Particulate matter (PM) emissions, which affect the Earth's climate, human health, and visibility, often accompany greenhouse gas (GHG) emissions. Atmospheric PM plays an important role in the global climate system through modifications of the global radiation budget, directly by scattering and absorption of radiation and indirectly by the modification of cloud properties. Direct and indirect climate forcing by atmospheric PM constitutes the largest uncertainty in current predictions of climate change. While aerosol organic carbon (OC) contributes to cooling through light scattering, black or elemental carbon (BC or EC) absorbs light that leads to global warming. BC and OC nearly always accompany each other in PM emissions from incomplete combustion of carbon-containing fossil and biomass fuels. Including the direct and indirect effects of BC into global- and regional-scale climate models requires accurate BC emission inventories and conversion factors that translate BC concentration into light absorption coefficients for different wavelengths.
The first phase of this study evaluated methods for measuring BC and light absorption. The goals of this Phase included: 1) critically review the literature on carbon analysis methods and comparisons; 2) create carbon analysis QA/QC methods and plans; 3) conduct laboratory inter-comparison experiments of OC, EC, BC, and light absorption (babs) measurement methods; and 4) perform a field comparison of different measurement methods for babs, BC, EC, and OC at the Fresno Supersite. The second phase of the study evaluated global and regional BC inventories and approaches for constructing a BC inventory for California. This study assembled existing profiles into a documented database, which can serve as a starting point for ARB to build on its PM2.5 emission inventory effort by coupling relevant source profiles containing BC/EC and OC abundances with its inventory system. This project has resulted in an improved understanding of the effect of different combustion sources and their particle emissions, in particular BC and OC, on air pollution and climate change.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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