Carbonaceous aerosols (CA) strongly impact regional and global climate through their light-absorbing and scattering properties, yet their effects remain uncertain in dust-influenced regions. We investigated the optical properties, source contributions, and radiative impacts of CA at two climatically distinct regions in northwestern India: an arid region (AR, Jodhpur; post-monsoon) and a semi-arid region (SAR, Kota; winter). Mean absorption & Aring;ngstr & ouml;m exponent (AAE) values were comparable between the two regions (AR: 1.416 +/- 0.173; SAR: 1.395 +/- 0.069), but temporal cluster analysis revealed source-specific variability, with lower AAE during traffic-dominated periods (similar to 1.30) and elevated AAE during solid fuel and biomass combustion (1.68 in AR and 1.52 in SAR). While equivalent BC (eBC) levels were higher in AR with a relatively uniform liquid-fuel contribution (BClf = 80.06 +/- 1.98 %), the mass absorption cross- of BC (MAC(BC)) in SAR was similar to 4.5X greater, driven by local solid fuel combustion and transported biomass burning emissions (BCsf = 34.61 +/- 6.88 %). Mie modelling indicated higher SSA in AR due to higher contribution of mineral dust, in contrast to SAR, where carbonaceous aerosols caused stronger absorption, forward scattering, and higher imaginary refractive index (k(OBD)). Although absorption enhancement (E-lambda) was slightly higher in AR (similar to 1.11 vs. similar to 0.99), SAR aerosols nearly doubled the warming potential (Delta RFE), with RFE values of similar to 0.87 W/m(2) in SAR versus similar to 0.43 W/m(2) in AR. These findings highlight strong source-specific and site-specific variability in aerosol absorption and radiative, emphasizing the need to integrate region-specific parameters into climate models and air quality assessments for data-scarce arid and semi-arid South Asian environments.

Light-absorbing carbonaceous aerosols, comprising black carbon (BC) and brown carbon (BrC), significantly influence air quality and radiative forcing. Unlike traditional approaches that use a fixed value of absorption & Aring;ngstrom exponent (AAE), this study investigated the absorption and optical properties of carbonaceous aerosols in Beijing for both local emission and regional transport events during a wintertime pollution event by using improved AAE results that employs wavelength-dependent AAE (WDA). By calculating the difference of BC AAE at different wavelengths using Mie theory and comparing the calculated results to actual measurements from an Aethalometer (AE31), a more accurate absorption coefficient of BrC can be derived. Through the analysis of air mass sources, local emission was found dominated the pollution events during this study, accounting for 81 % of all cases, while regional transport played a minor role. Carbonaceous aerosols exhibited a continuous increasing trend during midday, which may be attributed to the re-entrainment of nighttime-accumulated carbonaceous aerosols to the surface during the early planetary boundary layer (PBL) development phase, as the mixed layer rises, combined with the variation of PBL and anthropogenic activity. At night, variations in the PBL height, in addition to anthropogenic activities, effectively contributed to surface aerosol concentrations, leading to peak surface aerosol values during local pollution episodes. The diurnal variation of AAE470/880 exhibited a decreasing trend, with a total decrease of approximately 12 %. Furthermore, the BrC fraction showed a constant diurnal variation, suggesting that the declining AAE470/880 was primarily influenced by BC, possibly due to enhanced traffic contributions.

Biomass burning is a major source of carbonaceous aerosols that significantly influences the Earth's radiation balance. However, the spectral light absorption properties of biomass burning aerosols (BBAs), particularly the contribution of brown carbon (BrC), remain poorly constrained due to reliance on laboratory measurements that may not accurately represent real-world atmospheric conditions. To address this limitation, we developed an unmanned aerial vehicle (UAV) based-platform for direct in-situ measurements of BBAs in the ambient atmosphere over the rural North China Plain. This approach reduces biases inherent to laboratory chamber experiments and enables a more realistic characterization of BBAs absorption properties. Our measurements revealed that the absorption & Aring;ngstr & ouml;m exponent (AAE) for typical residential biomass burning was 3.70 +/- 0.04 under smoldering conditions and 1.50 +/- 0.08 under flaming conditions. Variations in AAE were driven primarily by combustion conditions and smoke humidity rather than fuel type. Additionally, field-observed OC/EC ratios were up to ten times higher than those reported in laboratory chamber studies, resulting in systematically lower mass absorption cross-sections. This finding suggests that the BBAs light absorption and radiative forcing estimates in the North China Plain may be systematically overestimated by chamber-based studies. Notably, under smoldering conditions, BrC absorption at 375 nm was up to 6.6 times greater than that of black carbon (BC) once mass emissions are considered, emphasizing that strategies aiming at reducing smoldering combustion could be particularly effective in mitigating the ultraviolet radiative effects of BBAs. Our results demonstrate that ambient atmospheric measurements are essential for accurately constraining BBAs absorption properties and their climate impacts.

Carbonaceous aerosols play a crucial role in air pollution and radiative forcing, though their light-absorbing and isotopic characteristics remain insufficiently understood. This study analyzes optical absorption and isotopic composition in PM10 and PM2.5 particles from primary emission sources, focusing on traffic-related and solid fuel categories. We analyzed key optical properties, including the Angstrom absorption exponent (AAE), the contributions of black carbon (BC) and brown carbon (BrC) to total light absorption and the mass absorption efficiencies (MAE) of carbonaceous aerosols. AAE values were lower for traffic emission sources (0.9 to 1.3) than solid fuel emission sources (1.5 to 3), with similar values for both particle sizes. BrC contributions were more prominent at shorter wavelengths and were notably higher in solid fuel emission sources (61% to 88%) than in traffic emission sources (8% to 40%) at 405 nm. MAE values of BC at 405 nm were 2 to 20 times higher than BrC across different emissions. Particle size significantly affect MAE(BC) with PM2.5 higher when compared to PM10. Emissions from diesel concentrate mixer and raw coal burning exhibited the highest MAE(BC) for PM2.5 and PM10, respectively. Conversely, Coke had the lowest MAE(BC) but the highest MAE(BrC) for both sizes. Traffic emissions showed more stable carbon isotope ratios (delta C-13) enrichment (-29 parts per thousand to -24 parts per thousand) than solid fuels (-31 parts per thousand to -20 parts per thousand). delta C-13 of solid fuel combustion, unlike traffic sources, is found to be independent of size variation. These findings underscore the importance of source and size-specific aerosol characterization for unregulated emission sources.

This study investigates aerosol characteristics using ground-based measurements at two distinct regions, MohalKullu (31.9 degrees N, 77.12 degrees E; 1154 m amsl) and Kosi-Katarmal (29.64 degrees N, 79.62 degrees E; 1225 m amsl), from July 2019 to June 2022. The average Black Carbon (BC) concentrations were 1.5 f 1.0 mu g m- 3 at Mohal and 1.1 f 1.4 mu g m-3 at Katarmal. BC showed strong seasonal variability, with maxima during post-monsoon (2.6 f 1.0 mu g m- 3) and pre-monsoon (1.8 f 0.5 mu g m-3) seasons. The diurnal variation displayed distinct morning and evening peaks in all the seasons. High pre-monsoon AOD500 (0.30 f 0.06 to 0.54 f 0.08) and low values of & Aring;ngstrom exponent (0.67 f 0.10 to 0.95 f 0.30) indicated dominance of large particles, whereas lower AOD500 (0.21 f 0.07 to 0.25 f 0.03) in post-monsoon and winter, along with larger & Aring;ngstrom exponent (1.05 f 0.74 to 1.13 f 0.11), indicated smaller particles. Satellite-derived (OMI and MAIAC) AOD500 showed weak to moderate correlation with ground-based measurements at Mohal (R = 0.4639 for MAIAC, R = 0.1402 for OMI) and Katarmal (R = 0.3976 for MAIAC, R = 0.2980 for OMI). Using optical properties of aerosols and clouds (OPAC) and Santa Barbara discrete ordinate radiative transfer (SBDART) models, the short-wave aerosol radiative forcing (SWARF) was found negative at the surface and top of the atmosphere but positive in the atmosphere, suggesting significant surface cooling and atmospheric warming leading to high heating rates, respectively. Annual mean atmospheric radiative forcing was 27.36 f 6.00 Wm- 2 at Mohal and 21.87 f 7.26 Wm- 2 at Katarmal. These findings may have consequences for planning air pollution strategies and understanding the effects of regional climate change.

Aerosols are an important factor leading to reduced visibility. In order to better comprehend the connection between visibility and aerosols, aerosol optical depth (AOD) and Angstrom exponent (AE) data from the Himawari-8 Advanced Himawari Imager (AHI) are used for validation in comparison with the data from the Aerosol Robotic Network (AERONET) observations in this paper, which amounted to 69,026 sets of data. The results indicate that the AOD of AHI is in good agreement with AERONET observations, but AE performs poorly. The correlation coefficients between the AOD of AHI and AERONET data increase with decreasing visibility and the root mean square error increase. The AE of AHI performs poorly in different visibility conditions. The conclusion drawn from further analysis of the correlation between aerosol products and meteorological factors is that the factor with the highest correlation with visibility. Mixed aerosols dominate at higher visibility and biomass burning/urban-industrial aerosols dominate at lower visibility. The visibility in a typical city (Beijing) has a strong negative correlation with AOD, a weak negative correlation with AE, and a strong correlation with aerosol radiative forcing. The reduction in visibility may be caused by the scattering and adsorption effects of aerosols. The results are important for the improvement and application of AHI aerosol products in regional pollution studies.

We measured black carbon (BC) with a seven-wavelength aethalometer (AE-31) at the Nam Co Lake (NCL), the hinterland of the Tibetan Plateau (TP) from May 2015 to April 2016. The daily average concentration of BC was 145 +/- 85 ng m(-3), increasing by 50% since 2006. The seasonal variation of BC shows higher concentrations in spring and summer and lower concentrations in autumn and winter, dominated by the adjacent sources and meteorological conditions. The diurnal variation of BC showed that its concentrations peaked at 9:00-16:00 (UTC + 8), significantly related to local human activities (e.g., animal-manure burning and nearby traffic due to the tourism industry). The concentration-weighted trajectory (CWT) analysis showed that the long-distance transport of BC from South Asia could also be a potential contributor to BC at the NCL, as well as the biomass burning by the surrounding residents. The analyses of the absorption coefficient and absorption angstrom ngstrom exponent show the consistency of sourcing the BC at the NCL. We suggest here that urgent measures should be taken to protect the atmospheric environment at the NCL, considering the fast-increasing concentrations of BC as an indicator of fuel combustion.

We report measurements of the optical properties of methanol-soluble organic carbon (MSOC) and water-soluble organic carbon (WSOC) in the metropolitan city of Mumbai (19.01(degrees) N, 72.92(degrees) E), India. The MSOC and WSOC extracts were analysed using UV-visible spectroscopy. The study covered a period of nine months from September 2017 to May 2018. On average, MSOC constituted 30% and WSOC constituted 24% of the PM2.5 mass for the sampling period with peak concentration observed in the winter season. The absorption coefficients of MSOC were on average 1.57 times higher than WSOC for the sampling period. The absorption coefficients of MSOC and WSOC were correlated with the brown carbon absorption coefficients. Mass absorption cross- (MAC) was calculated by normalizing the absorption coefficients with its concentration, and the absorption angstrom exponent (AAE) was calculated by exponential fitting of the absorption coefficients. The MAC values for WSOC were estimated to be 1.03 +/- 0.39 m(2) g(-1), while for MSOC, it was 1.41 +/- 0.76 m(2) g(-1). The relative radiative forcing compared to black carbon was estimated at 10.1 +/- 5.2% and 6.3 +/- 3.8% for MSOC and WSOC, respectively.

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 & PLUSMN; 4.7 & mu;g m- 3, and the nighttime average (9.1 & PLUSMN; 6.1 & mu;g m- 3) was nearly double that of the daytime (5.8 & PLUSMN; 3.5 & mu;g m- 3). BC was most enhanced during winter, with mean concentration (14.3 & PLUSMN; 3.8 & mu;g 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 & PLUSMN; 0.31 km-1 in winter and lowest at 0.12 & PLUSMN; 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 & PLUSMN; 22 W m- 2) was estimated via the radiative transfer model SBDART, with an associated atmospheric heating rate of 1.02 K d-1.

Aerosols play an important role in the earth's environment across the globe through their involvement in various earth system cycles. The change in the aerosol properties may cause short and long-term impacts, the knowledge of such changes is useful in the estimation of the pollution sources of any region. We have carried out the analysis of the aerosols' optical and radiative properties using AERONET station data from 2018 to 2021 in Dibrugarh City. The higher Aerosol Optical Depth (AOD) values during winter and pre-monsoon months indicate high anthropogenic activities, and biomass burning in Dibrugarh. The impact of various sources and daily meteorological parameters help in understanding the diurnal variations of the AOD, Angstrom Exponent (AE), and column water (CW). Fine aerosol fractions dominate the aerosol volume, but sometimes the long-range transport of dust affects aerosol properties during pre-monsoon months (MAM). MODIS-derived AOD and AERONET AOD values show a good correlation, with R-2 = 0.68. The highest volume of the aerosols reaches up to 0.11 mu m(3) mu m(-2) during pre-monsoon months, whereas it lies below 0.05 mu m(3) mu m(-2) in other seasons. SSA values indicate the presence of scattering aerosols but in 2020, a sudden decline in the SSA values shows a strong rise in the absorbing aerosols. Throughout the study period (2018-2021), the positive radiative forcing indicates a rise in atmospheric heating.