Weekly patterns of aerosol in the United States D. M. Murphy1, S. L. Capps1,2,*, J. S. Daniel1, G. J. Frost1,3, and W. H. White4 1Earth System Research Laboratory, Chemical Sciences Division, National Oceanic and Atmospheric Administration Boulder, CO 80305, USA 2Vanderbilt University, Nashville, TN 37240, USA 3Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, CO 80309, USA 4Crocker Nuclear Laboratory, University of California, Davis Davis, CA 95616, USA *now at: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
Abstract. Data from the Interagency Monitoring of Protected Visual Environments
(IMPROVE) network of aerosol samplers and NOAA monitoring sites are examined
for weekly cycles. At remote and rural sites, fine particle elemental
carbon, crustal elements, and coarse particle mass had pronounced (up to
20%) weekly cycles with minima on Sunday or Monday. Fine particle organic
carbon and mass had smaller amplitude cycles, also with Sunday or Monday
minima. There was no statistically significant weekly cycle in fine particle
sulfate despite a 5 to 15% weekly cycle in power plant SO2
emissions. Although results for nitrate may be more susceptible to sampling
artifacts, nitrate also showed a pronounced weekly cycle with an amplitude
similar to elemental carbon. The only species found with a weekend maximum
was Pb, probably from general aviation on weekends. Aerosol optical
properties at NOAA monitoring sites were consistent with the IMPROVE
chemical data, with significant weekly cycles in aerosol light absorption
but not light scattering. These results support a large role of diesel
emissions in elemental carbon aerosol over the entire United States and
suggest that a large fraction of the airborne soil dust is anthropogenic.
They also suggest that studies of weekly cycles in temperature, cloudiness,
precipitation, or other meteorological variables should look for causes more
in light-absorbing particles and possible ice nucleation by dust rather than
sulfate or total aerosol. There are also implications for personal exposure
and epidemiological studies of aerosol health effects.
Citation: Murphy, D. M., Capps, S. L., Daniel, J. S., Frost, G. J., and White, W. H.: Weekly patterns of aerosol in the United States, Atmos. Chem. Phys., 8, 2729-2739, doi:10.5194/acp-8-2729-2008, 2008.