Thermal Optical Transmittance Research Articles

Zirconia toughened mica glass ceramics for dental restorations: Wear, thermal, optical and cytocompatibility properties

BackgroundIn an effort to design novel zirconia reinforced mica glass ceramics for dental restorations, clinically relevant properties such as wear, coefficient of thermal expansion, optical transmittance, and cytocompatibility with human gingival fibroblast cell lines were investigated in the present study. Materials & MethodsMicrostructure analysis of two body wear of heat treated mica glass ceramic ceramics (47.2 SiO2–16.7 Al2O3–9.5 K2O–14.5 MgO–8.5 B2O3–6.3F wt.%) reinforced with 20wt.% YSZ, were evaluated against a steatite antagonist in a chewing simulator following Willytec Munich method. In addition, Coefficient of thermal expansion (CTE), total transmittance, scattering coefficient and cytocompatibility on human gingival fibroblast cell lines were performed and compared to the commercially available dental ceramic systems. ResultsThe experimental mica glass ceramic demonstrate micro-ploughing, pull out and debris formation along the cutting surface, indicating abrasive wear mechanism. Thermal expansion of mica glass ceramic composite was recorded as 5×10−6/°C, which is lower than the thermal expansion of commercially available core and veneering ceramics. Further, significant differences of transmittance and scattering coefficient of mica glass ceramics with 20wt.% YSZ with commercial dental ceramics was found and extensive fibroblast cell spreading with filopodial extension, cell-to-cell bridges and proliferation with human gingival fibroblast cell lines. ConclusionWith acceptable cytocompatibility with human gingival fibroblast cells and better wear properties with respect to commercial IPS emax Press, the mica glass ceramic composites (47.2 SiO2–16.7Al2O3–9.5 K2O–14.5 MgO–8.5 B2O3–6.3F wt.%) with 20wt.% YSZ have the potential for dental restorative applications as machinable veneering ceramics.

Pollution Characteristics and Sources of Carbonaceous Components in PM2.5 in the Guanzhong Area

In order to study the pollution characteristics and sources of fine particulate matter in the Guanzhong area of China, PM2.5 samples were collected and observed by hand from September 4, 2017 to January 19, 2018 at five sites (XA, WN, TCH, BJ and XY). The carbonaceous component of these samples was analyzed by thermal-optical transmission, which showed that the average concentrations of OC and EC in the fine particulate matter were (14.48±7.86) μg·m-3 and (2.27±0.95) μg·m-3, respectively, Percentages of OC and EC were 18.04% and 2.99%, respectively. Compared with other cities, the measured levels of pollution in the Guanzhong areas were more severe. The spatial distribution of percentage of carbon component in PM2.5 was XY > WN > XA > BJ > TCH, and the concentrations in winter were higher than in autumn. The correlation between OC and EC was significant (R2=0.79), which indicates a common source. The highest proportion of OC1 was 23.44%. The concentration of the carbonaceous component from high to low was OC1 > EC2 > EC3 > OC4 > EC1 > OC2 > OC3 > EC4 > EC6 > EC5. The results of PMF modeling show that the four main contributing sources of carbon components in pollution in this area are biomass combustion and coal-burning, gasoline vehicle exhaust emissions, diesel vehicle exhaust emissions, and road dust, contribution 48.63%, 23.07%, 18.82%, and 9.47%, respectively. Furthermore, there were clear differences in the pollution structure at each study site.

열-광학 투과법을 이용한 준 실시간과 필터방법 사이의 탄소성분 농도 비교

열-광학 투과법을 이용한 준 실시간과 필터방법 사이의 탄소성분 농도 비교

Comparison of measurement methods for the characterization of the black carbon emissions from a T63 turboshaft engine burning conventional and Fischer-Tropsch fuels

ABSTRACTEmission measurements of black carbon (BC) mass were conducted on a T63 turboshaft engine, operated at idle and cruise power with conventional and alternative fuels, using an Artium LII-300 laser-induced incandescence analyzer (LII) and AVL model 483 micro soot sensor (MSS) photoacoustic instrument using the manufacturer’s calibration for both instruments. These measurements were compared with elemental carbon (EC) determined by manual and semicontinuous thermal-optical transmission analyses according to National Institute for Occupational Safety and Health (NIOSH) method 5040 as the reference method. The results indicate that both the LII and MSS instruments show good linear correlation with EC for the two fuels and two engine power conditions evaluated. The LII measurements were observed to be biased high (27–49%) and the MSS measurements were biased low (24–35%) relative to EC. The agreement between the instruments and the reference method was substantially improved by applying a calibration of the instruments against a common BC aerosol source. Test data also suggest that the two instruments show some sensitivity to particle size (or properties related to size), specifically for particles with a geometric mean diameter (GMD) <30 nm. This sensitivity is problematic, since new engines or certain combustion conditions in current engines will produce smaller particles compared with the T63 model tested in this study. Further assessments of instrument performance for particles within this size range are therefore warranted.Implications: Accurate black carbon emission measurements are needed to certify new and in-production commercial aircraft engines. Both the Artium LII-300 and AVL 483 micro soot sensor are currently approved by the International Civil Aviation Organization for this purpose. This study compares the two instruments against elemental carbon (EC) using NIOSH method 5040 as the reference using a T63 turboshaft engine. The results indicate that both instruments correlate reasonably well with EC, and the correlation substantially improved when applying a calibration against a common aerosol source. Sensitivity to particle size may be an issue for both instruments.

Composition and origin of PM2.5 in Mediterranean Countryside

In this work PM2.5 was collected during winter and summer in a Sardinian village (Gonnostramatza, Italy) highly affected by biomass burning emissions. A multi-technique approach was adopted for the complete PM chemical characterization. The bulk characterization was performed by IC (Ion Chromatography), HPAEC (High-Performance Anion-Exchange Chromatography), TOT (Thermal Optical Transmittance) and ED-XRF (Energy-Dispersive X-Ray Fluorescence) while XPS (X-ray Photoelectron Spectroscopy) was used for the surface characterization. Using levoglucosan as specific tracer of biomass burning emissions, the assessment of the impact of this source was carried out and it represent the major PM source at the investigate site during winter. In winter the average levoglucosan concentration is 2096 ± 324 ng/m3 while during summer its concentration is negligible (18 ± 7 ng/m3). Levoglucosan content in PM2.5 during winter is on average 13.7%; it is estimated that 65% of PM2.5 is due to wood burning. XPS has been exploited in this work aiming at highlighting possible differences between surface and bulk composition of PM2.5. The surface of the particulate matter resulted enriched in carbon compared to the bulk. Among the components of XPS C1s signals recorded on the samples collected during winter, it was found that the signal at 286.5 eV, which is due to the presence of COH, reflects the bulk composition of levoglucosan.

Biomass burning history in East Asia during the last 4 million years recorded in elemental carbon variability at IODP site U1423

The burning of trees and grasses produces charred particles, such as charcoal and soot, that can be transported over long distances via winds and rivers to coastal, deltaic, and ocean environments, where they are preserved in sediments. Charcoal contained in sediments has been widely used as a proxy for biomass burning and human activities as well as climate change. Charcoal and soot in Cenozoic marine sediments at Integrated Ocean Drilling Program (IODP) Expedition (Exp.) 346 Site U1423 were measured to examine the regional history of biomass burning in East Asia. Charcoal and soot were measured as elemental carbon (EC) in coarse (> 2 μm) and fine (< 2 μm) fractions using grain size separation by repeated settling followed by application of a thermal optical transmittance (TOT) method. Organic carbon (OC) was also quantified during the process. EC and OC in both coarse and fine fractions are higher from 0 to 1.8 Ma and lower from 1.8 to 4.3 Ma but have large variations, which suggest more frequent or intense biomass burning since 1.8 Ma. Terrestrial biomass and precipitation could be major controls on the EC supply. Fine EC varies independently from coarse EC, which suggests a remote origin of fine EC. Large increases in terrestrial vegetation cover have led to high-temperature burning, which is associated with interglacial stages.

Seasonal and annual trends of carbonaceous species of PM10 over a megacity Delhi, India during 2010–2017

PM10 samples were collected to characterize the seasonal and annual trends of carbonaceous content in PM10 at an urban site of megacity Delhi, India from January 2010 to December 2017. Organic carbon (OC) and elemental carbon (EC) concentrations were quantified by thermal-optical transmission (TOT) method of PM10 samples collected at Delhi. The average concentrations of PM10, OC, EC and TCA (total carbonaceous aerosol) were 222 ± 87 (range: 48.2–583.8 μg m−3), 25.6 ± 14.0 (range: 4.2–82.5 μg m−3), 8.7 ± 5.8 (range: 0.8–35.6 μg m−3) and 54.7 ± 30.6 μg m−3 (range: 8.4–175.2 μg m−3), respectively during entire sampling period. The average secondary organic carbon (SOC) concentration ranged from 2.5–9.1 μg m−3 in PM10, accounting from 14 to 28% of total OC mass concentration of PM10. Significant seasonal variations were recorded in concentrations of PM10, OC, EC and TCA with maxima during winter and minima during monsoon seasons. In the present study, the positive linear trend between OC and EC were recorded during winter (R2 = 0.53), summer (R2 = 0.59) and monsoon (R2 = 0.78) seasons. This behaviour suggests the contribution of similar sources and common atmospheric processes in both the fractions. OC/EC weight ratio suggested that vehicular emissions, fossil fuel combustion and biomass burning could be the major sources of carbonaceous aerosols of PM10 at the megacity Delhi, India. Trajectory analysis indicates that the air mass approches to the sampling site is mainly from Indo Gangetic plain (IGP) region (Uttar Pradesh, Haryana and Punjab etc.), Thar desert, Afghanistan, Pakistan and surrounding areas.

Characteristics and Source Analysis of Carbonaceous Components of PM2.5 During Autumn in the Northern Suburb of Nanjing

In this study, PM2.5 samples were collected from October to November of 2015 in the northern suburb of Nanjing. The mass concentrations of organic carbon (OC), elemental carbon (EC), and levoglucosan in the samples were analyzed by thermal optical transmittance (TOT) and ion chromatography. The average concentrations of OC and EC were respectively (11.3±4.9) μg·m-3 and (1.1±0.9) μg·m-3. The average total carbon (TC) was 22.9%, and the OC/EC was 7.4. The quality concentrations of PM2.5, OC, EC, and SOC all reflected daytime features, and the correlation between OC and EC was better during the day than at night (correlation coefficients of 0.86 for day and 0.7 for night). By analyzing the mass concentrations of PM2.5, levoglucosan, and SOC, as well as the data of backward trajectories and fire point data, it was determined that the northern suburb of Nanjing is affected by the long-distance transportation of biomass from Hebei and other places from October 13-16. The correlations between levoglucosan and OC, EC, or SOC were significant (correlation coefficients of 0.78, 0.79, and 0.65, respectively), and the contribution of biomass combustion during sampling to OC was 21.9%.

Spring-time PM2.5 elemental analysis and polycyclic aromatic hydrocarbons measurement in High-rise residential buildings in Chongqing and Xian, China

The mass concentration and the elemental composition of PM2.5 and polycyclic aromatic hydrocarbons were measured in 30 residential apartments during spring in the city of Xian and Chongqing, China. A total of 45 major, minor and trace elements were determined by X-Ray Fluorescence analysis. The carbonaceous species were determined with the thermal–optical transmittance technique. The daily PM2.5 mass concentration ranged from 25 to 140 µg/m3. The following compounds had higher concentrations outdoors than indoors and had higher concentrations in Xi'an than in Chongqing: Na, Al, Si, K, Mn, Fe, Cu, Zn, Br. Sulfur had higher concentrations in Chongqing than in Xi'an and had higher concentrations outdoors than indoors. For the strongly enriched elements (enrichment factor > 100) like S, Cl, Zn, Br, an anthropogenic origin can be suggested. In this study, the average ratio of organic carbon to elemental carbon was 4.9, indicating the possible presence of secondary organic carbon.

Comparison of filter smoke number and elemental carbon from thermal optical analysis of marine diesel engine exhaust

The interest on contribution of shipping to global warming and especially on polar ice melting has increased. The International Maritime Organization is working toward reporting and estimation of black carbon emissions from shipping. The filter smoke number method is discussed as one possible candidate for onboard determination of black carbon/soot concentration of the engine exhaust gas, and it has recently been considered as one of the best candidates for further evaluation in the International Council on Clean Transportation 4th workshop on marine black carbon emission. Proven, standardized technology and small size and simple operation of the filter smoke meter make it a potential choice for actual onboard use. In our study, we evaluated the validity of the filter smoke number method for measuring soot emission by looking at correlations between the filter smoke number and elemental carbon analyzed using thermal optical transmittance analysis. Until now the conversion of the filter smoke number to black carbon /soot emission has been performed with equations derived from high-speed engines operating with distillate fuels. We introduce optimized calculation parameters for filter smoke number to black carbon/soot conversion, which are derived from light and heavy fuel oil measurements. These new parameters can be utilized with improved accuracy for the estimation of the black carbon emission from filter smoke number measurement with marine fuel qualities.

Efficient electrochemical degradation of multiwall carbon nanotubes

As the production mass of multiwall carbon nanotubes (MWCNT) increases, the potential for human and environmental exposure to MWCNTs may also increase. We have shown that exposing an aqueous suspension of pristine MWCNTs to an intense oxidative treatment in an electrochemical reactor, equipped with an efficient hydroxyl radical generating Boron Doped Diamond (BDD) anode, leads to their almost complete mineralization. Thermal optical transmittance analysis showed a total carbon mass loss of over two orders of magnitude due to the electrochemical treatment, a result consistent with measurements of the degraded MWCNT suspensions using UV–vis absorbance. Liquid chromatography data excludes substantial accumulation of the low molecular weight reaction products. Therefore, up to 99% of the initially suspended MWCNT mass is completely mineralized into gaseous products such as CO2 and volatile organic carbon. Scanning electron microscopy (SEM) images show sporadic opaque carbon clusters suggesting the remaining nanotubes are transformed into structure-less carbon during their electrochemical mineralization. Environmental toxicity of pristine and degraded MWCNTs was assessed using Caenorhabditis elegans nematodes and revealed a major reduction in the MWCNT toxicity after treatment in the electrochemical flow-by reactor.

Inter-Comparison of Carbon Content in PM2.5 and PM10 Collected at Five Measurement Sites in Southern Italy

A field campaign was performed simultaneously at five measurement sites, having different characteristics, to characterize the spatial distribution of the carbonaceous content in atmospheric aerosol in Southern Italy during the winter season. Organic carbon (OC) and elemental carbon (EC) were measured at urban (Naples), suburban (Lecce), coastal/marine (Lamezia Terme and Capo Granitola), and remote (Monte Curcio) locations. OC and EC mass concentrations were quantified by the thermal-optical transmission (TOT) method, in 24-h PM10 and PM2.5 samples collected on quartz fiber filters, from 25 November 2015 to 1 January 2016. The different sites showed marked differences in the average concentrations of both carbonaceous species. Typically, OC average levels (±standard deviation) were higher at the sites of Naples (12.8 ± 5.1 and 11.8 ± 4.6 μg/m3) and Lecce (10.7 ± 5.8 and 9.0 ± 4.7 μg/m3), followed by Lamezia Terme (4.3 ± 2.0 and 4.0 ± 1.9 μg/m3), Capo Granitola (2.3 ± 1.2 and 1.7 ± 1.1 μg/m3), and Monte Curcio (0.9 ± 0.3 and 0.9 ± 0.3 μg/m3) in PM10 and PM2.5, respectively. Similarly, EC average levels (±standard deviation) were higher at the urban sites of Naples (2.3 ± 1.1 and 1.8 ± 0.5 μg/m3) and Lecce (1.5 ± 0.8 and 1.4 ± 0.7 μg/m3), followed by Lamezia Terme (0.6 ± 0.3 and 0.6 ± 0.3 μg/m3), Capo Granitola (0.3 ± 0.3 and 0.3 ± 0.2 μg/m3), and Monte Curcio (0.06 ± 0.04 and 0.05 ± 0.03 μg/m3) in PM10 and PM2.5, respectively. An opposite trend was observed for the OC/EC ratios ranging from 6.4 to 15.9 in PM10 and from 6.4 to 15.5 in PM2.5 with lower values in urban sites compared to remote sites. Different OC-EC correlations, 0.36 &lt; R2 &lt; 0.90, were found in four observation sites. This behavior suggests the contributions of similar sources and common atmospheric processes in both fractions. No correlations were observed between OC and EC at the site of Naples. The average secondary organic carbon (SOC) concentrations, quantified using the minimum OC/EC ratio method, ranged from 0.4 to 7.6 μg/m3 in PM10 and from 0.4 to 7.2 μg/m3 in PM2.5, accounting from 37 to 59% of total OC in PM10 and from 40 to 57% in PM2.5 with higher percentages in the urban and suburban sites of Naples and Lecce.

Evaluation of thermal optical analysis method of elemental carbon for marine fuel exhaust

ABSTRACTThe awareness of black carbon (BC) as the second largest anthropogenic contributor in global warming and an ice melting enhancer has increased. Due to prospected increase in shipping especially in the Arctic reliability of BC emissions and their invented amounts from ships is gaining more attention. The International Maritime Organization (IMO) is actively working toward estimation of quantities and effects of BC especially in the Arctic. IMO has launched work toward constituting a definition for BC and agreeing appropriate methods for its determination from shipping emission sources. In our study we evaluated the suitability of elemental carbon (EC) analysis by a thermal-optical transmittance (TOT) method to marine exhausts and possible measures to overcome the analysis interferences related to the chemically complex emissions. The measures included drying with CaSO4, evaporation at 40–180ºC, H2O treatment, and variation of the sampling method (in-stack and diluted) and its parameters (e.g., dilution ratio, Dr). A reevaluation of the nominal organic carbon (OC)/EC split point was made. Measurement of residual carbon after solvent extraction (TC-CSOF) was used as a reference, and later also filter smoke number (FSN) measurement, which is dealt with in a forthcoming paper by the authors. Exhaust sources used for collecting the particle sample were mainly four-stroke marine engines operated with variable loads and marine fuels ranging from light to heavy fuel oils (LFO and HFO) with a sulfur content range of <0.1–2.4% S. The results were found to be dependent on many factors, namely, sampling, preparation and analysis method, and fuel quality. It was found that the condensed H2SO4 + H2O on the particulate matter (PM) filter had an effect on the measured EC content, and also promoted the formation of pyrolytic carbon (PyC) from OC, affecting the accuracy of EC determination. Thus, uncertainty remained regarding the EC results from HFO fuels.Implications: The work supports one part of the decision making in black carbon (BC) determination methodology. If regulations regarding BC emissions from marine engines will be implemented in the future, a well-defined and at best unequivocal method of BC determination is required for coherent and comparable emission inventories and estimating BC effects. As the aerosol from marine emission sources may be very heterogeneous and low in BC, special attention to the effects of sampling conditions and sample pretreatments on the validity of the results was paid in developing the thermal-optical analysis methodology (TOT).

The effect of cetyltrimethylammonium bromide on the coefficient of thermal expansion and optical transmittance of poly(ether sulfone) film

Cetyltrimethylammonium bromide (CTAB) was used as a stabilizing agent for PES films, and its effect on the coefficient of thermal expansion (CTE) and optical transmittance (OT) of PES films was investigated. The CTE of PES film decreased with increasing CTAB concentration up to 0.5 wt%, because of the improved intermolecular interaction between polymer chains via CTAB molecules. When 0.5 wt% of CTAB was added to the PES film, the CTE of polymer film decreased from 66 to 50 ppm/°C without noticeable reduction in OT. At such a low CTAB concentration range (<0.5 wt%), the glass transition temperature (T g ) and tensile strength increased with CTAB. At high CTAB concentration above 0.5 wt%, however, it had a negative effect on the properties of PES film - CTE increased but T g and tensile strength decreased with it.

Extraction and process analysis of high aspect ratio cellulose nanocrystals from corn (Zea mays) agricultural residue

Cellulose nanocrystals (CNCs) have long been an interest of researchers because of their exceptional mechanical properties as well as being sourced from natural, inexpensive, and renewable materials. In this work, maize CNCs (m-CNC) were obtained from maize (Zea mays) husk, which is an agricultural residue. This material is a common waste product from agricultural production in different parts of the world, and of potential value if CNCs with advantageous properties are extracted from them. Maize husk is a major agricultural waste in the United States and is used for erosion prevention or to produce insulating materials, paper, and other chemicals. Dried materials were alkali treated, bleached, and hydrolyzed to CNCs using sulfuric acid. The extracted CNCs were found to have a length of 940±70nm and width of 6±2nm, high aspect ratio of approximately 157, and increase the Young’s modulus of natural rubber composites from 0.89±0.15MPa to 1.98±0.73MPa with the addition of 2wt% m-CNCs. Other characterization techniques employed in this study are dynamic light scattering (DLS), conductometry, thermal gravimetric analysis (TGA), x-ray diffraction (XRD), and optical transmittance. Maize husks provided high aspect ratio cellulose Iβ CNCs, similar to tunicate CNCs, but with much lower processing required. Therefore, m-CNCs are more cost effective as shown by an economic evaluation. This study could provide assistance for producing CNC from one of the world’s largest supply of agricultural waste.

Role of iodine in broadening the optical window of As[sbnd]Sb[sbnd]S[sbnd]I chalcogenide glass system

Present article describes the preparation of new series of chalcogenide glasses in As-Sb-S-I system with an aim to explore its thermal and optical properties. Arsenic and antimony concentrations were varied by keeping the concentration of sulphur and iodine constant in the studied glass compositions. Bulk glasses were prepared by following melt quenching technique and then investigated further for thermal stability, optical transmission and impurities present within the resulted glasses. Optical band gap (Eg) was calculated using Tauc equations where it was found that Eg is in harmony with structural arrangement of glasses. The glasses with the combination of higher arsenic and iodine have their UV band edge blue shifted while the glasses with the combination of higher antimony and iodine showing their IR cut-off red shifted.

Chemical characterization of organic particulate matter from on-road traffic in São Paulo, Brazil

Abstract. This study reports emission of organic particulate matter by light-duty vehicles (LDVs) and heavy-duty vehicles (HDVs) in the city of São Paulo, Brazil, where vehicles run on three different fuel types: gasoline with 25 % ethanol (called gasohol, E25), hydrated ethanol (E100), and diesel (with 5 % biodiesel). The experiments were performed at two tunnels: Jânio Quadros (TJQ), where 99 % of the vehicles are LDVs, and RodoAnel Mário Covas (TRA), where up to 30 % of the fleet are HDVs. Fine particulate matter (PM2.5) samples were collected on quartz filters in May and July 2011 at TJQ and TRA, respectively. The samples were analyzed by thermal-desorption proton-transfer-reaction mass spectrometry (TD-PTR-MS) and by thermal–optical transmittance (TOT). Emission factors (EFs) for organic aerosol (OA) and organic carbon (OC) were calculated for the HDV and the LDV fleet. We found that HDVs emitted more PM2.5 than LDVs, with OC EFs of 108 and 523 mg kg−1 burned fuel for LDVs and HDVs, respectively. More than 700 ions were identified by TD-PTR-MS and the EF profiles obtained from HDVs and LDVs exhibited distinct features. Unique organic tracers for gasoline, biodiesel, and tire wear have been tentatively identified. nitrogen-containing compounds contributed around 20 % to the EF values for both types of vehicles, possibly associated with incomplete fuel burning or fast secondary production. Additionally, 70 and 65 % of the emitted mass (i.e. the OA) originates from oxygenated compounds from LDVs and HDVs, respectively. This may be a consequence of the high oxygen content of the fuel. On the other hand, additional oxygenation may occur during fuel combustion. The high fractions of nitrogen- and oxygen-containing compounds show that chemical processing close to the engine / tailpipe region is an important factor influencing primary OA emission. The thermal-desorption analysis showed that HDVs emitted compounds with higher volatility, and with mainly oxygenated and longer chain hydrocarbons than LDVs.

Inter-comparison of NIOSH and IMPROVE protocols for OC and EC determination: implications for inter-protocol data conversion

Abstract. Organic carbon (OC) and elemental carbon (EC) are operationally defined by analytical methods. As a result, OC and EC measurements are protocol dependent, leading to uncertainties in their quantification. In this study, more than 1300 Hong Kong samples were analyzed using both National Institute for Occupational Safety and Health (NIOSH) thermal optical transmittance (TOT) and Interagency Monitoring of Protected Visual Environment (IMPROVE) thermal optical reflectance (TOR) protocols to explore the cause of EC disagreement between the two protocols. EC discrepancy mainly (83 %) arises from a difference in peak inert mode temperature, which determines the allocation of OC4NSH, while the rest (17 %) is attributed to a difference in the optical method (transmittance vs. reflectance) applied for the charring correction. Evidence shows that the magnitude of the EC discrepancy is positively correlated with the intensity of the biomass burning signal, whereby biomass burning increases the fraction of OC4NSH and widens the disagreement in the inter-protocol EC determination. It is also found that the EC discrepancy is positively correlated with the abundance of metal oxide in the samples. Two approaches (M1 and M2) that translate NIOSH TOT OC and EC data into IMPROVE TOR OC and EC data are proposed. M1 uses direct relationship between ECNSH_TOT and ECIMP_TOR for reconstruction: M1 : ECIMP_TOR = a × ECNSH_TOT + b; while M2 deconstructs ECIMP_TOR into several terms based on analysis principles and applies regression only on the unknown terms: M2 : ECIMP_TOR = AECNSH + OC4NSH − (a × PCNSH_TOR + b), where AECNSH, apparent EC by the NIOSH protocol, is the carbon that evolves in the He–O2 analysis stage, OC4NSH is the carbon that evolves at the fourth temperature step of the pure helium analysis stage of NIOSH, and PCNSH_TOR is the pyrolyzed carbon as determined by the NIOSH protocol. The implementation of M1 to all urban site data (without considering seasonal specificity) yields the following equation: M1(urban data) : ECIMP_TOR = 2.20 × ECNSH_TOT − 0.05. While both M1 and M2 are acceptable, M2 with site-specific parameters provides the best reconstruction performance. Secondary OC (SOC) estimation using OC and EC by the two protocols is compared. An analysis of the usability of reconstructed ECIMP_TOR and OCIMP_TOR suggests that the reconstructed values are not suitable for SOC estimation due to the poor reconstruction of the OC / EC ratio.

A comparison between thermal-optical transmittance elemental carbon measured by different protocols in PM2.5 samples

Although controlled procedures for the determination of carbonaceous fractions are of importance for any air quality measurements, currently no reference method for elemental carbon (EC) and organic carbon (OC) analysis is established yet in Europe. The implementation of the different thermal evolution protocols available in the literature, differing in temperature and duration of the heating ramps, affects the results and can result in a wide variation of EC and OC values. In this study three different protocols for thermal-optical-transmittance analysis of EC and OC were compared, namely He-870 (a variation of the NIOSH protocol), He-550 (a proxy of the IMPROVE protocol), and EUSAAR_2. Measurements were carried out on PM2.5 samples collected on Quartz fibre filters in three sites of different typology: urban background and urban traffic in Florence (Italy) and regional background in Livorno (Italy). The samples were analysed before and after a washing procedure to remove possible water-soluble organic compounds (WSOC), which may enhance the charring process, complicating the EC quantification.This study evidenced a very good agreement for TC measurement (at 2–3% level) and some discrepancies in EC measurement (up to 40%), as expected. WSOC and Pyrolitic Carbon (PyC) present a good correlation, independently of site typology, demonstrating that water soluble compound can be responsible of charring mechanism during the He phase.

Characterization of sampling artifacts in the measurement of carbonaceous particles using high- and low-volume samplers in Daejeon, Korea

This study investigates the influence of positive sampling artifacts on the determination of atmospheric organic carbon (OC) and elemental carbon (EC) by undenuded high-volume (HV) and low-volume (LV) samplers. The samples, which were collected in Daejeon, Korea during the spring and fall of 2014, were analyzed for OC and EC using a thermal optical transmittance (TOT) technique. Positive artifacts for OC using the undenuded LV and HV samplers were determined to be ∼12.2% and ∼7.2%, respectively. The adsorption of organic vapors on quartz filters and the analytical artifacts of thermal-optical method contributed equally to the positive artifact for the HV sampler, whereas that of the undenuded LV sampler was caused primarily by the adsorption of organic vapors on quartz filters with a relatively small contribution from the analytical artifacts of thermal-optical method. The analytical artifacts of thermal-optical method was closely related to the additional formation of pyrolyzed OC (POC) during the analysis, resulting in an underestimation of EC (HV sampler: 15.6 ± 15.6%; undenuded LV sampler: 9.1 ± 7.6%). The POC that formed during the analysis was related to the adsorption of organic vapors (in both the HV and undenuded LV samplers) and high particle loading on the quartz filters (HV sampler only). OC concentrations determined using the undenuded LV sampler and corrected using backup filter measurements correlated well with those of the denuded LV sampler (R2 = 0.98), suggesting that the backup filter correction method can be applied to particulate OC measurements using an undenuded LV sampler under conditions typical of those in Daejeon, Korea.