Author
Archita Rana
Other affiliations: Indian Institute of Science Education and Research, Kolkata
Bio: Archita Rana is an academic researcher from Indian Institute of Science. The author has contributed to research in topics: Angstrom exponent & Aerosol. The author has an hindex of 4, co-authored 7 publications receiving 81 citations. Previous affiliations of Archita Rana include Indian Institute of Science Education and Research, Kolkata.
Papers
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TL;DR: A comprehensive review of black carbon measurements in India from a survey of >140 studies spanning 2002-2018 is presented in this paper, where the authors identify key areas for improvement, such as the need for long-term BC monitoring networks, especially in regions where estimated emissions are high but measurement coverage is low; the general lack of understanding, despite some recent reports, of BC aerosol mixing states, aging and direct climate effects in the Indian context; the need to shift from qualitative approaches of BC source apportionment to robust quantitative measures; and the prospects for coupled chemical-opt
67 citations
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TL;DR: Children are comparatively more vulnerable than adults to HM exposure, with the ingestion exposure pathway dominating over dermal contact and inhalation, according to cumulative hazard index (HI) and incremental lifetime cancer risk (ILCR).
40 citations
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TL;DR: Measurements of aerosol black carbon and aqueous and methanol-extractable brown carbon from a receptor location in the eastern Indo-Gangetic Plain under two aerosol regimes: the photochemistry-dominated summer and biomass burning post-monsoon and the BB regime are reported.
28 citations
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TL;DR: Spectroscopic compositional analysis of brown carbon (BrC) and humic-like substances (HULIS) in the Indian context under varying conditions of source emissions and atmospheric processing uncover a complex interplay of emissions and Atmospheric processing of carbonaceous aerosols in the IGP.
21 citations
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TL;DR: In this paper, the authors reported the first characterization of the aerosol brown carbon composition in the Indian context using excitation emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor (PARAFAC) analysis.
Abstract: We report the first characterization of the aerosol brown carbon (BrC) composition in the Indian context using excitation emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor (PARAFAC) analysis. We find that biomass burning (BB)-dominated wintertime aerosols in the Indo-Gangetic Plain (IGP) outflow are characterized by two humic-like (HULIS) (C1_aq and C2_aq) and one protein-like/fossil fuel-derived (C3_aq) component for aqueous-extractable BrC (BrCaq), and by one humic-like (C1_me) and one protein-like (C2_me) component for methanol-extractable BrC (BrCme). Strong correlations of the BB tracer nss-K+ with C1_aq and C2_aq (r = 0.75–0.84, p < 0.01) and C1_me (r = 0.77, p < 0.01) point towards the BB-dominated IGP outflow as the major source. This is also supported by the analysis of fluorescence indices, which suggest extensive humification of BB emissions during atmospheric transport. The HULIS components correlate significantly with BrC absorption (r = 0.85–0.94, p < 0.01), and contribute substantially to the BrC relative radiative forcing of 13–24% vis-a-vis elemental carbon (EC). There is strong evidence that the abundant BB-derived NOX leads to NO3− formation in the IGP plume and drives the formation of water-soluble nitroaromatics (NACs) that constrain BrCaq light absorption (r = 0.56, p < 0.01) to a considerable degree. Overall, the study uncovers complex atmospheric processing of the IGP outflow in winter, which has important implications for regional climate.
4 citations
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01 Dec 2007
TL;DR: In this article, the authors examined absorption spectra of primary organic carbon (OC) emitted from solid fuel pyrolysis and found that more than 92% was extractable by methanol or acetone compared with 73% for water and 52% for hexane.
Abstract: Abstract. Carbonaceous aerosols affect the radiative balance of the Earth by absorbing and scattering light. While black carbon (BC) is highly absorbing, some organic carbon (OC) also has significant absorption, especially at near-ultraviolet and blue wavelengths. To the extent that OC absorbs visible light, it may be a non-negligible contributor to positive direct aerosol radiative forcing. Quantification of that absorption is necessary so that radiative-transfer models can evaluate the net radiative effect of OC. In this work, we examine absorption by primary OC emitted from solid fuel pyrolysis. We provide absorption spectra of this material, which can be related to the imaginary refractive index. This material has polar character but is not fully water-soluble: more than 92% was extractable by methanol or acetone, compared with 73% for water and 52% for hexane. Water-soluble OC contributes to light absorption at both ultraviolet and visible wavelengths. However, a larger portion of the absorption comes from OC that is extractable only by methanol. Absorption spectra of water-soluble OC are similar to literature reports. We compare spectra for material generated with different wood type, wood size and pyrolysis temperature. Higher wood temperature is the main factor creating OC with higher absorption; changing wood temperature from a devolatilizing state of 210 °C to a near-flaming state of 360 °C causes about a factor of four increase in mass-normalized absorption at visible wavelengths. A clear-sky radiative transfer model suggests that, despite the absorption, both high-temperature and low-temperature OC result in negative top-of-atmosphere radiative forcing over a surface with an albedo of 0.19 and positive radiative forcing over bright surfaces. Unless absorption by real ambient aerosol is higher than that measured here, it probably affects global average clear-sky forcing very little, but could be important in energy balances over bright surfaces.
446 citations
01 Dec 2013
TL;DR: Comparison with literature studies suggests that under typical polluted conditions the effect of NOx on SOA absorption is small, and SOA may contribute significantly to atmospheric BrC, with the magnitude dependent on both precursor type and oxidation level.
Abstract: Brown carbon (BrC), which may include secondary organic aerosol (SOA), can be a significant climate-forcing agent via its optical absorption properties. However, the overall contribution of SOA to BrC remains poorly understood. Here, correlations between oxidation level and optical properties of SOA are examined. SOA was generated in a flow reactor in the absence of NOx by OH oxidation of gas-phase precursors used as surrogates for anthropogenic (naphthalene, tricyclo[5.2.1.02,6]decane), biomass burning (guaiacol), and biogenic (α-pinene) emissions. SOA chemical composition was characterized with a time-of-flight aerosol mass spectrometer. SOA mass-specific absorption cross sections (MAC) and refractive indices were calculated from real-time cavity ring-down photoacoustic spectrometry measurements at 405 and 532 nm and from UV–vis spectrometry measurements of methanol extracts of filter-collected particles (300 to 600 nm). At 405 nm, SOA MAC values and imaginary refractive indices increased with increasin...
217 citations
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01 Jan 2020
203 citations
01 Dec 2010
TL;DR: In this article, the authors use the adjoint of the GEOS-Chem model to identify the location from which black carbon (BC) arriving at a variety of locations in the Himalayas and Tibetan Plateau originates, and calculate its direct and snow-albedo radiative forcing.
Abstract: . The remote and high elevation regions of central Asia are influenced by black carbon (BC) emissions from a variety of locations. BC deposition contributes to melting of glaciers and questions exist, of both scientific and policy interest, as to the origin of the BC reaching the glaciers. We use the adjoint of the GEOS-Chem model to identify the location from which BC arriving at a variety of locations in the Himalayas and Tibetan Plateau originates. We then calculate its direct and snow-albedo radiative forcing. We analyze the seasonal variation in the origin of BC using an adjoint sensitivity analysis, which provides a detailed map of the location of emissions that directly contribute to black carbon concentrations at receptor locations. We find that emissions from northern India and central China contribute the majority of BC to the Himalayas, although the precise location varies with season. The Tibetan Plateau receives most BC from western and central China, as well as from India, Nepal, the Middle East, Pakistan and other countries. The magnitude of contribution from each region varies with season and receptor location. We find that sources as varied as African biomass burning and Middle Eastern fossil fuel combustion can significantly contribute to the BC reaching the Himalayas and Tibetan Plateau. We compute radiative forcing in the snow-covered regions and find the forcing due to the BC induced snow-albedo effect to vary from 5–15 W m−2 within the region, an order of magnitude larger than radiative forcing due to the direct effect, and with significant seasonal variation in the northern Tibetan Plateau. Radiative forcing from reduced snow albedo likely accelerates glacier melting. Our analysis may help inform mitigation efforts to slow the rate of glacial melt by identifying regions that make the largest contributions to BC deposition in the Himalayas and Tibetan Plateau.
192 citations
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TL;DR: In the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) as mentioned in this paper, particle-phase organic carbon (OC) was quantified using Fourier transform infrared (FTIR) transmission spectroscopy.
Abstract: Atmospheric submicron particles were collected on Teflon filters downstream of a three-stage concentrator aboard the National Center for Atmospheric Research C-130 aircraft near Japan during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia). Particle-phase organic carbon (OC) was quantified using Fourier transform infrared (FTIR) transmission spectroscopy. Silicate, carbonate, alkane, alkene, aromatic, alcohol, carbonyl, amine, and organosulfate functional groups were identified and separated with a four-solvent rinsing procedure. X-ray fluorescence identified elemental composition. Total OC constructed from FTIR measurements agreed with simultaneous thermal-optical OC measurements with a slope of 0.91 and an R value of 0.93. OC varied from 0.4 to 14.2 μg m -3 , and organic mass varied from 0.6 to 19.6 μg m -3 , representing on average 36% of the identified submicron aerosol mass. Measured carbon monoxide (CO) to OC slopes illustrate 10 groups of air from regions described by an Asian emissions inventory. The CO/OC slope is used to compare sources and their influence on organic composition. Fifty-two percent of ACE-Asia samples have CO/OC slopes indicative of biomass combustion. Unitless CO/OC slopes above 15 are associated with increased fractions of alcohol groups, unsaturated C-H groups, and inorganic nitrate. Increased carbonyl carbon fractions in air originating over northern Asia are consistent with secondary OC formation. Case studies in the boundary layer demonstrate that aerosol compositions downwind of large Asian aerosol sources show clear regional composition signatures.
138 citations