Thermal-optical Carbon Analyzer Research Articles

Characteristics and Source Analysis of Carbonaceous Aerosols in PM2.5 in Huaxi District, Guiyang

Carbonaceous aerosol, as an important component of atmospheric aerosol, has a significant impact on atmospheric environmental quality, human health, and global climate change. To investigate the characteristics and sources of carbonaceous aerosol in atmospheric fine particulate matter (PM2.5) in Huaxi District of Guiyang, an in-situ observational study was conducted during different seasons in 2020, and the carbonaceous components of PM2.5 were measured using a thermal-optical carbon analyzer (DRI Model 2015). The results of the study showed that the average concentrations of PM2.5, total carbonaceous aerosol (TCA), organic carbon (OC), secondary organic carbon (SOC), and elemental carbon (EC) concentrations during the observation period were (39.7±22.3), (14.1±7.2), (7.6±3.9), (4.4±2.6), and (2.0±1.0) μg·m-3, respectively, and the mean value of OC/EC was (3.9±0.8). ρ(PM2.5), ρ(TCA), ρ(OC), ρ(SOC), and ρ(EC) showed a seasonal variation pattern with the highest in winter [(52.6±28.6), (17.0±9.6), (9.1±5.2), (6.1±3.9), and (2.4±1.2) μg·m-3, respectively] and the lowest in summer [(25.1±7.1), (11.6±3.6), (6.3±1.9), (3.7±1.2), and (1.6±0.6) μg·m-3, respectively]. The seasonal variation in OC/EC showed summer (4.2±0.8) > winter (3.8±0.9) > autumn (3.8±0.5) > spring (3.7±0.9), indicating the presence of SOC generation in all seasons in Huaxi District. SOC showed a significant correlation with OC (R2 =0.9), and the SOC concentration tended to increase with the increase in atmospheric oxidation. OC showed a good correlation with EC in all seasons, with the highest in autumn (R2 =0.9) and lower correlations in the other three seasons (R2 ranged from 0.74 to 0.75), indicating a common source. According to OC/EC ratio range, it was preliminarily determined that carbonaceous aerosol came from vehicle exhaust emissions, coal burning emissions, and biomass combustion emissions. In order to further quantify the contribution of major emission sources to carbonaceous aerosol, the results of this study using PMF to analyze the sources of carbonaceous aerosol showed that the main sources of carbonaceous aerosol in Huaxi District of Guiyang were coal combustion sources (29.3%), motor vehicle emission sources (21.5%), and biomass combustion sources (49.2%).

Mass and Light Absorption Properties of Atmospheric Carbonaceous Aerosols over the Outflow Regions of Indo-Gangetic Plain

The uncertainty associated with carbonaceous aerosols in climate models becomes an obstacle to evaluating their harmful environmental effects. Brown Carbon (BrC) has recently become an eye-catching carbonaceous aerosol in ambient air because of its strong light absorption properties. The optical properties of soluble BrC are well studied in South Asia, one of the largest emitters. However, the absorption property of strong light-absorbing insoluble BrC is highly uncertain because of their complex mixing. Besides, the simultaneous apportionment of light-absorbing carbonaceous aerosol constituents as a function of wavelengths is seldom explored. The present study aims to study mass as well as apportionment of absorption properties of Black Carbon (BC) and different BrC chromophores using a multi-wavelength thermal-optical carbon analyzer over the least explored Eastern part of India to fill the knowledge gap. The output suggested that the primary emission sources dominate the carbonaceous aerosol mass; thus, the primary emission reductions will be helpful in improving the local air quality. The BrC is the dominant light-absorbing carbonaceous aerosol in the ultraviolet wavelengths. Besides, significant light absorption by BrC chromophores in near-infrared wavelengths (up to ∼50% of total aerosol absorption) suggested the absorption by BrC in longer wavelengths cannot be neglected. The insoluble fraction of BrC (Tar-BrC), which has a property identical to BC, contributes significantly to light absorption and is more than 50% of total absorption by aerosols in shorter ≤635 nm wavelengths. The present study also revealed that the contribution of Tar-BrC is more pronounced in the Indo-Gangetic Plain (IGP) outflow region than in the IGP emission source regions.

Mass spectrometric analysis of unprecedented high levels of carbonaceous aerosol particles long-range transported from wildfires in the Siberian Arctic

Abstract. Wildfires in Siberia generate large amounts of aerosols, which may be transported over long distances and pose a threat to the sensitive ecosystem of the Arctic. Particulate matter (PM) of aged wildfire plumes originating from Yakutia in August 2021 was collected in Nadym and on Bely Island (both in northwestern Siberia). An advanced analysis of the chemical composition of aerosol particles was conducted through a multi-wavelength thermal–optical carbon analyzer (TOCA) coupled to resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS) as well as through ultra-high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). In Nadym, concentrations of organic carbon (OC) and elemental carbon (EC) peaked at 100 and 40 µg m−3, respectively, associated with Angström absorption exponents for 405 and 808 nm (AAE405/808) between 1.5 and 3.3. The weekly average on Bely Island peaked at 8.9 µg m−3 of OC and 0.3 µg m−3 of EC and AAE405/808 close to unity. In particular, ambient aerosol in Nadym had a distinct biomass burning profile with pyrolysis products from carbohydrates, such as cellulose and hemicellulose, as well as lignin and resinoic acids. However, temporarily higher concentrations of five- and six-ring polycyclic aromatic hydrocarbons (PAHs), different from the PAH signature of biomass burning, suggest a contribution of regional gas flaring. FT-ICR MS with electrospray ionization (ESI) revealed a complex mixture of highly functionalized compounds, containing up to 20 oxygen atoms, as well as nitrogen- and sulfur-containing moieties. Concentrations of biomass burning markers on Bely Island were substantially lower than in Nadym, flanked by the appearance of unique compounds with higher oxygen content, higher molecular weight, and lower aromaticity. Back-trajectory analysis and satellite-derived aerosol optical depth suggested long-range transport of aerosol from the center of a Yakutian wildfire plume to Nadym and from the plume periphery to Bely Island. Owing to lower aerosol concentrations in the plume periphery than in its center, it is demonstrated how dilution affects the chemical plume composition during atmospheric aging.

Seasonal and Day–Night Variations in Carbonaceous Aerosols and Their Light-Absorbing Properties in Guangzhou, China

Carbonaceous aerosols (CAs), including elemental carbon (EC) and organic carbon (OC), have become the dominant component in PM2.5 in many Chinese cities, and it is imperative to address their spatiotemporal variations and sources in order to continually improve air quality. In this study, the mass concentrations and light absorption properties of EC and OC in PM2.5 were investigated at diverse sites in Guangzhou, in the winter of 2020 and the autumn of 2021, using the DRI Model 2015 thermal–optical carbon analyzer. The results showed that total EC and organic matter (OM = OC × 1.8) could account for nearly 30% of the PM2.5 mass concentrations. Secondary production was the most important source for OC, with secondary OC (SOC) percentages in the OC as high as 72.8 ± 7.0% in autumn and 68.4 ± 13.1% in winter. Compared to those in 2015, OC and EC concentrations were reduced by 25.4% and 73.4% in 2021, highlighting the effectiveness of control measures in recent years. The absorption coefficient of brown carbon at 405 nm (babs,BrC,405) decreased by over 40%, and the mass absorption coefficient (MAC) at 405 nm of total carbon (TC) decreased by over 30%. EC and OC concentrations and the light absorption of black carbon (babs,BC,405) showed no significant diurnal differences in both autumn and winter mainly because the reduction in anthropogenic emissions at night was compensated by the lowering of the boundary layer. Differentially, babs,BrC,405 was significantly lower during daytime than at night in autumn, probably due to the daytime photobleaching effect. The sources of EC, OC, BC, and BrC were preliminarily diagnosed by their correlation with typical source markers. In autumn, babs,BrC,405 might be related to biomass burning and coal combustion, while babs,BC,405 were largely related to vehicle emissions and coal combustion. In winter, babs,BrC,405 was closely related to coal combustion.

Characterizing the sources of ambient PM10 organic aerosol in urban and rural Catalonia, Spain

Organic aerosols (OA) have recently been shown to be the dominant contributor to the oxidative potential of airborne particulate matter in northeastern Spain. We collected PM10 filter samples every fourth day from January 2017 to March 2018 at two sampling stations located in Barcelona city and Montseny Natural Park, representing urban and rural areas, respectively. The chemical composition of PM10 was analyzed offline using a broad set of analytical instruments, including high-resolution time-of-flight mass spectrometry (HR-ToF-AMS), a total organic carbon analyzer (TCA), inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), ion chromatography (IC), and thermal-optical carbon analyzer. Source apportionment analysis of the water-soluble organic content of the samples measured via HR-ToF-AMS revealed two primary and two secondary sources of OA, which included biomass-burning OA (BBOA), sulfur-containing OA (SCOA), as well as summer- and winter‑oxygenated OA (SOOA and WOOA). The presence of hydrocarbon-like water-insoluble OA was also identified based on concentration trends in black carbon and nitrogen oxides. The results from the source apportionment analysis of the inorganic composition were correlated with different OA factors to assess potential source contributors. Barcelona showed significantly higher average water-soluble OA concentrations (5.63 ± 0.56 μg m-3) than Montseny (3.27 ± 0.37 μg m-3) over the sampling period. WOOA accounted for nearly 27 % of the averaged OA in Barcelona compared to only 7 % in Montseny. In contrast, SOOA had a greater contribution to OA in Montseny (47 %) than in Barcelona (24 %). SCOA and BBOA were responsible for 15–28 % of the OA at both sites. There were also seasonal variations in the relative contributions of different OA sources. Our overall results showed that local anthropogenic sources were primarily responsible for up to 70 % of ambient soluble OA in Barcelona, and regulating local-scale emissions could significantly improve air quality in urban Spain.

Atmospheric Ultrafine Particulate Matter (PM0.1)-Bound Carbon Composition in Bangkok, Thailand

Seasonal variations in atmospheric ultrafine particulate matter (PM0.1) were monitored in Bangkok, Thailand, from 2016 to 2017. PM0.1-bound organic carbon (OC) and elemental carbon (EC) were collected by a cascade air sampler that can collect PM0.1 and were analyzed by a Thermal-Optical carbon analyzer following the IMPROVE-TOR protocol. The annual average PM0.1 in Bangkok was 14.5 ± 4.7 µg/m3, which is higher than in large Asian cities such as Shanghai and Hanoi. Biomass burning from neighboring areas was shown to increase the particle concentration. Apparent increases in carbon species such as OC and EC, and the OC/EC ratios in the wet and dry seasons were observed; the Char-EC/Soot-EC ratio revealed that the PM0.1 in the Bangkok atmosphere was influenced mainly by vehicle exhausts, even though the influence of biomass burning was greater during the dry season. The effective carbon ratio (ECR) shows that Bangkok’s carbonaceous aerosol is light-absorbing and -scattering. The higher SOC/OC in the dry season indicates the high level of secondary sources forming smaller particles from the combustion sources in Bangkok, increasing light scattering during these periods, and contributing to climate and air quality. The findings of this work are of great importance to air pollutant control policies in urban areas.

Addressing Thermal Behavior and Molecular Architecture of Asphaltenes by a Thermal-Optical Carbon Analyzer Coupled to High-Resolution Mass Spectrometry

Addressing Thermal Behavior and Molecular Architecture of Asphaltenes by a Thermal-Optical Carbon Analyzer Coupled to High-Resolution Mass Spectrometry

Highly time-resolved characterization of carbonaceous aerosols using a two-wavelength Sunset thermal–optical carbon analyzer

Abstract. Carbonaceous aerosols have great influence on the air quality, human health and climate change. Except for organic carbon (OC) and elemental carbon (EC), brown carbon (BrC) mainly originates from biomass burning as a group of OC, with strong absorption from the visible to near-ultraviolet wavelengths, and makes a considerable contribution to global warming. Large numbers of studies have reported long-term observation of OC and EC concentrations throughout the world, but studies of BrC based on long-term observations are rather limited. In this study, we established a two-wavelength method (658 and 405 nm) applied in the Sunset thermal–optical carbon analyzer. Based on a 1-year observation, we firstly investigated the characteristics, meteorological impact and transport process of OC and EC. Since BrC absorbs light at 405 nm more effectively than 658 nm, we defined the enhanced concentrations (dEC = EC405 nm − EC658 nm) and gave the possibility of providing an indicator of BrC. The receptor model and MODIS fire information were used to identify the presence of BrC aerosols. Our results showed that the carbonaceous aerosol concentrations were the highest in winter and lowest in summer. Traffic emission was an important source of carbonaceous aerosols in Nanjing. Receptor model results showed that strong local emissions were found for OC and EC; however, dEC was significantly affected by regional or long-range transport. The dEC/OC and OC/EC ratios showed similar diurnal patterns, and the dEC/OC increased when the OC/EC ratios increased, indicating strong secondary sources or biomass burning contributions to dEC. A total of two biomass burning events both in summer and winter were analyzed, and the results showed that the dEC concentrations were obviously higher on biomass burning days; however, no similar levels of the OC and EC concentrations were found both in biomass burning days and normal days in summer, suggesting that biomass burning emissions made a great contribution to dEC, and the sources of OC and EC were more complicated. Large number of open fire counts from the northwestern and southwestern areas of the study site were observed in winter and significantly contributed to OC, EC and dEC. In addition, the nearby Yangtze River Delta area was one of the main potential source areas of dEC, suggesting that anthropogenic emissions could also be important sources of dEC. The results proved that dEC can be an indicator of BrC on biomass burning days. Our modified two-wavelength instrument provided more information than the traditional single-wavelength thermal–optical carbon analyzer and gave a new idea about the measurement of BrC; the application of dEC data needs to be further investigated.

Characteristics and Source Apportionment of Carbon Components in Road Dust in Anshan

In order to study the characteristics and sources of carbon fractions in PM2.5 in road dust in Anshan, road dust samples were collected from nine roads in Anshan in October 2014 and re-suspended on filters using a NK-ZXF sampler to obtain PM2.5 samples. A thermal optical carbon analyzer (IMPROVE-TOR) was employed to measure the mass fraction of organic carbon (OC) and elemental carbon (EC) in PM2.5. The results showed that ω(TC) in PM2.5 in road dust was 9.78% (outer loop)-14.00% (Qianshan West Road), ω(OC) was 8.15% (outer loop)-10.84% (Qianshan West Road), and ω(EC) was 1.63% (outer loop)-2.85% (Qianshan West Road). ω(OC) was much higher than ω(EC), indicating that road dust contained a large amount of organic carbon. All OC/EC values were greater than 2.0 during the sampling period, suggesting that there was secondary pollution. Spearman correlation analysis and linear fitting indicated that the sources of OC and EC were basically the same. Cluster analysis results showed that carbon components in PM2.5 in road dust in Anshan mainly originated from vehicle exhaust, biomass burning, and coal combustion emissions.

Day-of-week patterns for ultrafine particulate matter components at four sites in California

Ultrafine particulate matter (PM0.1) samples were collected during three-day averaging periods over an annual cycle at four sites across California: Los Angeles, East Oakland, San Pablo, and Fresno. PM0.1 samples were analyzed for thermal carbon fractions using a thermal-optical carbon analyzer and trace elements using ICP-MS. A statistical analysis of the day-of-week trends for 15 PM0.1 components reveals location-specific patterns along with important general trends for UFP concentrations. PM0.1 elemental carbon (EC) concentrations are elevated in the middle of the week consistent with increased activity for diesel engines during this time period. Just as significantly, PM0.1 organic carbon (OC) concentrations do not exhibit a day-of-week pattern. Since OC accounts for the majority of the PM0.1 total mass, the lack of a day-of-week pattern for PM0.1 OC suggests that diesel engines do not dominate total PM0.1 mass in California. A paired t-test constructed using measurements on weekends compared to measurements immediately preceding or immediately following the weekend showed that PM0.1 potassium (K) and rubidium (Rb) concentrations were elevated on weekends. This pattern is consistent with increased biomass combustion on weekends (a previously unknown exposure pattern for UFPs). The two closest sampling locations (East Oakland and San Pablo) had the greatest number of UFP components with identical weekly trends, but even at these locations only 4 out of 15 components displayed the exact same day-of-week profiles. Less similarity was observed in measured day-of-week profiles for UFP components at other sites. The heterogeneity between sites suggests that the details of UFP concentrations at each location reflect the mixture of sources immediately adjacent to that site. By extension, individual neighborhoods across California will each experience unique day-of-week concentration profiles for UFP components that reflect the surrounding sources. These factors must be considered when estimating population exposure to ultrafine particles during future health effects studies.

Inter-comparison of elemental and organic carbon mass measurements from three North American national long-term monitoring networks at a co-located site

Abstract. Carbonaceous aerosol is a major contributor to the total aerosol load and being monitored by diverse measurement approaches. Here, 10 years (2005–2015) of continuous carbonaceous aerosol measurements collected at the Centre of Atmospheric Research Experiments (CARE) in Egbert, Ontario, Canada, on quartz-fiber filters by three independent networks (Interagency Monitoring of Protected Visual Environments, IMPROVE; Canadian Air and Precipitation Monitoring Network, CAPMoN; and Canadian Aerosol Baseline Measurement, CABM) were compared. Specifically, the study evaluated how differences in sample collection and analysis affected the concentrations of total carbon (TC), organic carbon (OC), and elemental carbon (EC). Results show that different carbonaceous fractions measured by various networks were consistent and comparable in general among the three networks over the 10-year period, even with different sampling systems/frequencies, analytical protocols, and artifact corrections. The CAPMoN TC, OC, and EC obtained from the DRI model 2001 thermal–optical carbon analyzer following the IMPROVE-TOR protocol (denoted as DRI-TOR) method were lower than those determined from the IMPROVE_A TOR method by 17 %, 14 %, and 18 %, respectively. When using transmittance for charring correction, the corresponding carbonaceous fractions obtained from the Sunset-TOT were lower by as much as 30 %, 15 %, and 75 %, respectively. In comparison, the CABM TC, OC, and EC obtained from a thermal method, EnCan-Total-900 (ECT9), were higher than the corresponding fractions from IMPROVE_A TOR by 20 %–30 %, 0 %–15 %, and 60 %–80 %, respectively. Ambient OC and EC concentrations were found to increase when ambient temperature exceeded 10 ∘C. These increased ambient concentrations of OC during summer were possibly attributed to secondary organic aerosol (SOA) formation and forest fire emissions, while elevated EC concentrations were potentially influenced by forest fire emissions and increased vehicle emissions. Results also show that the pyrolyzed organic carbon (POC) obtained from the ECT9 protocol could provide additional information on SOA although more research is still needed.

Characteristics and Source Apportionment of Carbon Components in Road Dust PM2.5 and PM10 During Spring in Tianjin Derived by Using the Quadrat Sampling Method

In order to study the characteristics and sources of carbon fractions in PM2.5 and PM10 of road dust in Tianjin, samples of road dust were collected by the quadrat sampling method in April 2015 in Tianjin, and samples were re-suspended on filters by using a NK-ZXF sampler. A Thermal Optical Carbon Analyzer (IMPROVE-TOR) was employed to measure the concentrations of organic carbon (OC) and elemental carbon (EC), and the pollution characteristics and sources were investigated by non-parametric tests and OC/EC ratio, correlation, and cluster analyses. The results showed that ω(total carbon, TC) in PM2.5 of road dust amounted to 4.89% (secondary road) -18.83% (expressway), ω(OC) amounted to 3.57% (secondary road) -15.39% (expressway), and ω(EC) amounted to 1.32% (secondary road) -3.44% (expressway); meanwhile, ω(TC) in PM10 of road dust was 8.14% (secondary road) -19.71% (expressway), ω(OC) was 5.91% (secondary road) -16.28% (expressway), and ω(EC) was 1.96% (main road) -3.43% (expressway). The mass fraction of each carbon component for the expressway was relatively high, and that for the secondary trunk road was relatively low, which may have been due to the large traffic volume on the expressway and corresponding large amounts of exhaust emissions from motor vehicles, whereas there were fewer vehicles on the secondary trunk road. Additionally, ω(OC) was significantly larger than ω(EC) for all types of roads, and ω(EC) did not vary much among the different road types. The non-parametric tests of two related samples showed that there was no significant difference in the mass fraction of each carbon component between PM2.5 and PM10. The correlation analysis showed that the sources of OC and EC in road dust were roughly the same. The OC/EC ratio analysis and cluster analysis showed that the main sources of the carbon components in the dust of roads in Tianjin in spring were coal combustion, motor vehicle exhaust, and biomass burning.

Measuring the Organic Carbon to Organic Matter Multiplier with Thermal/Optical Carbon-Quadrupole Mass Spectrometer Analyses

A thermal/optical carbon analyzer (TOA) was adapted to direct thermally-evolved gases to an electron ionization quadrupole mass spectrometer (QMS), creating a TOA-QMS. While this approach produces spectra similar to those obtained by the Aerodyne aerosol mass spectrometer (AMS), and can quantify sulfate (SO42−), nitrate (NO3−), ammonium (NH4+), and organic carbon (OC) fractions from ambient particle laden quartz-fiber filters, there remains a need to further understand the composition of the organic aerosol fraction. Elemental analysis (EA) of standard organic mixtures and ambient samples demonstrates the feasibility of the TOA-QMS for measuring the ratios of oxygen-to-carbon (O/C), hydrogen-to-carbon (H/C), nitrogen-to-carbon (N/C), sulfur-to-carbon (S/C), and organic matter-to-organic carbon (OM/OC). For ambient samples from Central California, the TOA-QMS returned average ratios for O/C of 1.03 ± 0.27 and H/C of 1.95 ± 0.69, respectively. Higher H/C ratios were observed during clean air episodes, while lower ratios were observed during hazy conditions. A relatively constant level of aerosol oxidation was observed throughout the study. The average OM/OC multiplier was 2.55 ± 0.4, which is higher than the conventionally used values of 1.4 and 1.8, indicating higher contributions from biomass burning and aged aerosols.

Seasonal variation and light absorption property of carbonaceous aerosol in a typical glacier region of the southeastern Tibetan Plateau

Abstract. Deposition and accumulation of light-absorbing carbonaceous aerosol on glacier surfaces can alter the energy balance of glaciers. In this study, 2 years (December 2014 to December 2016) of continuous observations of carbonaceous aerosols in the glacierized region of the Mt. Yulong and Ganhaizi (GHZ) basin are analyzed. The average elemental carbon (EC) and organic carbon (OC) concentrations were 1.51±0.93 and 2.57±1.32 µg m−3, respectively. Although the annual mean OC ∕ EC ratio was 2.45±1.96, monthly mean EC concentrations during the post-monsoon season were even higher than OC in the high altitudes (approximately 5000 ma.s.l.) of Mt. Yulong. Strong photochemical reactions and local tourism activities were likely the main factors inducing high OC ∕ EC ratios in the Mt. Yulong region during the monsoon season. The mean mass absorption efficiency (MAE) of EC, measured for the first time in Mt. Yulong, at 632 nm with a thermal-optical carbon analyzer using the filter-based method, was 6.82±0.73 m2 g−1, comparable with the results from other studies. Strong seasonal and spatial variations of EC MAE were largely related to the OC abundance. Source attribution analysis using a global aerosol–climate model, equipped with a black carbon (BC) source tagging technique, suggests that East Asia emissions, including local sources, have the dominant contribution (over 50 %) to annual mean near-surface BC in the Mt. Yulong area. There is also a strong seasonal variation in the regional source apportionment. South Asia has the largest contribution to near-surface BC during the pre-monsoon season, while East Asia dominates the monsoon season and post-monsoon season. Results in this study have great implications for accurately evaluating the influences of carbonaceous matter on glacial melting and water resource supply in glacierization areas.

Feasibility of coupling a thermal/optical carbon analyzer to a quadrupole mass spectrometer for enhanced PM2.5 speciation

ABSTRACTA thermal/optical carbon analyzer (TOA), normally used for quantification of organic carbon (OC) and elemental carbon (EC) in PM2.5 (fine particulate matter) speciation networks, was adapted to direct thermally evolved gases to an electron impact quadrupole mass spectrometer (QMS), creating a TOA-QMS. This approach produces spectra similar to those obtained by the Aerodyne aerosol mass spectrometer (AMS), but the ratios of the mass to charge (m/z) signals differ and must be remeasured using laboratory-generated standards. Linear relationships are found between TOA-QMS signals and ammonium (NH4+), nitrate (NO3−), and sulfate (SO42-) standards. For ambient samples, however, positive deviations are found for SO42-, compensated by negative deviations for NO3−, at higher concentrations. This indicates the utility of mixed-compound standards for calibration or separate calibration curves for low and high ion concentrations. The sum of the QMS signals across all m/z after removal of the NH4+, NO3−, and SO42- signals was highly correlated with the carbon content of oxalic acid (C₂H₂O₄) standards. For ambient samples, the OC derived from the TOA-QMS method was the same as the OC derived from the standard IMPROVE_A TOA method. This method has the potential to reduce complexity and costs for speciation networks, especially for highly polluted urban areas such as those in Asia and Africa.Implications: Ammonium, nitrate, and sulfate can be quantified by the same thermal evolution analysis applied to organic and elemental carbon. This holds the potential to replace multiple parallel filter samples and separate laboratory analyses with a single filter and a single analysis to account for a large portion of the PM2.5 mass concentration.

AMBIENT CONCENTRATIONS OF ELEMENTAL AND ORGANIC CARBON IN URBAN AND SUBURBAN ATMOSPHERES IN ESKİSEHİR: ESTIMATION OF THE SECONDARY ORGANIC CARBON

Ambient air particulate matter samples were collected from urban and suburban sites of Eskişehir in 2012. Samples were collected concurrently from both sites between 26 th of February and 20 th of December 2012. Mass concentrations of particulate matter (fine particles- PM 2.5 , coarse particles- PM 2.5-10 and total suspended particulate matter- TSP ) were determined. TSP samples were analyzed by Thermal Optical Carbon Analyzer to determine elemental carbon (EC), organic carbon (OC) and total carbon (TC) concentrations. It was found that 4.9% of the TSP is composed of EC, and 13.6 % is OC in urban sampling point. EC and OC contributions in suburban sampling points were 2.7% and 9.6% respectively. OC/EC ratio was found to be almost 1.5 times higher in suburban sampling site compared to urban sampling site. EC tracer method was used to estimate the contribution of Secondary Organic Carbon (SOC). The SOC percent of TSP was estimated as 7.1 % and 5.6 % for the urban and suburban locations respectively.

Hyphenation of a EC / OC thermal–optical carbon analyzer to photo-ionization time-of-flight mass spectrometry: an off-line aerosol mass spectrometric approach for characterization of primary and secondary particulate matter

Abstract. Source apportionment and characterization of primary and secondary aerosols remains a challenging research field. In particular, the organic composition of primary particles and the formation mechanism of secondary organic aerosols (SOAs) warrant further investigations. Progress in this field is strongly connected to the development of novel analytical techniques. In this study an off-line aerosol mass spectrometric technique based on filter samples, a hyphenated thermal–optical analyzer photo-ionization time-of-flight mass spectrometer (PI-TOFMS) system, was developed. The approach extends the capability of the widely used particulate matter (PM) carbon analysis (for elemental / organic carbon, EC / OC) by enabling the investigation of evolved gaseous species with soft and selective (resonance enhanced multi-photon ionization, REMPI) and non-selective photo-ionization (single-photon ionization, SPI) techniques. SPI was tuned to be medium soft to achieve comparability with results obtained by the electron ionization aerosol mass spectrometer (AMS). Different PM samples including wood combustion emission samples, smog chamber samples from the reaction of ozone with different SOA precursors, and ambient samples taken at Ispra, Italy, in winter as well as in summer were tested. The EC / OC–PI-TOFMS technique increases the understanding of the processes during thermal–optical analysis and identifies marker substances for the source apportionment. Composition of oligomeric or polymeric species present in PM can be investigated by the analysis of the thermal breakdown products. In the case of wood combustion, in addition to the well-known markers at m/z ratios of 60 and 73, two new characteristic masses (m/z 70 and 98) have been revealed as potentially linked to biomass burning. All four masses were also the dominant signals in an ambient sample taken in winter time in Ispra, Italy, confirming the finding that wood burning for residential heating is a major source of PM in winter at this location. The summer sample from the same location showed no influence of wood burning, but seems to be dominated by SOAs, which was confirmed from the comparison with chamber experiment samples. The experiments conducted with terpenes as precursors showed characteristic masses at m/z 58 and 82, which were not observable in any other emission samples and could serve as a marker for SOA from terpenes.

Characterization of Particulate Matter and Carbonaceous Aerosol over Two Urban Environments in Northern India

Monitoring and simultaneous sampling of Particulate matter (PM10 and PM2.5) was carried out for the first time over two urban sites in Northern India (Jabalpur and Udaipur) during December 2010–November 2012 (up to August 2012 over Udaipur). The samples of PM2.5 were analyzed for elemental carbon (EC) and organic carbon (OC) using advanced DRI Thermal optical carbon Analyzer. The monthly mean PM10 values were as high as 149 ± 44 µg m–3 over Jabalpur (JBL) and 171 ± 42.2 µg m–3 over Udaipur (UDPR). PM2.5 mass over JBL varied between 25–79 µg m–3 and over UDPR between 24–82 µg m–3. The monthly mean OC concentration varied from 12.5 ± 7.3 µg m–3 to 28.4 ± 10.7 µg m–3 over JBL and from 7.8 ± 2.9 to 39.7 ± 11.6 µg m–3 over UDPR. The variation of monthly mean EC concentration was from 3.9–10.3 µg m–3 over JBL and from 3–10.9 µg m–3 over UDPR. The contribution of TC to PM2.5 was in the range of 31–75% over JBL and 30–83% over UDPR. The EC showed higher concentration in winter and minimal values in monsoon. The OC/EC ratio showed low variation over JBL compared to that over UDPR suggesting spectrum of sources responsible for EC and OC components over UDPR. Formation of secondary organic carbon (SOC) was also recognized as a potential component altering OC/EC ratio. Up on extracting the sub fractions, it is found that OC2 and OC3 are the major component over both the sites contributing up to 51% to the total OC in different months. EC1 (EC component derived at 580°C) was found to be the major EC component contributing up to 79% over the sites.

Particle emissions from a marine engine: chemical composition and aromatic emission profiles under various operating conditions.

The chemical composition of particulate matter (PM) emissions from a medium-speed four-stroke marine engine, operated on both heavy fuel oil (HFO) and distillate fuel (DF), was studied under various operating conditions. PM emission factors for organic matter, elemental carbon (soot), inorganic species and a variety of organic compounds were determined. In addition, the molecular composition of aromatic organic matter was analyzed using a novel coupling of a thermal-optical carbon analyzer with a resonance-enhanced multiphoton ionization (REMPI) mass spectrometer. The polycyclic aromatic hydrocarbons (PAHs) were predominantly present in an alkylated form, and the composition of the aromatic organic matter in emissions clearly resembled that of fuel. The emissions of species known to be hazardous to health (PAH, Oxy-PAH, N-PAH, transition metals) were significantly higher from HFO than from DF operation, at all engine loads. In contrast, DF usage generated higher elemental carbon emissions than HFO at typical load points (50% and 75%) for marine operation. Thus, according to this study, the sulfur emission regulations that force the usage of low-sulfur distillate fuels will also substantially decrease the emissions of currently unregulated hazardous species. However, the emissions of soot may even increase if the fuel injection system is optimized for HFO operation.

Black Carbon Measurements of Flame-Generated Soot as Determined by Optical, Thermal-Optical, Direct Absorption, and Laser Incandescence Methods

Black carbon (BC) is a primary particle matter component emitted as a result of incomplete combustion. Due to its light-absorbing nature, BC can exert both direct and indirect influence on global climate. There is no universal research or regulatory definition of BC; instead, a variety of instruments and analytical methods define BC operationally. This study used a constant, source-generated BC concentration in order to quantify the variation in BC measurements using 10 different instruments and methodologies. Instruments examined include a multiangle absorption photometer, a transmissometer, rack-mount, portable, and micro-aethalometers, a thermal-optical carbon analyzer (using IMPROVE, NIOSH 5040, and NIST-EPA methods), a single-particle soot photometer (SP2), and a three-wavelength photoacoustic soot spectrometer (PASS3). BC-bearing soot was generated using an ethylene-air diffusion flame, diluted to ∼100 μg/m3, which was subjected to simultaneous analyses. Measured BC and elemental carbon (EC) concentrations ranged from 20.5 to 39.9 μg/m3. BC concentrations measured by aethalometers and transmissometer instruments varied by <15%. However, measurements of BC were as much as 52% greater than EC determined by thermal-optical techniques. Gravimetric data from the current study suggest that the thermal-optical measurements of EC likely underestimated the carbon in flame soot samples, indicating an inability to close a carbon mass balance.