模拟降雨对铀尾矿中U、Sr、Mn、Fe释放规律的影响

为查明某铀尾矿中U、Sr、Mn和Fe等4种元素在模拟降雨下的释放规律,在研究铀尾矿中4种元素赋存状态的基础上,采用静态浸出和动态淋滤的方法对铀尾矿溶浸特征进行研究.结果表明,铀尾矿中U、Sr、Mn和Fe的赋存总量分别为:30.4、122.0、523.0、9700.0μg·g~(-1),其中U、Mn迁移活性最强,Sr次之,Fe最弱.在静态浸出过程中,除Fe的浸出量与pH值相关性不明显外,U和Mn的浸出量随pH值增加而减少,Sr的浸出量随pH值增加而增加;动态淋滤过程中,各元素都表现出释放速率随淋滤时间增长而减小,淋滤初期pH值对Mn和Sr的累计释放量影响不显著,但淋滤后期pH值对其累计释放量影响显著.     

伊利石对水溶液中低浓度铀的吸附

采用静态实验方法研究了伊利石对水溶液中铀的吸附特性,通过批实验考察了反应时间、溶液初始浓度、p H值、离子强度、固液比以及温度对吸附的影响,用傅里叶变换红外光谱仪(FTIR)、X射线衍射仪(XRD)表征伊利石吸附铀前后结构的变化,探讨了伊利石对铀的吸附等温方程和热力学规律,分析其反应机制.实验结果显示,伊利石与低浓度铀溶液接触后立即反应,1 h后反应基本达到平衡;溶液p H和离子强度对伊利石吸附铀的影响显著,当p H=4—7、离子强度为0.001 mol·L-1时,吸附效果最好;在一定条件下,伊利石对水溶液中低浓度铀的吸附量与铀初始浓度呈正比,与固液比呈反比;吸附等温线符合Freundlich模型,相关系数可达0.9966;伊利石对铀的吸附属于吸热反应,反应自发进行,高温促进伊利石的吸附行为.     

改性腐殖酸对铀的吸附的试验研究

通过静态吸附实验,探讨了改性HA对U(Ⅵ)吸附影响。考查pH值、时间、U(Ⅵ)的初始浓度和温度等对吸附的影响。结果表明:pH值对改性腐殖酸的吸附效果影响较大,改性腐殖酸吸附U(Ⅵ)的最佳pH值为6,最大去除率为99.37%,吸附在60 min内基本达到平衡。UO22+在改性腐殖酸上的吸附是放热过程,符合Freundlich等温吸附方程,相关系数达0.99以上,表明IHA对铀的吸附是以表面为主要吸附位,并不是均匀的单层吸附。图8,参9.     

地下水铀污染与饮用水中铀的健康风险

铀广泛存在于地壳中,是一种重要的战略资源.受自然和人为因素影响,铀可以被释放到天然水体中,造成地下水的铀污染,进而带来潜在的生态环境与人体健康风险.作为一种锕系元素,铀同时具有放射毒性与化学毒性.由于铀的天然同位素均具有较长的半衰期,且自然环境中铀的人体暴露具有低剂量、长周期的特点,地下水铀污染的健康风险主要体现为化学...     

聚硅氧烷包膜对磁黄铁矿尾矿重金属溶出的影响

通过用不同pH的3%双氧水分别浸泡原始尾矿和聚硅氧烷包膜处理尾矿,研究了包膜剂浓度,浸泡时间,浸泡介质pH对尾矿中重金属溶出的影响,并利用红外光谱法对改性前后的尾矿进行表征.结果表明选择包膜剂浓度为10%-15%时效果最佳;在3%的双氧水中浸泡1周的时间内,包膜剂对尾矿中重金属离子的溶出都有较大影响,抑制Cr、Mn、C...     

矿物质与矿物离子对煤中硒释放行为的影响

利用固定床热解反应装置研究了煤中不同类矿物质及不同矿物离子(Ca2+、Si4+、Al3+、Mg2+)对黑代沟烟煤、霍林河褐煤及各自的酸抽提(HCl、HF、HNO3脱矿物质)样品中硒释放行为的影响.研究发现,热解过程中,碳酸盐、硫酸盐、单硫化物、磷酸盐与氧化物(HCl脱除的矿物质)抑制了两种煤中硒的释放,且对黑代沟烟煤中硒释放的抑制作用较强;铝硅酸盐类(HF脱除的矿物质)对两种煤中硒释放的抑制作用均较强;而煤中黄铁矿类(HNO3进一步脱除的矿物质)在其分解转化过程中会形成更加稳定的新物质而抑制硒的释放.担载的Ca2+、Si4+、Al3+、Mg2+对黑代沟与霍林河煤的HCl/HF-抽提样品中硒的释放均有抑制作用,但作用的强弱顺序不同.对黑代沟煤为:Ca2+>Si4+>Al3+>Mg2+,而对霍林河煤为:Ca2+>Al3+>Si4+>Mg2+.     

某铀矿区农田土壤重金属生物有效性分析

为探究某铀矿区附近农田土壤的重金属生物有效性,以该铀矿采矿区、冶炼厂和尾矿坝附近农田土壤为研究对象,分析土壤理化性质并采用经改良后的BCR四步提取法对土壤重金属Pb、Cd、Cr、Cu和U生物有效性进行评估。结果表明:研究区农田土壤偏酸性;不同区位农田土壤有机质含量由大到小依次为尾矿坝、冶炼厂和采矿区;重金属赋存形态主要为残渣态;重金属元素Pb、Cd、Cr和Cu生物有效态含量分别占其总含量的27%～42%,放射性核素U生物有效态含量为U总含量的43%～45%;不同区位农作物对重金属Cr、Cd、Cu和Pb富集系数由大到小依次为采矿区、冶炼厂和尾矿坝;各区位农作物对U的富集效果均最强。综上,研究区农田土壤重金属生物有效性受pH值、有机质含量及重金属生物有效态含量等因素的综合影响,重金属生物有效性越强,其引起的生态风险越大;不同区位农田土壤中重金属Cr、Cd、Cu和Pb生物有效性由大到小依次为采矿区、冶炼厂和尾矿坝;不同区位农田土壤重金属中U的生物有效性均最强;由于受提炼铀矿石的影响,冶炼厂相较于其他研究区域具有更强的U生物有效性;虽然尾矿坝农田农作物对重金属元素的富集效果较差,但考虑到该区位土壤重金属含量较大,其带来的生态风险仍值得关注。研究结果可为今后该矿区重金属污染的科学生物防治提供重要理论依据。     

磷酸二氢钠去除铀的效果与机理

通过静态实验,研究了不同反应时间、p H值、初始铀浓度、磷酸二氢钠用量、温度等因素对磷酸二氢钠去除溶液中铀的效果的影响,并结合红外光谱、扫描电镜和热重分析等测试结果,探讨了磷酸二氢钠去除铀的机理.结果表明,一定质量的磷酸二氢钠对铀的去除量随着铀初始浓度的增大而增大,随着温度的升高而减小;在p H值为5,磷酸二氢钠用量为2.0 mg时,磷酸二氢钠去除铀的效果最好,铀的去除率高达99%以上;反应在120 min基本达到平衡.红外光谱分析说明磷酸二氢钠主要是通过磷酸二氢根与UO2+2发生络合反应去除溶液中的铀,扫描电镜分析显示反应生产了矿物晶体,热重分析可知该矿物晶体具有很好的热稳定性.     

某铀尾矿库周边地下水的水化学特征分析

选取某铀尾矿周边地下水作为研究对象,对比分析地下水与排放水在主要水化学成分、水化学参数、水化学类型及放射性元素铀和微量元素氟含量上的差异,探明铀尾矿库对其周边地下水的影响程度.分析结果表明:地下水主要水化学成分为HCO-3和Na+,水化学类型以HCO3·Cl-Ca·Na为主,排放水主要水化学成分为SO2-4和Ca2+,水化学类型以SO4-Ca为主.说明在主要水化学成分、水化学参数、水化学类型上,可能尾矿库对地下水的影响不大;地下水中铀和氟含量分别超过美国EPA标准和我国《地下水质量标准》,超标率分别为100%和85.7%.可能是受矿山开釆产生的废石和铀尾矿库堆积的矿砂及p H的影响,说明尾矿库对地下水铀、氟含量的增加有一定影响.     

铀在地表水中的主要迁移形式及其沉淀条件的模拟计算——以四川沱江流域绵远河为例

通过对沱江流域绵远河地表水系中化学成分分析,考察了铀及其他元素含量的空间分布特征.利用热力学方法计算了地表水系中U的迁移形式,及水体中不同U络合物的活度及比例.结果表明,地表水中铀主要以UO2(CO3)2-2形式迁移和存在,其次为UO2(CO3)0、UO2(CO3)4-3和UO2(OH)2.沱江流域绵远河水系自上游至下游各样品中U络合物活度百分比组成基本相同,U的溶解和迁移形式类似,物化性质(温度、压力、pH值、Eh等)没有发生明显变化.通过对影响U沉淀的物理化学条件的热力学计算,分析了铀在表生水体中的沉淀条件,较高的pH、Eh值将有利于U络合物在水系中稳定存在和迁移,而较低的pH、Eh值将会使水系中的U发生沉淀.     

Efficient uranium immobilization on red clay with phosphates

Uranium is a very toxic and radioactive element. Removal of uranium from wastewaters requires remediation technologies. Actual methods are costly and ineffective when uranium concentration is very low. Little is known about the enhancement of sorption of uranyl ions by phosphate ions on aluminosilicates. Here, we studied sorption of uranyl acetate on red clay in the presence of phosphates. The concentration of U(VI) ranged 0.0001–0.001 mol/L, whereas the concentration of PO₄ ^3? was constant at 0.0001 mol/L. We designed a new method for the analysis of ternary surface complexes. We observed for the first time a remarkable improvement of U(VI) sorption on red clay under the influence of phosphates. We also found that at least two different ternary surface complexes U(VI)–phosphate–clay are formed in the sorbent phase. The complexation of UO₂ ²⁺ cations by phosphate ligands in the sorbent phase was confirmed by the X-ray photoelectron spectra of U 4f electrons.     

Efficient phytoremediation of uranium mine tailings by tobacco

This investigation shows that tobacco plant roots and leaves accumulate 60?times more uranium than previously reported. Phytoremediation is a convenient technique to clean up polluted soils using herbaceous plants and trees. Increasing research aims to identify novel plant species that accumulate toxic metals. Tobacco plant (Nicotiana tabacum L.) is a promising cultivar for phytoremediation because tobacco is fast growing and easily propagated. Here, we study phytoremediation of uranium by two tobacco varieties Virginia and Burley, bred in natural conditions. Plants were grown on uranium mine tailings with an average uranium content of 15.3?mg?kg^?1. Each shoot sample was cross-sectioned into five uniform groups of leaves and stem segments. Results show a substantial variance in uranium uptake according to the section elderliness and origin of the plant parts. The highest concentrations of uranium values recorded in leaves of Burleys and Virginias nearest root shoot sections were 4.18 and 3.50?mg?kg^?1, respectively. These values are 60?times higher rates than those previously published for leaves of cultivars grown under similar conditions. Taking into account the level of soil contamination, the content of accumulated uranium demonstrates uranium hyperaccumulatory properties of tobacco plant and its potential utilization in phytoremediation of uranium-contaminated mediums.     

Toxicity of depleted uranium on isolated liver mitochondria: a revised mechanistic vision for justification of clinical complication of depleted uranium (DU) on liver

Depleted uranium (DU) is widely used in military anti-armor weapons. Recent evidence suggested that oxidative stress and mitochondrial dysfunction may contribute to DU-induced toxicity. However, the underlying mechanisms of DU toxicity in mitochondria are not well understood. In this study, liver mitochondria were obtained from Wistar rats treated with DU in the form of uranyl acetate (UA) (0.5, 1 or 2 mg/kg i.p.) using differential centrifugation. For in vitro experiments, control rat liver mitochondria were incubated with different concentrations of UA (50, 100 or 200 μM) for 1 hr. Mitochondrial reactive oxygen species (ROS) production, collapse of mitochondrial membrane potential, and mitochondrial swelling were examined by flow cytometry. Mitochondrial sources of ROS formation were determined using specific substrates and inhibitors. Extent of lipid peroxidation (LPO) and glutathione (GSH) oxidation, and also complex II and IV activities were detected via spectroscopy. Further, the concentration of ATP and ATP/ADP ratio was measured using luciferase enzyme and release of cytochrome c from mitochondria which was detected by ELISA kit. UA induced succinate-supported mitochondrial ROS production, elevated LPO levels, GSH oxidation, and mitochondrial complex II inhibition. UA also induced mitochondrial permeability transition and increase in cytochrome c release which subsequently disturbed oxidative phosphorylation and reduced the mitochondrial ATP concentration. Data suggest that mitochondrial oxidative stress and uncoupling of oxidative phosphorylation may play key roles in DU-induced hepatic toxicity.     

Redox potential and uranium sorption onto sediments: kinetic and thermodynamic characteristics

ABSTRACT

The effects of the flooding and initial Eh of sediments on the sorption of uranium onto the sediments were analysed by flooding and static experiments. The changes in uranium species with Eh and kinetic and thermodynamic characteristics of the uranium sorption onto the sediments were investigated. The flooding experiment indicates that the initial Eh of the sediment gradually decreased with the increase in flooding time. Based on the redox potential in the flooding experiment, simulation results obtained using the geochemical simulation software PHREEQC show that the concentration of U (VI) decreased. In contrast, the concentrations of U (III), U (IV), and U (V) gradually increased. The pseudo-second-order kinetic model well fitted the experimental data, which shows that the sorption was mainly chemical sorption. The thermodynamic parameters suggest that the entropy and enthalpy under the used conditions were positive and that ΔG^θ was negative. A thermodynamic analysis shows that the sorption was endothermic and spontaneous. These results are useful for the understanding of the sorption mechanism and migration of uranium onto the sediment under different initial sediment redox potentials and provide a good theoretical foundation for radioactive pollution remediation.     

Soil uranium,basement radon and lung cancer in Illinois,USA

Using counties as the sampling unit, a significant association between the chemical form of uranium occurring in soils with basement radon levels was found (Spearman r, 0.266; p > |r|, 0.007). Uranium atoms dispersed throughout the soil matrix are efficient emanators of Rn to soil gas, whereas Rn that is trapped diffuses very slowly from the several U-bearing minerals in Illinois soils and does not contribute significantly to explaining basement Rn. Basement Rn level is correlated with annual incidence of male and female lung cancers. Dispersed U is correlated with annual incidence of lung cancer in females with a Spearman correlation coefficient of 0.162 (p > |r|, 0.104) and males of 0.177 (p > |r|, 0.075).     

Redistribution of uranium by physical processes during weathering and implications for radon production

Erosion of the Edale shales of Derbyshire during the Tertiary and Quaternary has resulted in sediment deposits in and on the underlying karstified limestones. Sorting during sedimentation has generated clay-rich sediments which are uranium enriched due to a clay association of uranium in the shales. Radon production in these sediments is at or close to equilibrium with their uranium content, and their fine grain-size ensures efficient radon release. Such sediments are therefore potent local sources of environmental radon.     

华南某铀矿开采利用对地表水环境质量的影响

以广东省某铀矿区为研究对象,利用电感耦合等离子体发射光谱仪(ICP-OES)测定了矿山、水冶厂及其周边地表水体共42个水样(包括工业废水、池塘水、溪流水、河水和矿区饮用水)中放射性元素(U和Th)和其它一些金属元素(Fe、Mn、Mg、Cu、Zn、Co、Ni、Li、Ca、Na、K、Al、Sr和Ba)的含量.由此确认铀矿区产生高污废水的重要环节和关键污染元素,并了解这些元素的迁移变化规律以及对周边地表水产生的影响.结果表明:(1)铀矿区产生高污外排废水的主要生产环节是采矿、铀矿堆浸和尾矿露天堆积,排放废水中U和Mn含量分别为0.238—8.700 mg.L-1和0.62—94.23 mg.L-1,均高于国家工业废水允许排放标准(GBJ8—74和GB8978—1996)的限定值;(2)铀矿周边用作当地农业灌溉和露天水源的溪流由于受纳了矿区外排废水,明显受到了U和Mn的污染:U含量在枯水期和丰水期分别为(0.415±0.619)mg.L-1和(0.233±0.308)mg.L-1,Mn含量在枯水期和丰水期分别为(8.72±12.8)mg.L-1和(8.56±12.61)mg.L-1;(3)受纳溪流中U、Fe的含量枯水期高于丰水期,而Mn和Cu的含量基本保持不变,且大多数元素的含量随着迁移距离的增加在枯水期和丰水期均呈下降趋势,指示污染源来自铀矿区;(4)铀矿区生产活动引起的地表水污染目前仅局限于铀矿区和周边较小的区域,但仍应引起重视.     

Effect of uranium on growth and reproduction of the marine amphipod Allorchestes compressa

Experiments on growth of the marine amphipod Allorchestes compressa Dana were carried out over four weeks, and both growth and reproduction were studied over three generations, each of which was exposed to uranium for approximately 10 wk. At 0.1 mg l^-1 the uranium increased growth by 23%, as measured by the mean weight after 4 wk, and at 2 mg l^-1 growth was reduced by 28% compared with the control. A. compressa accumulated uranium from sea water with a concentration factor of 10. There was no effect of uranium on the survival of amphipods or their progeny in the multiple-generation experiment, but the numbers of males, the sex ratio, and the respiration rate (measured on males only) at 1mg l^-1 were significantly lower than the control. A. compressa is shown to be a convenient species for the study of toxic effects on growth and reproduction using multiple-generation experiments.