Suppression of Soot by Metal Additives During the Combustion of Polystyrene

This paper describes an experimental study on the suppression of soot by metal additives during the combustion of polystyrene (PS). A two-dimensional flame generated by using a Wolfhard-Parker type diffusion flame burner was used to simulate practical combustion situations. The PS was continuously fed to the burner and, by controlling the feed rate, the combustion was maintained at a steady state. The additives tested were the salts of Li, Na, K, Mg, Ca, Sr, and Ba, and the combinations of the salts of K and Ca, Sr, or Ba. These additives were added to the flame in the form of small drops of their aqueous solutions generated by an ultrasonic atomizer. Since the flow rate of the carrier gas (air) is very small, this addition causes no noticeable disturbance to the flame. The effectiveness of the alkali metals follows the order of their ease of ionization, i.e., K > Na > Li, and that of the alkaline-earth metals: Ba > Sr > Ca > Mg. At low addition rates, the effectiveness increases with increasing addition rate but becomes unaffected at high addition rates and the maximum percentage of soot suppressed is approximately 50 percent. The combinations of the two metals (i.e., K and Ca, Sr, or Ba) are much more effective than each single metal at the same addition rates and the maximum percentage of soot suppressed reaches approximately 90 percent. It is proposed that the alkaline-earth metals catalyze the ionization of the alkali metals, thus significantly enhancing the effect on soot suppression.     

Estimation and field measurement of methane emission from waste landfills in Hanoi, Vietnam

A methodology for estimating the methane emissions from waste landfills in Hanoi, Vietnam, as part of a case study on Asian cities, was derived based on a survey of documents and statistics related to waste management, interviews with persons in charge, and field investigations at landfill sites. The waste management system in Hanoi was analyzed to evaluate the methane emissions from waste landfill sites. The quantity of waste deposited into the landfill was evaluated from an investigation of the waste stream. The composition of municipal waste was surveyed in several districts in the Hanoi city area, and the quantities of degradable organic waste that had been deposited into landfill for the past 15 years were estimated. Field surveys on methane emissions from landfills of different ages (0.5, 2, and 8 years) were conducted and their methane emissions were estimated to be 120, 22.5, and 4.38 ml/min/m², respectively. The first-order reaction rate of methane generation was obtained as 0.51/year. Methane emissions from waste landfills were calculated by a first-order decay model using this emission factor and the amount of landfilled degradable waste. The estimates of methane emissions using the model accorded well with the estimates of the field survey. These results revealed that methane emissions from waste landfills estimated by regional-specific and precise information on the waste stream are essential for accurately determining the behavior of methane emissions from waste landfills in the past, present, and future.     

Effect of reservoir flushing on downstream river water quality

The effect of short-term reservoir flushing on downstream water quality in the Geum River, Korea was studied using field experiments and computer simulations. The reservoir release was increased from 30 to 200 m(3)/s within 6 h for the purpose of this experiment. The flushing discharge decreased the concentrations of soluble nitrogen and phosphorus species considerably, but the experimental results revealed a negative impact on organic forms of nutrients and biochemical oxygen demand (BOD). A dynamic river water quality model was applied to simulate the river hydraulics and water quality variations during the event. The model showed very good performance in predicting the travel time of flushing flow and the variations of dissolved forms of nitrogen and phosphorus constituents. However, it revealed a limited capability in simulating organic forms of nutrients and BOD because it does not consider the re-suspension mechanism of these constituents from sediment during the wave front passage.     

COMPARATIVE STUDY OF DROUGHT PREDICTION TECHNIQUES FOR RESERVOIR OPERATION1

ABSTRACT: Predicting the likelihood of a drought markedly enhances the efficiency of reservoir operations. This study applies the kriging method and time series analysis to predict inflows to Shihmen Reservoir in northern Taiwan. A subsequent reservoir operation simulation is employed to determine the drought lead time (DLT), the time before the onset of a drought. A more efficient reservoir operational strategy can be established with the aid of DLT and the probability of successful drought prediction (P s). Simulation results of reservoir operation over a period of three decades demonstrate that, at one month DLT, the kriging approach achieves 0.86 of P s for moderate droughts and 0.94 of P s for severe droughts. The kriging approach generally outperformed the time series approach in terms of DLT, P s of drought prediction, and the number of correctly predicted drought events.     

Monitoring of non-point source pollutants load from a mixed forest land use

The aim of this study was to determine the unit load of NPS (non-point source) pollutants including organic variables such as BOD (biochemical oxygen demand),COD (chemical oxygen demand) and DOC (dissolved organic carbon),nitrogen and phosphorus constituents,and suspended solids (SS) and their event mean concentration (EMC) of runoff flows from a water-shed of mixed forest land use by intensive field experiments.Field monitoring for continuous measurements of rainfall,flow,and water quality was conducted over 12 storm events during 2008–2009 using automated and manual sampling methods.The EMCs of individual runoff event were estimated for each water quality constituent based on the flow rate and concentration data of runoff discharge.The average EMCs of BOD,COD,DOC,SS,TN (total nitrogen),NH 4+ -N,NO 3- -N,TP (total phosphorus),PO 43- -P from the mixed forest land were 1.794,3.498,1.462,10.269,0.862,0.044,0.634,0.034,and 0.005 mg/L,respectively.The annual unit loads of BOD,COD,DOC,SS,TN,NH 4+ -N,NO 3- -N,TP and PO 43--P were estimated as 66.9,133.2,55.5,429.8,36.5,1.6,26.9,1.3 and 0.1 kg/(ha·yr),respectively.In addition,affecting parameters on the EMCs were investigated by statistic analysis of the field data.As a result,significant correlations with precipitation,rainfall intensity,and total runoff flows were found in most constituents.     

Observations of Dust-Storms in China, Mongolia and Associated Dust Falls in Korea in Spring 2003

A joint monitoring of dust-storms that occurred in East Asia from March until May 2003 has been carried. Our discussions include dust-storm observations in the source areas of China and Mongolia, and measurements with satellites and ground monitors in central Korea. Differences were found in the definition and measurement of dust-storms. Over the source area of Mongolia there were 6 dusty days in March, 18 days in April, and 10 dusty days in May. In Inner Mongolia of northern China there were 4 dust-storms with 14 dusty days observed over the three months. In central Korea, a sink area, there were 4 cases of weak dust-storm and 17 dusty days in the spring of 2003. The highest PM10 value was 607 μgm⁻³ and PM 2.3 was 149 μgm⁻³, respectively. These observations identify the growing need for further universal observation practices and dust-storm reporting in future. Observations indicated that snow covered the central part of the Gobi Desert, near the boundary of China and Mongolia, from December until mid-March. This is in contrast to other years when the Gobi was relatively wet, producing unfavourable conditions for the formation of intense dust-storms. In addition, the very strong winds associated with intense cyclones and anticyclones were not apparent and the systems shifted northward during the spring. As a result, the frequency and intensity of observed dust-storms in 2003 in this region were very low. This confirms that there is variability in the frequency of dust-storm formation due to the current process of desertification and climate change.     

The responses and prospects of sustainable development for Guangzhou and Hong Kong

The ability to achieve urban sustainability has become an indication of the competence of a municipal government aiming to gain world class status for the city. While both Guangzhou and Hong Kong are Chinese cities having their own formulation of urban sustainability, the implementation details and the actual sustainability blueprints are very different. As a result, the outcomes and prospects for urban sustainability are also different.

Hong Kong has adopted a less integrative and more institutionally-oriented approach for urban sustainability. Guangzhou has used the conventional approach to formulate an integrated sustainability programme for its local Agenda 21. Hong Kong's action plan emphasizes improving coordination, making objective assessments and achieving consistency in policy-making. Guangzhou, on the other hand, emphasizes the meeting of concrete environmental targets. Unfortunately, the new institutional arrangement and monitoring tools adopted by Hong Kong have not been able to achieve the original intent and neither is there the intention to go too far beyond the weak sustainability approach. On the contrary, Guangzhou has planned and attempted to incorporate industrial ecology in its development regime while heavily investing into pollution control programmes and pushing forward a green community programme at the grass-roots level.     

A comparison of waste-reduction practices and new environmental paradigm of rural and urban Chinese citizens

This paper compares the public attitudes of three southern Chinese cities/towns, namely Guangzhou, Dongguan, and Yuanzhou on waste recycling and avoidance, and the New Environmental Paradigm (NEP). The latter describes the concept of treating the resources and the ecosystems on Earth as things having their own rights rather than being subordinate and subservient to humans. These three places are chosen to represent areas in different stages of urbanization in the Guangdong province. As Hong Kong is also a southern Chinese city, where data of similar nature are available, comparison with Hong Kong is also made. It was found that the support for source separation of household waste in the rural and urban areas in mainland China was greater than that found in Hong Kong. Concerning actual practices on waste separation, about 85% of the respondents in the cities and almost all of the rural household surveyed have the habit of saving up and selling the recyclables. It is estimated that about 11-13% of the household waste was diverted in such a way. This is higher than the estimated 8% household waste recovery rate of Hong Kong. The majority of the respondents in the three surveyed cities have recovered household recyclables in the past but with higher family incomes, it was now less common. On the contrary, the lower income group tended to recover greater portion of their waste for selling to the waste depots. These findings have implications on the future waste management policy formulation in China. Regarding the acceptance of the New Environmental Paradigm, it was found that the rural population scored better than the urban population and they tended to agree more frequently with the NEP. However, the rural population perceives a greater potential for industrial and urban development without dampening environmental quality. It was also found that the NEP scores of the mainland Chinese are higher, in general, than their Hong Kong counterparts as measured in early 1990s. Insufficient public support has often been a concern for source separation programmes in all countries despite the obvious waste management benefits of recycling. This study shows that there is overwhelming support for source separation of waste in Mainland China, whether it is in rural or urban communities, and that most people are already undertaking source separation due to the redemption value of the recyclables. Therefore, for policy-makers, the concern should not be on whether the public knows how to separate the waste but rather on how to motivate them to separate waste for the good of society, and how to maintain an effective market for recyclables.