Influence of complex reagents on removal of chromium(VI) by zero-valent iron

The removal of Cr(VI) by zero-valent iron (Fe(0)) and the effect of three complex reagents, ethylenediaminetetraacetic acid (EDTA), NaF and 1,10-phenanthroline, on this reaction were investigated using batch reactors at pH values of 4, 5 and 6. The results indicate that the removal of Cr(VI) by Fe(0) is slow at pH 5.0 and that three complex reagents play different roles in the reaction. EDTA and NaF significantly enhance the reaction rate. The zero-order rate constants at pH 5.0 were 5.44 microM min(-1) in the presence of 4mM EDTA and 0.99 micrM min(-1) in the presence of 8 mM NaF, respectively, whereas that of control was only 0.33 micrM min(-1), even at pH=4.0. This enhancement is attributed to the formation of complex compounds between EDTA/NaF and reaction products, such as Cr(III) and Fe(III), which eliminate the precipitates of Cr(III), Fe(III) hydroxides and Cr(x)Fe(1-)(x)(OH)(3) and thus reduce surface passivation of Fe(0). In contrast, 1,10-phenanthroline, a complex reagent for Fe(II), dramatically decreases Cr(VI) reduction by Fe(0). At pH=4.0, the zero-order rate constant in the presence of 1mM of 1,10-phenanthroline was 0.02 micrM min(-1), decreasing by 99.7% and 93.9%, respectively, compared with the results in the presence and absence of EDTA. The results suggest that a pathway of the reduction of Cr(VI) to Cr(III) by Fe(0) may involve dissolution of Fe(0) to produce Fe(II), followed by reduction of Cr(VI) by Fe(II), rather than the direct reaction between Cr(VI) and Fe(0), in which Fe(0) transfers electrons to Cr(VI).     

风险严重度指数法在毒气泄漏评价中的应用

为评价某区域或某设备潜在的毒气泄漏事故场景的风险水平,以对不同的风险等级进行风险控制和安全规划,详细介绍了工业事故风险评估方法ARAMIS所采用的风险严重度指数法.首先基于事故频率和后果的风险矩阵选取毒气泄漏事故场景;然后运用毒气当量浓度计算任意暴露时间下不同风险严重度等级所对应的特征距离,并根据同一风险等级内风险严重度指数与距离的线性关系计算任意点的风险严重度指数;最后应用1个实例分析了考虑所研究区域的风向概率后对风险严重度指数的真实影响,便于工厂或企业识别不同的风险等级,进行不同场景下风险水平的对比性研究,为其安全设计及风险分析提供了一种新的评估方法.     

山地地形重气扩散模拟中湍流模型的选择

针对类似开县井喷的毒气扩散事故,研究山地地形条件下如何合理选择湍流模型对重气扩散进行大范围数值模拟.在初始条件和边界条件相同条件下,采用密切值法对6个BANS模型(RSM、标准k-ε、RNG k-ε、可实现k-ε、标准k-ω和SST k-ω)的计算结果进行多方案选择,同时参考模拟中所消耗的CPU时间,使选用的模型尽可能在"计算精度"和"计算时间"之间取得平衡.结果表明,对山地条件下的大范围毒气扩散事故的模拟,采用标准k-ε模型时可在"计算精度"和"计算时间"之间取得较好平衡.可见,对山地地形条件下大范围重气扩散的数值模拟宜采用标准k-ε模型.     

Anthropogenic metal cycles in China

The flows and stocks of seven important industrial metals were characterized for mainland China for several years in the dynamically changing decade of 1994–2004. One-year snapshot cycles are provided for chromium, nickel, and silver. For copper, zinc, lead, and iron, multiple-year cycles have been completed; they demonstrate that the flows of these metals into use in China doubled between 2000 and 2004. Although the Chinese per capita flows from production to disposal are mostly shown to be below the global average rate, they are increasing or are expected to increase dramatically. The metal resource efficiency is evaluated for several indicators of material flow analysis; these metrics for China are also below the global average values. The research quantitatively illustrates that China’s metal cycles may pose significant resource and environmental challenges in terms of their magnitudes and potential for growth.     

浅谈资源型城市可持续发展 ──以大庆为例阐述战略规划和环境政策制定的依据和原则

文章分析了资源型城市制定可持续发展战略和环境政策的依据和原则,以大庆开发建设多年来的成功经验和失败教训为例,阐释了资源型城市充分利用资源、资金、文化、人才的重要性和必要性,及对生态环境和人文环境充分保护的紧迫性。进而说明:充分利用好城市的各种资源,充分保护好城市的生态环境和人文环境,及早发展替代产业完成城市转型是资源型城市可持续发展的必由之路。     

基于GIS的城市火灾风险评价及其在防灾规划中的应用

随着经济发展和城市化进程的不断加快,城市火灾事故不断增多,造成的人员伤亡和财产损失也越来越严重。本文通过构建城市火灾风险评价指标体系,利用GIS中的空间分析功能对各指标体系按其权重进行叠加,得出城市的现状火灾风险等级区划图。根据风险评价现状确定防灾减灾规划的目标,采取相应的防灾减灾措施,并对规划后的火灾风险状况进行了预测,得出规划后的火灾风险等级,从而为消防和规划部门减少和预防城市火灾提供依据和参考。     

湖北农村民居现状调查与震害预测

通过对湖北农村民居建筑结构、抗震设防以及居民抗震意识的调查,分析了湖北农村民居的结构特点和建造现状,得到了湖北农村民居在结构形式、建筑材料、建造年代、场地条件及连接构造等方面的统计数据。在此基础上,采用震害预测方法对湖北农村民居在不同地震烈度时的震害进行了预测,给出了各结构类型的震害预测结果,为湖北省农村地震灾害的综合防御提供了科学依据。     

地震引发城市燃气管线事故的定量风险评价

为了对地震作为诱发事件导致燃气管线的风险进行量化,提出了地震引发城市燃气管线事故的定量风险评价程序,基于离散化的地震PGA值和地震预期重现时间给出可能的损坏概率和参考事故场景,并进行事故场景的后果评价,最终实现燃气管线个人风险和社会风险的表征.此外,基于Matlab编写了适用于该风险评价程序的GUI程序,结合淮南市城市次高压燃气管线的具体实例,实现了风险表征并研究了地震参数变化对风险变化的影响.     

基于PDCA持续改善架构的企业业务持续管理研究

以研究业务持续管理相关的国际法规条款与PDCA持续改善架构,给出业务持续管理关键要素定义以其在PDCA架构中所担任的角色与位阶,进而制定企业业务持续管理的PDCA封闭式管理模型,并阐述企业典型业务持续管理各个要素的实行重点,为企业的业务风险管理提供可用的方法与可执行的建议。     

闪火灾害的后果分析

闪火是可燃性气体或蒸气泄漏到空气中并与之混合被点燃而发生的一种非爆炸性的蒸气云燃烧,其主要危害是热辐射和火焰直接灼烧。闪火的热辐射计算包括闪火动力特性及热通量计算。热辐射的大小由火焰的辐射能,视角系数和大气传输率所决定。运用Pietersen(1990)热辐射的伤害－破坏理论,分析计算了一起闪火灾害热辐射造成人的伤害后果和对建筑物的破坏后果。