Ion-Induced Nucleation of Atmospheric AerosolsEPA Grant Number: R829620
Title: Ion-Induced Nucleation of Atmospheric Aerosols
Investigators: McMurry, Peter H. , Eisele, Fred
Institution: University of Minnesota
EPA Project Officer: Carleton, James N
Project Period: January 1, 2002 through December 31, 2004 (Extended to December 31, 2005)
Project Amount: $400,000
RFA: Exploratory Research: Nanotechnology (2001) RFA Text | Recipients Lists
Research Category: Safer Chemicals , Nanotechnology
We plan to study the role of ion-induced nucleation as a mechanism for producing new nano-sized particles in the atmosphere. We hypothesize that (1) nucleation processes in different locations are driven by different gas phase species and can be homogeneous and/or ion-induced depending on time and locale, and (2) ion-induced nucleation events can be due to the growth of either positive or negative ions, and different gas phase species are responsible for bursts of intermediate and large positive and negative ions. It is our ultimate goal to develop experimentally verified models for the formation of ultrafine atmospheric particles by nucleation.
Our study will include both laboratory and field research and will involve the measurement of ion mobility spectra (nominal ion sizes 0.4 to 15 nm) and ion composition. Ion composition will be measured by tandem mass spectrometry and will include measurements of both positive and negative ion composition during nucleation events, which has not previously been done. We will develop a microphysical model to interpret our data. This model will attempt to reconcile observed time-dependent trends in ion mobility distributions and aerosol charge distributions.
Recent epidemiological research has suggested that, on a mass basis, ultrafine particles can be more harmful to human health than larger particles. Furthermore, ultrafine particles formed by nucleation can grow into cloud condensation nuclei that can impact on the earth's radiation balance. This project complements other ongoing research in our laboratories in which we are studying the homogeneous nucleation by reactions of neutral molecules in the atmosphere. The results of this study will be useful to modelers, who require experimentally-verified models of microphysical processes to evaluate aerosol climatic effects, human exposure, etc.