中的有效态钼是生态地球化学评价的重要内容之一。经典的测定方法是以草酸-草酸铵溶液(Tamm溶液)为浸提剂的催化极谱法,在测定过程中存在铁、锰等离子及草酸盐、有机质的干扰,而消除这些干扰的程序繁琐、耗时较长。本文通过实验初步探讨了干扰机理,认为草酸根和有机质都具有还原性,在浸取过程中铁、锰等多变价的金属离子转变成还原态离子,这几种物质都与测定体系中的氯酸钠发生氧化还原反应,从而影响催化波的灵敏度。本文提出在草酸-草酸铵浸提液中加入固体氢氧化钠沉淀分离铁、锰等杂质,以硝酸-硫酸破坏浸提液中草酸盐及有机质,利用钼-苯羟乙酸-氯酸盐-硫酸体系极谱催化波实现了土壤标准物质中有效态钼的测定。相比于传统消除干扰的方法,本方法所用试剂种类少,操作时间短,有效地减少了分析过程中的误差来源,方法检出限为0.0015μg/g,低于传统方法的检出限(0.0068μg/g),精密度(RSD,n=12)7%,相对误差小于8%,国家标准物质的测定值和标准值更加吻合。经上千件土壤样品的验证,此法适用于pH 3.6~10.5土壤中有效态钼的测定,可测定范围为0.005~2 mg/kg,具有快速简便、测定结果准确和稳定等特点,适合推广应用于大批量土壤有效态钼的快速分析。 相似文献
3.
张家口克山病地区土壤硒的地球化学形态研究 总被引：22，自引：3，他引：19
对张家口克山病地区土壤中硒的７种地球化学形态：水溶态、交换态、有机态（富啡酸态与胡敏酸态）、酸溶性铁锰氧化物态、硫化物态以及硅酸盐态进行了测定,分析总结了各种形态存在的影响因素,从而得出土壤中的有效性硒成能够直接参与硒的生物地球化学循环,并对人体健康产生影响的结论。 相似文献
4.
5.
大量研究表明,溶解性有机质与铁的螯合对生物可利用性铁的输出有重要影响.然而,对于天然有机质,尤其是泥炭沼泽源的酚类物质,与铁相互作用的地球化学机制仍然缺乏研究.以长白山西麓哈尼泥炭沼泽为研究对象,调查了泥炭沼泽源水体可溶性总铁、亚铁、水溶性总酚等理化指标.同时,测定了泥炭中酚酸的组成及含量,分析对比泥炭与土壤中铁的主要赋存形态.并开展了酚铁相互作用模拟实验,研究了泥炭沼泽源水体中酚铁相互作用机制.结果表明:哈尼泥炭沼泽水体中亚铁浓度与水溶性总酚浓度显著相关,说明水溶性总酚对亚铁的存在及运移有重要影响.哈尼泥炭中含有原儿茶酸、咖啡酸、没食子酸、龙胆酸、丁香酸、阿魏酸、对羟基苯甲酸、对香豆酸、水杨酸、香草酸等多种酚酸.其中,具有儿茶酚或没食子酰基结构的原儿茶酸、咖啡酸和没食子酸能与亚铁形成稳定螯合物,是泥炭沼泽源水体中Fe(Ⅱ)保持稳定并可以远距离迁移的关键.研究还表明,原儿茶酸、咖啡酸、没食子酸和龙胆酸对Fe(Ⅲ)有显着的还原作用,有利于沼泽区水体中的保持较高Fe(Ⅲ)和Fe(Ⅱ)浓度.哈尼泥炭中铁主要以活动态(可交换态、络合态和无定形态)为主,为铁的迁移、转化和循环奠定了基础.鉴于泥炭沼泽在全球的分布面积巨大以及亚铁对海洋生物有促进作用,酚酸对铁的作用机制对陆地系统向海洋输送生物可利用铁具有重要意义,并对碳循环、硫循环以及气候变化有重要影响. 相似文献
6.
邻菲啰啉光度法测定高岭土中可溶铁和非可溶铁 总被引：2，自引：1，他引：1
高岭土中铁的赋存状态和含量影响其白度和增白效果,因此快速准确地测定高岭土中不同种类的铁含量具有实际应用意义。高岭土中自由铁和结构铁定量分析困难,为此本文将高岭土中的铁分为可溶铁和非可溶铁两类。高岭土经盐酸酸溶处理后溶液中的铁含量为可溶铁含量,经氢氧化钠碱熔处理后溶液中的铁含量为总铁含量,非可溶铁含量由总铁含量减去可溶铁含量计算得出。采用邻菲啰啉光度法测定溶液中的铁含量,该方法的相对标准偏差小于5%,加样回收率范围在95%～105%,最低检测含量为1.06μg/g。高岭土中的其他元素对铁的测定均没有干扰。所测得的可溶铁为大部分自由铁和少数结构铁。通过对高岭土中的可溶铁进行定量分析,可得知漂白工艺中可除去的最大铁含量。 相似文献
7.
含铁石英岩仅仅是存在于前寒武纪韵律层中的一种贫铁矿。它是由地表风化或火山成因的物质中铁沉积富集而形成的,有一种观点认为含铁石英岩与浅水沉积有关,而另一种观点认为与深水(远海)沉积堆积有关。浅水沉积成因的含铁石英岩,它包括陆源的、生物成因的,甚至溶液沉积方式富集的 相似文献
8.
铁矿石物相分析标准物质的研制 总被引：2，自引：2，他引：2
介绍了研制铁矿石物相分析标准物质的研制工艺及技术关键，列出了磁性铁中铁、碳酸铁中铁、赤（褐）铁矿中铁、硫化铁中铁、硅酸铁中铁和全铁的原始数据和定值数据。所研制的６个标准物质已于１９９５年被国家技术监督局批准为一级标准物质，编号为ＧＢＷ０７２７１～０７２７６。 相似文献
9.
10.
江汉平原高砷含水层沉积物地球化学特征 总被引：2，自引：0，他引：2
选取江汉平原典型地下水砷中毒区仙桃市沙湖原种场为研究区,对3个长50m的钻孔沉积物砷含量与赋存形态及其他化学组成进行了分析。结果表明区内沉积物砷质量分数为1.35~107.5mg/kg(平均值为12.8mg/kg)。黏土或亚黏土层中砷含量较高,这与细粒沉积物中铁锰氧化物、黏土矿物对砷的吸附有关。地下20m左右深度内含水层沉积物中砷含量最高,相应地下水中砷质量浓度高达到1 000μg/L。草酸-草酸铵选择性提取结果指示沉积物中10%~77%(平均38%)的As与无定形铁氢氧化物结合,表明无定形铁氢氧化物还原性溶解可能是控制砷释放与还原的主要地球化学过程,并且有机质生物氧化机制极大地促进了该过程。然而,沉积物中仅1.2%~23%的铁被草酸-草酸铵提取,含水层中砷浓度主要受铁的氢氧化物还原性溶解影响,但其他形式的铁、有机物的吸附作用亦控制着砷的含量。 相似文献
11.
Iron speciation in interaction with organic matter: Modelling and experimental approach 总被引：1，自引：0，他引：1
The present study aims to model iron speciation when interacting with natural organic matter. Experimental data for iron speciation were achieved with insolubilized humic acid as an organic matter analogue for 1.8 × 10− 3 M and 1.8 × 10− 4 M iron concentrations and 2–5 pH range. Combining EPR spectroscopy and chemical analysis allowed us to fit NICA-Donnan model parameters for both organic complexation of iron and oxides precipitation. 相似文献
12.
含铁地下水成因、危害及防治 总被引：3，自引：0，他引：3
含铁地下水形成于中偏酸性的还原性水文地球化学环境中,人为活动也可引发含铁水的出现。含铁水进入水井附近后,有沉淀析出铁矿物从而堵塞水井附近含水层和滤水管的危险,也因为其偏低的ＰＨ值和可能含有硫化物而对金属水井管材具有腐蚀作用。防治含铁水对水井破坏作用的根本方法是采取改善地下水水质的现场处理技术。 相似文献
13.
A combination of flow-injection analysis and kinetic analysis was used to examine the speciation of iron(II) and iron(III) in fulvic acid solutions as a function of pH, ionic strength, and time. This methodology was used to follow a shift in iron speciation from faster to slower reacting species over a timescale of several days. This speciation data shows that both iron(II) and iron(III)-fulvic acid complexes are important iron species in humic-containing natural waters and that their amounts and their rates of transformation to colloidal iron are controlled primarily by the kinetics of thermal (dark) reduction and iron(II) oxidation. The kinetic analysis methodology also yielded the rate constants for the thermal reduction of iron by the fulvic acid. These rate constants decrease with increasing pH and are independent of ionic strength. While thermal reduction was found to be too slow to produce large amounts of steady state iron(II) at circumneutral pH, it does provide a mechanism for iron redox cycling in the absence of photochemical or biochemical processes. 相似文献
14.
《Journal of Geochemical Exploration》2005,85(2):55-62
Concern about arsenic is increasing throughout the world, including areas of the United States. Elevated levels of arsenic above current drinking-water regulations in ground and surface water can be the result of purely natural phenomena, but often are due to anthropogenic activities, such as mining and agriculture. The current study correlates arsenic speciation in acid mine drainage and mining-influenced water with the important water-chemistry properties Eh, pH, and iron(III) concentration. The results show that arsenic speciation is generally in equilibrium with iron chemistry in low pH AMD, which is often not the case in other natural-water matrices. High pH mine waters and groundwater do not always hold to the redox predictions as well as low pH AMD samples. The oxidation and precipitation of oxyhydroxides deplete iron from some systems, and also affect arsenite and arsenate concentrations through sorption processes. 相似文献
15.
Guodong Zheng Yuhua Lang M. Miyahara T. Nozaki T. Haruaki 《Environmental Geology》2007,51(8):1455-1464
Orange precipitate was collected at the mouth of groundwater drainage tubes from the Kumanashi Landslide slip zone in Toyama prefecture, Northwest Japan. Data from XRF, X-ray diffraction, and Mössbauer spectroscopy determined the precipitate as hydrous ferric oxide (HFO) bearing multi-elements such as phosphorous, silica, calcium, etc. The occurrence of HFO may indicate an oxidation of ferrous iron in the percolated groundwater from the slip zone. Moreover, the precipitate iron should be mobilized with groundwater circulation from the slip zone, whose reducing condition was determined by the iron speciation on the same type of landslide profiles within the study area in previous studies. The HFO precipitate may be considered as a secondary reliable indicator to locate the seepage of a slip zone on surface, especially for a landslide newly investigated under wet-warm climate. 相似文献
16.
《Chemical Geology》2006,225(1-2):156-171
Groundwater samples were collected along a groundwater flow path in the Carrizo Sand aquifer in south Texas, USA. Field measurements that included pH, specific conductivity, temperature, dissolved oxygen (DO), oxidation–reduction potentials (Eh in mV), alkalinity, iron speciation, and H2S concentrations were also conducted on site. The geochemistry (i.e., concentrations, shale-normalized patterns, and speciation) of dissolved rare element elements (REEs) in the Carrizo groundwaters are described as a function of distance along a flow path. Eh and other redox indicators (i.e., DO, Fe speciation, H2S, U, and Re) indicate that redox conditions change along the flow path in the Carrizo Sand aquifer. Within the region of the aquifer proximal to the recharge zone, groundwaters exhibit both highly oxidizing and localized mildly reducing conditions. However, from roughly 10 km to the discharge zone, groundwaters are reducing and exhibit a progressive decrease in redox conditions. Dissolved REE geochemical behavior exhibits regular variations along the groundwater flow path in the Carrizo Sand aquifer. The changes in REE concentrations, shale-normalized patterns, and speciation indicate that REEs are not conservative tracers. With flow down-gradient, redox conditions, pH and solution composite, and adsorption modify groundwater REE concentrations, fractionation patterns, and speciation. 相似文献
17.
Guodong Zheng Yuhua Lang Bokuichiro Takano Motoyuki Matsuo Akihito Kuno Haruaki Tsushima 《Journal of Asian Earth Sciences》2002,20(8)
It has been often observed that black mud recently formed and accumulated in slip planes that are closely associated with a progressing landslide in Japan. Mössbauer spectroscopy revealed that the composition of Fe species in the sliding mud is different from those in the debris rock and bedrock. The sliding mud contains more ferrous iron species, which indicates a relatively stronger reducing condition within the sliding zone than within the host rocks. In addition, the composition of Fe species, the total Fe and the volume of sliding mud also change with landslide development. Therefore, detailed Fe speciation in landslide profiles can be a useful approach to understanding the progress of a landslide and may also predict future sliding as well. 相似文献
18.
Lewis J. Alcott Alexander J. Krause Emma U. Hammarlund Christian J. Bjerrum Florian Scholz Yijun Xiong Andrew J. Hobson Lesley Neve Benjamin J. W. Mills Christian Mrz Bernhard Schnetger Andrey Bekker Simon W. Poulton 《Geostandards and Geoanalytical Research》2020,44(3):581-591
The development and application of geochemical techniques to identify redox conditions in modern and ancient aquatic environments has intensified over recent years. Iron (Fe) speciation has emerged as one of the most widely used procedures to distinguish different redox regimes in both the water column and sediments, and is the main technique used to identify oxic, ferruginous (anoxic, Fe(II) containing) and euxinic (anoxic, sulfidic) water column conditions. However, an international sediment reference material has never been developed. This has led to concern over the consistency of results published by the many laboratories that now utilise the technique. Here, we report an interlaboratory comparison of four Fe speciation reference materials for palaeoredox analysis, which span a range of compositions and reflect deposition under different redox conditions. We provide an update of extraction techniques used in Fe speciation and assess the effects of both test portion mass, and the use of different analytical procedures, on the quantification of different Fe fractions in sedimentary rocks. While atomic absorption spectroscopy and inductively coupled plasma‐optical emission spectrometry produced comparable Fe measurements for all extraction stages, the use of ferrozine consistently underestimated Fe in the extraction step targeting mixed ferrous–ferric minerals such as magnetite. We therefore suggest that the use of ferrozine is discontinued for this Fe pool. Finally, we report the combined data of four independent Fe speciation laboratories to characterise the Fe speciation composition of the reference materials. These reference materials are available to the community to provide an essential validation of in‐house Fe speciation measurements. 相似文献
19.
为了解潮间带微环境中磷、铁元素的分布和耦合规律及对磷释放的影响,借助薄膜扩散梯度技术（ZrO-Chelex DGT）原位高分辨率获取九龙江口红树林潮滩孔隙水剖面的溶解活性磷（DRP）、Fe2+浓度,并测定沉积物相应的理化参数.研究结果表明:（1）在表层孔隙水中,DRP、Fe2+浓度呈现显著的正相关性,证实了磷、铁元素的耦合关系以及沉积物铁氧化物对磷吸附/解吸附的控制作用;（2）在深部还原带,DRP浓度相对Fe2+浓度具有较大的波动,主要受到沉积物异质性以及红树植物吸收等的影响;（3）根据表层孔隙水中DRP的浓度梯度计算获得磷的分子扩散通量为0.000 64~0.006 00 μg·cm-2·d-1,结果远低于一般湖泊沉积物内源磷的扩散通量,原因是富铁且具较深氧化带的潮滩沉积物中的磷-铁耦合关系有效地抑制了磷的释放. 相似文献
20.
The iron site geometry in orthopyroxenes (OPX) and synthetic FeO, has been investigated by X-ray Absorption Near Edge Structure (XANES) spectroscopy. Multiple scattering calculations have been used to determine how the iron polyhedral geometry affects the absorption spectra. The results reported here demonstrate that this approach is effective in determining the site geometry around the absorbing atom, allowing the assignment of features in the XANES spectrum to specific structural aspects of the coordination environment. In the case of the orthopyroxenes this method allows discrimination between the multiple scattering contributions to the absorption spectrum due to the two octahedral sites M1 and M2 of the OPX structure. The results obtained with the MS calculation were used to evaluate the effects of polyhedral distortion, symmetry changes and iron site occupancies on the experimental spectra. The results indicate a more quantitative way to interpret XANES experimental spectra and give insights into the interpretation of site geometries of more complex or unknown structures and amorphous materials. 相似文献