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通过室内水槽试验,探讨了单切口坝对稀性泥石流的拦砂性能,并与梳子坝的试验结果进行了比较分析。初步得到:(1)单切口坝有全闭塞、部分闭塞和不闭塞3种闭塞类型。当切口宽度b与稀性泥石流中最大颗粒粒径dmax之比b/dmax≤0.394时,切口全闭塞;b/dmax≥1.478时,切口不闭塞;0.394〈b/dmax〈1.478时,切口为部分闭塞。(2)单切口坝在降低过坝泥石流密度变化量上,与梳子坝有相似规律。对单切口坝而言,b/dmax在0.394~0.739之间,过坝泥石流密度变化量随b/dmax增大而增大,在b/dmax=0.739时,过坝泥石流密度变化量达到最大,其后随着b/dmax的进一步增大,过坝泥石流密度变化量逐渐减小;在0.493≤b/dmax≤0.986之间,单切口坝降低过坝泥石流密度变化量较显著。(3)在相同的试验条件下,以过坝泥石流平均密度及其降低率为防治泥石流的效益指标,显示梳子坝与单切口坝的坝后平均密度的比值大多小于1,表明在相同的试验条件下梳子坝对稀性泥石流的防治效果较好。 相似文献
316.
北京城市灾害及新世纪安全战略 总被引:4,自引:0,他引:4
在归纳分析北京城市灾害源的基础上 ,研究了北京城市综合减灾战略规划的指导思想、基本原则及技术路线。重点论述了城市科学减灾的研究模式及方法 相似文献
317.
In November 2005, an explosion occurred at a petrochemical plant of the Jilin Petrochemical Corporation in Jilin Province, China. A nearby water body was seriously polluted with a large spill of toxic substances made up of a mixture of benzene, aniline, and nitrobenzene (NB). To understand the long term impact of NB on public health and ecosystem around the Songhua River, it was necessary to investigate its fate in the environment. In this study, a microcosm was used to mimic the polluted water system and to study the transport and fate of NB in the river water body. The volatility and biodegradation of NB was investigated and a Markov model was applied to predict the fate of NB in the environment. The simulated results matched very well with the results obtained from the microcosm experiment. The model indicated that at room temperature and after around 500 h, there was only residual NB in the water and sediment. Most of the NB (around 82%) evaporated into the air and 18% was degraded by microorganisms. 相似文献
318.
Decolorization of cationic red X-GRL by wet air oxidation: performance optimization and degradation mechanism 总被引:1,自引:0,他引:1
The decolorization of a strong colored azo dye solution of cationic red X-GRL was investigated by wet air oxidation under relatively mild conditions (60-180 degrees C, PO2 = 0-1.2 MPa). Mono-factor experiments were carried out to investigate the effect of the operation factors and the relatively important parameters were selected for optimization using response surface methodology to explore the interactions of these relatively important parameters. Model regeneration analysis and the check experiments showed that the data of the general linear model agreed with the experiment results well. With multistage Monte-Carlo optimization, the best region of these variables could be predicted to dye color removal. At typical operational conditions, the intermediates of dye degradation were detected and confirmed by GC/MS system. Considering the intermediates and the structure analysis with the help of Gaussian 03W (version 6.0) and the theory of dye color, a possible degradation mechanism for the wet air oxidation of cationic red X-GRL was discussed and the probable degradation pathway was deduced. 相似文献
319.
Physiological and biochemical responses to high Mn concentrations in two contrasting Populus cathayana populations 总被引:1,自引:0,他引:1
We exposed the cuttings of Populus cathayana to Hoagland's solution containing four different manganese (Mn) concentrations (0, 0.1, 0.5 and 1mM) in a greenhouse to characterize the physiological and biochemical basis of Mn resistance in woody plants. Two contrasting populations of P. cathayana were used in our study, which were from the wet and dry climate regions in western China, respectively. The results showed that Mn treatments significantly decreased chlorophyll content and growth characteristics, including shoot height, basal diameter, biomass accumulation and total leaf area in the two populations. Mn treatments also significantly increased the levels of abscisic acid (ABA), polyamines and free amino acids especially proline (Pro), histidine (His) and phenylalanine (Phe) available for cellular signaling and heavy metal chelation. In addition, high Mn concentrations also caused oxidative stress indicated as the accumulation of hydrogen peroxide (H(2)O(2)) and malondialdehyde (MDA) contents. On the other hand, there were different responses to Mn stress between the two contrasting populations. Compared with the dry climate population, the wet climate population accumulated more Mn in plant tissues especially in leaves; it showed lower tolerance index and more pronounced decrease in growth and chlorophyll contents. The wet climate population not only accumulated less ABA, putrescine and free amino acids, but also exhibited lower activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX), thus suffering from more serious oxidative damage. Therefore, our results showed that the wet climate population was more susceptible to Mn stress than the dry climate population. 相似文献
320.
The distribution and dynamics of microcystins in various organs of the phytoplanktivorous bighead carp were studied monthly in Lake Taihu, which is dominated by toxic cyanobacteria. There was a good agreement between LC-MS and HPLC-UV determinations. Average recoveries of spiked fish samples were 63% for MC-RR and 71% for MC-LR. The highest MC contents in intestine, liver, kidney and spleen were 85.67, 2.83, 1.70 and 1.57 microg g-1 DW, respectively. MCs were much higher in mid-gut walls (1.22 microg g-1 DW) than in hind- and fore-gut walls (0.31 and 0.18 microg g-1 DW, respectively), suggesting the importance of mid-gut wall as major site for MC absorption. A cysteine conjugate of MC-LR was detected frequently in kidney. Among the muscle samples analyzed, 25% were above the provisional tolerable daily intake level by WHO. Bighead is strongly resistant to microcystins and can be used as biomanipulation fish to counteract cyanotoxin contamination in eutrophic waters. 相似文献