Impacts of brown carbon from biomass burning on surface UV and ozone photochemistry in the Amazon Basin.
The spectral dependence of light absorption by atmospheric particulate matter has major implications for air quality and climate forcing, but remains uncertain especially in tropical areas with extensive biomass burning. In the September-October 2007 biomass-burning season in Santa Cruz, Bolivia, we studied light absorbing (chromophoric) organic or "brown" carbon (BrC) with surface and space-based remote sensing. We found that BrC has negligible absorption at visible wavelengths, but significant absorption and strong spectral dependence at UV wavelengths. Using the ground-based inversion of column effective imaginary refractive index in the range 305-368 nm, we quantified a strong spectral dependence of absorption by BrC in the UV and diminished ultraviolet B (UV-B) radiation reaching the surface. Reduced UV-B means less erythema, plant damage, and slower photolysis rates. We use a photochemical box model to show that relative to black carbon (BC) alone, the combined optical properties of BrC and BC slow the net rate of production of ozone by up to 18% and lead to reduced concentrations of radicals OH, HO2, and RO2by up to 17%, 15%, and 14%, respectively. The optical properties of BrC aerosol change in subtle ways the generally adverse effects of smoke from biomass burning.
Department of Atmospheric and Oceanic Science (AOSC), University of Maryland, College Park, Maryland, USA.|Earth System Science Interdisciplinary Center (ESSIC), College Park, Maryland, USA.
Jungbin
J
Mok
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.
Nickolay A
NA
Krotkov
Finnish Meteorological Institute, Kuopio, Finland.
Antti
A
Arola
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.
Omar
O
Torres
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.|Universities Space Research Association, Columbia, Maryland, USA.
Hiren
H
Jethva
Laboratory for Atmospheric Physics, Institute for Physics Research, Universidad Mayor de San Andres, La Paz, Bolivia.
Marcos
M
Andrade
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.|Science Systems and Applications, Inc., Lanham, Maryland, USA.
Gordon
G
Labow
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.|Universities Space Research Association, Columbia, Maryland, USA.
Thomas F
TF
Eck
Department of Atmospheric and Oceanic Science (AOSC), University of Maryland, College Park, Maryland, USA.|Earth System Science Interdisciplinary Center (ESSIC), College Park, Maryland, USA.|State Laboratory of Earth Surface Process and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, Beijing, China.
Zhanqing
Z
Li
Department of Atmospheric and Oceanic Science (AOSC), University of Maryland, College Park, Maryland, USA.|Earth System Science Interdisciplinary Center (ESSIC), College Park, Maryland, USA.
Russell R
RR
Dickerson
Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Georgiy L
GL
Stenchikov
Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Sergey
S
Osipov
Department of Atmospheric and Oceanic Science (AOSC), University of Maryland, College Park, Maryland, USA.|NOAA Air Resources Laboratory, College Park, Maryland, USA.
Xinrong
X
Ren