Black Carbon Aerosols Research Articles

Provenance of Aerosol Black Carbon over Northeast Indian Ocean and South China Sea and Implications for Oceanic Black Carbon Cycling.

Aerosol black carbon (BC) is a short-lived climate pollutant. The poorly constrained provenance of tropical marine aerosol BC hinders the mechanistic understanding of extreme climate events and oceanic carbon cycling. Here, we collected PM2.5 samples during research cruise NORC2016-10 through South China Sea (SCS) and Northeast Indian Ocean (NEIO) and measured the dual-carbon isotope compositions (δ13C-Δ14C) of BC using hydrogen pyrolysis technique. Aerosol BC exhibits six different δ13C-Δ14C isotopic spaces (i.e., isotope provinces). Liquid fossil fuel combustion, from shipping emissions and adjacent land, is the predominant source of BC over isotope provinces "SCS close to Chinese Mainland" (53.5%), "Malacca Strait" (53.4%), and "Open NEIO" (40.7%). C3 biomass burning is the major contributor to BC over isotope provinces "NEIO close to Southeast Asia" (55.8%), "Open NEIO" (41.3%), and "Open SCS" (40.0%). Coal combustion and C4 biomass burning show higher contributions to BC over "Sunda Strait" and "Open SCS" than the others. Overall, NEIO near the Bay of Bengal, Malacca Strait, and north SCS are three hot spots of fossil fuel-derived BC; the first two areas are also hot spots of biomass-derived BC. The comparable δ13C-Δ14C between BC in aerosol and dissolved BC in surface seawater may suggest atmospheric BC deposition as a potential source of oceanic dissolved BC.

A Decadal, Temporal and Seasonal Variation of Black Carbon Aerosol at High Altitude Region of Ooty, Tamil Nadu, India

Climate change is accelerating at an unprecedented pace due to escalating greenhouse gas emissions, emphasizing the urgency of understanding its drivers. Aerosols present in the atmosphere, play an significant role in the intricate climate system. In this study, we examine the temporal and seasonal trends of black carbon aerosol, a significant contributor to warming, in the high-altitude locale of Ooty, Tamil Nadu, India. Utilizing the Aethalometer instrument, this research presents a comprehensive analysis of black carbon concentrations over a decade (2013-2023). Observations reveal distinct patterns, with higher concentrations during certain months and seasons. Specifically, April consistently exhibited the highest concentrations, while the monsoon season recorded the lowest. The exceptional decline in 2020, attributed to COVID-19 lockdown measures, highlights the significant role of anthropogenic activities.
 These findings underscore the significance of proactive black carbon monitoring in regions like Ooty. The study contributes valuable insights into the complex interplay between black carbon aerosols and climate systems, especially in high-altitude environments. It underscores the need for continued research to comprehensively understand black carbon's implications on local and global climate dynamics. In conclusion, this research establishes a foundation for grasping the intricate dynamics of black carbon aerosols in Ooty and serves as a stepping stone for broader insights into their role in shaping climate patterns and effects. By addressing these critical knowledge gaps, we can better inform mitigation strategies and policy decisions aimed at tackling climate change.

Measurement report: Inland ship emissions and their contribution to NOx and ultrafine particle concentrations at the Rhine

Abstract. Emission plumes of around 4700 ship passages were detected between March 2021 and June 2022 in the Upper Rhine Valley in Worms, Germany. In combination with ship-related data recorded via the automatic identification system (AIS), the plume composition of individuals ships was analyzed, and it was possible to quantify their contribution to the overall emission load. To obtain an integral picture of inland ship emissions, nitrogen oxide (NOx = NO + NO2) and carbon dioxide (CO2) measurements in the gas phase were combined with detailed particle-phase measurements including particle number concentration (PNC), particle size distribution (PSD) from 5 nm to 10 µm, particulate matter (PM1 and PM2.5), ultrafine particle fraction (UFP, diameter < 100 nm) and aerosol black carbon (BC). One measuring station was located inside a bridge directly above the navigation channel and was especially helpful in deriving emission factors under real-world driving conditions for the fleet on the Upper Rhine. The other station was situated on a riverbank at about 40 m distance to the shipping lane and was thus representative of the exposure of people working or living close to the Rhine. Inland ships contributed 1.2 µg m−3 or 7 % on average to the local nitrogen dioxide (NO2) concentration at the bridge above the shipping lane. NOx concentrations were increased by 10.5 µg m−3 (50 %), PNC by 800 cm−3 (10 %), PM1 by 0.4 µg m−3 (4 %) and BC by 0.15 µg m−3 (15 %). On the riverbank a NOx increase of 1.6 µg m−3 (8 %) and an NO2 increase of 0.4 µg m−3 (3 %) were observed. More than 75 % of emitted particles were found in the UFP range with a geometric mean particle diameter of 52±23 nm. Calculated emission factors (25–75 percentiles) were 26–44 g kg−1 of fuel for NOx, 1.9–3.2 g kg−1 for NO2, 0.3–0.7 g kg−1 for BC, 0.9–2.3 g kg−1 for PM1 and (1–3) × 1015 kg−1 for PNC, with a large variability observed from ship to ship. Relating these values to ship-specific parameters revealed the importance of engine characteristics, i.e., vessels using old motors with low revolutions per minute (rpm) caused comparably high emission factors for both NOx and PNC. A comparison with emission regulation limits set by the Central Commission for the Navigation of the Rhine (CCNR) and the European Union (EU) showed that – within the uncertainty of our calculation method – mean energy-dependent emission factors under real-driving conditions were slightly exceeding those under controlled laboratory conditions. The results from this study underline the importance of long-term measurements with high temporal resolution to reliably estimate the contribution of inland shipping to air pollution in cities along heavy traffic waterways and to monitor a potential future emission reduction when modernizing the fleet.

Aging of biomass burning emissions in the Indo-Gangetic Plain outflow: Implications for black carbon light-absorption enhancement

Recent studies worldwide have demonstrated that coating on atmospheric black carbon (BC) aerosol enhances its absorption potential. However, studies quantifying the light-absorption enhancement (Eabs) of BC are extremely limited over the Indian region. The northwestern Indo-Gangetic Plain (IGP) region witnesses annual episodes of substantial crop-residue burning during the post-monsoon season (PoMS), which has been attracting wide attention due to its impact on regional air quality and aerosol characteristics. Chemical aging of these biomass burning (BB) emissions occurs during its long-range transport across the IGP by the weak westerlies, and such atmospheric processing affects their chemical, optical, and radiative properties over downwind locations. This study examines the impact of atmospheric aging of biomass burning emissions on BC light-absorption enhancement (Eabs) using extensive, simultaneous measurements of single particle refractory BC and near-real-time mass spectrometry measurements of non-refractory submicron aerosols from an IGP outflow site. It was observed that organics were the dominant submicron aerosol species, and positive matrix factorization analysis of the organics mass spectra suggested that a large fraction of organics (64%) was secondary in nature. The BC particles in the IGP outflow (mass median diameter ∼ 0.18 ± 0.01 μm) were found to be thickly coated with volume-weighted bulk relative coating thickness in the range of 1.3–1.8. The evolution of biomass-burning organic aerosols (BBOA) indicated the presence of significant amounts of aged BBOA during the PoMS. Further, the oxidation products from the evolution of BB emissions contributed to enhanced coatings (∼ 30–70%) on BC. Mie core-shell theory calculations were then used to assess the changes in BC light absorption characteristics due to the coating of non-refractory mass on its cores. It was found that thick coatings on BC led to significant light-absorption enhancement (Eabs) (bulk Eabs in the range of 1.14–1.94 at 550 nm, depending on the extent of coating). Increased Eabs values of ≥1.8 were seen when the coating on BC exceeded 60% of its core size. The modeled bulk Eabs at 550 nm depicted a better association with highly oxidized secondary organic aerosols (SOA) than sulfate among the secondary aerosol species, suggesting an SOA-dominant regime. The present findings suggest that the critical impact of the aging of BC and co-emitted species from widespread BB emissions in the IGP outflow should be considered when evaluating the regional radiative implications.

Measuring the Emission Changes and Meteorological Dependence of Source‐Specific BC Aerosol Using Factor Analysis Coupled With Machine Learning

AbstractReducing ambient black carbon (BC) relies on the targeted control of anthropogenic emissions. Measuring emission changes in source‐specific BC aerosol is essential to assess the effectiveness of regulatory policies but is difficult due to the presence of meteorology and multiple co‐existing emissions. Herein, we propose a data‐driven approach, combining dispersion‐normalized factor analysis (DN‐PMF) with a machine learning weather adjustment (deweathering) technique, to decompose ambient BC into source emissions and meteorological drivers. Six refined BC sources were extracted from the factor analysis of aethalometer multi‐wavelength BC and concurrent observational datasets. In addition to the widely reported dominant sources, such as vehicular emissions (VE) and coal/biomass burning (BB), a discernible port and shipping emission source were identified with potential impacts on coastal air quality. The source‐specific BC showed abrupt changes in response to interventions (e.g., holidays) after separating weather‐related confounders. Significant reductions in deweathered coal and BB, VE, and local dust verified the effectiveness of policies, such as clean winter‐heating and support for the Clean Air Actions. As revealed by a post‐hoc model explanation technique, the evolution of the boundary layer was the predominant meteorological driver exerting the opposite impact on local sources with respect to distant regional‐wide sources, that is, the port and shipping emissions.

A comprehensive reappraisal of long-term aerosol characteristics, trends, and variability in Asia

Abstract. Changes in aerosol loadings and properties are important for the understanding of atmospheric environment and climate change. This study investigates the characteristics and long-term trends of aerosols of different sizes and types in Asia from 2000 to 2020 by considering multi-source aerosol data and novel analysis methods and perspectives, all of which provides the groundwork for promoting the acquisition of new discoveries that are different from the past. The geometric mean aggregation method is applied, and serial autocorrelation is considered to avoid the overestimation of trend significance. Among regions in Asia, high values of aerosol optical depth (AOD) are mainly concentrated in East Asia (EA) and South Asia (SA) and are closely related to the population density. The AOD in EA showed the most significant negative trend, with a value of -5.28×10-4 per year, mainly owing to decreases in organic carbon (OC), black carbon (BC), and dust aerosols. It is also worth noting that this observed large-scale decrease in OC and BC is a unique and significant phenomenon to region of EA and mainly around China. In contrast, the aerosol concentrations in SA generally show a positive trend, with an increased value of AOD of 1.25 × 10−3 per year. This increase is mainly due to large emissions of fine-mode aerosols, such as OC and sulfate aerosol. Additionally, the high aerosol loading in northern SA has a lower AOD variability when compared with that of East China Plain, revealing a relatively more persistent air pollution situation. Over the whole region of Asia, the characteristics of the percentage changes in different types of AOD are seen in the increases in BC (6.23 %) and OC (17.09 %) AOD, together with a decrease in dust (−5.51 %), sulfate (−3.07 %), and sea salt (−9.80 %) AOD. Except for anthropogenic emissions, the large increase in the percentage of OC is also due to wildfires found in northern Asia in the summer, whereas the differently sized AOD only shows slight changes in Asia in that small-sized AOD decreases (−3.34 %) and that the total AOD did not show a significant change. This suggests that, from a trend perspective, decreases in aerosol in recent years have mostly been offsetting earlier increases in the anthropogenic emissions over Asia. To summarize, the above findings analyse the comprehensive characteristics of aerosol distributions and reappraise the long-term trends of different aerosol parameters, which will greatly enhance the understanding of regional and global aerosol environment and climatology, in addition to filling the gaps and breaking through the limitations of past knowledge.

Satellite (GOSAT-2 CAI-2) retrieval and surface (ARFINET) observations of aerosol black carbon over India

Abstract. Light-absorbing black carbon (BC) aerosols strongly affect Earth's radiation budget and climate. This paper presents satellite retrieval of BC over India based on observations from the Cloud and Aerosol Imager-2 (CAI-2) on board the Greenhouse gases Observing Satellite-2 (GOSAT-2). To evaluate and validate the satellite retrievals, near-surface BC mass concentrations measured across the Aerosol Radiative Forcing over India NETwork (ARFINET) of aerosol observatories are used. Then the findings are extended to elucidate global BC features. The analysis reveals that this satellite retrieval clearly demonstrates the regional and seasonal features of BC over the Indian region, similarly to those recorded by surface observations. Validation and closure studies between the two datasets show RMSE < 1 and absolute difference below 2 µg m−3 for > 60 % of simultaneous observations, exhibiting good associations for December, January, and February (R of approximately 0.73) and March, April, and May (R approx. 0.76). Over the hotspot regions of India, satellite retrievals show a soot volume fraction of approx. 5 %, columnar single-scattering albedo of approx. 0.8, and BC column optical depth of approx. 0.1 during times of the highest BC loading, which are comparable to other in situ and satellite measurements. In terms of global spatiotemporal variation, satellite retrievals show higher BC occurring mostly in areas where biomass burning is intense. Overall, this study highlights the effectiveness of satellite retrieval of BC, which can be used effectively for the regular monitoring of BC loading attributable to vehicular, industrial, or biomass burning activities.

Airborne investigation of black carbon interaction with low-level, persistent, mixed-phase clouds in the Arctic summer

Abstract. Aerosol–cloud interaction is considered one of the largest sources of uncertainty in radiative forcing estimations. To better understand the role of black carbon (BC) aerosol as a cloud nucleus and the impact of clouds on its vertical distribution in the Arctic, we report airborne in situ measurements of BC particles in the European Arctic near Svalbard during the “Arctic CLoud Observations Using airborne measurements during polar Day” (ACLOUD) campaign held in the summer of 2017. BC was measured with a single-particle soot photometer aboard the Polar 6 research aircraft from the lowest atmospheric layer up to approximately 3500 m a.s.l (metres above sea level). During in-cloud flight transects, BC particles contained in liquid droplets (BC residuals) were sampled through a counterflow virtual impactor (CVI) inlet. Four flights, conducted in the presence of low-level, surface-coupled, inside-inversion, and mixed-phase clouds over sea ice, were selected to address the variability in BC above, below, and within the cloud layer. First, the increase in size and coating thickness of BC particles from the free troposphere to the cloud-dominated boundary layer confirmed that ground observations were not representative of upper atmospheric layers. Second, although only 1 % of liquid droplets contained a BC particle, the higher number concentration of BC residuals than BC particles sampled below cloud indicated that the totality of below-cloud BC was activated by nucleation scavenging but also that alternative scavenging processes such as the activation of free-tropospheric BC at the cloud top might occur. Third, the efficient exchange of aerosol particles at cloud bottom was confirmed by the similarity of the size distribution of BC residuals and BC particles sampled below cloud. Last, the increase in the BC residual number concentration (+31 %) and geometric mean diameter (+38 %) from the cloud top to the cloud bottom and the absolute enrichment in larger BC residuals compared with outside of the cloud supported the hypothesis of concomitant scavenging mechanisms but also suggested the formation of BC agglomerates caused by cloud processing. The vertical evolution of BC properties from inside the cloud and below the cloud indicated an efficient aerosol exchange at cloud bottom, which might include activation, cloud processing, and sub-cloud release of processed BC agglomerates. In the case of persistent low-level Arctic clouds, this cycle may reiterate multiple times, adding an additional degree of complexity to the understanding of cloud processing of BC particles in the Arctic.

Dry Deposition of Hydrophilic Black Carbon Aerosols in China

Dry Deposition of Hydrophilic Black Carbon Aerosols in China

Polarized radiative transfer in heterogeneous black carbon aerosol particles

Research on the polarized radiative transfer of black carbon (BC) aerosol particles in the atmosphere is of great help for real-time monitoring of climate change. Existing studies generally have not considered the effects of complex morphology and heterogeneity of BC aerosol particles on the polarized radiative transfer. BC aggregates with different coating shapes are established in accordance with the heterogeneous particle superposition model. The vector Monte Carlo method (VMCM) combined with Discrete dipole approximation (DDA) method proposed in this work offers a general method for calculating the polarized radiative transfer of heterogeneous BC aerosol particles with arbitrary coating shapes. The effects of sulfate coating volumes and shapes, and wavelengths on the Stokes parameters, the degree of polarization P, transmissivity T, and reflectivity R of atmosphere containing heterogeneous BC aerosol particles are discussed. The results show that the simplification of coating shape underestimates the Stokes parameter I and the degree of polarization P of the top of atmosphere and overestimates the I of the bottom of atmosphere. The simplification models of coating shape result in a maximum underestimation of the peak I by ∼26% at the bottom of atmosphere and a maximum overestimation of the peak I by ∼8% at the top of atmosphere, relative to that of the irregular coating models. Moreover, coating volumes and wavelengths also significantly affect the polarized radiative transfer characteristics. Thus, the influence of these factors should be considered for the calculation of polarized radiative transfer of heterogeneous BC aerosol particles in the atmosphere.

Evaluation of a method to quantify the number concentrations of submicron water-insoluble aerosol particles based on filter sampling and complex forward-scattering amplitude measurements

Water-insoluble aerosol particles (WIAPs), such as black carbon (BC), mineral dust, and primary biological aerosol particles (PBAPs), affect climate through their interaction with radiation and clouds. However, with the exception of BC, methods to identify WIAP types and quantify their number concentrations are limited. Here, we evaluated a method that has been recently developed to measure the number concentrations of submicron WIAPs based on atmospheric aerosol measurements at an urban site in Nagoya, Japan. In this method, atmospheric aerosol particles are collected on a filter and dispersed in water. Then, the complex forward-scattering amplitudes of individual particles are measured. This complex parameter reflects the complex refractive index, volume, and shape of each measured particle, enabling the characterization of these physical properties from the signals. The WIAPs were classified as BC-like, dust-like, and PBAP-like particles based on their complex amplitude data. The number concentrations of BC-like particles were strongly correlated with those of refractory BC particles measured by a Single Particle Soot Photometer. BC-like and dust-like particles dominated the population of the submicron WIAPs, which was also confirmed using electron microscopy and Wideband Integrated Bioaerosol Sensor observations. Under the observed atmospheric conditions, the number concentrations of WIAPs were measured with their dispersion efficiency from a filter to water of approximately 50%. These results indicate that our method based on filter sampling and complex forward-scattering amplitude measurements has the potential to become a new technique for quantifying the spatio-temporal distributions of WIAPs.

Long‐Term Observations of Levoglucosan in Arctic Aerosols Reveal Its Biomass Burning Source and Implication on Radiative Forcing

AbstractBiomass burning (BB) has a significant influence on the Arctic environment. Here, we determined the atmospheric levels of BB‐specific tracer compounds such as levoglucosan (Lev), galactosan (Gan), and mannosan (Man) in Arctic aerosols during 2010–2018. The average concentrations of Lev during the study period ranged between 0.43 and 4.15 ng m−3. Both Lev/Man (0–30) and Man/Gan (0–3) ratios further suggested their origin from softwood/hardwood burning. The North Atlantic Oscillation (NAO) was the main driver of the Lev variability during the study period and Lev could be advected to Arctic air during the NAO was in a positive phase. Based upon the levels of Lev, black carbon (BC) generated from BB was estimated, and the corresponding radiative forcing was then calculated by Santa Barbara DISORT Atmospheric Radiative Transfer. BC has a potential warming effect in the atmosphere (+4.28 W/m2) while shows a cooling effect on the surface, which is equivalent to a large volcanic eruption (−3 W/m2). Since climate change is expected to intensify BB around the Arctic, such BC aerosols should be considered in future climate model projections.

Aerosols heat up the Himalayan climate

The impact of aerosols, especially the absorbing aerosols, in the Himalayan region is important for climate. We closely examine ground-based high-quality observations of aerosol characteristics including radiative forcing from several locations in the Indo-Gangetic Plain (IGP), the Himalayan foothills and the Tibetan Plateau, relatively poorly studied regions with several sensitive ecosystems of global importance, as well as highly vulnerable large populations. This paper presents a state-of-the-art treatment of the warming that arises from these particles, using a combination of new measurements and modeling techniques. This is a first-time analysis of its kind, including ground-based observations, satellite data, and model simulations, which reveals that the aerosol radiative forcing efficiency (ARFE) in the atmosphere is clearly high over the IGP and the Himalayan foothills (80–135 Wm−2 per unit aerosol optical depth (AOD)), with values being greater at higher elevations. AOD is >0.30 and single scattering albedo (SSA) is ∼0.90 throughout the year over this region. The mean ARFE is 2–4 times higher here than over other polluted sites in South and East Asia, owing to higher AOD and aerosol absorption (i.e., lower SSA). Further, the observed annual mean aerosol-induced atmospheric heating rates (0.5–0.8 Kelvin/day), which are significantly higher than previously reported values for the region, imply that the aerosols alone could account for >50 % of the total warming (aerosols + greenhouse gases) of the lower atmosphere and surface over this region. We demonstrate that the current state-of-the-art models used in climate assessments significantly underestimate aerosol-induced heating, efficiency and warming over the Hindu Kush – Himalaya – Tibetan Plateau (HKHTP) region, indicating a need for a more realistic representation of aerosol properties, especially of black carbon and other aerosols. The significant, regionally coherent aerosol-induced warming that we observe in the high altitudes of the region, is a significant factor contributing to increasing air temperature, observed accelerated retreat of the glaciers, and changes in the hydrological cycle and precipitation patterns over this region. Thus, aerosols are heating up the Himalayan climate, and will remain a key factor driving climate change over the region.

Sources, transport pathways and radiative effects of BC aerosol during 2018–2020 at a receptor site in the eastern Indo-Gangetic Plain

This study reports black carbon (BC) characteristics and climate effects for a 22-month period during 2018–2020 at a receptor location in the eastern Indo-Gangetic Plains (IGP). The overall averaged BC mass concentration was 7.8 ± 4.7 μg m−3, and the nighttime average (9.1 ± 6.1 μg m−3) was nearly double that of the daytime (5.8 ± 3.5 μg m−3). BC was most enhanced during winter, with mean concentration (14.3 ± 3.8 μg m−3) higher by 4 times as compared to summer. A two-component mixing model, frequency distribution of the Angstrom exponent, and a simultaneous increase in brown carbon (BrC) absorption coefficient suggested that this enhancement was mostly due to the biomass burning (BB) fraction of BC. CALIPSO-derived products showed that the extinction coefficient was highest at 0.62 ± 0.31 km−1 in winter and lowest at 0.12 ± 0.05 km−1 in summer. Backscatter plots and particle depolarization ratios indicated presence of spherical dust particles during summer and smoke plumes during post-monsoon and winter. Concentration-weighted trajectories (CWTs) helped in quantifying significant contributions of the IGP outflow to BC, BC-BB and BrC absorption. Finally, a large direct radiative forcing of the atmosphere by BC (37 ± 22 W m−2) was estimated via the radiative transfer model SBDART, with an associated atmospheric heating rate of 1.02 K d−1.

The Time Scales of Climate Responses to Carbon Dioxide and Aerosols

Abstract The climate system responds to changes in the amount of atmospheric greenhouse gases or aerosols through rapid processes, triggered within hours and days, and through slower processes, where the full response may only be seen after centuries. In this paper, we aim to elucidate the mechanisms operating on time scales of hours to years to better understand the response of key climate quantities such as energy fluxes, temperature, and precipitation after a sudden increase in either carbon dioxide (CO2), black carbon (BC), or sulfate (SO4) aerosols. The results are based on idealized simulations from six global climate models. We find that the effect of changing ocean temperatures kicks in after a couple of months. Rapid precipitation reductions start occurring instantly and are established after just a few days. For BC, they constitute most of the equilibrium response. For CO2 and SO4, the magnitude of the precipitation response gradually increases as surface warming/cooling evolves, and for CO2, the sign of the response changes from negative to positive after 2 years. Rapid cloud adjustments are typically established within the first 24 h, and while the magnitude of cloud feedbacks for CO2 and SO4 increases over time, the geographical pattern of the equilibrium cloud change is present already after the first year. While there are model differences, our work underscores the overall similarity of the major time-varying processes and responses simulated by current global models and hence the robustness of key features of simulated responses to historical and future anthropogenic forcing. Significance Statement How does the climate system respond to a change in the amount of atmospheric greenhouse gases or aerosols? Some processes are rapid, responding within hours and days. Others are slow, and the full response to a forcing of the climate may only be seen after centuries. In this paper, we use six global climate models to investigate the time scales of climate responses to carbon dioxide, black carbon, and sulfate, focusing on key climate quantities, such as temperature, precipitation, and clouds. While there are ample model differences, our work underscores the overall similarity of the major time-varying processes and responses simulated by current global models and hence the robustness of key features of simulated responses to historical and future anthropogenic forcing.

Burning of Municipal Solid Waste: An Invitation for Aerosol Black Carbon and PM2.5 Over Mid–Sized City in India

Waste management is the main concern of most cities in developing countries. The proper procedure is needed to reduce Municipal solid waste, that’s why burning is the cheaper way to decrease solid waste. The main aim of this study is to assess the concentration of Black Carbon and PM2.5 during the MSW burning sites in Jamshedpur. The continuous measurement was taken during the burning period in three phases at Industrial, Urban, and Rural waste burning sites having respective average BC concentrations observed as 145 ± 46, 101 ± 33 & 95 ± 33 μg m−3, and PM2.5 as 1391 ± 358, 998 ± 319, 957 ± 313 μg m−3. BC and PM2.5 concentrations show significant diurnal variations with maximum average concentration at the midnight phase due to large temperature fluctuation (lower mixed layer height) in the atmosphere. This evaluation during burning period exceeds regular day estimates by around 5–6 times. The rate distinction of BC by the Aethalometer model indicates that source apportionment of BC is more sensitive in assessing BCBB (biomass burning) with an average fraction of 82% at 880 nm because waste trash burning in the dump yard was mostly solid. Pearson correlation analysis shows strong correlations between BC and PM2.5 concentration that is primarily attributable to well-known nearby sources such as vehicular emissions.

Seasonal transition of Black carbon aerosols over Qinghai-Tibet Plateau: Simulations with WRF-Chem

Black carbon (BC) particles over the Qinghai-Tibet Plateau (Q-TP), whether suspended in the air or deposited on snow, can affect snow melt and accelerate glacier retreat. Since BC over the Q-TP may originate from different regions, it is necessary to understand the transport mechanism of BC and then provide concentrations and spatial-temporal distributions of BC over Q-TP, in order to study its radiative and climatic effects. In this study, Weather Research and Forecasting model with Chemistry (WRF-Chem), with MIX emission inventory (a mosaic Asian anthropogenic emission inventory for the MICS-Asia and the HTAP projects), was used to study the BC transport from South Asia, one of the major BC source regions, to Q-TP in April (pre-monsoon season), July (summer monsoon season) and December (winter monsoon season). The model's ability to simulate the BC transport from South Asia to the Q-TP was firstly evaluate using various reanalysis data, including 2 m temperature, precipitation, 10 m wind speed and direction and BC concentration at surface. The simulated meteorological fields and seasonal distribution and variation of BC are generally in good agreement with reanalysis data. The model showed good performance in simulating transport of BC as well. Our study showed that during pre-monsoon season, BC aerosols accumulated in the foothills of the Himalayas and were transported to southern Q-TP and even Southeast Asia via dry and wet deposition and westerly winds below 200hpa. Although the cyclonic airflow, which was favorable to transport, prevailed in South Asia, slight BC aerosols would be transported to Q-TP through wet deposition due to the efficient wet scavenging by abundant precipitation during summer monsoon season. During winter monsoon season, the prevailing westerly winds at 500hpa would transport BC aerosols from South Asia to Q-TP by dry deposition. A sensitivity simulation using PKU emission inventory (Peking University's global BC emission inventory) was then conducted to investigate the impact of different emission inventory on the modeling results. It is shown that the simulations using the different BC emission inventories overall did not have significant impacts on spatial distributions of surface concentration and column burden during three studies seasons. However, the simulated BC concentrations and burden based on PKU were overall higher than that based on MIX, that is, main differences were found in the southern part of Q-TP (i.e. adjacent to South Asia), especially during pre-monsoon and winter monsoon seasons. The differences of mean BC surface concentration ranging from 0.1 to 1 μg/m3, and burden ranging from 0.1 to 1 mg/m2 due to both higher dry and wet deposition (0.1–2 μg/m2/s for dry deposition flux, and 0.1–3 μg/m2/s for wet deposition flux) during pre-monsoon. During winter monsoon seasons, relatively large differences (0–3 μg/m3 for concentration, and 0–2 mg/m2 for burden, and 0.1–3 μg/m2/s for dry deposition flux) were found in southern Q-TP.

The Simulated Source Apportionment of Light Absorbing Aerosols: Effects of Microphysical Properties of Partially‐Coated Black Carbon

AbstractBiomass burning (BB) fractions estimated with the aethalometer model differ from 0 even for pure aerosols from fossil fuel (FF) combustion. We used black carbon (BC) aerosols partially‐coated with non‐absorbing materials to represent typical FF aerosols, and the BB fractions were determined with the aethalometer model. Thus, the estimated BB fractions are the fractions that FF aerosols are incorrectly attributed to BB aerosols. The BC morphology and mixing state have significant effects on the estimation of BB fractions. For freshly emitted BC, the BB fractions do not deviate significantly from 0, and the BB fraction is generally in the range of −1%–10% based on an FF absorption Ångström exponent (AAE) of 1 and a BB AAE of 2. The BB fraction deviates substantially from 0 when BC becomes compact and is coated. The absolute values of the deviations sometimes can be close to 100% for heavily coated BC. The BB fraction is generally greater than 0 for fluffy BC while compact BC generally exhibits a negative BB fraction. The BB fractions of partially‐coated BC are very sensitive to the size distribution and coating ratio, which is consistent with the results of the core‐shell sphere model. We have also performed a series of studies with different configurations for BC morphologies, coating ratios, and mixing states, which show the variations of the estimated BB fractions with atmospheric aging. We also explain the reasons for the uncertainties in the BB fraction estimates and provide suggestions for using different AAE pairs.

Microphysical characteristics of black carbon from various emission sources

The complex microphysical characteristics of black carbon aerosol (BC) results in large uncertainties in the evaluation of BC's climatic and environmental effects. In this study, the microphysical properties were investigated in fresh BC emitted from traffic sources (gasoline vehicle and diesel) and aged BC emitted from solid fuel burning sources (coal, cotton stem, rice stem and mulberry). For the BC core size distribution, the number size distribution of traffic sources peaks at a lower value than that of aged solid fuel burning sources. Although traffic sources emit a greater number of small BC cores, traffic sources could also emit BC aerosols with large BC cores (diameter larger than 400 nm) not found in solid fuel sources. The coating thickness of BC from traffic sources is significantly lower than that of aged BC from solid fuel sources. Such differences in size distribution and coating thickness cause large variations in other microphysical parameters, such as light absorption and hygroscopicity, for these two types of BC. The mass absorption cross section (MAC) of aged BC from cotton stems reached 11.69 m2/g, nearly 2 times higher than the MAC (6.08 m2/g) of fresh BC from gasoline vehicles. The hygroscopicity of aged BC from solid fuel burning is also much higher than that of fresh BC from traffic. The critical supersaturation needed to activate BC to become cloud droplets is 0.03% for the former and 0.42% for the latter. This study reports the BC emission characteristics of traffic sources and emphasizes the large property difference between fresh traffic emission BC and aged solid fuel burning BC. The microphysical properties of BC should be carefully considered to better resolve BC concentrations and optical properties in climatic models.

Mutual response hypothesis between surface temperature and aerosol (BC and non-BC) mass concentration observed in an urban environment

The mutual response between near surface aerosol concentration and surface temperature works in a complicated manner. A recent study has introduced a hypothesis of mutual response between surface temperature and near surface black carbon (BC) mass concentration which states that ‘more fall in morning hour surface temperature (T) contribute to the enhancement of BC fumigation peak after the sunrise which positively impacts the extra rise in mid-day temperature over a region during the day time’. Morning hour surface temperature is proportionally linked with the strength of the night time near surface temperature inversion which contributes to the enhancement of the fumigation peak of BC aerosols after the sunrise and the enhanced fumigation peak can impact the degree of the mid-day surface temperature rise by influencing the instantaneous heating. However, it didn't mention the role of non-BC aerosols. Further, the hypothesis was drawn based on the co-located ground-based observations of surface temperature and BC concentration at a rural location of peninsular India. Though, it was mentioned that the hypothesis can be tested independently of locations, but was not thoroughly validated for an urban environment where the loading of both BC and non-BC aerosols are high. In this context, the first objective of the present work is to methodically test the BC –T hypothesis over an Indian metropolitan city, Kolkata, using the suite of measurements obtained from Kolkata Camp Observatory of NARL (KCON) along with other supporting data. In addition, the validity of the hypothesis for the non-BC fraction of PM2.5 aerosols over the same location is also tested. Besides ascertaining the above-mentioned hypothesis over an urban location, it is found that the enhancement of non-BC PM2.5 aerosols peak after the sunrise can negatively influences the mid-day temperature rise over a region during the day time.