Equivalent Black Carbon Concentrations Research Articles

End-to-end simulations to optimize imaging spectroscopy mission requirements for seven scientific applications

CNES is currently carrying out a Phase A study to assess the feasibility of a future hyperspectral imaging sensor (10 m spatial resolution) combined with a panchromatic camera (2.5 m spatial resolution). This mission focuses on both high spatial and spectral resolution requirements, as inherited from previous French studies such as HYPEX, HYPXIM, and BIODIVERSITY. To meet user requirements, cost, and instrument compactness constraints, CNES asked the French hyperspectral Mission Advisory Group (MAG), representing a broad French scientific community, to provide recommendations on spectral sampling, particularly in the Short Wave InfraRed (SWIR) for various applications.This paper presents the tests carried out with the aim of defining the optimal spectral sampling and spectral resolution in the SWIR domain for quantitative estimation of physical variables and classification purposes. The targeted applications are geosciences (mineralogy, soil moisture content), forestry (tree species classification, leaf functional traits), coastal and inland waters (bathymetry, water column, bottom classification in shallow water, coastal habitat classification), urban areas (land cover), industrial plumes (aerosols, methane and carbon dioxide), cryosphere (specific surface area, equivalent black carbon concentration), and atmosphere (water vapor, carbon dioxide and aerosols). All the products simulated in this exercise used the same CNES end-to-end processing chain, with realistic instrument parameters, enabling easy comparison between applications. 648 simulations were carried out with different spectral strategies, radiometric calibration performances and signal-to-noise Ratios (SNR): 24 instrument configurations × 25 datasets (22 images + 3 spectral libraries).The results show that spectral sampling up to 20 nm in the SWIR range is sufficient for most applications. However, 10 nm spectral sampling is recommended for applications based on specific absorption bands such as mineralogy, industrial plumes or atmospheric gases. In addition, a slight performance loss is generally observed when radiometric calibration accuracy decreases, with a few exceptions in bathymetry and in the cryosphere for which the observed performance is severely degraded. Finally, most applications can be achieved with a realistic SNR, with the exception of bathymetry, shallow water classification, as well as carbon dioxide and methane estimation, which require the optimistic SNR level tested. On the basis of these results, CNES is currently evaluating the best compromise for designing the future hyperspectral sensor to meet the objectives of priority applications.

Vertical distributions of atmospheric black carbon in dry and wet seasons observed at a 356-m meteorological tower in Shenzhen, South China

Black carbon (BC) is a vital climate forcer in the atmosphere, but measurements of BC vertical profiles near the surface remain limited. This study investigates time-resolved vertical profiling of BC in both dry (December 2017) and wet (August 2018) seasons in Shenzhen, China, at a 356-m meteorological tower. In the dry season, five micro-aethalometers were deployed at different heights (2, 50, 100, 200, and 350 m), while four heights (2, 100, 200, and 350 m) were measured in the wet season. The concentrations of equivalent BC (eBC) showed a decreasing trend with altitude in the dry season, while a weaker vertical gradient was observed in the wet season. The diurnal variability of eBC in the dry season is also more significant than in the wet season. Correlation analysis between eBC concentrations at the ground and those at the upper levels suggest a better vertical mixing of eBC in the wet season than in the dry season. In the wet season when south wind prevailed, eBC concentration at ground level was likely reduced by the large amount of vegetation cover south to the sampling site. In the dry season, eBC concentrations at 350 m show little dependence on wind speed, implying that local emissions have a limited effect on eBC concentrations at 350 m. In the wet season when brown carbon influence was weak, higher wind speed leads to a higher Ångström exponent (AAE) at 350 m, likely associated with more aged BC particles. Cluster analysis of backward trajectories suggests that high eBC concentration was associated with air masses from Central China in both seasons. This study provides a better understanding on the influencing factors that affect the vertical distributions of BC in the lower part of the boundary layer.

Yearly Variations of Equivalent Black Carbon Concentrations Observed in Krakow, Poland

The evaluation of the equivalent black carbon (eBC) concentration is very important, especially in environmental sciences. Light absorbing carbon (LAC), also presented as equivalent black carbon (eBC), is generated from the partial combustion of fossil fuels and biomass. The scientific interest in eBC is large because its contribution to the PM2.5 fraction is high, especially in urban areas. This study presents yearly variations in eBC concentrations observed in Krakow, Poland. The transmissions of light at different wavelengths were measured by a multi-wavelength absorption black carbon instrument (MABI). Absorption coefficients and concentrations of eBC were calculated. Samples of the PM2.5 fraction were collected from 1 February 2020 to 27 March 2021 every third day in Krakow, Poland. The concentrations of eBC from fossil fuel combustion and biomass burning were in the range of 0.82–11.64 μg m−3 and 0.007–0.84 μg m−3, respectively. At the same time, PM2.5 concentrations varied from 3.14 to 55.24 μg m−3. The eBC contribution was a significant part of PM2.5 mass and we observed a seasonal variation in eBC concentrations during the year, with the peak in winter (5.3 ± 1.8 µg m−3). The contribution of BC from biomass burning to PM2.5 mass was in the range of 4%–5% with the highest value for winter. The eBC concentration during workdays was 21% higher than during weekend days.

Toward Cleaner Transport Alternatives: Reduction in Exposure to Air Pollutants in a Mass Public Transport.

Commuters are often exposed to higher concentrations of air pollutants due to its proximity to mobile sources. Despite recent trends in urban transport toward zero- and low-tailpipe emission alternatives, the assessments of the impact of these transformations on commuter exposure are limited by the low frequency of such studies. In this work, we use a unique data set of personal exposure concentration measurements collected over the span of 5 years to analyze changes due to the introduction of a new fleet for Bogotá's Bus Rapid Transit System. In that system, over a thousand Euro-II and -III diesel-powered buses were replaced with Euro-VI compressed natural gas and filter-equipped Euro-V diesel buses. We measured personal exposure concentrations of equivalent black carbon (eBC), fine particulate (PM2.5), and ultra fine particles (UFP) during and after the retirement of old buses and the introduction of new ones. Observations collected prior to the fleet renewal were used as baseline and later compared to data collected over two follow-up campaigns in 2019 and 2020. Significant reductions in the concentration of PM2.5 and eBC were observed during the 2019 campaign, with a 48% decrease for mean in-bus eBC (89.9 to 46.4 μg m-3) and PM2.5 (180.7 to 95.4 μg m-3) concentrations. Further reductions were observed during the 2020 follow-up, when the fleet renovation was completed, with mean in-bus eBC decreasing to 17.7 μg m-3 and PM2.5 to 42.3 μg m-3. These observations imply nearly a 5-fold reduction in eBC exposure and a 4-fold decrease in PM2.5. There was a much smaller reduction of in-bus UFP concentration between 2019 and 2020, indicating a persistent presence of high particle number concentrations in the near-road environment despite the fleet renovation process. In-bus UFP concentrations ranged between 65 000 and 104 500 cm-3 during the follow-up campaigns. The results in this work illustrate the immediate benefits of reducing personal exposure through the adoption of vehicles with more stringent emission standards.

Spatial Distribution of Aerosol Characteristics over the South Atlantic and Southern Ocean Using Multiyear (2004–2021) Measurements from Russian Antarctic Expeditions

Since 2004, we have carried out yearly measurements of physicochemical aerosol characteristics onboard research vessels at Southern Hemisphere high latitudes (34–72° S; 45° W–110° E). In this work, we statistically generalize the results from multiyear (2004–2021) measurements in this area of the aerosol optical depth (AOD) of the atmosphere, concentrations of aerosol and equivalent black carbon (EBC), as well as the ionic composition of aerosol. A common regularity was that the aerosol characteristics decreased with increasing latitude up to the Antarctic coast, where the aerosol content corresponded to the global background level. Between Africa and Antarctica, AOD decreased from 0.07 to 0.024, the particle volume decreased from 5.5 to 0.55 µm3/cm3, EBC decreased from 68.1 to 17.4 ng/m3, and the summed ion concentration decreased from 24.5 to 2.5 µg/m3. Against the background of the common tendency of the latitude decrease in aerosol characteristics, we discerned a secondary maximum (AOD and ion concentrations) or a plateau (aerosol and EBC concentrations). The obtained spatial distribution of aerosol characteristics qualitatively agreed with the model-based MERRA-2 reanalysis data, but showed quantitative differences: the model AOD values were overestimated (by 0.015, on average); while the EBC concentrations were underestimated (by 21.7 ng/m3). An interesting feature was found in the aerosol spatial distribution in the region of Antarctic islands: at a distance of 300 km from the islands, the concentrations of EBC decreased on average by 29%, while the aerosol content increased by a factor of 2.5.

Characteristics of equivalent black carbon aerosols over Doon Valley in NW Indian Himalaya during COVID-19 lockdown 2020.

Recently, black carbon (BC) has been identified as a potential transmitter for COVID-19 besides being responsible for climate change and serious health hazards. To mitigate the dreaded consequences of COVID-19 pandemic, the Government of India declared a nationwide lockdown on March 24, 2020. Accordingly, observations on equivalent black carbon (EBC) aerosols using AE 51 Aethalometer were performed during different lockdowns in Doon Valley. During April, May, June, and July, the monthly average EBC mass concentration recorded 2.12 ± 1.14 μg m−3, 2.58 ± 1.46 μg m−3, 2.74 ± 1.49 μg m−3, and 2.12 ± 1.32 μg m−3, respectively. A comparison of diurnal variation patterns with earlier studies indicates a significant reduction in EBC mass concentration levels. Bipolar NWR analysis for April and May depicts that relatively high EBC concentration was experienced with prominent south-easterly winds. The EBC concentration level during daytime was high compared to nighttime hours. Preliminary visualization of scanning electron micrographs indicates the variable morphology of aerosols. The bulk particle EDX spectral analysis indicates C, O, Na, F, Al, Si, K, Ca, and Ti elements with a dominance of C and O. Windblown dust seems to be the major contributor to the ambient aerosols. Furthermore, MODIS recorded the fire anomaly (attributed to the wheat stubble burning) starting from mid of April to early-June along the Indo-Gangetic Basin. Heavy loading of polluted aerosols was visible in CALIPSO data imageries. HYSPLIT cluster trajectories indicate that the study region is strongly influenced by the air mass transporting from the Gangetic Plain, Iran, Pakistan, Afghanistan, and Gulf region.

Contribution of coal combustion to black carbon: Coupling tracers with the aethalometer model

Black carbon (BC) aerosol characteristics have been analysed from January 2016 to March 2017 in an urban background area (León, Spain), located in a coal-mining region, where this fuel is commonly used. The monthly and seasonal variations of BC and source contributions were examined. The mean equivalent BC concentration (eBC) during cold and warm months were 1.0 ± 0.5 and 0.6 ± 0.2 μg m−3, respectively. eBC can be further divided into eBCff (eBC from liquid fossil fuel) and eBCbb+cc (eBC from biomass burning plus coal combustion), with mean annual values of 0.6 ± 0.3 and 0.3 ± 0.3 μg m−3 (cold months) and 0.4 ± 0.2 μg m−3 and 0.1 ± 0.1 μg m−3 (warm months), respectively. The eBC obtained from the aethalometer and the elemental carbon (EC) quantified through a Thermal Optical Transmittance method presented a significant strong positive correlation in both warm (r = 0.82) and cold (r = 0.88) periods. A mass absorption cross-section (MAC) of 4.46 ± 0.16 between two techniques has been obtained. In the cold period, a multilinear regression model to decouple eBCbb from eBCcc was established (r2 = 0.85) based on two tracers: arsenic for coal combustion and potassium for biomass burning. The model application enabled us to distinguish the contributions to eBCbb+cc (as a function of the variance explained by the tracers) in the cold period: 74% from biomass burning and 26% from coal combustion. The highest eBCcc concentration was estimated for December 2016 and January 2017 (0.18 μg m−3). This result was supported by the Absorption Ångström Exponent (AAE), which showed the maximum value in January 2017 (1.43 ± 0.37) due to the high biomass burning and coal combustion contributions.

Elemental Carbon and Its Fractions during Evolved Gas Analysis with Respect to Pyrolytic Carbon and Split Time

We demonstrated the relationships between elemental carbon (EC) and EC fractions during evolved gas analysis (EGA) for PM2.5 sampled at KOREATECH from 29 March 2018 to 12 May 2018. The EC concentrations were compared to the concentrations of equivalent black carbon to confirm that the level of EC concentrations analyzed in this study was valid. Among various EC fractions and their combination, EC1+EC3 fractions were best correlated with the EC concentrations. Especially, dominant EC fraction was related with the dependence of carbon oxidation quantity on the oxidation temperature. We also examined the relationships between pyrolytic carbon (PyC) and EC concentration with respect to the split time. PyC was correlated with the split time in the phase of oxygen-helium mixture. PyC was close to zero for the split time in the helium phase. It is novel, as far as the authors know, that the correlation between PyC and the split time under NIOSH 5040 protocol was reported with regard to EGA. We believe that our study helps to identify what causes uncertainty in the quantification of PyC.

Temporal Variability of Equivalent Black Carbon Components in Atmospheric Air in Southern Poland

This study assesses the air quality in Zabrze (southern Poland) based on the ambient concentrations of equivalent black carbon (eBC). eBC measurement campaigns were carried out from April 2019 to March 2020 using a modern AE33 Aethalometer, accompanied by parallel measurements of gaseous pollutants, PM10 and meteorological parameters. The use of the two-component AE33 model allows for the determination of the eBC from fossil fuel combustion (eBCff) and biomass burning (eBCbb). The obtained results showed a clear seasonal variability of eBC concentrations, with higher average levels in the heating season (4.70 µg·m−3) compared to the non-heating one (1.79 µg·m−3). In both seasons, the eBCff component had a dominant share in total eBC, which indicates significant emissions from the combustion of fossil fuels for heating purposes and from local traffic sources. The obtained results showed high correlation coefficients with gaseous and particulate pollutants, with the strongest relationship for eBC and carbon monoxide (CO). During the non-heating and heating period, both anticyclone and cyclone systems played an important role in shaping eBC, eBCff and eBCbb concentrations. High concentrations of all components occurred with a significant decrease in air temperature and solar radiation in winter.

A single-beam photothermal interferometer for in situ measurements of aerosol light absorption

Abstract. We have developed a novel single-beam photothermal interferometer and present here its application for the measurement of aerosol light absorption. The use of only a single laser beam allows for a compact optical set-up and significantly easier alignment compared to standard dual-beam photothermal interferometers, making it ideal for field measurements. Due to a unique configuration of the reference interferometer arm, light absorption by aerosols can be determined directly – even in the presence of light-absorbing gases. The instrument can be calibrated directly with light-absorbing gases, such as NO2, and can be used to calibrate other light absorption instruments. The detection limits (1σ) for absorption for 10 and 60 s averaging times were determined to be 14.6 and 7.4 Mm−1, respectively, which for a mass absorption cross section of 10 m2 g−1 leads to equivalent black carbon concentration detection limits of 1460 and 740 ng m−3, respectively. The detection limit could be reduced further by improvements to the isolation of the instrument and the signal detection and processing schemes employed.

Applicability of benchtop multi-wavelength polar photometers to off-line measurements of the Multi-Angle Absorption Photometer (MAAP) samples

In this study, the applicability of a benchtop polar photometer (PP_UniMI) to retrieve multi-wavelength aerosol absorption coefficient data by off-line measurements of the Multi-Angle Absorption Photometer (MAAP) sample spots is presented. MAAP is a widespread single wavelength online instrument providing the aerosol absorption coefficient and the equivalent black carbon concentration. In this work, MAAP samples collected during four different campaigns were analysed off-line with PP_UniMI.First of all, data from PP_UniMI and MAAP were compared to investigate contributions to measurement uncertainties. In particular, the role of the following assumptions performed in the MAAP was investigated:1) reconstructing angular distribution of light scattered by filter samples from measurements at three fixed angles using analytical functions;2) setting the fraction of the back-scattered radiation by the blank filter (BM) at a fixed value BM = 0.7;3) assuming a fixed value for the asymmetry factor g = 0.75.Samples collected at several sites showed an agreement within 5% when data from the two instruments were retrieved using the same approximations (i.e. backscattered radiation from the filter matrix BM set at a fixed value, phase functions reconstructed by analytical functions from measurements at 3 angles, same asymmetry factor) in the data retrieval algorithm. Conversely, larger differences (14% on average) between off-line measurements and averaged MAAP data were obtained when the high-angular resolved information available by PP_UniMI was exploited. By analysing the role of MAAP assumptions for σap retrieval, it resulted that fixing BM = 0.7 was the main responsible for the detected differences. Indeed, high-angular resolved off-line measurements by PP_UniMI allow to directly measure BM, obtaining BM = 0.88 on white spots. It is noteworthy that the observed results were similar at all investigated sites, so they proved to be independent of the aerosol type and can likely be attributed to instrumental effects. Moreover, a sensitivity test was carried out also to check the impact of the fixed value used for the asymmetry factor (set at g = 0.75 in both instruments). Varying g values within the typical range for ambient aerosol (0.50–0.75) the estimate of aerosol absorbance ABS (directly obtained from PP_UniMI measurements and linked to σap) was affected by 8% at most, thus being a minor source of uncertainty in the calculation. The effect of the variability in blank spots used for off-line analyses was also evaluated and resulted in a contribution smaller than 3% to the uncertainty of the methodology employed.Finally, the possibility of exploiting multi-wavelength assessment of absorption coefficients is an added value of PP_UniMI; indeed, it allows to estimate the contribution of different aerosol sources and components to the absorption coefficient using MAAP tapes used in present or past campaigns.

Vertical Measurement of Equivalent Black Carbon Concentration at Low Altitude

The vertical profile of equivalent black carbon (eBC) concentrations has been measured together with the temperature up to 130 m above ground level at several locations. A hexacopter was deployed for the measurement of eBC, and the temperature on typical days in winter, spring, summer and early autumn. We observed high eBC concentrations between 10 m and 90 m above ground level, which was related to the vertical distribution of temperature. We examined that the measurement noise could be reduced by using a box-average scheme. Furthermore, the negative values at low eBC concentration could be removed for an averaging time of 30 min or longer.

One-Year Measurements of Equivalent Black Carbon, Optical Properties, and Sources in the Urumqi River Valley, Tien Shan, China

Equivalent black carbon (EBC) was measured with a seven-wavelength Aethalometer (AE-31) in the Urumqi River Valley, eastern Tien Shan, China. This is the first high-resolution, online measurement of EBC conducted in the eastern Tien Shan allowing analysis of the seasonal and hourly variations of the light absorption properties of EBC. Results showed that the highest concentrations of EBC were in autumn, followed by those in summer. The hourly variations of EBC showed two plateaus during 8:00–9:00 h local time (LT) and 16:00–19:00 h LT, respectively. The contribution of biomass burning to EBC in winter and spring was higher than in summer and autumn. The planetary boundary layer height (PBLH) showed an inverse relationship with EBC concentrations, suggesting that the reduction of the PBLH leads to enhanced EBC. The aerosol optical depths (AOD) over the Urumqi River Valley, derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) data and back trajectory analysis, showed that the pollution from Central Asia was more likely to affect the atmosphere of Tien Shan in summer and autumn. This suggests that long-distance transported pollutants from Central Asia could also be potential contributors to EBC concentrations in the Urumqi River Valley, the same as local anthropogenic activities.

Yearlong first measurements of black carbon in the western Indian Himalaya: Influences of meteorology and fire emissions

Measurements of equivalent black carbon (EBC) aerosols are presented for the first time from a high-altitude station Ranichauri (30°18′ N, 78°24′ E; 2200 m amsl) in the lesser Himalaya during January-December 2016. The influences of meteorology, fire emissions and transport, on [EBC] variations have been investigated here. The daily mean values of [EBC] are observed to vary from 0.04 ± 0.03 μgm−3 to 7.83 ± 2.66 μgm−3 with peak during April. A significant enhancement in [EBC] is observed towards the end of April, reaching the levels as high as 23.95 μgm−3 and attributed to fire emissions. Diurnal variations are suppressed with typically lower [EBC] levels during the summer monsoon (0.42 ± 0.25 μg m−3 in July) due to the transport of marine air mass and scavenging. On a seasonal basis, the average [EBC] levels are found to be higher during winter (2.72 ± 1.86 μgm−3) and pre-monsoon (2.56 ± 1.80 μg m−3), and lowest during the summer monsoon (0.89 ± 01.03 μg m−3).Our measurements in conjunction with the analysis of model meteorology (Era Interim reanalysis) show profound effects of boundary layer dynamics on EBC concentrations. Wintertime [EBC] maximum is suggested to be due to confinement of regional anthropogenic emissions in shallow boundary layer. In addition, transport from the North-West, and Western regions, characterized by wood-burning and fossil fuel combustion, also affected [EBC] the variations here, except during the summer monsoon.

Evaluation of spatial and temporal heterogeneity of black carbon aerosol mass concentration over India using three year measurements from IMD BC observation network

Extensive measurements of equivalent black carbon (EBC) aerosol mass concentration at fifteen stations of India Meteorological Department (IMD) BC observation network during the period 2016–2018 are used to study the spatial and temporal heterogeneity over India. The sampling sites represent different geographical region of India. Spatial distribution shows higher values of EBC over stations of north India and IGP. Highest annual mean EBC mass concentration during study period was reported at two mega cities New Delhi (13,575 ± 8401 ng/m3) followed by Kolkata (12,082 ± 6850 ng/m3) whereas lowest mean concentration was at Ranichauri (1737 ± 884 ng/m3) followed by Bhuj (2021 ± 1471 ng/m3). Stations located in coastal region of south India reported low concentration of EBC. In order to find out the quantitative contribution of biomass burning (EBCBB) and fossil fuel (EBCFF) in total mass concentration of EBC, source apportionment study has been carried out using Aethalometer model. The EBCFF is the dominant contributor to EBC mass concentration at all the sites in every season, while the highest seasonal biomass burning mass contribution (37%) was observed in the winter at a background site Ranichauri. Maximum concentration of EBCBB was observed at Srinagar (2671 ng/m3) where as EBCFF was maximum in Delhi (11,074 ng/m3). Seasonal and diurnal variation studies have also been carried out for all the stations. The EBC mass concentrations exhibited strong seasonality, with the highest values occurring in postmonsoon/winter and the lowest in monsoon season. The higher EBC concentration in postmonsoon/winter seasons was attributed to the increased use of fuel in seasonal emission sources, domestic heating and stagnant meteorological conditions, whereas the low levels in monsoon season were related to the precipitation scavenging. Maximum concentration of EBC (22,409 ± 10,510 ng/m3) was observed in winter season over Kolkata. Our study finds high spatial heterogeneity in EBC concentrations across the study area.

Black carbon over an urban atmosphere in northern peninsular Southeast Asia: Characteristics, source apportionment, and associated health risks

Black carbon (BC) has been demonstrated to pose significant negative impacts on climate and human health. Equivalent BC (EBC) measurements were conducted using a 7-wavelength aethalometer, from March to May 2016, over an urban atmosphere, viz., Chiang Mai (98.957°E, 18.795°N, 373 m above sea level), Thailand in northern peninsular Southeast Asia. Daily variations in aerosol light absorption were mainly governed by open fire activities in the region. The mean mass-specific absorption cross-section (MAC) value of EBC at 880 nm was estimated to be 9.3 m2 g−1. The median EBC mass concentration was the highest in March (3.3 μg m−3) due to biomass-burning (comprised of forest fire and agricultural burning) emissions accompanied by urban air pollution within the planetary boundary layer under favorable meteorological conditions. Daily mean absorption Ångström exponent (AAE470/950) varied between 1.3 and 1.7 and could be due to variations in EBC emission sources and atmospheric mixing processes. EBC source apportionment results revealed that biomass-burning contributed significantly more to total EBC concentrations (34–92%) as compared to fossil-fuel (traffic emissions). Health risk estimates of EBC in relation to different health outcomes were assessed in terms of passive cigarette equivalence, highlighting the considerable health effects associated with exposure to EBC levels. As a necessary action, the reduction of EBC emissions would promote considerable climate and health co-benefits.

On-flight intercomparison of three miniature aerosol absorption sensors using unmanned aerial systems (UASs)

Abstract. The present study investigates and compares the ground and in-flight performance of three miniaturized aerosol absorption sensors integrated on board small-sized Unmanned Aerial Systems (UASs). These sensors were evaluated during two contrasted field campaigns performed at an urban site, impacted mainly by local traffic and domestic wood burning sources (Athens, Greece), and at a remote regional background site, impacted by long-range transported sources including dust (Cyprus Atmospheric Observatory, Agia Marina Xyliatou, Cyprus). The miniaturized sensors were first intercompared at the ground-level against two commercially available instruments used as a reference. The measured signal of the miniaturized sensors was converted into the absorption coefficient and equivalent black carbon concentration (eBC). When applicable, signal saturation corrections were applied, following the suggestions of the manufacturers. The aerosol absorption sensors exhibited similar behavior against the reference instruments during the two campaigns, despite the diversity of the aerosol origin, chemical composition, sources, and concentration levels. The deviation from the reference during both campaigns concerning (eBC) mass was less than 8 %, while for the absorption coefficient it was at least 15 %. This indicates that those sensors that report black carbon mass are tuned and corrected to measure eBC more accurately than the absorption coefficient. The overall potential use of miniature aerosol absorption sensors on board small UASs is also illustrated. UAS-based absorption measurements were used to investigate the vertical distribution of eBC over Athens up to 1 km above sea level during January 2016, exceeding the top of the planetary boundary layer (PBL). Our results reveal a heterogeneous boundary layer concentration of absorbing aerosol within the PBL intensified in the early morning hours due to the concurrent peak traffic emissions at ground-level and the fast development of the boundary layer. After the full development of the PBL, homogenous concentrations are observed from 100 m a.g.l. to the PBL top.

Analysis of Absorption Characteristics and Source Apportionment of Carbonaceous Aerosol in Arid Region of Western India

The present work analyses the equivalent Black Carbon (EBC) data obtained using Aethalometer (AE-33) located at India Meteorological Department, Jodhpur, Rajasthan during the year 2016. The annual mean EBC concentration is 5.76 µg m−3 and the monthly mean concentration is maximum (12.12 µg m−3) in January and minimum (1.27 µg m−3) in December. The seasonal mean of wind speeds are 1.94, 2.02, 1.34, 1.02 m s−1 and the calm percentages are 7, 5.7, 28.7, 25.7% during pre-monsoon (MAM), monsoon (JJAS), post-monsoon (ON) and winter (DJF), respectively. The night time EBC concentrations are more than the day time concentrations due to the shallowness of the boundary layer and local anthropogenic activities. The Concentrated Weighted Trajectories (CWT) are calculated using back trajectories ending at 100 m above ground level at Jodhpur station using National Centre for Medium Range Weather Forecast (NCMRWF) Global Forecast System (GFS) based reanalysis T574 data. The CWT, directional source region analysis reveals the effect of long-range transport in the winter season with a 60% of probability of source regions from the W, NW direction of observational site. Source apportionment also carried out by assuming alpha (at 470-, 950-nm wavelengths) close to 1 for anthropogenic emissions and alpha close to 2 for biomass burning aerosols. The monthly mean biomass burning concentration is found maximum (2.58 µg m−3) in November and minimum (0.22 µg m−3) in July.

Black carbon aerosols in the ambient air of Gangotri Glacier valley of north-western Himalaya in India

The warming effect of equivalent Black Carbon (EBC) aerosols due to their light absorbing nature is a serious environmental concern, particularly, in the eco-sensitive and glaciated Himalayan region. Moreover, baseline data on BC is rarely available from most of the glaciated Himalayan region. For the first time, measurements on ambient EBC mass concentration were made at a high altitude site Chirbasa (3600 m, amsl), near Gangotri Glacier in the Indian Himalaya, during the year 2016. The change in the EBC concentration over the year was recorded from 0.01 μg m−3 to 4.62 μg m−3 with a diurnal variability of 0.10 μg m−3 to 1.8 μg m−3. The monthly mean concentration of EBC was found to be minimum (0.089 ± 0.052 μg m−3) in August and maximum (0.840 ± 0.743 μg m−3) in the month of May. The observed seasonal mean concentrations of EBC are less than 0.566 μg m−3 whereas the annual mean is 0.395 ± 0.408 μgm−3 indicating a pristine glacial and absence of locality EBC sources. Further, investigation on the occasional high values extricated that the seasonal cycle of EBC was significantly influenced by the emissions resulting from agriculture burning (in western part of the country), forest fires (along the Himalayan slopes) in summer, and to some extent the contribution from long range transport of pollutants in winter, depending the prevailing meteorological condition.

Seasonal features and origins of carbonaceous aerosols at Syowa Station, coastal Antarctica

Abstract. We have measured black carbon (BC) concentrations at Syowa Station, Antarctica, since February 2005. The measured BC concentrations in 2005–2016 were corrected to equivalent BC (EBC) concentrations using Weingartner's method. Seasonal features of EBC concentrations, long-range transport from mid-latitudes to the Antarctic coast, and their origins were characterized. Results show that daily median EBC concentrations were below the detection limit (0.2 ng m−3) to 63.8 ng m−3 at Syowa Station (median, 1.8 ng m−3; mean, 2.7 ng m−3 during the measurement period of February 2005–December 2016). Although seasonal features and year-to-year variations in EBC concentrations were observed, no long-term trend of EBC concentrations was clear during our measurement period. Seasonal features of EBC concentrations showed a spring maximum during September–October at Syowa Station. To elucidate EBC transport processes, origins, and the potential source area (PSA), we compared EBC data to backward trajectory analysis and chemical transport model simulation. From comparison with backward trajectory, high EBC concentrations were found in air masses from the marine boundary layer. This finding implies that transport via the marine boundary layer was the most important transport pathway to EBC concentrations at Antarctic coasts. Some EBC was supplied to the Antarctic region by transport via the upper free troposphere. Chemical transport model simulation demonstrated that the most important origins and PSA of EBC at Syowa Station were biomass burning in South America and southern Africa. Fossil fuel combustion in South America and southern Africa also have important contributions. The absorption Ångström exponent (AAE) showed clear seasonal features with 0.5–1.0 during April–October and maximum (1.0–1.5) in December–February. The AAE features might be associated with organic aerosols and mixing states of EBC.