Average Black Carbon Concentrations Research Articles

Emission reduction of black carbon and polycyclic aromatic hydrocarbons during COVID-19 pandemic lockdown.

The global pandemic COVID-19 necessitated various responses throughout the world, including social distancing, use of mask, and complete lockdown. While these measures helped prevent the community spread of the virus, the resulting environmental benefits of lockdown remained mostly unnoticed. While many studies documented improvements in air quality index, very few have explored the reduction in black carbon (BC) aerosols and polycyclic aromatic hydrocarbons (PAHs) concentrations due to lockdown. In this study, we evaluated the changes in concentrations of BC, PAHs, and PM2.5 before and during the lockdown period. Our results show that lockdown resulted in a significant reduction in concentrations of these pollutants. The average mass concentration of BC, PAHs, and PM2.5 before the lockdown was 11.71 ± 3.33 μgm−3, 108.71 ± 27.77 ngm−3, and 147.65 ± 41.77 μgm−3, respectively. During the lockdown period, the concentration of BC, PAHs, and PM2.5 was 2.46 ± 0.95 μgm−3, 23.19 ± 11.21 ngm−3, and 50.31 ± 11.95 μgm−3, respectively. The diagnostic ratio analysis for source apportionment showed changes in the emission sources before and during the lockdown. The primary sources of PAHs emissions before the lockdown were biomass, coal combustion, and vehicular traffic, while during the lockdown, PAHs emissions were primarily from the combustion of biomass and coal. Similarly, before the lockdown, the BC mass concentrations came from fossil-fuel and wood-burning, while during the lockdown period, most of the BC mass concentration came from wood-burning. Human health risk assessment demonstrated a significant reduction in risk due to inhalation of PAHs and BC-contaminated air.

Premature Mortality Associated with Exposure to Outdoor Black Carbon and Its Source Contributions in China

Epidemiological studies have shown that outdoor black carbon (BC) has higher health risks than other constituents and the total fine particulate matter (PM2.5). In this study, we estimated premature mortality attributed to BC in China in 2013 using a health impact model combined with annual average BC concentrations predicted using the Community Multi-scale Air Quality model. Source contributions to BC from six different source sectors were estimated using the source-oriented method, including residential, industrial, transportation, open burning, power, and other sources. The sensitivity of BC-related premature mortality to emission reductions in different sources was quantified in different regions of China. The results showed that the total all-cause premature mortality related to BC was approximately 1,436,957 (95% CI: 998,746–2,029,210) in China in 2013. Residential, industrial, and transportations sources were the three main sources of BC-induced premature mortality. Central China, Yangtze River Delta, and Sichuan Basin had the highest BC-induced mortality due to a high level of emissions and a dense population. A sensitivity test by assuming the same exposure-response coefficient of BC as the total PM2.5 showed the number of deaths was 265,122 thousand (95% CI: 541,90, 445,943) which can be treated as the lower limit of the BC-related mortality in China. Despite the uncertainties in estimates, it is suggested that reducing BC emissions in China would lead to significant health benefits. Controlling BC from industrial and transportation sources would bring more relative mortality reductions, from a percentage point of view, in most provinces of China.

Temporal variations of black carbon, carbon monoxide, and carbon dioxide in Mexico City: Mutual correlations and evaluation of emissions inventories

Black carbon (BC), carbon monoxide (CO), and carbon dioxide (CO2) were measured in Mexico City (UNAM observatory) with a Photoacoustic Extinctiometer-PAX (BC) and a Cavity Ring-Down Spectroscopy analyzer-CRDS (CO and CO2), from November 2014 to July 2016. The objective of this study was to determine temporal variations of BC, CO, and CO2, their mutual correlations, and evaluation of the Mexico City emission inventory. The highest concentrations of pollutants were detected in cold dry season. The average concentrations of BC, CO, and CO2, for the entire period, were 2.95 μg m−3, 0.64 ppm, and 421.81 ppm, respectively. We calculated ΔBC/ΔCO, ΔBC/ΔCO2, and ΔCO/ΔCO2 using three methods to obtain a confidence interval for the emission ratios. BC, CO, CO2 concentrations, and the ΔBC/ΔCO ratio were maximum in the early morning, while the ΔBC/ΔCO2 and ΔCO/ΔCO2 peak was maximum in the afternoon. BC and CO have a weekday/weekend difference. The estimated slopes (ΔBC/ΔCO, ΔBC/ΔCO2, and ΔCO/ΔCO2) were compared with the emission ratios (BC/CO, BC/CO2, and CO/CO2) derived of the 2016 Mexico City emissions inventory. For mobile sources, the emission ratios of BC/CO and BC/CO2 were within the measurement range of ΔBC/ΔCO and ΔBC/ΔCO2, while CO/CO2 was underestimated in the emission inventory.

One-Year Real-Time Measurement of Black Carbon in the Rural Area of Qingdao, Northeastern China: Seasonal Variations, Meteorological Effects, and the COVID-19 Case Analysis

In this paper, we report the results obtained from one year of real-time measurement (i.e., from December 2019 to November 2020) of atmospheric black carbon (BC) under a rural environment in Qingdao of Northeastern China. The annual average concentration of BC was 1.92 ± 1.89 μg m−3. The highest average concentration of BC was observed in winter (3.65 ± 2.66 μg m−3), followed by fall (1.73 ± 1.33 μg m−3), spring (1.53 ± 1.33 μg m−3), and summer (0.83 ± 0.56 μg m−3). A clear weekend effect was observed in winter, which was characterized by higher BC concentration (4.60 ± 2.86 μg m−3) during the weekend rather than that (3.22 ± 2.45 μg m−3) during weekdays. The influence of meteorological parameters, including surface horizontal wind speed, boundary layer height (BLH), and precipitation, on BC, was investigated. In particular, such BLH influence presented evidently seasonal dependence, while there was no significant seasonality for horizontal wind speed. These may reflect different roles of atmospheric vertical dilution on affecting BC in different seasons. The △BC/△CO ratio decreased with the increase of precipitation, indicative of the influence of below-cloud wet removal of BC, especially during summertime where rainfall events more frequently occurred than any of other seasons. The bivariate-polar-plot analysis showed that the high BC concentrations were mainly associated with low wind speed in all seasons, highlighting an important BC source originated from local emissions. By using concentration-weighted trajectory analysis, it was found that regional transports, especially from northeastern in winter, could not be negligible for contributing to BC pollution in rural Qingdao. In the coronavirus disease 2019 (COVID−19) case analysis, we observed an obvious increase in the BC/NO2 ratio during the COVID-19 lockdown, supporting the significant non-traffic source sector (such as residential coal combustion) for BC in rural Qingdao.

Characteristics, potential regional sources and health risk of black carbon based on ground observation and MERRA-2 reanalysis data in a coastal city, China

Black carbon (BC) produced by the incomplete combustion of carbonaceous materials and biomass has become a major factor affecting global climate change and adversely affects health. Based on the ground-measured data and MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications, Version 2) reanalysis data, BC's pollution characteristics and the health risks caused by BC exposure were investigated in Tianjin, China. The results showed that the highest BC concentration occurred in winter, and the annual average concentration of BC on weekends was higher than that on weekdays in winter. The hourly average monitoring concentration variations of BC in four seasons all had two peaks that appeared 6:00–8:00 and 22:00–2:00. For MERRA-2 reanalysis data, there was one peak appeared during 5:00–7:00 in four seasons. The lowest values appeared during 14:00–16:00 for both ground-measured data and MERRA-2. The relationships between BC concentration and meteorological factors showed that wind speed and temperature inversion played important roles in the atmospheric BC diffusion. The wind directions of southwest, southeast, and north were closely associated with BC in 2019. The Potential Source Contribution Function (PSCF) results showed that the southwestern area of Tianjin, especially the southern Hebei, northern Henan and Beijing, would be the potential source areas of Tianjin BC in 2019. The cancer risks of adults and children caused by BC exposure in Tianjin were higher than the risk levels (1 × 10−6 to 1 × 10−4) recommended by the US Environmental Protection Agency (US EPA) in 2019, resulting in more than 3.78 cases of cancer per 10,000 adults (3.78 × 10−4), and more than 1.55 cases of cancer per 10,000 children (1.55 × 10−4), respectively. The relative risk (RR) of BC exposure on mortality showed the highest in winter and the lowest in summer. Compared with all-cause and cardiovascular mortality, respiratory mortality caused by the BC showed the highest risk.

The black carbon dispersion in the Southern Hemisphere and its transport and fate to Antarctica, an Anthropocene evidence for climate change policies.

Black carbon (BC) has been measured in Antarctica's air, and its global warming effect can potentially speed up the ice melting in the most solid water reservoir of the planet. However, the primary responsible sources are not well evidenced in this region. The dispersion of black carbon emissions from the Southern Hemisphere was conducting using atmospheric chemical transport model and we compared the results with satellite registries from March 1st to April 30th in 2014. The emission inventory considered the anthropogenic and biomass burning emissions from global datasets. The largest and most populated cities in Southern Hemisphere showed the higher emission of BC. As a result, the average daily concentrations of atmospheric BC were around 4ng/m3 in most regions of Antarctica according to its pristine characteristics. We analyzed fifteen relevant sites in coastal zones of Antartica and some peaks registered by the satellite records were not replicated by model outputs and it was mainly associated with the lack of emissions. Finally, we made simulations in the same period without biomass burning emissions and we observed decreased concentrations of BC in the range of 20-50%. As a result, we show that the black carbon transportation from the continental land to the polar region took place in 17-24days during the Austral summer and the biomass burning emissions were the primary source. Black Carbon deposition in Antarctica is not permanent, but the uncontrolled emissions from Southern Hemisphere can increase its transportation to the white continent and make its accumulation during the period when the weak polar vortex occurs.

Variations in Black Carbon concentration and sources during COVID-19 lockdown in Delhi

A nationwide lockdown was imposed in India due to COVID-19 pandemic in five phases from 25th March to May 31, 2020. The lockdown restricted major anthropogenic activities, primarily vehicular and industrial, thereby reducing the particulate matter concentration. This work investigates the variation in Black Carbon (BC) concentration and its sources (primarily Fossil Fuel (ff) burning and Biomass Burning (bb)) over Delhi from 18th February to July 31, 2020, covering one month of pre-lockdown phase, all the lockdown phases, and two months of successive lockdown relaxations. The daily average BC concentration varied from 0.22 to 16.92 μg/m3, with a mean value of 3.62 ± 2.93 μg/m3. During Pre-Lockdown (PL, 18th Feb-24th March 2020), Lockdown-1 (L1, 25th March-14th April 2020), Lockdown-2 (L2, 15th April-3rd May 2020), Lockdown-3 (L3, 4th-17th May 2020), Lockdown-4 (L4, 18th-31st May 2020), Unlock-1 (UN1, June 2020), and Unlock-2 (UN2, July 2020) the average BC concentrations were 7.93, 1.73, 2.59, 3.76, 3.26, 2.07, and 2.70 μg/m3, respectively. During the lockdown and unlock phases, BC decreased up to 78% compared to the PL period. The BC source apportionment studies show that fossil fuel burning was the dominant BC source during the entire sampling period. From L1 to UN2 an increasing trend in BCff contribution was observed (except L3) due to the successive relaxations given to anthropogenic activities. BCff contribution dipped briefly during L3 due to the intensive crop residue burning events in neighboring states. CWT analysis showed that local emission sources were the dominant contributors to BC concentration over Delhi.

Characterization of black carbon aerosol at the summit of Mount Tai (1534 m) in central east China: Temporal variation, source appointment and transport

As a crucial absorption component of aerosols, black carbon (BC) plays a key role in modifying aerosol-planetary boundary layer (PBL) meteorology and hence aggravating haze pollution. With an altitude of 1534 m, Mt. Tai is close to the top of the PBL and located within the transportation channel from the North China Plain (NCP) to the Yangtze River Delta (YRD). In this study, BC aerosols were continuously observed using a seven-channel aethalometer (AE-33) at the summit of Mt. Tai from May 11 to June 25, 2017. The temporal variation, source and transport characteristics of BC in the upper PBL of central and eastern China in summer were then discussed. The average concentrations of BC, BCliquid and BCsolid were 1722.6, 1194.6 and 545.8 ng m−3, respectively, during the observation period. Liquid fuel sources were calculated and accounted for 64.7% of the BC mass concentration. The distributions of BC were mostly centralized in concentrations less than 600 ng m−3 (accounting for 21.9% of the total BC samples) and ranged from 1400 to 2200 ng m−3 (32.5%). Meteorological elements were determined to have great impacts on the distribution of BC concentrations, which increased with the decrease in visibility and wind speed and the increase in relative humidity (RH). The diurnal variations in BC presented high values during the daytime and low values during the nighttime, with peaks at 06:00, 11:00 and 18:00. Long-range transport from the YRD regions in summer, as well as the surrounding regions, played an important role in determining the BC concentrations at Mt. Tai with concentration weighted trajectory (CWT) values exceeding 2000 ng m−3. Air masses may move northward to the NCP after passing through Mt. Tai, and they contributed more than 1800 ng m−3 to the BC in the whole NCP region.

Continuously observed light absorbing impurities in snow cover over the southern Altai Mts. in China: Concentrations, impacts and potential sources

The deposition of light absorbing impurities (LAIs) (e.g., black carbon (BC), organic carbon (OC), mineral dust (MD)) on snow is an important attribution to accelerate snowmelt across the northern Xinjiang, China. At present, there is still a lack of understanding of the LAIs concentration, elution and enrichment process in snow cover over Xinjiang. Based on these, continuously sampling during two years carried out to investigate the concentrations, impacts and potential sources of LAIs in snow at Kuwei Station in the southern Altai Mountains. The average concentrations of BC, OC and MD in the surface snow were 2787 ± 2334 ng g −1 , 6130 ± 6127 ng g −1 , and 70.03 ± 62.59 μg g −1 , respectively, which dramatically increased along with snowmelt intensified, reflecting a significant enrichment process of LAIs at the snow surface. Besides, high LAIs concentrations also found in the subsurface and melting layers of the snowpit, reflecting the elution and redistribution of LAIs. With the simulation of the SNow ICe Aerosol Radiative model, BC was the main dominant factor in reducing snow albedo and radiative forcing (RF), its impact was more remarkable in the snowmelt period. The average contribution rates of BC, MD and BC + MD to snow albedo reduction increased by 20.0 ± 1.9%, 13.0 ± 0.2%, and 20.5 ± 2.3% in spring compared with that in winter; meanwhile, the corresponding average RFs increased by 15.8 ± 3.4 W m −2 , 4.7 ± 0.3 W m −2 and 16.4 ± 3.2 W m −2 , respectively. Changes in the number of snowmelt days caused by BC and MD decreased by 3.0 ± 0.4 d to 8.3 ± 1.3 d. It indicated that surface enrichment of LAIs during snow melting might accelerate snowmelt further. Weather Research and Forecasting Chemistry model showed that the resident emission was the main potential source of BC and OC in snow. This implied that the mitigation of intensive snowmelt needs to mainly reduce resident emission of LAIs in the future. • Light absorbing impurities (LAIs) in snowpit were analyzed in the Altai Mountains. • A significant enrichment process of LAIs appeared on snow surface. • Black carbon (BC) had a greater role in snow albedo, radiative forcing and snowmelt than mineral dust. • Residential emission was the main source of BC and organic carbon deposited on snow. Capsule: Vertical variations and enrichment process of LAIs concentrations in snowpit were analyzed in the southern Altai Mountains.

Black Carbon in the Near-Surface Atmosphere Far Away from Emission Sources: Comparison of Measurements and MERRA-2 Reanalysis Data

We compare the time variations in monthly average concentrations of black carbon in the surface air layer obtained from field measurements ([BC]) and from MERRA-2 reanalysis ([BC]M) at four monitoring sites located in the northern part of Russia (Tiksi Observatory, Pechora-Ilych Biosphere Reserve), Alaska (Barrow station), and Greenland (Summit station). It is shown that the MERRA-2 reanalysis data for the regions of Tiksi and Barrow do not completely reflect the [BC] variations during the year, in contrast to the Pechora-Ilych Biosphere Reserve, where the discrepancies are within 30–50%. The [BC]M reanalysis products for the Summit monitoring site qualitatively agree with the measurements characterizing the BC content in the free troposphere, but they underestimate [BC] by more than a factor of two. On the whole, our analysis showed that the results of the MERRA-2 reanalysis of the monthly average indices of near-surface concentration of atmospheric black carbon can be used for climate assessments for hard-to-reach northern regions in the warm season with an error of about 30%. Possible causes for the discrepancies between [BC] and [BC]M are discussed for different times of the year and observation sites.

Exposure assessment of elemental carbon, ultrafine particles, and crystalline silica at highway toll booths

Highway toll booth workers have been reported to be at an increased risk of occupational lung cancer. Moreover, insufficient studies have been performed on exposure assessment of workers at highway toll booths. Elemental carbon (EC), black carbon (BC), and respirable crystalline silica (RCS) concentrations were measured at highway toll booths in Gyeongsangbuk-do (Republic of Korea). The particle number (PN) concentration and size distribution of ultrafine particle were measured using three SMPS devices. The average concentration of the EC inside the booth was 3.3 μg/m<sup>3</sup>, with the maximum being 5.8 μg/m<sup>3</sup>. The concentrations of EC were highest for booths that operated exclusively for trucks. The average PN concentration inside the booth was 3.54 × 10<sup>4</sup> cm<sup>-3</sup>, approximately 5-fold higher than the reference indoor background. The average BC concentration in the booths were approximately 8 μg/m<sup>3</sup>, and the instantaneous peak concentration was 271 μg/m<sup>3</sup>. The RCS was below the detection limit in all samples. This study revealed that toll workers were most frequently exposed to diesel engine particle less than 100 nm, with an extremely high respiratory deposition rate. Therefore, a respiratory protection program is necessary to safeguard these workers against vehicle-related pollutants.

Distribution Characteristics and Source of Black Carbon Aerosols in the Northern Suburbs of Nanjing

Black carbon (BC) is an important component of atmospheric particulate matter (PM) emitted during the combustion process. Light absorption and scattering exhibited by BC affect the exchange of solar energy on Earth. In this study, continuous measurements of atmospheric particulate BC were carried out, using a BC analyzer (AE33) in the suburban area of Nanjing from January 2019 to May 2019, to realize the diurnal variations of BC during the different seasons and potential sources of BC during the clean (CD, PM2.5<35 μg ·m-3) and haze days (PD, PM2.5>75 μg ·m-3). The results showed that the average concentration of BC was (3.8±2.3) μg ·m-3; a higher average BC concentration value of (4.3±2.6) μg ·m-3 was observed during the winter, exceeding that during the spring period by a factor of 1.3. The higher BC concentrations during the winter was attributed to the stagnant weather conditions and additional emissions. Significant diurnal cycles of BC were observed with higher BC concentrations during rush hours of traffic, suggesting traffic origins. The Ångström exponent were 1.32 and 1.30 during the spring and winter periods, respectively, indicating that the BC was mainly produced from the traffic emissions during both the seasons. This hypothesis was also supported by the average BC/CO ratio of 0.005, which was similar to that of BC derived by traffic emissions. Moreover, we discovered that the contributions of traffic emissions to BC were 68%-87% and 72%-86% during the haze and clean periods, respectively. This indicated enhanced contributions of coal combustion and biomass burning to BC in Nanjing during the haze events. Finally, using the potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analysis, we highlighted that the BC at the receptor site was mainly from the local emissions in the surrounding areas of Nanjing.

Susceptibility of individuals with chronic obstructive pulmonary disease to respiratory inflammation associated with short-term exposure to ambient air pollution: A panel study in Beijing

BackgroundChronic obstructive pulmonary disease (COPD) is a leading cause of death worldwide. There is no clear evidence of whether COPD patients are more susceptible to respiratory inflammation associated with short-term exposure to air pollutants than those without COPD. ObjectivesThis study directly compared air pollutant-associated respiratory inflammation between COPD patients and healthy controls. MethodsThis study is based on the COPDB panel study (COPD in Beijing). Fractional exhaled nitric oxide (FeNO) was repeatedly measured in 53 COPD patients and 82 healthy controls at up to four clinical visits. Concentrations of carbon monoxide (CO), nitrogen monoxide, nitrogen dioxide (NO2), sulfur dioxide (SO2), fine particulate matter (PM2.5), black carbon (BC), ultrafine particles (UFPs), and accumulated-mode particles (Acc) were monitored continuously at a fixed-site monitoring station. Linear mixed-effects models were used to compare the associations between ln-transformed FeNO and average 1–23 h concentrations of air pollutants before the clinical visits. ResultsFeNO was positively associated with interquartile range (IQR) increases in average concentrations of CO, NO2, SO2, BC, UFPs, and Acc in all participants, with the strongest associations in different time-windows (range from 6.6% for average 1 h NO2 exposure to 32.1% for average 7 h SO2 exposure). Associations between FeNO and average 13–23 h PM2.5 exposure differed significantly according to COPD status. Increases in FeNO associated with average 1–2 h NO exposure were significant in COPD patients (range 8.9–10.2%), while the associations were nonsignificant in healthy controls. Associations between FeNO and average 1–23 h CO and SO2 exposure tended to be higher in COPD patients than in healthy controls, although the differences were not significant. UFPs-associated respiratory inflammation was robust in both subgroups. ConclusionsCOPD patients are more susceptible to respiratory inflammation following PM2.5, NO, CO, and SO2 exposure than individuals without COPD.

Results of Studying Physicochemical Characteristics of Atmospheric Aerosol in the 71st Cruise of RV Akademik Mstislav Keldysh

In summer 2018 along the route of the 71st cruise of RV Akademik Mstislav Keldysh in the North Atlantic we carried out the measurements of such atmospheric aerosol characteristics as aerosol optical depth, near-surface aerosol and black carbon concentrations, content of chemical elements in aerosol samples, and organic and elemental carbon, as well as the isotopic composition of black carbon. It is shown that the average values of most characteristics decrease severalfold during passage from the Baltic Sea to the North Atlantic (57°–60° N), and then to the Norwegian Sea. For instance, the average black carbon concentration decreased from 83 to 29 ng/m3. Episodic impact of continental aerosol was noted even in remote regions of ocean. Outflow of smokes from forest fires in the north of Canada to the region of measurements (southward of Greenland) had the strongest effect on aerosol characteristics. The average concentrations of chemical elements in aerosol composition over the North Atlantic were several times larger than in the Arctic region, and smaller than in the background region of Siberia.

The spatio-temporal evolution of black carbon in the North-West European ‘air pollution hotspot’

Particulate black carbon has a range of negative impacts on health, the environment and climate, however despite this there are relatively few long-term studies on its ambient distribution as a tropospheric air pollutant. In order to address this lack of data, to help to provide greater insight into the spatio-temporal distribution of particulate black carbon and to assess potential influencing factors, a new, permanent suburban monitoring network was established with sites in four northwest European cities: London (UK), Leicester (UK), Amsterdam (the Netherlands) and Antwerp (Belgium). We report here an analysis of the first measurements made by the network over a twenty-seven-month period (January 01, 2013–April 01, 2015), alongside data from pre-existing comparator urban roadside (AURN Marylebone Road, London, UK) and rural background (AURN Auchencorth Moss, Scotland) sites. The temporal evolution of black carbon was investigated at each site, as were associations with other commonly monitored pollutants (e.g. O3, NOx, PM2.5, PM10) and wind fields. Results showed clear anthropogenic signatures across the diurnal, weekly and annual timeframes, and positive correlations were obtained between black carbon measurements and other common traffic-related pollutants, highlighting the importance of vehicle emissions as a major contributor to ambient black carbon concentration in northwest Europe. Average black carbon concentrations varied from 6.6 μg m−3 at the urban roadside, to 0.2 μg m−3 in the rural background, with suburban and urban background sites having average concentrations in the range of 1.0–2.4 μg m−3. Wind field analysis further highlighted the importance of road traffic as a source of black carbon and demonstrated the importance of local emission sources at the various receptor locations. Statistical analysis of data between sites generally indicated a weak correlation (rs = −0.03 to 0.68, COD = 0.32–0.91), further highlighting the importance of local emissions in determining ambient black carbon concentration. It was also found that black carbon comprised a significant portion of total ambient particulate matter (PM), particularly at sites with the larger traffic volumes and during rush-hour (e.g. ~45% of PM2.5 at Marylebone Road), however, its contribution to total PM was found to decrease on days of high pollution, indicating the importance of other PM components when air quality is particularly poor.

BLACK CARBON IN PM2.5 AT ROADSIDE SITE IN BANGKOK, THAILAND

Traffic is typically a major source of air pollution in urban areas of developing countries. The exhaust emissions include gaseous substances and particulate matter, which PM2.5 (particulate matter less than 2.5 micrometers in aerodynamic diameter) is the majority. In urban areas, the composition of PM2.5 at roadside site dominated by the carbonaceous combustion component, the major constituent wherein was represented as black carbon (BC). This study aimed to investigate the diurnal concentrations of BC related to PM2.5 by using a seven-wavelength aethalometer. Study site was located near one of congested roads in Bangkok, Thailand. The correlation between traffic volumes and BC concentrations at roadside were also discussed. Results showed that the 24-h average BC concentrations of this site were in the range of 1.5 – 15 µg/m3. The diurnal pattern of BC levels exhibited two peaks of BC concentrations occurring during 0500 to 0700 LST and 2100 to 2300 LST. The morning peak of BC evidently governed by traffic condition while the evening peak resulted from traffic associated with meteorological effect. In addition, the density of heavy-duty diesel vehicles (HDDVs) played an important role to the diurnal pattern of BC concentrations. Interestingly, the highest BC level from this study site was observed on Sunday, where the lowest was found on Monday and Friday. This involved with traffic volumes caused by particular activity around this study site.

The relationship between black carbon and polycyclic aromatic hydrocarbon exposures and mortality in Allegheny County, Pennsylvania

Black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) are components of fine particulate matter associated with adverse health outcomes. However, limited work has examined the effects of PM constituents on mortality risk. Our multiple regression analysis evaluated the association of estimated neighborhood-level average fine particulate matter (PM2.5), BC, and PAH concentrations for 2013 obtained from local-scale land use regression models with 2007–2011 census tract-level age-adjusted non-accidental, cardiovascular, pulmonary, cancer, and other mortality rates in Allegheny County, PA. Models were further adjusted for census tract-level race, education, and health insurance status. In our adjusted models, estimated pollutant concentrations were not consistently associated with mortality. Only one model’s effect estimate did not include the null value, although the relationship was opposite of our original hypothesis. An interquartile range (0.25 μg/m3) increase in BC concentration was associated with a 5.9% (95% CI − 11.07, − 0.36%) decrease in log-transformed cancer mortality. However, in all mortality categories, education and health insurance covariates had a robust association with outcomes. We did not find a consistent relationship between pollutant exposures and age-adjusted mortality rates in Allegheny County, PA. However, having health insurance and having greater than a high school diploma were associated with lower mortality risk.

Impact of the Emission Control of Diesel Vehicles on Black Carbon (BC) Concentrations over China

In order to reduce black carbon (BC) emissions from diesel vehicles, a regional atmospheric chemistry model (WRF-Chem) was used to investigate the effects of installing a high-efficiency device for vehicle exhaust control, a diesel particulate filter (DPF), on diesel vehicles in China. To reduce the uncertainty of estimation, three sensitivity experiments were designed and conducted for different emission scenarios. The first experiment uses the standard black carbon emissions of diesel vehicles without engaging in any emission control actions (referred to as CTRL), and the other two experiments were conducted using different DPF devices to reduce BC emissions by 65% (CASE1) and 39% (CASE2), respectively. The results show that the model simulation reasonably represents the measured BC concentrations. The highest BC concentrations occurred in large cities of the North China Plain (NCP) and present important seasonal variations. The results suggest that the reduction in diesel vehicle emissions has great benefits for reducing BC pollution not only in winter but also in other seasons. Sensitivity studies show that in CASE1, the average BC concentrations decreased about ~6% in January and by more than 10% in the other seasons. The greatest reduction exceeded 50%. In CASE2, the average BC concentrations decreased by about ~3.5% in January and by more than 7% in the other seasons. This study suggests that adding DPF to a diesel vehicle can have a significant influence on reducing BC concentrations in China. Thus, this study provides a practical basis by which diesel vehicle emissions can be reduced.

Long-Term Variation of Black Carbon Aerosol in China Based on Revised Aethalometer Monitoring Data

Black carbon (BC) aerosol, as a typical optical absorption aerosol, is of great significance to the study of climate and radiation. The China Atmosphere Watch Network (CAWNET), established by the China Meteorological Administration (CMA), contains 35 BC-monitored stations, which have been collecting data using commercial Aethalometer instruments (AEs) since 2006. Element carbon (EC) data measured from the thermal/optical reflectance (TOR) method was used to correct the BC monitoring data from the AEs, which are affected by various sampling and analytical artifacts. The average difference before and after the revision was about 17.3% (±11.5%). Furthermore, we analyzed the variations of BC in China from 2006 to 2017 using a revised dataset. The ten-year averaged concentration of BC would have been applicable for climate analysis, and can be a comparison sample in future research. The concentrations of BC across the stations in China showed a general downward trend, with occasional fluctuations, and the concentrations at urban sites decreased more significantly. The average concentrations of BC in urban sites are higher than rural and remote sites. The 10-year averaged concentration of BC ranges from 11.13 μg m−3 in Gucheng to 0.19 μg m−3 in Shangri-La, showing a strong spatial variation; the proportion of BC aerosol in PM2.5 is generally less than 20%. The BC showed obvious seasonal and diurnal variation; and the highest concentration occurred in winter, with more dramatic diurnal variation, followed by autumn and spring. There was a significant increase in concentration between local time 7:00–9:00 and 18:00–0:00. The distribution and trend of BC concentration in China showed a consistency with emissions of BC.

Black Carbon: The Concentration and Sources Study at the Nam Co Lake, the Tibetan Plateau from 2015 to 2016

We measured black carbon (BC) with a seven-wavelength aethalometer (AE-31) at the Nam Co Lake (NCL), the hinterland of the Tibetan Plateau (TP) from May 2015 to April 2016. The daily average concentration of BC was 145 ± 85 ng m−3, increasing by 50% since 2006. The seasonal variation of BC shows higher concentrations in spring and summer and lower concentrations in autumn and winter, dominated by the adjacent sources and meteorological conditions. The diurnal variation of BC showed that its concentrations peaked at 9:00–16:00 (UTC + 8), significantly related to local human activities (e.g., animal-manure burning and nearby traffic due to the tourism industry). The concentration-weighted trajectory (CWT) analysis showed that the long-distance transport of BC from South Asia could also be a potential contributor to BC at the NCL, as well as the biomass burning by the surrounding residents. The analyses of the absorption coefficient and absorption Ångström exponent show the consistency of sourcing the BC at the NCL. We suggest here that urgent measures should be taken to protect the atmospheric environment at the NCL, considering the fast-increasing concentrations of BC as an indicator of fuel combustion.