scholarly journals Seasonal contrast in size distributions and mixing state of black carbon and its association with PM<sub>1.0</sub> chemical composition from the eastern coast of India

2020 ◽  
Vol 20 (6) ◽  
pp. 3965-3985 ◽  
Author(s):  
Sobhan Kumar Kompalli ◽  
Surendran Nair Suresh Babu ◽  
Sreedharan Krishnakumari Satheesh ◽  
Krishnaswamy Krishna Moorthy ◽  
Trupti Das ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Black Carbon ◽  
Mass Concentration ◽  
Monsoon Season ◽  
Regional Climate ◽  
Eastern Coast ◽  
Size Distributions ◽  
Mixing State ◽  
Air Masses ◽  
Microphysical Properties

Abstract. Over the Indian region, aerosol absorption is considered to have a potential impact on the regional climate, monsoon and hydrological cycle. Black carbon (BC) is the dominant absorbing aerosol, whose absorption potential is determined mainly by its microphysical properties, including its concentration, size and mixing state with other aerosol components. The Indo-Gangetic Plain (IGP) is one of the regional aerosol hot spots with diverse sources, both natural and anthropogenic, but still the information on the mixing state of the IGP aerosols, especially BC, is limited and a significant source of uncertainty in understanding their climatic implications. In this context, we present the results from intensive measurements of refractory BC (rBC) carried out over Bhubaneswar, an urban site in the eastern coast of India, which experiences contrasting air masses (the IGP outflow or coastal/marine air masses) in different seasons. This study helps to elucidate the microphysical characteristics of BC over this region and delineates the IGP outflow from the other air masses. The observations were carried out as part of South West Asian Aerosol Monsoon Interactions (SWAAMI) collaborative field experiment during July 2016–May 2017, using a single-particle soot photometer (SP2) that uses a laser-induced incandescence technique to measure the mass and mixing state of individual BC particles and an aerosol chemical speciation monitor (ACSM) to infer the possible coating material. Results highlighted the distinctiveness in aerosol microphysical properties in the IGP air masses. BC mass concentration was highest during winter (December–February) (∼1.94±1.58 µg m−3), when the prevailing air masses were mostly of IGP origin, followed by post-monsoon (October–November) (mean ∼1.34±1.40 µg m−3). The mass median diameter (MMD) of the BC mass size distributions was in the range 0.190–0.195 µm, suggesting mixed sources of BC, and, further, higher values (∼ 1.3–1.8) of bulk relative coating thickness (RCT) (ratio of optical and core diameters) were seen, indicating a significant fraction of highly coated BC aerosols in the IGP outflow. During the pre-monsoon (March–May), when marine/coastal air masses prevailed, BC mass concentration was lowest (∼0.82±0.84 µg m−3), and larger BC cores (MMD > 0.210 µm) were seen, suggesting distinct source processes, while RCT was ∼ 1.2–1.3, which may translate into higher extent of absolute coating on BC cores, which may have crucial regional climate implications. During the summer monsoon (July–September), BC size distributions were dominated by smaller cores (MMD ≤ 0.185 µm), with the lowest coating indicating fresher BC, likely from fossil fuel sources. A clear diurnal variation pattern of BC and RCT was noticed in all the seasons, and daytime peak in RCT suggested enhanced coating on BC due to the condensable coating material originating from photochemistry. Examination of submicrometre aerosol chemical composition highlighted that the IGP outflow was dominated by organics (47 %–49 %), and marine/coastal air masses contained higher amounts of sulfate (41 %–47 %), while ammonium and nitrate were seen in minor amounts, with significant concentrations only during the IGP air mass periods. The diurnal pattern of sulfate resembled that of the RCT of rBC particles, whereas organic mass showed a pattern similar to that of the rBC mass concentration. Seasonally, the coating on BC showed a negative association with the mass concentration of sulfate during the pre-monsoon season and with organics during the post-monsoon season. These are the first experimental data on the mixing state of BC from a long time series over the Indian region and include new information on black carbon in the IGP outflow region. These data help in improving the understanding of regional BC microphysical characteristics and their climate implications.

scholarly journals Seasonal contrast in size distributions and mixing state of black carbon and its association with PM1.0 chemical composition from the eastern coast of India

2019 ◽  
Author(s):  
Sobhan Kumar Kompalli ◽  
Surendran Nair Suresh Babu ◽  
Sreedharan Krishnakumari Satheesh ◽  
Krishnaswamy Krishna Moorthy ◽  
Trupti Das ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Black Carbon ◽  
Mass Concentration ◽  
Regional Climate ◽  
Eastern Coast ◽  
Size Distributions ◽  
Organic Mass ◽  
Mixing State ◽  
Post Monsoon ◽  
Microphysical Properties

Abstract. Over the Indian region, aerosol absorption is considered to have potential impact on regional climate, monsoon and hydrological cycle. Black carbon (BC) is the dominant absorbing aerosol, whose absorption potential is largely determined by its microphysical properties, including its concentration, size and mixing state with other aerosol components. The Indo-Gangetic Plains (IGP) is one of the regional aerosol hot spots with diverse sources, both natural and anthropogenic, but still the information on the mixing state of the IGP aerosols, especially BC, is limited and a major source of uncertainty in understanding their climatic implications. In this context, we present the results from intensive measurements of refractory BC (rBC) carried out over Bhubaneswar, an urban site in the eastern coast of India, which experiences contrasting airmasses (the IGP outflow or coastal/marine airmasses) in different seasons. This study helps to elucidate the microphysical characteristics of BC over this region and delineates the IGP outflow from the other airmasses. The observations were carried out as part of South West Asian Aerosol Monsoon Interactions (SWAAMI) collaborative field experiment during July 2016–May 2017, using a single particle soot photometer (SP2) that uses a laser-induced incandescence technique to measure the mass and mixing state of individual BC particles and an aerosol chemical speciation monitor (ACSM). Results highlighted the distinctiveness in aerosol microphysical properties in the IGP airmasses. BC mass concentration was highest during winter (~ 1935 ± 1578 ng m−3), when the prevailing air masses were mostly of IGP origin, followed by post-monsoon (mean ~1338 ± 1396 ng m−3). Mass median diameter (MMD) of the BC mass size distributions were in the range 0.190–0.195 µm suggesting mixed sources of BC, and further, higher values (~ 1.3–1.8) of bulk relative coating thickness (RCT) (ratio of optical and core diameters) were seen indicating a large fraction of highly coated BC aerosols in the IGP outflow. During the pre-monsoon, when marine/coastal airmasses prevailed, BC mass concentration was lowest (~ 816 ± 835 ng m−3) and larger BC cores (MMD > 0.210 µm) were seen suggesting distinct source processes, while RCT was ~ 1.2–1.3, which may translate into higher extent of absolute coating on BC cores which may have important regional climate implications. During the summer monsoon, BC size distributions were dominated by smaller cores (MMD ≤ 0.185 µm) with lowest coating, indicating fresher BC, likely from fossil fuel sources. A clear diurnal variation pattern of BC and RCT was noticed in all the seasons, and day time peak in RCT suggested enhanced coating on BC due to the condensable coating material originated from photochemistry. Examination of sub-micron aerosol chemical composition highlighted that the IGP outflow is dominated by organics (47–49 %) and marine/coastal airmasses contained greater amounts of sulphate (41–47 %), while ammonium and nitrate were seen in minor amounts with significant concentrations only during the IGP airmass periods. The diurnal pattern of sulphate resembled that of the RCT of rBC particles, whereas organic mass showed a pattern similar to that of the rBC mass concentration. Though the pre-monsoon is sulphate dominated, the coating on BC showed a negative association with sulphate and same is true for organic mass during the post-monsoon, suggesting preferential coating and importance of source processes (and co-emitted species) on the mixing state of BC. This is the first experimental data on the mixing state of BC from a long time series over the Indian region, and includes new information on black carbon in the IGP outflow region. This data helps in improving the understanding of regional BC microphysical characteristics and their climate implications.

scholarly journals Measurements to determine the mixing state of black carbon emitted from the 2017–2018 California wildfires and urban Los Angeles

2020 ◽  
Vol 20 (24) ◽  
pp. 15635-15664
Author(s):  
Joseph Ko ◽  
Trevor Krasowsky ◽  
George Ban-Weiss
Keyword(s):  
Los Angeles ◽  
Black Carbon ◽  
Biomass Burning ◽  
Spatial Scales ◽  
Field Measurements ◽  
Mixing State ◽  
Air Masses ◽  
Microphysical Properties ◽  
Source Type ◽  
Wide Variability

Abstract. The effects of atmospheric black carbon (BC) on climate and public health have been well established, but large uncertainties remain regarding the extent of the impacts of BC at different temporal and spatial scales. These uncertainties are largely due to the heterogeneous nature of BC in terms of its spatiotemporal distribution, mixing state, and coating composition. Here, we seek to further understand the size and mixing state of BC emitted from various sources and aged over different timescales using field measurements in the Los Angeles region. We measured refractory black carbon (rBC) with a single-particle soot photometer (SP2) on Catalina Island, California (∼70 km southwest of downtown Los Angeles) during three different time periods. During the first campaign (September 2017), westerly winds were dominant and measured air masses were representative of well-aged background over the Pacific Ocean. In the second and third campaigns (December 2017 and November 2018, respectively), atypical Santa Ana wind conditions allowed us to measure biomass burning rBC (BCbb) from air masses dominated by large biomass burning events in California and fossil fuel rBC (BCff) from the Los Angeles Basin. We observed that the emissions source type heavily influenced both the size distribution of the rBC cores and the rBC mixing state. BCbb had thicker coatings and larger core diameters than BBff. We observed a mean coating thickness (CTBC) of ∼40–70 nm and a count mean diameter (CMD) of ∼120 nm for BCbb. For BCff, we observed a CTBC of ∼5–15 nm and a CMD of ∼100 nm. Our observations also provided evidence that aging led to an increased CTBC for both BCbb and BCff. Aging timescales < ∼1 d were insufficient to thickly coat freshly emitted BCff. However, CTBC for aged BCff within aged background plumes was ∼35 nm thicker than CTBC for fresh BCff. Likewise, we found that CTBC for aged BCbb was ∼18 nm thicker than CTBC for fresh BCbb. The results presented in this study highlight the wide variability in the BC mixing state and provide additional evidence that the emissions source type and aging influence rBC microphysical properties.

scholarly journals Size distribution and coating thickness of black carbon from the Canadian oil sands operations

2017 ◽  
Author(s):  
Yuan Cheng ◽  
Shao-Meng Li ◽  
Mark Gordon ◽  
Peter Liu
Keyword(s):  
Size Distribution ◽  
Black Carbon ◽  
Coating Thickness ◽  
Oil Sands ◽  
Radiative Forcing ◽  
Climate Models ◽  
Source Area ◽  
Size Distributions ◽  
Mixing State ◽  
Earth’S Climate

Abstract. Black carbon (BC) plays an important role in the Earth’s climate system. However, parameterization of BC size and mixing state have not been well addressed in aerosol-climate models, introducing substantial uncertainties into the estimation of radiative forcing by BC. In this study, we focused on BC emissions from the massive oil sands (OS) industry in northern Alberta, based on an aircraft campaign conducted over the Athabasca OS region in 2013. A total of 14 flights were made over the OS source area, in which the aircraft was typically flown in a 4- or 5-sided polygon pattern along flight tracks encircling an OS facility. Another 3 flights were performed downwind of the OS source area, each of which involved at least three intercepting locations where the well-mixed OS plume was measured along flight tracks perpendicular to the wind direction. Comparable size distributions were observed for refractory black carbon (rBC) over and downwind of the OS facilities, with rBC mass median diameters (MMD) between ~ 135 and 145 nm that were characteristic of fresh urban emissions. This MMD range corresponded to rBC number median diameters (NMD) of ~ 60–70 nm, approximately 100 % higher than the NMD settings in some aerosol-climate models. The typical in- and out-of-plume segments of a flight, which had different rBC concentrations and photochemical ages, showed consistent rBC size distributions. Moreover, rBC size distributions remained unchanged at different downwind distances from the source area, suggesting that atmospheric aging would not necessarily change rBC size distribution. However, aging indeed influenced rBC mixing state. Coating thickness for rBC cores in the diameter range of 130–160 nm was nearly doubled within three hours when the OS plume was transported over a distance of 90 km from the source area.

scholarly journals Mixing state of refractory black carbon aerosol in the South Asian outflow over the northern Indian Ocean during winter

2020 ◽  
Author(s):  
Sobhan Kumar Kompalli ◽  
Surendran Nair Suresh Babu ◽  
Krishnaswamy Krishnamoorthy ◽  
Sreedharan Krishnakumari Satheesh ◽  
Mukunda M. Gogoi ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Black Carbon ◽  
South Asian ◽  
Arabian Sea ◽  
Equatorial Indian Ocean ◽  
Mixing State ◽  
Air Masses ◽  
Continental Outflow ◽  
Mass Concentrations

Abstract. Regional climatic implications of aerosol black carbon (BC) are well recognized over South Asia, which has a wide variety of anthropogenic sources in a large abundance. Significant uncertainties remain in its quantification due to lack of sufficient information on the microphysical properties (its concentration, size, and mixing state with other aerosol components), which determine the absorption potential of BC. Especially the information on mixing state of BC is extremely sparse over this region. In this study, first-ever observations of the size distribution and mixing state of individual refractory black carbon (rBC) particles in the south Asian outflow to Southeastern Arabian Sea, northern and equatorial Indian Ocean regions are presented based on measurements using a single particle soot photometer (SP2) aboard the ship cruise of the Integrated Campaign for Aerosols, gases, and Radiation Budget (ICARB-2018) during winter-2018 (16 January to 13 February). The results revealed significant spatial heterogeneity of BC characteristics. Highest rBC mass concentrations (~ 938 ± 293 ng m−3) with the highest relative coating thickness (RCT; the ratio of BC core to its coating diameters) of ~ 2.16 ± 0.19 are found over the Southeast Arabian Sea (SEAS) region, which is in the proximity of the continental outflow. As we move to farther oceanic regions, though the mass concentrations decreased by nearly half (~ 546 ± 80 ng m−3), BC still remained thickly coated (RCT ~ 2.05 ± 0.07). The air over the remote equatorial Indian Ocean, which received considerable marine air masses compared to the other regions, showed the lowest rBC mass concentrations (~ 206 ± 114 ng m−3), with a moderately thick coating (RCT ~ 1.73 ± 0.16). Even over oceanic regions far from the landmass, regions which received the outflow from more industrialized east coast/the Bay of Bengal had thicker coating (~ 104 nm) compared to regions that received outflow from the west coast/peninsular India (~ 86 nm). Although different regions of the ocean depicted contrasting concentrations and mixing state parameters due to varying extent and nature of the continental outflow as well as the atmospheric lifetime of air masses, the modal parameters of rBC mass-size distributions were similar over all the regions. The observed mono-modal distribution with mean mass median diameters (MMD) in the range of 0.19–0.20 μm suggested mixed sources of BC. The mean fraction of BC containing particles (FBC) varied in the range 0.20–0.28 (suggesting significant amounts of non-BC particles), whereas the bulk mixing ratio of coating mass to rBC mass was highest (8.77 ± 2.77) over the outflow regions compared to the remote ocean (4.29 ± 1.54) highlighting the role of outflow in providing condensable material for coating on rBC. These parameters, along with the information on size-resolved mixing state of BC cores, throw light on the role of sources and secondary processing of their complex mixtures for coating on BC under highly polluted conditions. Examination of the non-refractory sub-micrometre aerosol chemical composition obtained using the aerosol chemical speciation monitor (ACSM) suggested that the overall aerosol system was sulfate dominated over the far-oceanic regions. In contrast, organics were equally prominent adjacent to the coastal landmass. Association between the BC mixing state and aerosol chemical composition suggested that sulfate was the probable dominant coating material on rBC cores.

scholarly journals Impact of different Asian source regions on the composition of the Asian monsoon anticyclone and of the extratropical lowermost stratosphere

2015 ◽  
Vol 15 (23) ◽  
pp. 13699-13716 ◽  
Author(s):  
B. Vogel ◽  
G. Günther ◽  
R. Müller ◽  
J.-U. Grooß ◽  
M. Riese
Keyword(s):  
Chemical Composition ◽  
Southeast Asia ◽  
Asian Monsoon ◽  
Monsoon Season ◽  
Intraseasonal Variability ◽  
Air Masses ◽  
Northern India ◽  
Source Regions ◽  
The Tropics ◽  
Emission Tracers

Abstract. The impact of different boundary layer source regions in Asia on the chemical composition of the Asian monsoon anticyclone, considering its intraseasonal variability in 2012, is analysed by simulations of the Chemical Lagrangian Model of the Stratosphere (CLaMS) using artificial emission tracers. The horizontal distribution of simulated CO, O3, and artificial emission tracers for India/China are in good agreement with patterns found in satellite measurements of O3 and CO by the Aura Microwave Limb Sounder (MLS). Using in addition, correlations of artificial emission tracers with potential vorticity demonstrates that the emission tracer for India/China is a very good proxy for spatial distribution of trace gases within the Asian monsoon anticyclone. The Asian monsoon anticyclone constitutes a horizontal transport barrier for emission tracers and is highly variable in location and shape. From the end of June to early August, a northward movement of the anticyclone and, during September, a strong broadening of the spatial distribution of the emission tracer for India/China towards the tropics are found. In addition to the change of the location of the anticyclone, the contribution of different boundary source regions to the composition of the Asian monsoon anticyclone in the upper troposphere strongly depends on its intraseasonal variability and is therefore more complex than hitherto believed. The largest contributions to the composition of the air mass in the anticyclone are found from northern India and Southeast Asia at a potential temperature of 380 K. In the early (mid-June to mid-July) and late (September) period of the 2012 monsoon season, contributions of emissions from Southeast Asia are highest; in the intervening period (early August), emissions from northern India have the largest impact. Our findings show that the temporal variation of the contribution of different convective regions is imprinted in the chemical composition of the Asian monsoon anticyclone. Air masses originating in Southeast Asia are found both within and outside of the Asian monsoon anticyclone because these air masses experience, in addition to transport within the anticyclone, upward transport at the southeastern flank of the anticyclone and in the tropics. Subsequently, isentropic poleward transport of these air masses occurs at around 380 K with the result that the extratropical lowermost stratosphere in the Northern Hemisphere is flooded by the end of September with air masses originating in Southeast Asia. Even after the breakup of the anticyclonic circulation (around the end of September), significant contributions of air masses originating in India/China are still found in the upper troposphere over Asia. Our results demonstrate that emissions from India, China, and Southeast Asia have a significant impact on the chemical composition of the lowermost stratosphere of the Northern Hemisphere, in particular at the end of the monsoon season in September/October 2012.

scholarly journals Using different assumptions of aerosol mixing state and chemical composition to predict CCN concentrations based on field measurements in urban Beijing

2018 ◽  
Vol 18 (9) ◽  
pp. 6907-6921 ◽  
Author(s):  
Jingye Ren ◽  
Fang Zhang ◽  
Yuying Wang ◽  
Don Collins ◽  
Xinxin Fan ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Black Carbon ◽  
Cloud Condensation Nuclei ◽  
Field Measurements ◽  
Minor Role ◽  
Mixing State ◽  
Mixing Processes ◽  
Size Dependent ◽  
Aerosol Mixing State ◽  
Aerosol Chemical Composition

Abstract. Understanding the impacts of aerosol chemical composition and mixing state on cloud condensation nuclei (CCN) activity in polluted areas is crucial for accurately predicting CCN number concentrations (NCCN). In this study, we predict NCCN under five assumed schemes of aerosol chemical composition and mixing state based on field measurements in Beijing during the winter of 2016. Our results show that the best closure is achieved with the assumption of size dependent chemical composition for which sulfate, nitrate, secondary organic aerosols, and aged black carbon are internally mixed with each other but externally mixed with primary organic aerosol and fresh black carbon (external–internal size-resolved, abbreviated as EI–SR scheme). The resulting ratios of predicted-to-measured NCCN (RCCN_p∕m) were 0.90 – 0.98 under both clean and polluted conditions. Assumption of an internal mixture and bulk chemical composition (INT–BK scheme) shows good closure with RCCN_p∕m of 1.0 –1.16 under clean conditions, implying that it is adequate for CCN prediction in continental clean regions. On polluted days, assuming the aerosol is internally mixed and has a chemical composition that is size dependent (INT–SR scheme) achieves better closure than the INT–BK scheme due to the heterogeneity and variation in particle composition at different sizes. The improved closure achieved using the EI–SR and INT–SR assumptions highlight the importance of measuring size-resolved chemical composition for CCN predictions in polluted regions. NCCN is significantly underestimated (with RCCN_p∕m of 0.66 – 0.75) when using the schemes of external mixtures with bulk (EXT–BK scheme) or size-resolved composition (EXT–SR scheme), implying that primary particles experience rapid aging and physical mixing processes in urban Beijing. However, our results show that the aerosol mixing state plays a minor role in CCN prediction when the κorg exceeds 0.1.

Sign in / Sign up

Export Citation Format

Share Document