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661.
662.
Shen S.Yang C.Cheng S. 《应用与环境生物学报》2015,(1):80-87
Microbes play an important role in material circulation and pollutant release in urban sediments, and its community structure can provide an important basis for evaluating the pollution load and ecosystem health of an urban river. In this study, bacterial communities in sediments from different locations of Tangxi River in Anhui Province were analyzed and compared, with an objective of evaluating the effects of aquatic environment on spatial characteristics of bacterial communities and the feasibility of using bacterial community composition as an indicator of urban river health. PCR-DGGE was applied to analyze the bacterial communities; fifteen major bands of 16S rDNA genes fragments from DGGE profiles of sediment samples were further eluted from gel, reamplified and sequenced. The sequences of these fragments were compared with the database in GenBank (NCBI). The collected samples were clustered based on UPGM Aanalysis. In addition, relationships between bacterial communities and environmental factors were analyzed by Monte Carlo test and redundancy analysis (RDA). The DGGE profiles indicated that upstream surface sediments had about 30 bands, but the differences in brightness were not significant. Although midstream surface sediments had only 18 bands on average, the brightness of some bands was relatively high, indicating that some dominant species of bacteria existed in these sediments. The amounts of bands in downstream sediments were between those of upstream and midstream, with some bands of high brightness. The NCBI comparison results showed that ten sequences shared 98-100% homology with known sequences, one with 97%, and the other four with uncultured bacteria. Shannon index (H) of bacterial diversity from upstream surface sediments was 3.31 on average, which was significantly (P < 0.05) higher than that of midstream surface sediments, and slightly higher than that of downstream surface sediments. UPGMA results showed both the distribution of bacteria communities and the diversity were strongly related with the sampling locations (Eigenvalue = 0.188, P = 0.134). Monte Carlo test and RDA analysis showed that the ion exchangeable form of nitrogen (IEF-N) was the main factor influencing the spatial characteristics of bacterial communities in the sediments. The aquatic plants had a significant effect on the richness of bacterial communities in the sediments, and the effectiveness of plant species was more notable than that of the vegetation coverage. The above results indicated that bacterial community structure and diversity in the surface sediments can well reflect the degree of urbanization development and effectiveness of ecological restoration in Tangxi River region. 相似文献
663.
A devastating crude oil vapor explosion accident, which killed 62 people and injured 136, occurred on November 22, 2013. It was one of the most disastrous vapor cloud explosion accidents that happened in Qingdao's storm drains in China. It was noted that blast overpressure and flying debris were the main causes of human deaths, personal injuries and structure damages. Two months after the accident, it was reported that there were three contentious issues in the investigation report. First issue was the discrepancy between the temperature of the crude oil vapor explosive limits which were measured by the investigation panel and the temperature reported by the local fire department. Second issue was the contradiction between the upper explosive limit and vapor pressure of the crude oil vapor. The last issue was the location of the ignition source which led to the explosion.In the present study some specific features of this accident and various causes led to the explosion, high casualties and severe damages were analyzed. Three contentious issues in the official investigation report were investigated and tested in detail. The first element tested was the explosive limits and limiting oxygen concentration of the crude oil vapor at different temperatures. Based on theoretical analysis and field investigations, the last two elements in the report were analyzed from multiple perspectives. Based on the TNO Multi-Energy model and PROBIT equations, damage probability of affected people at the leaking site was also estimated. The investigation concluded with a result that precautions need to be taken to prevent flammable gas explosions in the drainage systems. Key steps were explicitly discussed for improving the hazard identification and risk assessment of similar accidents in the future. 相似文献
664.
Lucie Flache Sezin Czarnecki Rolf-Alexander Dring Uwe Kierdorf Jorge A. Encarnao 《环境科学学报(英文版)》2015,27(5):184-193
Metal-contaminated soils and sediments are widespread in urbanized areas due to atmospheric deposition close to emission sources. These metals are bio-available for organisms, e.g., insects, and accumulate in food chains of insectivorous mammals. Especially bats, which live in urban regions and ingest large amounts of food relative to their body mass, are at risk of being poisoned due to the accumulation of trace metals. To determine species-specific trace metal contents in bats from urban environments, hair samples were analyzed by ICP-OES. Observed trace metal concentrations were related to species-specific foraging habitat, prey spectrum and degree of synanthropy. The species studied were Pipistrellus pipistrellus, Myotis daubentonii and Nyctalus noctula. P. pipistrellus showed the highest concentrations of lead and zinc and slightly higher concentrations of cadmium than the other two species, which was related to its high degree of synanthropy with foraging habitat mostly located in cities. In contrast, N. noctula displayed the highest contents of manganese and copper. The reason might be found in its prey spectrum, as N. noctula feeds mainly on beetles that are caught in cultured areas. Trace metal concentrations determined in hair samples of M. daubentonii ranged between the values of P. pipistrellus and N. noctula, probably reflecting an intermediate level of synanthropy. Positive correlations were observed between the concentrations of cadmium and lead and those of manganese and copper. Hair samples from bats are suitable monitoring tools to study trace metal exposure and can be used to determine differences in trace metal levels between species. 相似文献
665.
This paper presents a game theory methodology for risk management of urban natural gas pipelines, which is a collaborative participation mechanism of the stakeholders, including government, pipeline companies, and the public. Firstly, the involvement proportion of stakeholders in risk management under rational conditions is estimated by the static game theory. Subsequently, the system dynamics (SD) simulation is used to establish an evolution game model of stakeholders in risk management under the irrational conditions, in which the stability of the evolution game process is analyzed. The stakeholders’ involvement proportions from the static game model are utilized as the inputs for the evolution game model to simulate the dynamic evolution behavior of risk management strategies with different involvement proportions of stakeholders. Eventually, the dynamic evaluation game can extract an optimal strategy for risk management of urban natural gas pipelines. A case study is used to illustrate the methodology. In essence, this methodology can be extended for implementing risk management of urban infrastructure. 相似文献
666.
巢湖表层沉积物中磷赋存形态的时空变化 总被引:13,自引:4,他引:9
以巢湖表层沉积物为对象,采用欧洲标准测试委员会框架下发展的SMT分离方法分析总磷(total phosphorus,TP)、有机磷(organic phosphorus,OP)、无机磷(inorganic phosphorus,IP)、铁铝磷(NaOH-P)、钙磷(HCl-P)等磷形态的含量,利用ArcGIS 9.2和地统计学软件GS+5.3进行空间数据和插值处理,探讨了巢湖表层沉积物中磷的形态分布特征及来源.结果表明:①沉积物中TN、TP和有机质含量的季节变化较小,在空间上均表现出西半湖含量高于东半湖的分布特点;C/N比率在21.35~28.19之间(平均值为24.94),表明巢湖的入湖污染物主要以面源污染为主.②巢湖表层沉积物中TP含量的变化范围为528.90~1 385.71 mg.kg-1,IP为主要赋存形态(占TP的质量分数为55.78%~79.86%).③巢湖表层沉积物中,OP含量为169.05~841.24 mg.kg-1,东、西半湖OP含量分别为376.02 mg.kg-1和406.53 mg.kg-1(占TP的质量分数为47.49%和36.28%);NaOH-P含量为33.77~411.37 mg.kg-1,东、西半湖含量分别为108.37 mg.kg-1和276.30 mg.kg-1(占IP的质量分数为21.73%和33.12%);HCl-P含量为194.95~477.45 mg.kg-1,东、西半湖HCl-P含量分别为321.71 mg.kg-1和338.08mg.kg-1(占IP的质量分数为64.50%和40.53%),是IP的主要组成部分.④冬春季节OP含量高于夏秋季节,而夏秋季节HCl-P和NaOH-P含量高于冬春季节. 相似文献
667.
668.
669.
AHP法是规划决策管理的有效工具,本文通过在城市生态系统质量评价中AHP法的应用着重阐述了城市生态系统的层次结构分析和在多级递阶结构的基础上,经过判断矩阵的建立和运算,为城市生态系统质量评价中权重确定的科学化提供了定量的依据。 相似文献
670.