Differences in the OC/EC Ratios that Characterize Ambient and Source Aerosols due to Thermal-Optical Analysis

Khan, Bernine; Hays, Michael D.; Geron, Chris; Jetter, James J.

doi:10.1080/02786826.2011.609194

Cited by 89 publications

(74 citation statements)

References 31 publications

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“…7,9,13,[16][17][18] The ratio of EC measurements from the IMPROVE method to those from NIOSH protocols is higher in the presence of more biomass burning and more secondary aerosols. 7,13,16 The Carbon measurements, morbidity associations measured EC concentration depends, in part, on the temperature protocol used in the analysis, with EC measurements typically being lower with higher peak inert mode temperatures (as used in NIOSH protocols).…”

Section: Discussionmentioning

confidence: 98%

“…7,13,15 The different EC/OC splits observed with the NIOSH and IMPROVE methods have been attributed to both differences in the temperature protocol used during the analysis 9,16-18 and to differences in the optical methods for monitoring changes in the optical properties of the specimen to correct for charring (that is, transmittance used generally by the NIOSH method, including the ACE-Asia protocol, versus reflectance used generally by the IMPROVE method). [16][17][18] Both of these factors lead to higher EC concentration estimates with the IMPROVE method than with the NIOSH method. The discrepancy between the two methods has been found to vary by season and PM source and composition, suggesting that the different methods may classify particular carbon species, such as carbon from biomass burning and secondary OC, differently.…”

Section: Introductionmentioning

confidence: 92%

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Impact of ambient fine particulate matter carbon measurement methods on observed associations with acute cardiorespiratory morbidity

Winquist

Schauer

Turner

et al. 2014

J Expo Sci Environ Epidemiol

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Elemental carbon (EC) and organic carbon (OC) represent a substantial portion of particulate matter <2.5 μm in diameter (PM2.5), and have been associated with adverse health effects. EC and OC are commonly measured using the National Institute of Occupational Safety and Health (NIOSH) method or the Interagency Monitoring of Protected Visual Environments (IMPROVE) method. Measurement method differences could have an impact on observed epidemiologic associations. Daily speciated PM2.5 data were obtained from the St Louis-Midwest Supersite, and St Louis emergency department (ED) visit data were obtained from the Missouri Hospital Association for the period June 2001 to April 2003. We assessed acute associations between cardiorespiratory ED visits and EC and OC from NIOSH and IMPROVE methods using Poisson generalized linear models controlling for temporal trends and meteorology. Associations were generally similar for EC and OC from the different measurement methods. The most notable difference between methods was observed for congestive heart failure and EC (for example, warm season rate ratios (95% confidence intervals) per interquartile range change in EC concentration were: NIOSH=1.06 (0.99-1.13), IMPROVE=1.01 (0.96-1.07)). Overall, carbon measurement method had little impact on acute associations between EC, OC, and ED visits. Some specific differences were observed, however, which may be related to particle composition.

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Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 92%

Impact of ambient fine particulate matter carbon measurement methods on observed associations with acute cardiorespiratory morbidity

Winquist

Schauer

Turner

et al. 2014

J Expo Sci Environ Epidemiol

View full text Add to dashboard Cite

show abstract

“…Issues that influence the charring include temperatures and residence times, as well as chemical composition. Charring is likely to be more of an issue for oxidized organics, such as biomass burning or secondary organic aerosol (SOA), than reduced organics, such as efficient combustion products (i.e., diesel and laboratory flame soot) [36,37]. Two significant differences between OCEC and thermodenuding include: (1) OCEC techniques typically operate at higher temperatures than TDs, and (2) OCEC charring occurs in a helium atmosphere, whereas thermodenuding occurs in air (i.e., oxidizing environment).…”

Section: Introductionmentioning

confidence: 99%

Effect of Thermodenuding on the Structure of Nascent Flame Soot Aggregates

et al. 2017

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Abstract:The optical properties (absorption and scattering) of soot particles depend on soot size and index of refraction, but also on the soot complex morphology and the internal mixing with materials that can condense on a freshly emitted (nascent) soot particle and coat it. This coating can affect the soot optical properties by refracting light, or by changing the soot aggregate structure. A common approach to studying the effect of coating on soot optical properties is to measure the absorption and scattering coefficients in ambient air, and then measure them again after removing the coating using a thermodenuder. In this approach, it is assumed that: (1) most of the coating material is removed; (2) charred organic coating does not add to the refractory carbon; (3) oxidation of soot is negligible; and, (4) the structure of the pre-existing soot core is left unaltered, despite the potential oxidation of the core at elevated temperatures. In this study, we investigated the validity of the last assumption, by studying the effect of thermodenuding on the morphology of nascent soot. To this end, we analyzed the morphological properties of laboratory generated nascent soot, before and after thermodenuding. Our investigation shows that there is only minor restructuring of nascent soot by thermodenuding.

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“…S3 is available at Annals of Occupational Hygiene online). EC3 and EC5 are associated with temperatures of 700°C and 890°C, respectively (Khan et al, 2011). Even though ambient particulate matter contains EC3 (Ono-Ogasawara and Myojo, 2013), it was believed that this EC3 in the quantifiable TSP area samples was indeed a signature of the MWCNTs used in this workplace due to the fact that both the area TSP sample located near the extruder and the PBZ PM 4 sample collected simultaneously yielded EC concentrations of <0.27 and <0.55 µg EC/m 3 , respectively.…”

Section: Oc-ec Analysismentioning

confidence: 99%

Aerosol Emission Monitoring and Assessment of Potential Exposure to Multi-walled Carbon Nanotubes in the Manufacture of Polymer Nanocomposites

Thompson

Chen

Wang

et al. 2015

ANNHYG

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Recent animal studies have shown that carbon nanotubes (CNTs) may pose a significant health risk to those exposed in the workplace. To further understand this potential risk, effort must be taken to measure the occupational exposure to CNTs. Results from an assessment of potential exposure to multi-walled carbon nanotubes (MWCNTs) conducted at an industrial facility where polymer nanocomposites were manufactured by an extrusion process are presented. Exposure to MWCNTs was quantified by the thermal-optical analysis for elemental carbon (EC) of respirable dust collected by personal sampling. All personal respirable samples collected (n = 8) had estimated 8-h time weighted average (TWA) EC concentrations below the limit of detection for the analysis which was about one-half of the recommended exposure limit for CNTs, 1 µg EC/m 3 as an 8-h TWA respirable mass concentration. Potential exposure sources were identified and characterized by direct-reading instruments and area sampling. Area samples analyzed for EC yielded quantifiable mass concentrations inside an enclosure where unbound MWCNTs were handled and near a pelletizer where nanocomposite was cut, while those analyzed by electron microscopy detected the presence of MWCNTs at six locations throughout the facility. Through size selective area sampling it was identified that the airborne MWCNTs present in the workplace were in the form of large agglomerates. This was confirmed by electron microscopy where most of the MWCNT structures observed were in the form of micrometer-sized ropey agglomerates. However, a small fraction of single, free MWCNTs was also observed. It was found that the high number concentrations of nanoparticles, ~200 000 particles/ cm 3 , present in the manufacturing facility were likely attributable to polymer fumes produced in the extrusion process.

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Differences in the OC/EC Ratios that Characterize Ambient and Source Aerosols due to Thermal-Optical Analysis

Cited by 89 publications

References 31 publications

Impact of ambient fine particulate matter carbon measurement methods on observed associations with acute cardiorespiratory morbidity

Impact of ambient fine particulate matter carbon measurement methods on observed associations with acute cardiorespiratory morbidity

Effect of Thermodenuding on the Structure of Nascent Flame Soot Aggregates

Aerosol Emission Monitoring and Assessment of Potential Exposure to Multi-walled Carbon Nanotubes in the Manufacture of Polymer Nanocomposites

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