环境气溶胶中90Sr分析测量的不确定度评定

⁹⁰Sr是高毒性的纯β放射性核素,其物理半衰期和生物半衰期长,环境气溶胶中的⁹⁰Sr通过吸入途径进入人体,对人类的危害主要为长时间积集在人体骨骼中并很难排出。在多堆型核设施运行场址中环境气溶胶的测定是辐射环境监测的重要内容,也是评价核设施运行对环境影响的重要指标。为了科学评价环境气溶胶中测量结果的准确性和可靠性,进行了气溶胶中⁹⁰Sr分析测量不确定度评定的方法研究,通过计算模型识别不确定度的来源,并对各分量进行量化分析,计算合成标准不确定度;结合典型样品分析实例,对环境气溶胶中⁹⁰Sr分析测量的不确定度进行了评定,气溶胶中的分析测量采用的是色层萃取的方法,利用草酸钇沉淀制成样品源,测量样品中β计数率。不确定度评定结果表明:环境气溶胶中⁹⁰Sr分析测量不确定度的来源主要有样品净计数率,探测效率,化学回收率,样品取样体积,测量期间半衰期修正;典型实例分析结果显示环境气溶胶中的相对标准不确定度可控制在15%内。文章中不确定度评定方法为气溶胶⁹⁰Sr分析测量结果的不确定度评定提供参考。     

Social capital and food security in post-conflict rural Lira District,northern Uganda

While a strong relationship has been established between social capital and food security in the research literature, it is uncertain whether this holds in post-conflict situations. This study examines associations between social capital and food security in post-conflict Lira District, northern Uganda. Since factors affecting food security are complex, we explored the roles of households' characteristics in food security outcomes. Data were collected from March to July 2011 through face-to-face interviews with 221 heads of household in rural Lira. Using multinomial logistic regression, a strong positive association was identified between social capital and household food security. The study also found significant associations of food security with sex, education of household head, amount of cultivated land, and farm and home possessions. The results of this analysis can aid the design of food security programmes that empower poor people while targeting the most vulnerable groups, thereby promoting sustainable development in post-conflict communities.     

长江河口区水体的锶同位素地球化学--对水与沉积物相互作用过程的反映

为了解长江河口区的水体混合过程和水与沉积物或颗粒物的相互作用过程,对长江河口水的87Sr/86Sr及Sr元素浓度进行了测定,结果显示:与世界河流平均值(Sr为78μg/L,87Sr/86Sr为0.7119)相比,长江水具有明显的高Sr(130μg/L)低87Sr/86Sr比值(0.7105)的特点。在长江口水体混合过程中,锶同位素没有象其它河口那样显示简单的两端员理想混合模式,而是在距河口约30～40km的地点出现87Sr/86Sr的突然升高,水体悬浮颗粒物(SPM)浓度也在同一区域出现升高现象。这可能是该区水体和沉积物相互作用比较强烈而引起沉积物与上覆水体发生物质交换。     

固定化啤酒酵母菌对锶的吸附机制及热力学研究

以聚乙烯醇和海藻酸钠作为载体,制备了固定化啤酒酵母菌颗粒。研究了固定化啤酒酵母菌对锶的吸附机制和吸附热力学。结果表明:(1)吸附Sr2+后的固定化啤酒酵母菌的内部结构更松散,更有利于固定化啤酒酵母菌对Sr2+的吸附。(2)固定化啤酒酵母菌吸附Sr2+后,部分-OH参与了吸附,使形成的氢键部分断开,振动峰发生蓝移。另外,由于-NH2和-CO-NH-中的N原子可提供孤对电子与有空轨道的Sr2+配位,从而改变了基团的极性。(3)当Sr2+初始质量浓度为10～200mg/L时,固定化啤酒酵母菌对Sr2+的吸附同时符合Freundlich和Langmuir吸附模型,但符合Langmuir吸附模型的程度更优,这说明固定化啤酒酵母菌与Sr2+之间主要通过分子间引力产生吸附,是以单分子层吸附为主的物理吸附。