Grantee Research Project Results
Surface Ion Mobility and Deliquescence of NaCl Particles
EPA Grant Number: FP916335Title: Surface Ion Mobility and Deliquescence of NaCl Particles
Investigators: King, Stephanie M.
Institution: Harvard University
EPA Project Officer: Lee, Sonja
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $106,688
RFA: STAR Graduate Fellowships (2004) RFA Text | Recipients Lists
Research Category: Fellowship - Atmospheric Sciences , Academic Fellowships , Air Quality and Air Toxics
Objective:
Recent laboratory and field studies have shown that heterogeneous reactions in aqueous surface layers of salt particles can significantly affect tropospheric chemistry. The kinetics and mechanisms of these reactions, however, are not fully understood, in part because of the dependence of surface reactivity on water vapor. In particular, surface reactivity on NaCl powders has been shown previously to increase with increasing relative humidity. Although adsorbed water provides a mechanism for increased ion mobility and reactivity, relatively little is known about the details. The objective of this research focuses on characterizing ion mobility on NaCl particles and its dependence on relative humidity.
Approach:
Time-resolved ion mobility measurements are made using a static mode of scanning polarization force microscopy (SPFM), which is a noncontact operation mode of atomic force microscopy that records the electrostatic (polarization) forces between a biased tip and sample surface. To determine ion mobility, the tip is held in place while a square wave voltage is applied at low frequency. The time evolution of the polarization force is recorded as solvable ions at the sample surface diffuse toward or away from the tip. The SPFM technique also will be used for noncontact imaging purposes to determine the deliquescence relative humidity of NaCl particles in the nanosize regime.
Supplemental Keywords:
fellowship, tropospheric chemistry, water vapor, salt particles, ion mobility, relative humidity, aqueous surface layer reactions,, Air, Scientific Discipline, Engineering, Chemistry, & Physics, Analytical Chemistry, Atmospheric Sciences, Ecology and Ecosystems, aerosol particles, salt particles, environmental monitoring, atmospheric particles, chemical composition, troposphere, humidity, surface ion mobilityProgress and Final Reports:
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.