Total Black Carbon Research Articles

Pollution characteristics of black carbon based on MERRA-2 reanalysis data in core city of Central Plains Economic Zone, China: Historical trend and potential sources

Black carbon (BC) is one of the main factors in global climate change and human health. Based on reanalysis data from the Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2), the historical trends in the variation of BC and the factors affecting this were investigated in core city of Central Plains Economic Zone in China-Zhengzhou. Based on correlation analysis with ground measurements of BC concentration, it was determined that the MERRA-2 reanalysis data could be used to reveal the variations in ground-level BC concentrations. According to the variation trends of BC concentration in 1980–2020 and typical fossil fuel consumption in 2008–2017, two periods of rapidly increasing BC concentration were identified in 1980–1989 and 1999–2006. The increase in BC concentration then slowed from 2007. Since 2012, due to the adjustment of the Zhengzhou strategy and the implementation of an emission control strategy throughout Henan Province, the consumption of coal and coke decreased by 4% every year, resulting in a downward trend in the total BC emissions. However, coal and coke were still the main factors affecting the BC concentration in Zhengzhou. The contribution of transportation to BC in Zhengzhou has been particularly important since 2016. Analysis of BC seasonal variation revealed that the highest BC concentration was in winter, mainly due to the increase in industry and residential emissions. Additionally, based on the local and regional emission inventories and combined with potential source contribution function (PSCF), concentration weighted trajectory (CWT), this study revealed the potential sources regions and source types of BC in Zhengzhou, and found that the intensification of energy consumption and BC emissions in Zhengzhou and the surrounding regions of Henan Province might be the reasons for the high BC loading in Zhengzhou through regional transport.

Compensatory effect of biomass burning on black carbon concentrations during COVID-19 lockdown at a high-altitude station in SW India

The characteristics of black carbon (BC) aerosols, their sources, and their impact on atmospheric radiative forcing were extensively studied during the COVID-19 lockdown (28th March–31st May 2020) at a high-altitude rural site over the Western Ghats in southwest India. BC concentration and the contribution of BC originating from biomass burning (BCbb) estimated from the aethalometer model during the lockdown period were compared with the same periods in 2017 and 2018 and with the pre-lockdown period (1st February to March 20, 2020). BC concentrations were 44, 19, and 17% lower during the lockdown period compared with the pre-lockdown periods of 2020 and similar periods (28th March to 31st May) of 2017 and 2018, respectively. BCbb contributed ∼50% to total BC during the lockdown period of 2020 and compensated for the decrease in BC concentration due to lower traffic emissions. The characteristics of light-absorbing organic carbon (brown carbon; BrC) absorption at 370 nm were evaluated during the lockdown and the pre-lockdown periods of 2020, 2017, and 2018. The BrC was estimated to be the highest during the lockdown period of 2020. Finally, atmospheric radiative forcing was calculated using the mean BC concentration during the pre-lockdown, lockdown, and similar periods (28th March to 31st May) of 2017 and 2018.

Multi-type emission factors quantification of black carbon from agricultural machinery based on the whole tillage processes in China

Black carbon (BC), as one of the short-lived climate pollutants, is becoming more prominent contribution from non-road mobile source, especially for agricultural machinery (AM) in China. However, the understanding of BC emissions from AM is still not clear, and the BC emission factors (EFs) are also limited. In this study, we conducted real-world measurements on twenty AM to investigate the instantaneous BC emission characteristics and quantify BC EFs under the whole tillage processes. We find the instantaneous BC emissions and fuel consumptions are obvious differences and present good synchronization under different tillage processes. Multi-type (CO2-, fuel-, distance-, time-, and area-based) EFs of BC are developed, which are significantly affected by different tillage processes and emission standards of the used AM. While AM conducting rotary tillage, ploughing, harvest corn and harvest wheat on the same area of land, total BC emissions by using the China III emission standard AM will be reduced by 56%, 36%, 88%, and 87% than those by using China II emission standard AM, respectively. Furthermore, for corn and wheat production under the whole tillage processes, BC EFs are 16.90 (6.03–39.12) g/hm2 and 18.18 (5.91–38.69) g/hm2, CO2 EFs are 112.64 (72.07–195.98) g/hm2 and 103.72 (71.47–167.02) g/hm2, respectively. We estimate the BC and CO2 emissions from wheat and corn productions based on the average area-based EFs. The large fluctuation ranges of BC and CO2 emissions in different tillage processes and the whole processes can reflect that the use of AM in China is uneven. It also indicates that there is a large space for BC and CO2 emission reduction and optimization. Therefore, more attention should be paid to the control of BC and CO2 emissions from AM. We believe that the recommended multi-type EFs are applicable for the quantification of BC emissions from AM in China and other countries.

Transport of biomass burning products from Siberian wildfires into the Arctic

The study of the long-range transport of biomass burning products from Siberian wildfires into the Arctic atmosphere during the period of 2000-2019 is presented. An analysis of the characteristics of forest fires over the past 20 years revealed an increase in radiation power of an average Siberian wildfire, which is characterized by a statistically significant linear trend of 1.7 ± 1.0% / year. A joint analysis of fire activity in Siberian forests, as well as the contents of the black carbon (BC) and carbon monoxide (CO) contents in the Arctic atmosphere, indicates that extreme fire events force the development of regional anomalies in BC and CO. Correlation between the anomalies of BC (CO) over the Russian segment of the Arctic and the number of Siberian wildfires is found to be statistically significant at the α = 0.05 level and reach the value r = 0.77 (0.48) during the summer months. Using a linear regression model, an estimate of the sensitivity of changes in the total BC content and in the volume mixing ratio of CO at the 700-hPa level in the 1.910-8 kg⋅m-2 per 1000 fires and 0.4 ppbv per 1000 fires, respectively. The results of a detailed analysis of the long-range BC transport into the Arctic during catastrophic Siberian wildfires in the summer of 2019 are presented. It is shown that the considered episode was conditioned by the features of the large-scale atmospheric circulation characteristic for the atmospheric blocking event.

Daily personal exposure to black carbon in different microenvironments in Hanoi, Vietnam

Daily personal exposure to black carbon (BC) in different microenvironments in Hanoi, Vietnam was quantified for the first time. In this study, a portable instrument, microAethe® model AE51, was used to continuously measure BC concentrations in various microenvironments within buildings and transportation modes. Overall average daily personal exposure to BC from those microenvironments was 5.46 µg/h. The highest BC exposure was during commuting 13.48 µg/h and 5.74 µg/h for the motorcyclist and car driver, respectively. In building environments, the highest BC exposure was 3.98 µg/h in a coffee shop with smoking; the lowest BC exposure was 1.54 µg/h in a hospital department; while BC exposure in an office was 1.92 µg/h. The level of BC exposure in an apartment was strongly influenced by building ventilation modes. They were 3.58 µg/h and 2.15 µg/h with doors/windows open and closed, respectively. Our finding confirmed that commuting contributes disproportionately to the total BC exposure due to the high level of BC during traffic/travel. Building ventilation and air conditioning can significantly affect indoor BC levels and should be considered as a measure to reduce BC exposure within buildings in Hanoi.

Vertical Profiling of Fresh Biomass Burning Aerosol Optical Properties over the Greek Urban City of Ioannina, during the PANACEA Winter Campaign

Vertical profiling of aerosol particles was performed during the PANhellenic infrastructure for Atmospheric Composition and climatE chAnge (PANACEA) winter campaign (10 January 2020–7 February 2020) over the city of Ioannina, Greece (39.65° N, 20.85° E, 500 m a.s.l.). The middle-sized city of Ioannina suffers from wintertime air pollution episodes due to biomass burning (BB) domestic heating activities. The lidar technique was applied during the PANACEA winter campaign on Ioannina city, to fill the gap of knowledge of the spatio-temporal evolution of the vertical mixing of the particles occurring during these winter-time air pollution episodes. During this campaign the mobile single-wavelength (532 nm) depolarization Aerosol lIdAr System (AIAS) was used to measure the spatio-temporal evolution of the aerosols’ vertical profiles within the Planetary Boundary Layer (PBL) and the lower free troposphere (LFT; up to 4 km height a.s.l.). AIAS performed almost continuous lidar measurements from morning to late evening hours (typically from 07:00 to 19:00 UTC), under cloud-free conditions, to provide the vertical profiles of the aerosol backscatter coefficient (baer) and the particle linear depolarization ratio (PLDR), both at 532 nm. In this study we emphasized on the vertical profiling of very fresh (~hours) biomass burning (BB) particles originating from local domestic heating activities in the area. In total, 33 out of 34 aerosol layers in the lower free troposphere were characterized as fresh biomass burning ones of local origin, showing a mean particle linear depolarization value of 0.04 ± 0.02 with a range of 0.01 to 0.09 (532 nm) in a height region 1.21–2.23 km a.s.l. To corroborate our findings, we used in situ data, particulate matter (PM) concentrations (PM2.5) from a particulate sensor located close to our station, and the total black carbon (BC) concentrations along with the respective contribution of the fossil fuel (BCff) and biomass/wood burning (BCwb) from the Aethalometer. The PM2.5 mass concentrations ranged from 5.6 to 175.7 μg/m3, while the wood burning emissions from residential heating were increasing during the evening hours, with decreasing temperatures. The BCwb concentrations ranged from 0.5 to 17.5 μg/m3, with an extremely high mean contribution of BCwb equal to 85.4%, which in some cases during night-time reached up to 100% during the studied period.

Transport of black carbon from Central and West Asia to the Tibetan Plateau: Seasonality and climate effect

Black carbon (BC) exerts potential effect on climate, especially in the Tibetan Plateau (TP), where the cryosphere and environment are very sensitive to climate change. Although transport of atmospheric BC from South and East Asia to the TP has been comprehensively investigated, transport of BC from Central and West Asia (CWA) to the TP and its climate effect on the region have received little attention and are warrant investigation. Therefore, based on the observation and ERA-Interim reanalysis data, this study investigated transport of atmospheric BC from CWA to the TP, its seasonality and climate effect over the TP using WRF-Chem model. On an annual scale, BC from CWA contributes to 5.8% of total BC over the TP. Seasonally, the contribution rates were 5.1%, 5.9%, 6.2%, and 5.7% in spring, summer, autumn, and winter, respectively. The area-averaged surface radiative forcing over the TP induced by BC from CWA ranged from −0.14 to −0.04 W m−2, with the largest and smallest negative radiative forcing occurring in autumn and winter, respectively. Affected by BC from CWA, the area-averaged surface temperature over the TP increased by 0.033 °C in summer, whereas it decreased by 0.002, 0.005, and 0.001 °C in spring, autumn and winter, respectively. In the atmosphere over the TP, the positive radiative forcing with values of 0.17, 0.20, 0.04, and 0.07 W m−2 were induced by BC from CWA in spring, summer, autumn, and winter, respectively. At the top of the atmosphere over the TP, the calculated radiative forcing associated with BC from CWA were 0.08, 0.14, −0.1, and 0.03 W m−2 in spring, summer, autumn, and winter, respectively. On an annual scale, the radiative forcing in the atmosphere and at the top of the atmosphere over the TP caused by BC from CWA were 0.12 W m−2 and 0.04 W m−2, respectively. This study enriched the theoretical connotation of transboundary transport of BC aerosols to the TP.

Dual-carbon isotope constraints on source apportionment of black carbon in the megacity Guangzhou of the Pearl River Delta region, China for 2018 autumn season

Black carbon (BC) aerosol negatively affects air quality and contributes to climate warming globally. However, little is known about the relative contributions of different source control measures to BC reduction owing to the lack of powerful source-diagnostic tools. We combine the fingerprints of dual-carbon isotope using an optimized Bayesian Markov chain Monte Carlo (MCMC) scheme and for the first time to study the key sources of BC in megacity Guangzhou of the Pearl River Delta (PRD) region, China in 2018 autumn season. The MCMC model-derived source apportionment of BC shows that the dominant contributor is petroleum combustion (39%), followed by coal combustion (34%) and biomass burning (27%). It should be noted that the BC source pattern is highly sensitive to the variations of air masses transported with an enhanced contribution of fossil source from the eastern area, suggesting the important impact of regional atmospheric transportation on the BC source profile in the PRD region. Also, we further found that fossil fuel combustion BC contributed 84% to the total BC reduction during 2013–2018. The response of PM2.5 concentration to the 14C-derived BC source apportionment is successfully fitted (r = 0.90) and the results predicted that it would take ∼6 years to reach the WHO PM2.5 guideline value (10 μg m−3) for the PRD region if the emission control measures keep same as they are at present. Taken together, our findings suggest that dual-carbon isotope is a powerful tool in constraining the source apportionment of BC for the evaluations of air pollution control and carbon emission measures.

Disparities in driving forces behind energy-related black carbon emission changes across China's provinces

Black carbon (BC) is one of the most important factors affecting the uncertainty of global climate change, as well as affecting human health by absorbing harmful substances in the environment. Understanding how human activities drive BC emissions can help formulate effective emission reduction policies. However, regional differences in social and economic activities determine the factors driving BC emission change in different regions/provinces, leading to the non-applicability of national-level emission reduction policies among the provinces. Therefore, it is necessary to develop a provincial-level analysis to shape refined policies for BC emission reduction. Here, we subdivided China's total BC emissions into 30 provinces based on previous work and used the multi-regional input-output model and complete average decomposition analysis to explore how BC emission intensity, intermediate inputs structural adjustment, local final demand, inter-provincial trade, and international exports drive BC emissions during 2007–2017. The results showed that BC emission intensity was an important emission reduction factor for all provinces in China. As for the effect of intermediate inputs structural adjustment, it had a negative effect during 2007–2012. However, during 2012–2017, as the tertiary industry had become the biggest factor in promoting economic development, the impact of the intermediate input structure on BC emissions had become a positive contribution, which showed that current industrial structure adjustment was not conducive to BC emissions reduction. Local final demand, inter-provincial trade, and international exports were the main factors causing the increase in BC emissions in each province as well. Southwestern regions and heavy industrial provinces emitted additional high BC emissions due to the huge final demand in the Eastern coastal regions. More targeted policies can be formulated by determining BC emission reduction responsibilities based on their driving factors at the provincial and sectoral levels and the development of emission reduction measures for each province.

Source apportionment of black carbon using light absorption measurement and impact of biomass burning smoke on air quality over rural central Taiwan: A yearlong study

Biomass burning episodes are critical particulate matter (PM) issues in Taiwan. The occurrence patterns of biomass burning events through long-term PM monitoring are worth further exploration. This study monitored PM10, PM2.5, and black carbon (BC) over one year in central Taiwan. The source apportionment of BC was examined using light absorption techniques and divided into fossil fuel combustion (BCf) and biomass burning (BCb). The monitoring results showed that the annual average PM10, PM2.5, and BC mass concentrations were 45.4 μg/m3, 19.8 μg/m3, and 0.79 μg/m3, respectively, while the annual average ratio of BC/PM2.5 was 0.044. Furthermore, BCf was remarkably higher than BCb, accounting for 89% of the total BC mass. However, it was noticed that biomass burning smoke impacted the air quality by enhancing PM10, PM2.5, and BCb over monitoring location. There were 14.4% of hourly PM10 events (≥125 μg/m3) and 10.0% of hourly PM2.5 events (≥35 μg/m3) resulting from biomass burning episodes at this monitoring site in one-year observation. The hourly average PM10 and PM2.5 concentrations during these biomass burning episodes were 2.1 and 2.3 times higher than the annual average PM10 and PM2.5 concentrations. During severe biomass burning episodes, high levels of human carcinogens, such as 1, 3-butadiene, benzene, and isoprene were also observed. The results demonstrate that air quality is severely degraded during biomass burning episodes. Therefore, further research is required to understand the effects of biomass burning events on the residents' acute and chronic health conditions.

Black Carbon over Wuhan, China: Seasonal Variations in Its Optical Properties, Radiative Forcing and Contribution to Atmospheric Aerosols

As an important fraction of light-absorbing particles, black carbon (BC) has a significant warming effect, despite accounting for a small proportion of total aerosols. A comprehensive investigation was conducted on the characteristics of atmospheric aerosols and BC particles over Wuhan, China. Mass concentration, optical properties, and radiative forcing of total aerosols and BC were estimated using multi-source observation data. Results showed that the BC concentration monthly mean varied from 2.19 to 5.33 μg m−3. The BC aerosol optical depth (AOD) maximum monthly mean (0.026) occurred in winter, whereas the maximum total AOD (1.75) occurred in summer. Under polluted-air conditions, both aerosol radiative forcing (ARF) and BC radiative forcing (BCRF) at the bottom of the atmosphere (BOA) were strongest in summer, with values of −83.01 and −11.22 W m−2, respectively. In summer, ARF at BOA on polluted-air days was more than two-fold that on clean-air days. In addition, compared with clean-air days, BCRF at BOA on polluted-air days was increased by 76% and 73% in summer and winter, respectively. The results indicate an important influence of particulate air pollution on ARF and BCRF. Furthermore, the average contribution of BCRF to ARF was 13.8%, even though the proportion of BC in PM2.5 was only 5.1%.

Heavy metals and metalloids concentrations across UK urban horticultural soils and the factors influencing their bioavailability to food crops

Urban horticulture (UH) has been proposed as a solution to increase urban sustainability, but the potential risks to human health due to potentially elevated soil heavy metals and metalloids (HM) concentrations represent a major constraint for UH expansion. Here we provide the first UK-wide assessment of soil HM concentrations (total and bioavailable) in UH soils and the factors influencing their bioavailability to crops. Soils from 200 allotments across ten cities in the UK were collected and analysed for HM concentrations, black carbon (BC) and organic carbon (OC) concentrations, pH and texture. We found that although HM are widespread across UK UH soils, most concentrations fell below the respective UK soil screening values (C4SLs): 99 % Cr; 98 % As, Cd, Ni; 95 % Cu; 52 % Zn. However, 83 % of Pb concentrations exceeded C4SL, but only 3.5 % were above Pb national background concentration of 820 mg kg−1. The bioavailable HM concentrations represent a small fraction (0.01–1.8 %) of the total concentrations even for those soils that exceeded C4SLs. There was a significant positive relationship between both total and bioavailable HM and soil BC and OC concentrations. This suggest that while contributing to the accumulation of HM concentrations in UH soils, BC and OC may also provide a biding surface for the bioavailable HM concentrations contributing to their immobilisation. These findings have implications for both management of the risk to human health associated with UH growing in urban soils and with management of UH soil. There is a clear need to understand the mechanisms driving soil-to-crop HM transfer in UH to improve potentially restrictive C4SL (e.g. Pb) especially as public demand for UH land is growing. In addition, the UH community would benefit from education programs promoting soil management practices that reduce the risk of HM exposure - particularly in those plots where C4SLs were exceeded.

Improving emissions inputs via mobile measurements to estimate fine-scale Black Carbon monthly concentrations through geostatistical space-time data fusion

Isolating air pollution sources in a complex transportation environment to quantify their contribution is challenging, particularly with sparse stationary measurements. Mobile measurements can add finer spatial resolution to support source apportionment, but they exhibit limitations when characterizing long term concentrations. Dispersion models can help overcome these limitations. However, they are only as reliable as their input emissions inventories. Herein, we developed an innovative method to revise emissions through inverse modeling and improve dispersion modeling predictions using stationary/mobile measurements. One specific revision estimated an adjustment factor of ~306 for warehouse emissions, indicating a significant underestimation of our initial estimates. This revised emission rate scaled up nationally would correspond to ~3.5% of the total Black Carbon emissions in the U.S. Nevertheless, domain-specific revisions only contribute to a 4% increase of area source emissions while improving R2 from monthly estimates at fixed sites by 38%. After revising emissions through inverse dispersion modeling, we combine this model with stationary/mobile measurements through Bayesian Maximum Entropy (I-DISP BME) to produce temporally coarse yet spatially fine data fusion. We compare this novel data fusion approach to BME using only measurements (Flat BME). A 10-fold conventional cross-validation (representative of months with mobile measurements) shows that all BME methods have R2 values that range from 0.787 to 0.798. A 2-fold cross-validation (representative of months with no mobile measurements) shows that the R2 for I-DISP BME increases by a factor 90 when compared to Flat BME. Furthermore, not only is our novel I-DISP BME method more accurate than the classic Flat BME method, but the area it detects as highly exposed can be up to 5 times larger than that detected by the less accurate Flat BME method.

Temporal trends in the spatial-scale contributions to black carbon in a Middle Eastern megacity

The analysis of high-resolution changes in black carbon (BC) concentrations was examined to distinguish and quantify various spatial-scale contributions to BC concentrations from nearby sources within 1 km distance to ranges of emission sources distributed over a larger city scale spanning tens of kilometers. Our analysis illustrated that BC emissions on the neighborhood scale only contribute a minor fraction (~15%) to total BC concentrations in the megacity of Tehran. Approximately 62% of the total black carbon is part of the city emissions, and around 23% is transported into the city from local nearby surroundings. Our analysis in highly polluted areas, including industrial and traffic hotspots in Tehran, demonstrated that the contributions of the urban mixture were relatively smaller than the average (~56%) in highly polluted areas; however, larger local-scale (~30%) contributions were observed in these areas. Our analysis in traffic hotspot areas also demonstrated significantly smaller contributions of BC from neighborhood surroundings (~9%). These results imply that the city-scale BC emissions in Tehran are a major contributor to BC exposures even in locations with local high-emitting sources. Polar annulus analysis of BC from city-scales in Tehran showed a mixture of hotspot locations ranging from north to easterly directions implying that city-scale emissions contribute to wider pollution plume expansions and larger-scale transport and vertical mixing corresponding to mixtures of emitters located further away.

Prenatal exposure to residential PM2.5 and its chemical constituents and weight in preschool children: A longitudinal study from Shanghai, China

BackgroundStudies have reported that prenatal exposure to fine particulate matter (PM2.5) might be associated with adverse birth outcomes in offspring. However, evidence with regard to the effects of prenatal exposure to PM2.5 and, especially, its main chemical constituents on offspring’s weight in childhood is limited and inconsistent. ObjectivesThe present study aimed to examine associations of prenatal exposure to PM2.5 total mass and its chemical constituents in each trimester with children’s weight from birth to 6 years of age using data from Shanghai-Minhang Birth Cohort Study. MethodsA total of 1,084 mother-infant pairs were included with both PM2.5 exposure data and at least one measurement of weight and height. Weight-for-Length (WLZ), BMI-for-Age (BMIz), and Weight-for-Age (WAZ) z-scores were generated according to the World Health Organization guidelines. Exposure to PM2.5 total mass and its chemical constituents [organic carbon (OC), black carbon (BC), ammonium (NH4+), nitrate (NO3−), sulfate (SO42−), and soil dust (SOIL)] during pregnancy was estimated from a satellite based modelling framework. We used multiple informant model to estimate the associations of trimester-specific PM2.5 total mass and its specific constituents concentrations with WLZ/BMIz and WAZ of offspring at birth and 1, 4, and 6 years of age. ResultsIn multiple informant model, we observed consistent patterns of associations between exposure to PM2.5 total mass, OC, BC, NH4+, NO3−, and SO42− during the 2nd and 3rd trimesters and decreased WLZ/BMIz and WAZ at 1, 4, and 6 years of age in boys. We observed associations between prenatal exposure to PM2.5 total mass, NH4+, and NO3− during the 1st and 2nd trimesters and increased WLZ/BMIz and WAZ in girls at birth. However, there were null associations at 1 and 4 years of age and inverse associations at 6 years of age. ConclusionsPrenatal exposure to PM2.5 total mass and its main chemical constituents was associated with decreased weight in boys from 1 to 6 years of age, with increased weight at birth and decreased weight at 6 years of age in girls. Our findings suggest that prenatal exposure to PM2.5 and its chemical constituents may have a lasting effect on offspring’s weight in childhood.

Characterising professional drivers’ exposure to traffic-related air pollution: Evidence for reduction strategies from in-vehicle personal exposure monitoring

Professional drivers working in congested urban areas are required to work near harmful traffic related pollutants for extended periods, representing a significant, but understudied occupational risk. This study collected personal black carbon (BC) exposures for 141 drivers across seven sectors in London. The aim of the study was to assess the magnitude and the primary determinants of their exposure, leading to the formulation of targeted exposure reduction strategies for the occupation. Each participant’s personal BC exposures were continuously measured using real-time monitors for 96 h, incorporating four shifts per participant. ‘At work’ BC exposures (3.1 ± 3.5 µg/m3) were 2.6 times higher compared to when ‘not at work’ (1.2 ± 0.7 µg/m3). Workers spent 19% of their time ‘at work driving’, however this activity contributed 36% of total BC exposure, highlighting the disproportionate effect driving had on their daily exposure. Taxi drivers experienced the highest BC exposures due to the time they spent working in congested central London, while emergency services had the lowest. Spikes in exposure were observed while driving and were at times greater than 100 µg/m3. The most significant determinants of drivers’ exposures were driving in tunnels, congestion, location, day of week and time of shift. Driving with closed windows significantly reduced exposures and is a simple behaviour change drivers could implement. Our results highlight strategies by which employers and local policy makers can reduce professional drivers’ exposure to traffic-related air pollution.

Quantification and implication of measurement bias of ambient atmospheric BC concentration

Black carbon (BC) aerosols have severe impacts on climate and health. Most atmospheric BC loadings are now predominantly reported for the PM2.5 size cut-off. Based on 39 published set of ambient BC concentrations from around the world where PM2.5 and PM10 were collected in parallel, we demonstrate that BC in PM2.5 was only around 80% of that in PM10. The implication is that around 20% of BC in the global ambient atmosphere is ignored with the now-legacy PM2.5 sampling approach. Correspondingly, BC of freshly emitted particles from combustion activities is dominantly reported in terms of PM2.5, and thus inflicting a bias in the total BC emission inventories. A consequence is that ambient BC is underpredicted when derived from models based on (PM2.5) emission inventories. This consideration contributes to reconcile existing systematic offset between model predictions and observation-based estimates of climate-relevant effects of anthropogenic BC aerosols. We propose that total ambient BC concentration should be considered rather than the PM2.5 portion to reduce the uncertainties in estimates of BC effects on the climate.

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.

Measurement report: Source and mixing state of black carbon aerosol in the North China Plain: implications for radiative effect

Abstract. Establishment of the sources and mixing state of black carbon (BC) aerosol is essential for assessing its impact on air quality and climatic effects. A winter campaign (December 2017–January 2018) was performed in the North China Plain (NCP) to evaluate the sources, coating composition, and radiative effects of BC under the background of emission reduction. Results showed that the sources of liquid fossil fuels (i.e., traffic emissions) and solid fuels (i.e., biomass and coal burning) contributed 69 % and 31 % to the total equivalent BC (eBC) mass, respectively. These values were arrived at by using a combination of multi-wavelength optical approach with the source-based aerosol absorption Ångström exponent values. The air quality model indicated that local emissions were the dominant contributors to BC at the measurement site. However, regional emissions from NCP were a critical factor for high BC pollution. A single-particle aerosol mass spectrometer identified six classes of elemental carbon (EC)-containing particles. They included EC coated by organic carbon and sulfate (52 % of total EC-containing particles); EC coated by Na and K (24 %); EC coated by K, sulfate, and nitrate (17 %); EC associated with biomass burning (6 %); pure-EC (1 %); and others (1 %). Different BC sources exhibited distinct impacts on the EC-containing particles. A radiative transfer model showed that the amount of detected eBC can produce an atmospheric direct radiative effect of +18.0 W m−2 and a heating rate of 0.5 K d−1. This study shows that reductions of solid fuel combustion-related BC may be an effective way of mitigating regional warming in the NCP.

Fingerprinting characterization of sedimentary PAHs and black carbon in the East China Sea using carbon and hydrogen isotopes

In this study, we present the application of a dual-isotope approach for the source apportionment of polycyclic aromatic hydrocarbons (PAHs) and black carbon (BC) in the East China Sea (ECS). The δ13C and δ2H isotope signatures of the PAHs were determined from surface sediments collected from the ECS. A Bayesian Markov chain Monte Carlo (MCMC) model was used to the environmental source identifications with dual-isotope PAHs data. The results indicate that the coal combustion source is predominant (with average of 41%) in the ECS. Liquid fossil fuels combustion, biomass combustion, and petrogenic sources account for 23%, 20%, and 12% of the total PAH burden, respectively. Additionally, we also determine the stable and radio carbon isotopes (δ13C and Δ14C) of total BC in sediment samples of the ECS. The results demonstrate the quantitative source apportionments for different sources, reflecting the contributions of fossil fuels (coal combustion and petroleum-related emissions), biomass (C3 and C4 plants) combustion, and rock-weathering sources. The fossil combustion in BC accounts for 67%, with 23% for biomass sources, meanwhile the rock weathering source in BC is an average of 10%. These results show a remarkable similarity and extensive homologies at source apportionment of PAHs and BC in the ECS, even though some differences in source mechanisms and processes. These findings on the environmental source apportionment will provide a reference for improved emission inventories, and will help to provide guidance for the efforts to mitigate environmental pollution in the coastal areas and marginal sea.