Biomedical subjects

Shang-Lien Lo

Publications and source records attributed to Shang-Lien Lo.

At least 19 recordsLinked to original sources

PubMed2006

Uncertainty in watershed response predictions induced by spatial variability of precipitation.

Negligence to consider the spatial variability of rainfall could result in serious errors in model outputs. The objective of this study was to examine the uncertainty of both runoff and pollutant transport predictions due to the input errors of rainfall. This study used synthetic data to represent the "true" rainfall pattern, instead of interpolated precipitation. It was conducted on a synthetic case area having a total area of 20 km(2) with ten subbasins. Each subbasin has one rainfall gauge with synthetic precipitation records. Six rainfall storms with varied spatial distribution were generated. The average rainfall was obtained from all of the ten gauges by the arithmetic average method. The input errors of rainfall were induced by the difference between the actual rainfall pattern and estimated average rainfall. The results show that spatial variability of rainfall can cause uncertainty in modeling outputs of hydrologic, which would be transport to pollutant export predictions, when uniformity of rainfall is assumed. Since rainfall is essential information for predicting watershed responses, it is important to consider the properties of rainfall, particularly spatial rainfall variability, in the application of hydrologic and water quality models.

Environmental Monitoring↗

PubMed2006

Leachability of metals from sludge-based artificial lightweight aggregate.

Metal sludge from industrial wastewater treatment plants was mixed with mining residues to be recycled into lightweight aggregate (LWA) through sintering at different temperatures. The physical properties of the LWA thus obtained were examined by scanning electron microscopy analyzer (SEM) coupled with an energy dispersive X-ray analyzer (EDX). The sequential extraction method combined with inductively coupled plasma atomic emission spectrometry (ICP-AES) was employed to determine the concentration and distribution of hazardous toxic elements in the metal sludge-based artificial LWA. The results show that the leaching concentrations of Cd, Cr, Cu, and Pb present in the non-sintered raw aggregate pellets reached 7.4, 68.0, 96.0, and 61.4 mg/l, respectively, far exceeding the regulatory threshold. Sintering at 1150 degrees C for 15 min results in stronger chemical bonds being formed between the elements. Hence, after the first three steps of sequential extraction, the concentrations of Cr, Cu, and Pb reached 2.69, 1.50, and 1.88 mg/l at 1150 degrees C, while the final residues had total concentrations of 96.1, 88.4, and 60.6 mg/kg, respectively, with Cd undetected in both phases. The concentration levels fell within the regulatory threshold, indicating that the LWA fabricated from recycled metal sludge contains elements that are toxic and hazardous but not leached. Having no harmful effect on the environment, the metal sludge-based artificial LWA is not only safe but also practical with good physical properties.

Conservation of Natural Resources↗

PubMed2006

Simulation the kinetics of fluoride removal by electrocoagulation (EC) process using aluminum electrodes.

A variable order kinetic (VOK) model derived from the Langmuir equation was applied to specify the kinetics of the fluoride removal reaction for electrocoagulation (EC). Synthetic solutions were employed to elucidate the effects of the initial fluoride concentration, the applied current and the initial acidity on the simulation results of the model. The proposed model successfully describes the fluoride removal reaction, except in a system in which the initial concentration of the acid is less than the initial fluoride concentration. The violent change of pH companying with the appearance of equivalence point in the titration curves should be the main reason the VOK model fails to simulate the defluoridation in the systems with an initial acidity higher than initial fluoride concentration.

Aluminum↗

PubMed2006

Production of lightweight aggregates from mining residues, heavy metal sludge, and incinerator fly ash.

In this study, artificial lightweight aggregate (LWA) manufactured from recycled resources was investigated. Residues from mining, fly ash from an incinerator and heavy metal sludge from an electronic waste water plant were mixed into raw aggregate pellets and fed into a tunnel kiln to be sintered and finally cooled rapidly. Various feeding and sintering temperatures were employed to examine their impact on the extent of vitrification on the aggregate surface. Microstructural analysis and toxicity characteristic leaching procedure (TCLP) were also performed. The results show that the optimum condition of LWA fabrication is sintering at 1150 degrees C for 15 min with raw aggregate pellets fed at 750 degrees C. The rapidly vitrified surface envelops the gas produced with the increase in internal temperature and cooling by spraying water prevents the aggregates from binding together, thus forming LWA with specific gravity of 0.6. LWA produced by sintering in tunnel kiln shows good vitrified surface, low water absorption rate below 5%, and low cylindrical compressive strength of 4.3 MPa. In addition, only trace amounts of heavy metals were detected, making the LWA non-hazardous for construction use.

Aluminum Silicates↗

PubMed2006

Numerical simulation of a steam-injection pilot study for a PCP-contaminated aquifer.

The following study was focused on the simulation of a steam-injection field pilottest conducted in our past research. The scope of research contained two main subjects: heat transfer and contaminant transport when steam was injected into a pentachlorophenol (PCP)-contaminated aquifer. Numerical simulation of the heat transfer during the field test showed that vertical permeability is more influential to the distribution of water temperature than the horizontal permeability. If the vertical permeability is relatively high, the steam in the aquifer has a higher tendency to migrate upward and cause the aquifer temperature to rise faster. The simulation results also showed that heat convection is very sensitive to the soil permeability. Therefore, high permeability media makes the effect of heat convection more important on applying the steam-injection method. Heat conduction dominates the heat transfer within the hot aqueous zone. However, the hot aqueous zone is relatively smaller than the steam zone when steam is injected into the aquifer. Therefore, heat conduction is not as important as heat convection within the steam zone, which is the same result observed in the field test. Specific heat of soil media is also a sensitive factor. A numerical simulator, T2VOC, was utilized to simulate the PCP transport in the aquifer when steam was injected into the aquifer. The results showed that the shape of PCP distribution was identical to that of steam. It illustrated thatthe steam carried PCP upward and laterally. The high vertical soil permeability causes the steam to migrate upward with PCP easily. A low partitioning coefficient allows PCP to be desorbed easier, also an important factor. A majority of the PCP in the soil was transferred to the aqueous phase as the water temperature increased, showing similar results to those observed in the field test. According to the sensitivity analysis, PCP transport is more sensitive to the vertical permeability than the partitioning coefficient. The steam-injection rate is also an important operation parameter and may determine the success of the remediation work.

Models, Chemical↗

PubMed2006

Effect of precursor concentration on the characteristics of nanoscale zerovalent iron and its reactivity of nitrate.

Differing precursor concentrations, 1.0, 0.1, and 0.01 M FeCl(3) x 6H(2)O, were performed to produce nanoscale Fe(0) and the results were discussed in terms of the specific surface area, particle size and electrochemical properties. The results indicated that the nanoscale Fe(0) prepared by 0.01 M FeCl(3) had absolutely reduced in size (9-10nm) and possessed the greatest specific surface area (56.67 m(2) g(-1)). These synthesized nanoscale Fe(0) particles were attempted to enhance the removal of 40 mg-NL(-1) unbuffered nitrate solution. The first-order degradation rate constants (k(obs)) increased significantly (5.5-8.6 times) with nanoscale Fe(0) prepared by 0.01 M precursor solution (Fe(0.01 M)(0)). When normalized to iron surface area concentration, the specific rate constant (k(SA)) was increased by a factor of approximately 1.7-2.4 using Fe(0.01 M)(0) (6.84 x 10(-4) L min(-1) m(-2) for Fe(0.01 M)(0), 4.04 x 10(-4) L min(-1) m(-2) for Fe(0.1 M)(0) and 2.80 x 10(-4) L min(-1) m(-2) for Fe(1 M)(0)). The rise of reactivity of the reactive site on the Fe(0.01 M)(0) surface was indicated by the specific rate constant (k(SA)) calculation and the i(0) value of the electrochemical test.

Iron↗

PubMed2006

Microwave enhanced stabilization of heavy metal sludge.

A microwave process can be utilized to stabilize the copper ions in heavy metal sludge. The effects of microwave processing on stabilization of heavy metal sludge were studied as a function of additive, power, process time, reaction atmosphere, cooling gas, organic substance, and temperature. Copper leach resistance increased with addition of aluminum metal powder, with increased microwave power, increased processing time, and using a gaseous environment of nitrogen for processing and air for cooling [N2/air]. The organic in the sludge affected stabilization, whether or not the organic smoldered. During heating in conventional ovens, exothermic oxidation of the organic resulted in sludge temperatures of about 500 degrees C for oven control temperatures of 200-500 degrees C. After microwave heating dried the sludge, the sludge temperature rose to 500 degrees C. The reaction between copper ions and metal aluminum in the dried sludge should be regarded as a solid phase reaction. Adding aluminum metal powder and reaction temperature were the key parameters in stabilizing copper in the heavy metal sludge, whether heated by microwave radiation or conventional oven. The mass balance indicates insignificant volatization of the copper during heating.

Aluminum↗

PubMed2006

Role of geographic information system (GIS) in watershed simulation by WinVAST model.

The uncertainty of modeling input will increase the simulation error, and this situation always happens in a model without user-friendly interface. WinVAST model, developed by the University of Virginia in 2003, treats an entire multi-catchment by a tree-view structure. Its extra computer programs can connect geographic information system (GIS). Model users can prepare all the necessary information in ArcGIS. Extracting information from GIS interface can not only decrease the inconvenience of data input, but also lower the uncertainty due to data preparation. The Daiyuku Creek and Qupoliao Creek in the Fei-tsui reservoir watershed in Northern Taiwan provided the setting for the case study reported herein. The required information, including slope, stream length, subbasin area, soil type and land-use condition, for WinVAST model should be prepared in a Microsoft Access database, which is the project file of WinVAST with extension mdb. In ArcGIS interface, when the soil layer, land-use layer, and Digital Elevation Model (DEM) map are prepared, all the watershed information can be created as well. This study compared the simulation results from automatically generated input and manual input. The results show that the relative simulation error resulting from the rough process of data input can be around 30% in runoff simulation, and even reach 70% in non-point source pollution (NPSP) simulation. It could conclude that GIS technology is significant for predicting watershed responses by WinVAST model, because it can efficiently reduce the uncertainty induced by input errors.

Computer Simulation↗

PubMed2006

Exploring the interparticle electron transfer process in the photocatalytic oxidation of 4-chlorophenol.

This work aimed to investigate the interparticle electron transfer (IPET) process within the coupled-photocatalyst systems on the basis of the degradation of 4-chlorophenol (4-CP). TiO(2), ZnO and SnO(2) are used as the model photocatalysts owing to their increasing energy levels which correspond to the IPET concept. In the single-photocatalyst tests, ZnO tests are associated with the highest degradation rate constants (0.347+/-0.083 h(-1) at pH 7 and 0.453+/-0.011 h(-1) at pH 11) and a better DOC reduction than in other single catalyst tests under given conditions. ZnO/SnO(2) coupled tests have constants of 0.612+/-0.068 and 0.948+/-0.069 h(-1) at pH 7 and 11, respectively. Additionally, the 4-CP prefers the breakdown of chloride group in TiO(2) system while proceeding hydroxylation reaction in ZnO systems. Meanwhile, a phenomenonlogical model coupled with the IPET effect was developed to explore the separation of photo-electrons and photo-holes within catalysts. Based on the model parameters, the recombination rate of photo-electrons and photo-holes in TiO(2)/SnO(2) and ZnO/SnO(2) systems is 20-45% lower than that obtained by a respective single catalyst. Thus, coupled-photocatalyst tests, TiO(2)/SnO(2) and ZnO/SnO(2) efficiently suppress the recombination, particularly for ZnO/SnO(2) tests at pH 11.

Catalysis↗

PubMed2006

Adsorption of copper ions onto microwave stabilized heavy metal sludge.

Microwave stabilized heavy metal sludge was used as an adsorbent to remove the copper ions from aqueous solution. The adsorption characteristics of copper on the stabilized-sludge were studied by various models, such as Freundlich and Langmuir isotherm equation. Results show that the pH(zpc) of stabilized-sludge was at 9.2-9.5. Moreover, the adsorption of copper ions onto the stabilized-sludge surface was mainly on account of the heterogeneous surface of the stabilized-sludge. In the dynamic study, the experimental data was fitted to the intraparticle diffusion model, pseudo-first order model and pseudo-second order model. However, the experimental data was only well correlated with pseudo-second order model with the correlation coefficient>0.995. Furthermore, both Freundlich and Langmuir isotherm equations were found to represent the measured adsorption data well. From the Langmuir equation, the adsorption capacity increased from 18 to 28 mg/g as the temperature rose from 15 to 55 degrees C, since this adsorption process was an endothermic reaction. After this adsorption process, copper ions can be concentrated on and in a small bead and recovery efficiently.

Adsorption↗

PubMed2006

The parameter optimization in the inverse distance method by genetic algorithm for estimating precipitation.

The inverse distance method, one of the commonly used methods for analyzing spatial variation of rainfall, is flexible if the order of distances in the method is adjustable. By applying the genetic algorithm (GA), the optimal order of distances can be found to minimize the difference between estimated and measured precipitation data. A case study of the Feitsui reservoir watershed in Taiwan is described in the present paper. The results show that the variability of the order of distances is small when the topography of rainfall stations is uniform. Moreover, when rainfall characteristic is uniform, the horizontal distance between rainfall stations and interpolated locations is the major factor influencing the order of distances. The results also verify that the variable-order inverse distance method is more suitable than the arithmetic average method and the Thiessen Polygons method in describing the spatial variation of rainfall. The efficiency and reliability of hydrologic modeling and hence of general water resource management can be significantly improved by more accurate rainfall data interpolated by the variable-order inverse distance method.

Algorithms↗

PubMed2005

Stabilization of Cu in acid-extracted industrial sludge using a microwave process.

The leaching concentration of copper ions from the industrial sludge that has been extracted using sulfuric acid may still exceed 15 mg/L, which is the leaching standard of the toxicity characteristic leaching procedure (TCLP) for hazardous waste in Taiwan. Therefore, the acid-extracted industrial sludge is still an important source of hazardous waste. Usually, hazardous waste in Taiwan must be solidified and passed through the TCLP test before it is disposed in a landfill. The aim of this study is to develop a microwave process to stabilize copper ions in the sludge to replace the use of traditional solidification. In this study, two parameters--the reaction time of the microwave process and the additive reagents--were considered. The efficiency of stabilization of the microwave process was evaluated from the result of the TCLP test. The results showed that the stabilization efficiency of copper ions obtained using a microwave process without any added reagent depends highly on the property of the original acid-extracted sludge. Under some conditions, the leaching concentrations were much lower than those of the raw sludge. In additive reagent systems, the results showed that iron powder promoted the stabilization of copper ions more than the other additives such as sodium carbonate and sodium silicate. The leaching concentration of copper ions decreased dramatically from 179.4 to 6.5mg/L below in the iron additive system.

Acids↗

PubMed2005

Effects of iron surface pretreatment on kinetics of aqueous nitrate reduction.

Using hydrogen gas at 400 degrees C to activate iron surface was proposed to remove nitrate (40 mg NL(-1)) in a HEPES buffer solution at pH value between 6.5 and 7.5. Compared with the nonpretreated iron, the first-order reaction rate constant (kobs) was increased 4.7 times by pretreated iron, and the lag of the early period disappeared. Normalized to iron surface area concentration, the specific rate constant (kSA) was increased approximately by a factor of 6 using hydrogen reduction (0.0020 min(-1)m(-2)L for nonpretreated iron and 0.0128 min(-1)m(-2)L for pretreated iron). The reactivity of aged iron covered by a complex mixture of iron oxides (soaking in nitrate solution for 60 days) were restored by hydrogen gas at 400 degrees C. Scanning electron microscopy (SEM) and temperature-programmed reduction (TPR) exhibited visibly cleaner without pitting and cracking and less oxygen fraction on pretreated iron surface relative to nonpretreated iron. Activation energies (Ea) of nitrate reduction over the temperature range of 10-45 degrees C were 46.0 kJ mol(-1) for nonpretreated iron, and 32.0 kJ mol(-1) for pretreated iron, indicating chemical reaction control, rather than diffusion. The results indicated that this enhancement was attributed to the increase in active site concentration on iron surface by hydrogen reduction.

Hydrogen↗

PubMed2005

Chemical reduction of an unbuffered nitrate solution using catalyzed and uncatalyzed nanoscale iron particles.

Uncatalyzed and catalyzed nanoscale Fe(0) systems were employed for the denitrification of unbuffered 40 mgN L(-1) nitrate solutions at initial neutral pH. Compared to microscale Fe(0) (<100 mesh), the efficiency and rate of nitrate removal using uncatalyzed and catalyzed nano-Fe(0) were highly promoted, in which the maximum promoted rate was obtained using copper-catalyzed nano-Fe(0) (nano-Cu/Fe). Nitrate first-order degradation rate constants (k(obs)) decreased significantly (>70%) with aged nano-Fe(0) and aged nano-Cu/Fe, and were recovered with NaBH(4) as reductants at levels of about 85 and 75%, respectively. Activation energies (E(a)) of nitrate reduction over the temperature range of 10-60 degrees C were 42.5 kJ mol(-1) for microscale Fe(0), 25.8 kJ mol(-1) for nano-Fe(0) and 16.8 kJ mol(-1) for nano-Cu/Fe. Unlike microscale Fe(0), the kinetics of denitrification by nano-Fe(0) and nano-Cu/Fe began to show characteristics of mass transport in addition to chemical reaction control. Ammonium was the predominant end product in all the systems. However, as for nitrite, 40% of the degraded nitrate persisted in the nano-Cu/Fe system. Thus, relative to nano-Cu/Fe, nano-Fe(0) is a potential reductant for denitrification of groundwater as far as toxic nitrite generation is concern.

Adsorption↗

PubMed2005

Removal of copper from industrial sludge by traditional and microwave acid extraction.

This work elucidates the removal of copper from industrial sludge by traditional and microwave acid extraction. The effects of acid concentration, extraction time, sludge particle size and solid/liquid (S/L) ratio on copper removal efficiency were evaluated. Leaching with more concentrated acid yielded greater copper content from the industrial sludge. The experimental findings reveal that the most economical traditional extraction conditions were the use of 1N sulfuric or nitric acid for 60 min at an S/L ratio of 1/20; however, at an S/L ratio of 1/6, the extraction time needed to achieve the same copper removal efficiency was increased to 36 h. Increasing the microwave power and reducing the S/L ratio increased the copper extraction efficiency and the effect in the larger S/L ratio system was more significant. A comparison of the results of microwave-assisted (microwave only) and microwave-enhanced (microwave with addition of active carbon) acid extraction demonstrated that under both conditions, S/L ratio=1/6 and 1/20; adding active carbon shortened the extraction time required to achieve 80% copper extraction efficiency from 20 to 10 min. These experimental results indicate that the most important factors that most strongly affected microwave acid extraction were the addition of a microwave absorber, the microwave power input and the S/L ratio. The sludge particle size did not significantly affect the copper extraction. The results reveal that sulfuric acid was an effective extractant and that the copper fraction in the extracted sludge shifted from being mostly bound to the Fe-Mn oxides and organic matter, to being mostly bound to organic matter and remaining as a residue during acid extraction.

Acids↗

PubMed2005

A fuzzy index model for trophic status evaluation of reservoir waters.

An index model for quality evaluation based on the formula of similarity membership functions in the fuzzy c-means (FCM) clustering algorithm is proposed. Summing up the weighted similarity degrees between an observation and designed specific quality-ordered levels develops an alternative overall index. Stretching the values of the controlling parameters in the formula of the similarity membership functions causes diverse patterns of overall index models. Applying this proposed fuzzy index model to the trophic evaluation of reservoir waters is studied to demonstrate the practical application of this index. Every measurement of the variables is standardized by the membership function of quality evaluation on the interval [0,1], referring to the trophic status clarified in the Carlson Trophic State Index. The sensitivity analyses are studied both in the proposed index system and the Carlson Trophic State Index. Besides, a case study of the trophic status evaluation of the Feitsui Reservoir from 1987 to 2003 is presented to demonstrate the feasibility of applying the proposed evaluation model.

Chlorophyll↗

PubMed2005

Quantifying and reducing uncertainty in life cycle assessment using the Bayesian Monte Carlo method.

The traditional life cycle assessment (LCA) does not perform quantitative uncertainty analysis. However, without characterizing the associated uncertainty, the reliability of assessment results cannot be understood or ascertained. In this study, the Bayesian method, in combination with the Monte Carlo technique, is used to quantify and update the uncertainty in LCA results. A case study of applying the method to comparison of alternative waste treatment options in terms of global warming potential due to greenhouse gas emissions is presented. In the case study, the prior distributions of the parameters used for estimating emission inventory and environmental impact in LCA were based on the expert judgment from the intergovernmental panel on climate change (IPCC) guideline and were subsequently updated using the likelihood distributions resulting from both national statistic and site-specific data. The posterior uncertainty distribution of the LCA results was generated using Monte Carlo simulations with posterior parameter probability distributions. The results indicated that the incorporation of quantitative uncertainty analysis into LCA revealed more information than the deterministic LCA method, and the resulting decision may thus be different. In addition, in combination with the Monte Carlo simulation, calculations of correlation coefficients facilitated the identification of important parameters that had major influence to LCA results. Finally, by using national statistic data and site-specific information to update the prior uncertainty distribution, the resultant uncertainty associated with the LCA results could be reduced. A better informed decision can therefore be made based on the clearer and more complete comparison of options.

Bayes Theorem↗

PubMed2005

Degradation of aqueous carbon tetrachloride by nanoscale zerovalent copper on a cation resin.

Nanoscale zerovalent copper supported on a cation resin was successfully synthesized to enhance the removal of carbon tetrachloride (CCl(4)) from contaminated water. The use of the cation resin as a support prevents the reduction of surface area due to agglomeration of nanoscale zerovalent copper particles. Moreover, the cation resin recycles the copper ions resulting from the reaction between CCl(4) and Cu(0) by simultaneous ion exchange. The decline in the amount of CCl(4) in aqueous solution results from the combined effects of degradation by nanoscale zerovalent copper and sorption by the cation resin; thus the amount of CCl(4) both in aqueous solution and sorbed onto the resin were measured. The pseudo-first-order rate constant normalized by the surface-area and the mass concentration of nanoscale zerovalent copper (k(SA)) was 2.1+/-0.1 x 10(-2)lh(-1)m(-2), approximately twenty times that of commercial powdered zerovalent copper (0.04 mm). Due to the exchange between Cu(2+) and the strongly acidic ions (H(+) or Na(+)), the pH was between 3 and 4 in unbuffered solution and Cu(2+) at the concentration of less than 0.1 mg l(-1) was measured after the dechlorination reaction. In the above-ground application, resin as a support would facilitate the development of a process that could be designed for convenient emplacement and regeneration of porous reductive medium.

Adsorption↗