Airborne minerals and related aerosol particles: Effects on climate and the environment

Aerosol particles are ubiquitous in the troposphere and exert an important influence on global climate and the environment. They affect climate throug h scattering, transmission, and absorption of radiation as well as by actin g as nuclei for cloud formation. A significant fraction of the aerosol part icle burden consists of minerals, and most of the remainder-whether natural or anthropogenic-consists of materials that can be studied by the same met hods as are used for fine-grained minerals. Our emphasis is on the study an d character of the individual particles. Sulfate particles are the main coo ling agents among aerosols; we found that in the remote oceanic atmosphere a significant fraction is aggregated with soot, a material that can diminis h the cooling effect of sulfate. Our results suggest oxidization of SO2 may have occurred on soot surfaces, implying that even in the remote marine tr oposphere soot provided nuclei for heterogeneous sulfate formation. Sea sal t is the dominant aerosol species (by mass) above the oceans. In addition t o being important light scatterers and contributors to cloud condensation n uclei, sea-salt particles also provide large surface areas for heterogeneou s atmospheric reactions, Minerals comprise the dominant mass fraction of th e atmospheric aerosol burden. As all geologists know, they are a highly het erogeneous mixture. However, among atmospheric scientists they are commonly treated as a fairly uniform group, and one whose interaction with radiatio n is widely assumed to be unpredictable. Given their abundances, large tota l surface areas, and reactivities, their role in influencing climate will r equire increased attention as climate models are refined.