城市灾时大范围人员应急疏散探讨

人类面临着许多自然的和人为的灾害,比如最近发生的印度洋大海啸和2001年的美国"9·11"恐怖袭击事件等.当这类重大灾害性事件发生时,在短时间内安全地大范围疏散转移高密集人群,实施科学的应急救灾策略,是减轻灾害后果严重性的重要措施之一.探讨了如何建立一个综合性的疏散规划模型,为人员应急疏散管理提供决策支持.     

Decomposition of perfluorooctanoic acid by microwaveactivated persulfate: Effects of temperature, pH, and chloride ions

Microwave-hydrothermal treatment of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water with persulfate (S₂O₈²⁻) has been found effective. However, applications of this process to effectively remediate PFOA pollution require a better understanding on free-radical scavenging reactions that also take place. The objectives of this study were to investigate the effects of pH (pH = 2.5, 6.6, 8.8, and 10.5), chloride concentrations (0.01–0.15 mol·L⁻¹), and temperature (60°C, 90°C, and 130°C) on persulfate oxidation of PFOA under microwave irradiation. Maximum PFOA degradation occurred at pH 2.5, while little or no degradation at pH 10.5. Lowering system pH resulted in an increase in PFOA degradation rate. Both high pH and chloride concentrations would result in more scavenging of sulfate free radicals and slow down PFOA degradation. When chloride concentrations were less than 0.04 mol·L⁻¹ at 90°C and 0.06 mol·L⁻¹ at 60°C, presence of chloride ions had insignificant impacts on PFOA degradation. However, beyond these concentration levels, PFOA degradation rates reduced significantly with an increase in chloride concentrations, especially under the higher temperature.     

Tropospheric Sulfate Aerosol Formation Via Ion-Ion Recombination

ABSTRACT

We propose a source of aerosols in the lower atmosphere associated with the creation, growth, and recombination of ubiquitous cosmogenically generated ions. This particle source should be favorable in the relatively clean, stable marine boundary layer, providing a uniform, continuous fine particle generator in the presence of dimethylsulfide emissions. Through this mechanism, new sulfate aerosols can be formed at sulfuric acid vapor partial pressures well below the supersaturations required for homogeneous binary nucleation of sulfuric acid/water solutions, which is consistent with numerous observations of new particle formation under sub-saturated conditions. The evolving aerosols in turn control the acid vapor concentration and thus modulate the sizes of the precursor ions and the rate of new particle formation. A simple model representing this nonlinear coupled system predicts that the physical and chemical processes connecting ions, vapors, and aerosols effectively constrain the particle population to a relatively narrow range of values. This self-limiting behavior may explain in part the apparent stability of the marine sulfate aerosol, with mean concentrations of the order of several hundred per cubic centimeter.     

Artificial aggregate made from waste stone sludge and waste silt

In this research, waste stone sludge obtained from slab stone processing and waste silt from aggregate washing plants were recycled to manufacture artificial aggregate. Fine-powdered stone sludge was mixed with waste silt of larger particle size; vibratory compaction was applied for good water permeability, resulting in a smaller amount of solidifying agent being used. For the densified packing used in this study, the mix proportion of waste stone sludge to waste silt was 35:50, which produced artificial aggregate of more compact structure with water absorption rate below 0.1%. In addition, applying vibratory compaction of 33.3 Hz to the artificial aggregate and curing for 28 days doubled the compressive strength to above 29.4 MPa. Hence, recycling of waste stone sludge and waste silt for the production of artificial aggregate not only offers a feasible substitute for sand and stone, but also an ecological alternative to waste management of sludge and silt.     

Fines migration from soil daily covers in Hong Kong landfills

Laboratory tests using 240 mm diameter columns were conducted to study fines migration in conditions that simulate daily soil covers in Hong Kong municipal solid waste landfills. Five factors suspected to affect fines migration were examined: moisture content at soil compaction, overburden pressure, pumping rate, cover thickness, and soil-waste interface condition. The results show that moisture content at compaction, cover thickness, and soil-waste interface are the most influential parameters on fines migration in completely decomposed granite daily covers. The measured equivalent sizes of migratory fines from the soil covers were in the range of 4–140 μm. The majority of migratory fines migrated during first permeations, representing 64–86% of the total by mass. Larger particles tended to migrate from the soil mass during the saturation process. In a typical run, about 0.0018% of the total cover soil (by dry weight) was washed out during a typical 1 h rainfall event. The results of the laboratory studies point to important engineering implications on the operation of local MSW landfills regarding the use of sandy daily covers.     

Environmental and economic aspects of water kiosks: Case study of a medium-sized Italian town

The consumption of bottled water in Italy began in the 1970s. Since then, this usage has grown considerably, also as a result of changes in habits. The environmental impact as a result of the water production chain is very significant; it would be considered, for example, the use of plastic bottles, the consumption of oil in the production of the bottles, the emission of air from the vehicles that transport the bottles, non-recycled plastic packaging, etc.In this study, considering the comparison between two situations, use of bottled water and use of water kiosk (WK), an environmental and economic impact evaluation has been done. The study considered the production of a WK in a town with 9000 inhabitants, which supplies controlled, still and sparkling water, with an organoleptic quality higher than tap water coming from the aqueduct. In particular, taking into consideration the environmental aspects, specific attention was paid both to CO₂ emissions and PET bottle waste reduction. The economic impact evaluation was carried out from the consumer’s point of view. In order to provide a supply service that was economically sustainable, a calculation was done with the aim of determining a specific fee for the supplied water. Moreover, a comparison has been made between quality parameters achieved with the analysis of water from aqueducts with the limits established in the Italian legislation and the parameters of several Italian water brands.The study has the aim at considering the opportunity to follow a different people’s habits, closer to the concept of sustainability, reducing the environmental charge related to the realization, transport and consumption of plastic water bottles without significant reduction of the quality of the service and with convenient and interesting economic implications. In fact the results of the study show that the alternative of WKs is more efficient in economic and environmental terms respect to the use of bottled water.     

Comparison of ozone uptake and sensitivity between a phytotron study with young beech and a field experiment with adult beech (Fagus sylvatica)

Chamber experiments on juvenile trees have resulted in severe injury and accelerated loss of leaves along with reduced biomass production under chronically enhanced O3 levels. In contrast, the few studies conducted on adult forest trees in the field have reported low O3 sensitivity. In the present study, young beech in phytotrons was more sensitive to O3 than adult beech in the field, although employed O3 regimes were similar. The hypotheses tested were that: (1) differences in O3 uptake were caused by the ontogenetically higher stomatal conductance of young compared to adult trees, (2) the experimental settings in the phytotrons enhanced O3 uptake compared to field conditions, and (3) a low detoxification capacity contributes to the higher O3 sensitivity of the young trees. The higher O3 sensitivity of juvenile beech in the phytotrons is demonstrated to relate to both the experimental conditions and the physiological responsiveness inherent to tree age.     

Modeling competitive adsorption of molybdate, sulfate, selenate, and selenite using a Freundlich-type multi-component isotherm

This study examined the interactions of MoO4(2-) + SO4(2-), MoO4(2-) + SeO4(2-), and MoO4(2-) + SeO3(2-) systems on gamma-Al2O3 to better understand the competitive adsorption of these anions in the natural environment. The Freundlich isotherms of anionic adsorption onto gamma-Al2O3 in single and binary solutes were also investigated to estimate the competition between these anions. Experimental results indicate that a higher concentration of competitive solute yields a higher efficiency of the competitive solute's prevention of MoO4(2-) adsorption. The most significant result was found in the MoO4(2-) + SeO3(2-) system. The Freundlich isotherm constant (n) increases with the competitive solute concentration. The suitability of a Freundlich-type isotherm, the Sheindorf-Rebuhn-Sheintuch (SRS) equation, and the modified SRS equation in representing the competitive adsorption of MoO4(2-), SO4(2-), SeO4(2-), and SeO3(2-) on gamma-Al2O3 surface, was also examined. Each set of isotherm data was found to conform to linear SRS expressions, allowing competition coefficients to be derived on a concentration basis for each binary-solute system. The competition coefficient aij and relative affinity coefficients alphaij can be seen as a way to quantify competitive interactions. The proposed SRS and modified SRS equations are simple mathematical expressions accounting for competitive interactions of anions present in a mixture for the range of concentrations over which each individual component exhibits Freundlich behavior.