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Fog holes were reported over cities of the Indo‐Gangetic plains of India, which were attributed to the urban heat island (UHI) effect. The present study reports the observational evidence of fog holes over rural area using satellite and ground observations. Delayed onset and early dissipation of fog is observed over the holes. Numerical simulations demonstrate that aerosol‐radiation interaction (ARI) leads to fog holes over both urban and rural regions. The anthropogenic aerosols and associated ARI dominate the UHI effect over the urban fog holes, while the aerosol absorption due to ARI mainly controls the rural fog holes. Turning off aerosol absorption causes ∼ 2 hours delay in the fog dissipation over urban area, whereas it yields persistent fog over rural area under saturated environment. An enhancement of soluble Aitken black carbon over the fog holes indicates the importance of aging process during fog dissipation. Plain Language Summary: This study reports the occurrence of fog holes over rural and urban regions and investigates the mechanism behind the formation of fog holes using DM‐Chem. The main reason behind the fog hole formation over Indo‐Gangetic plains is the absorption of radiation by the total black carbon aerosols. The absence of the absorbing component of aerosol‐radiation interaction leads to the occurrence of fog over both the urban and rural hole areas. The fog hole areas are correlated with an enhanced formation of small sized soluble black carbon aerosols. These findings suggest the need for detailed aging processes of carbonaceous particles in atmospheric models. Key Points: Fog holes over the rural regions reported for the first timeDelayed onset and early dissipation of fog over the hole regionsAerosol radiation effect (absorption) dominates over the urban heat island effect [ABSTRACT FROM AUTHOR]

In this study, we present the indoor Black Carbon (BC) measurements with the help of Aethalometer (AE‐33) from various sites in Eastern India in a typical kitchen room situated in a rural area. Analysis was done on how various cooking activities performed in the home affected the indoor level of BC. The activities resulting in elevated indoor concentrations included three different periods of cooking breakfast, lunch, and dinner with three different kinds of kitchen structures open, semi‐open and closed kitchen. Close kitchen resulted in the highest BC concentrations, while open kitchen resulted in the lowest level. The burning of low‐grade fuels resulted in the largest increases in indoor BC concentration. We calculated the average BC concentrations for three distinct kitchens, with open kitchens emitting 260.14 μgm−3, semi‐open kitchens emitting 441.14 μgm−3, and closed kitchens emitting 477.25 μgm−3. The biomass burning % was high during the entire research. Because BC mass concentration was found to be high in indoor sampling, as a result, the health risk assessment is also considered to be high in all types of kitchens. As people spend a significant amount of time at home, especially in a future where remote work is anticipated to be easier, finding the activities, sources, and health effects that increase indoor pollution is vital to lowering indoor exposure. [ABSTRACT FROM AUTHOR]

Eight micro-samples from mural paintings of Malayadipatti and Adiyamankottai temples in Tamil Nadu, India were studied using binocular microscopy, thin film crystal X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, micro-Raman spectroscopy and field emission scanning electron microscopy to understand the original constituent materials of the pigments, binders and the methods of painting. Red paint had a mixture of cinnabar and hematite. The yellow colour resulted from orpiment. Orange hues were produced a mixture of orpiment and hematite. Grey colour was produced by a mixture of calcium carbonate and manganese dioxide. Black tones were prepared primarily using lamp black. The minerals used in both the temples were nearly identical. The appearance of proteinaceous materials/oils as a binding medium in all samples indicated the use of a tempera wall painting technique. These findings help improve our understanding of the methods and materials used in mural arts and serve as a guide for their future restoration. [ABSTRACT FROM AUTHOR]

Global precipitation change in response to climate change is closely related to surface temperature, the forcing agent, and the atmospheric dry energy budget, but regional precipitation change is more complex. In this study, we use experiments from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP) wherein carbon dioxide, sulfate aerosols, and black carbon aerosols are perturbed to study the global precipitation response in contrast with the regional response over India. The response to global warming from carbon dioxide increases precipitation both globally and regionally, whereas the cooling response to sulfate aerosol leads to a reduction in precipitation in both cases. The response to black carbon aerosols, however, is a global decrease but a regional increase of precipitation over India. The mechanism is increased atmospheric heating driving a stronger monsoon circulation and stronger low-level winds. This intensification of the Indian monsoon is, somewhat surprisingly, stronger for global black carbon emissions than when the emissions are limited to those from the Asian region. Overall, our study presents heterogeneity in precipitation responses at both global and regional levels and the potential underlying physical processes under a variety of climate forcings that would be useful in designing further model experiments with higher spatial resolution. [ABSTRACT FROM AUTHOR]

We reported the seasonal variations of columnar aerosol optical depth (AOD) and equivalent black carbon (EBC) from December 2018 to November 2019 in semi-arid station, Anantapur. Furthermore, using the two-component source apportionment model, we estimated the contribution of biomass burning (EBCbb) and fossil fuel combustion (EBCff) to the total EBC. The high AOD values at shorter wavelengths indicate that particle loading occurs primarily in fine mode aerosols. The high AOD500 was observed in the month of May (0.77 ± 0.19), and the low was in July (0.32 ± 0.11). The seasonal highest mean AOD500 was noticed during the summer (0.67 ± 0.12) followed by winter (0.49 ± 0.01), post-monsoon (0.43 ± 0.15) and monsoon (0.43 ± 0.17). The results revealed that both local emissions and long-range transported aerosols are primarily responsible for a significant spectral and temporal variability in AOD. In winter, the Angstrom exponent (α) was relatively high, whereas it was low in monsoon season. The mass concentrations of EBC, EBCff and EBCbb showed a strong diurnal and seasonal variations with in the study period. The highest and lowest EBC was noticed in winter and monsoon that is 2.64 ± 0.32, and 0.625 ± 0.16 μg/m3, respectively. The percentage contribution of annual mean EBC was 52.13% during the day and 47.86% during the night, respectively. With an average of 91.48%, EBCff contributes the most to total EBC during the study period. Furthermore, during all seasons, the hourly mean concentrations of EBC showed good agreement (r = 80) between the observed (Aethalometer) and MERRA-2 (Modern-Era Retrospective Study for Research and Applications). According to the MERRA-2 winds and Moderate Resolution Imaging Spectroradiometer (MODIS), the prevalence of fine mode particles throughout winter and summer is connected with continental air masses originating from India's central and northern regions. [ABSTRACT FROM AUTHOR]

Real-time measurement of black carbon (BC) aerosol contaminated air has potential for human health and climate change. A comprehensive investigation of BC concentration and its source apportionment distribution in the atmosphere of three traffic sites in East India was conducted using the portable Aethalometer (AE-33). The results showed that concentrations of BC ranged from 2.48 to 47.57 μg m−3 were minimum in Ranchi (RNC, 10.39 ± 2.48 μg m−3) and maximum in Jamshedpur (JSR, 18.22 ± 10.76 μg m−3). The average BC mass concentrations were reported as 18.22 ± 10.76 μg m−3, 14.18 ± 3.14 μg m−3, and 10.39 ± 2.48 μg m−3 at JSR, DHN (Dhanbad), and RNC, respectively. This was attributed to a high volume of traffic and a dense population in JSR compared to other sites. The airborne particulate particles arrived from various directions, as evidenced by backward trajectories. According to the diagnostic ratio analysis of BC, it was observed that the highest contribution of fossil fuel was reported at DHN (57%) and the highest contribution of biomass burning was reported at RNC (53%). Apart from explaining BC's atmospheric impacts, the health risk measurement of BC during various traffic sites over East India is also demonstrated in order. [ABSTRACT FROM AUTHOR]

Black carbon (BC) aerosols critically impact the climate and hydrological cycle. The impact of anthropogenic emissions and coastal meteorology on BC dynamics, however, remains unclear over tropical India, a globally identified hotspot. In this regard, we have performed in situ measurements of BC over a megacity (Chennai, 12° 59′ 26.5″ N, 80° 13′ 51.8″ E) on the eastern coast of India during January–June 2020, comprising the period of COVID-19-induced strict lockdown. Our measurements revealed an unprecedented reduction in BC concentration by an order of magnitude as reported by other studies for various other pollutants. This was despite having stronger precipitation during pre-lockdown and lesser precipitation washout during the lockdown. Our analyses, taking mesoscale dynamics into account, unravels stronger BC depletion in the continental air than marine air. Additionally, the BC source regime also shifted from a fossil-fuel dominance to a biomass burning dominance as a result of lockdown, indicating relative reduction in fossil fuel combustion. Considering the rarity of such a low concentration of BC in a tropical megacity environment, our observations and findings under near-natural or background levels of BC may be invaluable to validate model simulations dealing with BC dynamics and its climatic impacts in the Anthropocene. [ABSTRACT FROM AUTHOR]

Black carbon (BC) has importance regarding aerosol composition, radiative balance, and human exposure. This study adopted a backward-trajectory approach to quantify the origins of BC from anthropogenic emissions (B C An) and open biomass burning (B C BB) transported to Xishuangbanna in 2017. Haze months, between haze and clean months, and clean months in Xishuangbanna were defined according to daily PM 2.5 concentrations of >75, 35–75, and <35 µg/m3, respectively. Results showed that the transport efficiency density (TED) of BC transported to Xishuangbanna was controlled by the prevailing winds in different seasons. The yearly contributions to the effective emission intensity of B C An and B C BB transported to Xishuangbanna were 52% and 48%, respectively. However, when haze occurred in Xishuangbanna, the average B C An and B C BB contributions were 23% and 77%, respectively. This suggests that open biomass burning (BB) becomes the dominant source in haze months. Myanmar, India, and Laos were the dominant source regions of BC transported to Xishuangbanna during haze months, accounting for 59%, 18%, and 13% of the total, respectively. Furthermore, India was identified as the most important source regions of B C An transported to Xishuangbanna in haze months, accounting for 14%. The two countries making the greatest contributions to B C BB transported to Xishuangbanna were Myanmar and Laos in haze months, accounting for 55% and 13%, respectively. BC emissions from Xishuangbanna had minimal effects on the results of the present study. It is suggested that open BB in Myanmar and Laos, and anthropogenic emissions in India were responsible for poor air quality in Xishuangbanna. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, we have assessed the concentrations of black carbon (BC) measured using Aethalometer during different cooking periods in five different types of kitchens and different fuels in the tribal villages of east India. The BC mass concentrations were 397.24 ± 129.28, 403.49 ± 204.02, 463.45 ± 196.83, 458.77 ± 181.81 and 445.43 ± 193.67 µgm−3 for the indoor built kitchen (K1), indoor built kitchen but stoves situated in living area (K2), outside built kitchen (K3), semi-open kitchen (K4), and open cooking (K5), respectively. It is noted that the kitchen structure also significantly influences the accumulation of BC particles. During the whole study period, the maximum and minimum BC concentrations were 996.75 µg m−3 and 58.23 µg m−3, respectively. Maximum BC concentrations of 472.84 μgm−3 and minimum concentration of BC 402.11 μgm−3 were found on use of cow dung with paddy residue and wood as fuel, respectively. The result shows that the paddy residue emitted highest BC pollutants as compared to other fuel categories. We also studied the ambient BC concentration exposure for women living in villages. Despite no connection between study area and from industrial site, we observed a more tremendous amount of BC concentration. It shows that solid biomass fuel is responsible for increasing the concentrations level of BC in the atmosphere. The health risks were higher in K3 and K4 types of kitchens than in other types of kitchens. Our results indicate a requirement for a comprehensive study to thoroughly investigate the impact of household BC pollutants on the health risk assessments in the villages of east India. [ABSTRACT FROM AUTHOR]

Air is the basis for the existence of life on Earth; but in the present age of modernization the degrading quality of air year by year, due to the growth of Industrialization, urbanization, automobiles, coal-fired thermal power plants, and various other factories is the matter of real concern. To predict the future growth of air pollutants numerous prediction models have been developed by researchers. Time-series ARIMA model although quite useful for forecasting but fails to handle non-stationary problems. Among all the existing forecasting models, wavelets along with the Machine learning models have proved to be very successful and have been widely used in various fields like mathematical modeling, signal recognition, image recognition, classification, function approximation, data processing, filtering, clustering, compression, robotics, and decision making. It is also used in the field of mathematical forecasting for developing efficient prediction models. This paper aims to develop a wavelet-ANFIS conjugation model and a wavelet-ARIMA coupled model along with the time-series ARIMA model for the prediction of black carbon concentration over the Raniganj, Jharia, and Bokaro coal mines of India, by considering a long term data obtained by NASA (http://nasa.gov/) and compare the results obtained by these models for determining the best prediction model. The validity of the results is tested with the help of error measures like RMSE, MSE, MAPE, MAE, and relative error. Results over the three sample sites conclude that the Wavelet-ANFIS conjugation approach outperforms the wavelet-ARIMA coupled approach and the simple time-series ARIMA model. [ABSTRACT FROM AUTHOR]

Black carbon (BC) and PM2.5 chemical characterizations are crucial for insight into their impact on the health of the exposed population. PM2.5 sampling was carried out over selected residential sites of Jamshedpur (JSR) and Kharagpur (KGP), east India, during the winter season. Seven selected elements (SO42−, Cl−, Na+, NO3−, K+, Ca2+, and Mg2+) were analyzed using ion chromatography (IC). Black carbon (BC) sampling was also done at two different sites in JSR and KGP to understand its correlation. The PM2.5 ionic species mass concentration in JSR was in the order of SO42− > Cl− > Na+ > NO3− > K+ > Ca2+ > Mg2+, whereas in KGP, it was SO42− > NO3− > Cl− > Na+ > K+ > Ca2+ > Mg2+. The back-trajectory analysis showed that most of the air masses during the study period originated from the Indo Gangetic Plain (IGP). The Pearson relations of BC-PM2.5 indicate a better positive correlation (r = 0.66) at KGP compared to JSR (r = 0.42). As shown in the diagnostic ratio analysis, fossil fuel combustion and wood burning account for 51.51% and 36.36% of the total energy consumption in JSR city, respectively. In KGP city, the apportionment of origin sources were fossil fuel and wood burning at 43.75% and 34.37%, respectively. This study provides the first inventory of atmospheric particulate-bound chemical concentrations and BC profiles in middle-east India and informs policymakers and scientists for further studies. [ABSTRACT FROM AUTHOR]

Sea breeze onset studies are very important to understand the effects of local air pollution and its environmental impacts. In the present work, we obtained and studied the sea breeze onset time (SBOT) over a semi-urban environment (12.81°N, 80.03°E) located on a tropical east coast of India. Weather data measurements were carried out in the university campus of SRM Institute of Science and Technology from June 2019 to January 2020, except for the month of December 2019. The sea breeze component (SBC) was calculated on an hourly scale, and the SBOTs for different days were obtained and are discussed in detail. Measurements of surface black carbon mass concentration (SBCMC) from an aethalometer (AE-31) and aerosol optical depth (AOD) from a Microtops II Sunphotometer were obtained and used to assess the impact of sea breeze onset on SBCMC. The results of the study indicate that (i) the study site experienced the sea breeze on 33% of the 163 days of the study period, and the maximum days with SBOT occurred from 10:00 to 12:00 IST, (ii) an average decrease of 0.236 µg/m3 in SBCMC was observed on most of the days (72.2%) after the onset of the sea breeze, and (iii) an increase in AOD associated with a decrease in the Angstrom exponent (AE) was observed after the sea breeze onset, which suggests that the natural sea aerosols replaced the anthropogenic black carbon aerosols over the study location. [ABSTRACT FROM AUTHOR]

Climatological variations and trends in aerosol parameters were studied over six different regions identified as different source regions of aerosol emissions over India. Analysis was carried out on monthly mean satellite data for total aerosol optical depth (AOD), black carbon AOD (BC-AOD), single-scattering albedo (SSA) and Ångström exponent (ANG), in addition to NCEP reanalysis data for air temperature and relative humidity, for two decades (2000–2019) over the six different Indian regions. Through analysis of seasonal and annual climatology, it was found that region R3 (Indo-Gangetic Plain) was the most aerosol-laden area, as evidenced by a high value of BC-AOD and AOD. A high mean value of ANG indicated an increase in natural aerosol emissions over region R1 (Northeast India). Single-scattering albedo was highest in region R4 (South India). The aerosol changes over all regions showed a lower enhancing trend in total AOD and BC-AOD in the second decade (2010–2019) as compared with the first decade (2000–2009), which was attributed to the improvements in vehicle technology and use of more refined fuels in the domestic sector. The decreasing trend in Ångström exponent and AOD indicates that the anthropogenic aerosol loading decreased in the second decade relative to the first decade. [ABSTRACT FROM AUTHOR]

We hypothesize that firework events involving the combustion of charcoal fuel, organic binders, metal salts, and cellulose-based wrapping material could be significant transient sources of aerosol brown carbon (BrC). To test this, we couple high time-resolution (1 min) measurements of black carbon (BC) and BrC absorption from a 7-wavelength aethalometer with time-integrated (12–24 h) measurements of filter extracts, i.e., UV–visible, fluorescence, and Fourier-transformed infrared (FT-IR) signatures of BrC, total and water-soluble organic carbon (OC and WSOC), ionic species, and firework tracer metals during a sampling campaign covering the Diwali fireworks episode in India. In sharp contrast to BC, BrC absorption shows a distinct and considerable rise of 2–4 times during the Diwali period, especially during the hours of peak firework activity, as compared to the background. Fluorescence profiles suggest enrichment of humic-like substances (HULIS) in the firework plume, while the enhancement of BrC absorption in the 400–500 nm range suggests the presence of nitroaromatic compounds (NACs). Considerable contributions of WSOC and secondary organics to OC (44.1% and 31.2%, respectively) and of the water-soluble fraction of BrC to total BrC absorption (71.0%) during the Diwali period point toward an atmospherically processed, polar signature of firework-related BrC, which is further confirmed by FT-IR profiles. This aqueous BrC exerts a short-lived but strong effect on atmospheric forcing (12.0% vis-à-vis BC in the UV spectrum), which could affect tropospheric chemistry via UV attenuation and lead to a stabilization of the post-Diwali atmosphere, resulting in enhanced pollutant build-up and exposure. [ABSTRACT FROM AUTHOR]

Black carbon (BC) along with PM2.5 (fine particular matters) plays an important role in the assessment health effect of human beings. Winter season campaign measurements carried out for BC concentrations by using 7 different wavelengths such as 370, 470, 520, 590, 660, 880, and 950 nm, handy aethalometer (AE-33, Magee Scientific, USA), at two different locations i.e., National Institute of Technology, Jamshedpur (NIT J) and Sakchi, Jamshedpur (SAK J), in eastern India. During the study period, the mass concentration of BC varies from 4.19 µgm−3 to 15.36 µgm−3, with an average mean of 8.88 ± 2.40 µgm−3 in NIT J and SAK J, the mass concentration of BC varies from 6.3 µgm−3 to 13.48 µgm−3, with an average mean of 10.29 ± 1.58 µgm−3. However, the concentration of PM2.5 varies from 102.98 µgm−3to 198.21 µgm−3, with an average mean of 155.82 ± 29.98 µgm−3 in NIT J and SAK J, the concentration of PM2.5 varies from 110.83 µgm−3 to 207.65 µgm−3, with an average mean of 169.14 ± 22.40 µgm−3. It was reported that SAK J has a higher BC concentration compared to NIT J. This was due to heavy traffic load and dense population in SAK J. Backward Trajectories were seen that the airborne particulate matter came from differerajeshnt directions. According to the diagnostic ratio analysis of BC, it was observed that most of the BC mass concentrations come from fossil-fuel (69.70%) followed by wood-burning (30.30%) in a particular place. The overall health risk assessment of BC concentration observed during the study period was 26.70, 13.95, 24.95 and 51.32 at NIT J as well as 32.07, 16.72, 29.95 and 61.87 at SAK J, the passive cigarettes comparable concerning the risk of CVM, LC, LBW, and PLEDSC, respectively. [ABSTRACT FROM AUTHOR]

Black Carbon (BC) is a major pollutant that poses immediate health as well as long-term climatic threat to human civilization. Globally, India and China are considered to be among the significant contributors of carbonaceous aerosol. Therefore, in the recent past, several studies on BC measurements have been conducted and reported in both these countries. Optical absorbance measurement techniques which give BC mass by measuring light absorbance of aerosol have been used widely. Keeping these facts in mind, here an attempt has been made to realise the current state of Equivalent Black Carbon (EBC) measurement done in both countries. Eighty EBC measurement studies published in last 15 years (2005-2020) are analysed on the basis of technique, instrumentation and various important parameters involved in measurements. It is found that EBC measurements in India and China contain large uncertainties, and available data are metrologically insufficient to realise spatial distribution and long-term temporal variation precisely. Furthermore, MERRA-2 Surface Black Carbon (SBC) levels and EBC measurements are compared and evaluated for biases between spatial and temporal variation of modelled data and ground measurements. It is observed that standardization of measurement technique and parameters involved in measurement is the need of the hour. Lack of a reference method creates inconsistency and discrepancy among the measurements. Recommendations for selection of parameter/instrument and cautious measures are provided as conclusion based on this review to improve overall metrology of BC. [ABSTRACT FROM AUTHOR]

The entire world is affected by Coronavirus disease (COVID-19), which is spreading worldwide in a short time. India is one of the countries which is affected most, therefore, the Government of India has implemented several lockdowns in the entire country from April 25, 2020. We studied air pollutants (i.e., PM2.5, Black Carbon (BC), and Polycyclic Aromatic Hydrocarbons (PAHs) level, and observed significantly sudden reduced. In India, most of the anthropogenic activities completely stopped. Therefore, we studied the levels of BC, PAHs and PM2.5 concentrations, their sources apportion, and health risk assessment during normal days, lockdown (from lockdown 1.0 to lockdown 4.0) and unlock down 1.0 situation at Sakchi, Jamshedpur city. It was observed that lockdowns and unlock down situations BC, PAHs and PM2.5 concentrations were significantly lower than regular days. We applied the advanced air mass back trajectory (AMBT) model to locate airborne particulate matter dispersal from different directions to strengthen the new result. The diagnostic ratio analyses of BC shows that wood burning contribution was too high during the lockdown situations. However, during normal days, the PAHs source profile was dedicated toward biomass, coal burning, and vehicle emission as primary sources of PAHs. During the lockdown period, emission from biomass and coal burning was a significant contributor to PAHs. The summaries of health risk assessment of BC quantified an equal number of passively smoked cigarettes (PSC) for an individual situation was studied. This study focuses on the overall climate impact of pandemic situations. [ABSTRACT FROM AUTHOR]

In 1995, a multimillion-dollar experiment – the Indian Ocean Experiment – discovered a dark mass of polluting air hovering above the Indian subcontinent. This mass of air was termed a cloud and found to be composed of a high amount of black carbon that was judged to be the second biggest threat to climate change after carbon-dioxide. In this article, an attempt is made to trace the life of black carbon by documenting its changing forms since the experiment. It emerges that the changing forms allow for the movement of air – smoke from traditional cookstoves and vehicular diesel emissions in India lead to the formation of the cloud – and reveal how an ethnography of air can be undertaken. [ABSTRACT FROM AUTHOR]

Biomass burning contributes considerably to black carbon (BC) emissions in South Asia, but such emissions have not been linked with the Green Revolution (GR) which has enabled substantial crop production growth in South Asian countries, India in particular. Here, we use an Earth system model to quantify climate change through the direct radiative forcing (DRF) by agriculture‐emitted BC associated with the GR in India. We show that the BC DRF in India has increased significantly since the GR, especially during the post‐GR period. The estimated BC DRF in India rose from +0.197 W/m2 in 1961 to +0.805 W/m2 in 2011; this represents a fourfold increase in DRF since the onset of the GR. The contribution of BC DRF by India's intensive agriculture to the global BC forcing also increased from 2.6% to 4.4% during the GR. Our results reveal that increasing BC emissions associated with the GR raises the importance of emission mitigation from agriculture source. Plain Language Summary: Black carbon originated from incomplete combustion can endanger human health and contaminate the environment. The light‐absorbing nature of black carbon is of vital importance to regional and global climate. Emissions from agriculture sources consist of large portion of black carbon particles, especially in India with intensive agriculture. The GR aiming at improving agriculture development in India has accomplished great success since the 1960s, but its side effects on long‐term climate change have not been assessed. In the present study, we quantify black carbon contamination and DRF induced by agriculture activities including crop residue burning from 1961 to 2011 during which the GR has been operated. Our results reveal that agricultural emission in India is an important sector contributing to the local and regional climate forcing. Such contribution could extend to the global climate. We propose that considerable and continuous efforts need to be made to control agriculture emissions in India to achieve a sustainable GR, in the meanwhile, mitigate the climate change. Key Points: Agricultural emission in India is an important sector contributing to the local and regional black carbon contamination and climate forcingEstimated regional black carbon direct radiative forcing in India showed a fourfold increase during the operation of the Green Revolution (GR)The contribution of India's intensive agriculture associated with GR to global black carbon climate forcing grew significantly [ABSTRACT FROM AUTHOR]

The SARS-CoV-2 pandemic resulted in India imposing a nationwide lockdown on 22 March 2020, bringing all human activities to a complete halt. The current study focuses on the effect of lockdown on the abundance of atmospheric aerosols over Goa. The study focused on pre-lockdown, lockdown and period corresponding to lockdown in 2019. The AOD spectra depicted a decrease in the anthropogenically derived fine mode aerosols during the lockdown compared to the pre-lockdown period. Mean AOD500 for prelockdown and lockdown periods were 0.43 ± 0.19 and 0.53 ± 0.11 respectively. The higher AOD500 during lockdown was due to an increase in naturally derived coarse mode aerosols, which is further confirmed with the lower Ångström exponent values (1.04 ± 0.11). The mean black carbon mass concentration for the respective periods were 1990.45 ± 470.87 ng m–3 and 1109.71 ± 218.33 ng m–3, and the mean atmospheric forcing during the respective periods were 25.13 ± 5.72 W m–2, 27.31 ± 3.71 W m–2 and 30.81 ± 5.59 W m–2 respectively. [ABSTRACT FROM AUTHOR]

The ongoing COVID-19 pandemic necessitated a complete lockdown from 24 March to 31 May 2020 as imposed by the Government of India to prevent the spread of the virus that resulted into halting most of the economic activities during that period. The stringent anthropogenic activities during the lockdown phase resulted in a notable drop in the air pollution level. The prevailing global scenario during the pandemic has provided an opportunity of assessing the air quality in the absence of normal anthropogenic activities. In the present article, the impacts of reduced anthropogenic activities on the black carbon concentration and associated atmospheric parameters have been studied over a tropical urban location, Kolkata (22.57°N, 88.37°E) in eastern India. Investigations have been made on the impacts on the parameters like atmospheric electric field, wind speed, temperature, relative humidity, dew point temperature, rain accumulation and soil moisture during this unusual time in comparison to the same time span of the previous year 2019 when the usual human activities were pursued. [ABSTRACT FROM AUTHOR]

To combat the present COVID-19 pandemic, a countrywide lockdown (LD) was imposed in India from 25 March until 31 May 2020. This unique scenario brought a decline in various anthropogenic activities leading to a considerable decrease in the concentration of several atmospheric pollutants. In this scenario, CSIR-IMMT Bhubaneswar carried out black carbon (BC), PM10 and PM2.5 analysis through optical and gravimetric measurements, respectively, during March-May 2020 followed by a comparison with previous years (2017–2018) of observation. There was a reduction of ~33% in average overall BC concentration along with a significant drop in PM10 (33%) (P < 0.05) and PM2.5 (~38%) (P < 0.05) during the entire LD period as compared to 2017–2018. During LD, contribution from biomass burning was enhanced by almost 3 times as compared to 2017–2018. However, the simultaneous meteorological variation during the LD period prevents clear distinction of the impact of lockdown on BC and PM. [ABSTRACT FROM AUTHOR]

In this study, we assess the response of ambient aerosol black carbon (BC) mass concentrations and spectral absorption properties across Indian mainland during the nation-wide lockdown (LD) in connection with the Coronavirus Disease 19 (COVID-19) pandemic. The LD had brought near to total cut-off of emissions from industrial, traffic (road, railways, marine and air) and energy sectors, though the domestic emissions remained fairly unaltered. This provided a unique opportunity to delineate the impact of fossil fuel combustion sources on atmospheric BC characteristics. In this context, the primary data of BC measured at the national network of aerosol observatories (ARFINET) under ISRO-GBP are examined to assess the response to the seizure of emissions over distinct geographic parts of the country. Results indicate that average BC concentrations over the Indian mainland are curbed down significantly (10–40%) from prelockdown observations during the first and most intense phase of lockdown. This decline is significant with respect to the long-term (2015–2019) averaged (climatological mean) values. The drop in BC is most pronounced over the Indo-Gangetic Plain (>60%) and north-eastern India (>30%) during the second phase of lockdown, while significant reduction is seen during LD1 (16–60%) over central and peninsular Indian as well as Himalayan and sub-Himalayan regions. Despite such a large reduction, the absolute magnitude of BC remained higher over the IGP and north-eastern sites compared to other parts of India. Notably, the spectral absorption index of aerosols changed very little over most of the locations, indicating the still persisting contribution of fossil-fuel emissions over most of the locations. [ABSTRACT FROM AUTHOR]

Biomass is one of the prime domestic energy sources in the kitchens and about 60% of households are still using biomass and kerosene for cooking in India. These traditional cooking practices are incompetent as the use of biomass in traditional cookstove produces an enormous amount of carbonaceous aerosols that lead to indoor and outdoor air pollution. Emissions of various pollutants like black carbon (BC), PM10 and PM2.5 from burning of biomass cause serious health impacts like respiratory illness, lung cancer, watering of eyes, coughing, asthma and heart problems especially in women due to higher rate of inhalation of these fine particulate matters during the cooking period. Quantification of BC, PM2.5 and PM10 emissions from a different type of biomass in various types of kitchen arrangements and its associated impacts are poorly examined in India. Hence, daily concentrations of BC, PM2.5 and PM10 were monitored from different types of biomass user's households during January 2018 to December 2019 to assess indoor air quality by using aethalometer and nephelometer (pDR-1500) in three districts (Sitapur, Patna and Murshidabad) of Indo-Gangetic Plains (IGP) where approximately, 96% of rural families rely on biomass cooking. The highest mass concentrations were observed in biomass user's households and cow-dung cake users due to low calorific value. About 30.13% of PM10 and 35.89% of PM2.5 data exceeded the national ambient air quality standard on a daily basis in biomass user's households. A cancer risk assessment was also conducted in terms of mass concentration of these pollutants. The lifespan danger from exposure to BC was 4.33 × 10−7 in indoor for non-ventilated kitchens, 2.63 × 10−7 in indoor for ventilated kitchens, 3.98 × 10−7 in outdoor for separated kitchen, 3.22 × 10−7 for semi-open kitchen and 1.78 × 10−7 for open kitchen. The vulnerability assessment for cancer mortality under exposure of pollution was estimated to be highest for the age group of more than 50 years whereas lowest for the age group of 0–4 years for all kinds of kitchens in the study area. [ABSTRACT FROM AUTHOR]

Brahmaputra Valley of northeast India is relatively pristine, with low local emission levels, but is susceptible to long-range transport from west Asian deserts. Hourly measurements of aerosol particulate matter (PM2.5 and PM10) and black carbon (BC) over a period of 1 year (June 2013–May 2014) over Tezpur station (26.63° N, 92.77° E), located in the Brahmaputra Valley, display annual mean PM2.5 and BC of 42 ± 25 µg m−3 and 6 ± 1.5 µg m−3, respectively, indicating that Tezpur enjoys lower pollution levels than other northeast stations. The lowest concentrations of PM2.5 and PM10 (~ 14.7 and 24 µg m−3, respectively) are observed during the monsoon season (JJAS). The highest values (~ 91 and 114 µg m−3) are observed during the winter (DJF) due to local atmospheric conditions and some additional transport from the west Asian deserts and the Indo-Gangetic Basin (IGB). Local emissions seem to be mainly responsible for moderate values (~ 24 and 42 µg m−3) of PM during the post-monsoon (ON) season with weak winds. Coarse particles (diameter > 2.5 µm) are much higher (approx. 47% of PM10) in the pre-monsoon than in the other seasons due to the long-range transport of dust particles from the IGB and west Asian deserts as well as sea salt particles from the Bay of Bengal. WRF-Chem model simulation underestimated the concentration of PM2.5 and PM10 as compared to daily mean observations. The variation in the "model–observation" time series for relative humidity (RH) and boundary layer height suggests that underestimation of PM10 is due mainly to the underestimation of RH and overestimation of the ventilation coefficient by the model during winter and pre-monsoon seasons. [ABSTRACT FROM AUTHOR]

We have studied the black carbon (BC) mass concentrations, contributions from Fossil Fuels (FF), and Biomass burning (BB) to total BC mass concentrations using a 7-wavelength Aethalometer (Model, AE-31; Make, Magee Scientific, USA) at a rural continental location in the northeastern India. We have taken the continuous measurements of BC from January 2011 to December 2017 (excluding the year 2016 due to nonavailability of data). The annual mean BC concentration at 880 nm is observed maximum 12.56±5.06 µgm-3 in the year 2011 with a minimum of 7.26±2.76 µgm-3 during the year 2015." is the final sentence. BC, BCff, and BCbb mass concentrations show significant variation during morning, afternoon, evening, and night hours. The significant monthly, seasonal, and annual variabilities in the BC concentration, equivalent BC from FF and BB, are due to seasonal change in the emission sources, boundary layer dynamics, and dispersion and dilution conditions. The determination of Angstrom exponent (α) for the BC emitted during burning of different biofuels by performing a burning experiment is an important part of the present study. We have conducted a survey in and around the study location to know the different biofuels used by the people for daily household activities, and those biofuels are used in the burning experiment. As a result of biomass burning experiment to determine Angstrom exponent, we have found the α values to be ranging from 1.20 to 2.37 for flaming and a range from 1.59 to 2.33 for smoldering conditions for different biofuels. Annual mean contributions of BCff and BCbb to the total BC are found to be dominated by FF emissions during the whole study period. The percentage contribution of BCff and BCbb is found to be 56% and 44% during winter season due to increase in wood and biomass burning activities for various purposes. We have found the higher percentage contribution from BCff (85%) during monsoon season due to reduction in usage of biofuels. [ABSTRACT FROM AUTHOR]

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 µ g m -3), when the prevailing air masses were mostly of IGP origin, followed by post-monsoon (October–November) (mean ∼1.34±1.40 µ g m -3). The mass median diameter (MMD) of the BC mass size distributions was in the range 0.190–0.195 µ m, 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 µ g m -3), and larger BC cores (MMD > 0.210 µ m) 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 µ m), 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. [ABSTRACT FROM AUTHOR]

This paper discusses pigments used in Indian palm leaf manuscripts. Formerly it was believed that pigments for palm leaf illustrations were mostly sourced from plant extracts – a believe that is still widespread in India. This paper reports the identification of pigments of an illustrated palm leaf manuscript (eighteenth – nineteenth century) collected from the east coast of India. As Raman spectra of many pigments gave too high background noise, the identification was mostly accomplished through SEM-EDX and FTIR spectroscopy. The analytical findings indicated that both mineral colours and plant extracts were sourced for Indian palm-leaf manuscripts. Analysis indicated the use of lamp black for black, indigo for blue, vermillion for red, orpiment for yellow, china clay for white and a mixture of orpiment and indigo for green coloration in the illustrations. The data has improved our knowledge of historic pigments used in palm leaf illustrations. As some of the pigments are either photosensitive or darken due to atmospheric pollution, necessary preventive conservation measures need to be adopted. [ABSTRACT FROM AUTHOR]

Black carbon (BC) is known to have major impacts on both climate and human health and is therefore of global importance, particularly in regions close to large populations that have strong sources. The size-resolved mixing state of BC-containing particles was characterised using a single-particle soot photometer (SP2). The study focusses on the Indo-Gangetic Plain (IGP) during the pre-monsoon and monsoon seasons. Data presented are from the UK Facility for Airborne Atmospheric Measurements BAe-146 research aircraft that performed flights during the pre-monsoon (11 and 12 June) and monsoon (30 June to 11 July) seasons of 2016. Over the IGP, BC mass concentrations were greater (1.95 µgm-3) compared to north-west India (1.50 µgm-3) and north-east India (0.70 µgm-3) during the pre-monsoon season. Across northern India, two distinct BC modes were recorded; a mode of small BC particles (core diameter <0.16 µm and coating thickness <50 nm) and a mode of moderately coated BC (core diameter <0.22 µm and coating thickness of 50–200 nm). The IGP and north-east India locations exhibited moderately coated black carbon particles with enhanced coating thicknesses, core sizes, mass absorption cross sections, and scattering enhancement values compared to much lower values present in the north-west. The coating thickness and mass absorption cross section increased with altitude (13 %) compared to those in the boundary layer. As the monsoon arrived across the region, mass concentration of BC decreased over the central IGP and north-east locations (38 % and 28 % respectively), whereas for the north-west location BC properties remained relatively consistent. Post-monsoon onset, the coating thickness, core size, mass absorption cross section, and scattering enhancement values were all greatest over the central IGP much like the pre-monsoon season but were considerably reduced over both north-east and north-west India. Increases in mass absorption cross section through the atmospheric column were still present during the monsoon for the north-west and central IGP locations, but less so over the north-east due to lack of long-range transport aerosol aloft. Across the Indo-Gangetic Plain and north-east India during the pre-monsoon and monsoon seasons, solid-fuel (wood burning) emissions form the greatest proportion of BC with moderately coated particles. However, as the monsoon develops in the north-east there was a switch to small uncoated BC particles indicative of traffic emissions, but the solid-fuel emissions remained in the IGP into the monsoon. For both seasons in the north-west, traffic emissions form the greatest proportion of BC particles. Our findings will prove important for greater understanding of the BC physical and optical properties, with important consequences for the atmospheric radiative forcing of BC-containing particles. The findings will also help constrain the regional aerosol models for a variety of applications such as space-based remote sensing, chemistry transport modelling, air quality, and BC source and emission inventories. [ABSTRACT FROM AUTHOR]

In this study, the evaluation of carbonaceous fine particulate matter (C-PM) was conducted using the SAFAR-India regional model. Two emission inventories were utilized: the newly developed SAFAR inventory and the global EDGAR-HTAP inventory, both for the year 2018. The simulation aimed to capture the seasonal and spatial patterns of black carbon (BC) and organic carbon (OC) concentrations. To validate model results, surface meteorological parameters, and C-PM concentrations were compared with the MERRA reanalysis data for the Indian region. Model simulated surface C-PM concentration with SAFAR emission inventory is found to be slightly overestimated (1.10), whereas simulated results with EDGAR emission inventory is significantly underestimated as compared to MERRA data. Model-simulated meteorological parameters showed a better correlation with MERRA reanalysis. Simulated geographical patterns of seasonal mean C-PM with SAFAR emission inventory exhibit quite a better comparison with MERRA reanalysis as against EDGAR simulated results. However, some differences in the present results are visible, particularly over the IGP region, as compared to MERRA data, but they are mainly attributed to a significant difference in the special resolution of present results (much finer) as compared to coarser MERRA data. In the Indo-Gangetic Plain (IGP) region, the concentration of BC SF and OC SF (BC and OC with SAFAR emission, respectively) show the peak during the winter, followed by the post-monsoon season. Although the correlation coefficients of hourly time series of surface BC SF and OC SF concentrations with MERRA over India are high (0.92 and 0.88), the poor RMSE, is attributed mainly to different scales of resolution. The model simulated BC, and OC concentrations with SAFAR emission input capture the pattern of spatial distribution reasonably well. The present evolution of BC and OC will help to better quantify their impact on climate and atmospheric conditions over the Indian region. [Display omitted] • C-PM from MERRA compares the simulations with SAFAR & EDGAR emission inventory. • Simulation provides the seasonal variations in BC and OC, with the highest concentrations in the winter at the IGP region. • Meteorology dominates the emissions during the monsoon season in BC and OC variation. • The study suggests that simulated C-PM using SAFAR capture hotspots regions across India as compared to other simulations. [ABSTRACT FROM AUTHOR]

The near-simultaneous measurements of wavelength dependent light absorption properties of black carbon (BC) aerosols employing the seven-channel, model AE-33 Aethalometers are carried out from the campuses of Ahmednagar College, Ahmednagar (AC-Ahmednagar) and Indian Institute of Tropical Meteorology, Pune (IITM-Pashan) from December 2015 to December 2016. Analysis brings out statistically significant higher values of BC absorption coefficient [σ abs,880 nm (BC), Mm−1 (hence BC mass concentration) at site AC-Ahmednagar (annual mean = 99.95 ± 79.8 Mm−1) as compared to those at site IITM-Pashan (annual mean = 47.19 ± 59.9 Mm−1). The seasonal mean values of σ abs,880 nm (BC) illustrate conspicuous intra-seasonal variability at both the locations. This variability seems to be influenced by the seasonal nature and strengths of BC emission sources, local meteorology, dynamics in atmospheric boundary layer (ABL) and modulation in advection pathways. The absorption Ångström exponent (AAE) analysis reveals that there exists a predominant contribution to the total BC by fossil fuel emission enriched mixed carbonaceous aerosols as well as freshly emitted fossil fuel burning BC aerosols at site AC-Ahmednagar while at site IITM-Pashan the major contribution to the total BC appears to come from fossil fuel/biomass emission enriched mixed carbonaceous aerosols. The source apportionment of BC mass depicts that the fractional contributions of BC_FF to BC mass dominate throughout the year at both observing locations. Seasonal variability of BC_BB fraction of BC at both locations is found to be complimentary to the seasonal variability of BC_FF fraction of BC at respective sites. • Seasonal mean σ abs,800 nm (BC) illustrates conspicuous intra-seasonal variability. • AAE variability depicts predominance of fraction BC_FF to BC throughout the year. • BC_FF and BC_BB seasonal variabilities are found to be complimentary each other. • Seasonally different advection pathways prevail at studied locations. [ABSTRACT FROM AUTHOR]

With a view to improving the performance of WRF-Chem over the Indian region in simulating BC (black carbon) mass concentrations as well as its short-term variations, especially on a diurnal scale, a region-specific diurnal variation scheme has been introduced in the model emissions and the performance of the modified simulations has been evaluated against high-resolution measurements carried out over eight ARFI (Aerosol Radiative Forcing over India) network observatories spread across India for distinct seasons: pre-monsoon (represented by May), post-monsoon (represented by October) and winter (represented by December). In addition to an overall improvement in the simulated concentrations and their temporal variations, we have also found that the effects of prescribing diurnally varying emissions on the simulated near-surface concentrations largely depend on the boundary layer turbulence. The effects are perceived quickly (within about 2–3 h) during the evening–early morning hours when the atmospheric boundary layer is shallow and convective mixing is weak, while they are delayed, taking as much as about 5–6 h, during periods when the boundary layer is deep and convective mixing is strong. This information would also serve as an important input for agencies concerned with urban planning and pollution mitigation. Despite these improvements in the near-surface concentrations, the simulated columnar aerosol optical depth (AOD) still remains largely underestimated vis-à-vis the satellite-retrieved products. These modifications will serve as a guideline for further model-improvement initiatives at a regional scale. [ABSTRACT FROM AUTHOR]

Abstract India is currently the second-largest emitter of black carbon (BC) in the world, with emissions projected to rise steadily in the coming decades. In view of the large variations associated with BC emission inventories in this region, model outputs of BC mass and radiative forcing (RF) need to be validated against long-term regionally-representative atmospheric measurements. Such measurements are highly scattered spatially as well as temporally in India, and a systematic evaluation of BC data is non-existent so far. To address this issue, we present here a comprehensive review of BC measurements in India from a survey of >140 studies spanning 2002–2018. In addition to summarizing baseline BC levels in urban, semi-urban, rural and remote locations, we report impacts of anomalous environmental and/or emission conditions, e.g., truck/general strikes, firework events, fog/haze episodes, large-scale biomass burning events, etc. We also present a discussion on major BC sources and climate impacts (in terms of direct RF) in major land-use categories, mitigation strategies currently employed on a national scale, and recent advances in measuring brown carbon (BrC) in India. We identify key areas for improvement, such as – i) the need for long-term BC monitoring networks, especially in regions where estimated emissions are high but measurement coverage is low; ii) the general lack of understanding, despite some recent reports, of BC aerosol mixing states, aging and direct climate effects in the Indian context; iii) the need to shift from qualitative approaches of BC source apportionment to robust quantitative measures; and iv) the prospects for coupled chemical-optical characterization of BrC for a better understanding of its sources and climate effects. We list potential research directions for the scientific community to address these knowledge gaps. We also believe that this review will be beneficial to policymakers for prioritizing BC mitigation efforts. Graphical abstract Unlabelled Image Highlights • First review of atmospheric black carbon (BC) measurements (2002–2018) in India • Summary of BC levels, sources and radiative effects in urban, rural and remote areas • The Indo-Gangetic Plain is the major driver of BC emission and regional outflow • Various anomalous environmental/emission conditions substantially enhance BC levels • Greater emphasis proposed for studying BC aerosol mixing states and climate effects [ABSTRACT FROM AUTHOR]

Black carbon (BC) aerosol formed from incomplete combustion of fossil fuel and biomass combustion is collected at an educational institute, Madurai Kamaraj University, Madurai located in Southern India. The sampling is done using an Aethalometer (AE-31) from January to March (2015 to 2017) to study the effect of meteorological parameters and anthropogenic activities during the transition from winter to summer. BC identified from a variety of sources showed strong diurnal variation with two peaks, first one at early morning hours and the ot. her one at evening hours, but this peak timings varied with the seasons. It is observed that biomass combustion and tobacco smoke at the study site dominates other sources. Raman spectral analysis showed strong organic source peak. [ABSTRACT FROM AUTHOR]

The effect of smoke aerosols on the low-level clouds over the Indian landmass during the winter season is examined using 15 years (2005–2019) of long-term multi-satellite observations and reanalyses (MERRA-2 and ERA-5) datasets. Climatologically higher values of aerosol optical depth (AOD) (> 0.6), Angstrom exponent (> 1.5), UV-aerosol index (> 0.7), and black carbon and organic carbon (BC + OC) extinction aerosol optical thickness (EXTAOT) (> 0.18) are found over the Indo-Gangetic Plain (IGP) compared to the rest of India indicating the dominance of smoke aerosols over the region. However, considerable enhancements in AOD (~ 60%) and (BC + OC) EXTAOT (20–40%) are observed over some parts of eastern India (particularly Odisha and Chhattisgarh) and central-south India compared to IGP (< 10% and < 5% respectively) in the recent years. Also, fire activities are increasing over almost the same region where smoke aerosols increased considerably, suggesting a significant role of local biomass burning (BB) in the observed rise of smoke aerosols. However, prevailing wind patterns and HYSPLIT backward air mass trajectories indicate that long-range transport from the upper IGP regions and northwestern sides of India and beyond could also increase smoke loading over this region. Climatologically, distinct spatial patterns with moderate cloud fraction (CF) (0.5–0.6) and comparatively larger liquid cloud effective radius (CER) (16–17 μm) are found over the IGP region. This study suggests that mainly low-level clouds contribute to this distinct signature of cloud distributions. However, a significant increase in CF (50–60%) is observed over almost the same region where smoke aerosols showed a considerable rise, implying the possible influence of smoke aerosols on the low-level clouds. While CF and CER showed a noticeable increase in the polluted condition, cloud optical thickness and liquid cloud water path showed a consequent decrease with increased aerosol loading. CALIPSO images suggest that mostly a mixture of dust, polluted dust, and polluted continental/smoke aerosols showed clear dominance over the inland areas, mostly confined within 2 km altitude over almost the entire study domain. However, an elevated layer of absorbing aerosols (smoke and polluted dust) over the low-level cloud increased the cloud fraction through the 'aerosol-cloud-boundary layer' feedback mechanism. • The dominance of smoke aerosols is prevalent over the IGP region during winter. • Increase in smoke aerosols and biomass burning observed over eastern and central-south India in recent years. • CF and CER showed a considerable increase in polluted conditions. • Absorbing aerosols above the low-level cloud decks increased CF over the central IGP. [ABSTRACT FROM AUTHOR]

India's air quality is in a dismal state, with many studies ascribing it to PM 2.5. Most of these corroborate that carbonaceous aerosol (CA) constitute significant fraction of PM 2.5. However, investigations on the effect of long-term meteorological or emission changes on PM 2.5 and its components, and their associated health effects are rare. In this work, WRF-Chem simulations for three seasons over four years (2016–2019) were carried out to cogitate the spatial and temporal changes in PM 2.5 and its components in India. Model predicted PM 2.5 concentrations were in good agreement with the ground-based observations for 25 cities. PM 2.5 was highest in winter and lowest in pre-monsoon. PM 2.5 reduced by ∼8% in Indo-Gangetic Plain (IGP) but increased by ∼38% and ∼130% in south and northeast India, respectively, from 2016 to 2019. IGP witnessed three times higher average PM 2.5 concentrations than south India. No significant interannual change in CA contributions was observed, however, it peaked in the winter season. Other inorganics (OIN) were the major component of PM 2.5, contributing more than 40%. Primary organic aerosol (POA) fractions were higher in north India, while secondary inorganic aerosol (SIA) dominated south India. Transport and residential sectors were the chief contributors to CA across India. Biomass burning contributed up to ∼23% of PM 2.5 in regions of IGP during post-monsoon, with CA fractions up to 50%. Associations between PM 2.5 and its components with daily inpatient admissions from a tertiary care centre in Delhi showed that PM 2.5 and OIN had lower associations with daily hospital admissions than CA. Every 10 μg/m3 increase in POA, black carbon (BC), and secondary organic aerosol (SOA) were associated with ∼1.09%, ∼3.07% and ∼4.93% increase in the risk of daily hospital admissions. This invigorates the need for more policies targeting CA rather than PM 2.5 to mitigate associated health risks, in India. [ABSTRACT FROM AUTHOR]

We present results of measurements of black carbon (BC) from ground-based wet-only rainwater (RW) and cloud-water (CW) sampling at a mountain field station, Sinhagad, situated in south western India during the period from June 2008 to October 2010. The amount of BC in the sample was determined by photometry at a wavelength of 528 nm after a procedure including the filtration through a 0.4 μm polycarbonate membrane filter. Water soluble concentrations of major anions in RW and CW were also determined. The average concentration of BC in RW (16 μmol dm −3 ) is higher by at least a factor 2 than that found in similar studies reported from other parts of the world. On the other hand, the average concentration of BC in CW (47 μmol dm −3 ) is lower by about a factor of 2 than that found at other sites. The ratio between the average concentrations in CW and RW varies from 2 (K + ) to 7 (SO 4 2− ). The ratio for BC was about 3. No significant difference was observed for pH. Analysis of air mass back trajectories and of correlations between the various components indicates that long range transport of pollutants and dust from East Africa and Southern part of the Arabian peninsula might contribute to the high concentrations of BC and some of the ionic constituents at Sinhagad during the monsoon season. [ABSTRACT FROM AUTHOR]

Black Carbon (BC) and Organic Carbon (OC) are the principal chemical aerosol components generated during combustion, both of which play a key role in air pollution, human health and climate change. Several studies of OC and BC have been conducted over India to assess the contribution from household and fossil fuel-based sources; however, studies on their emissions and their contribution from forest and cropland fires are quite limited. To address this issue, as part of this research, we derived a vegetation burning-based inventory of BC and OC aerosols over India at a resolution of 250 m × 250 m. Using a consumed biomass technique, we estimated emissions based on updated emission factor estimates. During the fire season in India (March–June), the mean OC and BC emissions were 2.1 ± 5.2 × 1013 kg per year and 1.8 ± 4.4 × 1012 kg per year, respectively. Andhra Pradesh had the highest total carbonaceous aerosol emissions during the study period. Forest fires were prevalent in the northeastern states, while agricultural fires were prevalent in Gujarat, Chhattisgarh, Odisha, Madhya Pradesh, Bihar, Tripura, Uttar Pradesh, and Andhra Pradesh. The previous inventory, conducted at a coarser resolution (25 km × 25 km), overestimated open burning by 5 Mt. Our results were highly correlated with global bottom-up model values, especially the Fire Inventory (FINN). Our analysis showed that vegetative burning contributed 80.32% of the total carbon stock, with agricultural burning being the largest source of vegetative burning. Based on these findings, measures and strategies to control agricultural burning which would reduce significantly the total emissions of BC and OC with implications to improvement in air quality, human health and climate should be planned. [Display omitted] • Agricultural burning dominates carbonaceous aerosol emissions in India. • Shrublands exhibit the highest inter-annual carbon stock change in India. • North-eastern states of India are worst affected by wildfires. • In India, vegetation burning contributes to 80.32% of carbon stock. • Global bottom-up inventories showed higher regional emissions in India. [ABSTRACT FROM AUTHOR]

In Asia, the evaluation of black carbon (BC) using global aerosol-transport models has been incomplete due to a lack of available measurements. Recently, new measurements and datasets at various Asian sites have become available for use in model validation. In this study, we compared the BC mass concentrations obtained by an aerosol-coupled global nonhydrostatic model adopting a uniform-grid system with in-situ measurements and other models over Asia. The results revealed that our model, as well as other global models, was unable to reproduce the observed BC values at most sites in China and India, most likely due to strong local hotspots. To overcome the inconsistency between the models and measurements, we developed a new aerosol-transport model using a stretched-grid system for high-resolution simulations with up to approximately 10 km grids. Our model can be used as a global-to-regional seamless aerosol-transport model for low to high horizontal resolution simulations. [ABSTRACT FROM AUTHOR]

• eBC mass concentration continuously decreased throughout lock-down periods (LD1 to LD4). • During lockdown period the eBC mass concentration decreased by 35% as compared to 2017–2019 • The contributions of eBC ff and eBC wf are 70% and 30% respectively during lockdown. • Atmospheric forcing reduced by 25% during the pandemic year 2020 as compared to 2017–2019. A nationwide lockdown was imposed in India due to the Coronavirus Disease 2019 (COVID-19) pandemic which significantly reduced the anthropogenic emissions. We examined the characteristics of equivalent black carbon (eBC) mass concentration and its source apportionment using a multiwavelength aethalometer over an urban site (Ahmedabad) in India during the pandemic induced lockdown period of year 2020. For the first time, we estimate the changes in BC, its contribution from fossil (eBC ff) and wood (eBC wf) fuels during lockdown (LD) and unlock (UL) periods in 2020 with respect to 2017 to 2019 (normal period). The eBC mass concentration continuously decreased throughout lockdown periods (LD1 to LD4) due to enforced and stringent restrictions which substantially reduced the anthropogenic emissions. The eBC mass concentration increased gradually during unlock phases (UL1 to UL7) due to the phase wise relaxations after lockdown. During lockdown period eBC mass concentration decreased by 35%, whereas during the unlock period eBC decreased by 30% as compared to normal period. The eBC wf concentrations were higher by 40% during lockdown period than normal period due to significant increase in the biomass burning emissions from the several community kitchens which were operational in the city during the lockdown period. The average contributions of eBC ff and eBC wf to total eBC mass concentrations were 70% and 30% respectively during lockdown (LD1 to LD4) period, whereas these values were 87% and 13% respectively during the normal period. The reductions in BC concentrations were commensurate with the reductions in emissions from transportation and industrial activities. The aerosol radiative forcing reduced significantly due to the reduction in anthropogenic emissions associated with COVID-19 pandemic induced lockdown leading to a cooling of the atmosphere. The findings in the present study on eBC obtained during the unprecedented COVID-19 induced lockdown can provide a comprehensive understanding of the BC sources and current emission control strategies, and thus can serve as baseline anthropogenic emissions scenario for future emission control strategies aimed to improve air quality and climate. [ABSTRACT FROM AUTHOR]

Abstract: Black carbon (BC), which is one of the highly absorbing capacities of solar radiation, reduces albedo of atmospheric aerosol. BC along with fine particulate matters (PM2.5), which play crucial role in climate and health, was monitored online for an entire year of 2011 at an urban megacity of Delhi, situated in the northern part of India. Daily mass concentration of BC varies from 0.9 to 25.5μgm−3, with an annual mean of 6.7±5.7μgm−3 displayed clear monsoon minima and winter maxima; however, PM2.5 concentration was ranging from 54.3 to 338.7μgm−3, with an annual mean of 122.3±90.7μgm−3. BC typically peaked between 0800 and 1000 LST and again between 2100 and 2300 LST, corresponding to the morning and evening traffic combined with the ambient meteorological effect. During summer and monsoon, the BC concentrations were found less than 5μgm−3; however, the highest concentrations occurred during winter in segments from <5 to >10μgm−3. In over all study, the BC mass concentration was accounted for ~6% of the total PM2.5 mass, with a range from 1.0% to 14.3%. The relationship between meteorological parameters and BC mass concentrations was studied and a clear inverse relationship (r=−0.53) between BC and wind speed was observed. Relation between visibility and BC mass concentrations was also significantly negative (−0.81), having relatively higher correlation during post-monsoon (−0.85) and winter (−0.78) periods and lower during summer (−0.45) and monsoon (−0.54) periods. The mixed layer depths (MLDs) were found to be shallower during post monsoon (379m) and winter (335m) as compared during summer (1023m) and monsoon (603m). The study indicated that during post-monsoon season, the impact of biomass burning is higher as compared to combustion of fossil fuels. Results are well associated with the rapid growth of anthropogenic emissions and ambient meteorological conditions over the station. [Copyright &y& Elsevier]

In this study, temporal variations of surface ozone (O3) were investigated at tropical urban site of Hyderabad during the year 2009. O3, oxides of nitrogen (NOx = NO + NO2), black carbon (BC), and meteorological parameters were continuously monitored at the established air monitoring station. Results revealed the production of surface O3 from NO2 through photochemical oxidation. Averaged datasets illustrated the variations in ground-level concentrations of these air pollutants along different time scales. Maximum mean concentrations of O3 (56.75 ppbv) and NOx (8.9 ppbv) were observed in summer. Diurnal-seasonal changes in surface O3 and NOx concentrations were explicated with complex atmospheric chemistry, boundary layer dynamics, and local meteorology. In addition, nocturnal chemistry of NOx played a decisive role in the formation of O3 during day time. Mean BC mass concentration in winter (10.92 µg m−3) was high during morning hours. Heterogeneous chemistry of BC on O3 destruction and NOx formation was elucidated. Apart from these local observations, long-range transport of trace gases and BC aerosols were evidenced from air mass back trajectories. Further, statistical modeling was performed to predict O3 using multi-linear regression method, which resulted in 91% of the overall variance. [ABSTRACT FROM AUTHOR]

Abstract: We carried out an analysis of black carbon (BC) surface mass concentration, its radiative effects, and sources of origin in an urban atmosphere in east India, during winter season, through ground-based measurements and application of modelling tools. BC surface mass concentration exhibited diurnal variation with their higher values and a larger variability during evening to early morning hours than during daytime (1100–1600h, Local Time, LT) hours. Daytime mean surface BC mass concentration and BC mass fraction in total aerosol (size range 0.23–20μm) and in submicronic aerosol (size range 0.23–1μm) during the study period, corresponding to the well-mixed atmospheric layer were 11μgm−3, 3–10%, and 9–16% respectively. The mean BC optical depth (BC-AOD) and BC-AOD fraction at 0.5μm were estimated in an optical model as 0.11 and 13% respectively. Mean shortwave aerosol radiative forcing due to BC at top-of-atmosphere (TOA) during the study period was found to be +0.94Wm−2, which is about 59% the global mean radiative forcing due to carbon-dioxide gases. Estimates from BC simulations in a general circulation model showed BC surface concentration and BC optical depth in east India are primarily attributed to emissions from biofuel and fossil fuel combustion. Most of BC surface concentration (95%) and BC optical depth (60%) are contributed by emissions arising from the Indo-Gangetic plain (IGP) but there is a significant influence to BC columnar loading through elevated transport channels attributed mainly to emissions from open biomass burning from distant regions outside IGP. [Copyright &y& Elsevier]

Abstract: The present study addresses the role of black carbon (BC) in aerosol radiative forcing (ARF) over western India, where the Thar Desert produces large amount of dust aerosols during premonsoon season (Mar–May) and its mixing with BC makes the investigation a real challenge. Measurements of aerosol physical and optical parameters were carried out at three stations, Ahmedabad (urban area), Udaipur (semi-arid region) and Mt. Abu (a hill-top representing background conditions), to investigate the regional variation of ARF during April 2007. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) measurements show presence of dust layer in the altitude region from 1 to 5km over western India throughout the month leading to uniform distribution of dust. Ahmedabad has slightly higher AOD500(0.31) due to production of anthropogenic aerosols with BC concentration of 1.8μg.m−3 at surface, followed by Udaipur (AOD500 =0.30 and BC=0.9μg.m−3) and Mt. Abu (0.28 and 0.7μg.m−3, respectively). The longwave ARF is found to be similar over all three stations whereas the shortwave ARF depends on type of location. The shortwave ARF at the top of atmosphere (TOA), surface, and within the atmosphere are found to be 1.7, −46 and 47.7Wm−2, respectively, at Ahmedabad, −1.5, −35 and 33.5Wm−2 at Udaipur and −1.5, −31 and 29.5Wm−2 at Mt. Abu. On the other hand, the heating rates in the lower atmosphere (up to 5km) are 1.3, 1.0 and 0.4K/day over Ahmedabad, Udaipur and Mt. Abu, respectively. Sensitivity analysis shows that a 40% enhancement of BC could increase the heating rate by up to 50% over western India. Higher aerosol-induced heating in the atmosphere during premonsoon may have a large impact on the regional climate dynamics and hydrological processes. [Copyright &y& Elsevier]

Abstract: Concentrations of air pollutants from vehicles are elevated along roadways, indicating that human exposure in transportation microenvironments may not be adequately characterized by centrally located monitors. We report results from ∼180 h of real-time measurements of fine particle and black carbon mass concentration (PM2.5, BC) and ultrafine particle number concentration (PN) inside a common vehicle, the auto-rickshaw, in New Delhi, India. Measured exposure concentrations are much higher in this study (geometric mean for ∼60 trip-averaged concentrations: 190 μg m−3 PM2.5, 42 μg m−3 BC, 280 × 103 particles cm−3; GSD ∼1.3 for all three pollutants) than reported for transportation microenvironments in other megacities. In-vehicle concentrations exceeded simultaneously measured ambient levels by 1.5× for PM2.5, 3.6× for BC, and 8.4× for PN. Short-duration peak concentrations (averaging time: 10 s), attributable to exhaust plumes of nearby vehicles, were greater than 300 μg m−3 for PM2.5, 85 μg m−3 for BC, and 650 × 103 particles cm−3 for PN. The incremental increase of within-vehicle concentration above ambient levels—which we attribute to in- and near-roadway emission sources—accounted for 30%, 68% and 86% of time-averaged in-vehicle PM2.5, BC and PN concentrations, respectively. Based on these results, we estimate that one’s exposure during a daily commute by auto-rickshaw in Delhi is as least as large as full-day exposures experienced by urban residents of many high-income countries. This study illuminates an environmental health concern that may be common in many populous, low-income cities. [Copyright &y& Elsevier]

Abstract: In the present study, collocated and simultaneous data on spectral aerosol optical depth (AOD), mass concentration and size distribution of near-surface composite aerosols and black carbon aerosol mass concentrations were obtained from Microtops-II Sunphotometer, Quartz Crystal Microbalance (QCM) and Aethalometer, respectively, over an urban location, Tirupati (India) in the month of May 2009. The mean AOD at 500nm and Ångström parameters (α, β) during this period were obtained as 0.64±0.13 and 0.89±0.24, 0.36±0.10, respectively. The total surface aerosol mass concentration varied from 13 to 60μgm−3 out of which coarse mode dominated by 39%. The mean value of total mass concentration of aerosols was 23.80±0.25μgm−3. The Ångström wavelength exponent (α) showed a positive correlation of 0.60 with the near-surface fine-mode fraction. The total mass concentration showed positive and negative correlations of 0.72 and 0.68 with air temperature and relative humidity, respectively. Along with this, the diurnal variation of black carbon aerosol concentration varied from 2 to 14μgm−3 and observed prominently a sharp fumigation peak at around 07:00–09:00h and the nocturnal peak between 20:00 and 22:00h with a low value in afternoon hours (15:00h) with a mean BC mass concentration of 3.76±0.23μgm−3. A scatter plot between BC mass concentration (M b ) and total surface mass concentration (M t ) showed significant positive correlation of 0.73 and was used to estimate mean mass fraction (F BC ) for the study period, which was found to be 8.1±0.5%. [Copyright &y& Elsevier]

Abstract: Two important festival events were selected to assess their impacts on atmospheric chemistry by understanding settling velocity and emission time of aerosols. Using high volume sampler, aerosols were collected in a sequential manner to understand settling velocity and emission time of aerosols on a particular day. Composition and total suspended particulate load of the aerosols collected during the festivals were used as markers for strengthening the assessment. Terminal settling velocity of the aerosols were calculated using morphological and elemental compositional data, obtained from scanning electron microcopy (SEM) and energy dispersive X-ray (EDX) study. Aerosol load, black carbon, aromatic carbon and terminal velocity calculations were correlated to obtain conclusion that aerosols collected on the festival day might have been emitted prior to the festival. Settling time of aerosols collected on 17th and 19th October’09 during Diwali were found to be 36.5 (1.5 days) and 12.8 h, respectively. Carbon concentration estimated using EDX was found to be almost double in the sample collected after 2 days of the festival event. This strengthens our inference of time calculation where carbon with high concentration of load must have settled approximately after two days of the event. Settling time of aerosols collected on Holi morning and afternoon was found to be 1.7 and 24.8 h, respectively. Further, because of the small distance of 5.4 km between the meteorological station and sampling site, observed TSP values were compared with theoretical load values, calculated by using visibility values taken from the meteorological data. And it was found that both experimental and calculated values are close to each other about 50% of the times, which proves the assumption that experimental and meteorological data are comparable. [Copyright &y& Elsevier]