体积含水率对铀尾矿氡析出率影响的试验研究

选取我国南方某铀尾矿库的自然尾矿样品,分析了其粒径分布和主要化学成分,设计并制作了测定铀尾矿氡析出率的室内试验装置,采用RAD7氡检测仪测定氡浓度,SM200水分仪测定铀尾矿的体积含水率,并阐述了试验步骤。采用对照试验的方法研究了体积含水率对铀尾矿氡析出率的影响规律。结果表明,随着体积含水率的增加,氡的析出率先上升,当铀尾矿体积含水率达到10%~12%时,氡析出率最高;之后,氡析出率随着铀尾矿体积含水率增加而下降。     

对新疆某铀伴生煤矿辐射环境影响分析及污染防治探讨

通过对新疆某煤矿辐射环境影响问题的调查与分析,阐明铀伴生煤矿对周围环境存在着不同程度的放射性影响,并在调查与分析的基础上,针对调查煤矿日前存在的问题提出了一些污染防治的对策和措施,以期为今后伴生放射性煤矿的环境管理决策提供有力依据。     

接种丛枝菌根真菌对蜈蚣草吸收铀的影响

采用盆栽土壤实验,模拟铀(uranium,U)污染土壤,以蜈蚣草(Pteris vittata L.)为研究材料,每盆接种丛枝菌根真菌地表球囊霉(Glomus versiforme,Gv)30 g,探索蜈蚣草菌根对U污染土壤不同时间段的修复效果.结果表明,蜈蚣草菌根侵染率2013年9月最低为57.14%,2014年3月最高为75.20%,呈先上升后下降的年周期变化规律;同一时期蜈蚣草的生物量(干重)Gv组显著高于CK组,根系最为明显;接种Gv组蜈蚣草各器官总U含量均显著高于CK组,且被吸收的U主要固定在根部,Gv组根部总U含量均高于同一时期CK组;接种Gv组基质中总U含量小于CK组,其中接种Gv后蜈蚣草对铁锰氧化态和硫化物态U的吸收效果最好;基质中各形态U随培养时间的延长含量均呈下降趋势.接种Gv组比CK组富集系数大,且均大于1;菌根侵染率与富集系数呈显著正相关关系.以上结果说明接种Gv促进蜈蚣草对U的吸收,因此,蜈蚣草丛枝菌根真菌共生体对治理U污染土壤有良好的应用前景.     

沸石负载对叔丁基杯[4]芳烃乙酸对铀的吸附行为

以对叔丁基杯[4]芳烃与溴乙酸乙酯为主要反应底物合成了对叔丁基杯[4]芳烃乙酸,然后将其负载在沸石上,红外光谱显示合成物具有杯[4]芳烃乙酸的特征结构,扫描电镜分析表明对叔丁基杯[4]芳烃乙酸成功负载于沸石之上,且分布均匀,分散性良好.通过静态吸附实验,结果表明在pH值 4,对叔丁基杯[4]芳烃乙酸/沸石的负载比0.025/1,吸附剂用量0.5g,铀初始质量浓度10mg/L,吸附时间30min时,沸石在负载了对叔丁基杯[4]芳烃乙酸后,对溶液中铀的吸附率从30%左右提高到93%.沸石和负载沸石吸附动力学行为均符合准二级动力学模型,但负载沸石对铀的吸附速率明显高于沸石.沸石和负载沸石吸附等温式都符合Langmuir吸附等温线,说明都为单分子层吸附;由此推导出的最大吸附量Qm从16.8919提高到32.5733mg/g,这主要是因为沸石负载了对叔丁基杯[4]芳烃乙酸增加了吸附点位.吸附铀前后的红外光谱表明,负载沸石对铀的去除主要依靠对叔丁基杯[4]芳烃乙酸与铀的强络合作用和Si—O和Al—O的吸附作用,两种作用的协同加快了吸附速率,增加了吸附容量.     

Biotic Impoverishment and Homogenization in Unfragmented Forest Understory Communities

Abstract:  Ecological change is often hard to document because of a lack of reliable baseline data. Several recent then-versus-now surveys of temperate forest and grassland communities demonstrate losses of local plant species, but most are based on data from a single site. We resurveyed understory communities in 62 upland forest stands in northern Wisconsin (U.S.A.) for which quantitative baseline data exist from 50 years ago. These stands are within a largely unfragmented region but vary in species composition and successional stage. We collected data on changes in (1) total and native species richness, (2) the ratio of exotic to native species, (3) the relative abundance of habitat generalists, and (4) community similarity among sites. We also compared how these rates of change varied over time. Over the past 50 years, native species density declined an average of 18.5% at the 20-m² scale, whereas the ratio of exotic species to native species increased at 80% of all sites. Habitat generalists increased, and habitat specialists declined, accounting in part for an 8.7% rise in average similarity in species composition among sites. Most of these changes cannot be related to succession, habitat loss, or invasion by exotic species. Areas without deer hunting showed the greatest declines in native species density, with parks and research natural areas faring no better than unprotected stands. Animal-pollinated and animal-dispersed species also declined, particularly at unhunted sites. These results demonstrate the power of quantitative multistand data for assessing ecological change and identify overabundant deer as a key driver of community change. Because maintaining forest habitats alone fails to preserve plant diversity at local scales, local biotic simplification seems likely to continue in the region unless active efforts are taken to protect diversity.     

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.     

Application of artificial neural networks for classification of uranium distribution in the Central Rand goldfield,South Africa

Mine tailings generate significant environmental impacts and contribute to water pollution. The Central Rand goldfield, South Africa is replete with gold mine tailings which have contributed significantly to water pollution as a result of acid mine drainage (AMD). Water quality is affected by mine tailings and spillages, especially from active slimes dams, currently reprocessed tailings, as well as footprints left behind after reprocessing. The release and distribution of uranium from these sites was studied. Correlation matrices show a strong link between different variables as a result of AMD produced. Principal component analysis (PCA) was used to identify very influential variables which account for the pollution trends. Artificial neural networks (ANN) using the Kohonen algorithm were applied to visualise these trends and patterns in the distribution of uranium. High concentrations of this radionuclide were detected in streams in the vicinity of the tailings dumps, active slimes and reprocessing areas. The concentrations are reduced drastically in dams and wetlands as a result of precipitation and dilution effects.     

某铀尾矿库周围农田土壤重金属污染潜在生态风险评价

为能够定量评价铀尾矿库周围农田土壤重金属污染程度及其潜在生态危害性,采用Hakanson潜在生态风险指数法对土壤中重金属进行综合污染评价。结果表明,铀尾矿库周围部分农田土壤中重金属Cd、Ni、As、Cu、Hg、Zn含量存在积累和超标情况,尤以Cd的污染最严重,Ni、As次之;Pb、Cr含量能够满足标准限值要求。潜在生态风险评价结果显示,铀尾矿库周围农田土壤重金属潜在生态风险较高,主要潜在生态风险因子为Cd,其次是Hg、As,Cr、Pb、Ni、Cu、Zn并不构成潜在生态风险。铀尾矿库周围农田土壤中较高水平的Cd在构成环境污染的同时,也构成了较严重的生态危害,应加强对重金属Cd、Hg的生态风险防治。     

某铀矿九种优势草本植物铀的测定

研究探讨通过植物吸收来修复铀污染的可能性.首先采用"无样地取样法"对南方某铀矿植物群落进行调研,再用"5Br-PADAP显色目视比色法"研究并测定了从中筛选到的芒、狗尾草、鬼针草、野棉花、辣蓼、律草、商陆、凤尾蕨和鸭跖草九种优势草本植物铀含量的差异.结果表明,测得的样品土壤中铀含量在120 μg/g左右,而芒草、鸭跖草...     

中空纤维膜器处理含铀(VI)废水的研究

在中空纤维膜器中研究了二（2－乙基己基）磷酸（HDEHP＿煤油膜萃取含铀（Ⅵ）废水。实验表明，HDEHP－煤油膜萃取铀（Ⅵ）的萃取率随萃取时间的增加而增加；当水相pH大于2时，水相酸度对速率影响较小，当水相pH小于2时，随着水相pH的提高，速率明显上升；提高水相流速可提高膜萃取率；当有机相HDEHP浓度小于0.01mol/L时，随着HDEHP浓度的提高萃取率上升，当大于0.01mol/L后，其浓度改变对萃取率影响不大。温度和有机相流速对膜萃取率影响较小。