岩石土壤及沉积物样品中210Pb-210Bi-210Po的快速联合测定

铀系核素210Pb一210Bi-210Po目前通常采用相对独立的分析技术,三核素分别进行测定,并存在一些技术问题需要解决.文献报道的三核素联测技术需要使用多种昂贵的测试设备和示踪剂,或者制源体系抗干扰能力较弱且分析周期较长.本文研究了210Bi、210Po同时且定量恒温自沉积于铜箔的最佳制源条件,建立了双样-两次铜箔恒温自沉积制源-总α、总β同时计数法快速联合测定岩石、土壤及沉积物样品中210Pb-210Bi-210Po的分析技术.结果表明,当铜镀片面积为3.14 cm2,盐酸浓度为0.5 mol/L,氯化钠浓度为3.5 mol/L,溶液体积为20 mL,恒温90℃,振速为120 r/min,振幅20 mm,制源70 min,210Bi和210Po可同步定量自沉积且210Pb不沉积.在抗坏血酸存在下,大量共存元素不干扰自沉积.方法的精密度优于5％,全程加标放化回收率在99.5％～100.5％之间.该联测技术采用的制源体系抗稳定铋干扰能力较强,回收稳定,分析周期短,仅需一台国产测试设备并无需示踪剂即可完成三核素联合测定,同时也适合于三核素的独立测定.     

镍箔恒温自沉积总α、总β计数法同时或连续测定样品中210Pb、210Bi、210Po

研究了210Bi、210Po同时恒温自沉积于镍箔的最佳制源环境,建立了岩石、土壤以及水体样品中210 Pb、210 Bi、210 Po同时或连续测定的方法——镍箔恒温自沉积总α、总β计数法。试验发现,当镍镀片面积为3.14cm2,盐酸浓度为1.0mol/L,溶液体积为25mL,恒温90℃,振荡频率180次/min,振幅20mm,制源60min,210Bi和210Po可同步定量自沉积。210 Po加入量与总α净计数率相关系数为0.9998,210Bi加入量与总β净计数率相关系数为0.9997。放置衰变法可以消除Bi和Po其它短寿命放射性同位素对测量产生的影响,盐酸肼及酒石酸存在时大量共存离子不干扰测定。方法的精密度优于5%,全程加标回收率在99.5%～100.5%。     

一次分解试样测定地质样品中~(230)Th,~(232)Th和~(234)U/~(238)U,~(230)Th/~(232)Th

试验了用~(234)Th示踪,一次分解试样测定~(234)Th,~(232)Th和~(234)U/~(238)U,~(230)Th/~(232)Th的快速方法。试样经Na_2O_2熔融分解,并以P350萃取色层法分离铀、钍。然后分别电沉积制备无自吸收铀、钍α源进行α谱测量。本法适用于铀矿石、岩石和土壤试样的测定。     

岩石、土壤样品中210Po测定方法的研究

研究了以铜箔为镀片时,自沉积总α计数法定量测定岩石、土壤样品中210Po的最佳制源环境、同位素的干扰和去除、共存元素的允许量以及适宜的溶(熔)矿方法,同时研究了银、铜两种镀片的区别。试验发现,当盐酸浓度为2.0mol/L,恒温80℃,振荡频率为180次/min、振程20mm时,制源2.0h,210Po自镀回收率在99.6%～100.4%之间,210Po加入量与α净计数率线性相关系数为0.9999。放置衰变法可以消除212Bi和218Po等短半衰期核素对210Po测量产生的影响,Vc存在时其它共存元素不干扰测定。方法配合HNO3HFHClO4溶矿(对复杂试样酸溶后的不溶渣,再进行碱熔),全程回收率为99.5%～100.4%。     

莱州湾沿岸地下浓缩海水高浓度铀的发现及地球化学异常

该成果利用目前最灵敏、准确、快速的激光铀分析仪对莱州湾沿岸地下浓缩海水中的铀进行了调查研究。发现该区地下浓缩海水中的高浓度铀一般为天然海水中铀浓度的5—30倍。浓度低的约为20μg/L,最高约达100μg/L。铀浓度变化由西向东逐渐增加,在岔河盐场出现高峰,然后又逐渐降低;地下浓缩海水中的高铀浓度与海水中铀浓度的关系不象其它化学成份(主要指常量元素)那样与地下浓缩海水的浓度近似成正比(一般为3—5倍,而铀浓度大都高于此倍数);从不连续抽水和连续抽水试验可说明,不连续抽水时,潜水层浓缩海水浓度较低(12.9°Be’),铀浓度为50μg/L;连续抽水时则为承压层,浓缩海水浓度高,铀浓度也高为80μg/L,说明承     

膜蒸馏处理糠醛废水的实验研究

采用中空纤维膜蒸馏技术研究了糠醛废水的膜蒸馏处理效果,考察了料液相的温度、醋酸浓度、流速、吸收液浓度等因素对处理效果的影响。结果表明：在温差为15℃、料液的浓度为0.306 mol/mL时,速度为8 mL/min;吸收液的质量浓度为25 g/L时,速度为3 mL/min。运行12 h后,料液的pH值由开始的1.9升高为5.1,醋酸的去除率为76.3％,糠醛的去除率为40.1％。此过程可降低料液中糠醛和醋酸的含量,减小了低分子量有机酸对微生物危害的影响,为后续生物处理奠定了基础。     

白龙江下游涉核地区水的放射性环境水平现状调查

通过白龙江下游涉核地区水的放射性环境水平调查,得出白龙江下游涉核地区的区域内水中铀、镭浓度普遍较低。U含量在0.35～5.42μg/L,Th含量水平极低,Ra在0.36～1.32Bq/L之间。通过分析,水中铀、镭浓度的相关性不一致,可知道在某些河段的铀、镭平衡已经被破坏,成为偏镭系的铀、镭平衡。     

应用中子活化分析技术测定铀和钍放射性同位素的α能谱内标法

开发了一种用＾２３８Ｕ和＾２３２Ｔｈ作为内标的α能谱测定铀和钍放射性同位新方法。应用中子活化分析技术精确地测定样品中的＾２３８Ｕ和２３２Ｔｈ。将其他部分样品全部溶解,采用阴离子交换法分离铀和钍,制备为α能谱测定的电镀薄（低强度）源。人已知的＾２３８Ｕ和＾２３２Ｔｈ质量浓度,求得它们的活度浓度,之后据α能谱,从Ｕ（＾２３Ｕ、＾２３５Ｕ、＾２３８Ｕ）和Ｔｈ（＾２２８Ｔｈ、＾２３０Ｔｈ、２３２Ｔｈ）放射     

用萃取色谱法测定地质样品中的铀和钍

本文推荐一种用萃取色谱法测定地质样品中的铀和钍的方法。溶样后，用Fe(OH)3沉淀法预富集铀和钍，再用UTEVA树脂分离，使分离的铀和钍电沉积在不锈钢圆盘上，再用α能谱法测定。用晶质铀矿、珊瑚和花岗岩标准物质评价该法。测得的铀和钍含量及^234U/^238U和^230Th/^234U活性比值与标准值十分一致。发现钚的存在会干扰分离，但利用氨基磺酸亚铁还原就可解决此问题。该法的化学回收率与阴离子交换法相近，但萃取色谱法能用较少试剂进行较快分离。     

砂岩铀矿成矿过程与氧化还原分带: 铀系不平衡证据

铀系不平衡技术被用来研究新疆伊犁盆地库捷尔太砂岩型铀矿床的氧化还原分带和成矿过程.取自该矿床的26个样品的铀、钍含量以及234 U/ 238U, 230 Th/ 234 U和230 Th/ 238U活度比值分别用ICP -MS和α能谱仪进行了测量.不同氧化还原带岩石的铀、钍含量和钍/铀比明显不同: 强氧化带岩石的U、Th含量和Th/U比分别为12.4 μg/g, 4.5 μg/g和0.48; 弱氧化带分别为20.4 μg/g, 5.0 μg/g和0.38; 过渡带(矿化带)分别为169.7μg/g, 4.7μg/g和0.07; 还原带(未蚀变带)分别为6.8μg/g, 3.7μg/g和0.87.其同位素特征亦有明显差异: 氧化带岩石234 U/ 238U大多大于1, 过渡带(矿化带)岩石部分大于或等于1, 部分小于1, 还原带(未蚀变带)岩石大多大于1; 氧化带岩石230 Th/ 234 U和230 Th/ 238U大多大于1, 过渡带(矿化带)岩石大多小于或等于1, 还原带(未蚀变带)岩石大多大于1.这可作为砂岩型铀矿床矿体定位的指示剂.铀系不平衡特征还示踪了该矿床的成矿作用过程.      

同位素测定样品中钙和锶的分离

与样品中基体和Rb分离了的Ca和Sr,在0.08mol/L柠檬酸-1.5mol/L NH_4OH介质中流经Dowex50×8阳离子树脂柱,并用此溶液淋洗Ca,用4mol/L HCI洗脱Sr。收集的含Sr溶液用于同位素年龄测定,消除了质谱测定过程中Ca的干扰。     

Studies on the recovery of uranium from nuclear industrial effluent using nanoporous silica adsorbent

In this paper, the sorption of uranium onto nanoporous silica adsorbent in the presence of nitrate, sulfate, chloride, fluoride and phosphate was studied. The effect of contact time between the nanoporous sorbent and aqueous solution, pH and initial concentration of uranium was also investigated. Uranium sorption onto nanoporous silica adsorbent is a very fast process as sorption rate increases with pH increment. Optimum pH for uranium sorption was 4?C8. Experimental sorption isotherm is successfully described by Langmuir and Freundlich models. The results obtained by batch experiments showed that the presence of high concentration of nitrate, sulfate, chloride and phosphate anions alone had no interference with uranium recovery. However, the presence of fluoride ions (>250?mg/L) decreases uranium sorption by about 55?%. The results also showed that the presence of phosphate ions (about 300?mg/L) in solution could remove fluoride interference completely. Finally, the efficiency of the nanoporous silica adsorbent for uranium recovery from wastewater of the uranium conversion facility was investigated.     

微量磷灰石中磷酸根氧同位素分析方法

生物磷灰石壳体的磷酸根氧同位素组成是重建古温度理想指标之一,在古环境研究中具有重要意义.针对牙形石等磷灰石量极少的情况,稳定可靠的前处理方法是分析其δ18O_PO4的重要保障,目前仅有少数国外实验室已建立了相关提取分析方法.结合这些方法的优缺点对分析步骤进行改进优化,建立了微量磷灰石的磷酸根氧同位素分析方法,通过硝酸消解磷灰石并除去非磷酸根氧,利用KF溶液沉淀法分离Ca2+,采用氨缓冲溶液形式调节pH,并加入AgNO₃溶液以氨挥发法将PO₄3-转化成Ag₃PO₄结晶分离,气体稳定同位素质谱仪在线测定Ag₃PO₄氧同位素组成.结果表明,方法全流程未产生明显的氧同位素分馏,样品最低仅需0.2 mg,标准偏差小于0.2‰（1σ）,与目前国际报道的分析精度一致.      

热表面电离质谱法测定贫化铀样品痕量铀同位素比值及含量

选用磷酸为离子流发射剂,热表面电离质谱法分析纳克量级贫化铀样品的铀同位素比值,方法最大相对标准偏差2.9%。以233U为稀释剂,采用同位素稀释法对铀的含量进行测定,扩展不确定度为2.4%(K=2)。研究表明,在纳克量级的铀同位素比值测定中,来自铼带等铀本底的干扰影响不容忽视,需要进一步研究并扣除。     

钼同位素的MC-ICP-MS测定方法研究

本文报道了运用多接收器等离子体质谱进行Mo同位素组成测定的方法, 测定过程中的仪器质量歧视校正采用样品－标样交叉法。实验对Mo同位素测定过程中的谱峰干扰、基体效应、浓度效应、酸度效应和重现性等问题进行了详细研究。结果表明Zr的存在对Mo同位素测定不会产生影响; Sr不适合作为Mo同位素测定的元素内标; 当m(Ag)/m(Mo)≤1时, Ag的存在不会对Mo同位素测定产生影响; 当样品相对于标样的Mo浓度变化不大于50%时, Mo同位素分析不受浓度影响; 以HNO3为进样介质时, HNO3的浓度(0.1 mol/L~0.2 mol/L)对Mo同位素分析没有影响。CAGS-Mo相对于Alfa-Mo的δ100/95Mo、δ98/95Mo和δ97/95Mo分别为－0.34‰±0.10‰(2sd)、－0.22‰±0.05‰(2sd)和－0.13‰±0.08‰(2sd), 在95%的置信区间内, 该方法的外部精度不大于0.06‰/amu。     

高REE-Nb-Fe-Mn样品Mg同位素测定的化学分离方法

利用多接收电感耦合等离子体质谱仪测定Mg同位素比值时,样品溶液中的基质元素可影响Mg同位素比值的准确测定。根据白云鄂博样品富含REE、Nb、Fe(REE质量分数可达10%、Nb质量分数可达0.1%)等元素的特性,本研究在评估测试溶液中Nd(REE)、Mn元素质量比对Mg同位素比值影响的基础上,建立了适用于富含REE、Nb、Fe等元素的特殊样品中Mg同位素的化学纯化方法。研究表明,当m（Nd）/m（Mg）>0.2、m（Mn）/m（Mg）>0.2时,REE和Mn的存在明显影响Mg同位素测定值的准确性,应予以去除。所建纯化方法首先是利用AG MP-1阴离子交换树脂,以10 mol/L HCl+0.001% H₂O₂溶液为上样介质和淋洗液,接取前2.5 mL淋洗液,去除样品中 Fe、Mn等杂质元素;然后利用AG50W-X12阳离子交换树脂,以2 mol/L HCl为上样介质和淋洗液,去除REE、Nb等杂质元素。所建方法满足多接收器等离子体质谱进行高REE-Nb-Fe-Mn样品中Mg同位素测定的要求。     

Application of Uranium Isotope Chronology for Partical Comminution in the Eolian Dust System

The wind dust system is an important part of the terrestrial surface system and plays an important role in many key belts. The mechanism of wind dust and the handling process are important to understand the environmental function of wind dust and to interpret the paleoclimate record. In the past, traditional geochemical methods can only reflect the rock composition or age in the final denudation zone, and it is not possible to distinguish the different silt mechanism and the intermediate process under the same eventual source background, which is one of the biggest challenges of the present research. The ²³⁴U/²³⁸U ratio of fine matter caused by alpha decay recoil reflects the time experienced by the particle since it was broken and may be able to effectively trace the mechanism of wind dust generation and the transport of the intermediate process, but the age of uranium isotope fragmentation is rarely used in the wind dust system. The complicated factors restricting the wide application of uranium isotope were summarized, and according to the latest research progress, the verification and development of the uranium isotope comminution age in the wind dust system, and the problem solution of the mechanism of wind dust production and the way of transporting were discussed.     

Ion-exchange fractionation of copper and zinc isotopes

Whether transition element isotopes can be fractionated at equilibrium in nature is still uncertain. Standard solutions of Cu and Zn were eluted on an anion-exchange resin, and the isotopic compositions of Cu (with respect to Zn) of the eluted fractions were measured by multiple-collector inductively coupled plasma mass spectrometry. It was found that for pure Cu solutions, the elution curves are consistent with a ⁶³Cu/⁶⁵Cu mass fractionation coefficient of 0.46‰ in 7 mol/L HCl and 0.67‰ in 3 mol/L HCl between the resin and the solution. Batch fractionation experiments confirm that equilibrium fractionation of Cu between resin and 7 mol/L HCl is ∼0.4‰ and therefore indicates that there is no need to invoke kinetic fractionation during the elution. Zn isotope fractionation is an order of magnitude smaller, with a ⁶⁶Zn/⁶⁸Zn fractionation factor of 0.02‰ in 12 mol/L HCl. Cu isotope fractionation results determined from a chalcopyrite solution in 7 mol/L HCl give a fractionation factor of 0.58‰, which indicates that Fe may interfere with Cu fractionation.Comparison of Cu and Zn results suggests that the extent of Cu isotopic fractionation may signal the presence of so far unidentified polynuclear complexes in solution. In contrast, we see no compelling reason to ascribe isotope fractionation to the coexistence of different oxidation states. We further suggest that published evidence for iron isotopic fractionation in nature and in laboratory experiments may indicate the distortion of low-spin Fe tetrahedral complexes.The isotope geochemistry of transition elements may shed new light on their coordination chemistry. Their isotopic fractionation in the natural environment may be interpreted using models of thermodynamic fractionation.     

The adsorption of glyphosate and phosphate to goethite: a molecular-scale atomic force microscopy study

The adsorption of glyphosate and phosphate to the goethite {010} surface (Pbnm notation) was studied using an atomic force microscope (AFM). The microscope was capable of producing molecular scale images of surfaces exposed to glyphosate, phosphate and nitric acid. In 0.08 mol/L HNO₃ solution with pH of 1, the goethite {010} surface displayed the periodicities of the surface unit cell. The presence of a secondary periodicity in the 2D-Fourier transform suggests that the surface relaxes or reconstructs slightly, either after cleavage or as a result of exposure to air or acid solution. Images obtained in 0.01 mol/L glyphosate solution with pH of 2.5 displayed a well-defined √2 × √2 superstructure and a somewhat diffuse √2 × 2√2 superstructure that alternated in orientation within single imaging areas. The √2 × √2 superstructure indicates that glyphosate functional groups adsorb in a 1:2 ratio with the singly coordinated hydroxyl groups and suggests that all functional groups coordinate similarly. The √2 × 2√2 superstructure is interpreted to originate from different behaviour of the tip during imaging of the adsorbed phosphonic and carboxylic groups, indicating that both groups coordinate to the surface and that the glyphosate molecule bridges the rows of singly coordinated hydroxyl groups. In 0.01 mol/L phosphate solution with pH of 2.6, the imaged pattern was identical to that obtained in HNO₃. The similarity suggests that phosphate adsorbs in 1:1 ratio with the singly coordinated hydroxyl groups and that phosphate thus coordinates monodentately. The relative maximum adsorption density of phosphate and glyphosate on the {010} surface expected from the AFM data was in agreement with that determined with X-ray photoelectron spectroscopy (XPS).     

Comparison of Pb Purification by Anion-Exchange Resin Methods and Assessment of Long-Term Reproducibility of Th/U/Pb Ratio Measurements by Quadrupole ICP-MS

A comparison between HBr-HCl and HBr-HNO₃ based anion chemistry is presented to test the efficiency of Pb purification in the preparation of samples for isotope ratio measurement by ICP-MS. It was found that the small advantages in yield and blank offered by the HNO₃-based method were more than compensated by the more effective matrix removal of the HCl-based method. Apart from very zinc rich matrices (e.g., sphalerite), a careful single pass purification using HBr and HCl removed more than 99.9% of the matrix. In preparation for the isotope ratio analysis, a small (2–5% m/v) liquid sample aliquot was analysed to determine U, Th and Pb concentrations by solution quadrupole ICP-MS. This allowed accurate prediction of the expected ion signal and permitted optimal spiking with Tl, if desired, for mass bias correction. Long-term results for international rock reference materials showed reproducibilities of better than 1% (Th/U) and 1.5% (U/Pb). For most geological applications, such analyses obviate the need for isotope dilution concentration measurements.