高压密闭罐溶样-氢化物原子荧光法测定环境样品中的砷

使用高压密闭罐溶样方式,比较了利用浓HNO3、王水和HNO3+HF消解土壤、沉积物和植物样品,还原后用氢化物发生-原子荧光光谱法(HG-AFS)测定样品中砷的情况。使用优选的浓HNO3溶样法对土壤标准参考物质GBW(E)070009、GBW07404(GSS-4)、GBW07405(GSS-5)、GBW07407(GSS-7)、GBW07408(GSS-8)、GS-BZ50011-88(ESS-1)和植物标准参考物质GBW07604(GSV-3)、GBW07602(GSV-1)进行了分析,砷的测定结果与推荐值基本一致。加标回收实验的回收率在99.9%～105.6%。利用该法对实际样品进行了测定,并与土壤总砷国标法(GB/T22105.2-2008)的分析结果进行了比较,平行样的重现性好,表明砷的分析结果准确可靠。     

金矿样品的几种溶样方法

通过王水、封闭和烧杯敞口及聚乙烯溶样瓶封闭溶样等方法，对含Au矿样的试样分解、溶样体系及各种溶样方法的对比表明，利用聚乙烯溶样瓶，采用HNO3 NaCl KMnO4 NH4HF2溶样体系，在水浴锅中封闭溶样40min，矿样中的Au即可完全分解。经国家标准物质分析验证，结果与标准值相符。封闭溶样可以避免样品外溢、进溅，使分析结果更准确可靠，降低成本，减少环境污染，适用于大批量样品分析。     

黄铁矿 Re-Os 同位素定年化学前处理若干条件初探

对黄铁矿 Re-Os 同位素定年化学前处理过程中的溶样温度、溶样酸介质及溶样时间进行了条件实验.温度实验结果表明,溶样温度对 Re 的测定结果影响不大,而对 Os 的测定结果影响较明显.溶样温度在120~220℃之间时,无论是 HNO3还是逆王水溶样, Re 含量在误差范围内都是一致的,但在120℃、150℃时, Os 的含量偏离真实值,可能是样品和稀释剂中的 Os 同位素并未完全达到平衡,在180℃、200℃和220℃时, Os 的含量基本一致且接近真实值.溶样酸介质实验表明, HNO3和逆王水溶样对 Re 的测定影响不大,而对 Os 的测定影响较明显.无论是用 HNO3还是逆王水溶样,在不同温度下所得到的 Re 含量是一致的,而在120℃、150℃时,逆王水溶样较 HNO3溶样所得到的 Os 含量更加接近真实值,180℃、200℃和220℃时,两种酸介质溶样得到的 Os 含量基本一致且接近真实值.用逆王水在200℃时溶样,时间为5 h、8 h、12 h、18 h所得到的 Re、187Os 含量基本一致,说明较高温度下在较短的时间内便能达到较好的溶样效果.Fe3+浓度对Re 的阴离子交换效率实验表明, Re 的回收率随着 Fe3+浓度的不断升高而逐渐下降.当黄铁矿取样量为3 g时,上柱体积控制在40 mL 左右可获得较高的 Re 回收率     

石笋中稀土元素含量的测定及气候环境意义

首次采用经过改良的外标法校正数据的ICP-MS方法对石笋中的稀土元素含量进行了测定。结果表明,该方法可以用于测定石笋中含量很低的稀土元素,尤其是对含量相对较高的轻稀土元素如La、Ce可以获得较精确的数据。对采集于四川东北部诺水河溶洞群的石笋SJ3的分析结果显示,在相对温暖湿润时期的石笋沉积中稀土元素含量明显增加。可能的原因包括:(1)温暖湿润的气候条件有利于土壤和岩石的化学风化及稀土元素的活化;(2)温暖湿润的气候条件下地下水动力加强,使得地下水中稀土元素的载体(有机质、铁锰胶体和颗粒物质等)增多。因此,石笋沉积中的稀土元素可以用于研究上覆土壤和岩石的化学风化和地下水水文演化。     

用微波封闭溶样氢醌滴定法快速测定金

采用HNO3—NaCl^--MnO2-NK4HF2溶样体系，在微波场中对矿样进行封闭溶解。实验表明，称样20g，利用聚丙烯溶样瓶，在微波场内只要照射2～3min，即可将矿样中的Au完全分解，以活性炭进行吸附富集，氢醌滴定法进行测定，其分析结果可满足地质找矿和选冶工艺对Au分析的要求。     

关于微波炉分解地质样品的评价

为了评价这种快速的地质样品的溶解方法,我们分析了51个地质样品,其中包括岩石、水系沉积物、硫化物矿石、土壤等。这种溶样方法是使用微波加热的HCl—HNO_3—HF的高压溶样技术。所得溶液由电感耦合等离子体光学发射光谱(ICPOES)分析,而残余物由直流电弧摄谱仪进行分析,对于所测大部分物料中的大多数元素,该溶样方法的回收率高于95％;当难熔矿物存在时,Al、Cr、Li、Pb、Si和Zr的回收率较低。采用这种方法,每人每天可制备多达100个样品,     

广西八一锰矿区土壤和主要农作物重金属含量的研究

对广西八一锰矿废弃地土壤基本理化性质及重金属全量(浓HC l 浓HNO3 HF HC lO4消解)、有效态含量(0.1MHC l浸提)和主要农作物重金属含量(浓HNO3 HC lO4消解)进行了测定(AA S)。结果表明:土壤营养缺乏和重金属污染是本矿区生态恢复面临的主要问题。土壤中全磷和全氮含量低于正常指标,且部分C/N比值偏高,同时土壤存在严重的Cd污染,并可能受到M n污染。在锰矿恢复区种植的主要农作物中,部分样品中Pb、M n含量与全部样品的C r、Cd含量超出了植物正常含量范围。农作物的食用部分中Cd、C r、Pb含量普遍超过国家食品限量卫生标准,不宜食用。     

BIF微量稀土元素分析方法及其在冀东司家营铁矿中的应用

以硅铁条带交替出现为特征的条带状铁建造(BIF)是世界上最重要的铁矿资源类型,精确分析磁铁矿的化学组成具有重要意义。本文开展了磁铁矿样品不同溶样方法分析结果的比对,并详细分析和讨论了冀东司家营铁矿磁铁矿与燧石单条带的微量及REE元素分析的地球化学特征。分析结果表明,对于磁铁矿样品,常规HF+HNO₃溶样法与HBr+HNO₃组合溶样法具有一致的溶样效果;司家营BIF的Zr,Sc,Th含量极低,表明未受陆源碎屑的污染;铁质与硅质具有低LREE、高HREE、La和Y正异常的海水REE特征,同时具有Eu正异常的热液REE特征;Ce负异常的缺乏,说明当时的古海洋是一个缺氧的环境。研究发现富铁条带的稀土总量大于富硅条带的稀土总量,这可能与硅、铁沉积物的地球化学习性相关,铁质沉积物更易吸收稀土元素。富矿和普通矿石具有原生的热液与海水的混合来源,部分富矿受到后期流体的强烈扰动,甚至表现出热液流体的特征。     

沥青样品铼-锇同位素分析溶解实验研究

沥青样品中Re、Os含量较低,且组成复杂,因含有大量有机质,在溶样过程中会释放大量CO2,需要大量氧化剂。控制样品称样量和氧化剂比例、用量对保证Os的回收率以及测量信号的稳定性非常重要。本文根据沥青样品组成特点改进了Re-Os同位素分析技术方法,称样量由原来的0.2 g增加到0.4 g,氧化剂由原来的3 mLHCl、6 mL HNO3改为3 mL HCl、4 mL HNO3、3 mL H2O2,改进的方法所得到Os的信号强度提高了大约2倍。考察了改变溶剂组成对不同称样量沥青的氧化效果,研究了氧化剂中加入H2O2对不同称样量沥青样品溶解效果,以及对Os的回收率和仪器测量信号强度的影响程度。采用2 mL HCl、5 mL HNO3、2 mL H2O2作为氧化剂,Carius管高温密闭溶样,直接蒸馏法或传统蒸馏法分离富集Os,丙酮萃取法分离纯化Re,用电感耦合等离子体质谱法(ICP-MS)对采自云南某铅锌矿床的沥青样品Re-Os同位素进行分析测定。沥青的Re-Os同位素等时线年龄为(60±2)Ma(MSWD=2.5,n=7),初始187Os/188Os值为4.36±0.14,表明该沥青样品中Re-Os同位素体系的封闭性较好,而且物质来源为典型的壳源性质。建立的方法能够用于沥青年龄厘定与来源示踪方面的研究。     

Sm-Nd同位素准确测定的影响因素分析

通过对Sm-Nd同位素测定的流程分析,探讨了对Sm-Nd同位素分析的影响因素。采用HF+HNO3+H3BO3溶解样品,可有效地消除氟化物对REE回收率的影响;样品容器和分离柱的本底是全流程本底的主要来源;根据同位素稀释法误差倍增曲线,合理加入稀释剂的量可有效提高147Sm/144 Nd测定的准确度;稀释剂加入量对稀释法同位素比值测定的影响主要来源于稀释剂同位素组成测定的不确定度,通过数学迭代法,可对稀释剂同位素组成测定的质量分馏效应进行有效校正,提高稀释剂同位素组成的准确性。     

High-resolution and precisely dated record of weathering and hydrological dynamics recorded by manganese and rare-earth elements in a stalagmite from Central China

Manganese (Mn) and rare-earth elements (REEs) in a stalagmite (SJ3) collected from Central China were analyzed, using an ICP-MS method for the precise determination of > 40 trace elements in geological samples by enriched-isotope internal standardization. Unlike speleothem Mn and REEs investigated by cathodoluminescence, which may be incorporated into crystal lattice, the Mn and REEs analyzed in SJ3 should come largely from colloidal and particle phases in groundwater and may be associated with non-carbonate inclusions. The Mn and REEs in SJ3 vary significantly during the period between 20 and 10 ka. These elements show remarkable increases since  14.5 ka, suggesting enhanced weathering of the overlying soil layer and the host rock since the onset of the last deglaciation and the strengthening of the Asian summer monsoon. In addition, the Mn and REEs in SJ3 display significant centennial fluctuations which may reflect groundwater dynamics.     

Geochemistry and biogeochemistry of rare earth elements in a surface environment (soil and plant) in South China

Plants and soils derived from different kinds of parent materials in South China were collected for analyses of rare earth elements (REEs) by inductively coupled plasma-mass spectrometry (ICP-MS). The distribution patterns and transportation characteristics of REEs in the soil–plant system were studied. The results show that geochemical characteristics of REEs depend on the types of soils, soils derived from granite being the highest in REE concentration. In a soil profile, REE concentrations are higher in B and C horizons than those in A horizon, with Eu negative anomaly and Ce positive anomaly. Plants of different genera growing in the same sampling site have quite similar REE distribution pattern, but plants of the same genera growing in different soils show considerable variation in characteristics of REEs. The patterns of the different parts of plant resemble each other, but the slope of the patterns becomes different. REEs have fractionated when they were transported and migrated from soil to plant root, stem and leaf, revealing that heavy REEs are relatively less available. REEs distributions in plants are influenced by the soil they grow in and also characterized by their individual biogeochemical characteristics. Biological absorption coefficients indicate difference of REE absorption capacity of plants. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

微波密闭消解-等离子体质谱法测定岩石样品中的稀土元素

建立了有微波密封ＨＦ＋ＨＮＯ３消解样品,等离子体质谱测定岩石样品中１５个稀土元素的分方法。用该方法对国内外岩石标准品进行测定,结果表明稀土元素的测定值与标准值之间的相对偏差小于５％,检出限为（０．１－０．９）＊１０＾－９,多次测定结果的相对标准偏差在１．３％－５．２％。各类实际岩石样品中稀土元素的分析结果均与地质规律相符,进一步证明了方法的可靠性。     

Ligand extraction of rare earth elements from aquifer sediments: Implications for rare earth element complexation with organic matter in natural waters

The ability of organic matter as well as carbonate ions to extract rare earth elements (REEs) from sandy sediments of a Coastal Plain aquifer was investigated for unpurified organic matter from different sources (i.e., Mississippi River natural organic matter, Aldrich humic acid, Nordic aquatic fulvic acid, Suwannee River fulvic acid, and Suwannee River natural organic matter) and for extraction solutions containing weak (i.e., CH₃COO⁻) or strong (i.e., ) ligands. The experimental results indicate that, in the absence of strong REE complexing ligands in solution, the amount of REEs released from the sand is small and the fractionation pattern of the released REEs appears to be controlled by the surface stability constants for REE sorption with Fe(III) oxides/oxyhydroxides. In the presence of strong solution complexing ligands, however, the amount and the fractionation pattern of the released REEs reflect the strength and variation of the stability constants of the dominant aqueous REE species across the REE series. The varying amount of REEs extracted by the different organic matter employed in the experiments indicates that organic matter from different sources has different complexing capacity for REEs. However, the fractionation pattern of REEs extracted by the various organic matter used in our experiments is remarkable consistent, being independent of the source and the concentration of organic matter used, as well as solution pH. Because natural aquifer sand and unpurified organic matter were used in our experiments, our experimental conditions are more broadly similar to natural systems than many previous laboratory experiments of REE-humic complexation that employed purified humic substances. Our results suggest that the REE loading effect on REE-humic complexation is negligible in natural waters as more abundant metal cations (e.g., Fe, Al) out-compete REEs for strong binding sites on organic matter. More specifically, our results indicate that REE complexation with organic matter in natural waters is dominated by REE binding to weak sites on dissolved organic matter, which subsequently leads to a middle REE (MREE: Sm-Ho)-enriched fractionation pattern. The experiments also indicate that carbonate ions may effectively compete with fulvic acid in binding with dissolved REEs, but cannot out compete humic acids for REEs. Therefore, in natural waters where low molecular weight (LMW) dissolved organic carbon (DOC) is the predominant form of DOC (e.g., lower Mississippi River water), REEs occur as “truly” dissolved species by complexing with carbonate ions as well as FA, resulting in heavy REE (HREE: Er-Lu)-enriched shale-normalized fractionation patterns. Whereas, in natural terrestrial waters where REE speciation is dominated by organic complexes with high molecular weight DOC (e.g., “colloidal” HA), only MREE-enriched fractionation patterns will be observed because the more abundant, weak sites preferentially complex MREEs relative to HREEs and light REEs (LREEs: La-Nd).     

An Evaluation of Methods for the Chemical Decomposition of Geological Materials for Trace Element Determination using ICP-MS

Complete dissolution is essential to obtain accurate analytical results using ICP-MS. In this study, decomposition techniques (i.e. acid digestions using Savillex Teflon vials, a high pressure digestion system and microwave oven, a combined lithium tetraborate fusion - HF/HNO3 acid decomposition and sodium peroxide sinter) for the total dissolution of different types of geological reference materials have been investigated. Savillex Teflon vial HF/HNO3 digestion is effective for basaltic samples. The high pressure HF/HClO4 digestion (PicoTrace TC-805 digestion system, Bovenden, Germany) allows dissolution of basalts and ironstones. Granites and magnetite-rich samples can be dissolved using a high pressure HF/H₂SO₄ method. Geological samples cannot be effectively attacked by microwave acid digestion. A combined lithium tetraborate fusion - HF/HNO3 acid digestion method allows complete dissolution of many different types of geological materials; however, this method precludes the determination of volatile elements due to the high fusion temperature (1000 °C). A sodium peroxide sinter method at 480 °C has the potential for the rapid determination of Y, Sc and REE in different types of geological materials. However, the lack of ultra-pure reagents precludes the use of lithium tetraborate fusion and sodium peroxide sinter methods for the measurement of geological samples with low trace element abundances.     

Fractionation characteristics of rare earth elements (REEs) linked with secondary Fe,Mn, and Al minerals in soils

Soil secondary minerals are important scavengers of rare earth elements (REEs) in soils and thus affect geochemical behavior and occurrence of REEs. The fractionation of REEs is a common geochemical phenomenon in soils but has received little attention, especially fractionation induced by secondary minerals. In this study, REEs (La to Lu and Y) associated with soil-abundant secondary minerals Fe-, Al-, and Mn-oxides in 196 soil samples were investigated to explore the fractionation and anomalies of REEs related to the minerals. The results show right-inclined chondrite-normalized REE patterns for La–Lu in soils subjected to total soil digestion and partial soil extraction. Light REEs (LREEs) enrichment features were negatively correlated with a Eu anomaly and positively correlated with a Ce anomaly. The fractionation between LREEs and heavy REEs (HREEs) was attributed to the high adsorption affinity of LREEs to secondary minerals and the preferred activation/leaching of HREEs. The substantial fractions of REEs in soils extracted by oxalate and Dithionite-Citrate-Bicarbonate buffer solutions were labile (10 %–30 %), which were similar to the mass fraction of Fe (10 %–20 %). Furthermore, Eu was found to be more mobile than the other REEs in the soils, whereas Ce was less mobile. These results add to our understanding of the distribution and geochemical behavior of REEs in soils, and also help to deduce the conditions of soil formation from REE fractionation.     

兴蒙-华北地球化学走廊带稀土元素含量与空间分布

为研究兴蒙造山带-华北克拉通地球化学走廊带区域地球化学组成及其横向空间变化,统计分析不同地理单元和五万图幅单元的REE含量并绘制其空间分布折线图.内蒙古半干旱草原土壤中稀土含量较低,与其草原沙土的粘土矿物较少有关;江苏北部冲积平原区的土壤中稀土含量较高,与降雨量存在良好空间对应关系.内蒙古红格尔到河北张家口,土壤与岩石∑REE的比值绝大多数小于1,REE发生贫化;山东章丘到江苏连云港,比值基本大于1,REE发生富集.华北克拉通内蒙地块土壤稀土特征与兴蒙造山带相似,可能受其草原沙土景观的影响.在不同构造单元之间,LREE与HREE亏损与富集的空间分布存在细微差异.结果表明:地理景观,特别是黏土矿物是影响土壤REE含量的重要因素,降雨量与REE存在良好空间对应关系,REE自身的地球化学性质的差异在土壤形成过程中对轻重稀土元素分异具有重要影响.      

岩石—土壤—铁芒萁系统中稀土元素的分布、迁移和累积

在赣南非稀土矿区和四处不同稀土矿区内取样,用ICP-MS法测定岩石-土壤-铁芒萁系统中15个稀土元素的含量,并对其分布、迁移、累积特征进行了研究。结果表明:稀土元素在岩石、土壤各层含量由高到低的顺序为C(心土层)>A(表土层)>B(底土层)>D(成土母岩);在铁芒萁植物体内的分布规律是:轻稀土元素含量为叶>根>茎>叶柄;重稀土元素含量为根>叶>茎>叶柄;稀土元素演化、迁移的难易是由稀土元素的重轻所决定的;岩-土-芒萁系统各环节间稀土元素的含量模式基本相似,表征元素在岩石→土壤→植物大系统中存在着向量(非均衡性)关系。     

Mobility of rare earth elements in the system soils–plants–groundwaters: a case study of an arid area (Oman)

Groundwater samples from six wells and various species of plants from soils developed on ophiolites were collected from an arid area (AlKhod area, Oman) and analyzed for trace elements including rare earth elements (REEs). The distribution patterns of REEs in plants indicated an enrichment in middle REEs (MREEs?=?Sm to Dy) and heavy REEs (HREEs?=?Ho to Lu), when they are normalized to the REE composition of the Post Archean Australian Shale (PAAS), with a significant negative anomaly in Ce and a positive anomaly in Eu. Compared to Oman ophiolites, the REEs in different species of plants are depleted in Ce and enriched in MREEs and slightly enriched in light REE (LREE?=?from La to Nd). Relative to PAAS, the distribution of REEs in groundwaters revealed similar patterns to the REE distribution in plants. The distribution patterns of REEs in plants relative to those in waters are nearly flat. These patterns suggest that the transfer of REEs from soil solutions to the groundwaters in Oman occurs without any significant fractionation.     

Hydrofluoric Acid‐Free Digestion of Geological Samples for the Quantification of Rare Earth Elements by Inductively Coupled Plasma‐Optical Emission Spectrometry

Rare earth elements (REEs) are very important to technological development as well as to geochemical and environmental studies. In this work, hydrofluoric acid (HF) was replaced by condensed phosphoric acid (CPA) in the digestion of geological samples, and the quantification of REEs was performed by inductively coupled plasma‐optical emission spectrometry (ICP‐OES). Six international reference materials (RMs), named DC86318, CGL 111, CGL 124, CGL 126, OKA‐2 and COQ‐1 and three Brazilian ore samples, named Araxá, Catalão and Pitinga were analysed. Only zircon and xenotime, which are potential REE‐bearing minerals, were not completely dissolved. Nevertheless, no REE associated with zircon was detected. The investigated digestion method presented many advantages: It was relatively fast (3 h), avoided fluoride precipitation, it was less hazardous because handling diluted H₃PO₄ is safer than HF, NH₄F or NH₄HF₂ aqueous solutions, it preserved the quartz fittings of the measurement equipment and the final solution contained lower levels of total dissolved solids than those produced by the fusion method.