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Particles in the Atmosphere
Published in Stanley Manahan, Environmental Chemistry, 2017
A significant fraction of the atmospheric aerosol consists of organic carbon, largely produced by burning fossil fuels (especially coal) and biomass. Much of this carbonaceous particulate matter is now classified as brown carbon, which absorbs radiation uniformly from the ultraviolet into the infrared region of the spectrum.6 Brown carbon is especially prevalent in densely populated developing countries in which wood and other forms of biomass are extensively employed for cooking, heating, and energy utilization. Uncontrolled forest and savanna fires as well as smoldering fires employed for forest management, especially in the practice of slash-and-burn agriculture, produce large quantities of brown carbon. Volatile organic carbon emitted by plants, such as terpenes from some kinds of trees, also contributes to brown carbon.
Particles in the Atmosphere
Published in Stanley E. Manahan, Environmental Chemistry, 2022
A significant fraction of the atmospheric aerosol consists of organic carbon, largely produced by burning fossil fuels (especially coal) and biomass. Much of this carbonaceous particulate matter is now classified as brown carbon, which absorbs radiation uniformly from the ultraviolet into the infrared region of the spectrum.10
Evaluating the accuracy of absorbing aerosol optical properties measured using single particle cavity ring-down spectroscopy
Published in Aerosol Science and Technology, 2023
Jamie W. Knight, Andrew J. Orr-Ewing, Michael I. Cotterell
Important classes of absorbing aerosol in the atmosphere include black carbon (Ramanathan and Carmichael 2008), a carbonaceous product of incomplete combustion that absorbs strongly over the visible spectrum, and mineral dust, a broad term for aerosol particles containing minerals such as hematite (Moosmüller, Chakrabarty, and Arnott 2009). In addition, aerosol particles composed of light absorbing organic carbon species, also known as brown carbon (BrC), are widespread in the atmosphere. Large uncertainties in the radiative forcing of BrC, with estimates varying by a factor of ∼15 (Feng, Ramanathan, and Kotamarthi 2013; Lin et al. 2014), derive from the poor characterization of BrC optical properties and how these evolve over particle lifetime (Bikkina and Sarin 2019; Carter et al. 2021; Wu et al. 2021). Accurate and sensitive measurements of the evolving complex refractive indices for BrC aerosols are therefore required to reduce uncertainties in the representation of aerosol-light interactions in climate models.
Solvent effects on chemical composition and optical properties of extracted secondary brown carbon constituents
Published in Aerosol Science and Technology, 2022
Kunpeng Chen, Nilofar Raeofy, Michael Lum, Raphael Mayorga, Megan Woods, Roya Bahreini, Haofei Zhang, Ying-Hsuan Lin
Brown carbon (BrC) aerosols are light-absorbing organic aerosols that absorb tropospheric solar radiation in the near UV and shorter visible ranges. BrC aerosols are one of the main uncertainties in radiative forcing in the atmosphere. Previous model studies showed that the direct radiative effect of BrC absorption ranges from +0.10 to +0.55 W m−2 (Feng, Ramanathan, and Kotamarthi 2013; G. Lin et al. 2014; Zhang et al. 2020). The Community Atmosphere Model simulation also suggested that BrC may reduce the global coverage of low clouds and hence indirectly decrease the cooling effects of clouds (Brown et al. 2018). However, evaluation of BrC’s climate forcing is largely limited due to the absence of chromophores in the current models (Laskin, Laskin, and Nizkorodov 2015), which requires in-depth characterization of BrC constituents and their optical properties.
Complex refractive index, single scattering albedo, and mass absorption coefficient of secondary organic aerosols generated from oxidation of biogenic and anthropogenic precursors
Published in Aerosol Science and Technology, 2019
Justin H. Dingle, Stephen Zimmerman, Alexander L. Frie, Justin Min, Heejung Jung, Roya Bahreini
In recent studies, brown carbon (BrC) which is emitted directly from biomass burning or formed as SOA particles, has been recognized to play a role in climate forcing in addition to black carbon (BC). BC, which is also emitted through combustion processes and biomass burning, is made of graphene layers, and can absorb radiation in a broad range, from the ultraviolet region to the infrared region (Bond et al. 2013; Venkataraman et al. 2005). BrC absorbs radiation more strongly in the near ultraviolet to ultraviolet region, contributing to strongly wavelength dependent direct radiative forcing effects and is decribed as “colored” organic compounds consisting of polycyclic aromatic hydrocarbon (PAH) structures, with double bonds and rings, and humic-like substances branched with nitrated and oxidized functional groups (Laskin et al. 2015; Andreae and Gelencsér 2006; Ramanathan et al. 2007; Feng et al. 2013). Small PAHs and their derivatives, emitted from automobile and biomass burning, are typically found in the gas phase; however their photooxidation products can lead to SOA particles and BrC formation (Di Filippo et al. 2010; Wang et al. 2007; Samburova et al. 2016; Chan et al. 2009; Hersey et al. 2011; Claeys et al. 2012; Iinuma et al. 2010). For example, nitro-aromatics identified in the water soluble organic carbon samples in the Los Angeles basin have been shown to contribute to ∼4% of water soluble BrC absorption at near ultraviolet to ultraviolet region (Zhang et al. 2013). In recent studies, light absorption of primary BrC aerosol emitted from biomass burning fuels such as Alaskan and Siberian peat have also shown efficient absorption in wavelengths between 300 and 400 nm (Chakrabarty et al. 2016).