Black carbon in Xiamen, China: Temporal variations, transport pathways and impacts of synoptic circulation

Traces of black carbon sources before and after the Covid-19 outbreak in Tehran, Iran

The concentration of black carbon was measured in four sites of the industrial and high-traffic metropolis of Tehran with different land uses. Then, the contribution of biomass and fossil fuels in the emission of this pollutant was modeled using the Aethalometer model. The possible locations of important sources of black carbon dissemination were projected using PSCF and CWT models, and the results were compared in the two periods before and after the Covid-19 outbreak. Temporal variations of black carbon illustrated that BC concentration decreased in the period after the onset of the pandemic in all studied areas, and this decline was more explicit in the traffic intersection of the city. Diurnal changes of BC concentration indicated the significant impact of the application of the law banning night traffic of motor vehicles in reducing the BC concentration in this period, and probably the reduction of HDDV traffic has played the most important role in this reduction. The results related to the share of BC sources indicated that black carbon emissions are affected by an average of about 80% of fossil fuel combustion and wood combustion interferes with about 20% of BC emissions. Finally, speculations were made about the possible sources of BC emission and its urban scale transport using PSCF and CWT models, which indicated the superiority of the CWT model in terms of source segregation. The results of this analysis were further utilized to surmise black carbon emission sources based on the land use of receptor points.

Impacts of synoptic circulation on surface ozone pollution in a coastal eco-city in Southeastern China during 2014-2019

The coastal eco-city of Fuzhou in Southeastern China has experienced severe ozone (O₃) episodes at times in recent years. In this study, three typical synoptic circulations types (CTs) that influenced more than 80% of O₃ polluted days in Fuzhou during 2014-2019 were identified using a subjective approach. The characteristics of meteorological conditions linked to photochemical formation and transport of O₃ under the three CTs were summarized. Comprehensive Air Quality Model with extensions was applied to simulate O₃ episodes and to quantify O₃ sources from different regions in Fuzhou. When Fuzhou was located to the west of a high-pressure system (classified as "East-ridge"), more warm southwesterly currents flowed to Fuzhou, and the effects of cross-regional transport from Guangdong province and high local production promoted the occurrence of O₃ episodes. Under a uniform pressure field with a low-pressure system occurring to the east of Fuzhou (defined as "East-low"), stagnant weather conditions caused the strongest local production of O₃ in the atmospheric boundary layer. Controlled by high-pressure systems over the mainland (categorized as "Inland-high"), northerly airflows enhanced the contribution of cross-regional transport to O₃ in Fuzhou. The abnormal increases of the "East-ridge" and "Inland-high" were closely related to O₃ pollution in Fuzhou in April and May 2018, resulting in the annual maximum number of O₃ polluted days during recent years. Furthermore, the rising number of autumn O₃ episodes in 2017-2019 was mainly related to the "Inland-high", indicating the aggravation of cross-regional transport and highlighting the necessity of enhanced regional collaboration and efforts in combating O₃ pollution.

Health threat of PM2.5-bound trace elements exposure on asthma hospital admission: A time-stratified case-crossover study

Environmental pollution of trace elements has become of main concern due to the adverse effects. To estimate the impact of PM_2.5-bound trace elements on human health, a time-stratified case-crossover study has been designed to examine the short-term associations between 28 elements and asthma hospitalizations from January 2019 to November 2021 in Xiamen, China. This research summarized the major components that pose health risks in different seasons and took risk assessment for different groups. We found that an inter-quartile range (IQR) increase of Ca, Fe, Mn, Pd, Si, and Ti was positively associated with the incidence of asthma in the lag of 0-4 days. In winter, the elements that predisposed the population to asthma attack were the most, such as Al, Ba, Ca, Cr, Cu, Fe, K, Mn, Pd, Si, and Ti, and these elements are at higher risk for longer periods of time. The discrepancy in risk levels and major elements of asthma diagnosis among various age groups were also found in this work. Our results provided insights into the development of specific policies to reduce the risk of asthma attacks due to exposure to PM_2.5-bound trace elements.

Characteristics, source apportionment and long-range transport of black carbon at a high-altitude urban centre in the Kashmir valley, North-western Himalaya

Six years of data (2012-2017) at an urban site-Srinagar in the Northwest Himalaya were used to investigate temporal variability, meteorological influences, source apportionment and potential source regions of BC. The daily BC concentration varies from 0.56 to 40.16 μg/m³ with an inter-annual variation of 4.20-7.04 μg/m³ and is higher than majority of the Himalayan urban locations. High mean annual BC concentration (6.06 μg/m³) is attributed to the high BC observations during winter (8.60 μg/m³) and autumn (8.31 μg/m³) with a major contribution from Nov (13.88 μg/m³) to Dec (13.4 μg/m³). A considerable inter-month and inter-seasonal BC variability was observed owing to the large changes in synoptic meteorology. Low BC concentrations were observed in spring and summer (3.14 μg/m³ and 3.21 μg/m³), corresponding to high minimum temperatures (6.6 °C and 15.7 °C), wind speed (2.4 and 1.6 m/s), ventilation coefficient (2262 and 2616 m²/s), precipitation (316.7 mm and 173.3 mm) and low relative humidity (68% and 62%). However, during late autumn and winter, frequent temperature inversions, shallow PBL (173-1042 m), stagnant and dry weather conditions cause BC to accumulate in the valley. Through the observation period, two predominant diurnal BC peaks were observed at ⁓9:00 h (7.75 μg/m³) and ⁓21:00 h (6.67 μg/m³). Morning peak concentration in autumn (11.28 μg/m³) is ⁓2-2.5 times greater than spring (4.32 μg/m³) and summer (5.23 μg/m³), owing to the emission source peaks and diurnal boundary layer height. Diurnal BC concentration during autumn and winter is 65% and 60% higher than spring and summer respectively. During autumn and winter, biomass burning contributes approximately 50% of the BC concentration compared to only 10% during the summer. Air masses transport considerable BC from the Middle East and northern portions of South Asia, especially the Indo-Gangetic Plains, to Srinagar, with serious consequences for climate, human health, and the environment.

Characteristics of fine carbonaceous aerosols in Wuhai, a resource-based city in Northern China:Insights from energy efficiency and population density

As one of the predominant compositions of PM_2.5 (particulate matter with aerodynamic diameter ≤2.5 μm), carbonaceous aerosols not only have adverse effects on air quality, but also can affect climate change. Although there are extensive recent studies on carbonaceous aerosols, comprehensive studies on their socioeconomic influencing factors in a resource-based city are relatively limited. In this study, the spatial-temporal variations of organic carbon (OC), elemental carbon (EC), and secondary organic carbon (SOC) were investigated in January, July, and October in 2015 and April in 2016 in Wuhai and its surrounding areas. The population distribution and industry layout have led to the uneven spatial-temporal distribution of carbonaceous aerosols. The concentrations of carbonaceous aerosols were higher in winter due to the unfavorable meteorology and the increased emissions from heating. The SOC is a significant contributor to OC in the cold season (52.0% for January). Primary carbonaceous aerosols pollution is higher in the industrial sites of resource-based cities, whereas the SOC makes a significant contribution in the residential sites. The results of backward-trajectory and concentration-weighted trajectory analysis suggest that the local emissions and short-range atmospheric transport from nearby areas have a significant impact on PM_2.5 and carbonaceous aerosols. A strong correlation between population density and OC/EC ratio was found, indicating that the megacities with high population density have a higher SOC contribution than the resource-based cities. Resource-based cities are characterized by high level of primary OC emissions, whereas cities with high energy efficiency have a more significant SOC contribution. These results provide a more comprehensive understanding of carbonaceous aerosols in a resource-based city.

Atmospheric black carbon in urban and traffic areas in Shanghai: Temporal variations, source characteristics, and population exposure

Black carbon (BC) measurements were performed at Pudong (PD) urban supersite and Gonghexin (GH) roadside station from December 1, 2017 to August 10, 2020 to investigate the variations, source characteristics, and population exposure levels of BC in traffic and urban areas in Shanghai, China. The BC median concentration at GH was more than two-fold that at PD. Absorption Ångström exponent (AAE) values were 1.27 ± 0.17 and 1.31 ± 0.17 at PD and GH, respectively, suggesting the dominance of liquid fossil fuel combustion sources (i.e., traffic exhaust) at these stations. The higher BC and AAE values in winter at PD indicated the relatively increasing contribution of solid fuels (i.e., biomass burning) to BC concentration in urban Shanghai. The diurnal variation in BC showed similar twin-peak patterns at PD and GH, implying that traffic emission mainly contributed to ambient BC concentration in urban Shanghai. The estimated daily intakes (EDIs) of BC were generally higher in males than in females at both PD and GH. The highest BC EDIs at PD were found in age subgroups 1-<2 and 2-<3 years. In contrast, the BC EDIs at GH were observed in age subgroups 6-<9, 12-<15, and 15-<18 years, which were higher than those determined at PD, indicating that more attention must be paid to BC exposure of the population in these age subgroups. These results provide scientific insights into variations, source characteristics, and population exposure levels of BC in urban and traffic areas and could help in the development of BC control strategies in Shanghai.

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%.

Hydrogen Technology towards the Solution of Environment-Friendly New Energy Vehicles

The popularity of climate neutral new energy vehicles for reduced emissions and improved air quality has been raising great attention for many years. World-wide, a strong commitment continues to drive the demand for zero-emission through alternative energy sources and propulsion systems. Despite the fact that 71.27% of hydrogen is produced from natural gas, green hydrogen is a promising clean way to contribute to and maintain a climate neutral ecosystem. Thereby, reaching CO2 targets for 2030 and beyond requires cross-sectoral changes. However, the strong motivation of governments for climate neutrality is challenging many sectors. One of them is the transport sector, as it is challenged to find viable all-in solutions that satisfy social, economic, and sustainable requirements. Currently, the use of new energy vehicles operating on green sustainable hydrogen technologies, such as batteries or fuel cells, has been the focus for reducing the mobility induced emissions. In Europe, 50% of the total emissions result from mobility. The following article reviews the background, ongoing challenges and potentials of new energy vehicles towards the development of an environmentally friendly hydrogen economy. A change management process mindset has been adapted to discuss the key scientific and commercial challenges for a successful transition.

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.

A novel way to calculate shortwave black carbon direct radiative effect

Black carbon (BC) aerosol has a strong radiative forcing effect and significantly affects human beings and the environment. Therefore, it is important to quantitatively calculate its direct radiative effect (BC DRE) at the surface (SFC) and the top of the atmosphere (TOA). Current studies mainly use empirical formula methods or broadband methods to calculate BC DRE. However, these two methods do not consider the differences of sky diffuse light ratios in different wavelength bands. To overcome this problem, a new scheme named the multiband synthetic method is proposed to calculate blue sky albedo at MODIS narrow bands, and then, the blue sky albedo at the whole shortwave band is synthesized with these separate narrowband blue sky albedos. Based on BC concentration measured in Xuzhou over two years (from May 2014 to July 2016), aerosol optical depth (AOD) and microphysical parameters provided by AERONET, and the black sky albedo (BSA) and white sky albedo (WSA) provided by Google Earth Engine (GEE) products, shortwave BC DRE was calculated numerically with the use of the 6S radiative transfer model. The range of BC DRE computed by the multiband synthetic method at the TOA and SFC are 0.84 ± 0.08 to 3.27 ± 1.01W/m² and -14.57 ± 4.53 to -4.31 ± 0.36W/m². The shortwave BC DRE calculated by the multiband synthetic method was higher than that calculated with the broadband method and empirical formula method by 0.11% to 0.36% (at the SFC), 0.14% to 1.4% (at the SFC) and 3.4% to 10.1% (at the TOA), 5.5% to 15.8% (at the TOA), respectively. The BC DREs calculated by these three methods have small differences at the SFC. However, the difference was large at the TOA. The results of this study suggest that it is important to consider the differences between different narrow bands when calculating the broadband shortwave blue sky albedo.

Chemical composition and sources of submicron aerosol in a coastal city of China: Results from the 2017 BRICS summit study

Chemical compositions of non-refractory submicron aerosol (NR-PM₁) were measured via an Aerodyne Aerosol Chemical Speciation Monitor at the coastal city Xiamen during the 2017 BRICS summit from August 10 to September 10. Mean hourly concentration of NR-PM₁ was 13.55 ± 8.83 μg m^-3 during the study period, decreasing from 18.83 μg m^-3 before-BRICS to 13.02 μg m^-3 in BRCIS I and 8.42 μg m^-3 in BRICS II. Positive matrix factor analyses resolved four organic aerosols (OA): a hydrocarbon-like OA (HOA, 14.78%), a cooking-related OA (COA, 28.21%), a biomass burning OA (BBOA, 18.00%), and an oxygenated OA (OOA, 39.22%). The contributions of local pollutants like nitrate and HOA reduced, while the proportions of sulfate and OOA increased during the control episodes. The diurnal patterns of NR-PM₁ species and OA components in each episode were characterized. The results showed that BC, nitrate, COA, and HOA had peaks in the morning and evening, which became less obvious under the emission control. Moreover, the diurnal variations of all species in Ep 3 with emission control were much flatter due to the effect of transport. Backward trajectories analysis confirmed the long-range transport of air masses from the continent, which resulted in the high proportions of sulfate (43.69%) and OOA (50.28%) in Ep 3. Our study implies the significant effect of emission control on reducing primary pollutants, but the formation of particles during the long-range transport need to be paid more attention when set the air quality control strategies in coastal cities.