Abstract View
How Do Measurements of Single Particle Composition Constrain Gas-Particle Exchange?
DANIEL MURPHY, Karl D. Froyd, Charles Brock, Agnieszka Kupc, Gregory Schill, Christina Williamson, NOAA CSL
Abstract Number: 117
Working Group: Aerosols, Clouds and Climate
Abstract
We will used data from the Atmospheric Tomography (ATom) and earlier missions to show how measurements of single particle composition can offer insights into gas-particle exchange processes that are not available from bulk measurements. Primary and secondary sources can often be distinguished. If a low-volatility species such as sulfuric acid or organics is condensing onto pre-existing particles, it will generally be present on almost all particles. In contrast, a primary source of sulfate or organics will usually lead to a distinct population with different concentrations on different particles. We will show examples of these processes.
A second way single particle composition can constrain gas-particle exchange is by measuring the evolution of distinct types of particles in the same air. A good example is in the lower stratosphere, where stratospheric sulfuric acid particles with and without meteoric metals coexist with mixed organic-sulfate particles that originated in the troposphere. That these particles remain distinct has important implications for aerosol chemistry and the concentrations of several gas-phase species. Neither semi-volatile organics nor ammonia can be in equilibrium with the gas phase. The gas-phase concentrations of semi-volatile organics and ammonia must be very low, or else the sulfuric acid particles would not stay so pure. Yet the sulfuric acid particles in the Northern Hemisphere show a very small but measurable uptake of organics, indicating non-zero gas-phase concentrations of those species. Finally, the organic-sulfate particles must be resistant to photochemical loss, or else they would no longer retain their organic content.