Brown carbon

{{Short description|Brown smoke released by burning organic matter}} {{distinguish|black carbon}}

In chemistry, '''brown carbon''' ('''C<sub>brown</sub>/BrC''') is a brown smoke that is released by the combustion of organic matter. It coexists with black carbon when released to the atmosphere.<ref name=":1">{{Cite web|url=http://www.atmos-chem-phys.net/6/3131/2006/acp-6-3131-2006.pdf|title=Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols|last=Andreae|first=M. O.|date=28 July 2006}}</ref>

Black carbon is primarily released by high-temperature combustion and brown carbon is emitted mainly by biomass combustion. These two are the two most important light absorbing substances in the atmosphere. The climate and radiative transfer are highly impacted by the absorptive properties of these substances.<ref>{{Cite web|url=http://aerosols.univie.ac.at/research/black-and-brown-carbon-in-atmospheric-aerosols/|title=Aerosol Physics & Environmental Physics » Black and Brown Carbon in Atmospheric Aerosols|website=aerosols.univie.ac.at|language=en|access-date=2017-04-20}}</ref> Aircraft measurements of smoke plumes in the western U.S. have reported varying trends in BrC absorption, including enhancement, depletion, or no significant change.<ref>{{Cite journal |last1=Zeng |first1=Linghan |last2=Dibb |first2=Jack |last3=Scheuer |first3=Eric |last4=Katich |first4=Joseph M. |last5=Schwarz |first5=Joshua P. |last6=Bourgeois |first6=Ilann |last7=Peischl |first7=Jeff |last8=Ryerson |first8=Tom |last9=Warneke |first9=Carsten |last10=Perring |first10=Anne E. |last11=Diskin |first11=Glenn S. |last12=DiGangi |first12=Joshua P. |last13=Nowak |first13=John B. |last14=Moore |first14=Richard H. |last15=Wiggins |first15=Elizabeth B. |date=2022-06-21 |title=Characteristics and evolution of brown carbon in western United States wildfires |url=https://acp.copernicus.org/articles/22/8009/2022/ |journal=Atmospheric Chemistry and Physics |language=English |volume=22 |issue=12 |pages=8009–8036 |doi=10.5194/acp-22-8009-2022 |bibcode=2022ACP....22.8009Z |doi-access=free |issn=1680-7316}}</ref><ref>{{Cite journal |last1=Washenfelder |first1=R. A.|author1-link=Rebecca Washenfelder |last2=Azzarello |first2=L. |last3=Ball |first3=K. |last4=Brown |first4=S. S. |last5=Decker |first5=Z. C. J. |last6=Franchin |first6=A. |last7=Fredrickson |first7=C. D. |last8=Hayden |first8=K. |last9=Holmes |first9=C. D. |last10=Middlebrook |first10=A. M. |last11=Palm |first11=B. B. |last12=Pierce |first12=R. B. |last13=Price |first13=D. J. |last14=Roberts |first14=J. M. |last15=Robinson |first15=M. A. |date=2022 |title=Complexity in the Evolution, Composition, and Spectroscopy of Brown Carbon in Aircraft Measurements of Wildfire Plumes |url=https://onlinelibrary.wiley.com/doi/abs/10.1029/2022GL098951 |journal=Geophysical Research Letters |language=en |volume=49 |issue=9 |article-number=e2022GL098951 |doi=10.1029/2022GL098951 |bibcode=2022GeoRL..4998951W |issn=1944-8007}}</ref><ref>{{Cite journal |last1=Sullivan |first1=Amy P. |last2=Pokhrel |first2=Rudra P. |last3=Shen |first3=Yingjie |last4=Murphy |first4=Shane M. |last5=Toohey |first5=Darin W. |last6=Campos |first6=Teresa |last7=Lindaas |first7=Jakob |last8=Fischer |first8=Emily V. |last9=Collett Jr. |first9=Jeffrey L. |date=2022-10-18 |title=Examination of brown carbon absorption from wildfires in the western US during the WE-CAN study |url=https://acp.copernicus.org/articles/22/13389/2022/ |journal=Atmospheric Chemistry and Physics |language=English |volume=22 |issue=20 |pages=13389–13406 |doi=10.5194/acp-22-13389-2022 |bibcode=2022ACP....2213389S |doi-access=free |issn=1680-7316}}</ref><ref>{{Cite journal |last1=Shen |first1=Yingjie |last2=Pokhrel |first2=Rudra P. |last3=Sullivan |first3=Amy P. |last4=Levin |first4=Ezra J. T. |last5=Garofalo |first5=Lauren A. |last6=Farmer |first6=Delphine K. |last7=Permar |first7=Wade |last8=Hu |first8=Lu |last9=Toohey |first9=Darin W. |last10=Campos |first10=Teresa |last11=Fischer |first11=Emily V. |last12=Murphy |first12=Shane M. |date=2024-11-21 |title=Understanding the mechanism and importance of brown carbon bleaching across the visible spectrum in biomass burning plumes from the WE-CAN campaign |url=https://acp.copernicus.org/articles/24/12881/2024/ |journal=Atmospheric Chemistry and Physics |language=English |volume=24 |issue=22 |pages=12881–12901 |doi=10.5194/acp-24-12881-2024 |bibcode=2024ACP....2412881S |doi-access=free |issn=1680-7316}}</ref><ref>{{Cite journal |last1=Liu |first1=Xiaoxi |last2=Zhang |first2=Y. |last3=Huey |first3=L. G. |last4=Yokelson |first4=R. J. |last5=Wang |first5=Y. |last6=Jimenez |first6=J. L. |last7=Campuzano-Jost |first7=P. |last8=Beyersdorf |first8=A. J. |last9=Blake |first9=D. R. |last10=Choi |first10=Y. |last11=St. Clair |first11=J. M. |last12=Crounse |first12=J. D. |last13=Day |first13=D. A. |last14=Diskin |first14=G. S. |last15=Fried |first15=A. |date=2016 |title=Agricultural fires in the southeastern U.S. during SEAC4RS: Emissions of trace gases and particles and evolution of ozone, reactive nitrogen, and organic aerosol |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/2016JD025040 |journal=Journal of Geophysical Research: Atmospheres |language=en |volume=121 |issue=12 |pages=7383–7414 |doi=10.1002/2016JD025040 |issn=2169-8996|hdl=11603/18908 |hdl-access=free }}</ref> Therefore, the understanding of brown carbon and constraints for atmospheric simulation are critical for the accuracy of climate modeling.

== Overview == thumb|Low temperature Bonfire in Denmark releasing brown carbon aerosols into the atmosphere

=== Discovery === Light absorbing aerosols have become an interest of study because of its effects on atmospheric warming. While the function of black carbon created by biomass burning in relation to the warming of air has as of now been known, the lesser-known part of brown carbon has recently been discovered.<ref name=":0">{{Cite news|url=http://www.thehindu.com/sci-tech/energy-and-environment/IIT-team-tracks-brown-carbon%E2%80%99s-effect-on-atmospheric-warming/article16703349.ece|title=IIT team tracks brown carbon's effect on atmospheric warming|last=Prasad|first=R.|work=The Hindu|access-date=2017-04-10|language=en}}</ref>

==== Brown carbon aerosols ==== The way light reflects the brown carbon off, it causes the material to appear brown or yellow. In respect to soot carbon (as an aerosol called black carbon) these light reflecting particles are collectively called brown carbon, highlighting their optical properties.<ref name=":1" />

It was seen that particles from combustion or from residential coal usage can contain substantial amounts of brown carbon. This particulate matter appears light brown, and not black as would be expected for pure soot particles.<ref name=":1" />

== Effects ==

=== Influence on Earth's atmosphere === thumb|The Malibu fire looking southwest towards West Los Angeles. Santa Ana winds fuel the flames and blow the brown carbon filled smoke out to sea for milesAerosols are one of the most important contributors to climate change in the atmosphere. Many of the particles suspended in the atmosphere originate from a multitude of sources. Some of these sources are natural and some of them are man-made. Most aerosols reflect sunlight, and some also absorb it. A lot of these nanoparticles cause severe health effects in addition to climate effects. There are many human activities that produce these particles.<ref name=":2">{{Cite web|url=http://www.evs.anl.gov/research-areas/highlights/brown-carbon.cfm|title=Understanding Brown Carbon Aerosols and Their Role in Climate Change {{!}} Environmental Science (EVS) {{!}} Argonne National Laboratory|website=www.evs.anl.gov|language=en|access-date=2017-04-20}}</ref>

Black carbon particles (a component of soot) originating from combustion processes have been known for some time to absorb sunlight and warm the atmosphere, and pollution controls have been put into place to reduce their emissions and their effects.<ref name=":2" />

Brown carbon has attracted interest as a possible cause of climate change. This class of organic carbon, known for its brownish color, absorbs strongly in the ultraviolet wavelengths and less significantly going into the visible wavelengths. Types of brown carbon include tar materials from smoldering fires or coal combustion, breakdown products from biomass burning, a mixture of organic compounds emitted from soil, and volatile organic compounds given off by vegetation.<ref name=":2" /> The lifetime of brown carbon in the atmosphere can be longer than 23 hours with a recalcitrant fraction of 4 ± 2%, indicating its impact on climate.<ref>{{Cite journal |last1=Chen |first1=Jhao-Hong |last2=Puttu |first2=Uma |last3=Huynh |first3=Han N. |last4=Ahern |first4=Adam T. |last5=Ball |first5=Katherine |last6=Bates |first6=Kelvin H. |last7=Brock |first7=Charles A. |last8=Campos |first8=Teresa |last9=Coggon |first9=Matthew M. |last10=Crounse |first10=John D. |last11=de Gouw |first11=Joost |last12=DiGangi |first12=Joshua P. |last13=Diskin |first13=Glenn S. |last14=Gkatzelis |first14=Georgios I. |last15=Halliday |first15=Hannah S. |date=2025-08-19 |title=Atmospheric Evolution of Brown Carbon from Wildfires in North America |journal=Environmental Science & Technology |volume=59 |issue=32 |pages=17145–17159 |doi=10.1021/acs.est.5c09020 |pmid=40772467 |bibcode=2025EnST...5917145C |issn=0013-936X}}</ref>

== Black and brown carbon ==

=== Brown carbon in relation to black carbon === [[File:New Orleans Fire 2005-09-02.jpg|thumb|High temperature fire in New Orleans, after Hurricane Katrina, causing black carbon aerosols to be released in the atmosphere]]

Simulation models suggest that, brown carbon contributes about 19% of the total atmospheric absorption by aerosols, while 72% is attributed to black carbon and 9% is due to the coating effect of sulfate and organic aerosols on black carbon. It seems that brown carbon can play an important role in photochemistry and the hydrologic cycle, especially over regions dominated by biomass combustion. Therefore, brown carbon needs to be considered in global climate change simulations for a more accurate understanding.<ref name=":2" /> The relative fraction of carbonaceous aerosol emissions can be used to incorporate brown carbon into climate models.<ref>{{Cite journal |last1=Navinya |first1=C. |last2=Kapoor |first2=T. S. |last3=Anurag |first3=G. |last4=Venkataraman |first4=C. |last5=Phuleria |first5=H. C. |last6=Chakrabarty |first6=R. K. |title=Brownness of organics in anthropogenic biomass burning aerosols over South Asia |journal=Atmospheric Chemistry and Physics |volume=24 |issue=23 |pages=13285–13297 |year=2024 |doi=10.5194/acp-24-13285-2024 |bibcode=2024ACP....2413285N |doi-access=free |url=https://acp.copernicus.org/articles/24/13285/2024/ }}</ref>

=== Mixture of black and brown === Up to about 70% of light absorption is by black carbon. When Brown carbon is present independently, it has nearly 15% potential to warm the atmosphere by absorbing light.<ref name=":0" /> thumb|Most aerosols in the smoke of combustion are a mix of black and brown carbon. Sometimes this cannot be discerned with the naked eye.

== References == {{reflist}}

Category:Carbon