Field validation of a semi-continuous method for aerosol black carbon (aethalometer) and temporal patterns of summertime hourly black carbon measurements in southwestern PA
Abstract
Two methods for measuring aerosol elemental carbon (EC) are compared. Three-hour integrated carbon samples were collected on quartz filters during the summer of 1990 in Uniontown, PA, primarily during episodes of elevated particulate pollution levels. These samples were analyzed for EC and organic carbon (OC) using a thermo/optical reflectance (TOR) method. Aerosol black carbon (BC) was measured using an Aethalometer, a semi-continuous optical absorption method. The optical attenuation factor for ambient BC was supplied by the instrument manufacturer. Three-hour average concentrations were calculated from the semi-continuous BC measurements to temporally match the EC/OC integrated quartz filter samples. BC and EC concentrations are highly correlated over the study period (R2=0.925). The regression equation is BC (μg m-3)=0.95 (±0.04) EC−0.2 (±0.4). The means of 3 h average measurements for EC and BC are 2.3 and 2.0 μg m-3, respectively, average concentrations of EC and BC ranged from 0.6 to 9.4 and 0.5 to 9.0 μg m-3 respectively. TOR OC and EC concentrations were not highly correlated (R2=0.22). The mean OC/EC ratio was 1.85.
The 10-week Aethalometer hourly dataset was analyzed for daily and weekly temporal patterns. A strong diurnal BC pattern was observed, with peaks occurring between 7 a.m. and 9 a.m. local time. This is consistent with the increase in emissions from ground level combustion sources in the morning, coupled with poor dispersion before daytime vertical mixing is established. There was also some indication of a day-of-week effect on BC concentrations, attributed to activity of local ground level anthropogenic sources. Comparison of BC concentrations with co-located measurements of coefficient of haze in a separate field study in Philadelphia, PA, during the summer of 1992 showed good correlation between the two measurements (R2=0.82).
References (0)
Cited by (182)
Emissions of black carbon and polycyclic aromatic hydrocarbons: Potential implications of cultural practices during the Covid-19 pandemic
2023, Gondwana ResearchEmissions of black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) from various anthropogenic activities are often reported, yet cultural practices such as the multi-day Diwali festival and its influences on the emissions of these compounds are often overlooked. Major activities during this festival include burning rows of oil-filled earthen lamps (diyas) and fireworks (bursting of crackers). A comprehensive field investigation was conducted to document the role of Diwali celebrations on the releases of BC and PAHs during the ongoing Covid pandemic. The results show that large-scale releases of BC and PAHs were observed on the first day of Diwali compared to the remaining four days. BC and PM2.5 mass concentrations throughout the monitoring period ranged from 3.24 to 27.64 µg m−3 and 83.33 to 288.13 µg m−3, respectively. The source apportionment was performed based on the calculated backward trajectories. The results show that the contribution of fossil fuel emission at Adityapur (ADP), Sakchi (SAK), and Gamharia (GMA) was approximately 36.1 %, 34.4 %, and 55.56 %, while biomass burning contribution was approx. 56.9 %, 59.9 %, 41.67 %, respectively. The result showed that fossil fuel emissions were lower compared to biomass combustion during Diwali. Simultaneously, PAHs diagnostic ratio showed that vehicular discharge and coal burning significantly contributed to PAHs at these study sites.
Characterization, seasonal variation, source apportionment and health risk assessment of black carbon over an urban region of East India
2021, Urban ClimateBlack carbon (BC) is produced due to the incomplete combustion of fossil fuels and rapidly accelerates the globe. The study of the source apportionment exploration of BC is inaccurate due to lacking observational limitations and uncertainties in emission inventories. In the present work, we measured BC mass concentrations using a 7-wavelength Aethalometer (AE-33). In this study, BC mass concentration was ranging from 2 to 13.43 μgm−3 and was minimum during monsoon (3.23 ± 0.38 μgm-3) and maximum in the winter season (11.68 ± 2.55μgm−3). The annual mean BC mass concentration and PM2.5 were reported as 6.60 ± 3.50 μgm−3 and 119.07 ± 43.44 μgm-3, respectively. In overall study, the BC aerosol was contributing 6.92% (winter), 5.09% (summer), 3.79% (monsoon) and 5.25% (post-monsoon) to the total mass concentration of PM2.5. Backward Trajectories have shown that the airborne particulate matter comes from different directions in different seasons. Correlation analysis has found a strong relationship between BC and PM2.5 (r = 0.89, r2 = 0.80). However, an inverse relationship was noticed between BC and temperature(r = −0.92), wind speed (r = −0.61), precipitation (r = −0.60) and humidity (r = −0.52) during the observational period. Apart from describing BC's atmospheric impacts, the health risk assessment of BC during various seasons over Jamshedpur city is also illustrated in detail.
Effect of discrepancies caused by model resolution on model-measurement comparison for surface black carbon
2021, Atmospheric EnvironmentEmission constraining studies have relied on comparisons of model against measurements, but the influence of model resolution has not been fully addressed. This work investigates the discrepancies caused by model resolution on model-measurement comparison of surface black carbon for urban and rural monitoring network sites in the U.S. With resolution of 0.5°, simulated BC concentrations were 106% greater at urban receptors in California than simulations with 2° resolution; the overprediction was 30% greater for rural network sites (IMPROVE). This effect could explain 24%–41% of the total discrepancy in model-measurement comparison for networks in California. For rural sites elsewhere in the U.S., increasing resolution from 2° to 0.5° results in either over- and under-prediction, with an averaged discrepancy of 6%. Factors describing the model resolution discrepancy for each urban and rural receptor site are tabulated.
Study on the characteristics of black carbon during atmospheric pollution conditions in Beijing
2020, Science of the Total EnvironmentBlack 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/PM2.5 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.
Characteristics of visibility-impairing aerosol observed during the routine monitoring periods in Gwangju, Korea
2018, Atmospheric EnvironmentAerosol chemistry measurements were performed during the routine monitoring periods in the urban atmosphere of Gwangju, Korea. Routine aerosol monitoring was carried out every sixth day in order to investigate the dependence of domestic sources and air mass transport characteristics on physicochemical and optical properties of atmospheric aerosol. Aerosol optical properties; atmospheric extinction and scattering coefficients were also measured continuously with a transmissometer and a nephelometer, respectively in order to investigate the causes of visibility impairment. Prevailing atmospheric condition was classified into four categories; one affected by stagnant condition (D), one affected by continental and domestic aerosols (CD), one affected by marine and domestic aerosols (MD), and one affected by continental, marine and domestic aerosols (CMD). Atmospheric condition type was further classified into thirteen sub-categories with the occurrences of episodic events such as Asian dust storm, biomass burning, and airborne pollen. The air mass types of D, CD, MD, and CMD were observed to be 11, 18, 43, and 78 events out of total 150 events, respectively. The fine mass concentration increased under continental air mass types. The average fine mass concentration of 23.0 ± 8.6 μg m−3 for CD type was slightly larger than that of 20.7 ± 5.2 μg m−3 for CMD type. Both of them were higher than that for D (18.9 ± 4.5 μg m−3) type. Increments of the fine mass concentrations for Asian dust storm (A) and Biomass-burning (B) events ranged from 141 to 151% and from 152 to 160% compared to those for D and CD types, respectively. The increments in the mass concentrations of nitrate, OC, EC, and BC for CD and CMD types in comparison with D air mass type were calculated to be approximately 17, 6, 8, and 22%, respectively. The mean mass extinction efficiency of PM10 was relatively higher in D (3.6 ± 1.6 m2 g−1) type and B events (4.1 ± 1.5 m2 g−1), but it was the lowest in MD air mass type. The aerosols observed in Gwangju were found to be influenced by the continental aerosol during the A events. Aerosol of CMD air mass type caused mainly poor visibility. The visibility reduction of Gwangju was influenced by the increase of carbonaceous particles under both domestically stagnant condition and air mass pathway from the continent. And ammonium sulfates and ammonium nitrates contributed the largest in CMD air mass type.
Investigation of aerosol black carbon over semi-urban and urban locations in south-western India
2018, Atmospheric Pollution ResearchTemporal evolution of the ‘dual-spot’ 7-channel Aethalometer measured black carbon (BC) aerosols over different time scales, their potential source regions and impact of meteorology on BC mass are analyzed using observational data at Ahmednagar College (AC-Ahmednagar), Ahmednagar and Indian Institute of Tropical Meteorology, Pashan (IITM-Pashan), Pune. Results reveal well defined bimodal diurnal pattern in BC mass; one in morning (07:00-09:00 LT) and another in evening (around 20:00 LT) at both sites. This is quite consistent with seasonally changing BC mass and is the combined effects of variations in anthropogenic emissions, meteorology and associated atmospheric boundary layer (ABL) dynamics. BC mass concentration at AC-Ahmednagar and IITM-Pashan varied from 1.8 to 49.0 μg m−3 (annual mean 13.8 ± 10.4 μg m−3) and 0.7–21.6 μg m−3 (annual mean 3.9 ± 2.8 μg m−3) respectively. Annual BC cycle at AC-Ahmednagar, IITM-Pashan, Delhi and Xian (China) appears to be similar. However, BC mass at AC-Ahmednagar being of the same order to that reported at Delhi (India) and Xi'an (China), it is about 3.5 times higher than at IITM-Pashan. The present work, further, demonstrates prominent role exerted by surface temperature (T) and relative humidity (RH) in modulating BC mass. Occurrence of high ΔBC (BC370 nm – BC880 nm) and absorption Ångström exponent (AAE) are indicative of enhanced absorption in near-UV and low-visible wavelengths attributed to the presence of biomass burning and light absorbing particulate matter. The back-trajectory cluster and concentrated weighted trajectory (CWT) analysis identifies four distinct potential BC source regions at the present receptor sites.