Experimental Studies of the Factors Controlling the Water Nucleating Ability of Atmospheric Particulate MatterEPA Grant Number: GF9501349
Title: Experimental Studies of the Factors Controlling the Water Nucleating Ability of Atmospheric Particulate Matter
Investigators: Brechtel, Fredrick J.
Institution: Colorado State University
EPA Project Officer: Michaud, Jayne
Project Period: September 1, 1995 through January 1, 2000
Project Amount: $25,446
RFA: STAR Graduate Fellowships (1995) Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Earth
The purpose of this project is to: 1) measure the size dependent chemistry and size distribution of aerosol particles which are capable of acting as cloud condensation nuclei in cloudy and clear air conditions; 2) measure the size dependent chemistry and size distribution of aerosols which do not act as cloud condensation nuclei in cloudy and clear air conditions; 3) measure the ability of aerosols to act as cloud condensation nuclei at various cloud supersaturations; and 4) measure which chemical properties of aerosols determine their cloud condensation nuclei activity in order to evaluate the potential for anthropogenic sources of aerosols to alter cloud properties. The experiments will be conducted in both polluted and clean ambient conditions so that the properties which control the ability of aerosols to act as efficient cloud condensation nuclei may be defined under different ambient conditions. The specific approach used under this study includes developing one set of measurements by gathering only the cloud droplets within a cloud, separating by size, and evaporating the water from them to isolate and examine the physical and chemical properties of the remaining aerosol particles. The ability of various aerosol samples to act as cloud condensation nuclei at various cloud supersaturations will be measured with a cloud condensation nuclei spectrometer, and Transmission Electron Microscope and chemical analyses will investigate the effect of coatings on aerosols, or mixtures of different chemical species within the same particle, on their ability to act as cloud condensation nuclei. At the same time, measurements will be made on the chemical and physical properties of the aerosol within a cloud which do not nucleate cloud droplets for comparison with the cloud condensation nuclei. The size dependent chemical properties, size distribution, and total particle concentrations of the interstitial aerosols will be measured, and a cloud condensation nuclei spectrometer will be used to determine if the non-cloud condensation nuclei aerosol are capable of acting as cloud condensation nuclei at higher than ambient water supersaturations in order to examine their water nucleating properties.