CAPS: Research

Atmospheric Particulate Matter

The central focus of CAPS is the origin, influence, and fate of atmospheric particulates. Particulate matter is either emitted directly into the atmosphere or formed there as a result of the atmospheric oxidation of precursor species. Once formed, particles (or aerosols): play a pivotal role in cloud formation; they affect visibility and the overall radiative balance of the earth; they influence the chemical properties of droplets and thus the oxidation of various pollutants; they directly influence human health; and finally they react directy with minerals on the surface or disolve into surface waters, influencing their acidity. Aerosol emissions are studied directly by Prof. Robinson, while the chemistry leading to their formation in the atmosphere is a major focus in the groups of Prof. Donahue and and Prof. Pandis. Chemistry of the aerosols themselves is studied by Prof. Pandis and Prof. Davidson, while the global chemistry and influence on climate is the major focus of Prof. Adams. Finally the fate and deposition of particles is studied by Prof. Davidson.

A unifying subject within the research groups comprising \caps is the origin, behavior, and fate of organic particulate matter (OC). Reduced or partially oxidized compounds make up between 1/3 and 1/2 of the total mass of PM2.5 in many places -- this is the most complex, least understood, and in many ways most interesting fraction of the PM2.5 mass. One of the interesting aspects of these organic compounds is that they remain chemically active, often in both the condensed and vapor phase, and those chemical reactions can transform initially water-averse (hydrophobic) particles into water absorbing (hydrophilic) particles. The interaction of particles with water is critical to the role they play in the climate system, so this generates a tight coupling between particle chemistry and climate. The health consequences of this processing are almost completely unknown.