Physico-Chemistry of Carbonaceous Aerosol Pollution in Evolving Cities

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Carbonaceous aerosols (organic and black carbon) remain a major unresolved issue in atmospheric science, especially in urban centers, where they are one of the dominant aerosol constituents and among most toxic to human health. The challenge is twofold: first, our understanding of the sources, sinks and physico-chemical properties of the complex mixture of carbonaceous species is still incomplete; and second, the representation of urban heterogeneities in air quality models is inadequate as they are designed for regional applications. The CARB-City project proposes the development of an innovative modeling framework that will address both issues by combining molecular-level chemical constraints and city-scale modeling to achieve the following objectives: (WP1) to develop and apply new chemical parameterizations, constrained by an explicit chemical model, for carbonaceous aerosol formation from urban precursors, and (WP2) to examine whether urban heterogeneities in sources and mixing can enhance non-linearities in chemistry of carbonaceous compounds and modify their predicted composition. The new modeling framework will then be applied (WP3) to quantify the contribution of traditional and emerging urban aerosol precursor sources to chemistry and toxicity of carbonaceous aerosols; and (WP4) to assess the effectiveness of greener-city strategies in removing aerosol pollutants. This work will enhance fundamental scientific understanding as to how key physico-chemical processes control the lifecycle of carbonaceous aerosols in cities, and will improve the predictability of air quality models in terms of composition and toxicity of urban aerosols, and their sensitivity to changes in energy and land use that cities are currently experiencing. The modeling framework will have the required chemical and spatial resolution for assessing human exposure to urban aerosols. This will allow policy makers to optimize urban emission reductions and sustainable urban development.