Role of sodium ions in the vitrification process: Glass matrix modification,slag structure depolymerization,and influence of metal immobilization

This study investigates the role of Na ions, a common flux, in the vitrification process. Artificial glass systems composed of Al₂O₃, CaO, and SiO₂ with various Na concentrations were melted at 1450 °C. The specimens were cooled by air cooling and water quenching and the metal mobility was evaluated using a sequential extraction procedure. The X-ray diffraction analysis and scanning electron microscopy observations showed that Na ions governed the air-cooled slag’s structure. Na ions initially depolymerized CaSiO₃-linked chains into CaSiO₃ chains, and further cut them into shorter and nonuniform ones, making the slag structure amorphous. With even more Na ions, CaSiO₃ chains were divided into single SiO₄ tetrahedrons and formed Na-related crystals (Na₂Ca₃Si₂O₈ and NaAlSiO₄). The phase distributions of Al, Cr, Cu Mn, and Ni showed that Na has a positive effect on the immobilization of heavy metals at suitable concentrations, but a negative effect when in excess amounts.

Implications:Vitrification has been widely used to treat hazardous materials. The Na-bearing additives were often used as a flux to improve the melting process. This study described the role of Na played in the vitrification process. The Na ions acted as glass modifier and depolymerize the chain structure of slag. With adequate addition amount of Na ions, the immobilization of heavy metals was improved. The results provided much information about the crystalline phase variation, metal mobility, and surface characteristics while Na serves as a flux.     

Ambient Air Particulates Bound Mercury Hg(p) Study Among Four Crops (Rice,White Cabbage,Arden Lettuce,and Gynura) at a Characteristic Sampling Site

The main purpose of this study was to monitor ambient air particulates and particulate-bound Hg (Hg[p]) compositions in different crops in the coastal zone in the Taichung, Taiwan, area at a sampling site during 2013 October to 2013 December. In addition, a direct mercury analyzer (DMA-80) was used to directly detect the concentration with measured results by the regression equation of Hg in the ambient air. The results indicated that: 1) the mean values of ambient air Hg(p) compositions in rice displayed no significant differences for weeks one, two, and three versus those of the other crops (white cabbage, Arden lettuce, and Gynura procumbens); 2) for white cabbage, the higher the humidity, the lower the average ambient air Hg(p) compositions that were obtained, a phenomenon that was also reflected on the crops of white cabbage and G. procumbens; 3) Arden lettuce displayed no significant differences in the leaf Hg(p) compositions during weeks one, two, and three; however, the stem portions displayed significant differences in Hg(p) compositions during weeks two and three; and 4) the Spearman statistical method showed the mean differences for ambient air Hg(p) at the Long-jing sampling site (coastal regions) with four different crops (rice, white cabbage, Arden lettuce, and Gynura) in central Taiwan. The results further revealed no significant differences in mean values.     

Stabilization of residues obtained from the treatment of laboratory waste: Part 2--transformation of plasma vitrified slag into composites

The Sustainable Environment Research Center of National Cheng Kung University in Taiwan has set up a treatment plant to dispose of laboratory waste. In the treatment process, the residue from the incineration system and the physical and chemical system is vitrified by a plasma melting system. Part 1 of this study described the treatment path of metals during vitrification. In Part 2, plasma vitrified slag is reused by using a molding technology. Unsaturated polyester resin and glass fiber were used as the molding material and additive, respectively, in the molding process. With an appropriate mixing ratio of unsaturated polyester resin, glass fiber, and slag, the physical properties of composites improved, and the ultimate tensile strength reached 17.6 MPa. However, an excess amount of slag reduced the strength and even retarded the production of composites. Differential thermal analysis and the water bathing test results show that the composite decomposed at 80 degrees C and that it vaporized at 187 degrees C. Although the unsaturated polyester resin decomposed, the metal encapsulated in the slag did not leach out. The results show that the reuse of slag using molding technology should be taken into consideration.     

INFLUENCE OF BATHYMETRIC CHANGES ON HYDRODYNAMICS AND SALT INTRUSION IN ESTUARINE SYSTEM1

ABSTRACT: A vertical (laterally integrated) two‐dimensional numerical model has been applied to study the hydrodynamic characteristics and salt water intrusion in the Tanshui River estuarine system. The cross‐sectional profiles measured in 1978 and 1994 are schematized for model simulations. Detailed model calibration and verification have been conducted with water surface elevations, tidal current, salinity distributions, and residual velocities measured. The overall performance of the model is in qualitative agreement with the available field data. The model was then used to study how hydrodynamics and salt water intrusion change in response to changes in bathymetry. The model simulations indicate that more tidal energy propagates into the estuarine system in 1994 because of the substantial increase in river cross‐sections. The limits of salt intrusion in 1994 extended farther inland than those in 1978. On the other hand, the extent of mangrove wetland in the lower estuary has increased over the past 20 years and is likely a result of the increased salinity in the estuary.     

WATER QUALITY MODELING FOR THE FEITSUI RESERVOIR IN NORTHERN TAIWAN1

ABSTRACT: Field data collected from the Feitsui Reservoir in Taiwan indicate that the water is at a stage between mesotrophic and eutrophic. Recent measurements such as total phosphorus, chlorophyll a and Secchi depth levels suggest that the water quality has been declining. A two‐dimensional, laterally averaged, finite difference hydrodynamic and water quality model was used to simulate the water quality in the Feitsui Reservoir in an effort to determine sound water quality management strategies. The model was calibrated and verified using data collected in 1996 and 1997. The calibrated model was used to simulate algal biomass (in terms of chlorophyll a) levels under various wasteload reduction scenarios. Model results show that 50 percent reduction of the total phosphorus load will improve the existing water quality, shifting the trophic status from eutrophic/mesotrophic to oligotrophic. The modeling effort has yielded valuable information that can be used by decision makers for the evaluation of different management strategies of reducing watershed nutrient loads.     

Characteristics of heavy metal absorption of river bed sludge components

Chronic inhalation of aerosols of different Cd compounds by rats gave sufficient evidence that inhaled Cd is a lung carcinogen in rats. In contrast, the evidence in humans has been termed limited that inhaled Cd causes lung cancer in occupationally exposed humans. In order to assess the carcinogenic potential of ambient air concentrations of Cd, the accumulated dose of Cd in lung tissue from a rat inhalation study was modelled taking into account deposition and retention of Cd in the lung. A lung Cd—cancer incidence relationship could then be established, and an equivalent human exposure could be calculated using man specific pulmonary Cd retention and deposition data for Cd containing particle sizes in the ambient air. Linear interpolation to low doses showed that the pulmonary carcinogenic risk from inhalation of environmental airborne Cd is generally very low, but may reach about 1 × 10^‐4 in polluted industrialized areas. Combined exposures to Cd plus other carcinogens or air pollutants may increase the risk considerably. Cd in cigarette mainstream smoke was estimated to contribute less than 5 % of the total lung cancer risk from smoking cigarettes. However, the influence of co‐exposure to other compounds in cigarette smoke is not known and should be taken into account.     

Assessing carbon footprint in the life cycle of accommodation services: the case of an international tourist hotel

The accommodation sector is the most demanding energy consumer among all building stock categories. This study quantifies an international tourist hotel in Taiwan to holistically estimate the greenhouse gas emissions of hotel accommodation services through a complete life cycle inventory. The study also investigates the difference between the carbon emissions of the baseline and reduction years to understand the effects of carbon emission reduction on the hotel industry. Results show that energy consumption is the main source of carbon footprint. However, the carbon emissions of other activities, such as the production and transportation of hotel amenities and laundry services, are 15.90% for the baseline year and 16.03% for the reduction year. These values are larger than the 5% cutoff rule according to PAS 2050. Thus, these factors should also be considered in assessing the carbon emissions of accommodation services. Hotel occupancy rate significantly affects carbon emissions during a one-night stay in a standard room as the functional unit. The selection of the functional unit should be considered in the hotel strategy. Although this case study involves an international tourist hotel in Taiwan, the findings and recommendations for improvements can be applied elsewhere.     

Utilization of waste from the silicon carbide grinding sludge and stone sludge as source of silicon aluminum for the synthesis of the amine functional mesoporous humidity control material

Journal of Material Cycles and Waste Management - This study outlines the synthesis of low-cost mesoporous silica nanomaterials (MSN) from stone sludge (SS) and silicon carbide grinding sludge...     

Review of PSR framework and development of a DPSIR model to assess greenhouse effect in Taiwan

In dealing with the complex issues of greenhouse gas (GHG) emission and climate change mitigation, many interrelated factors such as cost, level of technology development, supply and demand of energy, structure of industry, and expenditures on research and development exist. Using indicators to monitor environmental impacts and evaluate the efficacies of policies and regulations has been practiced for a long time, and it can serve as a useful tool for decision making and for comparison between different countries. Although numerous indicators have been developed for relevant subjects, integrated approaches that consider individual changes, dynamic interaction, and multi-dimensions of indicators are scarce. This paper aimed to develop a Driving Force-Pressure-State-Impact-Response (DPSIR) framework to assess the problems. This DPSIR model is mainly related to energy consumption, environmental impacts, and policy responses. The objectives of the paper were: (1) conduct a literature review on the indicators that have been used in GHG-related studies; (2) develop a DPSIR model that incorporates GHG-related indicators and evaluate their relationships using a cause?Ceffect chain of GHG emission; and (3) develop a calculative method that can be used to explain the dynamic correlation among the interdependent indicators. Taiwan is a significant source of global GHG emissions. A case study, using the developed framework and Taiwan??s actual data of the past two decades, was conducted. The results indicate that regulatory strategies for pollution control are inadequate in terms of ensuring environmental quality, and the nature does not have the capability to revert the impacts from the existing level of pollution.     

Comparison of polycyclic aromatic hydrocarbon emissions on gasoline- and diesel-dominated routes

Three diesel-dominated routes (DDRs) and three gasoline-dominated routes (GDRs) were chosen as the study sites. The total number of vehicles on GDRs (47,200) was much higher than that on DDRs (14,500). The concentration of polycyclic aromatic hydrocarbons (PAHs), elemental carbon, organic carbon, and metals from GDR roadsides was higher than that for DDRs. The diagnostic ratios (ANTHR/PHE + ANTHR, FLT/FLT + PYR, BaA/BaA + CHR, and IND/IND + BghiP + ANTHN) all indicated that the major PAH source on DDR and GDR was emissions from vehicle engine combustion. The marked diesel ratios of low molecular weight PAH_2.5/T-PAH_2.5, methyl-PAH_2.5/T-PAH_2.5, methyl-PHE/PHE, and Mo/PM_2.5 on DDRs were higher than those on GDRs. Significant correlations were found between the number of vehicles and the concentration of T-PAH_2.5, Car-PAHs_2.5, and BaP_eq2.5 on DDRs and GDRs. The increase in the levels of T-PAH_2.5, Car-PAHs_2.5, and BaP_eq2.5 per 100 vehicles on DDRs was about 3.3, 3.5, and 4.2 times higher than that on GDRs, respectively. The higher percentage of high-exhaust volume from the larger amount of diesel vehicles on DDRs than that on GDRs was the main factor leading to these results. The diagnostic ratios BaA_2.5/CHR_2.5 and (BbF + BkF)_2.5/BghiP_2.5 showed significant differences between the fine PAH sources emitted on DDRs and GDRs, whereas the diagnostic ratios Me-PAH_2.5/T-PAH_2.5 and (BbF + BkF)_2.5/BghiP_2.5 showed good correlations with the percentages of diesel exhaust volume in the total exhaust volume (E _diesel/E _total) on DDRs.