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Formation pathways of polychlorinated dibenzofurans (PCDFs) in sediments contaminated with PCBs during the thermal desorption process 总被引:1,自引:0,他引:1
Thermal desorption has attracted considerable interest as a remediation technology for the removal of dioxins and polychlorinated biphenyls (PCBs) from contaminated soils and sediments. Although several research groups have confirmed that polychlorinated dibenzofurans (PCDFs) are formed from PCBs during the thermal desorption of sediments contaminated with PCB, the formation pathways remain poorly understood. Herein, thermal desorption has been used to develop a greater understanding of the formation pathways of PCDFs from sediments contaminated with PCBs. PCB decomposition experiments of sediments contaminated with PCBs were performed over 5 min at 450 °C with a gas composition of 10% O(2)/90% N(2), either in the absence (Run 1) or presence (Run 2-4) of one of three different (13)C(12)-labeled PCB individual standards. The results of Run 1 showed that 99.96% of PCBs and 98.40% of polychlorinated dibenzo-p-dioxins (PCDDs) in the treated sediments had decomposed, whereas the concentration levels of PCDFs had increased by a factor of 31. The addition of different (13)C(12)-labeled PCBs to the sediment sample yielded different (13)C(12)-PCDFs isomer patterns, with formation pathways including loss of ortho-Cl(2), loss of HCl involving a 2,3-chlorine shift, loss of ortho-H(2) and dechlorination. 相似文献
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Ayako Hirose Akihiko Nagasaka 《International journal of occupational safety and ergonomics》2013,19(4):479-490
The aim of this study was to examine how to take an effective rest to prevent a decline in alertness at work. The relationship between alertness during the rest period and subsequent task performance were investigated. The electroencephalogram (EEG) during the rest period was classified into 3 types, and these types had a significant effect on performance after the rest period. Type 1 (increasing in theta, alpha 2, and beta 1 power) was the best one for carrying out the task, whereas performance gradually declined in Type 3 (no change in EEG activity). In the case of Type 1, the method that would relieve sleep inertia had a more positive impact on performance after the rest period. 相似文献
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Supaporn Phanwilai Naluporn Kangwannarakul Pongsak 《Frontiers of Environmental Science & Engineering》2020,14(6):115
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Haruna Amano Toshiaki Fujita Naoshi Hiramatsu Sayumi Sawaguchi Takahiro Matsubara Craig V. Sullivan Akihiko Hara 《Marine Biology》2007,150(6):1215-1225
Coralliophila abbreviata (Lamarck) is a corallivorous gastropod that lives and feeds on several species of scleractinian coral in the Western Atlantic
and Caribbean. Previous studies of C. abbreviata have revealed that snails on branching acroporid corals are larger and consume more tissue than those on massive and plating
corals. To ascertain whether snail life-history and fitness are differentially affected by the coral host, an analysis of
the age structure and female reproductive output of snail populations on three coral host taxa (Acropora palmata, Diploria spp., and Montastraea spp.) was conducted at four shallow (2–7 m depth) reef sites off Key Largo, Florida in June through August, 2004. Snails
were, on average, almost twice as large on A. palmata than on Diploria spp. and Montastraea spp., averaging 30.3 mm shell length, compared to 17.2 and 17.6 mm, respectively. Brood size increased as a power function
with female shell length. Females on A. palmata were significantly larger than females on the other two hosts and, therefore, produced more offspring per female. The number
of growth striae on the inner surface of the operculum was used to estimate snail age. Estimates of growth rate were obtained
by fitting the Gompertz growth function to size-at-age plots and mortality was estimated using growth parameters and size-frequency
data. The data suggest that C. abbreviata inhabiting A. palmata are larger than on alternative hosts due to a combination of a faster growth rate and longer life-span. The species is believed
to be a protandrous hermaphrodite. The timing of sex change varied among hosts; snails on A. palmata changed sex later at larger sizes relative to those on the other two hosts. Based on these results, it seems probable that
C. abbreviata has developed reaction norms for life-history traits, allowing snails to adjust and maximize fitness in the different environments
associated with various coral hosts. 相似文献
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We carried out a field study of the plume discharged by a near-shore wastewater outfall near the Akashi Strait, Japan. Using
an Acoustic Doppler Current Profiler and a tow-body CTD, we measured the near-surface salinity and temperature fields in the
region throughout an M2 tidal cycle. We filtered the data in T–S space to remove water masses other than the wastewater, and then used the adiabatic
mixing assumption to calculate the concentration of wastewater in the far field of this plume. Averaging the T–S fields of
repeated surveys over a time period during which the tidal regime did not change substantially, allowed comparison of the
time-averaged plume with the analytical solution for a plume diffusing in both the horizontal and vertical dimensions. The
resulting vertical turbulent diffusion coefficients agreed well with those resulting from Thorpe scales determined via a vertically-profiling
CTD, as well as with the canonical value for open channel flow of D
z
= 0.067hu
*. The corresponding horizontal turbulent diffusion coefficients, however, were two orders of magnitude larger than those typically
observed in straight channels, and an order of magnitude larger than those observed in meandering rivers. This is likely a
result of enhanced horizontal mixing due to barotropic eddies generated by the interaction of strong tidal flow with headlands
and levees, as well as due to the time-varying nature of tidal flow, and baroclinic spreading of the buoyant wastewater plume. 相似文献
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We carried out a field study of a small river plume emptying into Osaka Bay near the Akashi Strait in western Japan, to understand
the fate of its urban-runoff-laden waters. As the river is weak compared to tidal currents, we find that the behavior of the
plume is strongly influenced by phasing between tidal stage and currents (a westward-traveling progressive tidal wave). When
the tidal stage rises, sea water floods up the river, and concentrated river effluent cannot be seen in Osaka Bay. During
most of the river’s ebb, a topographic eddy transports river effluent towards the energetic Akashi Strait, while strong vertical
shear in the tidal flow mixes the effluent with seawater. However, there is a short interval of time during which the direction
of tidal flow in the Strait changes direction and the magnitude of the current is weak. At this time, shear is weak enough
to allow a stratified plume of concentrated river water to form, and this plume is driven offshore, and into Osaka Bay, by
baroclinic circulation. A sewage outfall, which is located very close to the river mouth, is subjected to these same conditions
and therefore exhibits similar behavior. Understanding the relation between tidal phase and plume behavior will be useful
to Kobe City, as well as other cities in a similar environment, for minimizing the environmental effects of their wastewater
and non-point-source runoff. 相似文献