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11.
Damage caused by the 2005 Buncefield explosion indicates pressures in excess of 2000 mbar over all of the area covered by the vapour cloud. Such high overpressures are normally associated with high (super-sonic) rates of flame spread. On the other hand, evidence from witnesses, building damage analysis and CCTV cameras all suggest the average rate of progress of the explosion flame front was only around 150 m/s.The high overpressures in the cloud and low average rate of flame advance can be reconciled if the rate of flame advance was episodic, with periods of very rapid combustion being punctuated by pauses when the flame advanced very slowly. The widespread high overpressures were caused by the rapid phases of combustion; the low average speed of advance was caused by the pauses.Mechanisms of flame spread through radiative ignition of particulates ahead of the flame front provide possible explanations for such unusual episodic behaviour.The first part of this paper reviews a wide range of empirical evidence on average flame speed and rate of blast pressure increase.The second part explores the theoretical consequences of forward radiation and how the new theory might be developed into a practical means of assessment. 相似文献
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Atmospheric concentrations of nitric acid (HNO3), sulfur dioxide (SO2), particulate nitrate and particulate sulfate on the urban- and mountain-facing sides of Mt. Gokurakuji were measured from November 2002 to October 2003, in order to evaluate
the effects of anthropogenic activity on air quality and dry deposited nitrate and sulfate on the surfaces of pine foliage.
The results showed that HNO3, SO2 and concentrations were significantly higher (P < 0.05) on the urban-facing side (1.54, 2.48 and 0.65 μg m−3, respectively) than the mountain-facing side (0.67, 1.19 and 0.37 μg m−3, respectively), while concentrations did not differ significantly between the two sides (urban-facing: 2.80 μg m−3; mountain−facing: 2.05 μg m−3). Indirect estimates of dry deposition rates of nitrate and sulfate to the surfaces of pine foliage based on the measured
concentrations approximately agreed with the measured values determined by the foliar rinsing technique in a previous study.
It was found that HNO3 was the major source (approximately 80%) of dry deposited nitrate on pine foliage, while the contribution from was about equal to that from SO2. In conclusion, HNO3 and SO2 appear to be dominant species reflecting higher dry deposition rates of nitrate and sulfate on the urban-facing side compared
to the mountain-facing side of Mt. Gokurakuji. 相似文献
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Nelson J. ODriscoll Emma Vost Erin Mann Sara Klapstein Robert Tordon Matthew Lukeman 《环境科学学报(英文版)》2018,30(6):151-159
Mercury is a globally distributed, environmental contaminant. Quantifying the retention and loss of mercury is integral for predicting mercury-sensitive ecosystems. There is little information on how dissolved organic carbon(DOC) concentrations and particulates affect mercury photoreaction kinetics in freshwater lakes. To address this knowledge gap,samples were collected from ten lakes in Kejimkujik National Park, Nova Scotia(DOC: 2.6–15.4 mg/L). Filtered(0.2 μm) and unfiltered samples were analysed for gross photoreduction, gross photooxidation, and net reduction rates of mercury using pseudo first-order curves. Unfiltered samples had higher concentrations(p = 0.04) of photoreducible divalent mercury(Hg(II)RED)(mean of 754 ± 253 pg/L) than filtered samples(mean of 482 ± 206 pg/L);however, gross photoreduction and photooxidation rate constants were not significantly different in filtered or unfiltered samples in early summer. DOC was not significantly related to gross photoreduction rate constants in filtered(R~2= 0.43; p = 0.08) and unfiltered(R~2= 0.02; p = 0.71) samples; DOC was also not significantly related to gross photooxidation rate constants in filtered or unfiltered samples. However, DOC was significantly negatively related with Hg(Ⅱ)_(RED) in unfiltered(R2= 0.53; p = 0.04), but not in filtered samples(R~2= 0.04;p = 0.60). These trends indicate that DOC is a factor in determining dissolved mercury photoreduction rates and particles partially control available Hg(Ⅱ)_(RED) in lake water. This research also demonstrates that within these lakes gross photoreduction and photooxidation processes are close to being in balance. Changes to catchment inputs of particulate matter and DOC may alter mercury retention in these lakes and could partially explain observed increases of mercury accumulation in biota. 相似文献
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柴油车尾气的致突变作用 总被引:1,自引:0,他引:1
用大鼠肝细胞悬液程序外DNA合成试验(UDS),来检测5种柴油机颗粒物的致突变活性,结果显示国产及进口的轻、中、重型柴油机,其排出颗粒提取物均能引起大鼠肝细胞UDS试验的CPM值升高,且有一定的剂量-反应关系,说明柴油机排出的颗粒提取物存在细胞遗传毒性;各牌号比较发现其颗粒物致突变性的轻型车大于中、重型车,国产车大于同类进口车的趋势。 相似文献
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Receptor modeling for source apportionment of polycyclic aromatic hydrocarbons in urban atmosphere 总被引:1,自引:0,他引:1
Singh KP Malik A Kumar R Saxena P Sinha S 《Environmental monitoring and assessment》2008,136(1-3):183-196
This study reports source apportionment of polycyclic aromatic hydrocarbons (PAHs) in particulate depositions on vegetation
foliages near highway in the urban environment of Lucknow city (India) using the principal components analysis/absolute principal
components scores (PCA/APCS) receptor modeling approach. The multivariate method enables identification of major PAHs sources
along with their quantitative contributions with respect to individual PAH. The PCA identified three major sources of PAHs
viz. combustion, vehicular emissions, and diesel based activities. The PCA/APCS receptor modeling approach revealed that the
combustion sources (natural gas, wood, coal/coke, biomass) contributed 19–97% of various PAHs, vehicular emissions 0–70%,
diesel based sources 0–81% and other miscellaneous sources 0–20% of different PAHs. The contributions of major pyrolytic and
petrogenic sources to the total PAHs were 56 and 42%, respectively. Further, the combustion related sources contribute major
fraction of the carcinogenic PAHs in the study area. High correlation coefficient (R
2 > 0.75 for most PAHs) between the measured and predicted concentrations of PAHs suggests for the applicability of the PCA/APCS
receptor modeling approach for estimation of source contribution to the PAHs in particulates. 相似文献