Characterization of black carbon in an urban-rural fringe area of Beijing

Characteristics and source apportionment of black carbon the urban and desert underlying surfaces

The spatial distribution of black carbon (BC) concentrations was highly variable across different underlying surfaces. Differences in meteorological conditions and emission sources led to great temporal and spatial variations in BC characteristics. As the most important absorbing aerosol, BC can affect radiation, clouds, and surface snow. BC mass concentrations were measured using a seven channel aethalometer (AE-33) in the Urumqi and Taklimakan Deserts from January to December 2022. The aethalometer data, potential source contribution function (PSCF), and concentration-weighted trajectory (CWT) models were used to analyse the variation characteristics, potential sources, and affected areas. Results showed that the BC concentrations in the Taklamakan Desert and Urumqi were in the range of 0-500 ng·m-3, accounting for 66.20 % and 59.50 % of the total, respectively. The backward trajectory simulation of BC mass concentration in the tower and Urumqi using the HYSPLIT model found that the airflow trajectories in the tower in summer corresponded to the BC concentration in the following order: trajectory 4 > trajectory 3 > trajectory 2 > trajectory 1, and trajectory 4 originated from the Turpan airflow accounting for 46.19 % of the total, which corresponded to the highest BC concentration of 621.73 ng·m-3. The trajectories of the airflow in Urumqi in summer corresponded to the BC concentration in the order of high to low, and the BC concentration in summer corresponded to the highest concentration in the Turpan airflow. BC concentrations arranged from high to low were trajectory 1 > trajectory 5 > trajectory 3 > trajectory 4 > trajectory 2. Trajectories 3, 4, and 5 airflow directions were the same, and the airflow trajectory accounted for 47.48 %, corresponding to BC concentrations of 599.82 ng·m-3, 579.99 ng·m-3, and 555.85 ng·m-3, respectively. Tower in the spring compared with other seasons of the CWT value of >400 ng·m-3 had the widest coverage, and Urumqi had more source areas contributing to moderate pollution concentration weights in winter (400 ng·m-3 < CWT < 800 ng·m-3). The conclusions of this study provide a scientific basis for regional environmental management and the formulation of air pollution measures in Xinjiang.

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

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

Effects of black carbon aerosol on air quality and vertical meteorological factors in early summer in Beijing

Black carbon (BC) aerosols have effects on the atmospheric thermal vertical structure due to its radiation absorption characteristics, hereby influencing the boundary layer characteristics and pollutant diffusion. This study focuses on the BC effects under different atmospheric conditions on air quality and vertical meteorological conditions. Four days flight observation combined with surface wind profiler radar data were used to investigate the vertical profiles of BC and wind speed over Beijing urban area in early summer. The vertical profiles of BC concentration and wind speed in the boundary layer had a negative correlation, both having abrupt changes near the boundary layer height under stagnant weather conditions. The chemical transport model showed the increase of BC under stagnant conditions could cause aggravation of the stability of the boundary layer, thereby increasing the accumulation of pollutants. In particular, BC leads to the changes in the temperature profile, which will modify relative humidity and indirectly lead to the changes in the vertical profile of aerosol optical properties. However, if the early accumulation of BC was absent under more turbulent conditions, the effects of BC on air quality and meteorological conditions were limited.

Near-surface wind profile test based on accuracy verification of UAV anemometer lifting height in an urban fringe built-up area

Multirotor UAVs (unmanned aerial vehicles) have been widely used in urban vertical wind environment testing, whereas less attention has been given to the accuracy of wind speed captured by anemometers as drones fly. This paper aims to identify the ideal location of the anemometer on the UAV to obtain more accurate wind speeds and to assess the variation characteristics of wind speed in different spatial types in urban fringe areas. Accuracy verification of the lifting height of the anemometer in the UAV and wind profile test was carried out at three locations (a tennis court, a residential area, and a green park) on the iHarbour campus of Xi'an Jiaotong University. The following results were obtained: (1) the background wind speed was captured more accurately (R = 0.727, P = 0.001) when the lifting height of the anemometer was 0.00 m (as the height of the anemometer was the same as the rotors) and when the multirotor UAV was hovering in the air. However, this optimal lifting height lost 29.6% of the accuracy for capturing the background wind speed. Interestingly, when the lifting height was 0.75 m, the anemometer captured by the anemometer on the drone showed a significant negative correlation (R =  - 0.682, P = 0.005) with the background wind speed. (2) The wind speed at an altitude of 1.5 m in the residential area was significantly lower than that noted at other heights, and the wind speed at 24 m was significantly lower than that at 100 m. (3) In addition, a sudden increase in wind speeds was always observed near the surface of 12 m inside the campus, which may be due to the interaction of hot surface air in this newly built-up area with the cool rural winds around it. The study presents methods and quantitative references for the application of multirotor UAVs in urban vertical wind environment testing and the evaluation of ventilation performance at different heights inside high-rise houses in urban fringe areas.

Vertical profiling of black carbon and ozone using a multicopter unmanned aerial vehicle (UAV) in urban Shenzhen of South China

Existing studies on vertical profiling of black carbon (BC) and ozone (O₃) were mainly conducted in the rural areas, leading to limited knowledge of their vertical distributions in the urban area. To fill this knowledge gap, vertical profiling (0-500 m and 0-900 m, AGL) of BC and O₃ was conducted in a highly urbanized area of Shenzhen in subtropical South China using a multicopter unmanned aerial vehicle (UAV) platform. In total 32 flights were conducted from the 10th to 15th, December 2017 (winter campaign) and 42 flights from the 19th to 28th, August 2018 (summer campaign) with 4 time slots per day, including morning, afternoon, evening, and midnight. In general, equivalent BC (eBC) concentration decreased as the height increased with an overall slope of -0.13 μg m^-3 per 100 m in the winter campaign and -0.08 μg m^-3 per 100 m in the summer campaign. On the contrary, an increase of O₃ level with altitude was observed (7.8 ppb per 100 m). Absorption Ångström exponent (AAE) exhibits a slightly increasing trend with height. Seasonality of eBC vertical profiles was observed in morning, afternoon and midnight flights, but not for evening flights. The analysis showed the shape of vertical profiles of eBC and O₃ can be affected by planetary boundary layer height (PBLH) and air mass origin. Calculated heating rates due to BC show distinct seasonal variability for morning but not for afternoon, because of the counteracting effects by solar irradiance in the subtropical afternoon and eBC concentration in urban South China influenced by the monsoon climate.

A multiple linear regression model with multiplicative log-normal error term for atmospheric concentration data

The homoscedasticity assumption (the variance of the error term is the same across all the observations) is a key assumption in the ordinary linear squares (OLS) solution of a linear regression model. The validity of this assumption is examined for a multiple linear regression model used to determine the source contributions to the observed black carbon concentrations at 12 background monitoring sites across China using a hybrid modeling approach. Residual analysis from the traditional OLS method, which assumes that the error term is additive and normally distributed with a mean of zero, shows pronounced heteroscedasticity based on the Breusch-Pagan test for 11 datasets. Noticing that the atmospheric black carbon data are log-normally distributed, we make a new assumption that the error terms are multiplicative and log-normally distributed. When the coefficients of the multilinear regression model are determined using the maximum likelihood estimation (MLE), the distribution of the residuals in 8 out of the 12 datasets is in good accordance with the revised assumption. Furthermore, the MLE computation under this novel assumption could be proved mathematically identical to minimizing a log-scale objective function, which considerably reduces the complexity in the MLE calculation. The new method is further demonstrated to have clear advantages in numerical simulation experiments of a 5-variable multiple linear regression model using synthesized data with prescribed coefficients and lognormally distributed multiplicative errors. Under all 9 simulation scenarios, the new method yields the most accurate estimations of the regression coefficients and has significantly higher coverage probability (on average, 95% for all five coefficients) than OLS (79%) and weighted least squares (WLS, 72%) methods.

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.

Preliminary study of black carbon content in airborne particulate matters from an open site in the city of Yaoundé, Cameroon

A light absorbing reflectometer was used to calculate black carbon (BC) mass concentrations contained in both fine and coarse particulate matters (PM_2.5 and PM_2.5-10) collected in an urban area of Yaoundé from 1st March 2018 to 26th February 2019 to highlight BC fluctuation and determine its potential predominant sources. The highest BC concentrations were obtained on 14/02/2019 (5.37 µg/m³) and 17/01/2019 (3.90 µg/m³) whereas the cleanest days were 28/06/2018 (0.01 µg/m³) and 30/06/2018 (0.21 µg/m³) for BC content of PM_2.5 and PM_2.5-10, respectively. While BC values for BC_2.5-10 were only obtained from November 2018 to February 2019 and in the long dry season, those of BC_2.5 were obtained for all the seasons. Months, which were most polluted with BC, were January with an average value of 2.34 ± 1.71 µg/m³ and December with 1.65 ± 0.82 µg/m³ whilst the least polluted were September with 0.54 ± 0.33 µg/m³ and August with 0.21 ± 0.10 µg/m³ for BC_2.5 and BC_2.5-10, respectively. The BC_2.5 and BC_2.5-10 annual average values were 1.18 ± 0.98 µg/m³ and 0.66 ± 0.39 µg/m³. The annual mean BC contributions were 8.27 ± 5.00% and 6.63 ± 4.49%, respectively, in PM_2.5 and PM_2.5-10. The BC_2.5/PM_2.5 percentages varied widely; thus, a complete identification of potential sources of BC was very complex. However, by analogy with other studies, predominant sources were agricultural burn, light-duty gasoline, household wood and charcoal burning sources.

Simulated aging processes of black carbon and its impact during a severe winter haze event in the Beijing-Tianjin-Hebei region

Black carbon (BC) can mitigate or worsen air pollution by perturbing meteorological conditions. BC aging processes strongly influence the evolution of the particle size, concentration, and optical properties of BC, which determine its influence on meteorology. Here, we use the online coupled Weather Research and Forecasting-Chemistry (WRF-Chem) model to quantify the role of BC aging processes, including physical processes (PP) and absorption enhancement (AE), in causing BC-induced meteorological changes and their associated feedbacks to PM_2.5 (particulate matter less than 2.5 μm in diameter) and O₃ concentrations during a severe haze event in the Beijing-Tianjin-Hebei (BTH) region during 21-27 February 2014. Our results show that, compared to those from the simulation without PP, the simulated near-surface BC concentration and BC mass loading in the BTH region decreased by 6.6% and 12.1%, respectively, when PP were included. PP increased the proportion of large BC (particle diameter greater than 0.312 μm) below 1000 m from 28 to 33% to 59-64% in the BTH region. When both PP and AE were included in the simulation, the reduction in PBL height due to the BC-PBL interaction was 116.3 m (20.7%), compared to reductions of 75.7 m (13.5%) without AE and 66.6 m (11.9%) without PP and AE. However, during this haze event, anomalous northeasterly winds were produced by the direct radiative effect of BC, which further affected aerosol mixing and transport. Due to their combined impacts on multiple meteorological factors, the direct radiative effects of BC without PP and AE, without AE, and with PP and AE increased the surface concentrations of PM_2.5 by 8.3 μg m^-3 (by 6.1% relative to the mean value), 6.1 μg m^-3 (4.5%) and 9.6 μg m^-3 (7.0%), respectively, but decreased the surface O₃ concentrations by 2.8 ppbv (7.4%), 4.0 ppbv (9.0%) and 5.0 ppbv (10.8%) on average in the BTH region during 21-27 February 2014.

Source Apportionment of Ambient Black Carbon During the COVID-19 Lockdown

Black carbon (BC) particles being emitted from mobile and stationary emission sources as a result of combustion activities have significant impacts on human health and climate change. A lot of social activities have been halted during the COVID-19 lockdowns, which has evidently enhanced the ambient and indoor air quality. This paper investigates the possible emission sources and evaluates the meteorological conditions that may affect the dispersion and transport of BC locally and regionally. Ground-level equivalent BC (eBC) measurements were performed between January 2020 and July 2020 at a university campus located in Dammam city of the Kingdom of Saudi Arabia (KSA). The fossil fuel (eBCff) and biomass burning (eBCbb) fractions of total eBC (eBCt) concentrations were estimated as 84% and 16%, respectively, during the entire study period. The mean eBCbb, eBCff, and eBCt concentrations during the lockdown reduced by 14%, 24%, and 23%, respectively. The results of statistical analyses indicated that local fossil fuel burning emissions and atmospheric conditions apparently affected the observed eBC levels. Long-range potential source locations, including Iraq, Kuwait, Iran, distributed zones in the Arabian Gulf, and United Arab Emirates and regional source areas, such as the Arabian Gulf coastline of the KSA, Bahrain, and Qatar, were associated with moderate to high concentrations observed at the receptor site as a result of cluster analysis and concentration-weighted trajectory analysis methods.

Source apportionment of black carbon and the feedback effect on the meteorological factors in Beijing, China

Black carbon (BC) is a major light-absorbing component in the atmosphere and plays an important role in aerosol radiative forcing. In this study, the combination of monitoring data and the WRF-Chem model was used to study the source apportionment of BC in China during January 2017. Meanwhile, the aerosol-radiation interaction (ARI) effect of BC was also simulated. We found that the average BC/PM_2.5 ratios were 4.8%, 4.2%, and 3.8% in Shijiazhuang, Tangshan, and Beijing, respectively. The source apportionment suggested that traffic emissions played a dominant role in the BC concentration over Beijing. The traffic, residential, industrial, and power contributions accounted for 41%, 32%, 25%, and 2% of total concentration, respectively. The BC concentration in Beijing was also affected by regional transport. During January, the contributions of monthly regional transport to BC and PM_2.5 concentrations in Beijing were 41% and 49%, respectively. BC emissions decreased downward shortwave radiation (SWDOWN) at the surface, leading to a decrease in temperature. As a result, the planetary boundary layer height (PBLH) development was suppressed and the relative humidity increased. The stable meteorological conditions suppressed the dispersion of air pollutants and increased BC concentrations. Traffic emissions decreased the monthly SWDOWN by approximately 2.2 W/m², decreased 2 m temperature (T2) by approximately 0.1 °C, increased 2 m relative humidity (RH2) by approximately 0.5%, and decreased PBLH by approximately 4.4 m.

Annual variations of black carbon over the Yangtze River Delta from 2015 to 2018

In this study, the black carbon (BC) measurements in the atmosphere of Nanjing, China were continuously conducted from 2015 to 2018 using a Model AE-33 aethalometer. By combining dataset of PM_2.5, PM₁₀, CO, NO₂, SO₂, O₃ and meteorological parameters, the temporal variations and the source apportionment of BC were given in this study. The results showed that the PM_2.5 mass concentrations decreased in Nanjing, with an average annual rate of variation of 6.50 μg/(m³⋅year). Differently, the annual average concentrations of BC increased with an average annual variation rate of 214.71 ng/(m³⋅year). The seasonal variations showed the pattern of BC mass concentrations in winter > autumn > spring > summer. The diurnal variations of BC mass concentrations showed a double-peak in all four seasons. The first peak occurred at approximately 7:00 in spring, summer and autumn and around 8:00 in winter. The second peak took place after 18:00. The average AAE (absorption Ångström exponent) was 1.26 with a maximum of 1.35 during wintertime and the lowest (1.12) during summertime. In addition, the AAE was smaller in the daytime than that at night, with a minimum occurring between 13:00 and 14:00. BC and visibility show a good power-function relationship at different humidity levels. The average values of the visibility thresholds of the BC mass concentrations in spring, summer, autumn and winter were 1.326, 5.522, 1.340 and 0.708 μg/m³, respectively. The greater the relative humidity, the smaller the visibility threshold for the BC mass concentrations was.

Study on the characteristics of black carbon during atmospheric pollution conditions in Beijing

Black carbon (BC), not only has a negative impact on human health, but also contributes to visibility degradation and the attenuation of solar radiation due to light absorption. In this paper, we investigated the variations of BC concentration, BC optical characteristics and its effects on the physical and optical properties of atmospheric aerosols based on AERONET data during atmospheric pollution conditions in Beijing from 2012 to 2017. The results indicated that the average annual ground-level BC concentration and BC/PM_2.5 were 8.9 μg m^-3 and 6.7%, respectively, from 2012 to 2017 during atmospheric pollution conditions in Beijing. The annual mean ground-level BC concentration showed weak variation, but the monthly variation was pronounced during atmospheric pollution conditions. Moreover, the BC column concentration had a higher correlation with absorptive aerosol optical thickness (AAOT) at 870 nm (R² = 0.93) than 440 nm (R² = 0.73). The difference in AAOT between 440 nm and 870 nm was more significant under high BC column concentration. The seasonal variation of the BC column concentration that contributed to the AAOT at 870 nm displayed a consistent monthly average variation tendency. The BC column concentrations were divided into three segments of low, moderate, and high according to the results of the approximately normal distribution of the BC column concentration. Compared with high BC concentration, the single scattering albedo (SSA) and asymmetry parameter were enhanced by 0.05 and 0.04 in low BC concentrations, respectively. On the contrary, the fine mode fraction (FMF) was dropped by 12.5% in low BC concentrations. A higher BC concentration contributed to the enhancement in the AAOT and the extinction ratio of the fine mode aerosol. Meanwhile, the atmospheric particles' forward scattering ability was also attenuated under a high BC concentration.

Variation in black carbon concentration and aerosol optical properties in Beijing: Role of emission control and meteorological transport variability

Black carbon (BC), which is a by-product with incomplete combustion of carbonaceous materials, can be used as an indicator of combustion emissions and is an important climate forcer. In this study, a spatial-temporal synthesis of BC aerosols and the affecting factors was conducted in urban Beijing. As observed, BC showed a spatial pattern with high concentration in south and low in north. BC concentration evidently decreased by approximately 61% between 2005 and 2017. From 2015 to 2017, the mass ratio of BC/PM_2.5 dropped by 28%, which suggested a more efficient effect of control measures to BC than PM_2.5. The BC/CO ratio dropped by 22%, which indicated the decreasing emission from fossil fuel sources. With regard to BC loading, the spectral dependence of absorption aerosol exhibited significant seasonal variations. High absorption Ångström exponent (α) was observed during heating season, which reflected the increasing contribution of brown carbon (BrC) to light absorption. Backward trajectory analysis showed that the levels of BC and PM_2.5 were high in Cluster-South and Cluster-West. BrC absorption was high in Cluster-West, Cluster-Northwest and Cluster-Northeast, due to the biomass and coal burning for domestic heating and aging processes on a regional scale. The effects of emission control and transport variability on pollutant variation were estimated on the basis of the cluster analysis. Results indicated that the effect of emission reduction was the major reason for the decrease of BC from 2015 to 2017, which resulted in a 34% reduction of BC concentration. Meanwhile, transport variability caused a 15% reduction.

Contrasting mixing state of black carbon-containing particles in summer and winter in Beijing

Black carbon (BC) exerts a large impact on climate radiative forcing and public health, and such impacts depend strongly on chemical composition and mixing state. Here a single particle aerosol mass spectrometry (SPA-MS) along with an aerosol chemical speciation monitor was employed to characterize the composition and mixing state of BC-containing particles in summer and winter in Beijing. Approximately 2 million BC-containing particles were chemically analyzed, and the particles were classified into nine and eight different types in summer and winter, respectively, according to mass spectral signatures and composition. The BC-containing particles in summer were dominated by the type of nitrate-related BC (BC-N, 56.7%), while in winter the BC mixed with organic carbon (OC) and sulfate (BCOC-S), and OC and nitrate (BCOC-N) were two dominant types accounting for 44.9% and 16.6%, respectively. The number fractions of BC-N in summer, and BCOC-N and BC-SN in winter increased largely during periods with severe air pollution, suggesting the enhanced secondary formation on BC-containing particles. We also found that the primary emissions of the biomass burning and coal combustion can affect BC mixing state substaintially as indicated by the considerable fraction of BC mixed with levoglucosan and polycyclic aromatic hydrocarbons in winter. Bivariate polar plots and back trajectory analysis indicated that the sulfate-associated BC-containing particles were mostly from regional transport while the nitrate-related type was more from local production. The optical parameter of absorbing Ångström exponents (AAE) of BC was 1.2 and 1.5 in summer and winter, respectively, and the AAE dependence of BC mixing state was also different in the two seasons. While higher fractions of BC-N were observed during lower AAE periods in summer, the variations of dominant OC-related BC-containing particles in winter were fairly stable as a function of AAE.

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

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

Role and Mechanisms of Black Carbon Affecting Water Vapor Transport to Tibet

Although some studies reported the impact of black carbon (BC) on the climate over the Tibetan Plateau (TP), the contribution and mechanisms of BC affecting the water vapor transport to Tibet are not fully understood yet. Here, utilizing the satellite observations and reanalysis data, the effects of BC on the climate over the TP and water vapor transport to the Tibet were investigated by the Community Earth System Model (CESM 2.1.0). Due to the addition of BC, a positive net heat forcing (average is 0.39 W/m2) is exerted at the surface, which induces a pronounced warming effect over the TP and consequently intensifies the East Asian Summer monsoon (EASM). However, significant cooling effects in northern India, Pakistan, Afghanistan and Iran are induced due to the BC and related feedbacks, which reduces significantly the meridional land–sea thermal contrast and finally weakens the South Asian summer monsoon (SASM). Consequently, the water vapor transport to the south border is decreased due to addition of BC. Moreover, through affecting the atmospheric circulation, the BC could induce an increase in the imported water vapor from the west and east borders of the TP, and an increase outflowing away from the north border of the TP. Overall, due to the BC, the annual mean net importing water vapor over TP is around 271 Gt, which could enhance the precipitation over the TP. The results show that the mean increase in the precipitation over TP is about 0.56 mm/day.

The characteristics and local-regional contributions of atmospheric black carbon over urban and suburban locations in Shanghai, China

Black carbon (BC), produced from the incomplete combustion of carbonaceous fuels, has emerged as a major contributor to global climate change with adverse health effects. Based on one-year (2016.06.01-2017.06.30) equivalent black carbon (eBC) measurements, this study analyzed the characteristics of eBC concentrations and the local-regional contributions at an urban site (Pudong, PD) and a suburban site (Qingpu, QP) in Shanghai, China. The results showed that the annual average eBC concentrations were 1.17 ± 0.61 μg m^-3 and 2.09 ± 0.97 μg m^-3 at PD and QP, respectively. The high eBC concentrations occurred in winter and at weekends both for PD and QP. There were significant negative correlation coefficients between the daily eBC, the daily wind speed (WS) and the daily boundary layer height (BLH) at PD (r_ws: 0.45, r_blh = -0.35, p < 0.01) and QP (r_ws: 0.49, r_blh = -0.32, p < 0.01). And the relative higher eBC concentrations coincided with southerly, southwesterly and westerly winds although these winds had lower frequencies. This could be related to the agricultural fire in these directions during summer harvesttime. The significant partial correlation coefficients of eBC-CO (r_u:0.37-0.64, r_s:0.18-0.44, p < 0.01) and eBC-NO₂ (r_u:0.49-0.74, r_s:0.38-0.75, p < 0.01) could suggest that eBC mainly come from vehicular exhaust emissions in Shanghai. Besides, the higher eBC/PM_2.5 (5.29% ± 1.94%) and eBC/CO(0.30% ± 0.14%) at QP indicated the more combustion activities and diesel-powered vehicle emissions in suburban areas. The concentration weighted trajectory (CWT) analysis indicated that the surrounding areas at the junction of Shanghai, Jiangsu, and Zhejiang provinces seemed to be relatively the most important sources outside of Shanghai.

Association of Long-term Ambient Black Carbon Exposure and Oxidative Stress Allelic Variants With Intraocular Pressure in Older Men

Importance

Elevated intraocular pressure is a major risk factor for glaucoma, a leading cause of irreversible blindness worldwide. Environmental air pollution has been suggested as a potential contributor to elevated intraocular pressure; however, no studies have demonstrated such an association to date.

Objective

To investigate the association of long-term ambient black carbon exposure with intraocular pressure in community-dwelling older adults.

Design, Setting, and Participants

This population-based analysis, conducted from October 18, 2017, through March 22, 2018, used data from the all-male, New England-based Normative Aging Study of the US Department of Veterans Affairs. The analysis included 419 older men with a total of 911 follow-up study visits between January 1, 2000, and December 30, 2011. Intraocular pressure was measured by Goldmann applanation tonometry during the study visits. Validated spatiotemporal models were used to generate 1-year black carbon exposure levels at the addresses of the participants.

Main Outcomes and Measures

An independently developed genetic score approach was used to calculate allelic risk scores for 3 pathways associated with black carbon toxicity: endothelial function, oxidative stress, and metal processing. The associations among black carbon exposure, allelic risk scores, and intraocular pressure were explored using linear mixed-effects models.

Results

All 419 participants were men with a mean (SD) age of 75.3 (6.9) years. The mean (SD) 1-year black carbon exposure was 0.51 (0.18) μg/m3, and the mean (SD) intraocular pressure for the left eye was 14.1 (2.8) mm Hg and for the right eye was 14.1 (3.0) mm Hg. Of the 911 visits, 520 (57.1%) had a high endothelial function allelic risk score, 644 (70.7%) had a high metal-processing allelic risk score, and 623 (68.4%) had a high oxidative stress allelic risk score. In fully adjusted linear mixed-effects models, the association of black carbon with intraocular pressure was greater in individuals with a high oxidative stress allelic score (β = 0.36; 95% CI, 0.003-0.73) compared with individuals with a low score (β = -0.35; 95% CI, -0.86 to 0.15).

Conclusions and Relevance

Ambient black carbon exposure may be a risk factor for increased intraocular pressure in individuals susceptible to other biological oxidative stressors. If additional studies confirm these results, monitoring ambient black carbon exposure and physiological oxidative stress may prevent the development and progression of intraocular pressure-related disease.

Knowledge, attitudes, practices and information demand in relation to haze in China: a cross-sectional study

BACKGROUND

Information on the effects of haze on health and corresponding knowledge, attitudes, and practices (KAP) will improve self-care ability against the ill effects of haze pollution and make environmental health policies more targeted and effective. In this study, we aim to determine the KAP and information demand in the context of haze and its effects on health.

METHODS

A cross-sectional survey was conducted in Changchun, China, between October and November 2016. A purposive sample comprising four groups (college students, occupational population, traffic police, and elderly population) were investigated. Personal information and questions pertaining to KAP and information demand on haze pollution and health were collected through questionnaire.

RESULTS

The questionnaire was completed by 888 residents. The awareness rate was 57.7% and varied significantly with education, exercise, and population group (p < 0.05). Among the four groups, college students scored the lowest in attitudes and practices, whereas traffic police scored the highest. Concerning the source of information demand, the elderly and traffic police preferred traditional information access (i.e., television and newspaper), whereas college students and the occupational population preferred new social media (i.e., mobile newspaper and social media sites). Regarding the most trusted department that releases information, all residents relied on the haze information released by the environmental protection department and meteorological department. The latest air quality was the most desired information of the residents.

CONCLUSIONS

Changchun residents have a relatively high knowledge awareness rate. The elderly and less-educated residents are the targetable population for haze education. Education should be disseminated in such manner as to meet the needs of different people.

The carbonaceous aerosol levels still remain a challenge in the Beijing-Tianjin-Hebei region of China: Insights from continuous high temporal resolution measurements in multiple cities

Carbonaceous aerosols in high emission areas attract worldwide attention of the scientific community and the public due to their adverse impacts on the environment, human health and climate. However, long-term continuous hourly measurements are scarce on the regional scale. In this study, a one-year hourly measurement (from December 1, 2016 to November 30, 2017) of organic carbon (OC) and elemental carbon (EC) in airborne fine particles was performed using semi-continuous OC/EC analyzers in Beijing, Tianjin, Shijiazhuang and Tangshan in the Beijing-Tianjin-Hebei (BTH) region in China, which is one of high emission areas in China, even in the world. Marked spatiotemporal variations were observed. The highest concentrations of OC (22.8 ± 30.6 μg/m³) and EC (5.4 ± 6.5 μg/m³) occurred in Shijiangzhuang while the lowest concentrations of OC (11.0 ± 10.7 μg/m³) and EC (3.1 ± 3.6 μg/m³) were obtained in Beijing and Tianjin, respectively. Pronounced monthly, seasonal and diurnal variations of OC and EC were recorded. Compared to published data from the past two decades for the BTH region, our OC and EC levels were lower, implying some effect of recent measures for improving the air quality. Significant correlations of OC versus EC (p < 0.001) were found throughout the study period with high slopes and correlation coefficients in winter, but low slopes and correlation coefficients in summer. The estimated secondary OC (SOC), based on the minimum R squared (MRS) method, represented 29%, 47%, 38% and 48% of the OC for Beijing, Tianjin, Shijiazhuang and Tangshan, respectively. These percentages are larger than previous ones obtained for the BTH region in the past decade. There were obvious differences in the potential source regions of OC and EC among the four cities. Obvious prominent potential source areas of OC and EC were observed for Beijing, which were mainly located in the central and western areas of Inner Mongolia and even extended to the Mongolian regions, which is different from the findings in previous studies. For all sites, adjacent areas of the main provinces in northern China were found to be important potential source areas.

Characterization and source identification of fine particulate matter in urban Beijing during the 2015 Spring Festival

The Spring Festival (SF) is the most important holiday in China for family reunion and tourism. During the 2015 SF an intensive observation campaign of air quality was conducted to study the impact of the anthropogenic activities and the dynamic characteristics of the sources. During the study period, pollution episodes frequently occurred with 12days exceeding the Chinese Ambient Air Quality Standards for 24-h average PM_2.5 (75μg/m³), even 8days with exceeding 150μg/m³. The daily maximum PM_2.5 concentration reached 350μg/m³ while the hourly minimum visibility was <0.8km. Three pollution episodes were selected for detailed analysis including chemical characterization and diurnal variation of the PM_2.5 and its chemical composition, and sources were identified using the Positive Matrix Factorization model. The first episode occurring before the SF was characterized by more formation of SO₄^2- and NO₃^- and high crustal enrichment factors for Ag, As, Cd, Cu, Hg, Pb, Se and Zn and seven categories of pollution sources were identified, whereby vehicle emission contributed 38% to the PM_2.5. The second episode occurring during the SF was affected heavily by large-scale firework emissions, which led to a significant increase in SO₄^2-, Cl^-, OC, K and Ba; these emissions were the largest contributor to the PM_2.5 accounting for 36%. During the third episode occurring after the SF, SO₄^2-, NO₃^-, NH₄⁺ and OC were the major constituents of the PM_2.5 and the secondary source was the dominant source with a contribution of 46%. The results provide a detailed understanding on the variation in occurrence, chemical composition and sources of the PM_2.5 as well as of the gaseous pollutants affected by the change in anthropogenic activities in Beijing throughout the SF. They highlight the need for limiting the firework emissions during China's most important traditional festival.

Distribution and health risks of aerosol black carbon in a representative city of the Qinghai-Tibet Plateau

Although aerosol black carbon (BC) exerts strong influences on human health, research on potential health risks of aerosol BC around the Qinghai-Tibet Plateau is very limited. This is the very first study to investigate the distribution of aerosol BC in a typical city of the Qinghai-Tibet Plateau and the resulting health risks. The results showed that the maximal real-time (5-min monitoring interval) concentration of aerosol BC was 22.34 μg/m³, much higher than day- and week-averaged concentrations which were in the range of 1.28-6.15 and 1.93-4.63 μg/m³, respectively. The health risks were evaluated using four different health endpoints including low birth weight (LBW), percentage lung function decrement of school-aged children (PLFD), cardiovascular mortality (CM), and lung cancer (LC). The highest risks of LBW, PLFD, CM, and LC had reached 69.5, 184.4, 67.4, and 31.8 numbers of equivalent passively smoked cigarettes (PSC), respectively. The concentrations and health risks of aerosol BC in the study area are at a middle level among the global cities/regions. In comparison, the cities of the Qinghai-Tibet Plateau are experiencing high potential health risks resulting from aerosol BC to need more effective prevention and control of air pollution.

Two-year continuous measurements of carbonaceous aerosols in urban Beijing, China: Temporal variations, characteristics and source analyses

Organic carbon (OC) and elemental carbon (EC) in the PM_2.5 of urban Beijing were measured hourly with a semi-continuous thermal-optical analyzer from Jan 1, 2013 to Dec 31, 2014. The annual average OC and EC concentrations in Beijing were 17.0 ± 12.4 and 3.4 ± 2.0 μg/m³ for 2013, and 16.8 ± 14.5 and 3.5 ± 2.9 μg/m³ for 2014. It is obvious that the annual average concentrations of OC and EC in 2014 were not less than those in 2013 while the annual average PM_2.5 concentration (89.4 μg/m³) in 2014 was slightly reduced as compared to that (96.9 μg/m³) in 2013. Strong seasonality of the OC and EC concentrations were found with high values during the heating seasons and low values during the non-heating seasons. The diurnal cycles of OC and EC characterized by higher values at night and in the morning were caused by primary emissions, secondary transformation and stable meteorological condition. Due to increasing photochemical activity, the OC peaks were observed at approximately noon. No clear weekend effects were observed. Interestingly, in the early mornings on weekends in the autumn and winter, the OC and EC concentrations were close to or higher than those on weekdays. Our data also indicate that high OC and EC concentrations were closely associated with their potential source areas which were determined based on the potential source contribution function analysis. High potential source areas were identified and were mainly located in the south of Beijing and the plain of northern China. A much denser source region was recorded in the winter than in the other seasons, indicating that local and regional transport over regional scales are the most important. These results demonstrate that both regional transport from the southern regions and local accumulation could lead to the enhancements of OC and EC and likely contribute to the severe haze pollution in Beijing.