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Jeffrey S. Gaffney Argonne National Laboratory 9700 S. Cass Avenue Argonne, IL 60439 Tel: 630-252-5178 Fax: 630-252-7415 email: gaffney@anl.gov The impacts on climate and radiative balance of aerosols depend on their tropospheric lifetimes, their compositions and sizes, and related optical properties. Carbonaceous aerosols are less hygroscopic than fine inorganic aerosols and therefore have potentially longer lifetimes. The ability of carbonaceous aerosols to take up water increases with time as the carbon surfaces are oxidized in the atmosphere. Currently, carbonaceous aerosols are treated in climate models as if their wet removal rates were similar to those for inorganic aerosols. A better understanding of the lifetimes and removal rates of carbonaceous aerosols is required to determine the overall impact of tropospheric aerosols on radiative balance. We are using natural radionuclide tracers, including 210Pb, 7Be, 40K, and 14C, to determine the lifetimes and sources of fine atmospheric aerosols, particularly the carbonaceous aerosols, in air samples size-fractionated by cascade impactors. As lead scientist for the ASP’s Megacity Aerosol Experiment in Mexico City (MAX-Mex), planned for February-March 2006. This effort will be collaborative with the Megacity Impacts on Regional and Global Environments (MIRAGE) study. MIRAGE (http://mirage-ex.acd.ucar.edu) is a project of the National Center for Atmospheric Research (NCAR) and the National Science Foundation (NSF). Future Accomplishments: In FY 2006 we will complete laboratory development of carbon separations and studies on the distribution and stability of radionuclides attached to carbonaceous soots. Our experiments on aging of soot use 7Be and 210Pb and daughters as tracers, with the oxidant ozone and ultraviolet light generating hydroxyl radical. In FY 2005 and FY 2006 we will lead and organize the MAX-Mex field study. MAX-Mex will focus on the export of aerosols and precursor pollutants from Mexico City and the effects on regional-scale air quality and climate, particularly measurement of black carbon aerosol effects and removal of black carbon by rainfall and aging processes (including changing hygroscopicity of the black carbon aerosols and secondary organic aerosols). We will continue to work with Mario and Luisa Molina and with ASP Science Team members toward collaboration with the MIRAGE study in Mexico City in February-March 2006 and will be completing a science plan for that effort. Preliminary plans are on the ASP web site (http://www.asp.bnl.gov/MAXMex. html). Relationships to Other Projects: Our field work will involve ground- and aircraft-based measurements and will entail collaboration on black carbon, organic, and secondary organic aerosols with Pacific Northwest and Brookhaven National Laboratories, other ASP participants, various organizations involved in the North American Research Strategy for Tropospheric Ozone, and organizations specific to the field study areas. Extensive interactions occur with MIT; the University of California, San Diego; the University of Chicago; New Mexico Tech in Socorro, New Mexico; the University of Illinois at Chicago; and other universities. We will also collaborate with Aerodyne Research, Inc., in the MAX-Mex 2006 effort. [back to ASP ST Membership] |