Average Black Carbon Concentrations Research Articles

Spatiotemporal Estimation of Black Carbon Concentration in Tehran Using Aerosol Optical Depth Remote Sensing Data and Meteorological Parameters: Health Risk Assessment and Relationship with Green Spaces

Black Carbon (BC) is an atmospheric pollutant with considerable adverse effects on human health, increasing the chance of cardiovascular disorders, respiratory issues, and cancers in exposed individuals. Accordingly, studying BC in urban areas is essential for understanding its associated health risks. In this study, the Multi-Angle Implementation of Atmospheric Correction (MAIAC) retrieved Aerosol Optical Depth (AOD) remote sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS), along with in situ observations of BC concentration and meteorological parameters were utilized to estimate BC concentration in Tehran. In this regard, an ensemble machine learning algorithm, Gradient Boosting Machine (GBM), was employed to estimate BC concentration from 2010 to 2021, enabling a spatiotemporal analysis of BC levels in Tehran. Subsequently, the carcinogenic and non-carcinogenic effects of BC on children and adults were examined, as well as its relationship to urban green spaces. The Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Adjusted R-squared (R2adj), values for BC estimation ranged from 0.80 to 1.59 μg/m3, 0.59 to 1.10 μg/m3, and 0.70 to 0.94, respectively, indicating the promising performance of the GBM algorithm. The estimated annual average BC concentration over 11 years was 6.18± 2.46 μg/m3. Spatial variations in BC concentration and hotspot analysis at 99% and 95% confidence levels, showed that hotspots were primarily concentrated in the central and southern parts of Tehran. In contrast, cold spots were more scattered across the western and northeastern parts of the city. The cancer risk (CR) from BC exposure exceeded the recommended risk levels (1 × 10⁻⁶ to 1 × 10⁻⁴) established by the US Environmental Protection Agency (US EPA), demonstrating severe health risks for people in Tehran exposed to the current levels of BC concentrations. The average Hazard Quotient (HQ) value across all areas of Tehran was below the threshold value of 1, indicating that the non-carcinogenic health risk remains within acceptable limits. Results regarding green spaces indicated that greenery significantly influences BC concentration, revealing a negative correlation between green space coverage and BC concentration.

Long-term spatiotemporal distribution characterization of atmospheric black carbon MERRA-2 concentration over China

Black carbon (BC), a component of atmospheric aerosols, strongly adsorbs solar radiation, thereby influencing atmospheric stability and air quality. In this study, the spatiotemporal distribution, historical trends, and influencing factors of BC concentration in China from 1980 to 2020 have been investigated using MERRA-2 (Modern-era Retrospective Analysis for Research and Applications, Vision2) reanalysis dataset, population distribution, and industrial statistics data. The annual total MERRA-2 BC concentration in China (averaging 1.08 μg/m3 over the study period) exhibited three distinct phases: slow growth (1980–1999, 0.02 μg/m3/year), rapid growth (2000–2007, 0.61 μg/m3/year), and gradual decline (2008–2020, -0.014 μg/m3/year). The BC concentration was consistently higher in autumn and winter than in spring and summer, being lowest in July (9.6 μg/m3) and highest in December (14 μg/m3). Spatially, the annual average BC concentration from 1980 to 2020 followed the order: central Yangtze River region (3.14 μg/m3) > eastern coastal region (2.72 μg/m3) > northeastern region (1.40 μg/m3) > western riverine region (0.69 μg/m3) > northwestern frontier region (0.31 μg/m3). High BC-concentration areas, mainly in the central and eastern regions, correlate with regions of vigorous human activities and high industrialization levels, confirming that human activity markedly influences BC pollution. Since 2013, the implementation of emission control strategies and adjustments in the energy structure in China had led to a significant decline in BC concentration. By revealing the spatiotemporal distribution and trends of BC concentration in China, this study provides valuable scientific insights for atmospheric science, environmental protection, and air pollution.

Local contribution of road traffic and residential biomass burning to black carbon aerosols – Modelling and validation

Black carbon (BC) is a harmful pollutant to human health and the environment. The aim of this paper is to evaluate the local contribution of road traffic and residential biomass burning to BC pollution levels at urban scale by implementing an integrated modelling approach with high spatial and temporal resolution. The traffic emission was extended to include BC emission factors considering road network as line emission sources. A new module to calculate emissions from residential biomass burning was developed based on the heating degree days methodology and local surveys. The modelling approach implemented in Coimbra, Portugal, was validated with observations collected during a six-month monitoring campaign at urban traffic and urban background stations using thermo-optical and optical methods. At the traffic station, modelling results showed that 86% of BC concentrations are related to traffic activity, which are mostly due to hot exhaust emissions (76%). Nevertheless, biomass burning has a significant contribution in the whole urban area during winter. The results of monthly average BC concentrations obtained from dispersion modelling revealed a contribution from local road traffic and residential biomass burning emissions of around 4 μg m−3 at both monitoring sites during the coldest period, but this contribution was two times higher for the hotspots identified within the urban area. Moreover, hourly values at hotspots obtained from the modelling may achieve 85 μg m−3, thus stressing the importance of spatial and temporal analysis with high resolution. The validation approach applied in this work highlight the need for more transparency in defining “black carbon” reported by modelling to ensure comparability with measurements obtained by different techniques.

Airborne particulate matter and diesel engine exhaust on infrastructure construction sites in the Copenhagen metropolitan area.

Diesel engine exhaust (DEE) is carcinogenic and potentially hazardous for those working in close proximity to diesel-powered machines. This study characterizes workplace exposure to DEE and its associated particulate matter (PM) during outdoor construction activities. We sampled at 4 construction sites in the Copenhagen metropolitan area. We used portable constant-flow pumps and quartz-fiber filters to quantify personal exposure to elemental carbon (EC), and used real-time instruments to collect activity-based information about particle number and size distribution, as well as black carbon (BC) concentration. Full-shift measurements of EC concentration ranged from < 0.3 to 6.4 µg/m3. Geometric mean (GM) EC exposure was highest for ground workers (3.4 µg/m3 EC; geometric standard deviation, GSD = 1.3), followed by drilling rig operators (2.6 µg/m3 EC; GSD = 1.4). Exposure for non-drilling-rig machine operators (1.2 µg/m3 EC; GSD = 2.9) did not differ significantly from background (0.9 µg/m3 EC; GSD = 1.7). The maximum 15-min moving average concentration of BC was 17 µg/m3, and the highest recorded peak concentration was 44 µg/m3. In numbers, the particle size distributions were dominated by ultrafine particles ascribed to DEE and occasional welding activities at the sites. The average total particle number concentrations (PNCs) measured in near-field and far-field positions across all worksites were 10,600 (GSD = 3.0) and 6,000 (GSD = 2.8)/cm3, respectively. Sites with active drilling rigs saw significantly higher average total PNCs at their near-field stations (13,600, 32,000, and 9,700/cm3; GSD = 2.4, 3.4, and 2.4) than sites without (4,700/cm3; GSD = 1.6). Overall, the DEE exposures at these outdoor construction sites were below current occupational exposure limits for EC (10 µg/m3 in Denmark; 50 µg/m3 in the European Union), but extended durations of exposure to the observed DEE levels may still be a health risk.

Spatio-temporal variation of aerosol optical depth and black carbon mass concentration over five airports across Bangladesh: emphasis on effect of COVID-19 lockdown

Globally, the COVID-19 outbreak has had a devastating impact on both health and economy. In contrast, the reduction in anthropogenic emissions has resulted in a major improvement in air quality. In this study, US National Aeronautics and Space Administration (NASA) satellite datasets and related reanalysis model data were used with validation using ground-based data to evaluate the effects of aviation-based emissions on aerosol optical depth (AOD) and black carbon (BC). The contributions from five airports in Bangladesh were assessed during the pre-lockdown (01 Jan to 22 March), lockdown (23 March to 30 May), and post-lockdown (31 May to 30 Aug) periods in 2019 and 2020. The study’s findings show that during the 2020 lockdown, AOD and BC concentrations significantly decreased at all five airports. The overall decline of AOD was ~ 18.5% (13.1% to 22.8%) and BC was ~ 18.1% (16.6% to 22.2%) in 2020 compared to 2019. The three international airports that were examined—Dhaka, Chattagram, and Sylhet—showed an average reduction of about ~ 9.7%, while Jashore and Barisal—two domestic airports—saw a minor increase in AOD of ~ 0.8% over the same period. However, the average BC concentration at both international and domestic airports dropped by ~ 9.8% and ~ 10.2%, respectively. This is the first study to use reanalysis datasets in Bangladesh to evaluate air pollution levels and aviation-based emissions. The results highlight the significant impact of reduced aviation activity on air quality and provide valuable insights for future air pollution management strategies.Graphical

Changes in the Direct Climate Effect of Black Carbon Aerosols in East Asia Under the “Dual Carbon” Goal of China

AbstractIn the context of China's “dual carbon” goal, emissions of air pollutants are expected to significantly decrease in the future. Thus, the direct climate effects of black carbon (BC) aerosols in East Asia are investigated under this goal using an updated regional climate and chemistry model. The simulated annual average BC concentration over East Asia is approximately 1.29 μg/m3 in the last decade. Compared to those in 2010–2020, both the BC column burden and instantaneous direct radiative forcing in East Asia decrease by more than 55% and 80%, respectively, in the carbon peak year (2030s) and the carbon neutrality year (2060s). Conversely, the BC effective radiative forcing (ERF) and regional climate responses to BC exhibit substantial nonlinearity to emission reduction, possibly resulting from different adjustments of thermal‐dynamic fields and clouds from BC‐radiation interactions. The regional mean BC ERF at the tropopause over East Asia is approximately +1.11 W/m2 in 2010–2020 while negative in the 2060s. BC‐radiation interactions in the present‐day impose a significant annual mean cooling of −0.2 to −0.5 K in central China but warming +0.3 K in the Tibetan Plateau. As China's BC emissions decline, surface temperature responses show a mixed picture compared to 2010–2020, with more cooling in eastern China and Tibet of −0.2 to −0.3 K in the 2030s, but more warming in central China of approximately +0.3 K by the 2060s. The Indian BC might play a more important role in East Asian climate with reduction of BC emissions in China.

Low-Cost Hourly Ambient Black Carbon Measurements at Multiple Cities in Africa.

There is a notable lack of continuous monitoring of air pollutants in the Global South, especially for measuring chemical composition, due to the high cost of regulatory monitors. Using our previously developed low-cost method to quantify black carbon (BC) in fine particulate matter (PM2.5) by analyzing reflected red light from ambient particle deposits on glass fiber filters, we estimated hourly ambient BC concentrations with filter tapes from beta attenuation monitors (BAMs). BC measurements obtained through this method were validated against a reference aethalometer between August 2 and 23, 2023 in Addis Ababa, Ethiopia, demonstrating a very strong agreement (R2 = 0.95 and slope = 0.97). We present hourly BC for three cities in sub-Saharan Africa (SSA) and one in North America: Abidjan (Côte d'Ivoire), Accra (Ghana), Addis Ababa (Ethiopia), and Pittsburgh (USA). The average BC concentrations for the measurement period at the Abidjan, Accra, Addis Ababa Central summer, Addis Ababa Central winter, Addis Ababa Jacros winter, and Pittsburgh sites were 3.85 μg/m3, 5.33 μg/m3, 5.63 μg/m3, 3.89 μg/m3, 9.14 μg/m3, and 0.52 μg/m3, respectively. BC made up 14-20% of PM2.5 mass in the SSA cities compared to only 5.6% in Pittsburgh. The hourly BC data at all sites (SSA and North America) show a pronounced diurnal pattern with prominent peaks during the morning and evening rush hours on workdays. A comparison between our measurements and the Goddard Earth Observing System Composition Forecast (GEOS-CF) estimates shows that the model performs well in predicting PM2.5 for most sites but struggles to predict BC at an hourly resolution. Adding more ground measurements could help evaluate and improve the performance of chemical transport models. Our method can potentially use existing BAM networks, such as BAMs at U.S. Embassies around the globe, to measure hourly BC concentrations. The PM2.5 composition data, thus acquired, can be crucial in identifying emission sources and help in effective policymaking in SSA.

Measurement of black carbon exposure in urban classrooms during rush hours

Traffic-related air pollutants are predominantly emitted in urban environments; therefore, analyzing their impact on indoor air quality (IAQ) is important. Effectively managing IAQ is vital, given the extensive duration individuals, particularly students, spend indoors. This study conducted a quantitative assessment of black carbon (BC) and indoor and outdoor particulate matter (PM2.5, particles with diameter ≤2.5 μm) concentrations in five South Korean classrooms to determine the root cause and effects of traffic-related air pollutants on indoor environments. The research specifically focused on indoor BC levels during rush hours, that is, periods marked by increased traffic volume. The analysis revealed that the mean indoor and outdoor BC concentrations in the five classrooms were measured at 1.03 (95% CI: 0.69, 1.36) and 1.38 (95% CI: 0.79, 1.96) μg/m3, respectively, while the mean PM2.5 concentrations were measured at 17.07 (95% CI: 12.92, 13.62) and 29.89 (95% CI: 10.88, 48.89) μg/m3, respectively. The indoor-to-outdoor (I/O) ratio of BC in the five classrooms during the occupied period was 0.77 (95% CI: 0.69, 0.84) and 0.62 (95% CI: 0.51, 0.72) for PM2.5. During the unoccupied period, the I/O ratio of BC was 0.68 (95% CI: 0.63, 0.72) and 0.53 (95% CI: 0.42, 0.63) for PM2.5. The rise in urban traffic increased the BC outdoor level by 47% and the PM2.5 concentration by 13%. Classrooms situated closer to roadways had higher BC levels than those located at a greater distance. During rush hours, the BC concentration in the classroom closest to the major road was 2.03 (95% CI: 1.78, 2.27) μg/m3, while the furthest classroom recorded a concentration of 0.88 (95% CI: 0.79, 0.96) μg/m3. During commuting times, classroom BC concentrations increased by up to 5.86 μg/m3 owing to student door-opening activities, increasing the I/O ratio by approximately 20%. Consequently, the average BC concentration in classrooms during rush hours was approximately double that recorded during non-rush hours (0.73 μg/m3). These findings are instrumental in developing strategies to enhance IAQ in educational settings and guiding urban planning decisions regarding the location of schools.

Black Carbon and Particulate Matter Concentrations: Air Pollution Levels in Rio de Janeiro, Brazil

This research explores the concentration of black carbon (BC) in particulate matter (PM10 and PM2.5) from ten monitoring stations in the Metropolitan Region of Rio de Janeiro (MRRJ), Bonsucesso (BS), Botafogo (BOT), Copacabana (COP), Gavea (GAV), Gericino (GER), Lagoa (LAG), Recreio dos Bandeirantes (REC), Santa Cruz (SC), Castelo (CAS) and Urca (URC), covering a range of pollution sources (vehicular, industrial, and residential). PM samples were collected using filter units every week from January 2018 to December 2019. Results revealed high concentrations of PM10 in BS (86 ± 22 µg m-3) and PM2.5 in REC (30 ± 11 µg m-3). Likewise, both monitoring stations exceeded the international limits. In 2019, BC in PM10 decreased in the following order: BS &gt; CAS &gt; GER &gt; BOT &gt; SC &gt; GAV. For 2018, BC in PM2.5 decreased as follows REC &gt; LAG &gt; SC, while 2019 REC &gt; GAV &gt; LAG &gt; COP &gt; URC. REC and BS have industrial and commercial activities and intense vehicular traffic. During the period of study, average BC concentrations in PM10 and PM2.5 were 3.3 ± 1.5 and 1.9 ± 0.70 µg m-3, respectively. These findings indicate that BC concentrations should be monitored and regulated in locations with high levels of traffic-related air pollution for offering new insights and guiding efforts to minimize emissions and enhance public health.

Spatiotemporal variations of atmospheric black carbon concentration and its correlation with meteorological and environmental factors in Xinjiang, China, from 2010 to 2022.

Black carbon (BC) is a pollutant produced by the combustion of fossil fuels and biomass fuels, which has a huge impact on regional climate, atmospheric environment, and human health. In this study, based on MERRA-2 reanalysis data and ground-based observation data, the Mann-Kendall (MK) test and random forest (RF) model were used to explore the spatiotemporal variation characteristics of atmospheric BC concentration in Xinjiang, China and its correlation with meteorological and environmental covariates in 2010-2022. The results showed that the use of MERRA-2 reanalysis data to explore the spatiotemporal variation characteristics of BC concentration in Xinjiang had high reliability (relative average deviation (RAD) = 0.65). From 2010 to 2022, the annual average concentration of atmospheric BC in Xinjiang was 195.40±15.55ng/m3, and the multi-year average change rate was -0.05%. The winter season had the highest atmospheric BC concentration (145.52 ± 39.31 ng/m3), followed by autumn (124.95±28.82 ng/m3), spring (74.05 ± 9.96 ng/m3), and summer (73.41 ± 5.69ng/m3). The atmospheric BC concentration had a significant spatial variation, showing two high-BC-concentration areas on the northern slope of the Tianshan Mountains (centered on Urumqi-Changji-Shihezi region) and the urban agglomeration around the Tarim Basin (centered on Kashgar). The RF model analysis showed that meteorological factors including snow depth, surface temperature, and humidity as well as environmental factors including NO2, PM10, and SO2 were the main factors affecting the BC concentration. This work is of great significance for clarifying the accumulation and spatial distribution characteristics of atmospheric BC in northwest China and the factors influencing the atmospheric BC concentration, and helps to raise public attention to the increasingly serious climate change and public health problems caused by BC.

Seasonal characterization of aerosols over high altitude location of southern India, Ooty, Tamilnadu

Climate change has been worsened by aerosols which got a significant place in the scientific research to understand climate change dynamics. Hence, the optical properties of the aerosols play an important role in the earth’s energy radiation budget. The Aerosol Optical Depth was measured at high altitude region in Ooty from December 2020 to May 2021. The spectral, monthly and diurnal variation of AOD were assessed and showed their seasonal variability. The mean AOD value at 500 nm was higher during the Summer season (0.625±0.323) than in the Winter season (0.213±0.006). The Black Carbon (BC) was measured using an Aethalo meter from December 2020 to September 2021. The average season wise concentrations of BC were 0.680±0.206µg m-3, 1.128±0.393 µg m-3 and 0.189±0.06 µg m-3 for the Winter, Summer and Monsoon seasons, respectively. The sources of BC mass concentration were apportioned based on fossil fuel (BCff) and biomass burning (BCbb). The fossil fuel based contribution was higher than the biomass based contribution to the total BC concentration. The comparative study of BC concentration with the AOD, it was projected that the AOD had increased in line with surging BC concentration up to April, 2021. The ground-based daily AOD measurements were compared with the MODIS retrieved AOD. The MODIS retrieved AOD was positively correlated with the ground measured AOD during the Winter and Summer seasons. The HYSPLIT trajectory presented the pathways of the source from the long range regions. The Winter season trajectory was attributed to the North-easterly and easterly winds and the Summer season was attributed to the North-westerly and westerly winds that exhibited the long-range transport of aerosols from the neighbouring cities. The meteorological parameters significantly affected the loading of aerosols during all the seasons, denoting that they were supposed to the local prevailing meteorological conditions.

Investigating Vertical Distributions and Driving Factors of Black Carbon in the Atmospheric Boundary Layer Using Unmanned Aerial Vehicle Measurements in Shanghai, China

Black carbon (BC) is a significant component of fine particulate matter (PM2.5, with aerodynamic diameters ≤ 2.5 μm), and its spatial distribution greatly affects the global radiation budget. However, the vertical distributions and key driving factors of BC in the atmospheric boundary layer, where BC is mostly concentrated, remain unclear. In this study, gradient measurements of BC were made using an unmanned aerial vehicle (UAV) platform from ground level to 500 m above ground level (AGL) during and after the 2016 G20 control period in Shanghai. Generally, vertical profiles of BC from local time (LT) 9 to 17 on all experimental days demonstrated an upward trend with increasing height. The BC emitted from chimneys was initially released at higher altitudes, resulting in the positive gradients of vertical BC profiles. Furthermore, with the progressive development of the boundary layer height from LT 9 to 15, the average concentration of BC per vertical profile decreased. However, meteorological conditions unfavorable for dispersions caused by particularly high temperatures, low wind speed, unfavorable boundary layer conditions, or especially high relative humidity, and hygroscopic growth owing to the extremely high relative humidity, led to an overall increase in vertical BC and ground-based PM2.5 and BC. Despite the impact of adverse meteorological conditions, emission control measures during the control period not only effectively decreased the BC concentration but also reduced the proportion of BC in PM2.5 in the atmospheric boundary layer. The results of this study can provide valuable observations for evaluating numerical model results and important implications for making control strategies of BC in the future.

Ambient black carbon variations and emission characteristics of typical Chinese vessels in the Yangtze River Delta, China.

Black carbon (BC) has a significant impact on air quality, climate change, and human health. Studies on BC from vessel exhaust have been focused on in recent years. To realize the contribution of BC from vessels to ambient air quality, 28 months of BC variation were observed from February 2019 to May 2022, including 3 fishing moratoriums and 2 normal periods. The results showed that the average daily concentration of BC in the fishing moratorium was significantly lower than that in the normal period. The difference proportion of the BC concentration between 370 and 880 nm was calculated over the whole period. As a result, the mean difference value in the fishing moratorium from February to May was 0.06 ± 0.07, and the normal period was -0.02 ± 0.05. The aethalometer model indicated that BC was greatly affected by fossil fuel combustion in the normal period. The effect of vessel emissions on regional BC concentrations was considerable. In addition, 16 PAHs and 21 elements in PM emitted from 24 vessels of different types were sampled and analyzed in Dianshan Lake and the Taipu River. EC accounted for the highest proportion (23.64%) in the sample of small trawlers compared to the emissions from cargo ships with large tonnages. The component profiles of vessel exhaust showed that Zn, As, phenanthrene (Phe), anthracene (Ant), fluoranthene (Fla), and pyrene (Pyr) were the dominant species, although some of these species were mainly recognized as characteristic factors of coal combustion. To improve the accuracy of identifying the vessel source, the diagnostic ratios of Ant/(Ant + Phe), BaA/(BaA + Chr), Phe/Ant, and BaA/Chr were provided, and they exhibited the obvious characteristics of fuel combustion.

Characteristics of atmospheric black carbon and its wet scavenging in Nanning, South China

Based on in-situ measurement of black carbon (BC) and carbon monoxide (CO), the characteristics of BC emissions and wet scavenging were comprehensively investigated in Nanning, South China. The average annual BC concentration was 1.02 ± 0.53 μg m−3 with higher pollution levels during winter. In winter, a higher net BC/CO (ΔBC/ΔCO) ratio of 3.3 ± 0.3 ng m−3 ppb−1 along with an increased absorption Ångström exponent (AAE) and BC mass from biomass burning (BCbb), indicated a significant contribution of biomass burning to BC emissions. However, emissions from the traffic sector consistently exerted a dominant influence throughout the year. Cluster analysis of backward trajectories identified three types of air masses with distinct origins. Cluster #1 originated from Guangxi province and its vicinity, intermittently influencing the sampling site throughout the year with varying effects between winter and summer. This air mass brought in clean sea breeze in summer whereas transported a higher proportion of BCbb to the site during wintertime due to local open biomass burning. Cluster #3 primarily arrived in autumn and winter (October–December) from polluted central China, resulting in substantially high BC mass at the site. Cluster #2 coincided with the period (January–March) when extensive surface open biomass burning events occurred in Southeast Asia (SEA) regions. These BC aerosols in cluster#2 initially rose to higher altitudes above SEA before being regionally transported, but were significantly scavenged by clouds and precipitation during vertical uplift. The remaining BC exhibited a notably lower BC loss rate on relative humidity (RH) of −0.01 ng m−3 ppb−1 %−1 compared to cluster #1 (−0.03) and cluster #3 (−0.06), corresponding to an average BC transport efficiency of 0.85, 0.73, and 0.53, respectively. Nonetheless, air masses in cluster #2 could still transport considerably high BC mass to Nanning due to dry conditions and less wet scavenging along trajectory pathways. These findings provide valuable insights for policymakers and government officials in regulating and mitigating BC pollution in South China.

Evaluation of MERRA-2 Black Carbon Characteristics and Potential Sources over China

Black carbon (BC), an important component of atmospheric aerosol, plays a significant role in regional climate, hydrological cycle, variation of monsoon rainfall, and human health. The 40-year detailed atmospheric BC over China from 1981 to 2020 is systematically investigated through the MERRA-2 reanalysis dataset. MERRA-2 BC generally showed a good correlation (R = 0.68) compared with 673 monthly samples from ground-based observation at 35 stations around China. The overall annual average of MERRA-2 BC concentration over China is 1.15 μg/m3, with a fast growth rate during 1981–2007 and a relatively slow decrease after that. The winter season has the highest mean concentration of BC, followed by autumn and spring, whereas summer shows relatively weaker values. The order of annual average BC concentrations during 1981–2020 is Beijing-Tianjin-Hebei region (BTH, 4.02 μg/m3) &gt; Sichuan Basin (SB, 3.94 μg/m3) &gt; Yangtze River Delta (YRD, 2.68 μg/m3) &gt; Pearl River Delta (PRD, 1.47 μg/m3). The monthly mean BC concentrations over the BTH, YRD, PRD and SB are estimated to be smallest 3.18 μg/m3 in May, 1.94 μg/m3 in August, 0.82 μg/m3 in July, 3.04 μg/m3 in June, respectively, whilst largest consistently in December with 5.09 μg/m3, 3.83 μg/m3, 2.12 μg/m3, and 5.41 μg/m3, respectively. Our study indicates the primary potential source areas for BC are concentrated in the research city and its surroundings. Beijing and Chengdu are more BC-polluted areas than Shanghai and Guangzhou. Long-distance, regional transfer from south BTH contributes importantly to BC pollution in Beijing under the influence of prevailing southerly winds. The geographical location of Chengdu causes the transport and accumulation of BC inside the SB.

Black carbon emissions in the rural Indian households: Sources, exposure, and associated threats

In this study, we present the indoor Black Carbon (BC) measurements with the help of Aethalometer (AE‐33) from various sites in Eastern India in a typical kitchen room situated in a rural area. Analysis was done on how various cooking activities performed in the home affected the indoor level of BC. The activities resulting in elevated indoor concentrations included three different periods of cooking breakfast, lunch, and dinner with three different kinds of kitchen structures open, semi‐open and closed kitchen. Close kitchen resulted in the highest BC concentrations, while open kitchen resulted in the lowest level. The burning of low‐grade fuels resulted in the largest increases in indoor BC concentration. We calculated the average BC concentrations for three distinct kitchens, with open kitchens emitting 260.14 μgm−3, semi‐open kitchens emitting 441.14 μgm−3, and closed kitchens emitting 477.25 μgm−3. The biomass burning % was high during the entire research. Because BC mass concentration was found to be high in indoor sampling, as a result, the health risk assessment is also considered to be high in all types of kitchens. As people spend a significant amount of time at home, especially in a future where remote work is anticipated to be easier, finding the activities, sources, and health effects that increase indoor pollution is vital to lowering indoor exposure.

Black carbon in contrasting environments in India: Temporal variability, source apportionment and radiative forcing

Analyses of black carbon (BC) data from three different environments in India - Delhi megacity, Srinagar metropolitan and Gulmarg hill station, showed that Delhi had the highest annual average BC concentration (12.3 ± 10.2 μg m−3), followed by Srinagar (4.3 ± 5 μg m−3) and Gulmarg (2.4 ± 2 μg m−3). The inflow of aerosols from the neighboring agricultural regions, notably during Winter, causes Delhi to have the highest seasonal average BC (16.8 μg m−3). Srinagar had the highest average seasonal BC during autumn (6.3 μg m−3) due to the burning of horticulture residue and hardwood for charcoal making and residential heating. At Gulmarg, on the other hand, the winter season's high BC (2.2 μg m−3) is due to the increased emissions from the tourist traffic, snowmobile/ATVs and wood burning for residential heating. BC concentrations in Delhi and Srinagar were roughly in line with their population size. However, compared to sites with the similar population, BC at Gulmarg was roughly twice higher than the other sites. There was a higher contribution to BC from fossil fuels than biomass burning at all three sites, which indicates that cars are the primary source of BC. Overall, values of BC aerosol optical properties in Delhi are much higher than those in Srinagar and Gulmarg. During the cold season, continental air masses transport BC from the neighboring areas to Delhi and westerlies enhance the local BC loading at Srinagar and Gulmarg. The predominant presence of absorbing aerosols, particularly BC, during late autumn and winter at all three sites leads to an increase in aerosol optical depth (AOD), a reduction in single scattering albedo (SSA) and an increase in asymmetry parameter (AP). As a result, there is a significant increase in the radiative forcing of the atmosphere (RFATM), with the highest values observed in January in Delhi (+71.5 W m−2) and Srinagar (+56.05 W m−2), and in November at Gulmarg (+18.5 W m−2). These findings suggest that small rural towns that are affected by seasonal emissions, low planetary boundary layers, and frequent temperature inversions, can contribute to a substantial amount of radiative forcing. This study provides a larger perspective on increasing BC in Delhi, and urban-rural fringe areas in the Indian Himalayas, which is crucial for identifying what actions must be taken to control BC emissions to reduce impacts on cryosphere, human health and other sectors.

Whether cycling around the city is in fact healthy in the light of air quality – Results of black carbon

Studying the air quality and exposure of the inhabitants of urban agglomerations to pollution is the basis for the creation and development of more sustainable cities. Although research on black carbon (BC) has not yet reached the official acceptable levels and guidelines, the World Health Organization clearly indicates the need to measure and control the level of this pollutant. In Poland, monitoring of the level of BC concentration is not included in the air quality monitoring network. To estimate the extent of this pollutant to which pedestrians and cyclists are exposed, mobile measurements were carried out on over 26 km of bicycle paths in Wrocław. The obtained results indicate the influence of urban greenery next to the bicycle path (especially if the cyclist is separated from the street lane by hedges or other tall plants) and the ‘breathability’ (i.e., associated with surrounding infrastructure) of the area on the obtained concentrations; the average concentration of BC in such places ranged from 1.3 to 2.2 μg/m3, whereas a cyclist riding directly on bike paths adjacent to the main roads in the city center is exposed to concentrations in the range of 2.3–14 μg/m3. The results of the measurements, also related to stationary measurements made at a selected point of one of the routes, clearly indicate the importance of the infrastructure surrounding the bicycle paths, their location, and the impact of urban traffic on the obtained BC concentrations. The results presented in our study are based only on short-term-field campaigns preliminary studies. To determine the quantitative impact of the characteristics of the bicycle route on the concentration of pollutants, and thus the exposure of users, the systematized research should cover a greater part of the city and be representative in terms of various hours of the day.

Mobile measurements of black carbon: Comparison of normal traffic with reduced traffic conditions during COVID-19 lock-down

A mobile monitoring campaign was conducted (by bicycle) to assess the black carbon (BC) concentrations in Cluj-Napoca city, Romania, in 2020, before, during and after COVID-19 lock-down. Over the entire study period, the BC concentrations ranged between 1.0 and 25.9 μg/m³ (averaged per street section and period characterized by different traffic conditions). Marked spatial and temporal differences were observed. Observed differences in BC concentrations between locations are attributed to traffic intensities, with average BC concentrations, under normal circumstances, of 6.6–14.3 μg/m³ at roads with high to intense traffic, compared to 2.8–3.1 μg/m³ at areas with reduced traffic, such as residential areas, parks and pedestrian streets. The COVID-19 measures impacted traffic volumes, and hence average BC concentrations decreased from 5.9 μg/m³ to 3.0 μg/m³ during lock-down and in a lower extent to 3.4 μg/m³ and 4.4 μg/m³ in post-lockdown periods with reduced and more normalized traffic. Two approaches to account for variations in background concentrations when comparing different situations in time are assessed. Subtracting background concentrations that are measured at background sites along the monitoring route is an appropriate method to assess spatio-temporal differences in concentrations. A reduction of about 1–2 μg/m³ was observed for the streets with low to medium traffic, and up to 6 μg/m³ at high traffic locations under lockdown. The approach presented in this study, using mobile measurements, is useful to understand the personal exposure to BC along the roads in different seasons and the influence of traffic reduction on BC pollution during prolonged restrictions. All these will support policymakers to reduce pollution and achieve EU directives targets and WHO recommendations.

Emission characteristics and light absorption apportionment of carbonaceous aerosols: A tunnel test conducted in an urban with fully enclosed use of E10 petrol

To reduce the heavy dependence on petroleum, bioethanol has been increasingly employed as an alternative and sustainable transportation fuel. However, the characteristics of black carbon (BC) emissions from E10 petrol vehicles (i.e., ethanol-gasoline containing 10% ethanol) are still unclear, especially under real driving conditions. Here, a tunnel test was conducted during a cold winter. This tunnel was characterized by heavy traffic comprising more than 98% E10-fueled gasoline vehicles (GVs). Real-time BC concentrations, traffic parameters and meteorological conditions were recorded during the sampling campaign. The average BC concentration inside the tunnel (10.94 ± 5.02 μg m−3) was almost twice the background concentration. Based on aethalometer AE33 in situ measurements and the minimum R-squared (MRS) method, real-time aerosol light absorption was apportioned. The light absorption proportions of BC, primary brown carbon (BrC1) and secondary brown carbon (BrC2) were 79.86%, 2.78% and 17.36%, respectively, at 370 nm. The BC emission factor (EFBC) of the E10-fueled vehicles was 1.09 ± 0.49 mg km−1·veh−1 and 15.24 ± 6.85 mg·(kg fuel)−1, lower than those of traditional gasoline fueled vehicles in previous studies. This study can support the compilation of vehicular BC emission inventories, provide recommendations for biofuel policies and contribute to comprehensively understanding the climatic impact of E10 petrol.