Nature Scientific Reports publishes study on impacts of brown carbon from biomass burning

November 11, 2016
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For Immediate Release
November 11th, 2016
Contacts: Catherine OBrien Stephens, csteph5@umd.edu

COLLEGE PARK, MD – A new study from scientists Jungbin Mok and Zhanqing Li, Earth System Science Interdisciplinary Center (ESSIC) University of Maryland, and Nickolay Krotkov, NASA Goddard Space Flight Center, is focusing on the impacts of brown carbon from biomass burning on ultraviolet (UV) radiation and atmospheric pollutants, which could lead to improved air quality models and help ameliorate potential health hazards such as suppression of the immune system and skin cancer. The paper is being released in Nature Scientific Reports on 11 November 2016. The spectral dependence of light absorption by atmospheric particulate matter (PM) in the UV wavelengths has major implications for air quality and health studies but remains highly uncertain. The PM absorption in areas downwind of extensive biomass burning (e.g. , forest fires and agricultural burning) is dominated by Black Carbon (BC), but the contribution by the light absorbing component of the accompanying organic carbon known as “brown carbon” (BrC) is highly uncertain and typically neglected in chemical and aerosol transport models.

Currently, the Aerosol Robotic Network (AERONET) provides field measurements of aerosol absorption from the visible wavelengths that are used to infer BC in the atmosphere. However, this new method of measurement adding UV wavelengths allows for BrC to be directly observed in addition to BC. This represents the first effort to separate effects of gaseous (ozone and NO₂) and aerosol absorption and partition black and brown carbon absorption in the biologically important UV-B wavelengths in a field experiment. The measurements allow scientists to isolate the effect of BrC absorption on photolysis rates significant for atmospheric photochemistry and ozone production.

This new method of measuring “Black” and “Brown” carbon optical properties in the Visible and UV spectrum will allow improvement in air chemistry models that are used in predicting health and biomass hazards. Although the study was conducted in the Amazon Basin, the method can be used elsewhere, for example, in California and the western U.S. to examine the effects on human health and plant production from the amount of BrC detected. One positive effect of increased BrC is that it acts as a natural sunscreen to damaging UV-B wavelengths (e.g., ~305-310nm) that are present under clear sky and unpolluted conditions. While the absorption of UV-B radiation seen for BrC can alleviate some of the adverse health effects of smoke, biomass burning aerosols still remain as major environmental and health hazards. However, this new method of measuring key emission pollutants in the UV spectrum will improve the photochemical and air quality models needed to better adapt to the changing climate.

The technique will also help validate global satellite UV aerosol retrievals from the current Ozone Monitoring Instrument (OMI) UV spectrometer on board NASA’s Earth Observing System Aura satellite (https://aura.gsfc.nasa.gov/) and the future atmospheric composition missions, such as the NASA’s Pre-Aerosol, Clouds, and ocean Ecosystem (PACE) mission (https://science.nasa.gov/missions/pace ), ESA’s Sentinel 5 Precursor (http://www.tropomi.eu/ ) and Geostationary Satellite Constellation for Observing Global Air Quality (http://ceos.org/ourwork/virtual-constellations/acc/ ).