Weekly patterns of aerosol in the United States

[摘要] Data from the Interagency Monitoring of Protected Visual Environments(IMPROVE) network of aerosol samplers and NOAA monitoring sites are examinedfor weekly cycles. At remote and rural sites, fine particle elementalcarbon, crustal elements, and coarse particle mass had pronounced (up to20%) weekly cycles with minima on Sunday or Monday. Fine particle organiccarbon and mass had smaller amplitude cycles, also with Sunday or Mondayminima. There was no statistically significant weekly cycle in fine particlesulfate despite a 5 to 15% weekly cycle in power plant SO₂emissions. Although results for nitrate may be more susceptible to samplingartifacts, nitrate also showed a pronounced weekly cycle with an amplitudesimilar to elemental carbon. The only species found with a weekend maximumwas Pb, probably from general aviation on weekends. Aerosol opticalproperties at NOAA monitoring sites were consistent with the IMPROVEchemical data, with significant weekly cycles in aerosol light absorptionbut not light scattering. These results support a large role of dieselemissions in elemental carbon aerosol over the entire United States andsuggest 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 morein light-absorbing particles and possible ice nucleation by dust rather thansulfate or total aerosol. There are also implications for personal exposureand epidemiological studies of aerosol health effects.

[学科分类] 大气科学