Teflon-coated Glass Fiber Filters Research Articles

Evaluation of alternative filter media for particulate matter emission testing of residential wood heating devices

ABSTRACTThe performance of Teflon-coated glass fiber filter media (Pallflex Emfab TX40) is evaluated for particulate matter (PM) sampling of residential wood heating devices in a dilution tunnel. Thirty samples of varying duration and PM loading and concentration were collected from an U.S. Environmental Protection Agency (EPA) Method 28 dilution tunnel using dual Method 5G sample trains with untreated glass fiber and Emfab filters. Filters were weighed soon after the end of sampling and again the next day after equilibration at 35% relative humidity (RH). PM concentrations from both types of filters agreed very well with 1-day equilibration, demonstrating that Emfab filters are appropriate for use in measuring PM from residential wood burning appliances in a dilution tunnel and have performance equal to or better than the glass fiber filter media. Agreement between filter media without equilibration was erratic, with PM from glass fiber filter samples varying from slightly less than the Emfab samples to as much as 2.8 times higher. Some of the glass fiber filters lost substantial mass with equilibration, with the highest percent loss at lower filter mass loadings. Mass loss for Emfab samples was a small percentage of the mass and very consistent across the range of mass loadings. Taken together, these results may indicate water uptake on the glass fiber media that is readily removed with 1-day equilibration at moderate RH conditions.Implications: EPA regulations now allow the use of either glass fiber or Teflon filter media for wood appliance PM emission testing. Teflon filter media minimizes the potential for acid-gas PM artifacts on glass fiber filters; this is important as EPA moves toward the use of locally sourced cordwood for testing that may have higher sulfur content. This work demonstrates that the use of Teflon-coated glass fiber filters can give similar PM measurement results to glass fiber filters after 1 day of equilibration. With no equilibration, measured PM from glass fiber filters was usually higher than from Teflon-coated glass fiber filters.

Study of the PM Gas-Phase Filter Artifact Using a Setup for Mixing Diesel-Like Soot and Hydrocarbons

The filter artifact is a significant source of error in gravimetric measurements of particulate matter (PM) exhaust. However, only a few studies on the subject exist. Results from these studies show a large discrepancy mainly because the experiments were performed using real diesel vehicle exhaust with varying exhaust composition. In this study, a setup for mixing diesel-like soot and hydrocarbon vapor was constructed for generating a stable exhaust aerosol with adjustable composition. The particle size distribution of the diesel-fueled soot generator (GMD [geometric mean diameter] adjustable between 27 and 164 nm) was found to represent “real” exhaust particulate emission. This setup was applied for studying the filter artifact on Teflon-coated glass fiber filters using pentadecane as the hydrocarbon vapor. Experiments were performed using particle and hydrocarbon concentrations of 130–700 μg/m3 and 10–12 ppm, respectively. It was found that the particle concentration of the aerosol affects the filter ar...

Chemical speciation of PM emissions from heavy-duty diesel vehicles equipped with diesel particulate filter (DPF) and selective catalytic reduction (SCR) retrofits

Four heavy-duty diesel vehicles (HDDVs) in six retrofitted configurations (CRT ®, V-SCRT ®, Z-SCRT ®, Horizon, DPX and CCRT ®) and a baseline vehicle operating without after--treatment were tested under cruise (50 mph), transient UDDS and idle driving modes. As a continuation of the work by Biswas et al. [Biswas, S., Hu, S., Verma, V., Herner, J., Robertson, W.J., Ayala, A., Sioutas, C., 2008. Physical properties of particulate matter (PM) from late model heavy-duty diesel vehicles operating with advanced emission control technologies. Atmospheric Environment 42, 5622–5634.] on particle physical parameters, this paper focuses on PM chemical characteristics (Total carbon [TC], Elemental carbon [EC], Organic Carbon [OC], ions and water-soluble organic carbon [WSOC]) for cruise and UDDS cycles only. Size-resolved PM collected by MOUDI–Nano-MOUDI was analyzed for TC, EC and OC and ions (such as sulfate, nitrate, ammonium, potassium, sodium and phosphate), while Teflon coated glass fiber filters from a high volume sampler were extracted to determine WSOC. The introduction of retrofits reduced PM mass emissions over 90% in cruise and 95% in UDDS. Similarly, significant reductions in the emission of major chemical constituents (TC, OC and EC) were achieved. Sulfate dominated PM composition in vehicle configurations (V-SCRT ®-UDDS, Z-SCRT ®-Cruise, CRT ® and DPX) with considerable nucleation mode and TC was predominant for configurations with less (Z-SCRT ®-UDDS) or insignificant (CCRT ®, Horizon) nucleation. The transient operation increases EC emissions, consistent with its higher accumulation PM mode content. In general, solubility of organic carbon is higher (average ∼5 times) for retrofitted vehicles than the baseline vehicle. The retrofitted vehicles with catalyzed filters (DPX, CCRT ®) had decreased OC solubility (WSOC/OC: 8–25%) unlike those with uncatalyzed filters (SCRT ®s, Horizon; WSOC/OC ∼ 60–100%). Ammonium was present predominantly in the nucleation mode, indicating that ternary nucleation may be the responsible mechanism for formation of these particles.

Levels of selected metals in ambient air PM10 in an urban site of Zaragoza (Spain)

An assessment of the air quality of Zaragoza (Spain) was performed by determining the trace element content in airborne PM10 in a sampling campaign from July 2001 to July 2002. Samples were collected in a heavy traffic area with a high volume air sampler provided with a PM10 cutoff inlet. The levels of 16 elements (Al, Ba, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, V, and Zn) were quantified after collecting the PM10 on Teflon-coated glass fiber filters (GFF). Regarding the PM10, 32% exceedance of the proposed PM10 daily limit was obtained, some of them corresponding to summer and autumn periods. The limit values of toxic trace elements from US-EPA, WHO, and EC were not exceeded, considering Zaragoza as a moderately polluted city under the current air quality guidelines. The contribution of anthropogenic sources to atmospheric elemental levels was reflected by the high values of enrichment factors for Zn, Pb, and Cu compared to the average crustal composition. Statistical analyses also determined the contribution of different sources to the PM10, finding that vehicle traffic and anthropogenic emissions related to combustion and industrial processes were the main pollutant sources as well as natural sources associated with transport of dust from Africa for specific dates. Regarding the influence of meteorological conditions on PM10 and trace elements concentrations, it was found that calm weather conditions with low wind speed favor the PM10 collection and the pollution for trace elements, suggesting the influence of local sources.

New Method for Time-Resolved Diesel Engine Exhaust Particle Mass Measurement

The Dekati mass monitor (DMM; Dekati Ltd., Finland), a relatively new real-time mass measurement instrument, was investigated in this project. In contrast to the existing gravimetric filter method also used as a standard for regulation purposes, this instrument provides second-by-second data on mass concentration in the engine exhaust gas. The principle of the DMM is based on particle charging, inertial and electrical size classification, and electrical detection of aerosol particles. This study focuses on the instrument's practical performance. Details on calibration and the theory of operation will be published elsewhere. The exhaust emissions of two heavy-duty engines complying with the Euro III emission standard were measured on a dynamic engine test bench. We looked atthe particle number and mass emissions of the engines in different transient test cycles and steady-state conditions. The ability to follow transient test cycles and the response times of the DMM were investigated. The aerosol mass concentration measured by the DMM was compared with the mass concentration obtained by the standard gravimetric filter method with Teflon-coated glass fiber filters. The total mass concentration (integral over the whole cycle) measured by the DMM is about 20% higher than that measured by the standard gravimetric filter method. The total mass concentration from the DMM was also compared with the volume concentration calculated from the electrical low-pressure impactor (ELPI) measurements. Correlations were made with other particle measuring systems. The DMM correlates very well with the particulate mass (R2 = 0.95) and exhibits good linearity and repeatability. The response time to a well-defined change in exhaust concentration was observed to be fast and stable. The DMM was able to follow transient test cycles and provides good results on a second-by-second basis. The instrument used in this study was still under development, and there is therefore no complete scientific background reference for the DMM. This study therefore focuses more on the measurements than on the scientific background. The measurements have shown thatthe DMM is an adequate instrument for measuring the mass concentration of engine exhaust, with results comparable to those from the standard gravimetric filter method. In addition, the DMM provides real-time second-by-second data of the mass concentration during transient test cycles.

An optimized method for the determination of volatile and semi-volatile aldehydes and ketones in ambient particulate matter

A method has been developed to measure aldehydes and ketones associated with atmospheric particles. Carbonyl compounds from particulate material collected on Teflon-coated glass-fiber filters were simultaneously extracted and derivatized with an appropriate 2,4-dinitrophenylhydrazine (2,4-DNPH) solution. The efficiency of this procedure utilizing various 2,4-DNPH concentrations and solvent compositions was studied for 13 carbonyl compounds of atmospheric importance. These include formaldehyde, acetaldehyde, acetone, dicarbonyls such as glyoxal and methylglyoxal, and biogenic carbonyls such as pinonaldehyde and nopinone. An extraction solution containing 3 × 10−2 M 2,4-DNPH, in 60% acetonitrile/40% water, and pH 3 was most efficient in extracting and derivatizing these aldehydes and ketones (83-100% recovery). Improved sample enrichment and 2,4-DNPH purification methods were developed that afforded detection limits of 0.009-5.6 ng m−3. The relative standard deviation for replicate analyses were 1.9-10.1%. Carbonyl compounds in ambient particulate samples were quantified during a recent field study. Median values for nine carbonyl species ranged from 0.01-33.9 ng m−3 during the study.

A closure study of aerosol mass concentration measurements: comparison of values obtained with filters and by direct measurements of mass distributions

We compare measurements of aerosol mass concentrations obtained gravimetrically using Teflon coated glass fiber filters and by integrating mass distributions measured with the differential mobility analyzer–aerosol particle mass analyzer (DMA–APM) technique (Aerosol Sci. Technol. 36 (2002) 227). The DMA–APM technique measures the distribution of particle mass as a function of mobility size for particles of arbitrary shape and composition (Relationship between particle mass and mobility, and between aerodynamic and mobility size distributions for diesel exhaust particles, Environ. Sci. Technol., 2003). Because DMA–APM measurements are made on particles suspended in the air, data are not affected by volatilization or adsorption that can affect the accuracy of the filter measurements. We show that the average ratio of the filter to DMA–APM mass concentrations for laboratory-generated dioctyl sebacate (DOS) and sodium chloride (NaCl) aerosols is 1.14±0.28, and they are well correlated ( R 2>0.97). For diesel exhaust aerosols from an engine operating at 75% load, the two techniques agreed well with the average ratio of 0.98±0.20. When the engine was operated at a low (10%) load, mass concentrations measured with the filter were 2.13±0.54 times higher than values measured with the DMA–APM. We believe that the higher filter loading may be due to the adsorption of condensable vapors, which are emitted at higher rates under low engine load conditions. Measurements in which the condensable organics were removed with a catalytic stripper show much better agreement between the filter and DMA–APM, which support the hypothesis that vapor adsorption leads to artificially high filter data for low-load measurements. We conclude that the DMA–APM technique can be used to evaluate the accuracy of filter samples that may be affected by sampling artifacts, and to measure mass distributions with high time resolution for sub-0.5 μm aerosols.

Gas/Particle Partition Measurements of PAH at Hazelrigg, U.K.

During September and October, 1998, the new Integrated Organic Gas and Particle Sampler (IOGAPS), was operated at Hazelrigg, UK, the field measurement station of the University of Lancaster. Gas/particle partition ratios of twenty-two 2–5 ring PAH were determined using both the IOGAPS (in which the gas phase is collected before the particle phase) and a low flow sampler which utilized the traditional filter-sorbent geometry. For compounds of intermediate volatility, less partitioning to the gas phase was observed when the denuder was used. The denuder (8- channel, 60 cm, 16.7 L min−1 air sampling rate) trapped small amounts of several non-volatile PAH. This result is consistent with particle diffusion losses of 5 to 10% for particles less than 0.05 μm under the flow conditions in the denuder. The 60-cm denuder was probably longer than necessary for the flow rate used. During the sampling, both glass fiber and Teflon-coated glass fiber filters were used. Without a denuder in front of a glass fiber filter, the fine particulate mass (PM 2.5) measurements showed a major positive bias that has been attributed to adsorption of gases by the filter. Teflon-coated glass fiber filters were not subject to this artifact problem, and equal masses were collected on filters from the denuded and non-denuded air flows.

Mass Concentrations of Respirable Particulate and Nicotine in Seven Smoker's Homes in Rural Area of Taiwan

This study examines smoker's impact on his indoor air quality and his relative exposure to respirable particulate and nicotine. The daily indoor/outdoor respirable particulate and nicotine concentrations of seven smoker's homes were concurrently measured over a week in a rural area of Taiwan in the summer and the winter. Personal exposures to respirable particulate and nicotine of sixteen members from these seven families were also measured. Respirable particulate samples were collected on PVC filters by personal pumps with cyclone (flow rate=1.9l/min). Nicotine samples were actively collected on the teflon coated glass fiber filters impregnated with sodium bisulfate, extracted by ammoniated heptane, and analyzed by the gas chromatographic method. Indoor respirable particulate concentrations (44 to 107µ/m^3) were higher than outdoor (27 to 92µ/m^3) in both the summer and winter. In summer, the nicotine concentrations averaged at 0.7±0.6µ/m^3 indoors and about 0.5±0.5µ/m^3 for personal exposure. In winter, the nicotine concentrations averaged 0.7±1.1µ/m^3 indoors and about 0.4±0.5µ/m^3 for personal exposure. From correlation analysis, the indoor respirable particulates appeared to be generated from outdoor road dust rather from environmental tobacco smoke.

Combustion aerosol water content and its effect on polycyclic aromatic hydrocarbon reactivity

A linear relationship was observed between particle water uptake and relative humidity for aerosol samples collected on Teflon coated glass fiber filters. Gasoline soot and wood smoke sample weight increases were three to five times greater than diesel soot weight increases at comparable relative humidities. Lower limit estimates of wood smoke water content at 90% relative humidity were in the 5–10% range. Based on these results polycyclic aromatic hydrocarbon photodegradation was investigated in liquid mixtures of actual wood smoke components with water content varied from 0 to 15%. Reaction rates of benz[a]anthracene and benzo[k]fluroanthene were significantly greater in methoxyphenol mixtures with 10% water content than in mixtures which did not contain water. Benzo[a]pyrene photodegradation was not significantly different. The results indicate that combustion particle water content increases with increasing relative humidity and that PAH photodegradation rates are likely to increase with increasing particle water content. This provides an explanation for previously described smog chamber studies in which a correlation between polycyclic aromatic hydrocarbon (PAH) decay in sunlight and water vapor concentration was reported.

Artifact formation of nitrated polycyclic aromatic hydrocarbons during diesel soot sampling on teflon coated glass fiber filters

Artifact formation of nitrated polycyclic aromatic hydrocarbons during diesel soot sampling on teflon coated glass fiber filters

Mutagenicity of Teflon-coated glass fiber filters: a potential problem and solutions

w Teflon-coated glass fiber filters, used in studies of airborne particulate matter, were tested for mutagenic activity with the Salmonella/mammalian-microsome (Ames) assay. Eight blank filters were simultaneously extracted with dichloromethane (DCM). Extracts were concentrated by rotary evaporation and a nitrogen purge and were solvent exchanged into dimethyl sulfoxide (Me2SO) for bioassay. Mutagenicity testing was performed on strain TA98, with and without metabolic activation. Findings indicated that both direct- and indirect-acting frameshift mutagens were present on the blank filters. Preextracting the filters with DCM reduced the activity associated with the filters; however, forced-air baking increased the mutagenic response. Interference caused by filter mutagenicity was shown to be inversely proportional to extraction efficiency and particle load, suggesting that the effect of filter mutagenicity on typical urban samples will be negligible. However, when particle yield is low, as for samples collected at rural or background sites, interference from filter mutagenicity may be significant, and results should be interpreted with caution.

Determination of occupational exposure to fabric brightener chemicals by HPLC.

Paired-ion reversed-phase liquid chromatography was applied to the problem of determining the exposure of chemical workers to aerosols of chemical intermediates in the production of fabric brighteners, specifically: 4,4'-diaminostilbene-2,2'-disulfonic acid, disodium salt (DAS), 4,4'-dinitrostilbene-2,2'-disulfonic acid, disodium salt (DNS), and paranitrotoluene sulfonic acid, sodium salt (PNTSA), which are all light-sensitive ionic compounds. Personal samples were collected on Teflon-coated glass fiber filters through which air was drawn at 1.7 Lpm. DAS, DNS and PNTSA were desorbed quantitatively in water from the filters. Tetrabutylammonium phosphate served as the ion-pairing reagent to these anions and was added to the eluent solutions. The samples were separated on an octadecylsilyl column with a methanol/water gradient. These three compounds eluted with good separation in 15 min. Monitoring absorbance of light at 254 nm, one can easily obtain detection limits of 2 micrograms/mL or less. Air concentrations of 0.02 mg/m3 were measured readily by personal sampling. Airborne exposures in this facility were found to range from nondetectable levels up to 60 micrograms/m3 DAS. A fixed high volume sampler collected between 0.2 and 2 micrograms/m3 each of DAS, DNS and PNTSA. The enclosure of the reactors and transport of materials in solution or as a slurry minimize exposure.

Chemical transformation of PAH on airborne particles by exposure to NO 2 during sampling: A comparison between two filter media

The influence of the filter media on the reactivity of polycyclic aromatic hydrocarbons (PAH) adsorbed on airborne particles, when exposed to nitrogen dioxide during sampling, has been studied. This paper describes an experiment with Teflon-coated glass fiber filters (Pallflex). The results indicate that the degradation of PAH and the formation of mononitro derivatives and mutagenic compounds due to NO 2 exposure is not affected by the filter media, since no significant difference compared with glass fiber filter sampling was obtained.

Filtration of diesel particles

Pressure drops and collection efficiency have been determined for two Teflon-coated glass fiber filters: Pallflex T60A20 and TX40HI20-WW, and two Teflon membrane filters: Ghia Zefluor 2.0 and 3.0 μm pore size. The T60A20 filter gave the lowest pressure drops but had a clean filter collection efficiency of less than 80%. This efficiency rose quickly as the filter loaded, exceeding 95% for loadings greater than 0.03 mg cm −2. The other filters tested had efficiencies greater than 94% for all of the conditions tested, but had significantly higher pressure drops. The pressure drop produced by the collected particles was examined in some detail. The pressure drop divided by the product of face velocity and mass loading was found to be a constant which depended upon particle size and collection conditions. A relationship between this normalized pressure drop and particle size has been established. It may be used to estimate the mass mean diameter of diesel or diesel-like particles from relatively simple pressure drop measurements.

Solvents and Techniques For The Extraction Of Polynuclear Aromatic Hydrocarbons From Filter Samples Of Diesel Exhaust

Abstract The amounts of five polynuclear aromatic hydrocarbons-fluoranthene, pyrene, benzo(a)anthracene, benzo(k)fluoranthene, and benzo(a)pyrene-extracted by six solvents with four extraction techniques have been determined for diesel exhaust particulate collected on Teflon-coated glass fiber filters. Samples were analyzed by high pressure liquid chromatography with fluorescence detection. Toluene and methylene chloride gave higher recoveries than methanol, isopropanol, acetonitrile, and acetone for benzo(a)anthracene, benzo(k)fluoranthene, and benzo(a)pyrene. Soxhlet extraction for two hours (approximately 48 cycles) with toluene or acetonitrile was more effective than simple mechanical agitation, ultrasonic agitation for 15 minutes or immersion in refluxing ‘solvent’ for two hours.

Mouse skin tumor initiation-promotion and complete carcinogenesis bioassays: mechanisms and biological activities of emission samples.

Extracts of soots obtained from various sources were applied to the skin of mice in an effort to identify carcinogens in these mixtures and to link these materials to the etiology of human cancer. Samples of coal chimney soot, coke oven materials, industrial carbon black, oil shale soot, and gasoline vehicle exhaust materials have been examined by this method. The studies reported here have been constructed to compare the carcinogenic and tumorigenic potency of extracts from various particulate emissions: coke ovens, diesel and gasoline vehicles and a roofing tar pot. Automobile emission samples were obtained by collecting the diluted and cooled exhaust on Teflon-coated glass fiber filters. Coke oven and roofing tar samples were particulate emission samples collected by impaction and filtration. The organic components associated with each of the particles were extracted with dichloromethane and dermally applied to SENCAR mice. All agents were applied as tumor initiators by using a five-dose protocol. Selected extracts were also applied as complete carcinogens and as tumor promotors. Statistical analyses of the resulting tumor data were performed by using nonlinear Poisson and probit models. The results from these experiments provide a suitable data base for comparative potency estimation of complex mixtures.

Mouse Skin Tumor Initiation-Promotion and Complete Carcinogenesis Bioassays: Mechanisms and Biological Activities of Emission Samples

Extracts of soots obtained from various sources were applied to the skin of mice in an effort to identify carcinogens in these mixtures and to link these materials to the etiology of human cancer. Samples of coal chimney soot, coke oven materials, industrial carbon black, oil shale soot, and gasoline vehicle exhaust materials have been examined by this method. The studies reported here have been constructed to compare the carcinogenic and tumorigenic potency of extracts from various particulate emissions: coke ovens, diesel and gasoline vehicles and a roofing tar pot. Automobile emission samples were obtained by collecting the diluted and cooled exhaust on Teflon-coated glass fiber filters. Coke oven and roofing tar samples were particulate emission samples collected by impaction and filtration. The organic components associated with each of the particles were extracted with dichloromethane and dermally applied to SENCAR mice. All agents were applied as tumor initiators by using a five-dose protocol. Selected extracts were also applied as complete carcinogens and as tumor promotors. Statistical analyses of the resulting tumor data were performed by using nonlinear Poisson and probit models. The results from these experiments provide a suitable data base for comparative potency estimation of complex mixtures.