The ROH,UV concept to characterize and the model uv/H202 process in natural waters

A new concept is introduced to characterize and model the UV/H2O2 advanced oxidation process (AOP) in water. Similarto the Rct concept used to describe OH radical exposure per ozone dose, the ROH,UV concept is defined as the experimentally determined *OH radical exposure per UV fluence. ROH,UV was determined by examining the destruction of a probe compound, para-chlorobenzoic acid in four different waters: DI water and three natural waters. ROH,UV was found to be affected greatly by water quality, specifically background *OH radical scavenging, which competed forthe formed *OH radical with the probe compound, and background UV absorbance, which screened UV irradiation from the hydrogen peroxide. The ROH,UV values determined in the experiments using low-pressure Hg lamp were greater than those for the medium-pressure Hg lamp . Finally, the ROH,UV concept was utilized to calculate an overall scavenging factor for each water matrix, and this was successfully utilized in conjunction with the steady-state *OH radical model to improve the prediction of the oxidation of endocrine-disrupting compounds 17-alpha-ethinyl estradiol and 17-beta-estradiol in the natural waters.     

Estimates of increased black carbon emissions from electrostatic precipitators during powdered activated carbon injection for mercury emissions control

The behavior of mercury sorbents within electrostatic precipitators (ESPs) is not well-understood, despite a decade or more of full-scale testing. Recent laboratory results suggest that powdered activated carbon exhibits somewhat different collection behavior than fly ash in an ESP and particulate filters located at the outlet of ESPs have shown evidence of powdered activated carbon penetration during full-scale tests of sorbent injection for mercury emissions control. The present analysis considers a range of assumed differential ESP collection efficiencies for powdered activated carbon as compared to fly ash. Estimated emission rates of submicrometer powdered activated carbon are compared to estimated emission rates of particulate carbon on submicrometer fly ash, each corresponding to its respective collection efficiency. To the extent that any emitted powdered activated carbon exhibits size and optical characteristics similar to black carbon, such emissions could effectively constitute an increase in black carbon emissions from coal-based stationary power generation. The results reveal that even for the low injection rates associated with chemically impregnated carbons, submicrometer particulate carbon emissions can easily double if the submicrometer fraction of the native fly ash has a low carbon content. Increasing sorbent injection rates, larger collection efficiency differentials as compared to fly ash, and decreasing sorbent particle size all lead to increases in the estimated submicrometer particulate carbon emissions.     

Single-particle SEM-EDX analysis of iron-containing coarse particulate matter in an urban environment: sources and distribution of iron within Cleveland, Ohio

The physicochemical properties of coarse-mode, iron-containing particles and their temporal and spatial distributions are poorly understood. Single-particle analysis combining X-ray elemental mapping and computer-controlled scanning electron microscopy (CCSEM-EDX) of passively collected particles was used to investigate the physicochemical properties of iron-containing particles in Cleveland, OH, in summer 2008 (Aug-Sept), summer 2009 (July-Aug), and winter 2010 (Feb-March). The most abundant classes of iron-containing particles were iron oxide fly ash, mineral dust, NaCl-containing agglomerates (likely from road salt), and Ca-S containing agglomerates (likely from slag, a byproduct of steel production, or gypsum in road salt). The mass concentrations of anthropogenic fly ash particles were highest in the Flats region (downtown) and decreased with distance away from this region. The concentrations of fly ash in the Flats region were consistent with interannual changes in steel production. These particles were observed to be highly spherical in the Flats region, but less so after transport away from downtown. This change in morphology may be attributed to atmospheric processing. Overall, this work demonstrates that the method of passive collection with single-particle analysis by electron microscopy is a powerful tool to study spatial and temporal gradients in components of coarse particles. These gradients may correlate with human health effects associated with exposure to coarse-mode particulate matter.     

Quantifying hazardous species in particulate matter derived from fossil-fuel combustion

An analysis protocol that combines X-ray absorption near-edge structure spectroscopy with selective leaching has been developed to examine hazardous species in size-segregated particulate matter (PM) samples derived from the combustion of fossil fuels. The protocol has been used to identify and determine quantitatively the amounts of three important toxic species in combustion-derived PM: viz., nickel sulfides in residual oil fly ash (ROFA) PM, and Cr(VI) and As(III) species in coal fly ash PM. Although it has been assumed that these toxic species might exist in PM derived from fossil-fuel combustion, the results presented here constitute the first direct determination of them in combustion-derived PM and their potential bioavailability. Detailed information on the presence of these toxic species in PM samples is of significant interest to epidemiological and toxicological studies of the health effects of both source and ambient PM. Additionally, information is obtained on insoluble forms that may be useful for source attribution and on the distribution of phases between size fractions that may be related to formation mechanisms of specific toxic species during combustion.     

Nitration of benzo[a]pyrene adsorbed on coal fly ash particles by nitrogen dioxide: role of thermal activation

Nitration of benzo[a]pyrene (BaP) by nitrogen dioxide (NO2) adsorbed on the surface of thermally activated coal fly ash and model aluminosilicate particles led to the formation of nitrobenzo[a]pyrenes as verified by extraction and gas chromatography/mass spectrometry (GC/MS). In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was utilized to follow the nitration reaction on the surface of zeolite Y. Nitrobenzo[a]pyrene formation was observed along with the formation of nitrous acid and nitrate species. The formation of the BaP radical cation was also observed on thermally activated aluminosilicate particles by electron spin resonance (ESR) spectroscopy. On the basis of GC/MS, DRIFTS, and ESR spectroscopy results, a mechanism of nitration involving intermediate BaP radical cations generated on thermally activated aluminosilicate particles is proposed. These observations have led to the hypothesis that nitration of adsorbed polyaromatic hydrocarbons on coal fly ash by reaction with nitrogen oxides can occur in the smokestack, but with the aging of the fly ash particles, the extent of the nitration reaction will be diminished.     

Emission characteristics of heavy metals and their behavior during coking processes

Besides organic pollutants, coke production generates emissions of toxic heavy metals. However, intensive studies on heavy metal emissions from the coking industry are still very scarce. The current work focuses on assessing the emission characteristics of heavy metals and their behavior during coking. Simultaneous sampling of coal, coke, residues from air pollution control devices (APCD), effluent from coke quenching, and fly ash from different processes before and after APCD has been performed. The total heavy metal concentration in the flue gas from coke pushing (CP) was significantly higher than that from coal charging (CC) and combustion of coke oven gases (CG). Emission factors of heavy metals for CP and CC were 378.692 and 42.783 μg/kg, respectively. During coking, the heavy metals that were contained in the feedstock coal showed different partitioning patterns. For example, Cu, Zn, As, Pb, and Cr were obviously concentrated in the inlet fly ash compared to the coke; among these metals Cu, As, and Cr were concentrated in the outlet fly ash, whereas Zn and Pb were distributed equally between the outlet fly ash and APCD residue. Ni, Co, Cd, Fe, and V were partitioned equally between the inlet fly ash and the coke. Understanding the behavior of heavy metals during coking processes is helpful for the effective control of these heavy metals and the assessment of the potential impact of their emissions on the environment.     

Effect of aluminosilicate powders on the applicability of innovative geopolymer binders for wood-based composites

In this research, a new binder class for wood based composites, named geopolymer binder, was developed based on pozzolanic by-products (e.g. fly ash). Additionally, effects of different amounts of silica fume, as a replacement agent with other aluminosilicate components (e.g. fly ash and metakaolin), have been evaluated in the innovative binder. The Automated Bonding Evaluation System technique was used to characterize the bonding shear strength of the developed geopolymer binder. It was shown that the best shear strength for fly ash based binders was obtained by the lowest press temperature and longest pressing time. The addition of silica fume (from 20% up to 100%) significantly influenced the bonding shear strength in all binder types. Due to the chemical and mineralogical compositions, silica fume displays higher pozzolanic activity than metakaolin whereas fly ash shows lower strength in comparison to metakaolin. The silica fume (100%) based binder has also superior shear strength compared to those of conventional UF resin and other geopolymer binders. Bonding shear strength like that for UF resin was achieved by substituting only 20% silica fume in geopolymer binder compositions.     

Carbon speciation of diesel exhaust and urban particulate matter NIST standard reference materials with C(1s) NEXAFS spectroscopy

The U.S. National Institute of Standards and Technology (NIST) provides a number of particulate matter (PM) standard reference materials (SRM) for use in environmental and toxicological methodology and research. We present here the first analysis with respect to the molecular structure of the carbon in three such NIST SRM samples, i.e., diesel engine exhaust soot from heavy duty equipment engines (SRM 1650), diesel soot from a forklift engine (SRM 2975), and urban PM collected in St. Louis, MO (SRM 1648), with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS spectra of the two diesel soot samples appear quite similar, while they differ significantly from the urban PM spectrum, in agreement with X-ray diffraction data published recently. Such comparison is made in terms of aromatic and aliphatic carbon species, as well as by a general comparison with graphitic materials. Both diesel soot SRM samples contain basic graphitic structures, but the presence of exciton resonance and extended X-ray absorption fine structure oscillations in SRM 1650 and the lack therof in SRM 2975 suggest that SRM 1650 is the more graphitic material.The presence of polycyclic aromatic hydrocarbons, which have a characteristic NEXAFS resonance at the same position as graphite, can obscure the graphitic character of soot, unless an extraction of the organic matter is made. Our NEXAFS data do not suggest that the urban PM sample SRM 1648 contains a substantial amount of graphite-like material.     

Dynamic change of copper in fly ash during de novo synthesis of dioxins

Although many researchers have reported that copper chloride is an important catalyst that generates relatively large amounts of dioxins in heat experiments involving model fly ash, details on the behavior of copper during the process are still unavailable. In this study, we used in situ XANES experiments involving one type of real fly ash, which originated from a municipal solid-waste incinerator (MSWI), and two fly ash models to investigate the behavior of copper in fly ash at temperatures that are suitable for de novo synthesis, which is the major formation route for dioxins during waste incineration and thermal processes. Cupric compounds in real fly ash and model fly ash A(CuCl2.2H2O + activated carbon (AC) + boron nitride (BN)) were reduced to cuprous compounds or elemental copper at low temperatures. The changes in the Cu XANES spectra of real fly ash were similar to those of model fly ash A and those of an oxychlorination catalyst. In model fly ash B (CuO + AC + KCl + BN), CuO did not vary dramatically in the temperature range studied. In this study, we found strong evidence that oxychlorination, the key mechanistic step in the formation of dioxins, occurred in both real MSWI and model fly ash.     

Application of solid ash based catalysts in heterogeneous catalysis

Solid wastes, fly ash, and bottom ash are generated from coal and biomass combustion. Fly ash is mainly composed of various metal oxides and possesses higher thermal stability. Utilization of fly ash for other industrial applications provides a cost-effective and environmentally friendly way of recycling this solid waste, significantly reducing its environmental effects. On the one hand, due to the higher stability of its major component, aluminosilicates, fly ash could be employed as catalyst support by impregnation of other active components for various reactions. On the other hand, other chemical compounds in fly ash such as Fe2O3 could also provide an active component making fly ash a catalyst for some reactions. In this paper, physicochemical properties of fly ash and its applications for heterogeneous catalysis as a catalyst support or catalyst in a variety of catalytic reactions were reviewed. Fly-ash-supported catalysts have shown good catalytic activities for H2 production, deSO(x), deNO(x), hydrocarbon oxidation,and hydrocracking, which are comparable to commercially used catalysts. As a catalyst itself, fly ash can also be effective for gas-phase oxidation of volatile organic compounds, aqueous-phase oxidation of organics, solid plastic pyrolysis, and solvent-free organic synthesis.     

Photolysis of aqueous H2O2: quantum yield and applications for polychromatic UV actinometry in photoreactors

Methanol is used to measure the yield of *OH radicals produced in the photolysis of H2O2 in aqueous solutions. The UV photolysis of H202 generates *OH radicals, which in the presence of methanol, oxygen, and phosphate buffer form formaldehyde, namely, phi(HCHO) = phi(*OH). The quantum yield of *OH has been redetermined in view of literature inconsistencies resulting in phi(*OH) = 1.11 +/- 0.07 in the excitation range of 205-280 nm. The constancy of phi(*OH) and the ease and sensitivity of the formaldehyde product analysis makes the H2O2/CH3OH system suitable for polychromatic UV actinometry. In addition, the relatively low cost of the main components and the possibility of destroying the methanol before disposal qualify the system for both monochromatic and polychromatic actinometry in a large volume of water. The H2O2/CH3OH system was applied in different commercial UV photoreactors.     

Removal of B,Cr, Mo,and Se from wastewater by incorporation into hydrocalumite and ettringite

Boron, chromium, molybdenum, and selenium often occur in high concentrations in fly ash leachates. During the leaching of fly ash in alkaline environments, hydrocalumite (Ca4Al2(OH)12(OH)2 x 6H2O) and ettringite (Ca6Al2(OH)12(SO4)3 x 26H20) form as secondary precipitates. In this study, the removal of B, Cr, Mo, and Se oxyanions from high pH waters by incorporation into hydrocalumite and ettringite was examined. Experiments were performed by precipitating these minerals in solutions containing B, Cr, Mo, and Se oxyanions at conditions relevant to lime-leaching of fly ash as well as to fly ash containing concrete. The uptake of all four anions by hydrocalumite and ettringite was high. Anion uptake by hydrocalumite was larger than that by ettringite, and hydrocalumite was able to reduce anion concentrations to below drinking water standards. Ettringite showed an anion preference in the order of B(OH)4- > SeO4(2-) > CrO4(2-) > MoO4(2-). In contrast, borate was least preferred by hydrocalumite. Coordination, size, and electronegativity are likely the factors that result in the observed differences among the oxyanions.     

Novel dry-desulfurization process using Ca(OH)2/fly ash sorbent in a circulating fluidized bed

A dry-desulfurization process using Ca(OH)2/fly ash sorbent and a circulating fluidized bed (CFB) was developed. Its aim was to achieve high SO2 removal efficiency without humidification and production of CaSO4 as the main byproduct. The CaSO4 produced could be used to treat alkalized soil. An 83% SO2 removal rate was demonstrated, and a byproduct with a high CaSO4 content was produced through baghouse ash. These results indicated that this process could remove SO2 in flue gas with a high efficiency under dry conditions and simultaneously produce soil amendment. It was shown that NO and NO2 enhanced the SO2 removal rate markedly and that NO2 increased the amount of CaSO4 in the final product more than NO. These results confirmed that the significant effects of NO and NO2 on the SO2 removal rate were due to chain reactions that occurred under favorable conditions. The amount of baghouse ash produced increased as the reaction progressed, indicating that discharge of unreacted Ca(OH)2 from the reactor was suppressed. Hence, unreacted Ca(OH)2 had a long residence time in the CFB, resulting in a high SO2 removal rate. It was also found that 350 degrees C is the optimum reaction temperature for dry desulfurization in the range tested (320-380 degrees C).     

Risk ranking of bioaccessible metals from fly ash dissolved in simulated lung and gut fluids

Power plant fly ash from two fuels, coal and a mixture of coal and shredded tires, were evaluated for trace metal solubility in simulated human lung and gut fluids (SLF and SGF, respectively) to estimate bioaccessibility. The proportion of bioaccessible to total metal ranged from zero (V) to 80% (Zn) for coal-derived ash in SLF and from 2 (Th) to 100% (Cu) for tire-derived fly ash in SGF. The tire-derived ash contained much more Zn. However, Zn ranked only 5th of the various toxic metals in SGF compared with international regulations for ingestion. On the basis of total concentrations, the metals closestto exceeding limits based on international regulations for inhalation were Cr, Pb, and Al. On dissolution in SLF, the most limiting metals were Pb, Cu, and Zn. For metals exposed to SGF there was no relative change in the top metal, Al, before and after dissolution but the second-ranked metal shifted from Pb to Ni. In most cases only a proportion of the total metal concentrations in either fly ash was soluble, and hence bioaccessible, in either biofluid. When considering the regulatory limits for inhalation of particulates, none of the metal concentrations measured were as hazardous as the fly ash particulates themselves. However, on the basis of the international ingestion regulations for Al, the maximum mass of fly ash that could be ingested is only 1 mg per day (10 mg based on bioaccessibility). It is possible that such a small mass could be consumed by exposed individuals or groups.     

Arsenic and selenium capture by fly ashes at low temperature

Arsenic and selenium compounds may be emitted to the environment during coal conversion processes, although some compounds are retained in the fly ashes, in different proportions depending on the characteristics of the ashes and process conditions. The possibility of optimizing the conditions to achieve better trace element retention appears to be an attractive, economical option for reducing toxic emissions. This approach requires a good knowledge of fly ash characteristics and a thorough understanding of the capture mechanism involved in the retention. In this work the ability of two fly ashes, one produced in pulverized coal combustion and the other in fluidized bed combustion, to retain arsenic and selenium compounds from the gas phase in coal combustion and coal gasification atmospheres was investigated. To explore the possible simultaneous retention of mercury, the influence of the unburned coal particle content was also evaluated. Retention capacities between 2 and 22 mg g(-1) were obtained under different conditions. The unburned coal particle content in the fly ash samples does not significantly modify retention capacities.     

甘草黄酮对大气细颗粒物PM2.5引起肺泡巨噬细胞损伤的保护作用

目的:研究甘草黄酮对大气细颗粒物PM2.5(SRM 2786)导致的大鼠肺泡巨噬细胞(NR8383)损伤的保护作用。方法:实验分为对照组、模型组(125 μg/mL SRM 2786)与不同浓度甘草黄酮给药组(3.125、6.25、12.5、25 μg/mL+125 μg/mL SRM 2786),药物作用24 h后分别用MTT法检测细胞存活率、细胞形态观察、酶联免疫法(Elisa)检测细胞上清液肿瘤坏死因子α(TNF-α)、白介素6(IL-6)及白介素1β(IL-1β)的含量、各组细胞NO和ROS释放及细胞中SOD活性和GSH-PX含量。结果:相较于对照组,125 μg/mL SRM 2786诱导可减少细胞贴璧生长且显著降低细胞存活率、SOD活性和GSH-PX含量、提高TNF-α、IL-6及IL-1β三种细胞因子的释放及细胞ROS和NO释放(p<0.01);而3.125~25 μg/mL甘草黄酮可使大部分悬浮细胞重新贴璧且显著提高下降的细胞存活率,显著抑制SRM 2786诱导的炎症细胞因子的释放和ROS释放、显著提高SOD活性及GSH-PX含量(p<0.05或 p<0.01),6.25~25 μg/mL甘草黄酮可显著降低SRM 2786导致的NO释放(p<0.05或p<0.01)。结论:甘草黄酮可显著提高由细颗粒物SRM 2786降低的细胞存活率和提高抗氧化酶活性、抑制炎性因子释放及氧化应激,其机制可能与其抗炎性损伤和氧化损伤有关。     

Reactions of hydroxyl radical with humic substances: bleaching, mineralization, and production of bioavailable carbon substrates

In this study, we examine the role of the hydroxyl (OH*) radical as a mechanism for the photodecomposition of chromophoric dissolved organic matter (CDOM) in sunlit surface waters. Using gamma-radiolysis of water, OH* was generated in solutions of standard humic substances in quantities comparable to those produced on time scales of days in sunlit surface waters. The second-order rate coefficients of OH* reaction with Suwannee River fulvic (SRFA; 2.7 x 10(4) s(-1) (mg of C/L)(-1)) and humic acids (SRHA; 1.9 x 10(4) s(-1) (mg of C/L)(-1)) are comparable to those observed for DOM in natural water samples and DOM isolates from other sources but decrease slightly with increasing OH* doses. OH* reactions with humic substances produced dissolved inorganic carbon (DIC) with a high efficiency of approximately 0.3 mol of CO2/mol of OH*. This efficiency stayed approximately constant from early phases of oxidation until complete mineralization of the DOM. Production rates of low molecular weight (LMW) acids including acetic, formic, malonic, and oxalic acids by reaction of SRFA and SRHA with OH* were measured using HPLC. Ratios of production rates of these acids to rates of DIC production for SRHA and for SRFA were similar to those observed upon photolysis of natural water samples. Bioassays indicated that OH* reactions with humic substances do not result in measurable formation of bioavailable carbon substrates other than the LMW acids. Bleaching of humic chromophores by OH* was relatively slow. Our results indicate that OH* reactions with humic substances are not likely to contribute significantly to observed rates of DOM photomineralization and LMW acid production in sunlit waters. They are also not likely to be a significant mechanism of photobleaching except in waters with very high OH* photoformation rates.     

De novo synthesis of polychlorinated dibenzo-p-dioxins and dibenzofurans on fly ash from a sintering process

Fly ash, collected in the electrostatic precipitator of a sinter plant in Belgium, has been examined and characterized in terms of its behavior with respect to thermal polychlorodibenzo-p-dioxins (PCDD) and polychlorodibenzofurans (PCDF) formation. Thermal experiments of the fly ash were conducted in a flow of air. The temperature was varied from 250 to 450 degrees C, and the reaction time varied from 30 min to 6 h. For comparison, the oxidative degradation of carbon in the fly ash was studied by differential scanning calorimetry (DSC) in the temperature range from 50 to 500 degrees C. Besides the known maximum of formation of PCDD/Fs around 325 degrees C generally found on experiments with incinerator fly ash, a second maximum of formation around 400 degrees C is observed on the sinter fly ash used in this study. DSC measurements on the fly ash show that the oxidative degradation of carbon appears at these two different temperatures confirming that the de novo synthesis on this kind of fly ash take place at two different optimum temperatures. About the reaction time, already after 30 min, an important quantity of PCDD/Fs is formed; the fast increase in PCDD/Fs amount is followed by a slower formation rate between 2 and 4 h. At longer reaction time, the formation slows down, and decomposition reactions become important. Analysis of homologue distribution indicates that the profile of PCDD/Fs is independent of the reaction time but that an increase of the temperature leads to a rise of lower chlorinated species. In all experiments, PCDF are formed preferentially (total PCDF/PCDD ratios larger than 5). The PCDF/PCDD ratio is clearly independent of the reaction time. Concerning the temperature, the apparently better stability of PCDF at high temperature (PCDF/PCDD ratio higher at high temperature) results in the fact of different PCDF/PCDD ratios for the different family and modifications of homologue distribution with the temperature. The isomer distribution shows little reaction time or temperature dependency, which is an argument in favor of a thermodynamic control of the isomer distribution during de novo formation of PCDD/Fs. Differences within the isomer distribution patterns of PCDD/Fs obtained from the laboratory de novo synthesis experiments and the original fly ash, reflecting the formation under the industrial process, suggest a different mechanism of formation in the sinter plant for the PCDD and PCDF. The de novo synthesis is sufficient to explain the PCDF formation in the real process, but synthesis from precursors must play a role for the PCDD formation.     

New processes in the environmental chemistry of nitrite: nitration of phenol upon nitrite photoinduced oxidation

The role of nitrite as an environmental factor has been widely recognized. Nitrite is a relevant source of *OH in the atmosphere, both in the gas phase via photolysis of gaseous HNO2 and in atmospheric hydrometeors by photolysis of NO2-. In aqueous systems, *OH production through nitrite photolysis can be negligible due to the competition for light absorption by dissolved Fe(III), colloidal iron oxides, and nitrate. These photoexcited oxidants interact with NO2- and HNO2 to form *NO2, either directly or via formation of *OH. As a consequence, nitrite and nitrous acid may act as *NO2 rather than *OH sources. The radical *NO2 is involved in the nitration of many aromatic compounds, of which phenol is a model in this work. Kinetic measurements using 2-propanol as *OH scavenger show that the direct production of *OH by aqueous Fe(III) species decreases as pH increases. At slightly acidic and neutral pH values, oxidation of nitrite occurs by direct electron transfer to photoexcited Fe(III)aq species or colloidal iron oxides, in addition to the *OH-mediated oxidation of NO2-. The reported findings suggest a completely new role of nitrite in aquatic environments.     

Continuous fractionation of fly ash particles by SPUTT for the investigation of PCDD/Fs levels in different sizes of insoluble particles

A combined analytical method has been developed to characterize the size dependent levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) contained in fly ash particles from a municipal solid waste incinerator (MSWI). Gravitational SPLITT fractionation (GSF), a relatively new technique for the fast and continuous separation of micron sized particles, was used to fractionate a fly ash sample, directly collected from a bag-filter house of MSWI in Korea, into six different size groups (<1.0, 1.0-2.5, 2.5-5.0, 5.0-10, 10-20, and 20-53 microm in diameter) in water solution, and the resulting fractions are examined by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) in order to determine the concentration of PCDD/Fs according to these particle sizes. The results from SPLITT fractionation show that approximately 54% of the fly ash particles (sieved fraction <53 microm) by weight have been found to be smaller than 5.0 microm excluding the water soluble matter in the sample. From the HRGC/HRMS measurements, particle fractions in the size range of PM 1.0-2.5 and 2.5-5.0 appear to carry about 76 and 79 ng/g of PCDD/Fs which are relatively larger than those found in other diameter ranges. Principal component analysis (PCA) shows that particles larger than 5.0 microm are clustered into a group predominantly containing low chlorinated dioxins and fractions smaller than 5.0 microm into another group with lower chlorinated furans. This study demonstrated that the combining GSF with a secondary analytical method such as HRGC/HRMS has the potential to obtain size dependent information of particulate materials in relation to their production processes, chemical compositions, environmental fates, and other factors.