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The mass and light absorption contributions of organic carbon (OC), elemental carbon (EC), and mineral dust influence glacial melting and potentially contribute to climate change over the high Himalayas and Tibetan Plateau (HTP). Plateau-scale investigations of these components and their respective light absorption are limited due to the high altitude. In this study, we combined the analysis of major light-absorbing substances and their corresponding multiwavelength absorption to determine their specific contributions firstly. We investigated the spatial variations of total suspended particle (TSP) mass across the HTP, noting high contributions from dust, carbonaceous components, and secondary inorganic aerosols (SNA, including sulfate, nitrate, and ammonium). Enhanced levels of primary and secondary OC and SNA were observed in the marginal areas of the HTP, associated with high relative humidity (RH) and OX levels (O 3 +NO 2). EC was the primary contributor to light absorption, accounting for approximately 68%, 46%, and 64% in Ngari, Qinghai Lake, and Beiluhe, respectively. We found higher light-absorbing contributions from carbonaceous aerosols in the marginal areas compared to the central HTP site, particularly during the heating seasons (∼90%). Fugitive dust significantly contributed to TSP mass but not to light absorption. The concurrent constraints on the mass and optical properties of OC, EC, and dust in this study can help reduce uncertainties in climate models specific to the HTP. [Display omitted] • The dominant light-absorbing was attributed to EC in the HTP. • Enhanced carbonaceous aerosol light-absorbing contributions were obtained in the HTP margin area. • Fugitive dust was an important contributor to aerosol mass, while not for light absorption. [ABSTRACT FROM AUTHOR]

Within the scope of this study, two equivalent PM 2.5 samplers were designed and developed to eliminate sampling artifacts in the results of atmospheric particulate organic carbon (OC) and particulate polycyclic aromatic hydrocarbons (PAH) caused by volatile organic compounds (VOCs) and gas phase PAH compounds, respectively. A mass loss of less than 10% due to the denuders was observed. Study results showed that if an impregnated denuder is not used, the results of atmospheric particle OC concentrations will be reported with higher values due to positive errors of 53.2 ± 7.23% (median: 52.00%) on average. It was observed that the total error (net error) was still positive, but decreased to an average of 35.1 ± 16.8% (median: 31.0%) after including the negative errors quantified from the backup filter into the calculation. In cases where denuders were not used in the sampling, it was observed that the results with positive errors of 41.0 ± 14.6% (median: 33.8%) on average would be obtained for the total PAHs. Ozone-induced negative interference was the highest in Acenapthylene (28%), followed by Fluoranthane (20%), Phenanthrene (18%), and 15% for Np and Benzo[g,h,i]perylene compounds, relative to their medians. Negative errors of 10% or less were found in all other individual PAH compounds. [Display omitted] • Particulate OCs have been reported in overestimated amounts as much as 53%. • Organic denuder and backup filters reduced VOC artifacts to 35.1%. • Ultrafine particulates were detected in the backup filter. • Measured OCs in the backup filters must be added to OCs in the primary filter. • OC loss from the primary filter increased as the ambient temperature increases. [ABSTRACT FROM AUTHOR]

Air pollution in upper Southeast Asia (SEA) has become critical particularly regarding atmospheric particles. This study aims to investigate the sources and formation of fine size-fractionated particulate matters (FSPMs), as well as their potential impact on climate. Particulate matter in three size ranges (2.1–1.1 μm, 1.1–0.65 μm, and 0.65–0.43 μm) was collected using cascade impactors in rural Chiang Dao (CD) and urban Chiang Mai (CM) during the smoke haze period (March–April 2019) in Chiang Mai, Thailand. The average concentration of FSPM was approximately 1.3 times higher in rural CD (88 ± 34 μg/m³) than in urban CM (66 ± 26 μg/m³). Both areas showed significantly higher concentrations of finer particles, with rural CD detecting 41 ± 17 μg/m³ (46% of FSPM) and urban CM presenting 27 ± 11 μg/m³ (41% of FSPM). Total carbon (TC) concentrations, including organic carbon (OC) and elemental carbon (EC), showed the same pattern as PMs. The most abundant fractions, including OC3 (32–45% of total OC) and EC1 (91–100% of total EC) in FSPM samples, particularly in fine particles (PM1), suggest that biomass burning was the primary source. Source classification based on diagnostic ratios of polycyclic aromatic hydrocarbons (PAHs), OC/EC ratios, combined with primary and secondary formations, revealed that PM 2.1-1.1 was influenced by biomass burning and secondary organic carbon (SOC), while PM 0.65-0.43 originated from both SOC and vehicular emissions. PM 1.1-0.65 in the rural area was probably caused by SOC and other mixed sources, whereas SOC and vehicular emissions were the main source in urban CM. With respect to the effective carbon ratio (ECR), lower values were observed in finer particles (0.37 ± 0.15 in rural CD and 0.36 ± 0.38 in urban CM), suggesting enhanced light-absorbing properties of fine particulate matter during the haze period in the upper SEA region. [ABSTRACT FROM AUTHOR]

• PM<0.1 µm contained more than 50% of OC, EC fractions. • Emissions of PM<0.1 µm were dominated by OC2. • OC2 was expected to be a marker of biomass combustion. • High lignin content in biomass might be responsible for high OC/EC and PyOC values. • Cl−, Cr, Ca, Cd, Ni, Na and Mg have potential as source indicators. Atmospheric nanoparticles (PM < 0.1 µm) are a major cause of environmental problems and also affect health risk. To control and reduce these problems, sources identification of atmospheric particulates is necessary. Combustion of bituminous coal and biomass including rubber wood, palm kernel, palm fiber, rice stubble, rice straw, maize residue, sugarcane leaves and sugarcane bagasse, which are considered as sources of air quality problems in many countries, was performed. Emissions of particle-bound chemical components including organic carbon (OC), elemental carbon (EC), water-soluble ions (NH 4 +, Cl−, NO 3 −, SO 4 2−), elements (Ca, K, Mg, Na) and heavy metals (Cd, Cr, Ni, Pb) were investigated. The results revealed that PM < 0.1 µm from all samples was dominated by the OC component (>50%) with minor contribution from EC (3%-12%). The higher fraction of carbonaceous components was found in the particulates with smaller sizes, and lignin content may relate to concentration of pyrolyzed organic carbon (PyOC) resulting in the differences of OC/EC values. PM emitted from burning palm fiber and rice stubble showed high values of OC/EC and also high PyOC. Non-carbonaceous components such as Cl−, Cr, Ca, Cd, Ni, Na and Mg may be useful as source indicators, but they did not show any correlation with the size of PM. [Display omitted] [ABSTRACT FROM AUTHOR]

Mercury-contaminated fish are a serious problem in the Great Lakes basin, because mercury is a potent neurotoxin that poses a danger to both humans and wildlife. Lake Superior lake trout and walleye have the highest mercury concentrations of the five Great Lakes. Because the atmosphere is the major source of mercury to the Great Lakes, information on the over-water mercury concentration is essential to model the mercury biogeochemical cycle. For the first time in the peer-reviewed literature, this paper presents total gaseous mercury (TGM) measurements made over Lake Superior and Lake Michigan. The Lake Superior aircraft measurements were made at an altitude of 300 m, and the Lake Michigan aircraft measurements at a variable altitude of 30–300 m. The over-water Lake Superior TGM of 1.02 ± 0.34 ng/m3 is much lower than the TGM from nine stations in the Canadian Atmospheric Mercury Measurement Network (CAMNet) and six stations in the Atmospheric Mercury Network (AMNet). The land-based TGM concentrations average range from 1.25 to 1.75 ng/m3 which are in good agreement with current global average values of 1.3–1.6 ng/m3. The over-water Lake Michigan TGM is 1.65 ± 0.61 ng/m3. We also present Lake Superior over-water measurements of volatile organic compounds (VOC), ozone (O 3), nitrogen oxide (NO y), and particulate matter. Elemental carbon (EC) is a tracer for mercury because mercury is released during the combustion of coal. EC is significantly correlated with TGM over both Lake Superior and Lake Michigan. TGM over Lake Michigan is also significantly correlated with organic carbon, sulfate, nitrate and ammonium. [ABSTRACT FROM AUTHOR]

Elemental carbon (EC) and metals are two important parts of atmospheric black carbon (BC). However, little information is available regarding the interaction between them and its impacts on the reactive oxygen species (ROS) formation and physiological antioxidants depletion. In this study, we chose six most frequently detected metals (Cu(Ⅱ), Fe(Ⅲ), Mn(Ⅱ), Cr(Ⅲ), Pb(Ⅱ) and Zn(Ⅱ)) in BC and examined their interactions with EC in the ROS generation and glutathione (GSH) oxidation. Results showed that only Cu(Ⅱ) and EC synergically promoted the GSH oxidation and hydroxyl radical (•OH) generation. Other five metals had negligible effects on the GSH oxidation regardless of the presence or absence of EC. The synergistic interaction between Cu(Ⅱ) and EC could be attributed to the superior electrical conductivity of EC. In the process, EC transferred electrons from the adjacent GSH to Cu(Ⅱ) through its graphitic carbon framework to yield Cu(Ⅰ) and GSH radical. Cu(Ⅰ) further reacted with dioxygen to generate •OH, which eventually led to the oxidation of GSH. Our results revealed a new driving force inducing the ROS formation and GSH depletion as well as provided novel insights into the risk assessment of BC. [Display omitted] • Cu(Ⅱ) and elemental carbon (EC) synergistically accelerated glutathione (GSH) oxidation. • Cu(Ⅱ) and EC synergistically promoted the hydroxyl radical generation. • Other metals mixed with EC had no synergistic effect on the GSH oxidation. • EC transferred electron from GSH to Cu(Ⅱ) and promoted the GSH oxidation. [ABSTRACT FROM AUTHOR]

• Methanol-diesel blends reduced total carbon drastically by up to 94 %. • 4 ring structured PAHs contributed maximum concentration in total PAHs for tested alcohol blends. • 5 ring structured PAHs (B[a]P and D[a,h]A) contributed maximum to toxicity equivalent potential. • DE5 and DB5 resulted in highest and lowest toxicity potential with ∼262 and ∼179B[a]P equivalent respectively. • cPAHs contributed maximum (>95 %) in total toxicity potential. Methanol, ethanol and butanol have emerged as an important alternative fuel for combustion engines due to their inherent advantages like lower particulate matter emission, renewability and lower greenhouse gas emissions in comparison to conventional diesel. Unregulated emission like elemental carbon (EC), organic carbon (OC) and polycyclic aromatic hydrocarbons (PAHs) in the exhaust are important aspects as these components are prone to have carcinogenic effects. The present study deals with the detailed analysis of EC, OC and individual PAHs determination in particulate matter samples of alcohol-diesel blends (methanol, ethanol, butanol and diesel; M, E, B and D) with varying oxygen mass fractions of 2.5% and 5%. The study revealed that methanol-diesel blends (DM2.5 and DM5) reduced the total carbon by ∼94% and ∼77% whereas DB5 (∼35%) was found to be least effective. DM2.5 also reduced the 4 ring structured PAHs by 6 folds in comparison to diesel while DE5 increased the 5 ring structured PAHs by ∼35% which carry higher toxicity potential. DE5 showed the highest toxicity potential of ∼262 benzo[a]pyrene (B[a]P) equivalent in comparison to toxicity potential of ∼224 B[a]P equivalent of diesel for their sampled particulate matters. [ABSTRACT FROM AUTHOR]

The U. S. Environmental Protection Agency in collaboration with the U. S. Air Force Arnold Engineering Development Complex conducted the VAriable Response In Aircraft nvPM Testing (VARIAnT) 3 and 4 test campaigns to compare nonvolatile particulate matter (nvPM) emissions measurements from a variety of diffusion flame combustion aerosol sources (DFCASs), including a Cummins diesel engine, a diesel powered generator, two gas turbine start carts, a J85-GE-5 turbojet engine burning multiple fuels, and a Mini-CAST soot generator. The VARIAnT research program was devised to understand reported variability in the ARP6320A sampling system nvPM measurements. The VARIAnT research program has conducted four test campaigns to date with the VARIAnT 3 and 4 campaigns devoted to: (1) assessing the response of three different black carbon mass analyzers to particles of different size, morphology, and chemical composition; (2) characterizing the particles generated by 6 different combustion sources according to morphology, effective density, and chemical composition; and (3) assessing any significant difference between black carbon as determined by the 3 mass analyzers and the total PM determined via other techniques. Results from VARIAnT 3 and 4 campaigns revealed agreement of about 20% between the Micro-Soot Sensor, the Cavity Attenuated Phase Shift (CAPS PM SSA) monitor and the thermal-optical reference method for elemental carbon (EC) mass, independent of the calibration source used. For the LII-300, the measured mass concentrations in VARIAnT 3 fall within 18% and in VARIAnT 4 fall within 27% of the reference EC mass concentration when calibrated on a combustor rig in VARIAnT 3 and on an LGT-60 start cart in VARIAnT 4, respectively. It was also found that the three mass instrument types (MSS, CAPS PM SSA , and LII-300) can exhibit different BC to reference EC ratios depending on the emission source that appear to correlate to particle geometric mean mobility diameter, morphology, or some other parameter associated with particle geometric mean diameter (GMD) with the LII-300 showing a slightly stronger apparent trend with GMD. Systematic differences in LII-300 measured mass concentrations have been reduced by calibrating with a turbine combustion as a particle source (combustor or turbine engine). With respect to the particle size measurements, the sizing instruments (TSI SMPS, TSI EEPS, and Cambustion DMS 500) were found to be in general agreement in terms of size distributions and concentrations with some exceptions. Gravimetric measurements of the total aerosol mass produced by the various DFCAs differed from the reference EC, BC and integrated particle size distribution measured aerosol masses. The measurements of particle size distributions and single particle analysis performed using the miniSPLAT indicated the presence of larger particles (≳150 nm) having more compact morphologies, higher effective density, and a composition dominated by OC and containing ash. This increased large particle fraction is also associated with higher values of single scattering albedo measured by the CAPS PM SSA instrument and higher OC measurements. These measurements indicate gas turbine engine emissions can be a more heterogeneous mix of particle types beyond the original E−31 assumption that engine exit exhaust particles are mainly composed of black carbon. • PA and CAPS BC mass measurement methods have less variability than the LII BC method. • Gravimetric mass 30–40% greater than reference EC and 50–60% greater than BC masses. • Secondary particle mode >150 nm was observed dominated by non-volatile OC and containing ash. • Calibration of LII with a turbine combustion source more effective than other methods. [ABSTRACT FROM AUTHOR]

Occupational exposure to diesel exhaust is regulated by legislation in Europe owing to its carcinogenic effects on humans. In underground mines, exposure to diesel exhaust requires regular monitoring. In this work, we investigate the usage of aethalometer AE33 and portable micro-aethalometer MA200 to assess occupational exposure to diesel exhaust in two underground mines. These instruments provide continuous data on wavelength-dependent particle light absorption, and based on this, equivalent black carbon (eBC) particle concentrations and potential sources. Both aethalometers correlated well with the thermal-optical elemental carbon analysis. Time-resolved aethalometer data revealed work-activity-dependent eBC concentration patterns that can be beneficial for identifying work phases that are significant for occupational exposure. In particular, high eBC peak exposures were observed for workers near load haul dumping areas. The diesel soot mass absorption cross-sections determined were similar for both mines. The absorption Ångström exponent determined from the aethalometer data was suitable for detecting and assessing the contributions of other potential sources to eBC concentrations, such as tobacco smoke, which is often prevalent in work environments. Overall, the portable micro-aethalometers proved to be suitable for monitoring occupational diesel exhaust exposure and can be useful for designing targeted exposure prevention measures in mining environments. • Aethalometers were used to monitor diesel exhaust exposure in underground mines. • Aethalometers AE33 and MA200 correlated well with elemental carbon analysis. • Micro-aethalometers provided data to identify work phases leading to high exposure. • High exposure peaks were measured from workers working near load haul dump area. • Aethalometer data enables separation of tobacco smoke and diesel exhaust exposure. [ABSTRACT FROM AUTHOR]

The impact of organic carbon (OC) on the light absorption of soot is determined by discrete element modeling coupled with the discrete dipole approximation for computing the scattering of radiation by soot particles. The mass absorption cross-section (MAC) of soot is used widely to determine its light absorption. Typically MAC is obtained from the mass average refractive index of OC and elemental carbon (EC) with large C/H that make up mature soot. As such, MAC can be overestimated by a factor of 3 in fuel-rich flames where newly-formed young soot contains EC with small C/H and OC that predominantly scatters light reducing its absorption by soot. Here a relation for the soot refractive index is derived accounting for soot morphology, maturity and OC content through its band gap at wavelength, λ = 266–1064 nm. Using this relation, the MAC of soot containing OC (up to 50 wt%) is in excellent agreement with carbon black, graphene and soot data. This confirms that soot morphology, maturity and OC content greatly influence light absorption during characterization of in-flame and freshly-emitted soot by laser induced incandescence and light extinction, especially in fuel-rich flames, and need to be properly accounted for in the soot refractive index. Image 1 [ABSTRACT FROM AUTHOR]

Characteristics of carbonaceous aerosol (CA) and its light absorption properties are limited in Karachi, which is one of the most polluted metropolitan cities in South Asia. This study presents a comprehensive measurement of seasonality of CA compositions and mass absorption cross-section (MAC) of elemental carbon (EC) and water-soluble organic carbon (WSOC) in total suspended particles (TSP) collected from February 2015 to March 2017 in the southwest part of Karachi. The average TSP, organic carbon (OC), and EC concentrations were extremely high with values as 391.0 ± 217.0, 37.2 ± 28.0, and 8.53 ± 6.97 μg/m3, respectively. These components showed clear seasonal variations with high concentrations occurring during fall and winter followed by spring and summer. SO 4 2−, NO 3 −, K+, and NH 4 + showed similar variations with CA, implying the significant influence on atmospheric pollutants from anthropogenic activities. Relatively lower OC/EC ratio (4.20 ± 2.50) compared with remote regions further indicates fossil fuel combustion as a primary source of CA. Meanwhile, sea salt and soil dust are important contribution sources for TSP. The average MAC of EC (632 nm) and WSOC (365 nm) were 6.56 ± 2.70 and 0.97 ± 0.37 m2/g, respectively. MAC EC is comparable to that in urban areas but lower than that in remote regions, indicating the significant influence of local emissions. MAC WSOC showed opposite distribution with EC, further suggesting that OC was significantly affected by local fossil fuel combustion. In addition, dust might be an important factor increasing MAC WSOC particularly during spring and summer. Image 1 [ABSTRACT FROM AUTHOR]

Carbonaceous aerosols affect atmospheric radiation and visibility and endanger human health. Administrative border and topography have created significant research interests focused on Yunnan Province. We studied the chemical characteristics and sources of OC and EC in four Yunnan cities using manual sampling and positive definite matrix factorization (PMF). Backward trajectories, cluster analysis, potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) were used to evaluate the transport pathways and potential source of carbonaceous aerosols during spring. The impacts of the transport of Biomass burning (BB) emissions in Southeast Asia and incomplete combustion on carbonaceous aerosols were highlighted in the study. Daily PM 2.5 concentration ranged from 12.00 μg/m3 to 91.50 μg/m3, with the average concentration of 34.03 ± 13.49 μg/m3. OC and EC accounted for 19.85–44.94 % and 4.99–13.16 % of PM 2.5. Average secondary organic carbon (SOC) concentration ranged from 0.82 μg/m3 ∼ 6.42 μg/m3, exhibiting the highest secondary conversion rate in autumn. BB was identified as the largest single source of carbonaceous aerosols through PMF analysis. The results of backward trajectory showed that more than 63.68 % of air mass originated from Myanmar in spring, and Myanmar, Laos and Vietnam were identified as the major potential source areas by PSCF and CWT. Biomass plumes emitted by some Southeast Asian countries in the spring are likely to be transported to the Yunnan Province under the guidance of southwest winds, thereby affecting local carbonaceous aerosols. The proportions of OC and EC in PM 2.5 of the Yunnan Plateau were found higher than those in the four plains of China (Northeast Plain, North China, Middle-Lower Yangtze, and Guanzhong Plain). Incomplete combustion caused by low oxygen concentrations at high altitudes was considered as the cause. [Display omitted] • Carbonaceous aerosols in the Southwest plateau of China were studied. • The OC and EC content in PM 2.5 is higher with low oxygen. • Biomass Burning contributes largely to OC and EC in spring. [ABSTRACT FROM AUTHOR]

Organic carbon (OC) and elemental carbon (EC) concentrations were measured in PM 1 and PM 10 daily samples collected at an urban station in Elche (southeastern Spain) from February 2015 to February 2018. The effect of seasonal weather conditions, traffic, and specific pollution events (Saharan dust outbreaks and local pollution episodes) on the variability of carbonaceous aerosol levels was studied in this work. The joint contribution of carbonaceous species to PM 1 and PM 10 mass concentrations was, respectively, 48% and 26%. Both OC and EC concentrations were higher in winter than in summer because of the poor dispersion conditions and lower temperatures leading to the condensation of semivolatile species. Secondary organic carbon (SOC), estimated using the EC tracer method, also exhibited higher concentrations during winter, indicating that the prevailing meteorological conditions during the cold season are more favorable for the formation of secondary organic aerosols. Our results suggest different formation pathways of secondary organic components during summer and winter. At the sampling site, EC was primarily derived from traffic emissions, independently of the season and the type of event, with a modest contribution from biomass burning (<20%). The estimated contribution from this source to OC levels was similar. Local pollution episodes lead to a significant increase in the concentrations of carbonaceous species, in particular of SOC, influencing its temporal variation. On average, African dust outbreaks showed a moderate impact on the levels of carbonaceous aerosols; however, the effect was significantly stronger during winter Saharan events. • EC mainly emitted from traffic, with a minor influence of biomass burning. • SOA production more affected by weather conditions than by photochemistry. • Significant increases of carbonaceous species during local pollution events (LPE). • Meteorological conditions during LPE especially suitable for SOA formation. • Important increases of SOC levels during winter Saharan events. [ABSTRACT FROM AUTHOR]

Secondary organic carbon (SOC) is known to account for a substantial fraction of fine-mode carbonaceous aerosol. Owing to a limited understanding of SOC formation processes and the absence of direct measurement methods, SOC concentrations are mostly estimated using a tracer-based method utilizing either elemental carbon (EC) or carbon monoxide (CO) as tracers. The performance of these tracer-based methods depends heavily on accurate determination of the (OC/Tracer) pri value. The minimum R squared (MRS) method is currently recognized as a relatively reasonable tool to determine (OC/Tracer) pri. This study estimated SOC based on the MRS method with EC and CO as tracers, followed by the Monte Carlo method to analyze quantitatively the effects of measurement uncertainty, emission scenario and sample size on SOC estimates. We report here four major findings: i) the concentration of O 3 was used as an indicator to atmospheric secondary reaction potential, and it was found that the mass proportion of SOC in total OC estimated by CO as the tracer is more consistent with the seasonality of actual secondary reaction potential; ii) the estimation results are highly sensitive to the measurement uncertainty in different emission scenarios, which leads us to conclude that the CO tracer method is more robust than the EC tracer method due to large inherent uncertainties in current EC measurements; iii) oversimplification of emission scenarios has substantial impacts on the estimated SOC value, and careful evaluation of the interdependence between sources should be performed to minimize this bias; and iv) the estimation bias of SOC can be reduced by increasing the sample size, and the tracer method can be expected to generate robust results for sample sizes over 1000. These findings are important in terms of providing a reference to choose appropriate tracers, emission scenarios and sample sizes for robust estimation of SOC in future studies. Unlabelled Image • Sensitivity of SOC estimation by CO and EC tracer methods studied • SOC fraction based on CO method consistent with atmospheric oxidation capacity • SOC estimation sensitive to measurement uncertainty and CO method is more robust. • Oversimplification of emission scenarios enhances uncertainty in SOC estimation. • Sample size >1000 markedly increases the reliability of estimates. [ABSTRACT FROM AUTHOR]

Carbonaceous aerosols (CAs) scatter and absorb incident solar radiation in the atmosphere, thereby influencing the regional climate and hydrological cycle, particularly in the Third Pole (TP). Here, we present the characteristics of CAs at 19 observation stations from the Atmospheric Pollution and Cryospheric Change network to obtain a deep understanding of pollutant status in the TP. The organic carbon (OC) and elemental carbon (EC) concentrations decreased noticeably inwards from outside to inland of the TP, consistent with their emission load and also affected by transport process and meteorological condition. Urban areas, such as Kathmandu, Karachi, and Mardan, exhibited extremely high OC and EC concentrations, with low and high values occurring in the monsoon and non-monsoon seasons, respectively. However, remote regions inland the TP (e.g., Nam Co and Ngari) demonstrated much lower OC and EC concentrations. Different seasonal variations were observed between the southern and northern parts of the TP, suggesting differences in the patterns of pollutant sources and in distance from the sources between the two regions. In addition to the influence of long-range transported pollutants from the Indo-Gangetic Plain (IGP), the TP was affected by local emissions (e.g., biomass burning). The OC/EC ratio also suggested that biomass burning was prevalent in the center TP, whereas the marginal sites (e.g., Jomsom, Dhunche, and Laohugou) were affected by fossil fuel combustion from the up-wind regions. The mass absorption cross-section of EC (MAC EC) at 632 nm ranged from 6.56 to 14.7 m2 g−1, with an increasing trend from outside to inland of the TP. Urban areas had low MAC EC values because such regions were mainly affected by local fresh emissions. In addition, large amount of brown carbon can decrease the MAC EC values in cities of South Asia. Remote sites had high MAC EC values because of the coating enhancement of aerosols. Influenced by emission, transport process, and weather condition, the CA concentrations and MAC EC presented decreasing and increasing trends, respectively, from outside to inland of the TP. Image 1 • CA concentrations decrease remarkably inwards from outside to inland of the TP. • CA seasonal variation suggest a different source pattern between south and north parts of TP. • The TP is affected by local biomass burning in addition to long-range transport pollutants. • MAC EC increase from outside to inland of the TP because of aging and coating processes. [ABSTRACT FROM AUTHOR]

Abstract The water-soluble ions and carbonaceous compounds of PM 1 were measured at the King Sejong Station (KSG) in the northern part of Antarctic Peninsula from March to November in 2009. As the sum of all measured species including organic matter [OM; organic carbon (OC)*1.9], the PM 1 mass reached a maximum of 936 ng m−3 with the mean of 686 ± 226 ng m−3. The most abundant constituents were OM (389 ± 109 ng m−3) and sea-salts (Na+ and Cl−, 193 ± 122 ng m−3), which comprised 85% of the PM 1 mass. In contrast, the contribution of SO 4 2− was below 1% and its depletion relative to Na+ was prevalent particularly during winter, which was attributed to the frost flowers on newly formed sea-ice surface. The OC concentration was the highest in fall and its subcomponents OC2 and OC3 were moderately correlated with sea-salts (r = 0.5), indicating the marine biogenic source for OC. The elemental carbon (EC) concentration was much lower than OC, leading to the mean OC/EC ratio over 10. While the charred fraction of EC (EC1) was elevated by the long-range transport of biomass burning plume from nearby continent, the mass fraction of soot-EC (EC23) was increased concurrently with enhanced NO 3 −, suggesting EC23 as a good indicator for local influence in pristine environments like Antarctic region. Graphical abstract Unlabelled Image Highlights • OM and sea-salts comprised 85% of the PM 1 (686 ± 226 ng m−3) at the KSG. • The OC/EC ratio was greater than 10 with biogenic source for OC from the ocean. • Char-EC was enhanced in biomass burning-impacted air from nearby continent. • Soot-EC is a good tracer indicating local influence in Antarctic environment. [ABSTRACT FROM AUTHOR]

The adsorption of polycyclic aromatic hydrocarbons (PAHs) by components such as elemental carbon (EC), total organic carbon (TOC), and particles is different, and EC and PAHs are good materials for reconstructing historical human activity patterns and pollution conditions. In this study, the effects of EC (soot and char), TOC and particles of different grain size on PAHs in surface sediments were quantitatively analysed, and their historical concentrations in a sediment core from western Taihu Lake were reconstructed. The contents of soot, TOC, clay, EC and char explained 57.2%, 27.6%, 26.0%, 24.0% and 16.4%, respectively, of the PAH concentrations in surface sediments. The correlation between the soot and PAH levels was significantly higher than that between the char, TOC, and clay contents and PAH levels, and PAHs were mainly affected by the local economic development and human activity, as indicated by metrics of population, highway mileage, coal burning, and industrial output. With the development of the economy of the Taihu Lake Basin, the composition of PAHs in the sediments has changed: the proportion of low-molecular-weight PAHs decreased from 42.4% to 17.5%, and that of high-molecular-weight PAHs increased from 58.7% to 82.5%. The concentration of PAHs in pore water from Taihu Lake over the past 100 years was reconstructed and ranged from 43.1 to 961.2 μg L−1, with an average of 180.7 μg L−1. After China's reform and opening up, the concentrations of various PAHs in Taihu Lake changed from safe to chronic pollution levels. The ratios of lead (Pb) isotopes and the diagnostic ratios of PAHs showed that the main sources of PAHs in western Taihu Lake sediments were human activities such as coal and petroleum combustion. Image 1 • The effects of EC, soot, char, TOC and particles of different grain size on PAHs were quantitatively analysed. • The material sources of PAHs in Taihu Lake from the perspective of Pb isotopes were explored. • The concentration of PAHs in Taihu Lake water over the past 100 years was reconstructed. [ABSTRACT FROM AUTHOR]

Carbonaceous aerosols are linked to severe haze and health effects, while its origins remain still unclear over China. PM 2.5 samples covering four seasons from Jan. 2016 to Jan. 2017 were collected at six sites in Chifeng, a representative agro-pastoral transitional zone of North China focusing on the characteristics and sources of organic carbon (OC) and elemental carbon (EC). The annual averages of OC, EC were 9.00 ± 7.24 μg m−3, 1.06 ± 0.79 μg m−3 with site Songshan in coal mining region exhibited significantly enhanced levels. The residential heating emissions, air stagnation, and secondary organic formation all contributed the higher OC, EC levels in winter. Meanwhile, the impacts from open biomass burning were most intensive in spring. The retroplumes via Lagrangian model highlighted a strong seasonality of regional sources which had more impacts on EC increases. The Positive Matrix Factorization (PMF) model resolved six primary sources, namely, coal combustion, biomass burning, industrial processes, oil combustion, fugitive dust, and fireworks. Coal combustion and biomass burning comprised large fractions of OC (30.57%, 30.40%) and EC (23.26%, 38.47%) across the sites, while contributions of industrial processes and oil combustion clearly increased in the sites near industrial sources as smelters. PMF and EC tracer method gave well correlated (r =0.65) estimates of Secondary OC (SOC). The proportion of coal combustion and SOC were more enhanced along with PM 2.5 elevation compared to other sources, suggesting their importances during the pollution events. Image 1 • OC, EC displayed distinct spatial variations due to influence from local sources. • Regional sources had obvious seasonal variation and more influence on EC. • PMF identified two main sources, coal combustion and biomass burning. [ABSTRACT FROM AUTHOR]

The estimation of emissions inventories of climate forcing species and air pollutants from activities such as the burning of biomass from cooking food in rural environments in Mexico presents some degree of uncertainty due to the lack of locally obtained emission factors; emissions estimates were generally obtained with other types of biomass and cookstoves. This study presents a controlled dilution system to obtain emission factors for gases (CO 2 , CH 4 , CO, NMHC, NOx, and SO 2) and PM 2.5 (and its components, elemental carbon (EC) and organic carbon (OC)) from improved wood-burning stoves. The sampling experiment combines measurements of PM 2.5 and gases from a diluted stream of emissions, with carbon mass balance methods and concentration ratios of CO 2 and CO to obtain average emission factors under the Water Boiling Test (WBT) protocol. The feasibility of the experimental design is demonstrated by an application of using white oak wood as fuel in an improved Patsari stove. The ranges of average emission factors obtained for the Patsari stove in g/kg of wood consumed for four representative species were: CO 2 , 1305–1423; OC, 1.47–2.07; EC, 0.13–0.17; PM 2.5 , 1.97–4.19, and are within the ranges reported in the literature. • We determine CO 2 , OC, EC, and PM 2.5 emission factors from improved wood-burning cookstoves at ˜1,900 masl. • This experiment consisted in the sampling and monitoring of a diluted stack effluent under the Water Boiling Test (WBT). • The measured average emission factors of the species studied are within the ranges reported in similar studies using WBT. • The results supply to the development of a larger emission factors database for wood-burning cookstoves at high elevations. • The use of emission factors can help to reduce the uncertainty of corresponding emission inventories for improved cookstoves. [ABSTRACT FROM AUTHOR]

Abstract Black carbon (BC) is important due to its complex influences on the environment and on climate in particular. However, reported BC data are largely dependent on measurement techniques due to the multitude of measurement principles. Here we focused on thermal-optical method which has been widely used to determine BC mass (as elemental carbon, EC). Several factors influencing EC measurement were investigated. Results from source samples representing vehicle engine emissions pointed to a continuum of EC components in thermal stability and provided direct observational evidence for the premature evolution of EC in inert atmosphere. It was also found that EC masses may be substantially underestimated for the vehicle exhaust samples if the adopted protocol requires an oxidizing atmosphere to define the split point between organic carbon (OC) and EC. Results from a field campaign conducted during winter in Beijing showed that the optical attenuation (ATN; i.e., the filter transmittance signal, I) was largely saturated for the samples with relatively high loadings, indicating their EC results were unreliable. Improved measurement of EC was achieved by extracting these heavily loaded filters using methanol, given that ATN was considerably reduced by the extraction and, moreover, saturation of ATN (or I) became not evident for the extracted samples. The methanol extraction also significantly reduced the transformation of OC to char-OC, by removing the majority (i.e., ~85%) of the deposited organic aerosols. Higher EC were measured for the extracted samples compared with the untreated ones, indicating that EC tends to be underestimated due to the charring-induced uncertainties. In addition, the methanol extraction largely reduced the inter-protocol discrepancy in the EC measurement results. Similar effects of methanol extraction have been observed during summer in Beijing, despite the seasonal variations of aerosol sources and compositions. This study indicates the potential benefits of methanol extraction for EC measurement. Graphical abstract Unlabelled Image Highlights • There likely exists a continuum of EC components in thermal stability. • The ATN vs. EC loading dependence is an useful indicator for evaluating EC results. • EC measurements can be highly uncertain for heavily-loaded filters. • Methanol extraction of heavily-loaded filters leads to more reliable EC results. • Refined EC measurements have implications for SOA estimation by EC tracer method. [ABSTRACT FROM AUTHOR]

Abstract To assess the factors influencing indoor exposure from outdoor PM 2.5 -bounded elemental carbon (EC), we developed a Monte Carlo framework to investigate the ambient exposure factor (the ratio of exposure concentration to ambient concentration) of PM 2.5 -bounded EC. The framework integrates outdoor PM 2.5 -bounded EC concentrations, the probability of window opening, dependence on outdoor parameters (temperature, humidity, wind speed, PM 2.5 concentration), EC infiltration factors, and population time-activity patterns. We investigated the population exposure in Beijing, which suffers from heavy air pollution, from January 1, 2013 to December 31, 2015. The average population exposure to outdoor PM 2.5 -bounded EC modified by ambient exposure factor was 2.24 μg/m3 (95% confidence interval (CI):1.06–4.30 μg/m3) in winter, 1.91 μg/m3 (CI:1.43–2.74 μg/m3) in the transition seasons, 1.53 μg/m3 (CI:1.51–1.56 μg/m3) in summer, 2.92 μg/m3 (CI:2.02.–4.53 μg/m3) on haze days, and 1.02 μg/m3 (CI:0.82–1.39 μg/m3) on non-haze days. Increases in outdoor temperature and humidity increased ambient exposure factors, whereas an increase in outdoor PM 2.5 concentration decreased the ratio of exposure concentration to ambient concentration. This implies that lower temperatures in winter and higher PM 2.5 concentrations on haze days result in a population exposure to a lower proportion of outdoor PM 2.5 -bounded EC. Graphical abstract Image 1 Highlights • The concentration of outdoor EC was measured daily from 2013 to 2015 in Beijing. • A daily time resolution model of population exposure to EC was developed. • Outdoor temperature/RH, wind speed and PM2.5 concentrations influence the difference in ambient exposure factors. [ABSTRACT FROM AUTHOR]

Abstract The atmospheric concentration of elemental carbon (EC) in aerosol particles is a key parameter related to global warming and health effects. Emission regulations for diesel exhaust intended to reduce EC concentrations have been strengthened in recent years. To investigate regulation effects in Japan, daily EC concentrations in the megacity of Nagoya, central Japan, were measured during April 2003–March 2016. The EC concentrations showed a decreasing trend with changing seasonal variation: high concentrations were found in autumn and winter before 2011, but no seasonal variation was discernible after 2012. Strong correlation was found for annual vehicular EC emissions and annual mean EC concentrations during 2003–2009. However, the relation after 2010 was weaker in spring and summer. Based on the relation of EC with trace element (Pb, V, Sb, etc.) concentrations and the backward air trajectories on high concentration days, EC sources other than vehicles were found to be related to long-range transport of air pollution from China in spring and combustion of heavy oil, including ship engine exhaust, in summer. Highlights • Elemental carbon sources other than vehicles were discussed with tracer elements. • Daily EC concentrations were measured at Nagoya, Japan, during 2003–2016. • The decreasing trend of EC concentrations changed around 2010. [ABSTRACT FROM AUTHOR]

Abstract Radiocarbon (14C) analysis is a powerful tool that can unambiguously distinguish fossil and non-fossil sources of carbonaceous particles. However, one of the big challenges of this method is to isolate elemental carbon (EC) or black carbon (BC) for 14C analysis. Hydropyrolysis (hypy) has proven to be an effective method for separating BC in environmental matrices. The potential of hypy for isolation of EC from atmospheric aerosols is evaluated using typical combustion products from non-fossil (biomass), fossil fuel (coal and petroleum), and ambient aerosol samples collected in Beijing and Guangzhou. Using solid state nuclear magnetic resonance (NMR) along with measurement of carbon content and 14C, hypy conditions of 15 MPa hydrogen pressure and 550 °C temperature was confirmed to effectively separate EC from aerosol samples. Consequently, a comparison study of EC 14C in aerosol samples separated using the two-step heating method (CTO-375), thermal-optical method and hypy was conducted. The results show that hypy is an effective and stable approach for matrix-independent 14C quantification of EC in aerosols. Graphical abstract Image 1 Highlights • The potential of hypy for isolation of EC from atmospheric aerosols was evaluated. • Hypy conditions were confirmed to effectively separate EC from aerosol samples. • A comparison study shows that hypy is a matrix-independent 14C quantification approach of EC in aerosols. [ABSTRACT FROM AUTHOR]

Abstract 75 paired TSP and PM 2.5 samples were collected over four seasons on Huaniao Island (HNI), an island that lies downwind of continental pollutants emitted from mainland China to the East China Sea (ECS). These samples were analyzed for organic carbon (OC) and elemental carbon (EC), with a special focus on char-EC (char) and soot-EC (soot), to understand their sources, and the scale and extent of pollution and dry deposition over the coastal ECS. The results showed that char concentrations in PM 2.5 and TSP averaged from 0.13 to 1.01 and 0.31–1.44 μg m−3; while for soot, they were from 0.03 to 0.21 and 0.16–0.56 μg m−3, respectively. 69.0% of the char and 36.4% of the soot were present in PM 2.5. The char showed apparent seasonal variations, with highest concentrations in winter and lowest in summer; while soot displayed maximum concentrations in fall and minimum in summer. The char/soot ratios in PM 2.5 averaged from 3.29 to 17.22; while for TSP, they were from 1.20 to 7.07. Both of the ratios in PM 2.5 and TSP were highest in winter and lowest in fall. Comparisons of seasonal variations in OC/EC and char/soot ratios confirmed that char/soot may be a more effective indicator of carbonaceous aerosol source identification than OC/EC. Annual average atmospheric dry deposition fluxes of OC and EC into ECS were estimated to be 229 and 107 μg m−2 d−1, respectively, and their deposition fluxes significantly increased during episodes. It was estimated that the loadings of OC + EC and EC accounted for 1.3% and 4.1% of the total organic carbon and EC in ECS surface sediments, respectively, implying a relatively small contribution of OC and EC dry deposition to organic carbon burial. This finding also indicates a possibly more important contribution of wet deposition to organic carbon burial in sediments of ECS, and this factor should be considered for future study. Graphical abstract Image 1 Highlights • PM 2.5 contained approximately 69% of char and 36% of soot, respectively, in TSP. • Char/soot may be a more effective indicator of carbonaceous aerosol source identification than OC/EC. • Dry depositions of OC + EC and EC accounted for 1.3% and 4.1% of their burial in ECS surface sediments, respectively. [ABSTRACT FROM AUTHOR]

Abstract Particulate matter with aerodynamic diameter less than 2.5 μm (PM 2.5) is a complex mixture of chemical constituents emitted from various emission sources or through secondary reactions/processes; however, PM 2.5 is regulated mostly based on its total mass concentration. Studies to identify the impacts on climate change, visibility degradation and public health of different PM 2.5 constituents are hindered by limited ground measurements of PM 2.5 constituents. In this study, national models were developed based on random forest algorithm, one of machine learning methods that is of high predictive capacity and able to provide interpretable results, to predict concentrations of PM 2.5 sulfate, nitrate, organic carbon (OC) and elemental carbon (EC) across the conterminous United States from 2005 to 2015 at the daily level. The random forest models achieved high out-of-bag (OOB) R2 values at the daily level, and the mean OOB R2 values were 0.86, 0.82, 0.71 and 0.75 for sulfate, nitrate, OC and EC, respectively, over 2005–2015. The long-term temporal trends of PM 2.5 sulfate, nitrate, OC and EC predictions agreed well with their corresponding ground measurements. The annual mean of predicted PM 2.5 sulfate and EC levels across the conterminous United States decreased substantially from 2005 to 2015; while concentrations of predicted PM 2.5 nitrate and OC decreased and fluctuated during the study period. The annual prediction maps captured the characterized spatial patterns of the PM 2.5 constituents. The distributions of annual mean concentrations of sulfate and nitrate were generally regional in the extent that sulfate decreased from east to west smoothly with enhancement in California and nitrate had higher concentration in Midwest, Metro New York area, and California. OC and EC had regional high concentrations in the Southeast and Northwest as well as localized high levels around urban centers. The spatial patterns of PM 2.5 constituents were consistent with the distributions of their emission sources and secondary processes and transportation. Hence, the national models developed in this study could provide supplementary evaluations of spatio-temporal distributions of PM 2.5 constituents with full time-space coverages in the conterminous United States, which could be beneficial to assess the impacts of PM 2.5 constituents on radiation budgets and visibility degradation, and support exposure assessment for regional to national health studies at county or city levels to understand the acute and chronic toxicity and health impacts of PM 2.5 constituents, and consequently provide scientific evidence for making targeted and effective regulations of PM 2.5 pollution. Highlights • First national machine learning models to predict PM 2.5 constituents in the U.S. • Random forest models provide accurate and interpretable results with full coverage. • Random forest models explained over 70% of daily variability of PM 2.5 constituents. • Predictions capture both regional and localized patterns of PM 2.5 constituents. [ABSTRACT FROM AUTHOR]

Abstract Carbonaceous aerosol was measured during fall of 2010 in Beijing. Daily variation of organic carbon (OC) was found to coincide with that of relative humidity (RH), and the OC to elemental carbon (EC) ratios were more than doubled during the more humid periods (RH above 0.75) compared to other conditions. This large increase in OC/EC could not be explained by the variations of primary biomass burning emissions but was accompanied by a five-fold increase in the sulfate to EC ratio. It was then inferred that secondary organic aerosol (SOA) formation was enhanced under the more humid conditions, presumably through aqueous-phase processes. This enhanced SOA formation might be partially associated with particles externally mixed with black carbon, as indicated by the RH-dependent relationships between aerosol optical attenuation and EC loading. In addition, organic aerosols exhibited different properties between the more humid and the other periods, such that they were less volatile and charred more significantly during thermal-optical analysis in the former case. These differences coincided with the evidence of enhanced SOA formation under the more humid conditions. This study highlights the necessity of incorporating aqueous-phase chemistry into air quality models for SOA. Highlights • OC/EC were more than doubled during the more humid periods than the other conditions. • The large increase in OC/EC could not be explained by biomass burning emissions. • The large increase in OC/EC was accompanied by a five-fold increase in sulfate/EC. • OA were less volatile and charred more significantly during the more humid periods. [ABSTRACT FROM AUTHOR]

Elemental carbon (EC) and organic carbon (OC) are major components of atmospheric PM 2.5. In this article we represent the results of long-term measurements (8–12 years) of EC and OC at three different background sites in Finland: in a rural area (Virolahti) since the summer 2010, in a marine environment (Utö) since the summer 2011, and in a clean arctic environment (Pallas/Matorova) since 2014. The concentrations of OC and EC were measured with a semi-continuous organic and elemental carbon analyser (SC-OCEC) in all the sites. The yearly average concentrations of OC varied between 0.96–3.1, 0.76–1.6 and 0.30–0.69 μg m−3 at the rural (Virolahti), marine (Utö) and arctic (Pallas/Matorova) sites, respectively. Similarly, the corresponding yearly average concentrations of EC ranged between 0.095–0.48, 0.090–0.2 and 0.010–0.086 μg m−3 at those sites. A clear seasonal variation in OC and EC concentrations was observed at each measurement site. OC concentrations were highest during summertime whereas EC concentrations were highest in wintertime. The seasonality of OC was clearest at the Arctic site that had also the largest temperature variation and shortest growing season resulting in a sharp increase in OC concentrations from June to August. At all the measurement sites, OC concentrations gradually increased when the temperature rose over sub-zero temperatures whereas the daily average EC concentrations did not show as apparent temperature dependence as OC. Based on the cluster analysis, highest OC and EC concentrations, and the highest total load for EC (23–32%), at all the sites were detected with the air mass origin of southeast. In the marine environment, the effect of black carbon from ship plumes was investigated. The limit for ship fuel sulfur content changed during the measurement period (in January 2015), but it was not observed to influence the Optical EC concentrations. Overall, long-term, continuous measurements are crucial when the time trends in air quality and the effect of emission mitigation actions are investigated. In this study, a slight decrease in OC was observed at the Marine site, however, a decrease for EC was seen both at the rural and marine sites suggesting that the emission mitigation actions like EURO limits for light vehicles or improved after-treatment systems developed for industry and energy production have already decreased the background concentrations in rural areas. • Long-term EC and OC measurements were conducted in three contrasting background areas. • Biogenic sources affected clearly OC concentrations in the summertime. • EC had a significant decreasing trend at the rural site. • Sulfur content in ship fuels was not influencing Optical EC concentration at the marine site. [ABSTRACT FROM AUTHOR]

Highlights • Microwave pyrolysis was proposed for recovering oil and gas from spent HDS catalyst. • The optimal conditions for de-oiling by microwave pyrolysis were 700 °C and 30 min. • 64% and 40% of C were removed by microwave and conventional pyrolysis, respectively. • XPS results indicate that elemental carbon can be removed by microwave pyrolysis. • Recovered oil and gas can be reused as fuels with high heating value. Abstract Spent hydrodesulphurization (HDS) catalysts generally contain about 20% oil, the presence of which hinders the metallurgical processes for recovering valuable metals. In this study, a new approach was developed to remove oil from spent HDS catalysts by microwave pyrolysis. Firstly, the effects of the pyrolysis temperature and time on removing oil were investigated using microwave and conventional pyrolysis. The results show that removing oil using microwave pyrolysis was superior to using conventional pyrolysis in terms of energy savings, speed, and removal ratio. Under the optimum pyrolysis conditions (700 °C, 30 min, and an inert atmosphere), about 64% and 25% removal of carbon and sulfur, respectively, and 25% weight loss were achieved with the proposed method, while using conventional pyrolysis, only 40% and 18% removal of carbon and sulfur, respectively, and 20% weight loss were achieved. The properties of the raw spent HDS catalysts and pyrolysis products, including their morphologies and elemental states, were investigated using SEM-EDS, XPS, and FTIR. The results of these analyses indicate that the proposed method not only removes oil efficiently, but can also remove elemental carbon from spent catalysts. Finally, the main components of recovered oil and gas were investigated using FTIR, GC–MS, and GC–TCD analyses. [ABSTRACT FROM AUTHOR]

Carbonaceous aerosols represent an important nexus between air pollution and climate change. Here we collected filter-based PM 2.5 samples during summer and autumn in 2015 at one urban and two rural sites in Guangzhou, a megacity in southern China, and got the light absorption by black carbon (BC) and brown carbon (BrC) resolved with a DRI Model 2015 multi-wavelength thermal/optical carbon analyzer apart from determining the organic carbon (OC) and elemental carbon (EC) contents. On average BrC contributed 12–15% of the measured absorption at 405 nm (LA 405 ) during summer and 15–19% during autumn with significant increase in the LA 405 by BrC at the rural sites. Carbonaceous aerosols, identified as total carbon (TC), yielded average mass absorption efficiency at 405 nm (MAE 405 ) that were approximately 45% higher in autumn than in summer, an 83% increase was noted in the average MAE 405 for OC, compared with an increase of only 14% in the average MAE 405 for EC. The LA 405 by BrC showed a good correlation ( p < 0.001) with the ratios of secondary OC to PM 2.5 in summer. However, this correlation was poor ( p > 0.1) in autumn, implying greater secondary formation of BrC in summer. The correlations between levoglucosan (a marker of biomass burning) and the LA 405 by BrC were significant during autumn but insignificant during summer, suggesting that the observed increase in the LA 405 by BrC during autumn in rural areas was largely related to biomass burning. The measurements of light absorption at 550 nm presented in this study indicated that the use of the IMPROVE algorithm with an MAE value of 10 m 2 /g for EC to approximate light absorption may be appropriate in areas not strongly affected by fossil fuel combustion; however, this practice would underestimate the absorption of light by PM 2.5 in areas heavily affected by vehicle exhausts and coal burning. [ABSTRACT FROM AUTHOR]

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/m 3 . 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. [ABSTRACT FROM AUTHOR]

During a transition period from 2007 to 2009, the Chemical Speciation Network (CSN) altered its carbon sampling instrumentation and analysis methods to be more consistent with the Interagency Monitoring of Protected Visual Environments (IMPROVE) network. CSN and IMPROVE operated collocated samplers spanning the transition at eight sites. This paper compares elemental, organic, and total carbon (EC, OC, and TC, respectively) measurements at these collocated sites from 2005 through March 2016. Prior to the changes, the concentration measurements between the two networks had imprecisions of 17, 17, and 16% and biases of 0.22, −1.93, and −1.69 μg m −3 for EC, OC, and TC, respectively, with CSN measuring higher OC and TC than IMPROVE. After the sampling equipment and analytical methods were changed, the imprecision improved to 14, 12, and 10% and biases decreased to −0.02, −0.12, and −0.15 μg m −3 for EC, OC, and TC, respectively. The increased comparability, particularly the smaller biases, between the two networks facilitates comparisons between urban and rural aerosols in geospatial analyses. [ABSTRACT FROM AUTHOR]

Time-resolved quantitative and qualitative measurement of the particulate matter (PM) - composition is an ongoing challenge for scientists and instrument developers. Raman spectroscopy is especially useful for PM analysis, however, its application has been restricted mainly to qualitative laboratory investigation. A low particle load on the filter and the resulting high elastic backscattering make Raman spectroscopic quantitative monitoring a demanding task with regard to optical design and the mathematical tools needed for data evaluation. In this paper, we present environmental measurements taken over several weeks with the fully automatized Raman Soot Spectrometer (RaSoS). The hourly recorded Raman spectra are characterized using factor analytic methods and a linear model for quantitative determination of the apparent elemental carbon (EC) filter loading is derived. Its predictions are compared with the measurements of an aethalometer which utilizes light absorption to measure the black carbon (BC) - concentration. Raman spectra taken a year earlier at the same location yield plausible predictions using the same model. The EC-scores of the RaSoS generally agree well with the BC measurements of the aethalometer ( σ = 0.82 – 0.92 ). However, for very high concentrations of BC and for several short time periods, there are deviations which may be connected to varying PM-composition. [ABSTRACT FROM AUTHOR]

Brown carbon (BrC) is increasingly included in climate models as an emerging category of particulate organic compounds that can absorb solar radiation efficiently at specific wavelengths. Water-soluble organic carbon (WSOC) has been commonly used as a surrogate for BrC; however, it only represents a limited fraction of total organic carbon (OC) mass, which could be as low as about 20% in urban atmosphere. Using methanol as the extraction solvent, up to approximately 90% of the OC in Beijing aerosol was isolated and measured for absorption spectra over the ultraviolet-to-visible wavelength range. Compared to methanol-soluble OC (MSOC), WSOC underestimated BrC absorption by about 50% at 365 nm. The mass absorption efficiencies measured for BrC in Beijing aerosol were converted to the imaginary refractive indices of BrC and subsequently used to compute BrC coating-induced enhancement of light absorption ( E abs ) by black carbon. E abs attributed to lensing was reduced in the case of BrC coating relative to that caused by purely-scattering coating. However, this reduction was overwhelmed by the effect of BrC shell absorption, indicating that the overall effect of BrC coating was an increase in E abs . Methanol extraction significantly reduced charring of OC during thermal-optical analysis, leading to a large increase in the measured elemental carbon (EC) mass and an apparent improvement in the consistency of EC measurements by different thermal-optical methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • A two-step method to adjust bottom-up EC emissions was developed. • The approach was applied to estimate regional and local EC contributions. • The emission adjustment resulted in EC emissions 2.5 times higher than the inventory. • The NME of modeled EC concentrations decreased from 48 % to 22 % after adjustment. • The linear regression function yields the optimal results among three functions. In this study, we developed a practical approach to augment elemental carbon (EC) emissions to improve the reproducibility of the most recent air quality with photochemical grid modeling in support of source-receptor relationship analysis. We demonstrated the usefulness of this approach with a series of simulations for EC concentrations over Northeast Asia during the 2016 Korea-United States Air Quality study. Considering the difficulty of acquiring EC observational data in foreign countries, our approach takes two steps: (1) augmenting upwind EC emissions based on simulated upwind contributions and observational data at a downwind EC monitor considered as the most representative monitor for upwind influences and (2) adjusting downwind EC emissions based on simulated downwind contributions, including the effects of updated upwind emissions from the first step and observational data at the downwind EC monitors. The emission adjustment approach resulted in EC emissions 2.5 times higher than the original emissions in the modeling domain. The EC concentration in the downwind area was observed to be 1.0 μg m−3 during the study period, while the simulated EC concentration was 0.5 μg m−3 before the emission adjustment. After the adjustment, the normalized mean error of the daily mean EC concentration decreased from 48 % to 22 % at ground monitor locations. We found that the EC simulation results were improved at high altitudes, and the contribution of the upwind areas was greater than that of the downwind areas for EC concentrations downwind with or without emission adjustment. This implies that collaborating with upwind regions is essential to alleviate high EC concentrations in downwind areas. The developed emission adjustment approach can be used for any upwind or downwind area when transboundary air pollution mitigation is needed because it provides better reproducibility of the most recent air quality through modeling with improved emission data. [ABSTRACT FROM AUTHOR]

Background. Diesel engine exhaust (DEE) and some of the polycyclic aromatic hydrocarbons (PAH) it contains are carcinogenic to humans (for example benzo(a)pyrene) and can cause lung cancer in workers. The objective of this study was to assess exposures to DEE and its component PAH and the potential associations between these two health hazards in a salt and potash mining population. Methods. Between 2017 and 2019, 1003 underground workers (mining n = 801, maintenance n = 202) and 243 above-ground facility workers from two German mines participated. Personal exposure to DEE was assessed in air as elemental carbon for diesel particulate matter (EC-DPM), whereas exposure to PAH was assessed in pre- and post-shift urine samples in terms of 1-hydroxypyrene (1-OHP). Associations between EC-DPM and 1-OHP were studied using linear regression models. Results. The highest EC-DPM exposures were measured in mining workers (median 0.06 mg/m³) followed by workers in the maintenance (0.03 mg/m3) and facility areas (<0.02 mg/m3). Exposures above the current German occupational threshold level of 0.05 mg/m3 were observed in 56%, 17%, and 5% of mining, maintenance and facility workers, respectively. 1-OHP increased statistically significantly across a work shift in underground workers but not in facility workers. Regression analyses revealed an increase of post-shift 1-OHP by almost 80% in mining and 40% in maintenance compared with facility workers. 1-OHP increased with increasing EC-DPM among underground workers. However, internal exposure of 1-OHP mainly remained at levels similar to those of the German general population in more than 90% of the urine samples. Conclusions. While exposures to DEE above the current German OEL for EC-DPM are quite common in the studied population of underground salt and potash miners (39.5% overall), urinary concentrations of 1-OHP did not reflect these findings. • 48% of underground workers exceeded current EC-DPM occupational exposure limits. • Internal exposure of 1-hydroxypyrene rose in underground workers during a shift. • Internal exposure standards of 1-hydroxypyrene were generally met. [ABSTRACT FROM AUTHOR]

Aggressive drive cycles can cause substantial discrepancies between particulate matter (PM) measurement methods and increased emissions variability. Previous work demonstrated good agreement, within ~10%, between aerosol instruments and gravimetric determinations of PM mass emissions from gasoline direct injection engine (GDI) vehicles run over the Federal Test Procedure (FTP). In contrast, the present study reveals discrepancies of a factor of three or more for these vehicles run over the US06 portion of the supplemental FTP test. Two aspects of this are examined: 1) Changes in particle composition and morphology and 2) variability associated with vehicle history and test preparation. PM emissions during the US06 cycle are often accompanied by a strong nucleation mode. The organic to elemental carbon ratio increases relative to the FTP cycle. Also, the black carbon to elemental carbon ratio decreases, suggesting the formation of brown soot. The origins of these changes are not entirely clear, but are likely associated with the high engine exhaust temperatures during the US06 cycle. This also contributes to the higher test to test variability observed for the US06 versus FTP cycle. High temperatures can thermally desorb and pyrolyze various materials, including heavy hydrocarbons, ash, and inorganic salts deposited in the exhaust pipe, catalytic converter, and muffler that provide an additional PM source not present during FTP driving. The first day’s PM mass emissions are often substantially higher than on following days for the US06 cycle, but not the FTP. There is also a distinct drop in PM emissions between first and subsequent US06 cycles run in series. [ABSTRACT FROM AUTHOR]

Black carbon is the second largest contributor to climate change and also poses risks to human health. Despite the need for black carbon (BC) emissions estimates from residential biomass burning for cooking, quantitative data are still scarce. This scarcity is mainly due to the scattered location of the stoves, as well as relatively costly and complex analytical methods available. Two low cost and easy-to-use optical methods, a cell-phone based system and smoke stain reflectometry, where compared to elemental carbon (EC) concentrations by the Sunset OCEC Analyzer (TOT). The three techniques were challenged with different aerosol types (urban and biomass cookstoves), and different filter substrates (quartz and glass fibre). A good agreement was observed between the two low cost techniques and the reference system for the aerosol types and concentrations assessed, although the relationship was statistically different for each type of aerosol. The quantification of correction factors with respect to the reference method for the specific conditions under study is essential with either of the low-cost techniques. BC measurements from the cell-phone system and the reflectometer were moderately affected by the filter substrate. The easy use of the cell-phone based system may allow engaging cookstove users in the data collection process, increasing the amount and frequency of data collection which may, otherwise, not be feasible in resourced constrained locations. This would help to raise public awareness about environmental and health issues related to cookstoves. [ABSTRACT FROM AUTHOR]

Equivalent Black Carbon (EBC) and Elemental Carbon (EC) are different mass metrics to quantify the amount of combustion aerosol. Both metrics have their own measurement technique. In state-of-the-art carbon analysers, optical measurements are used to correct for organic carbon that is not evolving because of pyrolysis. These optical measurements are sometimes used to apply the technique of absorption photometers. Here, we use the transmission measurements of our carbon analyser for simultaneous determination of the elemental carbon concentration and the absorption coefficient. We use MAAP data from the CESAR observatory, the Netherlands, to correct for aerosol-filter interactions by linking the attenuation coefficient from the carbon analyser to the absorption coefficient measured by the MAAP. Application of the calibration to an independent data set of MAAP and OC/EC observations for the same location shows that the calibration is applicable to other observation periods. Because of simultaneous measurements of light absorption properties of the aerosol and elemental carbon, variation in the mass absorption efficiency (MAE) can be studied. We further show that the absorption coefficients and MAE in this set-up are determined within a precision of 10% and 12%, respectively. The precisions could be improved to 4% and 8% when the light transmission signal in the carbon analyser is very stable. [ABSTRACT FROM AUTHOR]

In this paper, the chemical constitutes of PM 2.5 mass [organic carbon (OC), elemental carbon (EC), water soluble inorganic ionic components (WSIC), and trace elements] was estimated for its chemical characteristics and source apportionment study at Delhi, India during January 2013 to May 2014. In the present case, the average mass concentration of PM 2.5 was recorded as 125.5 ± 77.2 μg m − 3 (range: 31.1–429.5 μg m − 3 ). The average concentration of major and trace elements (Na, Mg, Al, P, S, Cl, K, Ca, Cr, Ti, AS, Br, Pb, Fe, Zn and Mn) was accounted for ~ 22% of PM 2.5 mass. Strong seasonal variation was observed in PM 2.5 mass concentration and its chemical composition with maxima during winter and minima during monsoon seasons. The chemical composition of the PM 2.5 was reconstructed using IMPROVE equation from the analyzed elemental composition of PM 2.5 mass. In reconstructed PM 2.5 mass, the highest contribution accounted from particulate organic matter (27.5%) to other components e.g., soil/crustal matter (16.1%), ammonium sulphate (16.1%), ammonium nitrate (13.1%), sea salt (17.1%) and light absorbing carbon (10.2%). In the present study, Positive Matrix Factorization (PMF) was used for identifying the PM 2.5 sources at the observational site of Delhi. The major source of PM 2.5 was identified as secondary aerosols (23.2%), soil dust (22.5%), vehicle emissions (18.5%), fossil fuel burning (13.1%), biomass burning (12.3%), industrial emissions (6.3%) and sea salts (4.1%) at Delhi. [ABSTRACT FROM AUTHOR]

Pulverized bituminous coal was burned in a 10 W externally heated entrained flow furnace under air-combustion and three oxy-combustion inlet oxygen conditions (28, 32, and 36%). Experiments were designed to produce flames with practically relevant stoichiometric ratios (SR = 1.2–1.4) and constant residence times (2.3 s). Size-classified fly ash samples were collected, and measurements focused on the soot, elemental carbon (EC), and organic carbon (OC) composition of the total and ultrafine (<0.6 µm) fly ash. Results indicate that although the total fly ash carbon, as measured by loss on ignition, was always acceptably low (<2%) with all three oxy-combustion conditions lower than air-combustion, the ultrafine fly ash for both air-fired and oxy-fired combustion conditions consists primarily of carbonaceous material (50–95%). Carbonaceous components on particles <0.6 µm measured by a thermal optical method showed that large fractions (52–93%) consisted of OC rather than EC, as expected. This observation was supported by thermogravimetric analysis indicating that for the air, 28% oxy, and 32% oxy conditions, 14–71% of this material may be OC volatilizing between 100 °C and 550 °C with the remaining 29–86% being EC/soot. However, for the 36% oxy condition, OC may comprise over 90% of the ultrafine carbon with a much smaller EC/soot contribution. These data were interpreted by considering the effects of oxy-combustion on flame attachment, ignition delay, and soot oxidation of a bituminous coal, and the effects of these processes on OC and EC emissions. Flame aerodynamics and inlet oxidant composition may influence emissions of organic hazardous air pollutants (HAPs) from a bituminous coal. During oxy-coal combustion, judicious control of inlet oxygen concentration and placement may be used to minimize organic HAP and soot emissions. [ABSTRACT FROM AUTHOR]

In this study, the emissions of three different generations of firewood stoves were characterized to test their sustainability with this new problematic. Organic Carbon (OC) and Elemental Carbon (EC) emissions were particularly targeted. After an investigation of the OC/EC measurement method, a specific protocol was developed, validated and optimized in order to measure OC/EC from direct samplings in the flue gas, without diluting or cooling systems. Carbon monoxide (CO), Total Suspended Particles (TSP) and Total Hydrocarbon (THC) emissions were followed too. To go further in the characterization and in the differentiation of the particles emitted from each kind of stoves, a Field Emission Gun Scanning Electron Microscope (FEG SEM) was used. The medium generation emitted 40% less mass of OC than the previous one. Concerning the new generation, emissions were reduced in mass about 98% for the EC and 40% for the OC compared to the old generation. [ABSTRACT FROM AUTHOR]

Radiocarbon ( 14 C) analysis is a unique tool that can be used to directly apportion organic carbon (OC) and elemental carbon (EC) into fossil and non-fossil fractions. In this study, a coupled carbon analyzer and high-vacuum setup was established to collect atmospheric OC and EC. We thoroughly investigated the correlations between 14 C levels and mass recoveries of OC and EC using urban PM 2.5 samples collected from a city in central China and found that: (1) the 14 C signal of the OC fraction collected in the helium phase of the EUSSAR_2 protocol (200 °C for 120 s, 300 °C for 150 s, 450 °C for 180 s, and 650 °C for 180 s) was representative of the entire OC fraction, with a relative error of approximately 6%, and (2) after thermal treatments of 120 s at 200 °C, 150 s at 300 °C, and 180 s at 475 °C in an oxidative atmosphere (10% oxygen, 90% helium) and 180 s at 650 °C in helium, the remaining EC fraction sufficiently represented the 14 C level of the entire EC, with a relative error of <10%. The average recovery of the OC and EC fractions for 14 C analysis was 64± 7% (n = 5) and 87 ± 5% (n = 5), respectively. The fraction of modern carbon in the OC and EC of reference material (RM) 8785 was 0.564 ± 0.013 and 0.238 ± 0.006, respectively. Analysis of 14 C levels in four selected PM 2.5 samples in Xinxiang, China revealed that the relative contribution of fossil sources in OC and EC in the PM 2.5 samples were 50.5± 5.8% and 81.4± 2.6%, respectively, which are comparable to findings in previous studies conducted in other Chinese cities. We confirmed that most urban EC derives from fossil fuel combustion processes, whereas both fossil and non-fossil sources have comparable and important impacts on OC. Our results suggested that water-soluble organic carbon (WSOC) and its pyrolytic carbon can be completely removed before EC collection via the method employed in this study. [ABSTRACT FROM AUTHOR]

The Supersito Project ( www.supersito-er.it ) has been active in the Emilia-Romagna region, southern part of the Po Valley (Italy), since 2011. Focal aim of the project is to enhance the knowledge on atmospheric aerosol and its impact on human health. In the framework of Supersito, major chemical components of daily PM2.5 were investigated over a period of more than three years at four sampling sites, representative of dissimilar territorial conditions: one rural background (SPC) and three urban background sites in the coastal (RN), central (MS) and inner area (PR) of the region. In all the sites, organic and elemental carbon and water soluble inorganic ions accounted for more than 70% of PM2.5 mass, during all seasons. Nitrate and organic carbon (OC) were the main components of winter PM2.5, while summer aerosol was mainly contributed by OC and sulphate. OC was dominated by primary sources, with a potentially important contribution from biomass burning, in winter, while secondary processes dominated OC production in summer. A substantial homogeneity was observed on a regional scale in terms of spatial distribution of pollutants, with EC only presenting significant differences between urban and rural areas during winters. Nonetheless, differences were observed between the coastal and the inner part of the region, with the former being systematically characterized by higher concentrations of carbonaceous compounds and lower concentrations of ammonium nitrate. The coastal area was likely influenced by the aged OC from the Po Valley outflow in addition to local sources, while the scarcity of local sources of ammonia limited the formation of ammonium nitrate. In the studied area, local and regional meteorology - mostly governed by geographical collocation and orography – was responsible for PM2.5 mass and composition no less than local and regional emission sources. [ABSTRACT FROM AUTHOR]

Long-term pollutant concentration trends can be useful for evaluating air quality effects of emission controls and historical transitions in energy sources. We employed archival records of coefficient of haze (COH), a now-retired measure of light-absorbing particulate matter, to re-construct historical black carbon (BC) concentrations at urban locations in the United States (U.S.). The following relationship between COH and BC was determined by reinstating into service COH monitors beside aethalometers for two years in Vallejo and one year in San Jose, California: BC (μg m −3 ) = 6.7COH + 0.1, R 2 = 0.9. Estimated BC concentrations in ten states stretching from the East to West Coast decreased markedly between 1965 and 1980: 5-fold in Illinois, Ohio, and Virginia, 4-fold in Missouri, and 2.5-fold in Pennsylvania. Over the period from the mid-1960s to the early 2000s, annual average BC concentrations in New Jersey and California decreased from 13 to 2 μg m −3 and 4 to 1 μg m −3 , respectively, despite concurrent increases in fossil fuel consumption from 1.6 to 2.1 EJ (EJ = 10 18 J) in New Jersey and 4.2 to 6.4 EJ in California. New Jersey's greater reliance on BC-producing heavy fuel oils and coal in the 1960s and early 1970s and subsequent transition to cleaner fuels explains why the decrease was larger in New Jersey than California. Patterns in seasonal and weekly BC concentrations and energy consumption trends together indicate that reducing wintertime emissions – namely substituting natural gas and electricity for heavy fuel oil in the residential sector – and decreasing emissions from diesel vehicles contributed to lower ambient BC concentrations. Over the period of study, declining concentrations of BC, a potent and short-lived climate warming pollutant, contrast increasing fossil fuel carbon dioxide (CO 2 ) emissions in the U.S. Declining BC emissions may have had the benefit of mitigating some atmospheric warming driven by increased CO 2 emissions with complementary health benefits. [ABSTRACT FROM AUTHOR]