Distribution of rare earth elements in sewage-irrigated soil profiles in Tianjin, China

The concentrations of rare earth elements(REEs)in the soil extracts and soil solutions from two different alluvial soil profiles irrigated with sewage were measured using inductively coupled plasma-mass spectrometry.The results showed that the REE concentrations in the soil extracts from soil samples affected by sewage irrigation were much higher than those in virgin soil samples.The REE concentrations in the soil extracts of the rhizophere soil were higher than those of the non-rhizophere soil.The shale-normalized REE patterns in the soil extracts from the upper soil layer affected by sewage irrigation shown middle REE(MREE)enrichment relative to light REE(LREE)and heavy REE(HREE).This result was attributed to the MREE-rich organic colloidal material,REE-HM(humic and fulvic acids)and phosphate-REE complexations.The REE patterns in the soil extracts from deep soil little-affected by sewage irrigation showed HREE enrichment relative to LREE,which might have been caused by the preferential complexation of HREE with carbonate.The normalized La/Yb ratios in the soil extracts increased with the decrease in depth.The sewage irrigation did not affect the total REE contents and REE pattern in the soil profiles.     

赣南稀土矿区农田土壤环境有效态稀土的分布

以赣南离子型稀土矿区农田土壤环境受稀土金属污染为调查研究对象,采用矿区土壤采样分析测试的研究方法,对受稀土资源开发活动影响的矿区农田土壤环境的有效态稀土分布进行调查研究。结果表明：在稀土资源开发活动的影响下,稀土金属在农田土壤中累积效应显著;相较对照区土壤,矿区轻重稀土比显著增大;矿区稀土形态分布呈紧结有机态﹥可交换态﹥铁锰氧化物态﹥松结有机态﹥专性吸附与碳酸盐态﹥水溶态;矿区中,有效态稀土、轻稀土、重稀土沿土壤层自上而下呈A (淋溶层)﹥B(淀积层)﹥C(母质层)分布;矿区土壤稀土可交换态、松结有机态、专性吸附与碳酸盐态和紧结有机态呈A>B>C分布,水溶态和铁锰氧化物态呈B>A>C分布。     

Local concentration of middle and heavy rare earth elements in the col on the weathered crust elution-deposited rare earth ores

This present study focused on investigating the content and relative enrichment multiple of rare earth elements(REEs) in different terrain of weathered ore body, and the value of light rare earth elements/middle and heavy rare earth elements(LREEs/HREEs), in order to understand the mobilization and redistribution of HREEs, Furthermore, the abrasion pH was investigated as well, The results show that the average contents of HREEs in the knap, ridge and col are 37.26, 61.71, and 271.3 μg/g, respectively. The value of LREEs/HREEs is decreased from 16.78 to 7.914 between knap and col and the relative enrichment multiple of HREEs is as follows: C_(Col-HREEs) C_(Ridge-HREEs) 0. It is indicated the HREEs is concentrated in the col and the enrichment degree of HREEs is stronger than the ridge and the knap. Rare earth elements fractionation is exhibited in the different terrain of weathered ore body. Based on this study, the finding that HREEs concentrate in the lower terrain of weathered crust elution-deposited rare earth ores, such as in the col, would become a marker or indicator to search for middle and heavy rare earth enriched zone.     

A review of fractionations of rare earth elements in plants

Studies were carried out on several aspects of rare earth elements （REEs）, such as the theory and practice of their applications in agriculture, their geochemical behaviors in natural and agricultural ecosystems, the mechanisms for the increase of crop yield using REE fertilizer, and their toxicology. However, limited knowledge was available for the transfer processes and the features and mechanisms of distribution and fractionations of REEs inside plants. The characteristics of REE fractionations in plants can be used to ＂trace＂ the pathway of REE transportation from soils （solution） to plants. A better understanding of the mechanisms of REE fractionations was helpful to investigate the controlling factors, including both the internal and the external ones. The characteristics and mechanisms of REE fractionations in plants and their significance were reviewed. Furthermore, the prospect for these fields was discussed, in hope of providing a new way in studying the bioavailability of REEs and heavy metals.     

Global rare earth resources and scenarios of future rare earth industry

It is known to all that China is abundant in rare earth resources.But rare earth deposits are really not that rare in the earth crust.In the five continents,i.e.Asia,Europe,Australia,North and South America,and Africa,there are about thirty four countries found to have rare earth deposits;Brazil might surpass China and rank the first in rare earth deposits.At present,investment in rare earth production was surged,there have been about 200 projects,and the total production for 25 of them would be more than 170 thousand tons after 2015,a multi-supply system on rare earths is being established worldwide.Cautions on the investment of rare earth production are involved.     

Content of rare earth elements in Salvia miltiorrhiza bunge from different areas

Salvia miltiorrhiza bunge(SMB) has been widely used as a traditional Chinese medicine for a long time,and today more and more attention has been paid to the effective components in Chinese traditional medicine,especially to rare earth elements(REEs).14 kinds of REEs in SMB from different areas were analyzed by the methods of ICP-MS.The results showed that the total concentration of REEs(as REO,the same below) ranged from 8.43(as dry weight,the same below) to 37.30 mg/kg,and the concentrations of La,Ce and Nd were higher than 2 mg/kg except Nd in SMB from Beijing.So the total concentration of REEs in SMB was much higher than that in rice,corn and barley,which could be the mechanism of curative effect of SMB on cardiovascular cerebrovascular system,digestive system,respiratory system,countershock and antibiotic.The character of other elements and the content of REEs in soil from different areas should be responsible for the difference,but the allocation mechanism of REEs in SMB should be further studied.     

Dissolved rare earth elements estimation of ion-absorption rare earth ores using reflectance spectroscopy in south Jiangxi province,China

Ion-absorption rare earth ores are an important mineral resource in China. Nowadays, the unauthorized mining has become a serious problem, resulting in severe water pollution and the wastage of rare earth elements (REEs). Being able to estimate the concentration of dissolved REEs in water bodies near mines is essential for tackling this environmental problem. Conventionally, quantitative analyses of the contents of dissolved REEs are performed using laboratory-based techniques, which can be time consuming and costly. Spectral reflectance is a rapid and cost-effective means of characterizing the chemical compositions of light-absorbing materials. In this study, reflectance spectroscopy was performed on dissolved REEs, and the correlation between their reflectance characteristics and REE content was determined. A total of 50 aqueous media samples collected in south Jiangxi Province and 25 laboratory-produced aqueous media samples were tested, and their reflectance spectra and REE contents were measured using reflectance spectroscopy and inductively coupled plasma mass spectrometry, respectively. Next, the reflectance, differential reflectance, and absorption depth were analysed based on the REE content. Six diagnostic absorption features related to REEs are recognised in the visible and near-infrared wavelength regions, along with several smaller peaks. It indicates that the results of the absorption depth analysis are in accordance with the absorption spectra characteristics of the REEs, with the R² value being higher than 0.97. The intensity of each of the six absorption bands exhibits a linear correlation to the total REE content. Therefore, linear regression models can be derived for estimating the total concentration of REEs in aqueous media samples. What's more, the detection limit for REEs is determined to be about 30 μg/L. Thus, it can be concluded that reflectance spectroscopy is a suitable technique for estimating the concentration of dissolved REEs.     

Vertical distribution of rare earth elements in a wetland soil core from the Sanjiang Plain in China

The objective of this study was to investigate the vertical distribution of rare earth elements (REEs) in a natural wetland soil core to understand the influence of natural and anthropogenic activities on geochemical behavior of REEs. A natural wetland soil core of 95 cm was collected from the Sanjiang Plain in China and sliced into 5 cm slices for analyses of REEs, Fe, Al, Mn, Sc, Y, and soil organic matter (SOM). Results indicated that SOM was accumulated in the upper part of the soil core (0 to 20 cm depth), while Fe and Mn was reductively leached from the upper part of the soil core and accumulated in the low part. The content of total REEs ranged from 137.9 to 225.9 mg/kg in the soil core. Content profiles obtained for all REEs were almost identical except for Ce. The highest contents of REEs generally occurred at about 20 cm depth, but enrichment factor (EF) of REEs except Ce was usually the highest in the surface horizon. Average EF ranged from 1.1 for La to 2.1 for Gd. The pronounced shift in EF occurred at about 40 cm depth and it gradually increased from 40 cm depth to surface (except for Ce), probably suggesting anthropogenic atmospheric deposition of REEs. In comparison with chondrite, Eu was depleted in all horizons, while Ce was negatively anomalous in the top horizons and positively anomalous in the bottom horizons. This positive anomaly of Ce in the bottom horizons was due to its preferential adsorption on Fe and Mn oxides, relative to other REEs. Although both natural and anthropogenic activi-ties influence the geochemical behaviors of REEs in soils, enrichment or mobility of REEs is low in the natural wetland soil core of the San-jiang Plain.     

Geochemistry of rare earth elements in cobalt-rich crusts from the Mid-Pacific M seamount

Rare earth elements (REEs) and major elements of 25 cobalt-rich crusts obtained from different depths of Mid-Pacific M seamount were analyzed using inductively coupled plasma-atomic emission spectrometer and gravimetric method. The results showed that they were hydrogenous crusts with average ∑REE content of 2084.69 μg/g and the light REE (LREE)/heavy REE (HREE) ratio of 4.84. The shale-normalized REE patterns showed positive Ce anomalies. The total content of strictly trivalent REEs increased with water depth. The Ce content and LREE/HREE ratios in Fe-Mn crusts above 2000 m were lower than those below 2000 m. The change in REE with water depth could be explained by two processes: adsorptive scavenging by setting matters and behaviors of REE in seawater. However, the Ce abundance took no obvious correlation with water depth reflects the constant Ce flux. The Ce in crusts existed mainly as Ce(IV), implying that the oxidative-enriching process was controlled by kinetic factors.     

Effect of rare earth elements on the thermal cracking resistance of high speed steel rolls

The effect of rare earth elements on the thermal cracking resistance of high speed steel (HSS) rolls was investigated. Laser rapid heating was used for thermal fatigue experiments. Thermal cracks and microstructure were observed using metalloscopy and scanning electron microscopy. The results showed that thermal cracks initiated from the interface between the matrix and eutectic carbides (including M6C and M7C3 type carbides),and propagated along the interface between the two phases. MC type carbides enriched with vanadium could prevent the propagation of thermal cracks. The presence of rare earth elements decreased the quantity of big eutectic carbides,and proportionally increased spherical and rod-shaped MC type carbide content. HSS0 (0.00% RE) had approximately three times the thermal cracking density of HSS3 (0.12 wt.% RE). Rare earth elements were shown to significantly improve the microstructure and thermal cracking resistance of HSS rolls.     

稀土处理钢中夹杂物对晶内针状铁素体形成的影响

分析了稀土处理钢中夹杂物的特征(夹杂物种类、尺寸分布和体积分数)对微观组织中针状铁素体形成的影响.结果表明,钢中夹杂物种类和体积分数对针状铁素体组织的形成非常重要.稀土氧化物(包含稀土氧硫化物)与铁素体具有低至1.9%的错配度降低针状铁素体在夹杂物表面的形核能垒,从而促使它在稀土氧化物上形核.反之,稀土硫化物与铁素体具有高达42.5%的错配度不能诱导生成针状铁素体组织.此外,微观组织中针状铁素体的体积分数随着夹杂物体积分数的增加而增大,当钢中夹杂物体积分数是9.5×10^-4时其体积分数达到53%.     

Rare earth elements in tropical surface water,soil and sediments of the Terengganu River Basin,Malaysia

The 14 stable rare earth element(REE) concentrations and distribution patterns were investigated for surface waters(n=51),soils(n=52) and sediments(n=42) from the tropical Terengganu River basin,Malaysia.The chondrite normalized REE patterns of soils developed on four geological units showed enrichment of LREE,a pronounced negative Eu,and depletion of HREE with an enrichment order granite>>metasedimentary>alluvium>volcanic.The REE patterns in sediments reflected the soil REE patterns with an overall order o...     

Effect of rare earth elements addition on thermal fatigue behaviors of AZ91 magnesium alloy

Influences of rare earth (RE) elements addition on thermal fatigue behaviors of AZ91 alloy were studied. Repeated heating and cooling cycles were applied on the samples at 170 and 210 ℃ to develop thermal fatigue cracks. Crack growth mechanisms and microstruc-tural influences were investigated by optical and scanning electron microscopy (SEM) as well as energy dispersive X-ray spectroscopy (EDS). Thermal fatigue behaviors were observed to improve successively by addition of the RE up to 2wt.%. This improvement was attrib-uted to the consummation of aluminum in melt by precipitation of the needle shaped A11IRE3 phases. This process was attributed to the re-duction of Mg17Al12 phase volume fraction and consequent decrease of the brittle Mg/Mg17Al12 interface which was the main reason for weak thermal properties of the alloy at rather high temperatures. Further additions of RE, however, reduced the thermal shock resistance of the samples by increasing the mean length of the brittle needle shaped phases.     

粉末压片-X射线荧光光谱法测定土壤、水系沉积物和岩石样品中15种稀土元素

采用粉末样品压片制样,使用波长色散X射线荧光光谱仪对土壤、水系沉积物和岩石样品中15个稀土元素(La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Y)进行测定。重点探讨了15个稀土元素的测量条件,如分析线、分析晶体,基体效应和谱线重叠干扰校正。使用60余个土壤、水系沉积物和岩石标样建立校准曲线,采用经验系数法和散射线内标法校正基体效应,并用多元回归准确扣除稀土元素谱线重叠干扰。重稀土元素的检出限多在0.2 μg/g以下。对土壤标准样品进行精密度考察,15个稀土元素测量结果的相对标准偏差(RSD,n=10)为0.74%～17%。对土壤、水系沉积物和岩石标准样品进行分析,测定值和认定值一致。     

Comparative study on rare earth elements from Flos Sophorae and Fructus Sophorae

Flos Sophorae and Fructus Sophorae are two kinds of traditional Chinese medicines. In this work, the two kinds of traditional Chi-nese medicines collected from eleven areas of Dezhou, were analyzed by inductively couple plasma-mass spectrometry (ICP-MS) to compare the content and distribution of 14 kinds of rare earth elements (REEs). The method was verified by analyzing GBW07605 certified reference material. The results showed that ICP-MS is an accurate, sensitive and reliable technique for determining REEs in traditional Chinese medi-cine. There were big differences in contents for REEs in Flos Sophorae and Fructus Sophorae from different areas. The contents of total REEs in Flos Sophorae samples from different areas ranged from 1.0785 to 2.2659 g/g, while those in Fructus Sophorae from 0.6826 to 1.0527 g/g. The contents of total REEs in Flos Sophorae samples from different areas were obviously higher than those in Fructus Sophorae of the same area and there was big difference between various Flos Sophorae samples. Interestingly, the higher the content of total REEs in Flos Sophorae samples, the lower the content of total REEs in Fructus Sophorae samples of the same area. The plots of normalized element con-centration versus atomic number showed some characteristic distribution trends. The distribution trend of light REEs (La-Gd) was relatively flat except a positive Eu anomaly, however, that was steep and discrepant for heavy REEs (Tb-Lu). The results could provide a valuable ref-erence for understanding the relationship between the curative mechanism, pharmacology characteristics and their geological condition for the two traditional Chinese medicines investigated.     

EGTA滴定法测定稀土合金中稀土总量

通过对稀土中干扰元素的掩蔽 ,用EGTA对稀土总量进行快速测定     

稀土元素对耐候钢元素偏析的影响

应用金属原位统计分布分析技术(OPA)研究了耐候钢铸锭中C、P、S、Cu、Si和Mn的宏观偏析规律,并分析了稀土元素对耐候钢中元素偏析的影响.结果表明,在30%～40%等轴晶率,20℃过热度下,元素C、S、P和Cu能产生严重的宏观偏析,C、S呈中心正偏析,P、Cu呈中心负偏析并伴随有反偏析,而Si和Mn的分布较为均匀.各个元素中心偏析位置完全相同.稀土元素在钢中的固溶度为10-5～10-4,固溶稀土元素可以细化枝晶,提高等轴晶率.钢中加入质量分数0.38%～0.55%的稀土元素可以有效改善C、S、P和Cu的宏观偏析.     

稀土矿开发过程污染物对土壤生物有效性研究进展

针对稀土矿采用原地浸矿工艺开采稀土过程中大量含有稀土、硫铵以及其他污染物的浸矿残留液进入周边农田土壤环境的现状,总结了国内外不同污染物对土壤生物有效性的研究进展及评价方法,为研究稀土及浸矿剂硫铵对土壤蚯蚓等生物有效性的课题提供理论基础.旨在通过探讨稀土元素及浸矿剂硫铵对土壤生物产生的影响,为稀土矿开发活动破坏周边农田土壤环境的生态评价提供实验依据及参考信息.      

二溴羧基偶氮胂双峰双波长分光光度法测定稀土元素研究

在 1 2mol/LHCl介质中 ,显色剂二溴羧基偶氮胂与稀土元素能发生高灵敏度的显色反应 ,形成稳定的蓝紫色络合物 ,试剂和络合物的最大吸收波长分别位于 5 3 4nm和 63 6nm ,用双峰双波长分光光度法测定痕量稀土总量。结果表明 ,本法有较高灵敏度 ,表观摩尔吸光系数 (La～Eu)达 1.5 4× 10 5～ 1.75× 10 5;在 2 5mL溶液中稀土元素质量在 0～ 2 0 μg范围内符合比尔定律 ;受酸度及共存离子的影响小 ,并具有准确、快速、简便的特点 ;方法回收率达 94.3 %～     

稀土在热喷涂（焊）中的运用

概述了稀土在热喷涂中的作用,着重介绍了稀土对喷涂层的硬度、结合强度、耐磨性、耐腐蚀性、抗氧化性等性能的影响。