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961.
Martin Braniš 《Water, Air, & Soil Pollution: Focus》2008,8(1):49-60
To assess the effect of changes in traffic density and fuels used for heating at the beginning of the 1990s, 1992–2005 monthly
averages of PM10, SO2, NO2, NO, CO and O3 from Prague, the Czech capital, were analyzed together with long term trends in emissions of major pollutants, fuel consumption
and number of vehicles registered in Prague. The data from all monitoring stations were retrieved from the database of the
state automated monitoring system. Correlation coefficients between ambient monthly averaged temperature and all pollutants
of concern showed distinct seasonal trends. The results showed that while SO2 and to some extent also CO concentrations dropped namely in the first half of the analyzed period (1992–1997) as a result
decreased fossil fuel consumption for local heating, the behaviour of other pollutant concentrations followed a different
pattern. PM10 concentrations decreased during the beginning of the 1990s but showed a sign of increase after 2000. Concentrations of ozone
and NO2 did not reveal any significant change throughout the whole studied period. It can be concluded that during the studied period
traditional urban sources of pollution, such as coal and oil combustion, lost their importance but were simultaneously substituted
by pollutants from automotive transport (namely PM and NO2) making the problem of air quality even worse. 相似文献
962.
963.
Reiner Schroll Sabine Grundmann Ulrike Dörfler Bernhard Ruth Jean Charles Munch 《Water, Air, & Soil Pollution: Focus》2008,8(2):209-216
Several lysimeter scenarios and approaches exist to study the fate of agro-chemicals or contaminants from deposition in soil
columns. In many systems just transport and leaching of the parent compound is followed, in some systems the leaching and
transport of the metabolites is investigated as well. In more sophisticated lysimeter systems the volatilization and also
the mineralization of the applied chemicals can be additionally monitored. Depending on the lysimeter system used and on the
fact whether the applied chemicals are 14C-labeled or not, different results and various interpretations of the results might be achieved. Different lysimeter systems
are described in this paper and a real dataset of a specific lysimeter experiment was transferred and evaluated in a virtual
approach in the different lysimeter systems in order to show the advantages and disadvantages of the various systems. 相似文献
964.
Hang Seok Choi Seock Joon Kim Kwan Tae Kim 《Journal of Material Cycles and Waste Management》2008,10(1):1-6
The mixing characteristics of a passive scalar in the turbulent flow of a selective catalytic reduction process were numerically
and experimentally investigated, focusing especially on an injection nozzle with multiple holes for the reducing agent. The
multihole injection nozzle studied has six holes that are perpendicular to the ambient flue gas flow and are located near
the tip of the nozzle. Large eddy simulation was applied to the turbulent flow and mixing fields to elucidate the mixing mechanism
of the proposed nozzle compared with the single-hole nozzle that is commonly used in the conventional selective catalytic
reduction process. From the results, there exist broader regions of higher turbulent intensities for the multihole nozzle
than for the conventional single-hole nozzle. These regions are well matched with the positions of high vorticity in the near
upstream region of the jet flow issuing from the multiple holes of the nozzle. Consequently, the high turbulent intensities
and vorticity magnitudes lead to intensified mixing between the flue gas and the reducing agent. Hence, the most suitable
molar ratio between NOx and the reducing agent for the catalytic reaction can be easily obtained within a shorter physical
mixing length as a result of the enhanced scalar mixing. Finally, the numerical results were applied to a trial design version
of a multihole nozzle, and this nozzle was experimentally tested to confirm its mixing performance. 相似文献
965.
Leaching behavior of heavy metals from municipal solid waste incineration bottom ash and its geochemical modeling 总被引:1,自引:1,他引:0
Hua Zhang Pin-Jing He Li-Ming Shao Xin-Jie Li 《Journal of Material Cycles and Waste Management》2008,10(1):7-13
With the increase in the number of municipal solid waste incineration (MSWI) plants constructed in China recently, great attention
has been paid to the heavy metal leaching toxicity of MSWI residues. In this study, the effects of various parameters, including
extractant, leaching time, liquid-to-solid ratio, leachate pH, and heavy metal content, on the release properties of Cd, Cr,
Cu, Ni, Pb, and Zn from MSWI bottom ash were investigated. Partial least-squares analysis was employed to highlight the interrelationships
between the factors and response variables. Both experimental research and geochemical modeling using Visual MINTEQ software
were conducted to study the pH-dependent leaching behavior of these metals in fresh and weathered bottom ash, considering
precipitation/dissolution and surface complexation reactions (adsorption by hydrous ferric oxide and amorphous aluminum oxide/hydroxide).
The results showed that leachate pH was the predominant factor influencing heavy metal leachability. The leaching of Cu, Pb,
and Zn was mainly controlled by precipitation/dissolution reactions, whereas surface complexation had some effect on the leaching
of Cr, Cd, and Ni for certain pH ranges. The modeling results aggreed well with the experimental results.
Part of this work was presented at the Fourth International Conference on Combustion, Incineration/Pyrolysis and Emission
Control (i-CIPEC) 相似文献
966.
Increased salinity in spawning and nursery grounds in the Savannah River estuary was cited as the primary cause of a 97% decrease
in adult striped bass (Morone saxatilis) and a concomitant 96% decrease in striped bass egg production. Restoration efforts focused on environmental remediation
and stock enhancement have resulted in restored salinity patterns and increased egg and adult abundances. However, future
water needs or harbor development may preclude further recovery by reducing freshwater inflow or increasing salinity intrusion.
To assess the effect of potential changes in the salinity regime, we developed models relating discharge, tidal phase, and
salinity to striped bass egg and early larval survival and re-cast these in a quantitative Bayesian belief network. The model
indicated that a small upstream shift (≤1.67 km) in the salinity regime would have the least impact on striped bass early
life history survival, whereas shifts >1.67 km would have progressively larger impacts, with a 8.33-km shift potentially reducing
our estimated survival probability by >28%. Such an impact could have cumulative and long-term detrimental effects on the
recovery of the Savannah River striped bass population. The available salinity data were collected during average and low
flows, so our model represents some typical and some extreme conditions during a striped bass spawning season. Our model is
a relatively simplistic, “first-order” attempt at evaluating potential effects of changes in the Savannah River estuarine
salinity regime and points to areas of concern and potential future research. 相似文献
967.
This paper presents the results of kinetic studies to investigate the effect of FeS film formation on the degradation rate of CCl(4) by 99.99% pure metallic iron. The film was formed by submersing metallic iron grains in an oxygen free HCO(3)(-)/CO(3)(2-) electrolyte solution. When the grains had reached a quasi steady-state value of the corrosion potential, Na(2)S((aq)) was injected. Upon injection, a microm thick poorly crystalline FeS film formed immediately on the iron surface. Over time, the iron became strongly corroded and both the FeS film and the metallic iron grains began to crack leading to exposure of bare metallic iron to the solution. The effect of the surface film on the degradation rate of CCl(4) was investigated following four periods of aging, 1, 10, 30, and 60 days. Relative to the controls, the 1-day sulfide-aged iron showed a substantial decrease in rate of degradation of CCl(4.) However, over time, the rate of degradation increased and surpassed the degradation rate obtained in the controls. It has been proposed that CCl(4) is reduced to HCCl(3) by metallic iron by electron transfer. The FeS film is substantially less conducting than the bulk iron metal or non-stoichiometric magnetite and from the results of this study, greatly decreases the rate of CCl(4) degradation relative to iron that has not been exposed to Na(2)S. However, continued aging of the FeS film results in breakdown and stress-induced cracking of the film, followed by dissolution and cracking of the iron itself. The cracking of the bulk iron is believed to be a consequence of hydrogen embrittlement, which is promoted by sulfide. The increase in CCl(4) degradation rate, as the FeS films age, suggests that the process of hydrogen cracking increases the surface area available for charge transfer. 相似文献
968.
Identification of key parameters controlling dissolved oxygen migration and attenuation in fractured crystalline rocks 总被引:1,自引:0,他引:1
In the crystalline rocks of the Canadian Shield, geochemical conditions are currently reducing at depths of 500-1000 m. However, during future glacial periods, altered hydrologic conditions could potentially result in enhanced recharge of glacial melt water containing a relatively high concentration of dissolved oxygen (O2). It is therefore of interest to investigate the physical and geochemical processes, including naturally-occurring redox reactions, that may control O2 ingress. In this study, the reactive transport code MIN3P is used in combination with 2k factorial analyses to identify the most important parameters controlling oxygen migration and attenuation in fractured crystalline rocks. Scenarios considered are based on simplified conceptual models that include a single vertical fracture, or a fracture zone, contained within a rock matrix that extends from the ground surface to a depth of 500 m. Consistent with field observations, Fe(II)-bearing minerals are present in the fractures (i.e. chlorite) and the rock matrix (biotite and small quantities of pyrite). For the parameter ranges investigated, results indicate that for the single fracture case, the most influential factors controlling dissolved O2 ingress are flow velocity in the fracture, fracture aperture, and the biotite reaction rate in the rock matrix. The most important parameters for the fracture zone simulations are flow velocity in the individual fractures, pO2 in the recharge water, biotite reaction rate, and to a lesser degree the abundance and reactivity of chlorite in the fracture zone, and the fracture zone width. These parameters should therefore receive increased consideration during site characterization, and in the formulation of site-specific models intended to predict O2 behavior in crystalline rocks. 相似文献
969.
The Bias of Complementarity Hotspots toward Marginal Populations 总被引:3,自引:1,他引:2
Abstract: It has been suggested that using complementarity to identify networks of important areas for conserving biodiversity may preferentially select areas within the margins of species ranges. We tested this idea by examining the location of complementarity hotspots in relation to two measures of range core-periphery. The first measures patterns of aggregation among records within each species' range to identify areas within the core (i.e., areas with aggregated distributions) and periphery (i.e., areas with scattered distributions) of the range. The second measures spatial turnover among species to identify areas with a high density of range edges. For three selected groups of terrestrial vertebrates in Europe—mammals, birds, and herptiles—areas chosen based on complementarity were located within the margins of species' ranges more often than expected by chance. This pattern was consistent for the two measures of core-periphery we used. The bias of complementarity hotspots toward marginal populations is especially important for species with restricted range sizes. If extinctions are determined mainly by demographic factors, then selecting areas at the peripheries of species' ranges might be a poor option. But if extinctions are determined mainly by extrinsic factors, then peripheral populations might be important to ensure the long-term persistence of species. 相似文献
970.
Population structure of yellowfin tuna (Thunnus
albacares) in the western Pacific Ocean, inferred from microsatellite loci 总被引:1,自引:0,他引:1
Five polymorphic microsatellite loci were examined in 1391 yellowfin tuna (Thunnus albacares) from eight regions of the western (Coral Sea, eastern Australia, Fiji, Indonesia, Philippines and Solomon Islands) and eastern (California and Mexico ) Pacific Ocean. Across all samples, numbers of alleles per locus ranged from 7 to 30 (mean: 17.0), and observed heterozygosities per locus ranged from 0.223 to 0.955 (mean: 0.593). Temporal collections were available for three areas: no significant temporal heterogeneity was observed for the Coral Sea (1991/1992 and 1995/1996 collections) or eastern Australia (1994/1995, 1995/1996, 1996/1997 and 1997/1998), but there was slight but significant heterogeneity at one locus (cmrTa-161) between the two Philippines collections (1994/1995 and 1996/1997). Genotypes generally showed a good fit to Hardy-Weinberg expectations within populations; only cmrTa-208 in the pooled Coral Sea population gave a significant deviation after Bonferroni correction for 40 tests, with a small but significant excess of homozygotes. Four loci showed no evidence of population differentiation following contingency Chi-squared and FST analyses. The fifth locus, cmrTa-161, showed small but significant differentiation (FST=0.002, P<0.001). This heterogeneity was largely a result of the Philippines 1994/1995 and Fiji collections; there was no correlation with geographic distance. The average FST across all five loci was very low (FST=0.002), but it was significant (P<0.001). It is unclear whether this low but significant differentiation reflects noise in the dataset, perhaps arising from experimental error, or real population differentiation. The finding of very limited population heterogeneity accords with most of the earlier allozyme and mitochondrial DNA studies of yellowfin tuna in the Pacific Ocean. 相似文献