Meteorological associations with aerosol composition in the boundary layer

Abstract

The associations of meteorological parameters with aerosol elemental concentrations in the boundary layer have been studied with measurements obtained at the Boulder Atmospheric Observatory from November 29 to December 6, 1979. Air motions were documented by measurements at the tower up to 300 meters and by regional weather data. Aerosols were sampled at 4, 9, 23, and 49 meters by particle size selective cascade impactors and by time sequence filter samplers and were analyzed by proton induced X ray emission (PIXE). Principal sources of fine particle (<1 μ m aerodynamic diameter) components were automotive emissions for Pb and Br and tall stack emissions and atmospheric conversion of pollution gases to sulfate for S. In coarse particles the major earth crustal elements Al, Si, K, Ca, and Fe were soil derived. Pb and Br concentrations and the ratio Br/Pb generally decreased with height. Also, these concentrations varied with ventilation and vertical mixing and were greatest during southerly air flow from Denver. S concentrations did not generally vary with height, ventilation, vertical mixing, or wind direction, suggesting long‐range transport, although 10‐fold temporal variations were observed. Crustal element concentrations generally decreased with height but depended in part on sampler position on the tower structure, indicating microscale shielding effects of coarse particles which were not observed for fine particle elements. Temporal variations of all elements were associated with major meteorological changes, including a cold front passage and a chinook wind.