Multiple model approach to evaluation of accelerated carbonation for steelmaking slag in a slurry reactor.

Basic oxygen furnace slag (BOFS) exhibits highly alkaline properties due to its high calcium content, which is beneficial to carbonation reaction. In this study, accelerated carbonation of BOFS was evaluated under different reaction times, temperatures, and liquid-to-solid (L/S) ratios in a slurry reactor. CO2 mass balance within the slurry reactor was carried out to validate the technical feasibility of fixing gaseous CO2 into solid precipitates. After that, a multiple model approach, i.e., theoretical kinetics and empirical surface model, for carbonation reaction was presented to determine the maximal carbonation conversion of BOFS in a slurry reactor. On one hand, the reaction kinetics of BOFS carbonation was evaluated by the shrinking core model (SCM). Calcite (CaCO3) was identified as a reaction product through the scanning electronic microscopy and X-ray diffraction analyses, which provided the rationale of applying the SCM in this study. The rate-limiting step of carbonation was found to be ash-diffusion controlled, and the effective diffusivity for carbonation of BOFS in a slurry reactor were determined accordingly. On the other hand, the carbonation conversion of BOFS was predicted by the response surface methodology (RSM) via a nonlinear mathematical programming. According to the experimental data, the highest carbonation conversion of BOFS achieved was 57% under an L/S ratio of 20 mL g(-1), a CO2 flow rate of 0.1 L min(-1), and a pressure of 101.3 kPa at 50 °C for 120 min. Furthermore, the applications and limitations of SCM and RSM were examined and exemplified by the carbonation of steelmaking slags.

Validating carbonation parameters of alkaline solid wastes via integrated thermal analyses: Principles and applications.

Accelerated carbonation of alkaline solid wastes is an attractive method for CO2 capture and utilization. However, the evaluation criteria of CaCO3 content in solid wastes and the way to interpret thermal analysis profiles were found to be quite different among the literature. In this investigation, an integrated thermal analyses for determining carbonation parameters in basic oxygen furnace slag (BOFS) were proposed based on thermogravimetric (TG), derivative thermogravimetric (DTG), and differential scanning calorimetry (DSC) analyses. A modified method of TG-DTG interpretation was proposed by considering the consecutive weight loss of sample with 200-900°C because the decomposition of various hydrated compounds caused variances in estimates by using conventional methods of TG interpretation. Different quantities of reference CaCO3 standards, carbonated BOFS samples and synthetic CaCO3/BOFS mixtures were prepared for evaluating the data quality of the modified TG-DTG interpretation, in terms of precision and accuracy. The quantitative results of the modified TG-DTG method were also validated by DSC analysis. In addition, to confirm the TG-DTG results, the evolved gas analysis was performed by mass spectrometer and Fourier transform infrared spectroscopy for detection of the gaseous compounds released during heating. Furthermore, the decomposition kinetics and thermodynamics of CaCO3 in BOFS was evaluated using Arrhenius equation and Kissinger equation. The proposed integrated thermal analyses for determining CaCO3 content in alkaline wastes was precise and accurate, thereby enabling to effectively assess the CO2 capture capacity of alkaline wastes for mineral carbonation.

Adsorption of Selected Pharmaceutical Compounds onto Activated Carbon in Dilute Aqueous Solutions Exemplified by Acetaminophen, Diclofenac, and Sulfamethoxazole.

The adsorption of three pharmaceuticals, namely, acetaminophen, diclofenac, and sulfamethoxazole onto granular activated carbon (GAC), was investigated. To study competitive adsorption, both dynamic and steady-state adsorption experiments were conducted by careful selection of pharmaceuticals with various affinities and molecular size. The effective diffusion coefficient of the adsorbate was increased with decease in particle size of GAC. The adsorption affinity represented as Langmuir was consistent with the ranking of the octanol-water partition coefficient, K(ow). The adsorption behavior in binary or tertiary systems could be described by competition adsorption. In the binary system adsorption replacement occurred, under which the adsorbate with the smaller K(ow) was replaced by the one with larger K(ow). Results also indicated that portion of the micropores could be occupied only by the small target compound, but not the larger adsorbates. In multiple-component systems the competition adsorption might significantly be affected by the macropores and less by the meso- or micropores.

Accelerated carbonation using municipal solid waste incinerator bottom ash and cold-rolling wastewater: Performance evaluation and reaction kinetics.

Accelerated carbonation of alkaline wastes including municipal solid waste incinerator bottom ash (MSWI-BA) and the cold-rolling wastewater (CRW) was investigated for carbon dioxide (CO2) fixation under different operating conditions, i.e., reaction time, CO2 concentration, liquid-to-solid ratio, particle size, and CO2 flow rate. The MSWI-BA before and after carbonation process were analyzed by the thermogravimetry and differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The MSWI-BA exhibits a high carbonation conversion of 90.7%, corresponding to a CO2 fixation capacity of 102g perkg of ash. Meanwhile, the carbonation kinetics was evaluated by the shrinking core model. In addition, the effect of different operating parameters on carbonation conversion of MSWI-BA was statistically evaluated by response surface methodology (RSM) using experimental data to predict the maximum carbonation conversion. Furthermore, the amount of CO2 reduction and energy consumption for operating the proposed process in refuse incinerator were estimated. Capsule abstract: CO2 fixation process by alkaline wastes including bottom ash and cold-rolling wastewater was developed, which should be a viable method due to high conversion.

Systematic approach to determination of maximum achievable capture capacity via leaching and carbonation processes for alkaline steelmaking wastes in a rotating packed bed.

Accelerated carbonation of basic oxygen furnace slag (BOFS) coupled with cold-rolling wastewater (CRW) was performed in a rotating packed bed (RPB) as a promising process for both CO2 fixation and wastewater treatment. The maximum achievable capture capacity (MACC) via leaching and carbonation processes for BOFS in an RPB was systematically determined throughout this study. The leaching behavior of various metal ions from the BOFS into the CRW was investigated by a kinetic model. In addition, quantitative X-ray diffraction (QXRD) using the Rietveld method was carried out to determine the process chemistry of carbonation of BOFS with CRW in an RPB. According to the QXRD results, the major mineral phases reacting with CO2 in BOFS were Ca(OH)2, Ca2(HSiO4)(OH), CaSiO3, and Ca2Fe1.04Al0.986O5. Meanwhile, the carbonation product was identified as calcite according to the observations of SEM, XEDS, and mappings. Furthermore, the MACC of the lab-scale RPB process was determined by balancing the carbonation conversion and energy consumption. In that case, the overall energy consumption, including grinding, pumping, stirring, and rotating processes, was estimated to be 707 kWh/t-CO2. It was thus concluded that CO2 capture by accelerated carbonation of BOFS could be effectively and efficiently performed by coutilizing with CRW in an RPB.

Kinetic modeling on CO2 capture using basic oxygen furnace slag coupled with cold-rolling wastewater in a rotating packed bed.

In this study, direct and indirect carbonation of basic oxygen furnace slag (BOFS) coupled with cold-rolling wastewater (CRW) was carried out via a rotating packed bed (RPB). The solid products were qualitatively characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) and quantitatively analyzed with thermogravimetric analysis (TGA). The leachate was analyzed with inductively coupled plasma-optical emission spectroscopy (ICP-OES). The results indicate that the maximum achievable carbonation conversion (MACC) of BOFS was 90.7%, corresponding to a capture capacity of 0.277 g CO2/g of BOFS, by direct carbonation with CRW under a rotation speed of 750 rpm at 30 °C for 20 min. In addition, CO2 mass balance among the gas, liquid, and solid phases within an RPB was well-developed, with an error less than 10%, to confirm the actual CO2 capture capacity of BOFS with precision and accuracy. Furthermore, a reaction kinetic model based on mass balance was established to determine the reaction rate constant for various liquid agents (CRW and pure water). It was concluded that co-utilization of alkaline wastes including BOFS and CRW via the RPB is a novel approach for both enhancing CO2 capture capacity and reducing the environmental impacts of alkaline wastes.

Ex Situ CO2 capture by carbonation of steelmaking slag coupled with metalworking wastewater in a rotating packed bed.

Both basic oxygen furnace (BOF) slag and cold-rolling wastewater (CRW) exhibiting highly alkaline characteristics require stabilization and neutralization prior to utilization and/or final disposal. Using CO2 from flue gases as the stabilizing and neutralizing agents could also diminish CO2 emissions. In this investigation, ex situ hot stove gas containing 30 vol% CO2 in the steelmaking process was captured by accelerated carbonation of BOF slag coupled with CRW in a rotating packed bed (RPB). The developed RPB process exhibits superior results, with significant CO2 removal efficiency (η) of 96-99% in flue gas achieved within a short reaction time of 1 min at 25 °C and 1 atm. Calcite (CaCO3) was identified as the main product according to XRD and SEM-XEDS observations. In addition, the elimination of lime and Ca(OH)2 in the BOF slag during carbonation is beneficial to its further use as construction material. Consequently, the developed RPB process could capture the CO2 from the flue gas, neutralize the CRW, and demonstrate the utilization potential for BOF slag. It was also concluded that carbonation of BOF slag coupled with CRW in an RPB is a viable method for CO2 capture due to its higher mass transfer rate and CO2 removal efficiency in a short reaction time.

Occurrence and assessment of treatment efficiency of nonylphenol, octylphenol and bisphenol-A in drinking water in Taiwan.

Occurrence and methods for the removal of nonylphenolic compounds in drinking water have been gaining increased attention due to their widespread presence in natural water and the potential health risks from the consumptions of drinking water. The purpose of this study was to assess the occurrence of nonylphenol (NP), octylphenol (OP), and bisphenol-A (BPA) in water sources and treated water in Taiwan, to evaluate the treatment efficiencies of these compounds in both the conventional (coagulation, sedimentation, filtration and chlorination) and advanced treatment processes. The treatment efficiencies of these chemicals were assessed based on their concentrations in water sources, and the results were verified with laboratory simulated treatment processes. A survey of NP, OP, and BPA in 11 Taiwanese water sources showed that all of them could be identified in most of the sampled sources, and that higher concentrations of NP were found when the raw water was contaminated by domestic wastewater. However, higher treatment efficiency could be observed when the NP concentration in water source is high. Laboratory simulation studies of conventional treatment processes showed that chlorination played an important role in the degradation of NP in raw water. Treatment efficiencies of 60%-90% were achieved for NP removal when sufficient chlorine dosages were applied to satisfy chlorine demands. However, results also showed that conventional coagulation and rapid filtration processes were less effective in the reduction of phenolic compounds in water.

Accelerated carbonation of steelmaking slags in a high-gravity rotating packed bed.

Carbon dioxide (CO(2)) sequestration using the accelerated carbonation of basic oxygen furnace (BOF) slag in a high-gravity rotating packed bed (RPB) under various operational conditions was investigated. The effects of reaction time, reaction temperature, rotation speed and slurry flow rate on the CO(2) sequestration process were evaluated. The samples of reacted slurry were analyzed quantitatively using thermogravimetric analysis (TGA) and atomic absorption spectrometry (AAS) and qualitatively using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and transmission electron microscopy (TEM). The sequestration experiments were performed at a liquid-to-solid ratio of 20:1 with a flow rate of 2.5 L min(-1) of a pure CO(2) stream under atmospheric temperature and pressure. The results show that a maximum conversion of BOF slag was 93.5% at a reaction time of 30 min and a rotation speed of 750 rpm at 65°C. The experimental data were utilized to determine the rate-limiting mechanism based on the shrinking core model (SCM), which was validated by the observations of SEM and TEM. Accelerated carbonation in a RPB was confirmed to be a viable method due to its higher mass-transfer rate.

Identifying the rejection mechanism for nanofiltration membranes fouled by humic acid and calcium ions exemplified by acetaminophen, sulfamethoxazole, and triclosan.

This research investigated the fouling effect of humic acid and humic acid/calcium ions on the rejection of three target compounds, i.e., acetaminophen, sulfamethoxazole, and triclosan, by two nanofiltration (NF) membranes. A modified Hermia fouling model was used to describe the fouling process. The effects of solute and membrane characteristics on the rejection and flux decline at various pH levels and with various foulants were also investigated. Results show that fouling mechanisms include complete blocking and gel layer formation. The presence of humic acid and humic acid/calcium ions may positively influence the rejection of hydrophilic compounds and neutral compounds rejected only by size exclusion. The experimental rejections of solute by the NF270 membrane correlate well with the theoretical rejection model in which only size exclusion was considered. For NF membranes with pore sizes larger than the solutes (e.g., the NTR7450 membrane), the rejection could be determined from the model combining both size exclusion and electrostatic exclusion.

CO2 sequestration by carbonation of steelmaking slags in an autoclave reactor.

Carbon dioxide (CO(2)) sequestration experiments using the accelerated carbonation of three types of steelmaking slags, i.e., ultra-fine (UF) slag, fly-ash (FA) slag, and blended hydraulic slag cement (BHC), were performed in an autoclave reactor. The effects of reaction time, liquid-to-solid ratio (L/S), temperature, CO(2) pressure, and initial pH on CO(2) sequestration were evaluated. Two different CO(2) pressures were chosen: the normal condition (700 psig) and the supercritical condition (1300 psig). The carbonation conversion was determined quantitatively by using thermo-gravimetric analysis (TGA). The major factors that affected the conversion were reaction time (5 min to 12h) and temperature (40-160°C). The BHC was found to have the highest carbonation conversion of approximately 68%, corresponding to a capacity of 0.283 kg CO(2)/kg BHC, in 12h at 700 psig and 160°C. In addition, the carbonation products were confirmed to be mainly in CaCO(3), which was determined by using scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) to analyze samples before and after carbonation. Furthermore, reaction kinetics were expressed with a surface coverage model, and the carbon footprint of the developed technology in this investigation was calculated by a life cycle assessment (LCA).

Performance evaluation for carbonation of steel-making slags in a slurry reactor.

CO(2) sequestration by the aqueous carbonation of steel-making slag under various operational conditions was investigated in this study. The effects of the operational conditions, including type of steel-making slag, reaction time, reaction temperature, and CO(2) flow rate, on the performance of the carbonation process were evaluated. The results indicated that the BOF slag had the highest carbonation conversion, approximately 72%, at a reaction time of 1h, an operating pressure of 101 kPa and a temperature of 60°C due to its higher BET surface area of BOF slag compared to UF, FA, and BHC slags. The major factors affecting the carbonation conversion are reaction time and temperature. The reaction kinetics of the carbonation conversion can be expressed by the shrinking-core model. The measurements of the carbonated material by the SEM and XRD instruments provide evidence indicating the suitability of using the shrinking-core model in this investigation. Comparison of the results with other studies suggests that aqueous carbonation by slurry reactor is viable due to its higher mass transfer rate.

Characterization and application of Ti-containing mesoporous silica for dye removal with synergistic effect of coupled adsorption and photocatalytic oxidation.

Highly ordered mesoporous silica, Santa Barbara Amorphous-15 (SBA-15), and titanium-substituted mesoporous silica (TiSBA-15) materials were successfully synthesized, characterized, and evaluated. The textual and structural properties of the prepared materials with various titanium contents were characterized by inductively coupled plasma-mass spectrometer (ICP-MS), powder X-ray diffraction (XRD) patterns, nitrogen physisorption isotherms, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A limited content of titanium could be effectively substituted into the framework of SBA-15 without provoking structure change. The adsorptive performance was examined by methylene blue (MB) adsorbed on prepared materials. The isotherm models were analyzed to describe the adsorption behavior of prepared materials. The adsorption isotherms were well-fitted with Langmuir and Freundlich models in the simulation of the adsorption behavior of dyes. The SBA-15 and TiSBA-15 materials were found to be effective adsorbents for MB from aqueous solutions. The photodegradation of MB and total organic carbon (TOC) analysis on solid composites were used to evaluate the catalytical performance of Ti-containing mesoporous silica. The synergistic effect of adsorptive and photocatalytical ability of prepared TiSBA-15 was identified. The regeneration and cyclic performance were also proved. These results revealed that TiSBA-15 could be one effective alternative material for dye removal.

Health risk assessment of exposure to selected volatile organic compounds emitted from an integrated iron and steel plant.

Workplace air samples from sintering, cokemaking, and hot and cold forming processes in the integrated iron and steel industry were analyzed to determine their volatile organic compound (VOC) concentration. Sixteen VOC species including three paraffins (cyclohexane, n-hexane, methylcyclohexane), five chlorinated VOC species (trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, chlorobenzene, 1,4-dichlorobenzene), and eight aromatics (benzene, ethylbenzene, styrene, toluene, m,p-xylene, o-xylene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene) were selected to measure their noncancer risk for workers. Concentrations of toluene, xylene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, dichlorobenzene, and trichloroethylene were high in all four processes. Carbon tetrachloride and tetrachloroethylene concentrations were high in the hot and cold forming processes. The noncancer risk followed the increasing order: cokemaking > sintering > hot forming > cold forming. 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzene contributed 44% to 65% and 13% to 20% of noncancer risk, respectively, for the four processes. Benzene accounted for a high portion of the noncancer risk in cokemaking. The hazard index (HI: 17-108) of the average VOC concentrations suggests that health risks can be reduced by improving workplace air quality and protecting workers.

Modeling the formation and assessing the risk of disinfection by-products in water distribution systems.

The effect of water quality parameters and operation conditions of water treatment on the formation of trihalomethanes (THM) and haloacetic acids (HAA) in pilot-scale reactor and water distribution system were investigated. Results indicated that dissolved organic carbon and THM formation increased while the concentration of free chlorine decreased along the length of pipeline from the water treatment plant; but HAA formation showed no relationship with the pipeline length. THM concentration was predicted with hydraulic analytic software, namely WaterCAD. The predicted THM data were within +/-10% of measurements; HAA had a relatively high error of +/-16% due to complex bio-decomposition reactions occurred in the distribution system. Both the hazardous quotient and cancer risk of THM in the water distribution system of an advanced water treatment plant were much lower than those of a conventional water treatment plant; there was no significant difference in hazard quotient and cancer risk of HAA in the above two water distribution systems.

Evaluating and elucidating the formation of nitrogen-contained disinfection by-products during pre-ozonation and chlorination.

The effects of pre-ozonation on the formation of haloacetonitriles (HANs), trichloronitromethane (TCNM), and haloketones (HKs) during chlorination were evaluated. Ozone dose used in this study was 8.0, 10.0 and 25.0 mg O(3)/min. Results showed high UV(254) reduction (>80%) and relatively low dissolved organic carbon removal (40-70%) after ozonation, indicating that ozone might change significantly the chemical properties of natural organic matter presented in the raw water. Undesired ozonation by-products such as aldehydes and ketones were also formed during ozonation. At high ozone dose of 25.0 mg O(3)/min, the formation of dichloroacetonitrile and bromochloroacetonitrile were reduced significantly. Chlorination of the ozonated water formed high concentration of TCNM and HKs were 8-10 and 31-48 microg/L, respectively. It was also found that continuous hydrolysis at longer reaction time rapidly decreased the formation of HKs. Ozonation prior to chlorination practice exhibited a negative effect on TCNM and HKs reduction. A model based on the dissolved organic carbon and chlorine decay was developed not only for determining the reaction rate constants, e.g. formation and hydrolysis of HANs, HKs and TCNM, but also for interpreting the mechanisms of formation and hydrolysis for HANs, HKs and TCNM during the chlorination of natural organic matter.

Effects of pre-ozonation on the removal of THM precursors by coagulation.

Pre-ozonation in combination with enhanced coagulation was used to remove NOM from lake water as to control the formation of disinfection by-products, DBPs. The effect of the hydrophobicity/hydrophilicity nature of NOM on the performance of the combined pre-ozonation and coagulation process was studied. The hydrophilicity/hydrophobicity property of NOM was characterized in terms of mass distribution of the phydrophilic and the hydrophobilic fractions of NOM. The optimal condition for the combined pre-ozonation-coagulation was established: pH=ca. 9.0 and ozone dose=0.45 mg-O(3)/mg-DOC. Under the optimal condition, it was able to achieve approximately 60% of THMFP removal. In terms of THMPF, results also indicated that the distribution between the hydrophilic and the hydrophobic fractions of NOM was 57.3 and 98.7 microg-THMFP/mg-DOC, respectively. Ozonation alters the structures and characteristics of NOM thereby affecting the coagulation effectiveness. Pre-ozonation was effective in removing the hydrophobic NOM, with a decrease of THMFP by approximately 20% versus approximately 10% for the hydrophilic fraction. The dosage of coagulant also governed DOC removal. The removal of hydrophobic and hydrophilic NOM were in the range of 27-41 and 2.5-22.7%, respectively at alum dosage of 0.41-1.65 (in Al/DOC) and 0.41-1.65 (in Al/DOC) and ozone dose of 0.58-2.93, mg/mg respectively. The adsorption characteristics of the hydrophilic and the hydrophobic fractions of NOM on aluminum hydroxide (from coagulant alum) were studied. Results indicated that the modified Langmuir isotherm of competitive adsorption was able to describe the adsorption of NOM onto hydrous aluminum hydroxide formed during alum coagulation of the lake waters.

Reduction of natural organic matter by nanofiltration process.

The objectives of this investigation were to characterize natural organic matter (NOM) in Kin-men raw water, to evaluate the performance of the nanofiltration (NF) membrane process for NOM removal, and to determine the good engineering practice (GEP) of the NF 270 membrane filtration performance. Three different samples: (1) raw water collected from the Tai Lake in Kin-men, Taiwan; (2) ultrafiltration (UF) pre-treated water; and (3) sand filtration (SF) treated water after the coagulation and sedimentation processes were employed in this study. The hydrophobic component (58%) was the predominant NOM fraction, and the NOM molecular weight was distributed broadly, i.e., lower than 1 kDa (30%), 1-5 kDa (32%) and larger than 5 kDa (38%). Hydrophobic NOM easily accumulated on the NF membrane surface and resulted in flux decline. The SF-NF was the proposed treatment process because it can reduce the NOMs effectively with lower energy consumption than UF-NF. It was noted that the dissolved organic carbon (DOC) rejection ratio was not affected by changing cross-flow velocity. However, at lower cross-flow velocity (0.15 ms(-1)), the reduction of organic matter in water sample was higher than that at higher cross-flow velocity (0.30 ms(-1)). By integrating the experimental results, it was concluded that a transmembrane pressure of 690 kPa and a cross-flow velocity of 0.30 ms(-1) exhibited the GEP, yielding about 94% of both DOC and UV(254) reduction.

Separation and structure determination of nicardipine photoproducts by LC-ESI-MS.

A sample of 0.104 M nicardipine in methanol was photoirradiated with a Philips 400 W UV lamp for 3 h in a photochemical chamber. A total of four major photoproducts were found from the HPLC chromatogram. The same sample was used for taking LC-MS, while eight major photoproducts were observed and the structures elucidated by analyzing the CID patterns of their respective mass spectra. A reaction scheme of nicardipine is proposed that the photochemical reactions occur mainly via oxidation of 1,4-dihydropyridine moiety, following the stepwise photo-reduction of the m-nitro group and demethylation of the ester group at 5-position of the pyridine ring.

The effects of synoptical weather pattern and complex terrain on the formation of aerosol events in the Greater Taipei area.

The aerosol in the Taipei basin is difficult to transport outward under specific weather patterns owing to complex terrain blocking. In this study, seven weather patterns are identified from synoptic weather maps for aerosol events, which occurred from March 2002 to February 2005. Among the identified weather patterns, High Pressure Peripheral Circulation (HPPC), Warm area Ahead of a cold Front (WAF), TYPhoon (TYP), Pacific High Pressure system stretching westerly (PHP), Weak High Pressure system (WHP), and Weak Southern Wind (WSW) are related to terrain blocking. The remaining pattern is High Pressure system Pushing (HPP). The classification of the pollution origin of the air masses shows that 15% of event days were contributed by long-range transport (LRT), 20% by local pollution (LP), and 65% by LRT/LP mix. Terrain blocking causes aerosol accumulation from high atmospheric stability and weak winds occurring under HPPC, TYP, and PHP weather patterns when the Taipei basin is situated on the lee side of the Snow Mountains Chain (SMC). Terrain blocking also occurs when the Taipei basin is situated on the upwind of SMC and Mt. Da-Twen under WAF and WSW patterns. To study the variation of aerosol properties under the mixed influence of terrain and pollution origin, we conducted a field observation simultaneously at the urban, suburban, and background sites in the Greater Taipei area from April 14 to 23, 2004. Terrain blocking plays an important role in aerosol accumulation in the stagnant environment when the Taipei basin is on the lee side of SMC. On the other hand, the PM(2.5) sulfate level is stable with a fraction of 30% in PM(2.5) during the observation period at the urban (25%-33%) and background (25%-41%) sites. It indicates that background PM(2.5) sulfate is high on the West Pacific in winter.