The effect of source area and atmospheric transport on mineral aerosol collected over the North Pacific Ocean

Aerosol samples collected on two North Pacific cruises were analyzed for rock-magnetic properties, grain size and < 2 mu m and 2-20 mu m mineralogy. These sedimentological results were compared with isentropic air mass trajectories in order to study the effects of source region and atmospheric transport on the mineral aerosol. The results indicate that there are differences in the aerosol composition and grain size for two broad source regions. Aerosols which originate from west of the Pacific an characterized by abundant, fine-grained aerosol, which has a high coercivity magnetic composition, and is relatively enriched in kaolinite. Aerosols originating from continents to the north and east of the Pacific basin are much less abundant, contain coarse-grained material with a low coercivity magnetic component, and the mineralogy is relatively enriched in plagioclase. Comparison of the mineral aerosol from Asia with atmospheric transport time indicated that the concentration of the mineral aerosol decreases with increasing transport time. The mineral aerosol is compositionally fractionated as it moves away from the continental source region, with a relative decrease in the primary minerals quartz and plalagioclase and an increase in the smectite, illite and chlorite concentration with increasing transport time. (C) 1998 Elsevier Science B.V. All rights reserved.