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971.
972.
作为核燃料循环过程中一种兼具辐射危害和化学毒性的中间产物,UF6的泄漏事故,特别是事故的环境评价技术越来越受到人们的重视.SAFUIT/UF6是专门针对此类事故的环境评价模型,目前已经开展了初步的验证工作.根据1987年法国UF6释放实验条件,对SAFUIT/UF6模型计算结果进行了误差分析,并与HG-SYSTEM/UF6模型进行了对比.初步认为SAFUIT/UF6模型可准确地模拟UF6扩散.此外,SAFUIT/UF6模型在某设施核事故应急评价系统中也得到了应用. 相似文献
973.
基于全隧道方案的渤海海峡跨海通道工程环境影响研究 总被引:1,自引:0,他引:1
渤海海峡跨海通道是疏通中国干线交通网战略布局中的咽喉工程,因工程规模浩大,其环境影响广泛而深远.简要回顾了工程建设方案的筛选进程及“深埋式全隧道”方案的环境优势;建议工程环境影响评价采用“协作型”环境影响评价模式,以合作和协调克服各方之间的分歧和矛盾;初步探讨了工程前期调研的主要内容;识别分析了通道工程对近岸海域、出入口城市的主要环境影响.结果表明:与其他方案相比,深埋式全隧道方案对自然人文景观、海洋生态环境、海洋资源开发利用等的影响是最小的,并提出了消除或减缓不良环境影响的对策措施,为通道工程的立项决策提供科学依据. 相似文献
974.
975.
Carbon source is a critical constraint on nutrient removal in domestic wastewater treatment. However, the functions of particulate organic matter (POM) and some organics with high molecular weight (HMW) are overlooked in the conventional process, as they cannot be directly assimilated into cells during microbial metabolism. This further aggravates the problem of carbon source shortage and thus affects the effluent quality. Therefore, to better characterize organic matter (OM) based MW distribution, microfiltration/ultrafiltration/nanofiltration (MF/UF/NF) membranes were used in parallel to fractionate OM, which obtained seven fractions. Hydrolysis acidification (HA) was adopted to manipulate the MW distribution of dissolved organic matter (DOM) and further explore the correlation between molecular size and biodegradability. Results showed that HA pretreatment of wastewater not only promoted transformation from POM to DOM, but also boosted biodegradability. After 8 hr of HA, the concentration of dissolved organic carbon (DOC) increased by 65%, from the initial value of 20.25 to 33.48 mg/L, and the biodegradability index (BOD5 (biochemical oxygen demand)/SCOD (soluble chemical oxygen demand)) increased from 0.52 to 0.74. Using MW distribution analysis and composition optimization, a new understanding on the characteristics of organics in wastewater was obtained, which is of importance to solving low C/N wastewater treatment in engineering practice. 相似文献
976.
Thiolated arsenicals in arsenic metabolism: Occurrence, formation, and biological implications 总被引:1,自引:0,他引:1
Arsenic (As) is a notoriously toxic pollutant of health concern worldwide with potential risk of cancer induction, but meanwhile it is used as medicines for the treatment of different conditions including hematological cancers. Arsenic can undergo extensive metabolism in biological systems, and both toxicological and therapeutic effects of arsenic compounds are closely related to their metabolism. Recent studies have identified methylated thioarsenicals as a new class of arsenic metabolites in biological systems after exposure of inorganic and organic arsenicals, including arsenite, dimethylarsinic acid (DMAV), dimethylarsinous glutathione (DMAIIIGS), and arsenosugars. The increasing detection of thiolated arsenicals, including monomethylmonothioarsonic acid (MMMTAV), dimethylmonothioarsinic acid (DMMTAV) and its glutathione conjugate (DMMTAVGS), and dimethyldithioarsinic acid (DMDTAV) suggests that thioarsenicals may be important metabolites and play important roles in arsenic toxicity and therapeutic effects. Here we summarized the reported occurrence of thioarsenicals in biological systems, the possible formation pathways of thioarsenicals, and their toxicity, and discussed the biological implications of thioarsenicals on arsenic metabolism, toxicity, and therapeutic effects. 相似文献
977.
In this study, cucurbit[8]uril (CB[8]) was utilized as a kind of new adsorbent to remove Pb2 + ions from aqueous solution. With the solution pH increased from 2 to 6, the removal efficiency of adsorption increased from 55.6% to 74.5%correspondingly. The uptake of Pb2 + increased rapidly in the initial 30 min, and then the adsorption rate became slower. The Pseudo-second order model could be used to interpret the adsorption kinetics satisfactorily; and the rate determining step in Pb2 + adsorption onto CB[8] was the external mass transfer step. Equilibrium isotherm study reveals that the Langmuir model gave a better fitting result than Freundlich model. The maximum adsorption capacity calculated by the Langmuir model was 152.67 mg/g for 298 K, 149.70 mg/g for 313 K and 136.42 mg/g for 323 K, respectively. The adsorption is a spontaneous process of exothermic nature. The effect of the adsorbent dosage and the influences of solution pH and co-existing cations were also investigated. The CB[8] was synthesized and characterized by 1H NMR, IR, ESI-MS spectra, SEM-EDAX, Zeta-potential and BET-analysis. The adsorption mechanism was due to the coordination between CB[8] molecule and Pb2 + ions. 相似文献
978.
在一些环境污染型工程项目中,做好农村移民的安置规划工作尤为重要。借助世行贷款项目,通过持续的实际调研,以梅城垃圾填埋场为例,介绍了项目的建设主要内容及影响。从征地补偿安置、农村住宅房屋拆迁安置及弱势群体及妇女权益保护三个方面论述了农村移民生产生活安置方式。基于此,总结出了以下四个结论:(1)严格遵守相关法律法规、(2)征迁过程与安置工作相协调、(3)合理补偿,适当调整、(4)强化机构建设和人员能力培养。并提出了四条合理化建议。 相似文献
979.
980.